A short manual of forest management

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431

J34

LIBRARY

FACULTY OF FORESTRY
UNIVERSITY OF TORONTO

A SHORT MANUAL

OF

FOREST MANAGEMENT

CAMBRIDGE UNIVERSITY PRESS

C. F. CLAY, MANAGER
LONDON : FETTER LANE, E.G. 4

LONDON : WILLIAM WESLEY AND SON,

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NEW YORK : THE MACMILLAN CO.
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CALCUTTA [ MACMILLAN AND CO., LTD.
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TORONTO J THE MACMILLAN CO
OF CANADA, LTD.

TOKYO : MARUZEN-KABUSHIKI-KAISH

ALL RIGHTS RESERVED

A SHORT MANUAL

OF

FOREST MANAGEMENT

BY

H. JACKSON, M.A.,

SCHOOL OF FORESTRY,
UNIVERSITY OF CAMBRIDGE

CAMBRIDGE

AT THE UNIVERSITY PRESS

1921

50
431

J34-

PREFACE

THE object of the present manual is to present a brief and
simplified text-book on Forest Management, based on a purely
practical foundation. The standard works on this subject some-
times present — for the student, and especially for the public—
a rather formidable appearance, and contain an exposition of
high theory a part of which at the present time is seldom, if
ever, capable of practical application to the forest conditions of
our own country, or of our possessions in other parts of the
world. An attempt is made therefore to produce a simplified
practical review of this subject from which are eliminated all
reference to advanced theories which are not at present sus-
ceptible of practical application, and all other matters of purely
academic interest. Some confusion has resulted, it is thought,
in the past, from attempting to embrace in one study such
diverse conditions as obtain in the most intensively worked
continental forests which have been highly organised for genera-
tions, in the vast forests of India which are still generally in their
natural state of the utmost irregularity, and thirdly in the small
estate woodlands and plantations of our own country. An attempt
is therefore made now to discriminate between such different
types of forest with a view to elucidate and facilitate the pre-
paration of suitable working-plans for each type.

Use has been made of the following standard works on Forest
Management: Manual of Forestry, vol. in. Sir Wm. Schlich;
The Forester, J. Nisbet; The Practice of Forestry, P. T. Maw;
British Estate Forestry, A. C. Forbes; Forest Working Plans in
India, W. E. D'Arcy.

H. JACKSON.

Jan. 1921

CONTENTS

PAGE

DEFINITIONS . vii

CHAPTER I. INTRODUCTORY.

1. The basis of management i

2. Various objects of management .... i

3. Choice of species 2

4. Choice of silvicultural method 3

5. Choice of rotation 3

CHAPTER II. FIRST PRINCIPLES.

6. Time element in forestry. The wood-capital . . 5

7. The normal forest 7

8. Relation between wood-capital and increment . 8

CHAPTER III. MENSURATION AND INCREMENT.

9. The quarter-girth convention 10

10. Commercial method of estimating standing timber n

1 1 . True measure of standing timber . . . . 12

12. Weise's method of finding the average tree . . 15

13. Increment . 15

14. Increment of felled trees. Stem -analysis . . 16

15. Increment of standing trees 17

1 6. Pressler's formula 18

17. Schneider's formula 19

1 8. Breymann's formula 19

19. Increment of whole crops 20

20. Yield-tables 22

CHAPTER IV. FIELD WORK.

21. Preliminary examination of the area . 23

22. General description of crop . . . . 24

23. The block 24

24. The compartment 25

25. The sub-compartment 25

26. Description of compartments 26

27. Collection of statistical data 26

28. Formation of working-circles . . . . . 27

29. Formation of felling-series 27

viii CONTENTS

CHAPTER V. GENERAL PRINCIPLES OF PLAN.

PAGE

30. The three types of forest 29

31. General and special plan 30

32. Duration of plan 31

33. Degree of rigidity desirable 32

CHAPTER VI. METHODS OF TREATMENT.

34. Classification of methods 34

35. Simple coppice '34

36. Coppice-with-standards 35

37. Methods included in even-aged high-forest . . 38

38. The Uniform method 38

39. Clear-felling with natural regeneration . . . 41

40. Clear-felling with artificial re-stocking ... 42

41. Strip-felling 43

42. Group method . 43

43. The Selection method . 44

44. Provisional methods 48

45. Conversion from Coppice-with-standards to Uniform 49

46. Conversion from Selection to Uniform . . . 51

47. Improvement method 54

CHAPTER VII. CALCULATION OF THE POSSIBILITY.

48. Theory and practice 56

49. Regulation by area 56

50. Regulation by volume of growing stock . . . 57

51. Regulation by increment 57

52. Regulation by area and volume .... 58

53. French method 59

54. Calculation of yield under Selection method . . 60

CHAPTER VIII. THE WORKING-PLAN REPORT.

55. Form of report 63

56. Control Form and Forest Journal .... 65

CHAPTER IX. BRITISH ESTATE FORESTS.

57. Outline of plan of management . . . . 67

INDEX 69

DEFINITIONS

Block is a large natural subdivision of a forest, either formed by a
detached group of woodland, or else a section of a main forest area
determined by .its situation, with natural boundaries, and often with
a local name. It may be of any size and shape, and has nothing to
do with the method of treatment.

Periodic block is a subdivision of a felling-series under the Uniform
method: it contains a succession of age-classes generally extending
over about twenty or thirty years, set apart to be regenerated during
the corresponding period of the same duration. The whole felling-
series or working-circle is divided into as many periodic blocks as
the rotation is divided into periods.

Compartment is a permanent topographical subdivision of the
block and forms the unit of area. Its boundaries are natural, or are
formed by roads or lines.

Sub -compartment is an area in which the condition of the crop,
its composition and age, and the soil 'and situation, are sufficiently
homogeneous for each such unit of the crop to be capable of being
described in one statement.

Coupe is an annual felling-area under the provision of the working-
plan.

Normal forest is a forest which, in addition to being fully stocked,
and yielding the maximum possible production of wood per acre
per annum up to the limit imposed by the local conditions of soil
and climate, is constituted of a complete and regular succession of
age-classes, from one year old up to the age chosen as the rotation,
with each age-class occupying an equal area.

In other words, the normal growing stock results from a normal
succession of age-classes, with a normal increment. It is the ideal
state of perfection in forest organisation ; it is not absolute, but is
relative to a given rotation and a given silvicultural method of
treatment.

Constitution of a crop refers to the existence of a regular succession
of age-classes in it.

Composition of a crop refers to the species that compose it.

Exploitability is the condition of a tree or crop that has reached
the age or size at which it yields the kind of produce most useful to
its owner, under the declared object of management.

Possibility is the maximum quantity of material, which may, for
the time being, be annually removed from a forest, consistently with
such treatment as shall tend to bring the forest as near as possible to
the normal state, and with maintaining a constant yield.

x DEFINITIONS

Increment is the increase, due to growth, in the volume of material
of a tree or crop, in a given time.

Working-circle is an area of the forest worked under one and the
same method of treatment, with the same rotation, and the same set
of prescriptions under one and the same working-plan.

Felling-series is an area of forest forming an entire working-circle,
or else a section of a working-circle, containing a complete separate
series of age-classes, thereby forming a miniature forest, and a unit
of management complete in itself.

Cutting-series is a subdivision of a felling-series comprising a
number of age-gradations differing in age by a constant number of
years. The object is to break up the succession of coupes in order to
reduce the danger of injury from wind. Instead therefore of a single
succession of crops on the ground from one year old up to a hundred,
the first cutting-series would contain — if there were five of them—
crops aged i, 6, n, and so on up to 96, the second cutting-series
2, 7, 12... up to 97, and so on.

Felling-cycle is the time elapsing between two successive principal
fellings in the same area, worked by the Selection method.

Rotation is the time elapsing between the creation of a crop and
its removal; or in other words, the age at which the crop attains
exploit ability under the stated object of management.

Thinning is a cultural operation which consists in removing from
out of a growing tree crop the stems becoming superfluous, so that,
while realising these latter, each tree left standing may have sufficient
space to attain that state of development which is required for it to
satisfy the objects of management.

CHAPTER I. INTRODUCTORY.

i. The basis of management.

WOODS and forests, whether owned by private -landlords, or by
the State or other corporate bodies, must obviously be managed
in such a way as to carry out as far as possible the wishes of the
owner. The foundation of forest management therefore is the
object of management as stated, after due consideration, by the
owner of the forest. No one but the owner can decide authori-
tatively on the policy to be followed, and it is his duty and
privilege therefore to think the matter out carefully, and then
to define exactly what his object or objects is or are. Until this
is done the professional forester can do little or nothing to help
matters. In some cases, as in most State forests, the object of
management has been definitely and explicitly laid down; but
in others, notably in British estate woods, the object has never
been clearly thought out nor defined, and is often, there is reason
to fear, non-existent.

2. Various objects of management.

Speaking generally, these objects of management may be
classified as being either physical or economic. The former class
would apply generally to all forests of protection, such as forests
maintained on mountain slopes to prevent erosion, ravinement,
landslips or torrents, and to forests in the catchment areas of
rivers affording an important water supply; and to any forests
maintained for climatic reasons or other indirect effects. It
would also apply to private woodlands attached to estates in
Great Britain which are treated as amenity grounds for land-
scape or arboricultural purposes, and lastly also — at any rate
to some extent — to woodlands worked primarily as game pre-
serves. On the other hand, an economic object of management
would apply to all forests of supply — to all forests,, that is,
which are worked mainly with a view to a supply of timber or

J.F. I

2 INTRODUCTORY [CH.

other forest produce, which therefore form a commercial enter-
prise and occupy rent-yielding ground. In this case the owner
would wish to adopt a scheme of management such as would
primarily render his woodlands a financial success, yielding the
maximum soil rental and giving him the highest net return on
his invested capital.

In many cases it is of course possible to adopt a mixed object
— at any rate to some extent — and so to modify the strict
financial course in any given direction. Even game preserving
is not altogether incompatible with economic forestry, though
the fact that rabbits generally accompany pheasants makes it
difficult. So, too, in the case of State forests, it may be the duty
of the State to produce timber of the largest possible dimensions
for the benefit of the community at large, since private owners
cannot afford to work with such a long rotation, involving an
immense invested capital and a proportionately diminished rate
of interest. In this case the State would have to modify the
strictly financial rotation, and deliberately to extend it in order
to obtain the timber of large dimensions required by the general
public.

3. Choice of species.

The object of management having been carefully considered,
and definitely stated in precise terms, it is possible then to con-
sider how this object may be best attained with reference to
choice of species, choice of method of treatment, and choice of
size of maturity. With regard to choice of species, if we are
dealing with a large State forest of natural origin covering an
extensive area, there may be no question as to species, nor
possibility of making any direct alteration in this respect; but
if on the other hand we are dealing with small woodland areas
such as exist all over Great Britain, it may be quite possible to
make a change from coniferous to broad-leaved species, or vice
versa, or to substitute one species for another, if by doing so,
the objects of management, financial or economic, can be better
realised. It is of course always safer to retain a species which
is found growing naturally and healthily in its own habitat than
to introduce a new — or still more an exotic — species, of which

i] INTRODUCTORY 3

the future is necessarily uncertain and speculative. In any case
the species chosen must always be absolutely suited to the local
conditions of soil and climate in every respect. The advantages
and disadvantages of pure and mixed crops may be considered
at the same time, in relation to the silvicultural character and
light requirements of the species in question. In most cases the
nature of the soil and climate will indicate very plainly what
species is best suited to it, and no other tree should then usually
be considered.

4. Choice of silvicultural method.

Then as to silvicultural method. This will be controlled largely
by the species with which we are dealing, and also by the length
of rotation required to carry out the object of management; the
timber market too will have to be consulted, and the require-
ments of local industries taken into account. These considerations
will generally be sufficient to decide whether the system of high-
forest should be adopted or not. If it is, the silvicultural character
of the principal species and its light requirements will indicate
whether the even-aged condition or that of mixed ages will be
the more profitable. If natural regeneration by seed is practicable,
this will be one of the most important points to be considered.
In any case the choice of method must be based purely on silvi-
cultural grounds, and no considerations, economic or financial,
except in so far as they are in perfect harmony with the cultural
requirements of the species, and the maintenance and improve-
ment of the fertility of the soil, must be entertained for a

moment.

5. Choice of rotation.

Then, lastly, as to the length of rotation. From the definition
of the object of management it should be possible to deduce what
size of timber it is necessary to turn out in order to attain that
object. The timber market must be consulted, and the probable
future demand estimated. On the other hand all available data
as to the rate of growth of the species in question must be studied,
and its periodic increment in volume, quality, and price, up to
the age of its physical maturity. Such considerations will serve
to determine — at any rate to within a period of a few years more

I — 2

4 INTRODUCTORY [CH. r

or less — the age at which the desired size of tree may, under
local conditions of soil and climate, be realised.

A longer rotation generally means a more valuable yield, but,
on the- other hand, it also means a larger wood-capital, and
therefore a proportionately smaller rate of interest on the capital
involved.

For forests of protection therefore, as we have already seen,
as distinguished from forests of supply, a physical rotation
would be adopted, while for ordinary commercial forests, the
rotation corresponding to the maximum soil-rental expresses
the true economic value of the management, but this is an
exceedingly difficult matter to determine exactly. In the
case of State forests, where the object of management is the
production of timber of the largest possible dimensions, the
rotation may be longer than the true financial rotation, while in
the case of private forests worked for the production of small
wood or fuel, the rotation adopted may be in the neighbourhood
of the short rotation corresponding to the greatest production
of volume, at the age when the current and mean annual rates
of increment coincide. In any case cultural considerations have
to be taken into account as well as economic ones.

CHAPTER II. FIRST PRINCIPLES.

6. Time element in forestry. The wood-capital.

THE preliminary matters discussed in the foregoing chapter
having been settled, it now becomes necessary to consider the
manner in which a forest may best be made to operate as a
wood-producing and rent-yielding property, and to organise the
working in such a way as to make the enterprise as profitable
as possible.

The distinguishing characteristic of forestry is the time
element. Instead of harvesting the fruit as it becomes ripe year
by year, as is the case in agriculture, in forestry we may have
to keep our trees standing for 100, or even 200, years, before they
become mature. Then to ensure a proper condition of the ground,
to make it suitable for reproduction by seed, and to secure the
highest degree of productivity, it is necessary to maintain a more
or less close leaf-canopy over it for the space of one to two human
generations at least. It may be assumed that a yearly return is
required, unless the woodland estate is too small to make an
annual out-turn practicable. It may also be assumed that this
annual return should be constant, that is, sustained at approxi-
mately the same figure year by year.

