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THE

OHIO STATE UNIVERSITY

BULLETIN

Volume XXV January 20, 1921

CONTRIBUTIONS IN BOTANY

Number 9
NUMBER 117

THE RELATION OF PLANT

SUCCESSION TO CROP

PRODUCTION

A Contribution to Crop Ecology

By

ADOLPH E. WALLER, Ph. D

Instructor in Botany in
The Ohio State University

Papers from the Department op Botany, Number 117

PUBLISHED BY THE UNIVERSITY AT COLUMBUS

Entered as second-class matter November 17, 1905, at the postoffice at Columbus,
Ohio, under Act of Congress, July 16, 1894.

THE

OHIO STATE UNIVERSITY

BULLETIN

Volume XXV January 20, 1921 Number 9

CONTRIBUTIONS IN BOTANY NUMBER 117

THE RELATION OF PLANT

SUCCESSION TO CROP

PRODUCTION

A Contribution to Crop Ecology

By

ADOLPH E. WALLER, Ph. D.

Instructor in Botany in
The Ohio State University

Papers from the Department of Botany, Number 117

PUBLISHED BY THE UNIVERSITY AT COLUMBUS

Entered aa second-class matter November 17, 1905, at the post-office at Colambus,
Ohio, under Act of Congress, July 16, 1894.

^

y

^

^ CONTENTS

t

ACKNOWLEDGMENTS AND FOREWORD 5

Introduction 7

A Genetic Classification of Vegetation 8

The Factors Controlling Distribution 8

The Nature of Crop Ecology 11

PART ONE

PLANT SUCCESSIONS 13

The Orientation of the Field op Ecology 15

autecology 15

Synecology 16

The Factors in Successions. 1. Climatic 17

The Relation of Climate to Plant Distribution 18

The Source of Land Evaporation 20

Movement of Air Currents 22

The Soil Factors 25

The Biotic Factors 27

Summary of Climatic, Edafhic, and Biotic Factors 30

Examples of Succession 31

PART TWO

FACTORS INFLUENCING CROP DISTRIBUTION IN THE U. S 33

PART THREE

THE CROP REGIONS OF OHIO AND THEIR SIGNIFICANCE 43

Topography and Drainage 43

The Soils 46

The Climatic Conditions 48

The Vegetation Centers 54

The Crop Centers of Ohio 56

SUMMARY AND CONCLUSIONS 69

LITERATURE CITED 73

i-07c>^3

Acknowledgments and Foreword

As in my previous paper on the Crop Centers, I am indebted
to Dr. E. N. Transeau for ecological criticism and guidance. The
idea of centers of plant and animal life about which certain forms
are naturally grouped is originally his and Dr. C. C. Adams's. Its
chief advantage, as opposed to the temperature or other "zone"
plan of mapping distribution is that it works. It should be clearly
borne in mind by the reader that boundary lines as drawn do not
attempt to mark divisions in any absolute way, but do show the
centers of distribution. For definitions of the biotic center
Adams's and Transeau's papers should be consulted. The writer
is also indebted to numerous other friends who have aided him in
one way or another, and most especially to those who corresponded
with him shortly after the publication of the Crop Centers paper.

Due to unavoidable delays in the University publications, the
date of the actual completion of the manuscript and the date of
going to press shows an interim of two years. In the meantime
a number of valuable papers of an ecological nature have appeared,
but a discussion of their bearing on the field of crop ecology must
be reserved for future work.

A. E. W.

August 24, 1920.

INTRODUCTION

The present paper is a study in one of the recent phases of
modern botany as applied to the nation's greatest commercial asset,
agriculture. The audience for which it is intended is a large one,
for the discussion is mainly directed toward farmers, albeit they
may be a special group of farmers. Some perchance are not ac-
quainted with the art of agriculture or the business side of it ; some
may never have lived on a farm ; while most of the members of this
group will be interested in the scientific aspects of plant life. The
last named constitute the special group who are to be reached by
the following series of investigations. For at this time more than
ever before in the world's history are the scientists looking in on
gatherings where business men meet. This predicates their appear-
ance at farmers' meetings. In the crowded places the man of sci-
ence learns the things most needful for human welfare. The "pure
scientist" who studies the fundamental principles and the "applied
scientist" who develops these principles can then work in harmony
for the betterment of civilization. The "pure botanist" and the
agriculturist, one of the many workers in different fields who draws
his fundamental facts from the botanist, can do team work with
benefit to each other and humanity.

The purpose of the paper is to show the relation of ecology to
agriculture and to introduce ecology to agronomists. In order to
do this the general ecology of plants must be discussed first. For
the working principles of the ecologist have been derived from
studies of the native vegetation. There is much good work in this
field which may be taken over verbatim for the use of the practicing
agronomer. There is also a good deal which may be derived from
experimental and laboratory work. Whenever it has seemed possi-
ble to the author, the accumulated facts of agriculturists have also
been grouped so that they may be of use to the ecologist in widen-
ing his principles and working generalizations, for it is believed
that the mutual assistance to be derived from such cooperation may
in some cases prove to be a revelation to plant ecologists and agri-
culturists.

A consistent and wilful attempt is made throughout the paper
to avoid the older, though still widely accepted, static ideas of the

8 PLANT SUCCESSION AND CROP PRODUCTION

distribution of vegetation. This is in agreement with the trend of
thought developing in botany in the last twenty years. A static
classification recognizes that the plants in swamps and lowland
forests are different from plants in upland forests, yet no relation
between the two is shown. A genetic classification on the contrary
would emphasize this relation: it would show the floating aquatic
herbs, grasses and sedges gradually filling the swamp with debris
until more permanent shrub thickets and young trees could find a
foothold. Later as the vegetable debris accumulates and soil is
formed, a complex swamp forest would develop. In the uplands,
from a dry rock surface covered with a tenuous coating of lichens
a denser plant cover gradually accumulates, and as soil forms, an
increase in the water content of the substratum results. In time
then, starting from bare rock a forest would develop. From the
extreme conditions, a fresh water surface, and a rock cliff, a con-
verging tendency would be noted as the development of a richer,
denser vegetation cover progressed. This change in the plant asso-
ciations as the conditions change is the keynote to plant successions.
The later plant societies and associations inherit much from the
earlier ones; not in a morphological sense of course, but in an eco-
logical sense. There were no transf erances of characteristics from
the earlier generations to the later ones. The inheritance is in the
environment; as in the human race, one civilization may inherit
something of the art, poetry, music and ideals of an earlier civiliza-
tion. The superiority of the genetic classification lies in the com-
pleteness of the picture presented.

A second advantage is in the economy of thought in placing a
group of plants in a definite relation to the whole vegetation as a
unit, instead of attempting to remember the vagaries of individual
distribution which many species often present. This is essentially
good geography as well as good ecology. We learn to associate cer-
tain groups of plants with peculiarities of locality and larger groups
with greater regions. By this process of mental association we
come to have a good understanding of a chain of perceptions which
are included in the underlying conditions of social and economic
development of a region.

The factors involved in the development of our native vegeta-
tion are climatic, edaphic, and biotic. The climatic factors deal
with the absorption and dispersal of the sun's energy and the cir-
culation of water and gases in the atmosphere. Viewed as a physical
machine the efficiency of the vegetation is not high. Due to reflec-

INTRODUCTION t

tion from the leaves during insolation only about 60% to 75% of the
total incident energy is absorbed. Of this amount a small fraction,
say 1%, is used in photosynthesis and a still smaller amount is re-
leased by respiration. The evaporation of water from the internal
surfaces of the leaves, or transpiration uses up a large amount of
the energy absorbed. Yet transpiration is by no means an unmiti-
gated evil, simply dissipating energy. Heating large quantities
of water serves the plant in much the same way that it serves an
internal combustion engine, it reduces the temperature. With liv-
ing plants the process is carried on to the evaporation of water, but
without large increase in temperature. Brown and Escombe have
shown that the leaf exposed to full sunlight is receiving energy
fast enough to raise its temperature almost 30° C. per minute. At
this rate two minutes of strong sunshine would result in the coagu-
lation of protoplasm and the instant death of the plant. Clearly
then the role of transpiration is in keeping the plant alive. Though
the efficiency of vegetation may not be high, the balance is in favor
of absorption, and this small percent of energy assimilated and
stored by green plants is the foundation upon which all the super-
structure of organic life is built.

The second, the edaphic factors include in a broad general way
the influence of soils upon plant growth. It is from the soil that
plants receive the minerals necessary for life in raw fonn. These
are built up into organic compounds in the plant and are assimilated
as food after being combined with the products of photosynthesis.
Water taken in by green plants also comes for the most part, if
not entirely, from the soil. Soil temperature and its oxygen supply-
ing power are still other factors important in the life of the plant.
The physical and chemical nature of the soil then is included in the
term edaphic.

The last, the biotic factors, include the effects of plants and ani-
mals upon the development of the vegetation. The chestnut bark
fungus has already destroyed large forests of the Allegheny Moun-
tain region and the white pine blister rust is menacing not only
the white pine forests of the east but some of our most important
timber pines of the western part of North America. Leaf eating
insects often destroy enough foliage to kill or seriously weaken
green plants. It has been stated by Professor Herbert Osbom that
grass hoppers and leaf hoppers consume as much of the vegetation
in a pasture as the cattle. Sap sucking insects are often as destruc-
tive. Rodents and grazing animals alter the aspect of vegetation.

10 PLANT SUCCESSION AND CROP PRODUCTION

Man is by far the most important of the biotic agencies in altering
the appearance of the hindscape. Earthworms, burrowing beetles,
snails and plants with tap roots favor the circulation of air in soils
and its consequent more rapid oxidation to humus. Nitrogen gath-
ering bacteria are also to be included among the favorable organ-
isms whose effect can be recorded.

In any of the broader groups of factors are a number of smaller
sets of factors. For example rainfall and humidity, (or saturation
deficit) of the air would be in the climatic group. Soil moisture and
water available for plant growth would be in the second group. In
the geographic distribution of plants the climate or the soils may
prove to be limiting factors which definitely determine areas be-
yond which certain plants are unable to advance. It is an abuse
of the word edaphic to suppose that it has reference to local condi-
tions. The effect of soils upon plant growth may be limited to
certain regions, however, since edaphic refers to the soil conditions.
The importance of the edaphic factors is often as great as the
climate group in detennining the success or the failure of certain
species.

In the crop plants a fourth set of factors ; namely, the economic
group, is fully as important in determining geographic distribution
as the other three. For in addition to being limited to regions where
soil and climate are suitable or can be controlled to a certain degree,
such economic conditions as improvement in transportation facili-
ties, increase in population, land values and intensiveness of utili-
zation of land all affect crop production. Thus we see at once the
importance of removing the discussion from all static considerations
and using genetic and dynamic ideas of the development of our agri-
culture. In the natural vegetation the changes in conditions give
rise to successions or changes in the types of vegetation. In the
crop plants conditional control gives rise to changes in type of
farming. This analogy between vegetation and crops does not refer
to rotations. In rotations an attempt is made to prevent conditions
from retrogressing. The change in the type of farming is historical
just as successions are historical.

The disappearance of plants from the vegetation as conditions
change may be referred to the operation of limiting factors. Some-
times moisture is the limiting factor, as with the desert vegeta-
tion. Or, it may be temperature as we progress northward. Two
or more limiting factors may work in combinations. With the crops
the limiting factors' may easily be from the economic group as well

INTRODUCTION 11

as from the physical group. Accordingly, depending on whether
we are interested in the problems from a botanical or an economic
aspect we are inclined to minimize the preponderating influence
of the economic or the physical factors.

Crop ecology may be viewed from two distinct angles. It is a
natural center from which the various phases of the scientific sides
of agriculture radiate. This is because the basis of crop ecology
is in plant physiology. An increase in the yield of crops is the re-
sult of changes in controlled conditions. These may be in the soil
or in the plant, and if in the latter the favorable variations are made
permanent by selection and plant breeding. If in the foraier, we
have the agronomists and plant physiologists to experiment for
certain definite ends and to explain why we arrive at certain results.

In the second place, crop ecology should be regarded as an ex-
periment in organization. It tries to show how the various aspects
of plant life, the adaptations, the growth habits, the disease resist-
ance must be unified and brought to a focus for further progress in
agriculture. Success in the future rests, not in allowing the pathol-
ogist and the geneticist and the agronomist to jog along independ-
ently, but in combining their forces. And for the business end of
fanning the economist must also be invoked so that a complete chain
stretches from the producer to the consumer. At present our agri-
culture is somewhat like a partly organized machine. All the parts
have been assembled and can be made to work separately, but for
the machine to be in smooth-running order, the operation of all
of these parts must be synchronized. Furthermore, increasing the
speed of one part of the machine, is likely to result in nothing more
than a few broken cogs and stoppage of the output, unless this
speeding can be compensated in the different parts. In a cotton
yam factory, for instance, unless all the wheels upon which the
spools turn revolve at the same rate the threads are not held at the
same tension and develop weak spots or the skein may even break
and have to be started over. The moral is that our agricultural
threads must all spin together at the tension necessary to make a
smooth, straight cord, capable of withstanding the strain of our
ever increasing population. Strange as it may seem after so many
years of our experimental stations and colleges of agriculture, the
living plant has not yet been seriously considered the logical start-
ing place about which agricultural instruction is to be grouped.

Whether or not genetic ideas may be applied to the classifica-
tion of soils remains to be proved by experiment. It seems reason-

12 PLANT SUCCESSION AND CROP PRODUCTION

able to believe that a study of the relation between soils and the
plants growing in them based on the conceptions of the develop-
ment of the vegetation would be of great benefit. There are already
studies in progress in several parts of the country on the indicator
significance of the vegetations to such practical ends as the location
of future forest sites and the possible crops yields of the future.
These investigations mark an important, if thus far only a slight,
step in the advance of learning. They indicate a new cooperation
among scientists as well as unification of the results of studies in
scientific theories and the adjustment possible between these and
human welfare.

PART I

PLANT SUCCESSIONS

The study of plant succession is an analysis of the develop-
mental process of vegetation. It is a recognition of the causes of
plant distribution. The tracing of the development and the study
of the causes have always gone hand in hand. The former leads
finally to the classification of vegetation on an ecological basis, the
latter to experimental physiology.

The broad concepts of plant distribution formulated from
time to time may be regarded as steps in the progress of ecological
development, each step bringing one closer to the complete classifi-
cation. Discovering the causes of plant succession involves changes
in methods of study, but does not necessarily alter the concepts.

The advance of the study of the causes of plant distribution
depends upon progress in the invention of new instruments, and
better ways of operating the existing ones, to measure the plant
environment ; that these two ways of examining plant distribution
have always been employed by the ecologists who have contributed
most toward the advance of the science is apparent from the liter-
ature. It is quite likely that these two methods will always be used
together.

Plant succession represents our most advanced trend of
thought in ecology. In its simplest form ecology is the observation
of plants and animals in relation to their surroundings and to one
another. The genesis of the vegetation from bare areas to highly
developed associations of plants is the basis of the examination of
successions. Ecologists taking advantage of the point of view of
successions are able to use shorthand methods for studying the
plants in the field. They thus make descriptions which are con-
cise as well as complete. By using shorthand descriptions of field
conditions and measuring these conditions carefully with the vari-
ous instruments designed for the purpose, the ecologist takes his
laboratory out into the field with him.

In most sciences, as time goes on, a broad generalization gives
way to one that is still broader, still more daring, more inclusive.

13

14 PLANT SUCCESSION AND CROP PRODUCTION

So with plant ecology, the earliest concepts of plant associations
have become enlarged and more flexible as it was found necessary
to make them more inclusive. The first ecologists perceived a rela-
tion of certain plants to dry situations and certain others to moist
ones — a most natural sort of grouping. Theophrastus (B. C. 370-
286) recognized this in the following words: "All (plants) are dis-
tinguishable as either terrestrial or aquatic, just as we primarily
distinguish animals; for there are some plants which grow no-
where but in the sea ; others affect only marshes or other very wet
places. Some cannot live in wet ground, but restrict themselves to
dry ground. Certain others are littoral only. A few trees thrive
in either moist land or dry, such are the myrtle, alder, and willow."
Except for the implication that plants are endowed with will by
the use of the word "restrict," this sounds fully as modern as any
ecological remarks could be which have been written without the
inspiration of the point of view of succession.

Plant succession has progressed in making an ecological classi-
fication understandable, because it consists essentially in a genetic
conception of vegetation. As the name indicates, succession is the
sequence of plant associations which dominate a locality as the de-
velopment of the vegetations proceeds. In the sequence each stage
is made possible because of the next or remote preceding stages. As
the term genetic suggests, one stage in the development grows out
of the preceding stages. A habitat then does not so much consist in
rocks or hills or lake, as it does in so much moisture, so many de-
grees of heat, such an amount and quality of light. A habitat is
not viewed dynamically until it is placed on a strictly factorial basis.
The field worker sees plants growing in sand along the seashore.
He must think of them in terms of the water balance of the plant,
the abundance of light, temperature, and so fortth.

Obviously, the ecologist does not attempt to control the condi-
tions of plant growth and vary them one at a time as one might
in a laboratory. The best that he can hope to do is to measure and
record the conditions he sees as carefully as his needs require. He
may even prove that succession is taking place by photographs
made at different intervals. The complete series of stages in most
successions are far beyond the space of an individual's life so his
records must be capable of interpretation by his successors. But
it is not necessary to see a complete succession in one place. One
may piece together the whole fascinating story of succession from

FACTORS AFFECTING PLANT DISTRIBUTION 16

stages at a distance from one another. It is this careful factorial
analysis of the progressive changes in the vegetation which has
been the key to the modern ecologist's ability to get ahead.

Succession, then, is only a phase of ecology, but a most impor-
tant phase. In order to have a clear notion of the relation succes-
sion bears to the general subject of ecology, a brief review of the
subdivision of the general subject seems in order.

The Orientation of the Field of Ecology

Ecology falls quite naturally into two principal subdivisions,
depending upon whether the plant responses to be studied are of in-
dividual plants or of groups of plants. This division separates
ecology into a section which is related closely to plant physiology
and a section related to plant geography, or into individual and
associational ecology. Following the names suggested by Schroeter,
these are called autecology and synecology.

A. Autecology

Autecology is the study of the responses of an individual plant
to its environment. It considers the general results of the plant
processes with respect to the life of a single plant. This is purely
a physiological study ; when carried on out of doors it becomes eco-
logical. Autecology represents to a certain extent a reaction from
studies which are of a laboratory nature purely. Nevertheless it
is in close relation to physiology which has put plant geography
into its proper place among sciences. On any other than a physio-
logical basis, plant geography is what it was in the past, pure em-
piricism. The study of the processes and the factors which deter-
mine the activities of an individual plant may be subdivided in
many different ways. A convenient way is to consider: (1) the
factors relating to changes in the growth activities of plants, (2)
the factors usually a part of the sequence of changes called "ad-
justments."

Changes in the growth activity of plants are measured by
computing variations in the water loss, variations in amount of
carbon absorbed and in the total mineral absorption. The work in
this field is of such magnitude that only the least mention of it
may be made here. The influence of water, light, salts, and their
concentrations must all be investigated and the results integrated.
As the experimental field is opened more extensively the many ad-

It PLANT SUCCESSION AND CROP PRODUCTION

ditional facts unknown or overlooked postpone the final rounding
up of the field into a completed work. This is as it should be with
any good subject. If we try to classify the experimental work in
this field we may at present say no more than that the experiments
always take one form, namely, the observation and analysis of the
factors causing an incre^ase in activity, and those which diminish
it and finally stop it entirely as limiting factors become operative.

The external and internal changes in structure may be sum-
marized as ephemeral and continuous. The former continue only
as long as the control conditions last. These affect only the most
plastic tissues and organs of the plant. The continuous variations
produce permanent effects upon the plants or upon the functioning
of the tissues and organs. In a rapidly varying stock such perma-
nent variations, no matter how induced or perpetuated, are called
mutants. This brings one to the verge of physiological ecology, the
adjoining field in this direction being genetics.

B. Synecology

Synecology deals with groups of plants and studies their de-
velopmental activity in mass. It is more geographic than physio-
logical. The mass responses are rarely, if ever, the simple sum
of the changes of activity of individuals, but more likely a ratio or
a quotient. The results of field studies of plants in mass are for
this reason different from the results of studies of individual plants.
In synecology the plant association as a whole is treated with rela-
tion to the factors of the environment which influence its develop-
ment. Studies in associational ecology are largely in the observa-
tion stage still. Accurate records, according to the strictest methods
of research, are made in several ways. The progress of the develop-
ment of the vegetation, or the plant successions, may be recorded
by means of photographs, soil and water analyses, besides various
instruments for keeping constant records of temperature and light
changes. These records, when properly put together, tell the story
of plant development in detail. The proof of plant successions,
while not at all necessary to the hypothesis, may be seen by re-
visiting reserved areas where intensive studies have been made.
After the lapse of sufficient time, the changes in the appearance of
the landscape is marked, but without the use of photographic rec-
ords is not nearly so convincing.

factors affecting plant distribution 17

The Factors in Plant Succession

The most concise grouping of the factors of plant succession
that can be made is : climatic, edaphic, and biotic.

1. Climatic Factors

In the climatic factors the air environment of the plant is
studied. There is no intention of raising the old metaphysical ques-
tion of "Where does the sky begin?", and it is not likely that the
statement will cause confusion. The air is that which begins at the
soil surface in the climatic factors and envelopes the above-ground
portions of the plant. In water plants it v/ould be whatever por-
tions are not submerged. The atmosphere contains carbon dioxide,
water, and oxygen, materials needed by the plant. In addition, the
duration and quality of light, the amount of heat, and the velocity
of wind are sources of energy for the plant. Animals or plants af-
fecting the above-ground portions of plants are grouped among the
biotic factors. The processes of absorption and distribution of mate-
rials and energy taken in and released by plant activity have no
place in this discussion, rightly belonging to a text on physiology or
experimental ecology.

From our viewpoint of the development of the vegetation,
extremes of temperatures are the most important factors in lim-
iting plant grov/th ; for the extremes, and not the means, determine
which species may become a part of the vegetation and which may
be killed from too great cold or too intense heat. Once species be-
come established, the mean temperatures are important because
they determine the average rate at which plant activities proceed.
The rate may double or treble within certain narrow limits for each
rise of ten degrees Centigrade, but Blackman ('05j and Blackman
and Tansley ('05) have shown that beyond a set limit further rises
do not accelerate growth. To regard temperature means as any-
thing more than a condition for photosynthesis is to put too much
weight on the wrong factor.

What has been said for temperature applies largely to light
also. The minimum and maximum amounts of light in which a
species may develop are the important factors in the distribution of
plants. As with the temperature light intensity, varies with the
season, the altitude, and the latitude. While some plants are active
photo-synthetically at 2° C, their common range is from 20 to
perhaps 40 or 45° C. Light less intense than full sunlight is sufR-

18 PLANT SUCCESSION AND CROP PRODUCTION

cient for growth so that as with temperature, light is not of su-
preme importance in plant distribution. There are few if any
places upon the surface of the earth where the light and tempera-
ture requirements of plants are not satisfied at least during some
season of the year. Moisture, therefore, remains the important
factor in detennining plant distribution.

The importance of water as compared with light and tempera-
ture is easily shown. Our climatic zones, torrid, temperate, and arc-
tic, are east and west in their bearing, and one crosses them in a
journey from the equator to either pole. Desert and arid regions
are by no means restricted to any particular climatic zone. Desert
and arid regions are the extreme, but we may have dry, grassy
plains extending far northward beyond the tree formations. Look-
ing at it another way, we can see that water is irregularly distrib-
uted on the earth's surface, while temperature and especially light
tend to be somewhat regularly distributed. The water is the un-
balanced factor and is therefore the limiting factor. It is the unequal
distribution of water, both in amount and during a given period
of time, which is the cause of our distribution of various types of
vegetation. In order to fully understand this, the variations of cli-
mate should be examined in detail.

The Relation of Climate to Plant Distribution

Although the sun's rays strike the different parts of the earth's
surface in about equal amounts, yet the total energy derived from
them is quite unlike in different regions. What then happens to
prevent equal distribution of energy?

In the first place, the land surfaces and the water surfaces
absorb heat at different rates. If we call the specific heat of the
water surface 1, then the specific heat of the land surface is ap-
proximately 4, for the land surface takes up and again gives oflf
heat about four times as fast as the water. Large land masses,
e.g., continents, have dry regions toward their centers where the
summer temperatures are extremely high and the winter tempera-
tures extremely low. The day and night temperatures also fluctu-
ate greatly. The loss of water from the centers of continents by
evaporation tends to intensify the variability of the climate. The
sea surface, on the other hand, or a small island in the center of
the ocean, has, at sea level, an equable climate in which the sum-
mer extremes and the winter extremes are much closer together

FACTORS AFFECTING PLANT DISTRIBUTION 19

than in an interior region. In the second place, elevation above sea
level produces a local climatic effect in some ways like the climate
of the central portions of continents. The sunshine intensity is
great, and the water loss rapid. On the windward side of the
mountain range, however, the precipitation is heavy, since the air
containing moisture deposits its load as it rises and cools in pass-
ing over the summits. The influence of the mountains in catching
water is felt in all the territory on the windward side between
them and the ocean, even in essentially dry regions, since they con-
tribute to stream flow.

More important as reservoirs of water than the oceans even
are the land masses. It is not difficult to see that if an air current
loaded with moisture from an ocean reservoir reached a land area
and deposited some of this water, the air current would become
rapidly dry as it passed over the land. Very little moisture would,
under these conditions, ever be transported inland for any great
distance. An examination, however, of the continents of the earth
shows that a good deal of water falls on the land at some distance
from oceans, leading up to the obvious conclusion that a current of
air is picking up water vapor and precipitating water all the time
as it passes over a continent. The amount of water evaporated
from oceans and evaporated from the land has been compared.
Brueckner has calculated that the land supplies from its own area
seven-ninths of the precipitation which falls upon it. This means
that the land is a much more abundant source of the moisture car-
ried by winds than the oceans are. A current of air moving over
the land and precipitating moisture would be continually having
more moisture added to it, a re-enforcement of the supply so to
speak, from the evaporation of water from the land surface.

Zon has constructed a balance sheet showing the circulation of
water on the earth's surface. The study of Zon's figures lead to
the following conclusions: (a) that the bulk of the water evapor-
ated from the oceans is reprecipitated into the oceans, (b) the bulk
of the water evoparated from the land is reprecipitated on land,
that the precipitation falling upon land is nearly all (four-fifths)
furnished by the land area. The examination of Table 1 explains
these statements in statistical form.