If then we have, for example, an area of 100 acres of woodland,
worked on a loo-year rotation, we should be able to fell each
year one acre of forest of one hundred years of age, which would
give us our equal annual yield. But in order to do this in per-
petuity, it would obviously be necessary to maintain standing
the whole 100 acres stocked with a regular succession of crops,
each crop occupying exactly the same area of one acre, and
composed of ages forming an arithmetical series of i, 2, 3, 4 years,
and so on, up to 98, 99 and 100.

It is a requisite condition for the realisation of an equal annual
yield that there should be this complete succession of equal areas
of all age-classes, from one year old up to the age taken as the
age of maturity — one area for each year of age — always kept

6 FIRST PRINCIPLES [CH.

standing, and fully stocked, up to the standard imposed by the
local conditions of soil and climate.

Just before the loo-year-old acre of forest in the above
example is felled, this acre may be regarded as the interest on
the capital formed by the 99 acres of growing stock. Just as
money deposited in a bank produces annual interest, so does our
wood-capital standing in the forest. Instead, however, of har-
vesting each year the annual production of each acre of the
forest, we realise each year the accumulated production (e.g.) of
100 years on one-hundredth part of the whole area; and we can
only continue to do so permanently, if we maintain a complete
and unbroken succession of all age-classes, each occupying an
equal area, always standing and in active growth. See the
figure on page 9.

It is evident that the longer the rotation, the greater will be
the wood-capital or growing stock which it will be necessary to
maintain. If, for instance, in the above example we were to
make 200 years our rotation instead of 100, it is obvious that the
volume of our wood-capital would have to be doubled, although
the annual yield (200 years accumulated production over half
an acre) would be much the same as before.

In systematic forestry therefore, where a sustained annual
yield is desired, it is necessary to keep a very large volume of
timber, covering a large extent of land, and representing a large
amount of invested money, always standing on the ground. This
graduated series of age-classes over equal areas is of course an
artificial condition, and it may take as many years to constitute
this wood-capital as there are years in the chosen rotation. The
importance of the time element in forestry is thus easily felt, and
the necessity for continuity of management is at once seen.

Without this continuity of management no organised forestry
is possible, and that is one reason why working-plans have been
generally confined to forests belonging to the State or other
corporate bodies, in which some continuity is assured.

With private owners there is no assurance of continuity from
one generation to another, and therefore the necessary organised
growing stock is seldom, if ever, constituted, and systematic
working is hardly possible.

n] FIRST PRINCIPLES 7

Another point to be noted is that there is nothing but volun-
tary economic considerations by which to distinguish the wood-
interest from the wood-capital, because they are identical in
nature and are joined together. In the wood of any tree, the
year's accretion of new wood, and the older wood which pro-
duced this accretion, are exactly alike and form one piece of
wood. So, in the forest, there is nothing to distinguish how much
is capital and how much is interest, except self-imposed moral
considerations.

Consequently mistakes may be made which may take a life-
time to correct, and the wood-capital may be drawn upon for
many years without any appreciable loss being felt, but at least
as many years will have to be spent in re-accumulating the
capital stock which has been wrongfully dissipated.

From these considerations, it is seen that the time element,
and the largeness of the capital required to produce timber, and
the danger of unbalancing the systematic management by
liquidating a part of the capital, combine to render forestry
more suitable to corporate bodies, which have an interest in
continuity, than to private owners of limited means.

7. The normal forest.

In forest management the ideal condition is known as the
"normal" forest, and a forest is said to be "normal," when, in
addition to being constituted of a complete series of growths of
all ages from the seedling to the exploitable tree, each age-class
occupying an equal area, it is completely stocked, and the
growth is proportionate to the fertility of the soil. .

In other words, it is a forest formed of a regular succession
of equal areas of each age-class, from one year old up to the age
of the rotation adopted; it is fully stocked, and has no blanks,
no defects or deficiencies, and the production of wood annually
over every square foot of the area is the maximum quantity
possible under the local conditions of soil and climate. It is
the ideal state of perfection which is very seldom — if ever —
realised in practice. It will be noticed that this normal state
represents nothing absolute, but is merely relative to a given
method of treatment and a given rotation. A forest might be

8 FIRST PRINCIPLES [CH.

normal under one rotation and one method of treatment, but
it would at once become abnormal if either of these conditions
was changed, and the forest required to be re-constituted or
organised on a different pattern. Normal volume means the
totaL cubic contents of the whole growing stock of a normal
forest, which results from its being formed of a normal (that is,
complete and regular, with an equal area of each) succession of
age-classes, and from its having a normal increment, that is, a
maximum possible annual rate of production. It is of course
not necessary that the different age-classes should be arranged
contiguously in regular succession of age on the ground, nor is
it even necessary that each age-class should be contained on a
single area all of one holding, but the normal state may, and
always ought to, exist, even in an irregular forest, where trees
of all ages are mixed up anyhow, and growing one above another
all over the whole area, although in this case no separate
age-classes are visible. Unless this normal series of age-classes
exists — although invisible — the full equal yield cannot be realised
every year for ever.

8. Relation between wood-capital and increment.

To make this clear, let us take an example. Suppose that we
are working a forest on a twenty year rotation, and for that
purpose have divided the ground up into twenty equal areas.

We can represent our growing stock diagrammatically as in the
figure on page 9. The horizontal co-ordinate represents the area
divided into 20 equal parts, and the vertical co-ordinate re-
presents the volume of timber produced by the growth of the
forest year by year. We have then 20 crops of equal area forming
a regular succession of ages. The first area, on the left-hand side,
is i year old, the second 2 years old, the third 3 years old, and
so on up to the twentieth area which is 20 years old. The volume
of the growing stock or wood-capital is represented by the area
of the triangle ABC, and the yield, which is equal to the annual
increment over the whole area, is represented by the rectangle
AEFB, which is formed of 20 years' accumulated growth on
one-twentieth of the area, and is equal to the sum of the annual
increments (the portions shaded along the diagonal A C) for one

II]

FIRST PRINCIPLES

year over the whole twenty sub-divisions of the area. We can
now see the relation which necessarily exists between the incre-
ment and the growing stock. If the whole area were stocked
with growth of 20 years of age, the volume of the wood-capital
would be represented by the rectangle ABCD, so that our
present normal wood-capital, represented graphically by the
triangle ABC, is equal to one half the increment during the
whole rotation over the whole area, or, in other words, it is equal
to the average annual increment over the whole area during half
the number of 'years in the rotation.

Growth

E A

r

20 years

15 years

10 years

5 years

C Areas. F B

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

This essential relation may also be demonstrated in another
way. In our example the growing stock is composed of the sum
of an arithmetical series of crops of equal area aged I, 2, 3, etc.
years up to 20 years old. Then if the average annual increment,
or production of cubic feet of wood, over the whole area, be
indicated by /, and the rotation be indicated by r the wood-
capital is equal to - x (1+2+3 + ... +r)

I r.(r+i) T r

= - x = / x - approximately.

t t* £

The normal growing stock is therefore equal to half the accretion
taking place throughout the rotation over the whole area, the
other half furnishing the yield during this time.

CHAPTER III. MENSURATION AND INCREMENT.

9. The quarter-girth convention.

THE cubic contents of a log of wood are found by multiplying
the sectional area at the middle of the log, .which presumably
tapers, more or less evenly, from one end to the other, by its
length. In terms of the girth at the point where the sectional

£2
area is taken, this area equals - - .

4.7T

The volume in cubic feet therefore, if the girth is measured in
inches and the length in feet, will be

x length.

4 . TT 144
This will give the true volume.

For commercial purposes, however, the true contents are riot
calculated, but instead, the quarter-girth measure is employed.

/£\2

In this method the sectional area is taken ( -) , or, in other

\4/

words, 77 is taken as 4.
Therefore,

the quarter-girth volume_ 3-14159 _ 78-5 _ 113
the true volume 4 100 144 '

and the true volume can be obtained from the quarter-girth
measure by dividing by 113 instead of by 144.

Thus the ordinary Custom-house formula, by which import
duty is levied on foreign timber, is

MM x length

= true cubic feet.

whereas the ordinary commercial Hoppus measure, which is
per cent, of the real contents, is

2x length
144

CH. in] MENSURATION AND INCREMENT n

In each case g is measured in inches at the middle of the log,
and the length of the log, or the timber-height of the tree, is
measured in feet.

As regards felled timber there is no difficulty about making
the measurement. For the girth, a quarter-girth tape, or a string
is used, while for the length an ordinary tape is used, or else a rod
with feet marked on it. If the shape of the tree or log is in any
way irregular, it is measured off into different sections of regular
form, and each section is measured separately.

10. Commercial method of estimating standing timber.

With standing timber, there are two procedures to be con-
sidered; first the ordinary commercial method of calculation,
and secondly the method employed for purposes of forest
management, or for scientific investigations, in which the true
volume is required.

By the commercial method, the girth is taken at 4 or 5 feet
from the ground with a quarter-girth tape, which gives at once
the quarter-girth to the nearest quarter of an inch.

The next step is to make a deduction for bark, which in most
parts of the country is done by allowing one inch for every foot
of quarter-girth. Thus if a tree measures anything under 24 inches
of quarter-girth, but 18 inches or over, ij inches would be
deducted for bark. An oak of course has a thicker bark than
a beech, and an opportunity may offer of measuring what the
actual thickness of bark is in a tree of any given species and any
given size. The correct mathematical allowance is -39 of an inch
from the quarter-girth for every quarter of an inch of thickness
of bark. Ordinarily, however, the commercial rule of thumb of
J inch for every 6 inches of quarter-girth is followed.

The next step is to estimate the timber-height of the tree,
that is, the length of bole from the base of the trunk up to the
point at which the stem divides up into the main branches that
form the lower part of the crown. This estimate is made by eye,
without using any means of measuring the height. It requires
practice and experience to do it accurately, and it is desirable
always to stand at about the same distance from the tree when
judging the height fit to yield sawing timber. There is of course

12 MENSURATION AND INCREMENT [CH.

no objection to making use of a long measured pole which can
be held up against the trunk, to assist in estimating its height.
It only remains now to make a further deduction from the
quarter-girth under bark to allow for the taper of the stem.
What is wanted is the quarter-girth under bark at mid-timber-
height. Thus, suppose the timber-height is estimated at 50 feet,
and we have taken the quarter-girth at 5 feet from the ground;
we now have to estimate the deduction for taper to be made over
a length of 20 feet, which is the distance through which we have
to raise our point of girthing to arrive at the middle of the
timber-length. The deduction to correspond with 20 feet of
height would generally be about 3 inches, or something between
2 and 4 inches. Here again there may be an opportunity of
measuring some felled trees lying on the ground to ascertain
what degree of taper actually exists. It may vary very con-
siderably according to the local conditions of growth, and
especially with the density of the crop, and an error in estimating
this deduction will make a considerable difference to the cubic
contents.

Another point that requires to be fixed is — up to what size is
to be considered measurable timber? Anything above 6 inches
in diameter is usually considered as possible timber, or in the
case of coniferous trees in regions where pitwood is saleable,
the limit may be put at 3 inches diameter.

The quarter-girth under bark at mid-timber-height, and the
timber-height, being now arrived at by this process of estimation,
it is only necessary to turn up Hoppus's tables to ascertain the
corresponding volume in cubic feet.

ii. True measure of standing timber.

For purposes of forest management, and for scientific in-
vestigations, some more accurate means of ascertaining the true
cubic contents of standing timber than the foregoing method,
which relies too much on ocular estimates, must be employed.

In continental countries, where systematic forestry has been
practised for a long time, and where careful data and statistics
of all kinds have been recorded and accumulated for a long time,
form-factors and volume-tables have been arrived at, which are

in] MENSURATION AND INCREMENT 13

most useful for these purposes, and are available now for each
different species in each sort of locality, grown in each kind of
crop, age, and so on, and are based on the records of thousands
of measurements. In these tables, form-factors are given
separately for each species, with different factors corresponding
to differences in height.

Where such form-factors exist, and are reliable, it is only
necessary to know the diameter at breast-height (4 feet 3 inches
exactly), and the timber-height, measured by a dendrometer,
thus:
Contents in cubic feet

f (Diam. at B.H. in ins.)2 TT

= F.f x v- - x - x height,

144 4

which would be equivalent to

(Diam. in ins. at mid- timber-height)2 TT

— — x - x height,
144 4

or

(Girth at mid-timber-height in ins.)2 I

— £- x - - x timber height m feet.

144 4 . 7T

It is of course only in very uniform crops grown in fully
stocked, close-canopied high-forest that form-factors and volume-
tables, which generally refer to the height of the tree, could be
safely applied, and even then they would only give good results
when applied to a large number of trees.

However, for the present we must generally be content to do
without these convenient helps to investigations regarding the
volume of standing timber, and find some other means of
estimating the cubic contents of a standing crop. This is best
done by finding out the exact size of a sufficient number of
sample trees; and then to fell several trees of these sizes, and
cut them into small sections, and measure them carefully, timber
and branch-wood.

The usual procedure is as follows. An enumeration is made of
the trees forming the crop, which are then totalled up for each
size class — generally i-inch diameter-classes, or 3-inch girth-
classes — and the size-classes are grouped together so as to form
say from three to six groups of equal range: the basal area
corresponding to each size is taken from tables, and entered in

14 MENSURATION AND INCREMENT [CH.

a column against that class, so that by multiplying this basal
area by the number of trees in each size-class, and adding them
together, the aggregate basal area of each group is found.
Dividing this total by the number of trees in the group, the basal
area of the average tree of the group is found, and its corre-
sponding girth or diameter is taken from the tables. This gives
us the exact size of the sample trees which we now have to find
in the crop, and one or two sample trees as nearly as possible
of exactly this size are selected for each group, and felled and
cut up and carefully measured. This gives the cubic contents in
timber and in small wood of the average tree for each group.
This volume, multiplied by the proportion borne by the basal
area of the whole group to the basal area of the sample trees
felled and measured, gives the volume for each group in solid
cubic feet. These have only to be totalled to get the total volume
for the whole area enumerated. Columns can, if desired, be
added for height, age, and form-factor.

This procedure would not be practicable in a very mixed and
utterly irregular crop, as it assumes a certain degree of uni-
formity. If the crop were quite irregular in all respects, no
accurate estimate could be arrived at except by estimating the
volume of each tree separately.

If, on the other hand, the crop were practically even-aged and
quite uniform, it would not be necessary to make groups, but
one average tree for the whole crop could be taken. It will be
noticed in the method described that no account is taken of
height. If, however, the crop contains distinct height-classes,
these must be dealt with separately in the same way.

Lastly, it is to be noted that, apart from the question of girth
or diameter, care must be taken in selecting the sample tree, as
any tree of this size would not do. It must be a tree representing
in shape and development all the conditions of growth existing
in the crop, especially with respect to the result of the density
of the crop and the crowding together of the stems in their
growth. The average density of the crop is of course a matter
of first importance as determining the size, shape, and develop-
ment, of the representative sample tree.

If the woodland area dealt with is of small extent, a complete

in] MENSURATION AND INCREMENT 15

enumeration would be made over the whole area. If, on the other
hand, the forest is too large for a complete enumeration to be
practicable, the estimate of its volume may be made either by
linear/surveys or by sample plots. In either case at least 5 per
cent, of the area should be enumerated in order to obtain reliable
results; less in young and regular crops, and more in old and
irregular ones. Linear surveys are preferable to sample plots if the
crop is irregular, or the ground hilly. In such a case a gridiron of
lines of one or two chains in width should be taken right across
the map in parallel lines at right angles to the contour lines as far
as possible, or in both directions at right angles to one another.
If sample plots are chosen, small areas of not less than half an
acre in extent should be selected at various points in the forest
so as to give a correct representation of all varieties of soil,
situation, age, and condition of crops over the whole area.

12. Weise's method of finding the average tree.

Another method of finding the average tree in a fairly regular
crop with a close canopy is Weise's. An enumeration of all stems
on the area is made by i-inch diameter or 3-inch girth-classes,
and the number of stems is then totalled. A count-back of
40 per cent, of this total number of the trees is made beginning
from the largest size. The size-class into which this count-back
leads will contain the average stem of the whole crop. A few
sample trees of this size should then be selected, felled, cut up,
and measured.

13. Increment.

In order to ascertain what financial return is being obtained
from the capital invested in a forest, and in order to frame a
plan on business principles, it is necessary to know the increment
in volume, quality, and price that is taking place at any given
time.

For this purpose we have to find out the volume increment
per acre per annum that is accruing in a standing crop of trees.

There is the rare case in which we might happen to have
accurate measurements of the crop previously taken, with
which, after a known period of years, we could easily ascertain

16 MENSURATION AND INCREMENT [CH.

the past rate of growth by comparing its present volume with
its recorded volume in the past, but it is of course most unlik-
that such past measurements will often be available. It will
therefore be necessary generally to estimate the volume incre-
ment of the standing crop by means of the ascertained volume
increment of an average sample tree, which, growing in a ful"
stocked close-canopied crop, may be taken as representative of
the entire crop.

It is obvious that our sample tree must represent all the
general conditions of growth which govern the individual stems
forming the crop, with a given degree of density, and growing
in close cover, because a tree growing in a free and isolated
position with an unrestricted amount of growing space in which
to spread itself, will develop in a very different way from a stem
grown in close cover. Then we have to remember that the
determination of the past rate of increment, although — unlike
the estimation of future increment, which is necessarily more or
less speculative, — it rests on actual existing data, is complicated
by the fact that a certain number of stems disappear out of the
crop year by year, or are removed by thinnings, and that the
stems remaining give us practically no information on this point.

The first thing to be done in any case is to consider the best
means of ascertaining the rate of volume increment of a sample
tree, which depends on its rate of growth in height, its form
factor, and its rate of growth in basal area, which in turr
proportional to the square of its girth, diameter or radius. This
volume increment may be expressed either in cubic feet, or ».
as a percentage. With reference to the volume of the wood-
capital producing it, the increment of a whole crop is stated as
so much per acre per annum.

14. Increment of felled trees. Stern-analysis.

In the case of felled trees, or of a sample tree which can be
felled and cut up in order to measure its past-rate of growth in
height and in radius, the rate of growth is ascertained by
counting and measuring the annual rin.

The most complete investigation of this kind is effected by
making what is called a stem-analysis, which is a rather intricate

in] MENSURATION AND INCREMENT 17

method of representing graphically the whole life-history of the
tree's growth in height, radius, and volume. It is only used for
purposes of scientific investigation.

In order to make a stem-analysis, the tree is cut up into a
number of sections of, say, 10 feet in length ; each section is then
sawn across the middle, and the number of concentric rings
exposed at each cross-section is successively counted and re-
corded.

From this record a table is prepared showing the number of
years that it took the tree to grow to the height of 5, 15, 25, etc.,
feet, up to its present total height. These results are plotted in
such a way as to represent graphically a longitudinal section of
the tree. A vertical line represents the axis of the tree, with the
heights of the successive cross-sections marked on it, and also
the heights which the tree had reached at successive periods of
its life.

Then at each cross-section the total number of annual rings
is counted, and each ten years' growth in radius, working back-
wards towards the centre of the tree, is accurately measured in
inches to two places of decimals, and a table is made of these
measurements at each cross-section. These radii corresponding
to successive ages are then plotted on a series of horizontal axes
corresponding to the successive heights of the various cross-
sections up to the top of the tree, and the points thus obtained
are connected by lines which represent the stem curves during
the life of the tree. A calculation can now be made of the volume
of the tree at each decennial period, and a series of tables is
prepared, giving the volume of each section at each age.

The periodic increment in cubic feet for every ten years is
thus known, and a curve can be plotted, with cubic feet repre-
sented by the vertical axis, and age by the horizontal axis,
showing the volume all through the life-time of the tree.

15. Increment of standing trees.

In the case in which the cubic contents of a certain tree-crop
had been accurately measured n years ago, and were found to
be v, while the present volume of the same crop is now V, the

V — v
average annual increment will be , and the mean volume of

n

J. F. 2

iS MENSURATION AND INCREMENT [CH.

V+v
the crop in the middle of the period of n years will be

mt

V — v V + v
If p is the percentage rate of increment, p : 100 : : -

rl 2

V — v 2 200 V — v ..

therefore p = 100 x -- x ^— - x = -- . Now if — as in

n V+v . n V+v

practice is most probable — the crop we are investigating is
a middle-aged one, and if the two periods are not separated
by a great number of years, say more than ten years, in
that case the height and the form-factor of the average sample
tree will remain unchanged throughout the entire period of
measurement, and the volumes will then be proportionate to
the basal areas of the average sample tree of the crop, and the
formula will take the form of

200 D2-d*

n

As the difference between the two diameters will be small,
D2 + d2 will be approximately the same as J (D + d)2, and so
the formula can be simplified to the form

_ 200 D — d
P" ~^TXDTd'

1 6. Pressler's formula.

This formula of Pressler's is a very useful one, and may be relied
upon to give good results, provided that the crop be of middle
age, say, of at least sixty years old, and that n represents a small
number of years so that D and d do not differ greatly.

In the case of standing timber, the radial increment of the
tree is readily ascertained by means of Pressler's borer. This is
a tool like a hollow gimlet, which is screwed into the sample tree
in a radial direction at right angles to the axis of the tree, and
which thereby extracts a round spill of wood about 2 inches in
length from the tree. To insure accuracy two, if not four, borings
at right angles to one another should be made at the same level
on each tree; the annual rings on the spills of wood extracted
will be carefully counted and measured, and the mean taken.

in] MENSURATION AND INCREMENT 19

17. Schneider's formula.

Another very useful formula is Schneider's. Suppose that D
is the mean diameter of the sample tree at breast-height, and
that n is the number of annual rings in the last inch of radius,
and let us suppose also that the diameter D lies, not outside,
but in the middle of the i-inch zone of increment resulting from
the n years' growth. The area of this zone of increment is

and the annual increment of this basal area will be — - —

n '

then, assuming that the increment takes place half inside and
half outside the present diameter,

TT.D 7T.D2

n
400

p : 100 : :

and p =

n .D

Schneider's iormula gives practically the same result as
Pressler's, for if in the latter n be taken as i year, the D — d =
twice the breadth of the last ring, and D + d = twice the present
diameter, so

breadth of the last ring

Yj — .4.OO X

breadth of the present diameter '
which is the same result as is given by Schneider's formula.

1 8. Breymann's formula.

A third formula of the same kind which is often useful for
purposes of investigation of increment is Breymann's. In this,
the width of the last annual increase of the diameter d is repre-
sented by a, so that -- represents the last annual increase of

radius, and here again we will suppose that the diameter d lies
in the middle of this zone of increment. The superficial area of
the last annual zone of increment is

7T ( / d\ f -. d\ } 7T d

-x-nd-h- — [a- -} V =-. 2 . a .d = ir.d x -
4 i\ r 2/ \ 2/ J 4 2

then p : 100 ::v.d.-

2

and p = 200x5

a

7T

2 4

a

2 — 2

20 MENSURATION AND INCREMENT [CH.

This formula gives the current annual percentage increment of
basal- area at breast-height (and also in cubic contents of the

tree) as equal to 200 x -5 , while the diametral increment of any
stem is found in the proportion of

p : 100 : : a : d, or p = 100 x -,

a

Comparing these two results it becomes evident that the
percentage increment in basal area of the stem, and in the cubic
contents of the tree, is always twice as great as the percentage
of increment in diameter.

Schneider and Breymann's formula only give the current
annual percentage of increase during the year of investigation,
while Pressler's gives it for a short period of, say, ten years,
either past, present, or future.

All three formulae rest on breast-height diameter of standing
timber, and assume that height and form-factor remain the same
for both periods. Therefore, to ensure accuracy, it is better,
when practicable, to fell a few average sample trees, and then
to cross-cut them at mid-height, measure the annual rings at
the mid-section, and then calculate the current percentage
increment by Schneider's formula. In cases of appreciable
height growth, the formulae for breast-high diameter should
be enhanced by a small percentage of up to 25 per cent.

19. Increment of whole crops.

We have already seen that the past increment of a wood
cannot accurately be deduced from the results of an investiga-
tion into the rate of growth of single trees, as many stems will
have disappeared or been removed in the thinnings. The past
increment of middle-aged and older woods will therefore be less
than that of the single average tree.

This difficulty, however, does not present itself so much in the
case of the present and future increments, especially when we
only estimate such increment for a short term of years for practi-
cal purposes of management, and in such cases it is safe to assume
that for the next ten years the increment of the crop will be
about the same as during the last similar period.

, / volume\ , .

per acre with the m ean annual increment = — - during

\ age /

in] MENSURATION AND INCREMENT 21

For a whole wood, the present annual increment may be

mean annual increment
roughly obtained by the formula p = 100 x -

present cubic contents

when the mean annual increment is found by dividing the present
volume of the growing stock by its age, and this method would
give fair results in the case of a middle-aged crop that has just
passed its maximum mean annual increment. If the volume of
the crop has been calculated by forming groups of diameter-
classes, the mean percentage of increment should be estimated
for each group from sample trees of that group, and then the
current annual increment in cubic feet will be estimated for
each size-class, and the sum of them added together will give
the increment of the whole crop.

A comparison of the course of the current annual increment

volumeX
age /

the life-time of a crop will always yield information useful for
purposes of forest management. Curves to indxate the current
and mean increments may be plotted, with a horizontal co-
ordinate for age, and a vertical co-ordinate to represent cubic
feet of increment year by year. These increment curves must not
be confused with volume curves. The current increment rises
rapidly at first, and reaches its maximum towards the end of
the pole stage, when the height-growth culminates; earlier on
good soils, and with light-demanding species. It then falls
gradually. The mean annual increment rises more slowly, and
reaches its maximum often about thirty or forty years later,
and it is at its maximum when it is equal to the current annual
increment. It is at this period that the production of volume
per acre per annum is at its maximum. Later on the mean
increment gradually decreases, but much less rapidly than the
current increment.

A single tree growing in a free open position would have a
higher increment than an average tree grown in a close crop,
but the fully-stocked wood would have a larger increment per
acre than the open wood, because the number of stems is so
much greater, although the crowding diminishes the growth in
diameter.

22 MENSURATION AND INCREMENT [CH. in

20. Yield-tables.

Lastly, for fully-stocked crops that may be considered as
fairly normal, the increment past, present and future, may be
obtained from average yield-tables, in countries where such
yield- tables exist.

Yield-tables are constructed by measuring a very large number
of woods of all different ages, normal sample plots fully stocked,
of all species and qualities, and then plotting the volumes thus
obtained by means of co-ordinates indicating cubic feet verti-
cally and age horizontally. The outside points, that is, the
highest and lowest volumes recorded, are connected severally by
two curves, and the intermediate space is divided into three or
four equal strips through the middle of which a line is drawn
to represent the mean volume curve for each of the three or four
quality classes.

A tabular statement of this kind for each species shows the
course of development of a wood throughout its life-time, under
each quality of soil and climate, and under each method of
treatment, and affords average statistics for each unit of area,
at every age, as to the number of trees, their mean height,
diameter, volume, increment and form-factor. Such yield-tables
which afford information which is indispensable for a full and
proper knowledge of all the economic and financial questions
which have to be dealt with in forest management, may be
either general or local.

CHAPTER IV. FIELD WORK.

21. Preliminary examination of the area.

THE object of the field work to be carried out in connection with
the preparation of a working-plan is to examine the forest and
make a classified inventory of the crops, and to investigate the
local conditions of growth, in order to collect data on which to
base prescriptions for the future organisation and management
of the area. The results of these investigations will then be in-
corporated into a detailed statistical report which will form the
first part of the working-plan report.

The first step will be to make a preliminary reconnaissance of
the whole area, and then to proceed to the collection of statistical
details with regard to the topography, the configuration of the
ground, the soil, and climate, including a report on the existing
boundaries, and on the present system of roads, rides, etc.
A review will then be made of any local requirements or agri-
cultural customs likely to influence the management of the
forest, and of any existing rights of any kind with which the
forest area is burdened.

With regard to the soil, the physical and chemical characters
both of soil and subsoil will have to be described, with the
average depth, porosity, humidity, and the existence and
quantity of vegetable matter in the surface soil, and the nature
of the vegetable covering. Then, with regard to climate, parti-
culars are required in connection both with the general and the
local climate. The relative elevation of parts of the ground over
the surrounding areas will have to be stated as well as the
absolute altitude above sea-level.

The aspects have to be noted, and the average annual rainfall,,
the general state of humidity of soil and atmosphere, the force
and direction of the prevailing winds, the occurrence of frosts
in and out of season, and any other climatic influences. From
the above information, taken in conjunction with indications

24 FIELD WORK [CH.

afforded by the growth of the crops, especially in the matter of
height-growth, it will then be possible to determine a site quality
for each component part of the area.