20 PLANT SUCCESSION AND CROP PRODUCTION

Table 1^

CIRCULATION OF WATER ON THE EARTH'S SURFACE

Cubic Miles

Volume of ocean vapor escaping to the land.
Continental vapor over the land

Total volume of vapor from which land precipitation is derived

5,997
20,870

26,868

The present discussion is not concerned with the amount of
precipitation into the oceans. The precipitation and evaporation of
closed basins in the interior of continents is regarded as equal and
therefore omitted. The volume of ocean vapor escaping to the land,
5,997 cubic miles, is 7 percent of all the water evaporated from the
oceans. The volume of continental vapor furnishes 98 percent of
the continental precipitation.

The Source of Land Evaporation

Evaporation is a surface phenomenon. A surface which is
rough and which absorbs heat will give off vapor more rapidly than
one which reflects heat. Therefore, with equal insolation and equal
wind velocity a bare surface of moist soil will give off more water
per unit of time than will a water surface. This will continue dur-
ing a warm season as long as water rises through soil pore spaces
to resupply evaporation. A soil surface with only dead vegetation
as a cover does not evaporate as much moisture as a bare soil. A
soil area with a living cover of vegetation, however, evaporates
much more rapidly. Every living plant has an uninterrupted stream
of water passing through it. In the case of the flowering plants
with the leaves borne on elongated stems some distance above the
soil, there is a complicated mechanical structure and a series of
interrelated physical processes by which water is absorbed and
lifted to the heights of the tallest trees. Plant communities are
composed of individuals of different water requirements and capa-
ble of absorbing water from different soil levels. In the most highly
developed plant communities, the forests, evaporation as well as
absorption is taking place at different levels. For example, there
is a certain amount of evaporation from the ground cover vegeta-

* The relation between continental vapor and continental precipitation.

FACTORS AFFECTING PLANT DISTRIBUTION 21

tion, a certain amount from the shrubs and short vines taller than
the plants forming the ground cover, and a still greater amount
from the trees and large lianas with their crowns exposed to full
sunlight and the more rapidly moving air currents found at this
distance above the soil. The forests are for this reason, therefore,
the greatest dessicators of the soil. Next in order of amount of
water evaporated would doubtless be a tall-growing cultivated crop,
corn, tobacco, sorghum, sunflowers, or castor beans, for example.
The evaporation would be increased if the weeds were allowed to
grow beneath these crops or if, as is commonly practiced, another
crop, a legume for example, were seeded in the field when tillage
ceased.

The part that forests play in the control of climate, especially
in the amount of rainfall in the regions near great forests, has
long claimed the attention of intelligent observers. The influence
of mountains upon precipitation, as set forth in the preceding sec-
tion of this paper, is markedly increased if the mountains are
clothed with a forest cover. The effect of the forest upon local pre-
cipitation may not be very great, but its influence is noticed in drier
regions in the paths of winds coming from over forested lands.
Hamberg says of the forests of Sweden : "The excess of evaporation
which the forest vegetation furnishes to the atmosphere above what
the same area would furnish if it were covered with herbaceous
vegetation merely, must of course be very considerable. If this
aqueous vapor were received in the forest and returned to the land
in the form of rain it would be extremely beneficial. But winds carry
it off and spread it in all directions with such rapidity that its bene-
ficial influence for our country (Sweden) remains very doubtful."
The cultivated lands in Sweden, especially its dairy farms, obtain
the benefit of the moisture evaporated from the forests and conti-
nental countries east of Sweden also feel its beneficial influence,
since they are in the paths of the winds blowing over Swedish
forests. In the United States the Ohio Valley receives the benefit
of the Appalachian forests when the winds are from the south.
Much of the increased moisture of the prairie region of the central
states over that of the plains states farther westward must also
come from this source. The digest of the present writer's opinion
on this point as given in a previous paper may be summarized as
follows: (a) The coincidence of precipitation in the United States
and prevailing southerly winds, (b) the amount of evaporation

22 PLANT SUCCESSION AND CROP PRODUCTION

from a land surface as compared with a water surface, and (c) the
greater efficiency of a vegetative cover, especially a forest, as an
evaporating surface when compared with a water surface or a bare
soil surface.

Movements of Air Currents

One of the most fundamentally important set of facts in
aerography deals with temperature and pressure changes by which
currents of air are moved horizontally and vertically over the
earth's surface. We know that at sea level air is more compressed
than on the tops of mountains, and we consequently obtain baro-
metric registers of greater pressure at lower altitudes than at
higher ones. By simple gravity air tends to collect right at the sur-
face and air particles are here crowded and compacted. Higher
up the air particles are farther and farther apart, and finally we
may get to a region where air no longer exists.

Above the polar regions of the earth the air is less heated than
above the equatorial region. Warm air rises and expands, while
cool air tends to settle. There is a general tendency then of air to
move inward from the polar regions toward the equator. This ten-
dency is considerably offset by another factor, however, the mat-
ter of the unequal heating of land and water masses. The difference
in the rate of heating was touched on in the previous section. The
air over a land mass in summertime will become warm and
ascend much more quickly than the air over a mass of water. In
winter the air over a body of water is likely to have the higher tem-
perature. With the changes of season there come to be established
permanent areas of high or low temperature. The high-temperature
areas of ascending air are areas of low barometric pressure. The
low-temperature areas may be regarded as areas of high barometric
pressure. Simple convection movements and tendency to stabiliza-
tion and equilibrium would lead to horizontal movements as well
as the vertical ones of the rising and descending columns of air.

The centers of action have come to be regarded by meteorolo-
gists as the essential factors in the control of climate. Buchan
many years ago prepared maps of winds, temperatures, and pres-
sures at sea level for practically the entire globe. It was Teisserenc
de Bort at the International Meteorological Conference held in Chi-
cago in 1893 who called special attention to the controlling influ-
ence which the centers of high and low pressure exerted upon cir-
culation. He had named them more than ten years previously "the

FACTORS AFFECTING PLANT DISTRIBUTION

23

grand centers of action" of the atmosphere. They are understood
to be closed areas of high and low pressure, or hyperbars and in-
frabars as they are commonly called, which have a certain perma-
nence in a given season and give the leading features to the gen-
eral circulation. In fact, the flow between these centers exerts the
dominating influence on the circulation of the entire atmosphere.

Fio. 1. Chart showing the grand centers of climatic control. After Buchan. See also
Adams's, "An Ecological Study of Prairie and Forest Invertebrates." Ills. Bull. Nat. Hist, 9 :70.

The centers of action come to have a motion of their own, due
to the earth's rotation. In the northern hemisphere the cyclones or
columns of ascending air have a counter-clockwise rotation. In the
anticyclones or descending air streams the motion is clockwise. In
the southern hemisphere the rotary motion of the cyclones and anti-
cyclones is just the opposite of the motion in the northern hemis-
phere.

The accompanying diagram (Figure 1), modified from Bu-
chan, shows the position of the permanent centers of action which
exert a controlling influence over the summer climate of North

24 PLANT SUCCESSION AND CROP PRODUCTION

America. The hyperbars or anticyclones are marked "high" and
the cyclones or infrabars "low." The arrows indicate the direc-
tion of rotation of the air flowing into or away from centers of ac-
tion.

In midsummer there is a large area of low pressure over the
central part of the North American continent. On the surface of
the earth it is warmer east of a low-pressure area, because the
winds blowing spirally, counter-clockwise, inward toward the low
are coming from the south, which is usually warmer. Mr. J. War-
ren Smith of the United States Weather Bureau, in some private
correspondence, has kindly pointed out the two laws which are
operating :

1. The pressure controls the surface winds.

2. The surface wind controls the temperature.

The converging air is warm at the surface and remains so un-
til it ascends, when it expands and cooling adiabatically, precipi-
tates its moisture. It is to the east of the high that the warm
weather and sometimes dry weather exists. The amount of rain-
fall would depend on the rapidity of the cooling and the total water
vapor content of the inrushing air. As far as vegetation is con-
cerned, though there might be rainfall, the final effect of the east-
ward migration of the low would be unfavorable, since in summer
the drying effect of the warm air at the surface would not be bal-
anced by the scattering showers.

Another shifting in the position of a great center of action
which would be even more unfavorable in its effect on the vegeta-
tion of eastern United States is the westward migration of the At-
lantic high shown in the diagram. Where the air is descending it
is being warmed adiabatically as it reaches the surface of the earth
and is taking up moisture. This air would then have a drying ef-
fect on the vegetation and the crops, and since it would be accom-
panied by clear skies the water loss from living plants would be ex-
tremely rapid. There would be no compensating showers brought
in by this type of distribution of the centers, and if the positions
were assumed for any considerable length of time the ensuing
drouth would be followed by a failure of the plants to maintain a
water balance. Wilting and even death would be the effect of a
protracted drouth. Besides the continental low and the Atlantic
high, there are three other region circulation centers, all of which

FACTORS AFFECTING PLANT DISTRIBUTION 25

have an effect on the climate of North America in summer. Their
action is indicated in the diagram.

Thus the interplay of air currents plowing into and out of the
grand centers of action can be seen to influence greatly all the liv-
ing vegetation. Wind, from the standpoint of plants, is a moisture-
temperature-relation factor. Increased wind velocity and increased
temperatures both accelerate transpiration. In full sunlight the
cooling effect of transpiration is the greatest possible benefit to the
plant in preventing coagulation of protoplasm. Rapid transpiration
probably also aids the plant greatly in the transfer of minerals
after absorption from the soil. But rapid transpiration in the ab-
sence of equally rapid water absorption is undoubtedly a constant
menace to the life and rapid growth of plants.

2. Soil Factors

In dealing with the soil factors which influence plant succes-
sion, the only measure which we may use for comparing different
soils is plant growth. Obviously, it would be incorrect to talk of
"fertile soils" or "barren soils" unless we had the climate as well as
the soil expressed in some way. We cannot say that a soil will or
will not support a dense cover of vegetation if we consider the soil
simply inert mineral material or if we base our notion of produc-
tivity on the physical structure of the soil alone, or upon the chemi-
cal nature of the soil alone. The temperature and the moisture must
both be included in our notion of soils. In the arid southwestern
regions of the United States the soils contain salts in more than
the amounts required for plant growth and the temperatures are
high enough to support a subtropical vegetation. Water is, how-
ever, the limiting factor. In the sandy barrens of southeastern
United States, the rainfall is high, the temperature high, and the
growing season long, but mineral salts and available water seem
to be the limiting factors.

The mineral portions of soils formed under arid or humid con-
ditions are entirely different. In arid regions the mineral parts of
the soil are formed through mechanical processes of weathering or
by disintegration. Soluble materials are found in abundance in the
soils of arid regions. In humid regions the mineral portion of the
soil is the insoluble or only sparingly soluble material, since the
most soluble portions have been carried off in the surface streams
and ground water. The mineral portion of the soil in a humid re-

26 PLANT SUCCESSION AND CROP PRODUCTION

gion represents a chemical residue, and like the residue on a filter
paper, it is frequently washed clean.

Plants need such small amounts of soluble salts for their de-
velopment that the sui-prise is not that they are able to secure these
raw materials in most soils, but that there may be found soils in a
humid region which do not support abundant plant growth. The
pine barrens are apparently an example of this. If a plant cover suf-
ficient to accumulate salts, especially nitrates, in excess of what is
carried away in solution and by oxidation, could be started on these
barrens, there is little doubt but that a rapid cycle of succession
would be initiated.

The mineral portion of a soil is also of importance ecologi-
cally because of the fineness of the particles and the nature of their
arrangement. These properties are known as the texture and struc-
ture of the soil, respectively. The former is a relatively perma-
nent property of the soil, that is, the size of the particles is not
materially reduced in a short time. Certainly, cultivation and till-
age produce no alteration in the size of the soil particles. The tech-
nical classification of the soils has been made largely on the basis
of the texture. The structure of soils, the arrangement of the par-
ticles, is undergoing constant change. Frost, rain, plant roots, and
burrowing animals are a few of the agencies which effect a change
in the structure of soils.

The humus portion of the soil is rich in colloids, which are
highly retentive of water. For this reason humus soils, or soils in
which the humus portion predominates over the mineral portion,
are proverbially productive soils. The old evolutionary idea, "all
life from pre-existing life," may be translated to the environment
when we speak of humus soils, for a soil full of humus contains the
accumulated remains of previous generations of plants, and the
future generations have this as their heritage- The humus furnishes
the energy to bacteria, which in turn leave a newly molded form
of energy for green plants.

The nitrifying bacteria do not add to the total soil nitrogen,
however. They are unable to use free nitrogen and live solely upon
dead organic material, converting the nitrogen into a form useful
for the green plants. Some soil bacteria can draw on the free nitro-
gen supply, but the nitrogen thus accumulated must be converted
into organic nitrogen compounds before it is available to green
plants. This is discussed in the following section on the biotic
factors.