22. General description of crop.

It will now be possible to proceed to a general description of
the forest crop. The distribution and area of the different types
of growth, and their suitability to the local conditions of soil
and climate. The composition of the crops, the principal species
and their relative proportions; their size and rate of growth,
reproduction, and general conditions of vegetation. Then the
Constitution of the forest crop, that is, the relative proportions
of the various size or age-classes. Any deficiency or irregularity
in the succession of these classes should be noted, and, if possible,
explained. The origin and past history of the forest crop should
be stated, as well as the general density of stocking. Blanks and
areas out of production should be noted, and lastly the effects
of climatic influences such as altitude, wind, drought, frost, and
the danger of injuries from insects and other pests, fire, etc.
should be described.

At this stage it may be possible to note at once some obvious
improvements that might be made in the selection of species,
or in the choice of silvicultural method, in order to carry out
the declared objects of management under the local conditions
of soil and climate that have just been investigated.

23. The block.

The next subject to which attention has to be paid is the
division of the forest into subdivisions. These may be either
purely topographical, and therefore more or less natural and
permanent, or they may be artificial, and dependant on the
organisation of the area with a view to its working under a
definite plan. Some existing subdivisions of the area will have
been already made use of for the purpose of describing the soil,
climate and crops, as indicated in the foregoing paragraphs. The
topographical and permanent subdivisions of a forest are the
block and the compartment. The block is a large natural sub-
division of a forest, formed either of a detached and self-contained

iv] FIELD WORK 25

group of woodland, or else of a section of the main forest area,
in which case it may often consist of one drainage basin and be
bounded by a watershed. In any case, the block has natural
boundaries such as watersheds, rivers, or roads, and it is often
distinguished by a local name. It may be of any size and shape,
and has no connection with the system adopted for working the
forest.

24. The compartment.

The compartment is a subdivision of the block and forms the
permanent unit of area. In a British woodland a compartment
may be 10 acres in extent, and in a forest in Burma it may be
1000 acres. It depends on the size of the forest and the intensity
of working. Its shape should be compact and more or less rect-
angular. Its boundaries will be formed by natural features of
the ground, or by roads, rides, fire-lines, rivers, ridges, or, if
necessary, by artificial lines.

25. The sub-compartment.

So far we have considered the compartment merely as a unit
of area, but we also have to find a unit of the crop which has
to be analysed and split up into silvicultural units. These will
therefore have to consist of subdivisions of the forest in which
the condition of the crop, its composition and age, and the soil
and situation, are sufficiently homogeneous for each of them to
be described as one unit of the crop. Now if the compartments
are small and are formed by the regular intersection of a network
of roads and lines, it is quite possible that the compartments
already formed in this way will also serve effectively as silvi-
cultural units for the purpose of affording a descriptive inventory
of the crop. It will, however, often be necessary to subdivide
our topographical compartments, because there will be found
notable variations in soil, or situation, or in the species, age or
condition of the crop. These subdivisions will be called sub-
compartments. They are not necessarily permanent, because
they are based on the nature of the crop standing on them at
the present time. The whole forest is thus split up into silvi-
cultural units, of no fixed size, but each containing a timber-crop
capable of being included in, and covered by, one description.

26 FIELD WORK [CH.

This description of compartments and sub-compartments often
forms- the bulkiest part of the whole working-plan report,
in which it is usually given as an Appendix. Its bulk, however,
will never exceed its importance, as it forms the foundation for
the whole enterprise, and will be found very valuable for future
reference.

26. Description of compartments.

This description of compartments will be drawn up in tabular
form, but will be written in narrative form under each heading.
The headings will be area, soil and situation, description of the
growing stock, and a column for remarks. Under description
of the growing stock, the composition, age, and condition of the
crop, will be given and an analysis and estimate of its contents.
The site quality, and the density may be also given. Under
remarks, notes will be made of any outstanding feature of each
crop, of any cultural operations that seem to be called for, and
suggestions regarding future treatment. There will of course be
considerable variations in the scope of these descriptions,
according to the extent of the area, the intensity of management,
the method of treatment, and the nature of the crop.

27. Collection of statistical data.

In order to collect all the information required for this detailed
description of sub-compartments it will be necessary to go all
over the ground very carefully, and to note all differences
occurring from point to point in the local conditions influencing
the growth of the crop, such as soil and aspect. It will be neces-
sary now to make careful note especially of the height-growth
as indicative of the quality of the soil, of the conditions con-
. trolling regeneration, and of the cultural requirements of the
different species, of which the relative proportions will also be
recorded. The predominant age of each crop, the existence of
over-mature stock, and the relative proportions of each com-
ponent age-class should also be noted, together with the density
of stock in each part.

In producing a working-plan it is the duty of the writer to
set forth and bring up to date all statistical data regarding the

iv] FIELD WORK 27

local conditions of growth. Probably there will be a certain
amount of information already recorded, and there may be
sample plots for the periodical measurement of girth-growth of
numbered sample trees already established. During the present
detailed examination of the growing stock there should be a
valuable amount of statistical figures obtained, such as careful
measurements of the cubic contents of sample trees, ring
countings, borings with Pressler's borer, and calculations of
current and mean annual increment. All these investigations
should be worked out and the results tabulated, and incorporated
as appendices in the plan under preparation.

28. Formation of working-circles.

We now have to consider the subdivision of the area in relation
to its organisation for the purpose of systematic working under
a definite plan. A working-plan may be prepared for an estate
or district containing woodland areas of diverse kinds, as for
instance coniferous woods worked as high-forest, and broad-
leaved woods worked as coppice-with-standards, requiring al-
together different treatment. The first step to be taken then is
to divide the area up into working-circles, each of which will
be composed of an area of forest worked under one and the same
method of treatment, with the same rotation, and the same set
of rules, under the provisions of one working-plan.

29. Formation of felling-series.

The boundaries of the different working-circles having been
determined, it may be found that for working purposes the
areas so defined are inconveniently large. Instead therefore of
working the whole area under one set of fellings, it may be
advantageous from several points of view to divide the working-
circle up into felling-series, each of which will be a unit area of
working. The advantages of this arrangement are, better pro-
tection against wind and insects, increased facilities for the
distribution of the produce to different centres of consumption,
distribution of work among establishments, and improved con-
ditions with regard to supervision and transport. The subdivision
of the working-circle into felling-series makes no difference to

28 FIELD WORK [CH. iv

the plan; it merely means that, for example, instead of felling
every year one compact area of 500 acres, we are going to fell
every year five different areas of 100 acres, each located in a
different part of the forest. Each felling-series will be a complete
and self-contained miniature of the whole working-circle, and
should contain therefore as nearly as possible an equal area of
every age-class. The number of series determined on will fix
the size of the annual felling area in each series, and this number
will be chosen, after due consideration of the questions above
indicated, namely protection against wind or insects, distribution
of produce in different directions, export and supervision, so as
to produce manageable coupes of the most convenient size.

CHAPTER V. GENERAL PRINCIPLES OF PLAN.

30. The three types of forest.

BEFORE proceeding to consider the measures necessary for the
detailed organisation of a forest under any definite method of
treatment, it may assist a clearer understanding of the matters
under discussion, from a practical point of view, if we now make
some discrimination between the different stages of forest
organisation that we may have to deal with, and distinguish
two or three types of forest for which a working-plan may have
to be prepared.

First of all then we have the rare case of the second or later
rotation of a completely constituted forest, which has already
been under intensive management for a long time, and which is
as nearly normal (in the strict sense of the word, which should
never be used in any other sense) as possible in every respect,
so that the sustained yield is equal to the full normal increment.
Such a forest could only be found in continental Europe, where
intensive management has been carried out for several genera-
tions, and where financial and actuarial methods have been
applied in great detail. This type of forest is the only one in
which the normal idea comes within the immediate range of
practical politics, in which valuations based on the maximum
expectation value of the soil are possible, and in which yield-
tables, increment-tables, and form-factors, are fully available.
It is safe to say that no such forest exists in Britain or in any
British possession at the present time.

Secondly we have the more common type of a forest fairly
well stocked, and containing some faint resemblance to a succes-
sion of age-classes, but incomplete, and not regularly constituted,
having not yet gone through a complete rotation under the
present scheme of management, or perhaps now undergoing con-
version from irregular to even-aged high-forest. During the
first rotation (or, in the case of a selection forest, the first
few felling-cycles) the building up of a complete and properly

30 GENERAL PRINCIPLES OF PLAN .[CH.

constituted growing stock is the principal thing aimed at, and
regular working and full production will not be possible till
after the end of the first rotation at the earliest. Meanwhile the
yield will be based — not on any abstract theories as to normal
increment — but on an estimate of the volume of standing old
stock that has to be cleared off the ground period by period.

Lastly we have the case of our English woodland estates, where
in most instances there is no assured continuity of management,
and no very definite or stable object of management. A working-
plan here will hardly touch the theories of forest management,
but will rather be a common-sense plan of operations, with a
progressive annual programme for the clearing and re-stocking
of successive portions of the ground as rapidly as possible, so
arranged that the receipts from clearings may cover the annual
expenditure in re-planting.

31. General and special plan.

Whatever method of silvicultural treatment is to be adopted,
the main provisions of the working-plan will take the form of
a general working scjieme followed by a special plan.

The general scheme will apply to the whole rotation, which,
in high-forest, may be 100 or 200 years, and will embrace in
outline the whole cycle of operations extending over that
time.

The special plan will refer to a period generally of between
ten and thirty years, and all the detailed prescriptions of the
plan will remain in force only for this period. In the case of
even-aged high-forest, one period, that is usually about twenty
or thirty years, will be taken as the duration of the prescriptions
of the plan; and the same period would be taken in the case of
a plan of conversion to even-age high-forest. In high-forest of
mixed ages, the period chosen for the duration of the special
plan would be one felling-cycle, or, if the felling-cycle were very
short — of not more than ten years, for instance — two felling-
cycles might be taken. In the case of coppice the general working
scheme and the special plan would practically coincide, and
the duration of the plan would be for one rotation of the
coppice.

v] GENERAL PRINCIPLES OF PLAN 31

While the general working scheme gives the framework of the
whole proposition, the special plan gives full details regarding
everything that has to be carried out in the forest during this
first period of twenty or thirty years, during which time all its
prescriptions remain in force. This includes a felling table
showing exactly what area is to be felled each year, and the
order of the annual coupes, if they exist; the nature of the
fellings, and a set of cultural rules to guide the operator who
carries them out; and lastly the material to be removed. This
special plan therefore contains the gist of the whole document.

32. Duration of plan.

Now to attempt to make any detailed forecast as to the future
condition of a forest after the lapse of a century or two, that is
to say any forecast that can be put into figures — either as regards
cubic contents or money value — is futile and misleading: if we
are wise, we shall avoid mathematics based on unknown future
conditions, and be content with a hope that, when that remote
time arrives, the forest will be to some extent improved as the
result of the wisdom of our present intervention. All calculations
of every kind should be limited to the period of twenty or
thirty years which has been adopted as the duration of the
prescriptions of the plan. No attempt should be made to extend
any hard-and-fast regulations for a longer future period, nor
should any regulation of the yield be imposed as a binding pre-
scription for more than twenty, or, at the outside, thirty, years.

It will in fact be found to be a wise course to follow if it is
always provided that the calculations on which the regulation
of the yield is based be revised every ten years, and that the
working-plan itself be revised at the end of each period of twenty
or thirty years, as the case may be.

Thirty years seems a short part of the life of a high-forest
timber crop, but it is a man's whole working lifetime, and some
progress should be made, and some improvements found avail-
able for introduction in the plan at the end of this period of
inception.

32 GENERAL PRINCIPLES OF PLAN [CH.

33. Degree of rigidity desirable.

There is one point of general application that may be noted
here, and that is that a fair margin of detail should always be
left to the discretion of the local forester who has to carry out
the prescriptions of the plan, and who may be assumed to be
a fairly competent person.

Cultural considerations should always be recognised as para-
mount, and must take priority over all rules. This is an important
principle, which must never be overlooked. For example, the
cultural requirements of a timber crop must never be sacrificed
for any paper calculations to regulate the yield, and no tree
should ever be felled — notwithstanding any working-plan rule—
if it is desirable for cultural reasons (such as shelter, or the
production of seed, etc.) to keep it standing.

The local forester is in the best position to appreciate these
cultural necessities, and therefore the prescriptions of the
working-plan should never be so detailed, and so rigid, as to
allow the local operator no discretionary power at all. Therefore,
while the general organisation of the forest and the annual plan
of operations are clearly and definitely laid down in the plan,
cultural details should be indicated in such a way that the
forester in charge will be at liberty to use his own judgment in
carrying them out.

The terms employed in framing the prescriptions of the plan
should, however, be precise and imperative. Suggestions and
recommendations are generally out of place in a plan, because
what is required are binding orders. "At such a place, at such
a time, such and such an operation will be carried out." Then
no evasion, or deviation from the plan, is possible without special
permission from competent authority. The working of the forest
should be rigidly prescribed in explicit and uncompromising
terms, while at the same time a fair margin of detail should be
left to the discretion of the local forester. For example, suppose
that, in prescribing the number of standards per acre to be
reserved in a coppice, it is found that forty-five would be the
best number to keep, in such a case the rule would be worded as
follows: "Between forty and fifty standards will be reserved
per acre." The framer of the rules should remember to look at

v] GENERAL PRINCIPLES OF PLAN 33

them from the point of view of the local operator who will have
to carry them out: the rules should be reasonable and easy to
apply, without being weak or ambiguous. Conditional or
facultative prescriptions may be employed in special cases to
meet doubtful contingencies, but such should be clearly stated.
The conduct of all essentially cultural operations, as for example
the successive regeneration fellings in even-aged high-forest,
must always be left to the local forester.

J.F.

CHAPTER VI. METHODS OF TREATMENT.

34. Classification of methods.

THE methods of treatment that we now have to consider may
be roughly classified as follows :

'Permanent /' [Simple coppice

Coppice system •{

(Coppice-with-standards

TT- u t (Even-aged

High-forest system i,,.
V (Mixed ages

(Conversions
^Provisional (Improvement.

35. Simple coppice.

In simple coppice the working-plan is of the simplest descrip-
tion, and consists in dividing the area of the working-circle, or
of a felling-series forming a subdivision of the working-circle,
into as many equal or equiproductive areas as there are years in
the coppice rotation. One annual area is then cut each year in
rotation. The number of years chosen as rotation depends on the
size of produce required, and on silvicultural considerations.
A few simple rules for the fellings will generally be drawn up
in order to prescribe the manner of cutting the underwood and
the season of cutting it. The rotation being short, generally
between ten and twenty years, there will be no need as a rule
for tending operations, but -if, for instance, a cleaning at mid-
rotation is thought desirable, in order to protect any seedling
plants that may appear on the ground or for any other purpose,
a prescription to this effect will be inserted.

The yield being determined by area, there will be no need to
estimate the possibility in volume. During the first rotation
there will probably be some irregularities to be faced. Some
coupes may have to be felled when they are a few years older or
younger than the proper age, but the main thing is to establish

CH. vi] METHODS OF TREATMENT 35

a regular succession of graded ages year by year, with equal areas
of each, for the second and subsequent rotations. To obtain
equal areas of all ages it might, for example, be wise to fell an
area in the first year and then again a second time in the last
year of the first rotation. In any case the areas must be classified
by age, and a felling- table then made out so as to deal with them
in such a way that at the end of the first rotation there will be
left standing on the ground a complete series of all ages occupying
equal areas. The actual out-turn year by year during the first
rotation is not of first importance, and equality of yield for these
first few years must be sacrificed to obtain the future regular
constitution of the series.

36. Coppice-with-standards.

In the case of coppice-with-standards, the general arrange-
ment will be the same as with simple coppice, and the size of
the annual coupe will be found by dividing the area of the
working-circle, or felling-series, by the number of years in the
rotation, which in this case will often be about ten years longer
than in simple coppice.

This rotation will have to be carefully considered from the
point of view of the objects of management, of the size and
quality of the produce required, and of the cultural character
of the species concerned, in given conditions of soil and climate,
with reference to both underwood and standards, since these
latter too will be materially affected by the length of the coppice
rotation, of which their ages will be a multiple.

In addition, the working-plan must regulate the selection and
reservation of the standards. Here we must go back to the object
of management as regards the reservation of standards, before
we can decide anything as to the number and kind of trees to
be reserved. Generally speaking, the object will either be a
cultural one, such as the protection of the underwood
against frost, or else an economic one, such as the production
of timber of fair size. These two cases must be considered separ-
ately. In either case we propose to grow two kinds of crop on
the same ground, while the available amount of soil and sunshine
is strictly limited. The more standards we keep standing, the

3—2

36 METHODS OF TREATMENT [CH.

less coppice production per unit of area will be obtainable ; so that
the two things have to be weighed, the one against the other.

Now if the main object of the reservation of the standards be
to protect the underwood from exposure and to supply seed, and
the underwood is to be looked upon as the more important of
the two kinds of crop, then the number of standards should be
fixed so as just to effect these cultural objects, and should be
kept at a minimum. The number should be no greater than what
would ordinarily be sufficient for these purposes. But if on the
other hand the object of maintaining an overwood is to produce
timber, then in this case the value and importance of the
standards will far outweigh that of the underwood, and the
interest of the owner will demand the largest number of standards
possible, without impairing the vigour of the coppice, which
will still be the main agent of the perpetuation of the forest.
These principles will be sufficient to enable us to decide on the
best number of standards to keep. The upper limit, that is, the
maximum possible number of standards, is fixed by the fact that
if the overwood forms close canopy, the underwood will languish
and tend to disappear. The rule therefore is that the standards
must never be so numerous that each tree is not in a state of
complete isolation, even at the end of the rotation, just before
the felling is made. As soon as the crowns of the standards begin
to touch one another, the coppice is in danger.

It will not be necessary each time to make a calculation as
to the superficial cover of each size of reserved tree. As a general
rule the standards will stand over one quarter, or as a maximum,
one third of the area, and local experience will generally be
available to assist one in deciding on the right number of stan-
dards per acre. The light-requirements of the species concerned,
and in particular the amount of shade thrown by the species
forming the overwood will of course affect the question. Then
there is the further matter of the number of rotations during
which a certain proportion ( and what proportion ?) of the reserves
are to be kept standing. It is not often that a standard can be
profitably kept for more than four or five coppice rotations.
Here again the size and age of the kind of timber required under
the object of management must be referred to, and at the same

vi] METHODS OF TREATMENT 37

time it must be remembered that a tree cannot support the
effects of sudden isolation several times without some degree of
injury and loss of quality. Also we have to arrange for a pro-
gressive process of selection, because a large proportion, probably
two-thirds, of the standards of two rotations old, will have to
be eliminated as unfit for further reservation, and there will
probably be only two or three trees per acre left of sufficient
value to be worth reserving for four or five rotations. The pre-
scription in our working- plan will therefore run somewhat as
follows, taking these figures simply as an example: There will
be reserved about forty standards of all ages per acre, and no
tree, unless in exceptional circumstances, will be retained for
more than four rotations (when they would probably be about
TOO years old), and that at each felling about two-thirds of the
number of standards of each age will be felled, and only the
best retained. Then a rule embodying the well-known silvi-
cultural conditions that control the selection of stems for
reservation from out of the underwood, relating to species,
origin, shape, etc., will be given, and lastly the distribution of
the reserves must be remembered, and, if for example there are
to be forty standards per acre, there should be four standards
reserved on each square chain.

In the above example, there might be on every acre, twenty-
seven standards of one rotation's age reserved from out of the
underwood, nine standards of two rotations of age, and three
standards of three rotations of age, which would ordinarily be
felled at the close of their fourth rotation.

Prescriptions will then be drawn up for whatever subsidiary
operations may be considered necessary. These will be cleanings
and thinnings, which will be carried out by area on purely
cultural lines. There may be one or two cleanings carried out
while the underwood is still young, then one cleaning perhaps
at mid-rotation, and a thinning about half-a-dozen years before
the coppice is cut. The frequency and nature of these tending
operations will depend entirely on cultural considerations, and
on the light-requirements and relative rate of height-growth of
the principal species. The rules should state the nature and
object of each operation, but it is to be presumed that the

38 METHODS OF TREATMENT [CHL

forester in charge of the forest will have sufficient professional
knowledge to carry out all ordinary operations in a fit and
proper manner.

37. Methods included in even-aged high-forest.

Under the head of even-aged high-forest, there are a small
number of variations of the method of treatment which will have
to be considered separately. These are:

(1) The uniform method.

(2) The group method.

(3) Clear-felling with natural regeneration.

(4) Clear-felling with artificial regeneration.

(5) Strip-felling.

38. The Uniform method.

The uniform method of successive regeneration fellings, called
in France the method of natural regeneration and thinnings,
and in Germany the shelter-wood compartment system, is the
typical method of even-aged high-forest management, and the
group and strip methods are merely variations of it.

In this method the working-circle is divided into a few
(generally about four to six) blocks of approximately equal
area, each containing an equal range of age-classes. The number
of blocks to be so formed is found by dividing the rotation by
the number of years considered necessary under existing con-
ditions to complete the regeneration of a block by successive
regeneration fellings.

Thus, if it was estimated that about thirty-six years would be
required to regenerate completely a block of mature crops under
conditions where natural regeneration was rather difficult and
slow, and the whole rotation was 144 years, there would have
to be four blocks, and Block I would contain the crops forming
the oldest quarter of the growing stock ; or if the rotation were
TOO years, and a period of twenty years was considered sufficient
in which to regenerate a block, there would be five blocks. In
this way the area is divided up into blocks corresponding to the
same number of periods into which the rotation is sub-divided.
These blocks are therefore called periodic blocks, because each
block is to be regenerated in the corresponding period, and the

vi] METHODS OF TREATMENT 39

old mature crop replaced by a new crop of seedling growth
during the course of the period. Block I, the oldest block, in the
first period; Block II in the second period, and so on.

The first step then is to classify all the compartments and sub-
compartments composing the working-circle, by age, and to
arrange them by groups of ages into four or five blocks of equal
or equiproductive area. This brings us to the question of whether
these blocks are to be self-contained, that is, each of one holding,
or whether they are to be composed of compartments scattered
about all over the working-circle.

A compact block of a single holding is always a convenient
and orderly feature of a plan, but it is not essential, and if such
blocks can only be formed at the cost of many discrepancies in
age-class, and consequently of the necessity of shifting a lot
of crops about, out of their regular turn as indicated by their
age, it is better to give up the idea of an entire block all of a
single holding, and to be content with a block1 composed of
crops of the requisite ages, scattered about over the forest.

(Note. In reviewing the different methods of treatment, we
are going to pass over the matter of felling-series for the time
being, for the sake of clearness. Except that each felling-series,
which is necessarily self-contained as far as possible, must include
a complete succession of all age-classes occupying equal areas,
the formation of felling-series does not affect the method of
treatment, and in the general working scheme it merely forms
a detail regarding the location and distribution of the prescribed
operations.)

Now since the principal fellings during any period are confined
to the block corresponding, and as tending operations are mean-
while carried out in all the other periodic blocks alike, it might
be sufficient to compose one block only at any given time,
namely the block coming under regeneration, and to leave the
separation of the other blocks to the future. For the duration of
any given period it is only necessary to have the one block
defined, and the three or four other blocks may be left to be
arranged when their turn comes. A further step in the way of
devolution now becomes visible, and, that is that, instead of
having a fixed permanent periodic block, it would be sufficient,

40 METHODS OF TREATMENT [CH.

and might be advantageous, to have a floating block of approxi-
mately the same area, always formed of mature crops, most in
need of regeneration, but revised and re-constituted say every
ten years, so that at each decennial revision all areas in which
the regeneration was completed would be thrown out, and fresh
areas of the same extent fit for regeneration taken in. This
quartier bleu, as it is called in France, differs from the ordinary
periodic block in that it has not got to be regenerated during
a time prescribed, but is an area composed of all the compart-
ments in which regeneration fellings are to be either started or
continued during the time. Provided that the rate of progress
was suitably regulated by the prescriptions to determine the
annual yield, the whole working-circle would in this way be
worked through and progressively regenerated in a manner
offering great elasticity to silvicultural conditions, though with
a risk of some future disorder ensuing.

It is evident that, unless there is already a fairly regular
succession of equal age-classes in the crop, the formation of the
complete series which is required for each self-contained periodic
block of equal area, will not readily be obtained, and in order
to equalise the areas of the blocks it may be necessary, on ac-
count of its enforced topographical position, to include in one
periodic block a compartment which, from the point of view of
its age, ought to be placed in a different block. In such a case
this compartment might have to be regenerated in a period other
than that corresponding to the block in which it is of necessity
placed. Absolute uniformity is not to be expected — at any rate
until the second rotation. Then with regard to the internal sub-
division of these periodic blocks, it is only in very exceptionally
favourable circumstances that regular equal annual coupes can
be laid out. The reason for this is that the regeneration does not
proceed like clock-work, and that the successive regeneration
fellings will necessarily depend for their progress on the gradual
development of the young crop which is being created.

Good seed-years may only occur at infrequent intervals, and
the regeneration must necessarily depend on cultural conditions,
and cannot be forced. The yield therefore is nearly always
regulated by volume, based on the cubic contents of the old

vi] METHODS OF TREATMENT 41

standing crop which is to be removed within the period, and this
annual volume may be extracted from any part of the block under
regeneration, whether in the form of seed, secondary or final
felling, according to silvicultural requirements. In the rare
cases in which annual coupes can be laid out on the ground, the
yield would be regulated by area, but the volume of timber
becoming available year by year during the period would be
easily ascertainable.

A general working scheme will then be drawn up for the
whole rotation, and a tabular statement prepared showing
what compartments have been allotted for regeneration to each
period; and a special plan will be similarly prepared in tabular
form showing the areas to be worked over during the coming
period by regeneration fellings regulated by volume, and showing
the ages of the crops occupying the compartments that form
Block I. A table of the tending operations, cleanings and
thinnings, according to cultural requirements, to be carried out
over the whole working-circle during this same first period,
indicating the periodicity of these operations, and the areas to
be worked over each year up to the end of the period will also
be prepared. These subsidiary fellings will be regulated by area
only, but cultural rules may be issued, calling attention to any
special features that may exist. The calculations on which is
based the regulation of the annual yield will be discussed in the
following chapter.

If the crop is a mixed one, rules will be issued applying both
to the regeneration fellings and to the tending operations, laying
down the cultural procedure to be followed in each case, so that
the more valuable species may be protected against other com-
peting kinds of trees, and favoured at each stage of its develop-
ment. A judicious control of the light conditions will enable the
forester to create a young crop of the composition desired, and to
direct the development of the crop both in quantity and quality.

39. Clear-felling with natural regeneration.

Clear-felling, with natural regeneration is an exceptional
method of treatment which is only possible under specially
favourable circumstances. An instance occurs in the forests of
the maritime pine in the sandy region of the Landes, in France.

42 METHODS OF TREATMENT [CH.

This pine seeds freely every year, and reproduction takes place
very easily on the loose sandy soil. The working of the forest is
based entirely on area. Annual coupes are laid out, rectangular
strips lying at right angles to the wind. Each year the coupe of
the year is clear-felled, and the area regenerates itself naturally
from seed on the ground. The working-plan lays down the pro-
cedure to be followed in tapping for resin. The rotation is
seventy-five years. For the first fifty years, thinnings are made
quinquennially, and the trees to be removed are tapped for
one season before being felled. From fifty to seventy years of
age the whole crop is tapped lightly, and then during the last
five years before the felling, the trees are all tapped as intensively
as possible. The forest is carefully fire-protected. The preparation
of a working-plan for a pine forest worked for turpentine requires
a detailed knowledge of the local conditions of soil and climate
affecting the growth and regeneration of the pine, and also of
the production of resin, and the best method of collecting it.
This is an instance of a special industry in which commercial
experience, as well as silvicultural knowledge, is necessary.

With local experience of these matters, the drafting of rules
for a working-plan of this type of forest offers no particular
difficulty, as the working scheme is a very simple one.

40. Clear-felling with artificial re-stocking.

This method, which is a very common one in Britain, is easy,
but expensive, and is only suited to small areas, such as privately
owned woodlands. There is often a danger of injury from insect
pests. From the point of view of management, this method offers
no difficulty. The yield would in most cases be regulated by area,
on which basis the whole plan would be drawn up.

A plan of progressive clearing and re-planting by area would
be drawn up for the next twenty years or so, while periodic
tending operations and improvement fellings would have to be
prescribed year by year for the other parts of the forest.

4 1. 9 Strip-felling.

Strip-felling resembled clear-felling with natural regeneration,
except that we have here a succession of regeneration fellings
under a shelter-wood instead of a single clear-felling. The
working is based on area, and the annual coupe is a long narrow

vi] METHODS OF TREATMENT 43

strip usually placed at right angles to the direction of the wind,
which is generally the controlling factor of the climate in the
regions where this method is practised. The idea is to get side
protection against wind, drought, frost and sun, combined with
overhead light.