FACTORS AFFECTING PLANT DISTRIBUTION 27

The most important chemical fact about humus soils is that
they are, under certain conditions, capable of supplying organic
substances to growing plants. In addition to this, in humid regions,
soils with a high organic content also have a high mineral content,
since the growth of plants tends to prevent the normal amount of
leaching which otherwise would take place. The prairie soils of
North America and the chernoziom (black earth) of Russia are
rich in both organic and soluble salts. If the color can be used as a
guide to the lime content, (Coffey '09), then the order in which the
soils of the United States rank is (1) the prairies, (2) the forests
of eastern America. This accumulation of mineral salts in the soil
is in agreement with the distribution of total rainfall throughout
the year. It is greater in the forests and less in the prairies. In the
prairies there has not been enough rainfall, or its distribution has
not been such as to leach the lime from the soils at the rate that this
is occuring in the light forest soils. Yet the rainfall in the prairies
has been sufficient to induce a heavy growth of vegetation, which is
only partly decomposed. This is because water standing during a
portion of the year in prairie sloughs prevented as complete oxida-
tion of the organic material as occurs in forests. The vegetation
acted as a series of dams in a country of rolling topography made
level by glacial action. These lakes or water-bottomed sloughs
kept the forests out until man hastened the gradual drainage proc-
ess. Thus we can see how climate and topography acting in unison
formed soils in the east north-central states which are entirely
different from the soils of the forested regions, though in many
instances they have been derived from similar geological for-
mation.

3. Biotic Factors

The influences of plants and animals upon the developing vege-
tation are known as the biotic factors. These are assigned various
degrees of importance by different authors. Clements ('05) classi-
fied habitat factors into physical and biotic and ('16) he consist-
ently eliminated an edaphic group while admitting its convenience.
It is true that edaphic factors may be further resolved into topogra-
phic, or physiographic, yet this does not detract from the import-
ance of having all the subterranean plant environment in a single
group. If the resolution be carried out far enough, the last result
will be something like Shreve's ('16), in which all the factors are
physical. Cowles ('01, '11) has carefully distinguished the biotic

28 PLANT SUCCESSION AND CROP PRODUCTION

factors and presents them in their true role of a source of the in-
fluences separate from the climatic or edaphic influences. The im-
portance of biotic factors is seen nowhere so well as in the forma-
tion of soils, which in the majority of cases are due to the action
of plants.

Among the various biotic factors the bacteria are of prime im-
portance, especially the bacteria of the Nitrogen Cycle.

The first group are saprophytic, that is, they live upon plant
and animal residues after the death of the individual. Their reac-
tions reduce the plant and animal proteins to ammonia, hence
the process is known as ammonification. The chief micro-organisms
are Bacillus subtilis and B. mycoides. Ammonification is followed
by rapid decay of the plant or animal residue. The ammonia remain-
ing in the soil is commonly ammonium carbonate (NHOiCOa. De-
cay is followed by nitrification, an oxidation process carried on by
the Nitrosococcus and Nitrosomonas bacteria. The ammonia or am-
monium salts are oxidized to nitrites of the composition (R) NO2.
Further oxidation carried on by the Nitrobacter changes the
nitrites, (R) NOa to nitrates, (R) NO3.

The nitrates are useful for green plants and with the excep-
tion of some of the ammonium compounds, are the only fomi in
which nitrogen can be absorbed by most green plants. At this stage
denitrification by bacteria of the denitrifying group may liberate
the nitrogen of nitrates into the free nitrogen of the air. The pres-
ence of these organisms is unfavorable to the growth of green
plants therefore.

The completion of the nitrogen cycle is found in one direction
by the building up of nitrates in the body of green plants into, first,
the amino-acids, then the plant proteins, and finally animals sub-
sisting on the plants build up the amino acids and proteins of plants
into their own protoplasm. The cycle begins again with the death
of animals and plants.

Free nitrogen of the air may under some conditions be fixed
by groups of soil bacteria which derive their energy from carbon-
material found in the soil or by living somewhat parasitically on
green plants- Azotobacter and Clostridium sp. are the chief of
these organisms. The former requires the presence of abundant
oxygen and so works only close to the surface of the soil, while the
organisms of the Bacillus radicicola group upon living roots of leg-
umes, furnish an example of another kind of organism capable

FACTORS AFFECTING PLANT DISTRIBUTION 29

of extracting free nitrogen from the air. The bacteria are para-
sitic upon the legume which furnishes food in the form of com-
pounds of carbon of its own manufacture. As the tubercles pro-
duced by the bacteria grow older, the appearance of the bacteria
themselves is altered. They become larger, sometimes branching,
and in this form are known as "bacteroids." Active nitrogen assimi-
lation by the green plant coincides with the appearance of the bac-
teroids in the root nodules of the legume. If a large enough portion
of the legume is then allowed to remain in the soil to offset nitrate
nitrogen absorbed by the plant, there results a corresponding gain
in soil nitrogen.

The reciprocal symbiosis of Phoma an endotrophic mycorhiza
should also be mentioned as a relation which nets a gain in the nitro-
gen supply for the host plant upon which the fungus lives. The
mycorhiza as a class are so important to many of the green plants
that the latter are unable to grow except in the presence of the
fungi.

Protozoa are also important, though mainly unfavorable, as
they destroy the beneficial bacteria. Brown ('16) has described the
importance of mold action and in addition there are other fungi —
all the saprophytic ascomycetes and basidiomycetes.

The white pine blister rust and the chestnut blight are exam-
ples of biotic factors which cause certain plants to drop out of the
native vegetation as surely as changing climatic or soil conditions
cause them to disappear. Chestnut trees in New York and Pennsyl-
vania have already been killed in such numbers as to alter entirely
the nature of some of our finest forests. If the disease goes on un-
checked it would not be strange to have inhabitants of these states
inquiring in a hundred years from now if the chestnut actually
grew in these portions of Eastern America. And yet the chestnut
bark disease was noted as a menace on Long Island for the first
time about the year 1905.

The white pine blister rust, as it has been named, has not yet
done any considerable damage and it looks as though this disease
will be checked, thanks to the efficient service of our forest patholo-
gists. Yet in those small localities which were infected the white
pine was completely destroyed. This disease is not only a menace
to the white pine of Eastern United States, but likewise attacks the
western yellow pine, another of our valuable timber woods.

30 PLANT SUCCESSION AND CROP PRODUCTION

Among all the chlorophyll-bearing plants there is competition
for light as well as competition for moisture and nutrient mate-
rials in the soil. Thus, we see that the influence of the green plants
themselves upon the vegetation must be greater than the influence
of the non-chlorophyll-bearing plants, since there is active compe-
tition going on among the members of an association in addition to
the action of the micro-organisms- A plant association cannot be
regarded as completely closed until all the levels for abstracting
water, minerals, light, and air are filled with sets of species of
dissimilar habits and requirements.

The animals are as important in the mixing of soil materials
as are plant roots. The importance of earthworms has been known
since Darwin's classic work on the subject. Snails, ants, beetles,
spiders, rodents, all contribute their quota toward mixing the min-
erals with vegetable mould and allowing air and water into the
substratum. Insects are important in cross pollinating plants and
in many species are essential to seed production. Insects may also
act injuriously in destroying plants and may even effect complete
destruction of a pure stand. The locust borer, to name only one ex-
ample, has almost eliminated the black locust from farm wood lots
and forests of the central states where it was long the favorite wood
for fence posts. Birds are agents in the dispersal of seeds and
spores. Rodents, rabbits, rats, and mice may destroy trees by prun-
ing the bark, and prairie dogs destroy grasses. Sheep and cattle
have been known to prevent the reproduction of some of the timber
trees in the grazing region of the National Forests of the Southwest
and West (Hill, '17), while the bison has been credited as being
one of the agents to delay the invasion of forest upon the plains.
Of all the animals, the destruction by man has been the greatest.
There are almost no virgin forests left in the United States, due
to man's activity.

4. Summary of Climatic, Edaphic, and Biotic Factors

It will doubtless have occurred to the reader that any classifi-
cation of factors of the environment will present certain difficul-
ties in the way of sharp distinctions between the subjects to be clas-
sified. The attempt made by the writer shows that the biotic fac-
tors cannot be escaped in talking of the other two sets, viz., in the
climatic factors the influences of forests upon climate are featured,
while the relations of soils and the micro-organisms are discussed

FACTORS AFFECTING PLANT DISTRIBUTION , 31

under the edaphic factors. The climate and the soil are distinct
enough in themselves ; the difficulty of classification lies in the de-
gree of modification which they undergo in reactions with each other
and with the organic universe. For the present discussion the writer
believes that he has carried the resolution of factors far enough.
More rigid separation would destroy the continuity of the story of
the facts in relation to one another.

5. Examples of Succession

Now that the factors contributing to succession have been thus
briefly reviewed, some examples of successions which show how the
vegetation gradually builds up soils and alters conditions for plant
growth, should be included. For this reason two extreme areas
have been chosen in order that the effect of plant growth in
each case may be brought out. The two areas are a swamp and a
dry rock surface. The effect of the changing conditions induced by
the vegetation can be noted in the change in plant population shown
in the following diagrams.

In the swamp series the open water surface is partly covered
by floating aquatics which gradually deposit debris on the bottom
of the swamp. This material slowly decomposes into the soil, which
in time reaches near the surface. Here and at the shallower mar-
gins, rushes and sedges enter and occupy the soil until the shrubs
typical of a button bush swamp, Cephalanthus, Rosa Carolina, and
Alnus rugosa, enter. These are succeeded by a willow stage, a red
maple stage, a swamp oak stage, and finally an oak-hickory forest,
in which beech and hard maple gradually appear. There has been
a tendency toward drier conditions continually during this succes-
sion. The swamp gradually becomes filled and drained as the vege-
tation accumulates. The last stage of the swamp is a forest, with
all but a few undrained patches occupied by a beech-maple forest.
Wherever the conditions remained but slightly changed by the vege-
tation, the vegetation is itself much as it was formerly. There is,
in other words, reaction between the vegetation and the environ-
ment.

In the cliff series we start with bare rocks on which only
lichens grow. The action of these plants is to decompose slightly
the rock surface and to add their own remains to the finely parted
mineral material. Some of this soil sifts into crevices and here the
action of the larger plants becomes effective in widening and deep-

32 PLANT SUCCESSION AND CROP PRODUCTION

ening the crevices. By the time a heath stage has been reached the
cliff is usually well covered. This stage is succeeded by a shrub stage
and often by a coniferous stage. Gradually oaks come in, increas-
ing the shade and lowering the water loss from the soil as well as
the oxidation rate of humus. The oaks are succeeded in time by
more mesophytic trees — beech and maple, which are again the
culmination of the successions. In all of this series the action of
the plants has been toward an increase in soil and moisture until
the conditions became suitable for plants like beech and maple.

These successions teach the lesson of soil foimation and bring
out the importance of the biotic factor in soil building. They also
show the importance of the genetic conception and the inadequacy
of a static or even a merely dynamic system of classification, for
the plants become a cause of subsequent change. Successful inva-
sions are of course in the beginning the effect of certain conditions
of the bare area into which they migrate. Chance is the sole cri-
terion of the original seed or spore introduction, but the life of the
seedling after introduction depends upon its inherent ability to
meet the conditions of the environment.

PART II

FACTORS INFLUENCING CROP DISTRIBUTION
IN THE UNITED STATES.^

That the crop plants are bound by the same laws of physiology
as other plants is an obvious truism. They respond in the same way
to changes in the environment. They become adjusted to the condi-
tions which they encounter. From the point of view of the crop
grower, this response is indicated by an increased yield. There are
well known physiological strains and races of cultivated plants just
as clearly distinct as morphological races. Examples are: Sixty
Day Oats, rust-proof asparagus and anthracnose resistant varieties
of beans.

It is important to determine how far the analysis of the rela-
tionship of the plant to its environment can be carried in the crop
plants. Are the methods of study used in ecology useful here?
Can a relationship be established between plants under cultural
conditions and the natural vegetation? The study of the indicator
significance of the natural vegetation is just beginning, and offers
to lead the way to possible future crop production. It has been
applied to cropping in the Great Plains by Shantz (1911), Kearney
(1914) , and to locating forest sites by Korstian (1917) , and others.
The results indicate how much can be done by the intelligent appli-
cation of the methods for studying plant associations to problems
of culture. It also seems possible that very slowly a scheme of eco-
logical equivalents might be worked out. For example the state-
ment is generally accepted that where sassafrass grows peaches
can be successfully produced. This statement is misleading. For
sassafras can be found growing under a great diversity of condi-
tions, and there are many varieties of peaches. It is useless to
spend much time in looking for individual ecological equivalents,
unless they can be grown under controlled or at least measurable
conditions.

In the present discussion an attempt is made to indicate some
of the relationships between great plant formations and certain crop
centers. The studies are, entirely, generalizations. Only the broad-

1 Presented at the Pittsburgh meeting of the Ecological Society of America, Jan., 1918.

33

34 PLANT SUCCESSION AND CROP PRODUCTION

est groups of factors limiting plant distribution can be discussed
in such a study. The climatic, the edaphic, and biotic factors are
given a brief treatment with respect to the endemic vegetation.
Later for the crop studies, a fourth group of factors is added. The
rainfall-evaporation ratio, (Fig. 2) successfully employed by Tran-
seau ('05) in delimiting the forest centers, has been used as a basis
for this study. This was secured by dividing the total rainfall for
a given station by the evaporation obtained from Russell's (1888)
data on evaporation.

The centers of vegetation of North America are as strongly
differentiated in the United States by the common crop plants as by
the native plants of the forest centers. Timothy, spring wheat, rye,
buckwheat, and potatoes occupy the same region as is dominated by
white pine, spruce, hemlock, balsam fir and white birch — in other
words the northeastern evergreen forest. The region occupied by
corn, winter wheat, oats, red clover and beans is related to both
the central deciduous forest and the prairies. This emphasizes the
importance of edaphic factors in plant successions and the relation
of the crop to edaphic conditions.

For although the grain belt extends eastward into Ohio, it
does not reach far from the edaphic prairies. Tobacco occupies
a median position between the central deciduous forest and the
southeastern mixed forest. Cotton, yams, cowpeas, and peanuts
center in the southeast-

The criteria which have been applied in delimiting the forest
centers hold for the crop centers as well. There is first of all
dominance. The evidence that one is approaching the center for
a given crop is the number of farms upon which it is being grown.
In this connection it is interesting to note that while central Illinois
is for very special reasons, the center of production of corn, yet
in point of acreage devoted to it in proportion to cultivated lands,
com is the most important crop of southeastern Kentucky. No
hills seem too steep or too high for the farmers to attempt to grow
a corn crop. Compared with production in Illinois, the results on
these hills seem far from encouraging. The production and total
acreage can be used in determining this center. (Fig. 3) .

In the natural vegetation next to dominance come maximum
size for the species, greatest differentiation of type and widest
range of habitat as criteria of the biological centers. These are all
corollaries of general well being, the result of the limiting factors
being fewer and less effective. In the crop plants we can see that

FACTORS AFFECTING CROP DISTRIBUTION

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36 PLANT SUCCESSION AND CROP PRODUCTION

in the centers even the rough, hilly land produces a fair yield.
Then it will be noticed that more varieties of a given plant are
known. For example it is at the Cornell Station that work in select-
ing and improving timothy can best be carried on, because of the
ready access to timothy variations. At the Minnesota station the
collection of wheat varieties and improved strains of wheat is very
large. The same is true for corn at the Ohio, Nebraska, and Illi-
nois Stations.

There is another analogy still to be drawn. In the endemic
vegetation the center of distribution, that is, where a species domi-
nates, is not necessarily the center of dispersal, the place from
which the species is spreading. Rather it is implied that in the
center the limiting factors are fewest, and least effective. As one
recedes from a center the limiting factors increase in number and
in intensity. In the crop plants it can be shown that the regions of
greatest yield per acre — which correspond to the centers of dis-
persal of the vegetation — are frequently separated from the regions
of maximum production. For instance in the case of wheat, the
yields are higher in the humid section where the rainfall is eight-
tenths or more of the evaporation called for. Yet the maximum
production of wheat centers in the region where the rainfall is only
six-tenths or less of the evaporation called for. An attempt to cor-
relate crop centers and vegetation centers considering only the
climatic and edaphic factors would present many strange anomalies.
These explanations alone would not support the facts of the dis-
tribution. It is necessary to go outside the field of physiology to
discover the basis of crop distribution.

The fundamental difference in the occurrence of plants belong-
ing to the natural vegetation and the crop plants lies in culture.
In the vegetation invaders from another center are frequently re-
stricted to one habitat, often a poor one. Arbor vitae in central
Ohio is confined to the rock terraces of stream gorges and to bogs.
The white pine and the scrub pine meet on rock cliffs east of
the glacial boundary. On Lake Michigan sand dunes the jack Pine
and the cactus meet. Yucca extends northward along the sand plains
of the Atlantic seaboard. In the better habitats competition with
the plants belonging to the center would be too keen for the in-
vaders. With the crop plants the case is almost the reverse. When
they are beyond their climatic optima they are generally to be
found on the richest lands of the farms. In New York and eastern

FACTORS AFFECTING CROP DISTRIBUTION

87

38 PLANT SUCCESSION AND CROP PRODUCTION

Pennsylvania only the best fields are ever used for growing com.
These are reinforced and amended by a liberal use of manures.
This coddling is carried out to a greater degree in the Connecticut
River Valley where tobacco is grown. Not only are the soils treated,
but the plants are sheltered under cloth. This cuts down the tran-
spiration rate during the day and at night prevents loss of heat.
The climate thus produced is more like that of the center of the
tobacco industry.

With the crop plants then, climatic optimum is not the factor
which determines the center. The soil conditions are not always the
controlling factor. It is the profits.

It is profit which causes the potato crop to center, (Fig. 4)
near each of the thirty largest cities of the United States without
much indication of climatic or soil preferences. It is profit which
links the corn belt with the center of oats production, though the
former is pushed upward from the south and the latter down from
Canada. Profits makes New York and New England a large
meadow of imported cultivated grasses, while the native prairies
and plains grasses only come to market if pastured.

An economist attempting to minimize what he regards as an
undue preponderance of the physical factors would explain these
distributions on the theory of rent. He would imagine a hypotheti-
cal state. This state would be circular in outline and present no
differences in climate, topography or soils. All transportation prob-
lems that existed would be equally distributed over the state. Under
such conditions, the state would be divided into many concentric
zones. Around the city would be truck gardens ; next to these, a
dairying community; next, grain farms; and in the outmost circle
pasturing would be the chief agricultural endeavor. (Fig. 5). The
explanation of the zonation of this unusual state would be that the
grain farmer, making more profit than the shepherd, could afford
to pay more rent than the latter and so live closer to the city and
his market. The dairyman's rent would be higher than the grain
farmer's, and so on into the city- The economist has a good case
and there is no way of circumventing his argument. We see ex-
amples of the working out of this hypothesis on every side.

Now the truth of the matter of crop production and the cen-
tering of crops in certain localities lies somewhere between the
geographic considerations of climate and soils and the purely hypo-
thetical proposition of the economists. They cannot escape, under

FACTORS AFFECTING CROP DISTRIBUTION

n

40 PLANT SUCCESSION AND CROP PRODUCTION

actual conditions, the influence of soils and climate. The factors
are like the legs of a three-legged stool.

The economist can never avoid the fact that it is sometimes
the edaphic group and sometimes the climatic group of factors
which stand back of this very profit he is studying. Climatic

Fig. 6. Zones of production on a purely hypothetical economic basis.

conditions determine the physiological limits of the cotton crop.
(Fig. 6). It is the climatic conditions and not the economic only
that determines the dominance of cotton. Corn is not and never
can be a serious competitor of cotton. In the case of spring wheat,
edaphic factors limit its distribution to the Dakotas and to Western
Minnesota. Here is a level tract of land with rich productive soil,
a bequest of the long-deceased Glacial Lake Agassiz.

Finally it would be well to point out an economic factor, not
a part of the theory of rent, which is intimately related to the pro-

FACTORS AFFECTING CROP DISTRIBUTION

41

42 PLANT SUCCESSION AND CROP PRODUCTION

duction of spring wheat. It is the invention of a milling device
which made possible the manufacture of a handsome white flour
from spring wheat. This device called the purifier, separated the
bran and endosperm better than any previously known machine
had done. But this machine, invented a generation ago, did not
establish the spring wheat center. It only intensified the already
increasing production. This helps one to understand how the eco-
nomic factors operate in crop distribution. They do not create
the conditions for plant growth, but profit is largely the determinant
which carries on or halts crop production.

In the ecological study of the vegetation, climatic conditions
are put down as the broad general determiners. The edaphic fac-
tors modify the effect of climate. In favorable soils, the center is
extended. In unfavorable soils, even well within the center, the oc-
currence of certain plants is prevented.

In the crops the economic factors increase or diminish pro-
duction. The physical factors determine whether or not a certain
plant may grow, but the profit determines whether or not produc-
tion will increase. This is the problem of the food administrator ;
to make the price of wheat, say, high enough to tempt the farmer
to increase production, and at the same time not to put it out of
reach of the majority of consumers. The relation of the economic
factor to crop production is analogous to the relation of the edaphic
factors to the climatic in the natural vegetation. The edaphic
factors have such an influence in modifying the climatic that the
occurrence of a certain plant is the direct result of the edaphic in-
fluence. The economic factors have such an influence in modifying
crop production, that even though the underlying climatic and soil
factors are suitable, production is still limited by the profits.

PART III
THE CROP REGIONS OF OHIO AND THEIR SIGNIFICANCE

A. Topography and Drainage

Ohio lies at the western edge of the Allegheny plateau. This
extends partly within the state, and constitutes the eastern and
southern three-fourths of it. The northwestern one-fourth is in
the Erie Plain. Southwest, the Allegheny plateau merges without
a definite line of separation into the Lexington Plain extending
northwest from Kentucky (see Fig. 7). In the extreme north-
west corner of Ohio is a low escarpment, separating the Erie Plain
from the Thumb Upland of Michigan. Thus the Erie Plain forms
a trough tilted toward Lake Erie. In Ohio the Erie Plain ranges
in altitude from 575 to nearly 1000 feet above sea level. (Geologic
Atlas, Columbus Folio pp. 1 to 4). The relief is, however, slight,
and it is on the whole a gentle rolling plain interrupted only by
low swells and morainic ridges. The Allegheny Plateau in Ohio
stands between 1000 and 1500 feet above sea level. It is tilted
southwestward and westward. The highest point in Ohio is at the
western edge of the plateau, near Bellefontaine in Logan County,
and is 1550 feet above sea level. In the eastern and southeastern
parts of the state, the plateau is so much dissected by valleys from
200 to 800 feet deep that but little of the plateau nature is discern-
able. The escarpment separating the plateau from the Erie Plain
is well marked in the northeastern and central part of the state.
The western ends of the escarpment are, however, obscure and
broken in two places by gaps which extend southward in the broad
valleys of the Scioto and Miami Rivers.

The drainage of the Erie Plain and its immediate boundary in
Ohio, about 12,000 square miles, is into Lake Erie and so on into
the Gulf of St. Lawrence. The rest of the state, about 30,000 square
miles, is drained into the Ohio River and through the Mississippi to
the Gulf of Mexico. Ohio thus lies on the divide of the two great
continental drainage systems of Eastern America. The divide be-
tween these systems is on the whole rather level and inconspicuous,
resembling a rib of an enormous umbrella rather than the ridge
of a roof. Lake Erie is about 140 feet higher above sea level

48

44

PLANT SUCCESSION AND CROP PRODUCTION

than the Ohio River. The plateau is better drained than the plain,
except near the edge where the drainage is rather poor and there
are a number of small lakes, swamps, and prairies. The narrow
belt of the Erie Plain along the lake shore is also well drained,

)etrc

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Scale
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Fig. 7. Outline map of Ohio showing the physioeraphic divisions. From the geologic Atlas,
Columbufl Folio 197.

but in the broad, nearly level area of the northwestern part, the
drainage is somewhat obstructed by glacial deposits. (Fig. 8).
These were formerly lakes and swamps. Later, they became prai-
rie areas. In recent years, however, drainage and cultivation have
effaced these except for the rich humus soil and a few relict plants
in undisturbed patches.

CROP REGIONS OP OHIO

46

There are some interesting features of the drainage of the
state which should be emphasized because of their bearing upon
the biota. From a biological point of view all of the valleys are
regarded as special means of ingress of animals and plants. It is

$ii,i..i.":--%i C_H1 GAN

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O lO 20 30 40 &OMII03
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Fig. 8. Map of Ohio showing glacial moraines and the limits of the drift left by the ice at
its several stages. The arrows indicate the direction of the ice movement. After Leverett, in
Geologic Atlas, Columbus folio 197.

not surprising then that many plants of the northeastern evergreen
forest have found their way into Eastern Ohio from the lake and
southward along the valleys which drain into the St. Lawrence
basin. Furthermore, a number of strictly southern species have
made their way into Central Ohio by progressing northward along
the valleys which are tributary to the Ohio. The state which lies
within the deciduous forest then, serves as a meeting ground for
both plants and animals of the northern and southern evergreen

4« PLANT SUCCESSION AND CROP PRODUCTION

forest, many of which are on the edge of their ranges. The drain-
age systems are to a large degree responsible for this condition.

B. The Soils

Soils represent the action of plants upon finely divided min-
eral materials. In the broadest sense the term soil means the
unconsolidated mixture of mineral and organic substances in which
green plants grow. This forms a covering, varying from a few
inches to many feet in thickness, over the rock surface of the
earth's crust. In a more restricted agricultural sense the soil is
only the surface eight or ten inches of this material. It is the
upper part which contains the largest proportion of the roots of
plants and which has become dark in color from the organic con-
tent. All strata below this surface layer are termed subsoil.
After the mineral matter of the subsoil has been exposed to the
action of the weather and has become the home of plant and ani-
mal microorganisms, it gradually becomes transformed into soil.

The mineral part of Ohio's soils were, for the most part, de-
rived from the geological formations underlying them. (Fig. 9).
One of the results of glacial action was the transportation of mate-
rial from north of Lake Erie. As the ice melted, the stones, clay,
and sand thus transported were left in a great mantle of drift on
top of similar finely ground material. Part of this transported
material became mixed with the soil existing at that time. Since
then much of the original drift has been carried away by stream
erosion, first as the ice melted, and second after it entirely dis-
appeared, by the normal stream flow. Some streams have cut
through to the original bedrock in many places. Others have
been forced by the accumulation of drift material, to cut entirely
new channels. The soils then, in the glaciated region, consist of bed-
rock material, surface and subsoil, plus a little transported soil
material and the organic remains of plant life which has not been
washed away since the beginning of post-glacial time. Coffey
(1912) gives a full discussion of the soil types of the state.