The forest is divided up into periodic blocks in the ordinary
way, and a period of twenty or thirty years allotted for the
regeneration of each block. The fellings, which consist of suc-
cessive strips on which seed, secondary and find fellings, follow
one another in due succession at intervals of a few years, always
march against the wind, so that the young regeneration is
sheltered by an old crop. If the wind conditions are severe,
severance fellings must be made in advance to protect the lee-
ward crops from being damaged by exposure to the wind.

This method is necessarily a rather rigid one, and in order to
regulate the rate of progress of the regeneration to fit the period
allotted, it will usually be convenient to institute a number of
cutting-series, and at the same time to vary the width of the
annual strip felled over. By a combination of these two expedi-
ents, the rate of progress of the regeneration can be controlled.
It may, however, be often found necessary, in all probability,
to supplement the natural regeneration by artificial re-stocking.

42. The Group method.

The group method is intermediate between the Uniform and
the Selection methods, but is generally included among the
methods applied to crops of mixed ages. It hardly forms a
separate method of treatment, but is rather a silvicultural
variation which may be applied either to the Selection method
in crops of mixed ages (Group-Selection), or to the Uniform
method in even-aged crops. In the latter case, the young
crops resulting from this kind of regeneration felling will be
less even-aged than those created under the Uniform method by
compartments or by strips, and may contain groups of young
growth varying by thirty years in age. This results from the
fact that the regeneration area is generally larger than in the
ordinary Uniform method, and the regeneration period con-
siderably longer. The organisation of the working-circle, and the

44 METHODS OF TREATMENT [CH.

formation of periodic blocks, are the same. There will be of
course no annual coupes laid out, but the possibility will be
extracted from every part of the block under regeneration in
which there are groups of young growth ready for extension.
The annual yield is determined by volume, and the regeneration
fellings will be progressively conducted all over the block during
the period by purely cultural considerations, by the removal
of the largest trees over advance growth, and by the subsequent
expansion of these groups by the progressive extraction of the
rest of the old stock. Preparatory and seed-fellings will often
not be required, as the fellings may follow the regeneration
instead of preceding it. All these points, however, are matters
of silviculture rather than of management, and in the working-
plan it will only be necessary to give effect to them in the rules
prescribing the nature and mode of executing the fellings. Some
provision may have to be made to facilitate the extraction of
the old crop without damage to the surrounding young growth.

43. The Selection method.

The high-forest of mixed ages, worked by the Selection method,
is, from the point of view of management, extremely simple.

Here we have the forest in its natural irregular condition;
there is no artificial separation of age-classes, and there is no
division of the area into periodic blocks. The whole forest is
theoretically the same everywhere at any time, and any acre
in it is exactly like any other acre, and contains trees of all ages
from one year old up to the limit of the rotation. Since, however,
in practice it is not possible to work over the whole area, which
is often very extensive, every year, in order to pick out the trees
which have just attained exploitable dimensions, a felling-cycle
is adopted — generally between five and thirty years — and the
forest is divided into a corresponding number of sections, one
of which is worked over each year in succession. With a short
felling-cycle the crop retains all the characteristic features of the
irregular forest, while with a very long felling-cycle, it gradually
approaches the even-aged type. The considerations which should
determine the length of the felling-cycle are administrative and
silvicultural. The annual sections or coupes should be of manage-

vi] METHODS OF TREATMENT 45

able size, and capable of effective supervision. Extraction and
transport should be cheap and easy. Then taking into considera-
tion the light-requirements of the principal species, the cycle
should be such that no too great interval of years will lapse
between two successive operations on any part, nor should it be
so low that the crop will be fatigued and damaged by too frequent
fellings. It will be noted that if a felling-cycle of twenty years,
for example, be applied, we are going to harvest twenty years'
accumulated production on one-twentieth of the area, instead
of taking each year's production off the whole area.

The determination of the girth limit which is adopted as the
size of maturity will result directly from the definition of the
object of management, taken in conjunction with the size
(easily ascertainable) of the firstly physical, and secondly com-
mercial, maturity of the average tree.

The age corresponding to the size adopted as the exploitable
size is obtained as the result of a large number of ring-countings
of sample trees. The exploitable age, in round numbers, fixes
the rotation, of which the felling-cycle will for convenience be
generally taken as a sub-multiple.

Now although the constitution of the timber crop is hidden
from our eyes, because the trees which form it are growing one
above another, all mixed up in the utmost irregularity, there are
two outstanding conditions which are necessary to enable the
realisation of an equal annual yield in perpetuity: firstly, re-
generation must be taking place every year without intermission
on every acre of the area, and secondly there must be a complete
and regularly graduated succession of all age-classes year by
year, all occupying equal areas, all over the forest. This equal
series of age-classes must exist although we cannot see it. In
addition, for the annual yield to be a maximum, it is of course
necessary that the forest should be fully stocked.

The only way in which the constitution of the crop can be
ascertained is by making enumerations, and counting the number
of stems in each group of size-classes. If the area of the working-
circle, or felling-series, is small, we might make a complete
enumeration, or if the area is too big, we should make a partial
enumeration, either by sample plots, or, better, by linear surveys,

46

METHODS OF TREATMENT

[CH.

all over the forest, and take countings over 5 or 10 per cent, of
the whole area. These figures multiplied up will give us an
estimate of the stock, and the proportion of the different groups
of size-classes throughout the whole forest. An inspection of
these gradated totals will at once tell us (more or less) if the suc-
cession of age-classes be anything like complete and regular, and
we may have similar figures for other forests of the same kind,
growing under similar conditions, with which to compare them.

It is possible, however, to gauge the corrections of the pro-
portions in another way.
If we represent graphically
five groups of age-classes
of equal area, as in the
figure, the volumes of these
five size-groups will be
proportional to the five
vertical columns A, B, C,
D, and E, into which the
triangle representing our . Area,

whole growing stock, is divided; and these five areas evidently
bear the proportion of 9 : 7 : 5 : 3 : i. The volume of A then
is ¥9g- of the whole; of B, -fgi and so on.

Now suppose that in the beech- woods of the Chiltern hills,
it is known from a large number of past measurements, that the
average stem of each of the following five size-groups contains
the number of cubic feet given in the second column of the
table here shown, and that the total volume per acre of a fully
stocked crop is say 3000 cubic feet.

Per Acre.

Size-class
Inches of
quarter-
girth

Volume of
average tree
of the class,
cubic feet

Volume
of whole
size class,
cubic feet

Number of
trees in each
size class

Percentage
proportion
of number
of trees

o-3

0-25

I2O

480

54'4

3-6

1-50 360

240

27-25

6-9

7-30

600

82

9

9-12

19-40 840

44

5

12-15

29-60

1080

36

4-25

3000

882

IOO

vi] METHODS OF TREATMENT 47

Under these local conditions of growth, this table gives us
the percentage proportion of each group of size-classes, if the
succession is complete and regular, and occupies equal areas.

It would not be very safe of course to take these figures for
the very smallest size-class, which is the least easy and the least
important to estimate, but we get some idea at any rate of the
proper proportions that ought to exist, on every acre, of the
larger and middle-sized classes. We might perfectly well work
this out in greater detail by taking fifty or any other number of
sizes, instead of making only five groups.

Another good method of ascertaining whether the relative
proportions of the different age-classes are correct, is to plot a
curve to represent these proportions after each enumeration.
It is possible to plot a normal curve of this kind, and any
deviation from the normal will at once be clearly indicated by
comparison with it. This will show which age-classes are in
excess, and which are deficient.

It is to be noted that under the Selection method the regenera-
tion of the forest does not primarily depend on the fellings as
it does in the even-aged forest. The principal fellings in the
Selection method may often to some extent result in some local
regeneration, and still more may they assist the development
of young growth waiting to be uncovered, but they are not
entirely responsible for the general regeneration of the forest,
which should be taking place naturally and automatically over
the whole forest all the time.

When the group method is applied to forests of mixed ages
worked by the Selection method, mature trees are extracted by
groups instead of by single stems, and these groups are subse-
quently expanded by later fellings, as the young growth in and
around them develops. In this case the fellings bear the full
character of regeneration fellings, although the natural regenera-
tion is not confined to the areas actually included in these group
fellings.

Under the Selection method, tending operations are generally
of less importance than they are in even-aged crops. Unless,
however, the felling-cycle is a very short one, of five or ten years,
it will be necessary to carry out a cleaning or improvement

48 METHODS OF TREATMENT [CH.

felling, including the extraction of dead or dying trees, once at
mid-period at least. In the year following the principal felling
too, it may be found very beneficial to go over the same ground
again with a cleaning, to cut back all young stems that have
been broken or damaged in the previous year's exploitation,
and to extract all bad and unmarketable material. A tabular
statement will be prepared, showing for each year during the
duration of the special plan what areas have to be worked over
by these subsidiary operations year by year, and rules framed
to state the nature of each kind of tending operation, its cultural
objects, and the manner in which it is to be carried out. This
tabular statement will be similar to the one prepared for the
principal fellings, which also will be accompanied by cultural
rules to supplement (and to take precedence of) the regulation
of the yield — rules which are of the greatest importance, since
they will touch on such fundamental matters as the maintenance
of the leaf-canopy and of the fertility of the soil, the supply of
seed, shelter against wind and exposure, favour shown to the
more valuable species in the crop, etc.

44. Provisional methods.

The cases in which a provisional or temporary method of
treatment has to be applied may be classified into two categories :
first, there are the forests that for the future are to be worked
under a new method of treatment, which renders it necessary
to re-constitute the growing stock, and to arrange a different
succession of age-classes to correspond with the new rotation;
and secondly there are the forests of which the wood-capital is
so deficient or so irregular that a preparatory period must be
adopted during which this wood-capital may be improved and
added to, until the growing stock has been sufficiently increased
and completed to render it fit for working under a regular
method of treatment. We have therefore to consider methods
of (i) conversion, and (2) improvement.

The commonest and most important cases of conversion are
from Coppice- with-standards to even-aged high-forest, and
secondly from Selection to even-aged high-forest.

vi] METHODS OF TREATMENT 49

45. Conversion from Coppice-with-standards

to Uniform.

In the case of conversion of Coppice-with-standards to the
Uniform method, we have first of all to arrange for a preparatory
period, during which the coppice will grow older, and so will
gradually lose the power of reproducing itself, when cut, by
stool-shoots. Then, when this period of waiting is over, we can
begin to start the creation of the new series of age-classes by
making regeneration fellings over a suitable area in that part
of the forest which is most fit for it. The whole process of con-
version cannot therefore be properly accompanied in a shorter
time than the number of years in the preparatory waiting period
plus the new rotation of the Uniform method. This total will
probably be of the order of 150 to 200 years.

Now we have already agreed that we are not going to attempt
to tackle so long a period as this in any working- plan. We are
going to be content to provide, with a moderate degree of detail,
for something like twenty, or at most thirty or thirty-five years,
and we are not going to attempt to estimate results, or discuss
figures, or put forward proposals in detail for such a lengthy
future as 150 or 200 years.

Let us then suppose that the rotation under the coppice
regime was 25 years, and that the rotation under the new
Uniform method is to be 175 years divided into five periods of
thirty-five years each, and let us suppose that the tree we
principally have to deal with does not lose the power of repro-
ducing itself freely by stool-shoots until it is at least sixty years
old. Under these circumstances we should be led to take thirty-
five years as the duration of the waiting period, so that at the end
of that time our crop would be sixty years old and therefore
fit to start regeneration fellings in.

Since, however, we have to convert the entire stock into a
regular succession of ages, each occupying an equal area, we
have got to conduct our regeneration fellings gradually year by
year over the whole working-circle, and we cannot start them
until thirty-five years have elapsed.

The programme of events will then be as follows: During
the first period of thirty-five years we shall select one block, the

j. F. 4

50 METHODS OF TREATMENT [CH.

one that is culturally in the best condition for the purpose, and
carry out a few thinnings and minor cultural operations in it
at intervals of eight or ten years while it grows older, and in the
other four blocks we shall continue the coppice treatment. In
the second period of thirty-five years, the regeneration of our
first block will be started, a second block will be selected for
submission to the waiting period, and coppice fellings will con-
tinue in the other three blocks. In the third period tending
operations, cleanings and thinnings will be carried out in
the now converted Block I, regeneration fellings will be
taken through Block II, preparatory operations during the
waiting period in Block III, and coppice fellings in Blocks IV
andV.

There are thus four different kinds of operations going on now,
and the whole process of conversion is going to take 210 years.
This is the general scheme. Our working-plan, however, will
only deal in detail with one period of thirty-five years. It is
unnecessary here to discuss the nature of these four different
kinds of operations, which are described in any book on silvi-
culture. In the preparatory period they will consist principally in
thinning out the coppice poles, so as to give the best of them
more space to spread in. The regeneration fellings, and the subse-
quent tending operations in the coverted part of the area, will
be similar to, if not identical with, such operations as commonly
carried out in even-aged high-forest. The temporary coppice
fellings continued in the later part of the area will be ordinary
coppice fellings, but the rotation should be a long one, and in
any case new coppice coupes will have to be laid out at the
beginning of each period, as the area under coppice is gradually
being reduced. Only in the case of the last coppice felling before
a coppice area is brought under trie waiting period, should the
largest possible number of standards be reserved.

The above example shows an outline of the method to be
followed in a plan of this sort, the general working scheme for
the whole business, and the special plan for the period on which
we are entering. The whole thing can be managed on a basis
of area, even the regeneration (or conversion) fellings, unless
natural regeneration is difficult, in which case the fellings can

vi] METHODS OF TREATMENT 51

be made by volume and be carried out in any part of the block
that is culturally fit for them, as in the ordinary Uniform method.

Tabular statements will be drawn up for each kind of opera-
tion, showing year by year throughout the period what areas
have to be worked over, and rules will be framed to determine
the nature of, and mode of execution of, each kind of felling.
The whole operation is a cultural one, and considerable liberty
should be left to the local operator with regard to the application
of practical details.

Then, in addition to the four kinds of principal fellings going
on in different parts of the area, there will also be subsidiary
tending operations in each part ; these will be cultural operations
of a nature suitable to the condition of the crops and to the
treatment that they are undergoing, and will be carried out with
a periodicity suitable to their light-requirements, their density,
composition, and condition.