In the unglaciated region of southeastern Ohio, the mineral
part of the soils has been derived from the underlying bed rock
exclusively. Since the mixing effects of glaciation were lacking,
the composition of the soil material corresponds closely to the
composition of the rock except as weathering and organic action
have altered it. The dissection of the Allegheny Plateau by

CROP REGIONS OF OHIO

47

streams has left many steep slopes and deep valleys. The leveling
action of the streams, that is, the lowering of the hills and filling
of the valleys has been slight as compared with the leveling in the

^ PERMIAN PENNSYLVANIAN MISSISSI PPIAN^ DEVONIAN SILURIAN ORDOVICIAN

CARBONIFEROUS

Scale
O 10 20 30 40 soMilci

Fig. 9. Geologic map of Ohio. From the geologic map of North America in U. S. Geol.
Survey Prof. Paper 71.

glaciated sections of the state, where the deposits of till have filled
and blocked many of the valleys. On the steep slopes subject to
rapid erosion, good soil is not formed unless the plant cover is left

48 PLANT SUCCESSION AND CROP PRODUCTION

entirely undisturbed. The best soil in southeastern Ohio is to be
found in the stream bottoms where the surface material washed
down from the slopes has accumulated. With the cutting of the
forests, however, many acres of fine bottom lands have been, for a
time at least, ruined since the erosion of the hills was rapid enough
to wash down sandy subsoils. Instead of leaving a fine deposit of
rich organic matter as is usually the case, floods frequently drop
a load of coarse sand and gravel and bury the best soil of the farm
several feet below the surface.

From the standpoint of plant successions, the original compo-
sition of the soils has not had a great deal of influence upon the
plant life. Succession on clay soils and upon sandy soils is
much the same, though on the sandy soils the cycles require a
longer time from the initial stage to the completion of the cycle.
The structure of the soil, since it greatly influences the water con-
tent, has, on the other hand, a most important influence. In the
glaciated region of the state the soils were mixed thoroughly and a
good deal of material was clay. In the unglaciated regions the
soils are not mixed, except the alluvial soils, and have been derived
in situ largely from the underlying rock. The successions in the
glaciated regions have, except for the lake and swamp areas, ad-
vanced as far in the cycle in postglacial time as the succession in
the sandy and over-drained unglaciated region. In the latter area
the development of the vegetation has not been in any broad way
interfered with for ages preceding the advance of the several ice
sheets.

C. The Climatic Conditions

The influence of climate upon plant and animal is everywhere
considered to be of fundamental importance. In the broader geo-
graphic sense climate is more important than soil conditions. The
latter, however, frequently limit the local distribution. Elevation
above sea level, latitude, relation to large bodies of water and the
direction of prevailing winds are all factors which exert a con-
trolling influence upon the climate of a region.

The effect of land relief and of elevation is to be seen in the
precipitation and in the length of the growing season, i. e., the
number of days between frosts in spring and fall. The least pre-
cipitation occurs in the flattest portion of the state — a part of the
Erie Plains (see Fig. 10), and in a narrow band southwest of Lake
Erie. Here the annual precipitation averages from 30 to 34

CROP REGIONS OF OHIO

A»

inches. The greatest precipitation occurs in eastern and south-
eastern Ohio, one region being a band covering the Ohio River
counties from Brown to Mahoning and another being a center
southeast of Lake Erie in Lake, Ashtabula, and Geauga counties.

3Q

Fio. 10. The average annual precipitation for the different sections of Ohio shown graph-
ically by means of shaded areas. The total fluctuation is eight inches. The least rainfall
is near the western end of Lake Erie, averaging about 32 inches. There are large areas in
the western portion of the state having an annual rainfall of less than 34 inches The heaviest
rainfall occurs along the Ohio river, where, in the most heavily shaded part of the diagram
the precipitation is more than 40 inches.

Here the precipitation averages 40 inches. The reader is referred
to the charts appearing in the Ohio Agricultural Experiment Sta-
tion Bulletin 235, one of v^^hich is here repeated in a modified form.
Elevation also shows an influence in the length of the growing
season. In southeastern Ohio stations only a few miles apart
horizontally, but with a difference in elevation of several hundred

60

PLANT SUCCESSION AND CROP PRODUCTION

feet, may be twenty days apart in the length of the growing season.
For example, at Milligan twenty-three years of frost records give
an average of 145 days in the growing season. Eighteen years
of records give Somerset 174 days.

More important than the length of the growing season, how-

23-5-2+5^

z^s:us/

«4 v5 -tSS

MEAN EFFECTIVE HEAT

MtPifS TE.MPE.R.,ATURX. A&OVt. 4Z.° rRJDM APRJL IS
TO OCTQCE-R. I aj

Fig. 11

ever, is a chart of the mean effective heat (Fig. 11). The data for
this chart were obtained through the kind cooperation of Mr. W. H.
Alexander, meteorologist and section director in the U. S. Weather
Bureau, who allowed the writer to examine the records on file in
the Columbus Weather Bureau office. The temperature normals
from all the weather observation stations in the state were ob-
tained and the average temperature from April to October found.
From this average 42 was subtracted, since 42° F. can be regarded

CROP REGIONS OF OHIO 61

as an average temperature below which plants do not grow very
actively. In other words, it is the threshold of our spring season
as far as the temperature is concerned. Although the station's
records used in the chart are rather scattered in the southeastern
portion where temperature varies most and where therefore the
stations should have the highest distribution frequency from our
point of view, some allowance has been made for elevation. This
chart will be modified in the future as increased data seem to war-
rant it.

Columbus, on the fortieth parallel of latitude is slightly south
of the center of the state. The extreme southern portion of the
state extends a little south of 38° 30' N. latitude. The northern-
most point almost touches latitude 42°. This position of Ohio af-
fects the seasons and the total amount of energy received from the
sun. At Columbus the length of the day varies from nine hours
and twenty-one minutes on December 15th to fifteen hours on
June 15th.^ During the longest days of summer the average
length of the day is almost eighteen minutes longer in the north-
ern part of the state than in the southern. Reference to Part I is
sufficient to inform the reader that the dispersal of the energy is
of greater importance in plant and animal geography than the total
absorbed, so we may pass this point without further comment.
Smith ('12) loc. cit. has described the general climatic conditions
of Ohio as follows :

"Ohio is in the path of the general low pressure or storm
areas which move across the United States from west to east.
These areas move at an average speed of 600 miles in twenty-four
hours and are preceded by southerly winds and high temperature,
and followed by northerly winds and lower temperature. They
are usually accompanied by cloudy weather and precipitation and
each storm causes an average of from one to two rainy days at
each place as they pass across the state.

As there is an average of two of these storm areas each week
with fair weather periods between them, it follows that the
change in weather conditions is rather rapid.

Yet Ohio is far enough from the coast so that the damaging
Gulf and Atlantic storms lose very much of their severity before
reaching our borders."

1 These figures are for the year 1917. There is a slight variation, a few minutes per
day, from one leap year to the next. This is not of any significance in the present work.

62 PLANT SUCCESSION AND CROP PRODUCTION

No comprehensive detailed studies of evaporation in this
state which can be correlated with plant growth have been
made. Dickey ('09) and Dachnowski ('11) have studied the
evaporation at Buckeye Lake, using the Ohio State University
campus lawn as unity. Sears ('16) has shown the evaporation
in the plant zone at the edge of a marsh in the Lake Erie region.
There are no other data available at present.

For a comprehensive idea of evaporation and rainfall there
is the map of rainfall — evaporation ratios of Transeau (Figure 2,
p. 35), however. This gives a generalized picture of the effect of
air temperature, wind velocity and evaporation power of the air
in their effect on plant life. It was made by examining the forest
and prairie centers and finding a moisture index which best de-
scribed their climatic peculiarities. This chart shows that the
northeastern corner of Ohio, v/here Pinus strobus and other plants
of the northern evergreen center are known, has a rainfall evapo-
ration ratio of 100 to 110 percent. The greatest portion of the
state is covered by the deciduous forest and has a general ratio
of 80-100 percent, while in the edaphic prairies of Ohio the ratio
is between 60 and 80 percent. Further work on evaporation and
its relation to the vegetation centers is in progress. As soon as
this is published our understanding of the relation of forests and
prairies in Ohio will be greatly enlarged. The Erie Plain has
uniformly less than 34 inches of rainfall, the Ohio River region 40
inches. The heaviest rainfall occurs during the summer months.
June, July, and August. June has the greatest average rainfall with
4.13 inches. July is only slightly less rainy. The least monthly
rainfall is in October, averaging only 2.52 inches.

The path of the storm track has an influence upon the direc-
tion of the prevailing winds. Over most of the state the prevailing
winds are from the southwest. Two notable exceptions, however,
are Cincinnati and Cleveland where the prevailing winds for the
year are from the southeast. The average hourly wind movement
is nearly nine miles. It varies with the season, being greater in the
winter and spring months than in the summer and fall months.
Near Lake Erie the average velocity is greater than in the central
and southern portions of the state.

The humidity or the saturation deficit of the air is one of the
most important climatic influences upon plant and animal life. In a
state as large as Ohio and with such varied topography, the rate

CROP REGIONS OF OHIO 63

of evaporation differs widely under various conditions. The
southern boundary of Ohio, along the river, is in approximately
the same latitude as Washington, D. C, while the northernmost
point approximates Cape Cod, Massachusetts, in latitude. The
summer temperature at these extremes would influence greatly
the evaporation rate. There is a difference of approximately a
thousand feet in elevation from the lowest part of the Erie Plain
to the highest point of the Allegheny Plateau. This would also
affect evaporation to a marked degree how, while the wind veloci-
ties would vary in the level regions and "cold waves pass across
the state with sufficient intensity to ventilate and invigorate the
towns and cities and send their health-giving winds into all parts
of the state, and yet the cold waves are not so severe in Ohio as in
corresponding latitudes in the Mississippi and Missouri valleys."
The fact of great significance is that Ohio lies directly across the
path of one of the main storm tracks, and there is rapid alter-
nation of areas of low and high barometric pressure. The writer
('18 p. 55) has discussed the influence of this feature of climate
upon crops.

The state is 205 miles long from north to south and the effect
of latitude is seen in the climatic difference in the northern and
southern extremes of Ohio. The influence of Lake Erie is to
counterbalance the effect of latitude in a narrow strip just south-
east of the lake. Lake Erie is an inland sea, giving an oceanic cli-
mate to a narrow strip of land bordering it. The work of Miller,
(1917), in Wisconsin shows the climatic effect of the lakes over
territory comparable to the Lake Erie region of Ohio. The
mean annual temperature in the northern part of the state is
48° F., in the central portion 51°, and in the southern portion
54° to 55° (Smith '12). The coolest sections of the state are in
the northeastern and northwestern districts, while the warmest
are in the extreme southern and southwestern counties. Isothermal
lines show the influence of elevation. From Champaign to Ottawa
counties, a distance of over 100 miles across the Erie Plain, the
average temperature varies less than one degree. The lowest mean
annual temperature is in Portage County, 47.2°. The highest,
55.5°, is in Scioto County. The precipitation shows similar dif-
ferences, increasing southward. The least precipitation is near
the western end of Lake Erie, and the greatest along the Ohio
River.

64 PLANT SUCCESSION AND CROP PRODUCTION

D. The Vegetation Centers Entering Ohio

When the climatic features of a region are studied it is neces-
sary to correlate these features with the climatic conditions sur-
rounding it. We cannot understand the vegetation of Ohio as it
exists today without having something of the nature of the vege-
tation of Eastern North America in mind.

Adams ('02) has pointed out the ideas of centers of flora and
fauna which have been accepted and amplified by ecologists- Since
plants migrate into and multiply in regions where the soil and
climatic conditions are favorable, we can regard the native vege-
tation as a criterion of the climatic and soil conditions. We must
not overlook the fact that after the plants are once established
they are themselves agents in altering climatic and soil conditions,
especially the latter, and they pave the way for the spread of other
species. From our point of view then, the plants are both passive
and active, are effect and cause.

For the existing plant cover, it is not necessary to go back any
farther than post-glacial time following the last glaciation. The
vegetation in southeastern! Ohio is much older than that, however.
During glacial times southern Ohio became the refuge of northern
plants, retreating before the advance of the ice sheet. Along the
margin of the advancing ice was a series of bands which from
the ice outward were: (1) Arctic tundra, (2) a bog-shrub zone,
(3) northern evergreen forest. Beyond this the central deciduous
forest was little disturbed except for the advent of the northern
species. In the southeastern part of North America the southern
evergreen forest was not at all disturbed by the ice cap of the
northern part of the continent. These conditions were discussed
by Transeau ('03), Chamberlain and Salisbury ('06), and by
Clements ('16, p. 372). The climatic changes as recorded in the
peat bogs at that time have been discussed by Penhallow (1896,
'98, '00) and Harshberger (1911) and Dachnowski (1912, p. 209).

There were several advances and retreats of the ice sheet, and
according to Leverett ('02) the glacial boundary is a combination
of four invasions, but when the ice finally made the retreat which
carries us into the present time, there was a gradual migration of
the vegetation northward. The shrub-bog zone advanced into the
tundra, the northern evergreen forest into the shrub, and the de-
ciduous forest regained its former terrain. There is no definite in-
formation as to whether the movement is still going on or has come

CROP REGIONS OF OHIO 65

to a full stop. However, we can still see in Ohio the advances of
the deciduous forest into regions held by northern evergreens, as
for example, the capture of the arbor-vitae bogs by deciduous
plants. This movement has been hastened by agricultural activi-
ties. The bogs existed only as biological islands. Their destruction
means extermination, since the conditions which led to their pres-
ei'vation are rapidly passing.

Ohio has been divided into four vegetation regions by Selby
(1899). This had the approval of Dachnowski (1912) p. 203.
These four divisions are: 1. The Lake Region; 2. The Western
Plain or Calcareous Region ; 3. The Scioto Valley Region ; 4. The
Appalachian Region. This static classification has for its chief con-
venience the fact that it divides the state into regions of approxi-
mately equal size. It has on that account been followed by the
United States Weather Service. As a matter of fact it is not very
closely related to the biotic centers which traverse Ohio. Following
the physiographic divisions already made in this paper, we have the
Allegheny Plateau and the Erie Plain. The plateau is occupied by
the deciduous forest, which has its center in the Ohio and Wabash
valleys, except as the plateau is held by plants of the two evergreen
centers. Pinus strobus, from the northern center and P. Virginiana
and P. rigida from the southeastern center are both present in the
eastern part of the state. The northern evergreen center is better
represented than the southern evergreen center. Then there are
on the Erie Plain and in a few scattered spots south of the plain,
typical prairie plants. The four vegetation centers represented in
Ohio are : the deciduous center, the two evergreen centers, and the
prairie center.

The deciduous center, the most important one in Ohio, is rep-
resented by such trees as Fagus Americana, Acer Saccharum,
which are the principal elements of the climax beech-maple forest;
Castanea dentata, Quercus alba, and Liriodendron tulipifera-
There are many other trees and shrubs and a large number of her-
baceous plants. Trees from the northern evergreen center are
Pinus strobus, Tsuga canadensis. Thuja occidentalism Taxus cana-
densis, and Larix laricina. The firs and spruces are missing, but
the flora is enriched by many northern shrubs and herbs. These
are on the edges of their range in northern and northeastern Ohio.
The northern species gain their entrance, or rather have not been
driven out, through the hills of the eastern section of the state and

56 PLANT SUCCESSION AND CROP PRDDUCTION

more northern species are known in the eastern than in the west-
em section of the state. The southern evergreen trees are Pinus
echinata, P. rigida, P. virginiana, and Jnniperus virginiana. In
addition should be mentioned the bear oak, Quercus ilicifolia, which
reaches the northern edge of its range in Ohio. There are also nu-
merous shrubs and herbaceous plants of the southern center which
reach the limit of their ranges. These perhaps belong more fairly
to the deciduous center and are simply its southern species, rather
than species of the southern center reaching up into the deciduous
center. The prairie center is rapidly disappearing and is being re-
placed largely by cultivated lands. The prairies if planted now
with trees would undoubtedly support the vegetation of the central
deciduous forest. The bogs and the prairies both belong in the gla-
ciated portion of the state and were most numerous in the western
part. One of the best evidences of the northward migration of
plants since glacial times is to be seen in the plants which were left
in the undrained depressions. They became established in early
post-glacial times, and the deposits of peat since have tended to
keep a cool substratum, which led to the preservation of these
species.

E. The Crop Centers of Ohio

The crop statistics of Ohio have been faithfully compiled by
the Ohio Board of Agriculture and published for its citizens. This
constitutes a valuable annual record which indicates the scope and
magnitude of one of Ohio's greatest businesses. These records have
been drawn upon freely in gathering the present data. The sta-
tistics are published by counties so that each community may see
what it is doing and what its neighbors are doing. For convenience,
the compilers have divided the state into four sections — northeast,
southeast, northwest, and southwest — and the county totals are
summed in accordance with this division. For our present purpose
this will not always show that crops center in a certain area. The
political divisions do not all correspond with natural physiographic
and geographic ones. The ivriter has not hesitated therefore to add
or substract county totals from one district where the geographic
data warrants, and place these in another group. Wherever this is
done attention is called to the fact that the names of the counties
specifically mentioned. This rearrangement of data is in accord with
the plan of the whole line of investigation here recorded, namely,
the genetic point of view, which aims to show the relation of the

CROP REGIONS OF OHIO 67

natural vegetation and the cultivated crops to fundamental soil and
climatic conditions. In the case of the cultivated plants, economic
conditions must be included as well, as has been shown in Part II
of this paper.

(a) Com

Ohio is one of the seven states which constitute the com belt
of the United States. (See Chart in Part 11.) There is in Ohio a
plainly marked corn belt which corresponds in many ways to the
corn belt of the United States. It is located in level soils with a
high humus and lime content. All of the western half of the state
may be regarded as a part of the corn belt. The center of popula-
tion is in the northwest. Production is cheapest on the level, fre-
quently prairie, soils of northwestern Ohio and the com center has
settled here. This was not the original corn belt of Ohio. The
northwest was the last section of the state to be settled, and its de-
velopment waited on the opening of the Erie Canal. During the last
fifty years production has increased in the northwest section so that
it outstrips all the older sections. Perhaps poor farming methods
of a half and a quarter century ago had something to do with a
decrease in the southeastern section, but even with the newest and
best farming methods the southeastern part of Ohio is not so well
adapted for com cultivation as the northwestern. The centering of
com in the northwest seems to be a normal, healthy migration of
a crop into a region to which it is well adapted. In 1916 the total
state estimated production of com was 82,953,943 bushels. This
was divided among the sections of the state as follows :

Northwestern section 35,101,566

Southwestern " 29,153,460

Northeastern " 10,571,956

Southeastern " 8,126,961

When the production of the two western sections of the state
is summed we find that 78 percent, or nearly four-fifths of the corn
grown in Ohio was produced in the western part of the state. This
clearly indicates the dominance of com in the western part. If we
wish to make a picture of com production on a map, we will find
that there are three highly productive centers in the corn belt. The
first includes Seneca, Wood, Henry, Putnam, Allen, and Hancock
Counties. The second includes Franklin, Madison, Clark, Green,

58 PLANT SUCCESSION AND CROP PRODUCTION

Clinton, Fayette, Highland, Pike, Ross, and Pickaway Counties.
The third includes Darke, Preble and Butler Counties.

(b) Wheat

Brigham (1910, pp. 44 and 45) has shown in the yield of wheat
of the United States by decades, 1839 to 1899 inclusive, that six
times out of the possible seven Ohio has been within the first four
states in production. The rapid westward progress of the center
of wheat production is shown in the fact that Illinois was not men-
tioned in the group of four until 1859. It took first place and held
that for three years before dropping out of the lists as suddenly as
it entered. In forty-one years, 1866 to 1906, Ohio has produced
1,247,082,674 bushels of wheat, an average of thirty million
bushels per year. It has eight times exceeded forty millions.

The following table from the Twelfth Census gives the loca-
tion of the wheat centers of the United States for the period 1850
to 1900.

Wheat Center, U. S., 1850 to 1900 (Seconds Omitted)

Census Year

N. Lat.

W. Long.

1900

41° 39'

94° 59'

1890

39° 33'

93° 9'

1880

40° 36'

90° 30'

1870

40° 39'

88° 48'

1860

39° 59'

86° r

Approximate Location by Important Towns

70 miles west of Des Moines, la.

138 miles south by east of Des Moines.

(In Missouri.)
69 miles northwest of Springfield, 111.
82 miles northeast of Springfield, 111.
18 miles north by east of Indianapolis,
Ind.
1850 40° 14' 81° 58' 57 miles east northeast of Columbus,0.

In Ohio, as in all humid climate states, the average yield of
wheat is moderately high and is above the average for the whole
United States. The average yield for Ohio is sixteen and a fraction
bushels per acre. The average for the United States is something
like twelve bushels per acre. According to Thome (1917, pp. 48-50)
the average for Wayne County is nineteen bushels. In spite of
these higher yields per acre and therefore better returns per acre,
wheat is found centering in that part of the United States just
west of the corn belt. This is a region of less moisture than in the
corn belt and where corn production consequently is not at its high-
est development.

The reasons for wheat being grown in this center are not diflEi-
cult to see. Where coiti can be grown to its greatest advantage it

CROP REGIONS OF OHIO 69

is the dominant crop. The returns per acre in grain and fodder
are greater than from wheat and the money returns are also greater.
Why is wheat grown at all in the humid sections, if com gives it
such competition? There are several reasons. A farmer can grow
wheat and even in normal times make a return on his investment.
He has also found out that to grow corn continuously does not pay.
Clover or clover and timothy usually enter into a scheme of crop
rotation. Wheat serves as a crop to sow with the hay crop which
will return a yield for the use of the land while the hay plants are
becoming established.

It is not surprising in the light of the above reasons for wheat
culture in humid regions, that we find wheat centering in the same
part of Ohio in which corn centers. It is found in the western
part of the state. Wheat suffers more from disease, from insects
and unfavorable weather conditions than corn does, so it is not
surprising to find that the yield from year to year varies widely.
In Ohio June and July are the months of heaviest rainfall. This
rain is usually too late to help the growth of wheat much and is often
the cause of damage. The wheat yield in 1913 was 27,825,105
bushels and in 1915, 35,624,381 bushels. In 1913, the southwestern
section led. In 1913 the two western sections produced 63 per-
cent of the crop; in 1915 the same sections produced 60 percent
of the total wheat. This shows in spite of variation in yield that the
wheat centers in the western half of the state.

There is another way of locating a center if there is some
doubt as to its exact location and that is by examining the acreage
sown to a certain crop rather than the actual production. This
has the advantage of showing what the farmer intended to pro-
duce. What he is actually able to grow depends on a number of
circumstances, many of which are beyond his control. In 1915,
there were 1,888,642 acres in Ohio from which wheat was har-
vested. This was distributed in the state as follows:

Southwestern section 599,704

Northwestern " 587,979

Northeastern " 466,750

Southeastern " 234,211

When the two western sections are summed, we find that 62
percent of the wheat crop came from the western section of the
state. It is also interesting to note that while the southwestern

60 PLANT SUCCESSION AND CROP PRODUCTION

section led in acreage, the northwestern section led in yield that
year. This bears out the contention that in a crop subject to dam-
age from conditions beyond the farmer's control, the acreage is
frequently a better way of locating the center than is the yield.
In a paper recently published the writer (1918, p. 62) discussed
the criteria for locating a crop center based upon production.
For most purposes the use of production is the method favored.
The above example shows how acreage may be used to advantage.

(c) Oats

In the United States, the center of oats production is only
slightly north of the corn belt. This is the case in spite of the fact
that oats are proverbially a cool climate crop with a high moisture
requirement. Under such conditions it would be expected that the
center of oats production be found much farther north than it is.
Oats are grown in rotations into which corn enters as the most
important plant. On farms following such rotation schemes,
there is need for much horse labor. Oats are ideal for horses and
oat straw is much prized for bedding, besides furnishing a cer-
tain amount of bulky feed. It is obvious then, that to bring the
oats center near to or within the corn center is desirable. The
difficulties have been partially overcome by the use of early matur-
ing varieties, which have escaped the summer heat, rusts and
smuts. There still remain plenty of opportunities to originate
new varieties or strains of oats which are better adapted to com
belt conditions than any of the varieties now grown.

In Ohio we find that the production of oats centers strongly in
the northern part of the state and that the heaviest production is
in the northwest, where corn production centers. For 1915 the
total production of oats for the state was 57,087,410 bushels. The
sectional yields were as follows :

Northwestern section 31,380,518

Northeastern " 19,592,053

Southwestern " 4,414,773

Southeastern " 1,700,066

In the northern part of the state 89 percent of the oats crop
was produced in 1915. It is not difficult to see where the center of
oats production is located.

CROP REGIONS OF OHIO 61

(d) Hay

Timothy and Clover Hay. — The northeastern section of the
United States is known to agronomists as the hay and pasture pro-
vince. To ecologists this is southern edge of northeastern ever-
green forest. Both the cultivated plants and the natural vegetation
are responses to the climatic conditions of this part of our country.
Northeastern Ohio contains the southwestern limit of the northern
evergreen forest. This is Ohio's hay and pasture belt.

The total hay production for 1915 in Ohio was 2,240,761 tons.
This was divided as follows :

Northeastern section 842,223 tons

Northwestern " 646,898 tons

Southeastern " 454,611 tons

Southwestern " 297,029 tons

The northern half of the state with lower summer temperatures
and lower evaporation making its rainfall more effective for con-
tinuous growth of untilled plants, has the higher production. In
grass hay, the eastern half of the state leads, but in clover hay the
western half is in advance as can be seen from the following table :

Northwestern section 387,497 tons

Northeastern " 120,500 tons

Southwestern " 144,318 tons

Southeastern " 43,901 tons

The total clover hay production for 1915 was 746,226 tons.
The difference in clover production in the eastern and western half
of the state is doubtless due to limestone. All of the soils of the
western half of the state are naturally underlain with limestone
bedrock. A good deal of the limestone material was brought near
the surface by glacial action and subsequent weathering has not yet
leached away all of it. It is a well known fact that clovers grow
best when inoculated with the nitrogen gathering bacteria. These
bacteria grow best in non-acid soil medium. The grasses are not
dependent upon these bacteria. Furthermore, a meadow of timothy
will be productive of compact clay soils where clover would be only
moderately productive. This again shows the importance of the
bacteria to clover production. In the tight clay soils the air cir-
culates less freely, so the growth of bacteria is limited. The soils
with a high lime content and a high humus content, as many of the

62 PLANT SUCCESSION AND CROP PRODUCTION

farms in the northwestern section are on former prairies now
drained, seem more suitable for clover production. In southeastern
Ohio the soils are porous enough for the growth of the nodule form-
ing bacteria and clover could be doubtless grown with the liberal
use of lime and a crop occasionally plowed under for green manure.