46. Conversion from Selection to Uniform.

Conversion from irregular to regular high-forest is a process
that every even-aged high-forest now worked under the Uniform
method, or one of its variations, has had to pass through, since
the natural forest is always composed of crops of all ages mixed
up over the whole area and the even-aged condition is an arti-
ficial one.

Under certain well-known conditions the Selection method is
a very excellent one, arid offers scope for intensive working, but
under other conditions, it is often desirable to introduce the
regular Uniform method in order to obtain the great advantages
that result from growing trees in close even-aged crops.

Theoretically the irregular high-forest is supposed to be of
uniform irregularity all over, and one part is supposed to be
exactly like another. In practice, however, this uniformity .of
irregularity (if the phrase be permissible) will not be found, and
there will always be certain parts of the area containing a pre-
ponderance of old trees, other parts stocked principally with
middle-aged trees, and other parts consisting largely — though
of course not exclusively — of young growth.

Now in order to create a regular equal graduated succession

4—2

52 METHODS OF TREATMENT [CH.

of even-aged crops over the whole area with which we are
dealing, aged from one year old up to the age of exploitability,
which is probably between 100 and 200 years old, it would seem
at first sight necessary to spend an equal number of years to
achieve this result. In practice this conversion may be com-
pleted in a considerably shorter period, because absolute
uniformity is not attempted, and therefore a great deal of the
younger growth already on the ground is left there to be in-
corporated in the new crop, although it will be of course really
a good many years older.

During the process of conversion then, what we understand
by an even-aged crop is not a crop composed entirely of trees
of the same, or even approximately the same, age, but it is a
crop sufficiently even-aged to be regenerated, when its time
comes, in one set of regeneration fellings. Exact uniformity
would entail also a great waste of production, and the sacrifice
of a large quantity of immature stock, so we shall take a middle
course and be satisfied for this first rotation if each part of the
crop is mainly composed of trees within, say, about thirty years
of the theoretical age.

The procedure then will be to examine carefully each com-
partment and sub-compartment, and to make enumerations over
representative areas — either by linear surveys, or by sample
plots — to ascertain the predominant proportion of size-class in
each part of the crop, and we shall prepare a table to collate size
with age. Then, after determining the rotation to be adopted
under the new method of treatment, and having settled on a
suitable period within which to complete the regeneration of any
block, we shall form a general framework of the plan for con-
version, allotting each unit of area — compartments and sub-
compartments — to its appropriate period in this general scheme.

In periodic Block I, will be placed those parts of the crop in
which regeneration is already abundant, and trees of the largest
class numerous. In Block II, crops containing most class II
trees, or class I and III trees, if class II trees are deficient; and
so on.

In the last block will be placed the poorest and least satis-
factory parts of the crop, which require to be nursed up and

vi] METHODS OF TREATMENT 53

improved before their turn comes round for conversion. This
general scheme for the allocation of each part of the crop to
its most appropriate position in a periodic block is the most
important part of the working- plan. The periodic blocks will
have to be composed of areas scattered about all over the forest,
and are not likely to be able to be compact self-contained areas.
Periodic Block I will at once be brought under conversion, and
regeneration fellings, regulated by area and cultural rules, will
be carried out.

Seed fellings will probably be unnecessary, so we shall only
make secondary and final fellings, in which all the old stock
standing on the area in hand, down to, say, about three feet in
girth, will gradually be removed. Everything below this limit
will be left, if good, to form part of the new crop. If the cultural
conditions of the regeneration permit it, it might be possible to
prescribe the number of fellings and their periodicity, but as a
rule such a prescription would be unwise.

This procedure would be based on the assumption that the
conditions of regeneration were straightforward and easy; if
this is not so, a less rigid method must be adopted, and instead
of prescribing the number of fellings by area with a fixed period-
icity, we must fix the possibility by volume, and instead of
having defined annual coupes, we should make the regeneration
fellings in any part of the block that was most ready for them,
and be guided by the cultural requirements of each part.

A tabular statement showing the areas to be worked over
year by year will be prepared for the duration of the first period,
and a set of cultural rules, laying down the details of the manner
in which these fellings are to be carried out, and providing what
is, and what is not, to be felled, under special circumstances,
will be carefully drawn up to accompany it. The operation being
a purely cultural one, these rules will be of great importance, but
they should be framed so as to allow some exercise of discretion
to the officer who carries them out. Some subsidiary operations,
such as cleanings and cutting-back, will be prescribed to follow
the fellings in Block I.

Meanwhile in all the other blocks, selection fellings will be
continued during the first period, at the end of which time

54 METHODS OF TREATMENT |CH.

Block II will be brought under conversion and regenerated in
the same way in the second period. These selection fellings will
consist in removing mature stems which can be left standing no
longer, but in addition to this they will go further, and will be
improvement fellings in which worthless material of any size
will be removed in order to assist in the development of the
more valuable trees.

The position of every part of the forest in the general scheme
of working being known, we shall know the girth limits of the
trees to be specially favoured on each part of the ground in order
to prepare the crop to take its place in the approaching con version.
These selection fellings therefore in the blocks not yet brought
under conversion will aim at inducing to some extent a state of
uniformity in the crops, and of regularising them to the type
required to fit in with the conversion scheme.

47. Improvement method.

The Improvement method is a provisional treatment applied
to forests which are in a very bad state, containing a large pro-
portion of unsound and worthless timber, and therefore unfit,
until to some extent restored, for working under any regular
method. The object is therefore to improve the growing stock
during a period of years, during which time the forest will be
treated on purely cultural considerations, and no revenue be
sought from it. During this provisional period, then, all trees, the
extraction of which is culturally desirable, will be removed, but
no others; and as a general rule no tree will be removed unless
there is a better one to take its place. As a method of manage-
ment, the arrangement will be exactly as under the Selection
method. A suitable felling-cycle will be fixed, and the forest
divided up into as many sections, over one of which an improve-
ment felling will be carried out each year. In order that in the
future there may be no intermission in the yield it is of course
necessary to see that natural regeneration always continues to
take place freely over the whole area year by year. There is
no possibility fixed, and the fellings are carried out by area on
purely silvicultural principles.

From the point of view of the working- plan, this method is of

vi] METHODS OF TREATMENT 55

extreme simplicity : the most important features of the arrange-
ment are the adoption of a felling-cycle of the (culturally) correct
duration, and the cultural rules controlling the fellings.

These rules will state what timber is to be removed, and under
what circumstances; they will also provide against too great
reduction of the leaf-canopy, and of the density of the crops, and
against over-exposure of young growth, and of the soil. Some
subsidiary cultural operations may also be arranged in a second
tabular statement showing the areas to be worked over year by
year.

These minor operations and their periodicity will depend on
the cultural requirements of the crop. In any case it will prob-
ably be wise to make one in the year following the principal
improvement fellings, in which a cleaning will be made over the
same area, and unsaleable material of all kinds extracted (all
available marketable timber will have been taken out in the
principal improvement felling and sold standing or felled), and
all young growth of good species, but of bad shape, or damaged
in the fellings, cut back. If the area is very large, several
felling-series may be made in order to reduce the size of the
annual coupe, as the felling-cycle should not usually be longer
than twenty years at most.

CHAPTER VII. CALCULATION OF THE POSSIBILITY.

48. Theory and practice.

IF everything were as it ought to be, the yield of the forest
should be equal to the normal increment, that is, the maximum
possible production per acre per annum under the rotation
adopted, that the soil and climate permit. In highly organised
forests where intensive working has been carried out for a long
time, and where reliable yield-tables and increment-tables and
exact statistical data of all kinds are available, the calculation
of the possibility can be strictly worked out in accordance with
the theory. In everyday practice, however, where such con-
ditions rarely obtain, the regulation of the yield is generally
calculated in a simpler and less theoretical fashion. This is
especially the case when we have agreed to be content with
short views, and to fix the yield only for twenty or thirty years,
with a revision of the calculation every ten years. What actually
happens in most cases is that we have a definite area to be worked
over during a definite number of years, say twenty years for
example, during which time we have to regenerate this area and
to remove all the standing stock of old trees. We should then
make an estimate of the actual volume of this mature crop, add
on a trifle perhaps for future increment during the period, and
then divide this total by the number of years, to get the annual
yield for the period. This is the simplest method, and there is
nothing theoretical in it.

The regulation of the yield may be by area, by volume, or

by both.

49. Regulation by area.

First, by area. This is the method applied to coppice fellings,
and to clear-fellings. The area under working is divided by the
number of years in the rotation, and this gives the size of the
annual coupe. If the site quality varies appreciably, the coupes
may be made equiproductive rather than exactly equal in area.
In the case of Coppice-with-standards, a further regulation has
to be made with regard to the over-wood. To do this an estimate

CH. vnj CALCULATION OF THE POSSIBILITY 57

is made of the volume of timber which will be available during
the coming rotation from Uie standards that will be extracted.
No rigid prescription as to the exact volume to be removed
annually should issue, as there is always a good deal to be left
to the appreciation of the local forester, with regard both to
cultural and economic considerations, in dealing with the reser-
vation and realisation of the standards.

50. Regulation by volume of growing stock.

Secondly, by volume. These methods are based either on the
whole growing stock, or on the increment, or on both. The deter-
mination of the yield from the estimated volume of the whole
wood-capital may be effected by dividing the total estimated
cubic contents of the growing stock by half the number of years
in the rotation. We have already considered this on page 9.
This method may serve as a check to other methods but it is
not very practicable, as it involves an enumeration of the whole
growing stock, and is only true on the assumption that the
actual increment bears to the actual growing stock the same
relation as the normal increment bears to the normal growing

stock.

51. Regulation by increment.

If the determination of the yield is based on increment, the
average current annual increment may be obtained for each of
four or five age classes, by using the borer on sample trees, or
by felling and measuring sample trees; this average increment
per acre is, if necessary, reduced by a factor for density, unless
the whole area is fully stocked, and the increment thus modified
is multiplied by the number of acres of each size or age-class,
and the whole then totalled up, and divided by the number of
acres in the felling-series. This method too is chiefly useful as a
check on other methods.

Then lastly, if the yield is to be determined by volume, based
on both increment and growing stock, it will be calculated by the
formula _

x

where i is the actual mean annual increment during an arbitrary
time x, which is chosen as a convenient period for the distribution
of the excess or deficiency of the actual growing stock as com-

58 CALCULATION OF THE POSSIBILITY [CH.

pared with the normal: V is the volume of the actual growing
stock, and nV is found by multiplyi»g the actual mean annual
increment by half the number of years in the rotation.

In the statement of the formula given above, it is supposed
that the actual growing stock is in excess of the normal growing
stock, as may often be the case in virgin forests; but the differ-
ence between the volume of the actual growing stock and the
normal growing stock corresponding to the actual mean annual
increment may of course be either positive or negative.

52. Regulation by area and volume.

The best way, however, in everyday practice is to determine
the yield on a basis of area combined with volume, and this is
the method that will generally be employed in the Uniform
method (except in the rare case when a succession of annual
coupes can be employed and the working be arranged by area
only, as mentioned on page 42), or in its variations, the Group,
and the Strip methods.

Here we have a periodic block which is to be regenerated
within the period of say twenty or thirty years. The yield is
calculated solely with regard to this block and this period.
Enumerations are made and an estimate is prepared of the

actual growing stock, neglecting young growth if any exists.

F + if
Then the annual yield for this period will be Y= —j~- ,

where / is the future increment accruing during the period p,
and V is the present volume of the actual standing crop. which
is to be extracted during the same period.

The reason for adding only one half of the increment expected
to take place during the period is that the other half will remain
on the ground after the passage of the fellings. If we have made
our enumerations and estimates this year and make the first
felling next year, we shall only realise one year's increment on
the first coupe, and two years' increment on the second coupe,
and so on, so that it will not be till we make the last felling of
the period that we shall harvest twenty years' increment added
on to the original volume. Thus for the whole period we shall
harvest half the increment taking place over the whole periodic

vn] CALCULATION OF THE POSSIBILITY 59

block during the whole period, the other half remaining in a
succession of graduated crops on the ground after the passage
of the fellings. The increment may be expressed either as a
percentage of the growing stock, or as so many cubic feet per
acre per annum. It is usual to make a rather low estimate of it,
so as to keep on the safe side, and to have a reserve always in
hand in case of accidents, such as wind storms, etc. Any excess
of material is easily adjusted at the decennial revision.

53. French method.

In France, before making the calculation of the possibility
based on an estimate of the volume of the mature crop to be
removed during the coming period, it is customary to ascertain
whether the older age-classes in the crop which will come under
working in the near future, are approximately in correct grada-
tion; so that, if desirable, an adjustment can be made in the
regulation of the yield in case of any marked excess or deficiency
in the older parts of the crop. This method is employed both
with even-aged high-forest, and with Selection-worked forests.

Suppose for example that 6 feet in girth were adopted as the
size of maturity; then an enumeration would be made, and the
whole stock would be divided into three groups. The youngest,
up to 2 feet in girth, the middle-aged third from 2 to 4 feet in
girth, and the oldest third would include all stems of over 4 feet
in girth. The estimated aggregate volumes of the oldest and of
the middle-aged thirds would then be compared, and if they
were found to bear respectively the ratio of five to three, it
would be assumed that the age-classes were in sufficiently correct
proportion.

This does not mean to say that the crop is necessarily by any
means normal in volume, or
fully stocked. This calcula-
tion is based on the method
which we have already men-
tioned on page 46, and which
may be graphically demon-
strated by the figure, in
which the volumes of the three thirds of the growing stock

Volume
propor-
tionate
to age.

Area

60 CALCULATION OF THE POSSIBILITY [CH.

are relatively proportional to the three divisions of the triangle,
and which therefore bear to one another the proportion of five to
three, and three to one.

If now it is found that the proportion of five to three does not
exist between the oldest and the middle-aged thirds of the crop,
the difference is subtracted from the third in excess and added
to trie third showing deficiency, so as to obtain the correct
proportion. When this adjustment has been made, the modified
total volume of the oldest third, plus the addition of a modest
increment for half the time, is divided by the number of years
in one third of the rotation, and this gives the annual yield for
that time. If timber extracted in thinnings or improvement
fellings carried out in the middle-aged parts of the forest is of
a size to bring it to be included in the possibility as prescribed,
provision should be made for this in the calculation of the yield
by adding to the total volume of timber in the oldest third of
the crop a suitable proportion of the estimated future increment
of the middle-aged third during the same period. In France the
allowance for future increment is sometimes neglected, so as to
keep well within the possibility, and to have a reserve always
in hand wherewith to meet unforseen contingencies. This cal-
culation of the annual yield is revised every ten years.