(e) Potatoes

Potato production in Ohio also centers in the northeastern
part. In the United States the potato crop seems to follow popu-
lation more than any special climatic or soil factor. We find a small
center of potato production near each of the thirty largest cities of
the United States. The east coast of Maine, however, is a famous
potato center. This points to a northeastern center for potato
production. In Ohio the total production of potatoes in 1915 was
7,757,169 bushels. The sectional production can be seen from the
following :

Northeastern section 4,039,487 bushels

Northwestern " 1,499,446 bushels

Southwestern " 1,351,122 bushels

Southeastern " 867,114 bushels

(f) Tobacco

Tobacco is in many ways one of our most interesting crops. It is
extremely susceptible to the environment and assumes many varia-
tions in growth form according to the treatment it has received dur-
ing cultivation. In the United States, it centers in Kentucky, Vir-
ginia, and North Carolina between the corn and cotton belts. Ohio,
Pennsylvania, Wisconsin, and Connecticut also engage in tobacco
production. In Kentucky while given more attention in cultivation
than corn receives, it is grown nevertheless on an extensive system
of farming. Farther north it receives a good deal more care, as
much often, as vegetables grown on an intensive system would get.
In some places in Connecticut it is grown under cloth shelters.
These shelters lower the transpiration rate in the daytime. They
also decrease the radiation of heat at night, thus maintaining more
equable climatic conditions. The shading increases the size and de-
creases the thickness of the leaf thus making a product more suit-
able for cigar wrappers.

The Ohio tobacco center is in the southwestern part of the
state — a continuation, as has been pointed out, of the Lexington

CROP REGIONS OF OHIO 08

Plain. The counties along the river grow and cure Burley tobacco
in the same manner as it is grown around Lexington, Kentucky.
Near Dayton the tobacco is grown for cigar fillers. In south-
eastern Ohio the tobacco is grown for export trade, as in Mary-
land. The small northeastern Ohio center produces cigar fillers.
The writer (1916) has reviewed the methods of growing and
handling Ohio's tobacco crop.

In 1915 the total tobacco production was 42,354,308 pounds.
This was distributed as follows according to the statistics of the
Board of Agriculture :

Southwestern section 26,613,759 pounds

Northwestern " 12,766,556 pounds

Southeastern " 2,719,394 pounds

Northeastern " 254,563 pounds

If, however, we substract from the production credited to the
northwestern section the amount produced in the four counties.
Champaign, Darke, Mercer, and Shelby, there is less than 3,000
pounds, a negligible amount, produced in Northwestern Ohio.
Darke county alone produced the bulk of this yield, 12,614,956. The
type of tobacco and method of handling show that it is essentially
the same as that produced near Daj^on. Our centers then should
rank as follows : (1) Southwestern, (2) Southeastern, (3) North-
eastern. When the production of Darke County is added to the
southwestern counties it is seen that this center produces 90 per-
cent of the total crop.

(g) The Centers of Livestock Production

The dependence of animals upon plants, often specific ones, for
their food, is a well known fundamental fact which needs no am-
plification here. However, when detailed information showing how
this relationship operates in determining the distribution of ani-
mals is presented, plants are brought out in their true role as the
basis of all agriculture. While no claim for novelty is made for any
of the material here presented, it is hoped that the method of pres-
entation will offer a new insight into agriculture even for those
who are best acquainted with it.

64 PLANT SUCCESSION AND CROP PRODUCTION

(h) The Dairying Indiistry
The number of milch cows in 1915 was 748,526. These were
distributed over the state in the following proportions:

Northeastern section 254,050

Northwestern " 225,090

Southwestern " 152,560

Southeastern " 116,826

This distribution makes the northern half of the state the dairy
cow center. This agrees with the hay and pasture provinces both
in the United States and in Ohio. A region in which summer pas-
tures are most productive is adapted to dairying. The conditions
making for productive summer pasture insure a good hay crop for
winter feeding, and with silos green feed can be had in winter.
Milk production, butter and cheese production, both that made in
home dairies and in factories and creameries follow the general
trend of this distribution. Space does not permit the detailed re-
cital of these accounts. The northeastern section contains 50 per-
cent of the creameries of the state and 54 percent of the cheese
factories. The home production of butter and cheese greatly ex-
ceeds the factory production of both of these commodities.

(1) Horses and Fat Stock
The corn belt — the northwestern part of the state shows the
dependence of the fat stock upon grain. The horses are there be-
cause their work is needed for the production of this grain. Forty-
four percent of the beef cattle are in the southwestern section of
the state, where the most dissected part of the glaciated region
permits corn cultivation and has produced land suitable for winter
feeding of beef cattle on com roughage. Twenty-six percent of the
beef animals are in the northwestern part of the state. Thus the
western half of the state supports sixty-eight percent of the beef
production. The southwest has thirty percent of the state's pro-
duction of hogs. The hog center is in the northwest which has
forty-four percent of the production. Seventy-four percent of the
hog production is located in the corn belt.

(j) Sheep
There is an important sheep raising center located in south-
western Pennsylvania and southeastern Ohio. This the writer
(1918 p. 79) has described as an edaphic center or one related to

CROP REGIONS OF OHIO OB

soil and physiographic conditions. There is, in contrast with this,
a climatic center of sheep production in the semi-arid districts of
the West which extend from Arizona northward to Montana.

The grouping of the statistical data as published by the Board
of Agriculture does not show the relation of the production of
sheep to the Ohio-Pennsylvania edaphic center. For our present
purpose this data is slightly differently arranged. The production
of Jefferson, Harrison, Knox, Tuscarawas, and Coshocton counties,
although listed with the northeastern production, is credited to the
southeastern part of the state. These counties are the border
counties between the northeastern and southeastern sections, so
that the statistics cannot really be considered distorted by this
transfer. The state and section totals as recorded are :

Northeastern section 462,354

Northwestern " 400,407

Southeastern " 397,262

Southwestern " 131,576

Total 1,391,599

The totals from counties above named are in round numbers
250,000. When this is added to the southeastern section it gives to
this section about 650,000 or forty-six percent, to be exact. This
leaves 150,000 to the northeastern section and it is transferred
from the first to third place in rank. The correctness of this
transfer can be seen from the figure showing the distribution of
sheep in Ohio and Pennsylvania (Fig. 12).

Sheep can be kept on pasture less continuously productive of
the best forage than is required for dairy cattle. Southeastern
Ohio is for this reason admirably adapted to sheep raising. Also
since the rough topography makes a permanent plant cover better
for the light easily eroded soil than cultivated crops, sheep raising
should be encouraged for this section of the state. It is a part of
the system to winter the sheep in sheds and to feed them grain. The
bottom lands of southwestern Ohio can produce sufficient grain to
feed the sheep and other livestock and leave some for local human
consumption. Feeding the sheep in winter makes the dual purpose
sheep, that is, those which produce both wool and mutton, the most
economical. There is no fundamental reason why a local demand
for mutton could not be developed in this country as has been done
in England.

66

PLANT SUCCESSION AND CROP PRODUCTION

CROP REGIONS OF OHIO

67

(k) Fruit

Apples are the most valuable of Ohio's fruit crops, though the
peach and grape producing region near Lake Erie is well known.
It is not necessary to repeat the reasons for the existence of the
Lake Erie fruit belt, since these have been several times discussed.
Nor is it necessary to give the peach and grape growing industry
more than passing mention though both are important. It is the
apple industry which at present solicits attention.

f?IT

I

APPLE

APPROXIMATE ACREAGE. I»I0

EACH DOT REPRESENTS

eOO ACRES

AOTvu. »«* covr»«o rr Twt

DOT IS m T1MC* »• ORCAT A*

^

r i^'^c^

/ i ♦ V ' i
/ '• ' ' r

\ ■'. •/ r

'

Pf J

^

r'

T-— i^J

V / 1

<• L

_ 1 \- V 5^ \

' S^IUS

^^^^^^/

/'*'

i I ' ^''.'•i^ fe' -

^

Ziz \ ''%:?; 'Hdf^

1^: -W'. tl.

'^'j^ •

nt'^

W^_v.

vL y^

^>S^-v^

y

vr""^

V

Fig. 13. Ohio's apply industry. In acreage the states rank, New York, Ohio, Pennsylvania,
Michiean. Compare the eastern and western states. From 1915 Yearbook U. S. Dept. of
Agriculture.

The conditions for apple production in southeastern Ohio are
ideal. Sheltered valleys in which both the soil and air drainage are
good are common. The rough topography, little suited to cultivated
crops, is a genuine advantage in tree crops. It is not surprising
then that we find the greatest apple acreage in Ohio in the south-
eastern part of the state. If the industry were encouraged and ad-
vertised, southeastern Ohio could market its apples as well as the
Oregon and Washington and New York orchardists market theirs.
Some capital and a great deal of cooperation are both needed to
develop this enterprise.

68 PLANT SUCCESSION AND CROP PRODUCTION

The total apple acreage for 1915 was 211,463 acres.* The
sections are as follows :

Northeastern section 77,105 acres

Southeastern " 56,062 acres

Northwestern ** 54,952 acres

Southwestern " 23,344 acres

If, however, we substract the acreage of Jefferson, Harrison,
Tuscarawas, Knox, and Coshocton counties, the northeast-southeast
border counties, from the northeast section, and add it to the south-
east section, it gives some 72,000 acres for the southeast and
61,000 in the northeast. There is, however, no sharp break in
the topography in the eastern part of the state north and south of
the glacial boundary. It is all part of the Allegheny Plateau. The
eastern half of the state contains sixty-three percent of Ohio's apple
acreage in spite of the fact that all over the state almost every
farm has a few trees. The chart (Fig. 13) shows the relation of
Ohio's apple acreage to Ohio's conditions and to the acreage in the
United States.

'Acreage is a better sruide to tree crops than a single year's production.

Summary and Conclusion

There is no better way of summarizing the foregoing discus-
sion on the effect of climatic and soil conditions upon agriculture
than by showing a chart of land values. This was made from the
state tax commission figures and while it does not give actual price
of land or show the changes in prices since the figures were collected,
yet the relative values are plainly discernible, and for our purpose
this is what is wanted. At first, the writer tried dividing the land
values into eight classes and using a large scale map. While this
gave much detailed information, the map appeared "patchy." Six
classes and two classes were subsequently tried and discarded. The
present chart (Fig. 14) was obtained by using the eight-class chart
but combining the classes 1 and 2, 3 and 4, 5 and 6, 7 and 8, making
a new chart of four classes. This chart, obtained entirely independ-
ent of physiographic, climatic or geological conditions, nevertheless
brings out some of these quite strongly, thus emphasizing their
bearing upon agriculture.

In the first place, the glaciers have the most important influ-
ence upon present day values of farm land. The Illinoisan (earliest)
glaciation was the most extensive. All of the land of lowest value,
(lightest shading) lies south or east of this glacial line, except for
the undrained bog land in the extreme northeast comer of the state.
The bog land probably has more potential farm value for cultivated
crops than most of the unglaciated territory. Except where cut
by the Miami Valley in the southwestern part of the state, the
once-glaciated terrain is separated from the several-times-
glaciated. The boundary of the Wisconsin drift is seen in the
southwestern part of the state and between it and the Ohio River,
the land is in the second class of values. The two glacial bound-
ary lines meet somewhere near Chillicothe. Running south
from Lake Erie through the central part of the state is the
line separating the Waverly formation on the east from the De-
vonian and Silurian on the west. Some of the Ohio river counties
in eastern Ohio show the influence of limestone outcrops in raising
land values, for the second-class values appear in a region of low-
est values. The third class constitutes our average or better farm
values. This class makes up the bulk of the state's area. The

69

70

PLANT SUCCESSION AND CROP PRODUCTION

fourth class, the highest values, show the influence of the cities
and towns upon farm land in the spread of the deep shading
around the area within which the city is located. It also shows

K.ELATIVE. LAMD VALUtO

Fio. 14. Chart of the relative land values in Ohio,
the two geological maps.

Compare with the physiographic and

the farm land not near large communities which takes its values
from the productions of the farms. Darke and Miami counties,
for example, near the Indiana line in the southwestern part of the
state, and Paulding, Van Wert, and Allen counties, are also shown

CROP REGIONS OF OHIO 71

as having high agricultural values. The spread of Cleveland and
the fruit belt along Lake Erie stand out. The city of Toledo and
the flat land of the Maumee River are both included in the heaviest
shading.

RE.LATIVE. LAND VALUES

Fig. 15. The relative value of farm land. Derived from the preceding chart by eliminating
the inflfluence of centers of population. Compare with the glacial map and the climatic maps.

There is still another extremely interesting feature. A pencil
line drawn from the southern part of the heaviest shading just
south of Cleveland, curving southwest around the curves of Lake

72 PLANT SUCCESSION AND CROP PRODUCTION

Erie and then northwest, north of Paulding County toward Indi-
ana and Michigan, and touching all the southern boundary lines of
spots of heaviest shading, will outline the old glacial Lake Maumee.
This is indicated on the Moraine chart (Figure 9, p. 47) by the
total absence of drift deposits since the land was covered with
water long enough to allow settlement and covering of coarse mate-
rial with a finer deposit from the lake. In post-glacial time this
territory has emerged. The finer soil deposits under water, and
the organic deposits of plants as the lake line retreated northward
to the present Lake Erie, are still of interest and importance to
us when we see in them a cause of increased land values.

The second chart of land values as shown in Figure 15, is made
by eliminating the areas in which tax evaluation comes from the ac-
crued value of population in the cities. Since the farm land would
have no value if it were not for population, and since on the other
hand the climate and soils are underlying fundamental factors in
the values, to be fair, both charts must be shown. The second
chart is our real summary and illustrates the ecological conditions.

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