54. Calculation of yield under Selection method.

Under the Selection method we have already the following
three limitations; firstly, area as determined by the size of the
felling-series and the number of years in the felling-cycle
adopted; secondly, a girth limit, which is the size adopted as
the size of exploitability, on attaining which size each tree is
fit for felling; and thirdly, cultural rules, which, although they
are of paramount importance, do not directly affect the present
calculation. Now it is evident that the first two limitations
already define exactly the annual yield, so that it is unnecessary
in addition to prescribe a fixed number of trees. It is, however,
usually convenient to know what the average annual out-turn
is going to be, but this number of trees cannot logically be en-
forced by a rigid prescription, though it may be prescribed

vn] CALCULATION OF THE POSSIBILITY 61

as a maximum, if there is any object in so doing, or given merely
as a general guide to the conduct of the annual working.

This possibility may be calculated as follows : An enumera-
tion is made of the whole stock, either by actual counting or by
estimate, and the number of stems in each of four or five size-
groups is ascertained. Suppose for example that 6 feet in girth is
taken as the size of maturity, then all trees of 6 feet or over form
Class I. Class II includes all trees with a girth between 4! and
6 feet, Class III includes all stems between 3 feet and 4^ feet in
girth, and so on. It has also to be ascertained by ring countings
how many years the average tree takes to pass from one class
to the next. Knowing then the number of trees in Class II, and
the number of years it will take the whole of this number to
pass up into the exploitable Class I, we can easily calculate the
annual rate of production of trees of the exploitable size. The
number of trees in Class II has only to be divided by the number
of years that it takes a tree to pass through that class.

This number forms the basis of our calculation of the yield,
which, it is to be noted, is not based on the existing number of
Class I trees (as might, at first sight, seem natural), because the
number of trees in Class I is purely accidental, depending on
past fellings, and tells us nothing as to the future rate of pro-
duction annually of trees of the required size.

There is, however, a further point to be considered. We do
not propose to fell over the whole area every year, but we
have chosen a felling-cycle, of, for example, twenty years, so
that we are going to confine our operations each year to one-
twentieth of the area, and we can only realise the production
of the whole forest off one-twentieth of its area on the con-
dition that we have twenty years' accumulation of production
standing, waiting for the fellings to come round. It is evident
therefore that we must have twenty years' accumulation of
Class I trees on one coupe, nineteen years' accumulation on
the next coupe, and so on down to one year's production of
Class I trees on the area worked over last year. We shall
therefore have to keep a considerable stock of Class I trees,
in regular gradated succession, always standing. The point
that we now have to consider is whether the existing stock

62

CALCULATION OF THE POSSIBILITY [CH. vn

of Class I trees will be sufficient or not for this purpose during
the first rotation. The total number of Class I trees that we
require as a working exploitable stock is the number of trees
becoming annually exploitable,— which we have already found
as the basis of our calculation of the yield, — multiplied by half
the number of years in the felling-cycle. This number then has
to be compared with the figure showing the number of Class I
trees in our table of enumeration, and any excess or deficit spread
out over a suitable number of years, and added to, or deducted
from, the original number of trees passing annually from
Class II to Class I.

1
II

III
IV

I

II

III

IV
V

A B

If the forest has not been in regular working up till now, we
have to change its constitution from A to J5.

During the first felling rotation the early fellings will depend
almost entirely on the accidental number of Class I trees that
happen to be standing on the ground, and the forest will not
come into full and regular production of an equal maximum
annual yield until the second felling-cycle, when the full suc-
cession of the necessary exploitable stock will be completely
constituted.

It will be noted that the average age of the trees forming
the yield will be greater than the exploitable age by half the
number of years in the felling-cycle.

CHAPTER VIII. THE WORKING-PLAN REPORT.

55. Form of report.

THERE is no stereotyped form of report for general use, and the
size of the report and the amount of detail it contains must
obviously depend upon the size and importance of the forest,
and on the complexity of its component parts. With this
provision, the form of the report will usually be more or less as
here given.

PART I. SUMMARY OF FACTS ON WHICH THE
PROPOSALS ARE BASED.

CHAPTER I. DESCRIPTION OF THE TRACT.

Name. Ownership. Situation.
Configuration of the ground. Elevation.
Soil and subsoil.
Climate.

CHAPTER II. COMPOSITION AND CONDITION OF FOREST.

Distribution and area. Existing subdivisions.

State of boundaries. Adjoining properties.

General description of crops, with silvicultural notes regarding
species and their regeneration.

Legal position of forests. Rights and concessions.

Sources of injury. Wind, frost, fire, game, insect and fungoid pests,
weeds.

CHAPTER III. MANAGEMENT.

Past and present methods of treatment. Results.
Special works of improvement*.
Past revenue and expenditure.

CHAPTER IV. UTILISATION OF PRODUCE.

Marketable products. Classification and prices. Lines of export;
method and cost of extraction. Local industries. Centres of con-
sumption and markets.

CHAPTER V. MISCELLANEOUS FACTS.
Labour supply. .
Forest staff.

64 THE WORKING-PLAN REPORT [CH.

PART II. FUTURE MANAGEMENT.
CHAPTER I. ALLOTMENT OF AREAS AND ANALYSIS OF THE CROPS.

Division of area into working-circles and felling-series. Reasons
for their formation.

Formation of compartments and sub-compartments.

Enumerations carried out.

Their result. Distribution of age-classes.

CHAPTER II. BASIS OF MANAGEMENT.
Object of management.

Choice of species and silvicultural treatment.
Choice of rotation.

CHAPTER III. THE FELLINGS.
General working scheme.
Special plan for the period.
Determination of the annual yield.
Tabular felling statement of annual areas.
Cultural rules for execution of fellings.

CHAPTER IV. TENDING OPERATIONS.

Tabular statement of annual areas to be worked over by sub-
sidiary improvement fellings, cleanings, thinnings, sowings and
plantings.

Fire-protection .

Miscellaneous prescriptions.

CHAPTER V. SUPPLEMENTARY PROVISIONS.
Roads, buildings, and other works: plan of execution.
Collection of data. Upkeep of records of sample plots and measure-
ments.

Organisation of forest staff.
Forecast of financial results.

Revisions.

APPENDICES.

Description of compartments and sub-compartments.
Maps.

Enumeration surveys, with map.

Record of measurements for compiling yield-tables, and increment-
tables.

Results of ring-countings and borings.
Miscellaneous.

Part I of the plan deals with the past and present, and Part II
with the future.

vin] THE WORKING-PLAN REPORT 65

Part I will therefore contain no prescription or provision for
the future, which will all be given in their appropriate place in
Part II. In Part II, the basis of future management is the object
of management as denned, and from this are deduced successively
the species (if any choice is possible), the method of treatment,
and the size of maturity under the object of management, from
which again is deduced the rotation. These sections should be
written coherently and logically, in concise and exact terms.

Chapters II, III and IV have to be written separately for
each working-circle.

56. Control Form and Forest Journal.

A working-plan is not of much use unless its prescriptions are
carried out. The control book is a means of ensuring continued
adhesion to the plan, and at the same time it forms a record of
the progress of the forest under the working-plan. It is mostly
kept in tabular form, with one book for each working-circle, and
one page (or more if necessary), for each year.

On the left-hand page is a table prepared showing in detail
the provisions of the plan; principal fellings, subsidiary fellings,
cultural operations, roads, buildings and works of all kinds, in
each locality, with the acreage of each, with the quantity of
material to be extracted, or expenditure to be incurred, are set
forth in tabular form for the year under review. On the right-
hand page opposite, a similar table is presented, in which are
filled in corresponding entries, showing what has been actually
done under each heading, and what operations have been carried
out, and their result in material and in money. A brief statement
is made to explain each deviation from the provisions of the plan,
and the reasons for the non-fulfilment in whole or in part, of any
operation prescribed. Any changes in area are recorded. This
control book is prepared each year at the close of the working
season by the forester in charge, and submitted to the owner of
the forest for his approval and orders.

An abstract of the results of the year's working in timber and
other produce, and a similar financial return for the year's
revenue and expenditure, with the results compared with pre-
vious years' figures, should be drawn up at the same time.
J.F. 5

66 THE WORKING-PLAN REPORT [CH .vn:

A'Forest Journal should also be kept up year by year in which
an informal record will be kept, in narrative form, of all matters
of interest connected with the forest and its working, which are
not already recorded in the control form. Silvicultural notes of
all kinds, especially on regeneration, will be put on record, also
anything remarkable in the way of climate, such as wind, storms,
frost, snow, or drought: then fires; fluctuations of prices, special
demands for any kind of produce, contractors, and labour
supply, etc. As a record' of cultural observations, and notes on
the regeneration and growth of the crops under the changing
conditions of each season's climate, the journal, if well kept,
forms a most valuable record of information for future use.

CHAPTER IX. BRITISH ESTATE FORESTS.

57. Outline of plan of management.

IN the management of a British woodland estate, the general
principle is the same as in a large State forest, and that is, to
get the area fully stocked with the most suitable and profitable
species, and therefore to realise annually a constant maximum
yield equal to the mean annual increment, which will give the
greatest annual revenue. This, continued with the least possible
annual expenses, will result in the highest rent from the soil.
Two conditions are necessary to start with — continuity of
management for at least one or two human generations, and a
definite object of management. Both these conditions often do
not exist, and even where they do, there will be often an in-
sufficiently stocked wood-capital and a very incomplete series
of age-classes. In such a case the working-plan, which will be
an organised attempt to convert the actual into the ideal, can
only be drawn up on very elastic principles and will aim at
getting the area completely stocked in the least possible time,
with annual receipts meanwhile to cover annual expenses. If a
plan can include several estates in the same district, it will
be very advantageous to arrange an organised supply of timber
for the local timber market, and for the producers to combine
to maintain a steady and attractive market, instead of each
selling separately at any price that the local trader likes to give
him.

The preparation of the plan will be carried out in the way that
has been "already indicated for other forests. A general survey
of the area will first be made, and some improvements may at
once suggest themselves with regard to the choice of species and
of method of treatment in different parts of the area. The first
object should be to maintain and improve the productive capacity
of the soil. The area will then be divided up into compartments
(and sub-compartments if necessary), which should usually have

68 BRITISH ESTATE FORESTS [CH. ix

a road or ride along one side, and should be of five to twenty
acres in extent. Working-circles will then be formed, and the
crops in each will be classified by age and condition into say
five age-groups of about twenty years each.

Most of the crops of about eighty years old or over will be put
into Block I to be dealt with during the first period of twenty
years or thereabouts. The general working scheme may be
rather less rigidly laid down here than it is for a large State
forest worked on a long rotation.

Block I, then, will be composed of all the old mature or over-
mature crops, which are often numerous in neglected woods,
and other areas which are in such an unsatisfactory state that
they too should be soon cleared and replanted. An estimate will
now be made of the volume of material to be extracted by
successive annual or periodical fellings during the first period.
A tabular felling statement showing the areas to be taken in
hand year by year will be drawn up, and the allotment of the
different areas will be made in consideration of the condition
of each crop, and the urgency of clearing it. A second table will
be drawn up for cultural operations, and works of improvement,
cleanings and thinnings, in the other parts of the forest.

Simplicity and economy should be the chief features of the
plan, which should result in a steady progression, annual or
periodical, towards clearing and replanting in systematic
succession, with equalised working. No unregulated fellings for
estate or any other purposes should be permitted. No high
theory, nor abstruse calculations are required, but only a
common-sense programme of operations; if, as will most often
be the case, the re-stocking of the cleared areas is to be artificially
carried out by sowing or planting, an annual plan of these opera-
tions will be required, and provision should be made for a
nursery of adequate size in the most suitable locality. Cultural
considerations to be followed should be clearly indicated, but the
prescriptions should not be too rigid in matters of detail.

INDEX

Age classes, 24
Analysis of crop, 25
Appendices, 64

Bark, deduction for, n

Basal area, 10

Basis of management, i

Block, 24

Breymann's formula, 19

British woodlands, I, 67

Cleanings, 37, 41
Clear-felling, 41, 42
Compartment, 25
Composition, 41
Constitution, 6
Continuity, 6
Control, 65
Conversion, 48, 51
Coppice, 34
Coupe, 31

Cultural rules, 32, 66
Cutting back, 44, 48

— series, 6

Dead wood extraction, 48
Density of crops, 14
Description of compartments, 26
Duration of plan, 31

Enumeration surveys, 15
Even-aged high forest, 38
Expectation value, 4
Exploitability, 45

Felling cycle, 44

— table, 35, 41

— series, 27
Field work, 23
Form factors, 13
Future increment, 21

Game preserves, 2
General working scheme, 30
Group method, 43
Growing-stock, 6

Height growth, 24
High forest systems, 34

Improvement method, 54
Increment, 9, 16, 21, 58
Interest, 6

Journal, forest, 66

Linear surveys, 15
Locality, quality of, 24

Method, choice of, 3
Miscellaneous prescriptions, 64
Mixed ages, forest of, 44

Normal age-classes, 7

— forest, 7

- increment, 7

- volume, 8

Objects of management, i
Owner's will, i

Period for prescriptions, 31
Periodic block, 38
Physical rotation, 4
Pine forests, 42
Possibility, 56
Preparatory period, 49
Prescriptions, framing of, 32
Pressler's borer, 18

— formula, 18
Private forests, i
Protection forests, i
Provisional methods, 48

Quality of locality, 24
Quarter- girth, 10
Quartiev bleu, 40

Regulation of yield, 56
Report, form of, 63
Revision of plan, 31
Ring counting, 18
Rotation, 3, 4

Sample plots, 15

— trees, 16
Schneider's formula, 19
Selection method, 43
Severance fellings, 44
Simple coppice, 34
Size-classes, 13, 61
Soil rent, 2, 67
Special plan, 30
Species, choice of, 2
Standards over coppice, 35
Stem analysis, 17

Strip felling, 43

70 INDEX

Sub-compartments, 25 Uniform method, 38

Sub-divisions of forest, 24

Subsidiary operations, 37, 41 Volume tables, 12

Supply, forests of, i

Sustained yield, 5 Weise's method, 15

Systems silvicultural, 34 Wood-capital, 5

Working circle, 27

Tape, quarter-girth, n — plan, 63
Taper, degree of, 12

Tapping resin, 43 Yield, by area, 56

Tending operations, 41 — by area and volume, 58

Thinnings, 37, 41 _ by volume, 57

Timber height, n — regulation of, 56

Time element, 5 — tables, 22
Types of forest, 29

CAMBRIDGE: PRINTED BY j. B. PEACE, M.A., AT THE UNIVERSITY PRESS.

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