Historic, archived document Do not.assume content reflects current scientific knowledge, policies, or practices. : i, ey bieueilN, « OE... HE ee) 2) USDEPARTNENT OFACRICULTURE © 9 RA No. 154 Contribution from the Forest Service, Henry S Graves, Forester. January 14, 1915. THE LIFE HISTORY OF LODGEPOLE PINE IN THE | ROCKY MOUNTAINS. By D. T. Mason, Assistant District Forester, District 1. GEOGRAPHIC DISTRIBUTION AND ALTITUDINAL RANGE. Lodgepole pine (Pinus contorta Loudon) is one of the most widely distributed western conifers. Its botanical range, shown in figure 1, extends from the Yukon Territory southward through the Cas- cade, Sierra Nevada, and San Jacinto Mountains to northern Lower California, and through the main range of the Rocky Mountains to northern New Mexico. Its commercial range, however, is much more restricted. At present lodgepole is being lumbered exten- sively only in Montana, Wyoming, Colorado, and the Uinta Moun- tains in northeastern Utah. Large areas also occur in Idaho, Wash- ington, Oregon, and California, but in these regions the tree is rendered less important commercially by the presence of other and more valuable timber trees. The “lodgepole region ”—that in which lodgepole is the preemi- nently important species—is mountainous, frequently interrupted by broad, open valleys, or plains, partly fertile and devoted to farming, and in part suitable only for grazing. The forests, as a rule, are con- fined to the mountains. The altitudinal range of lodgepole pine in the Rocky Mountains decreases from south to north. In Colorado and southern Wyoming the tree is found at altitudes ranging from 7,000 feet to timber line, or 11,500 feet; in northern Wyoming at from 6,000 to 10,500 feet; and in southwestern and central Montana at from 4,500 to 9,000 feet. As a rule, however, it forms commercial stands only within an altitudinal belt from 2,000 to 2,500 feet in width. In Colorado the best stands are usually between 7,500 and 9,500 feet; in Wyoming between 7,000 and 9,000 feet; and in southwestern and central Montana between 6,000 and 8,500 feet. In the more humid northwestern portion of _ Montana, outside of the main lodgepole region, the species grows at 62799°—15—1 2 BULLETIN 164, U. S. DEPARTMENT OF AGRICULTURE. an altitude as low as 1,800 feet, and occurs as a temporary type fol- lowing fire with little regard to elevation. Y, 3 o4ys 2s Fic. 1.—Botanical distribution of lodgepole pine. SIZE, AGE, AND HABIT. Lodgepole is one of the smallest of the commercially important pines. In well-developed stands approximately 140 years old, at which age the tree may be considered mature, most of the merchant- LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 3 able trees are from 8 to 14 inches in diameter breasthigh, and from 60 to 80 feet in height. However, trees up to 20 inches in diameter and 85 feet in height are common. The largest lodgepole of record in the Rocky Mountains is one on the Gunnison National Forest, Colo., which is 34 inches in diameter and 100 feet tall. On the Deerlodge National Forest in Montana is a tree 26 inches in diameter and 115 feet tall, containing six 16-foot logs and scaling approximately 1,000 board feet. Individuals over 30 inches in diameter have been found at other places in the lodgepole region. In California there are in- dividuals much larger in diameter than any mentioned, but these are usually short and hmby. Lodgepole pine seldom attains a very great age because of fire and insect damage. Stands over 250 years old are uncommon, and stands over 300 years very rare. The oldest stand on record is one on the Beaverhead National Forest, Mont., which has attained an age of about 450 years. As a forest tree lodgepole characteristically Prae a straight, slim, gradually tapering trunk with a compact, conical crown. In very dense stands trees which have been crowded throughout life may _ have extremely narrow crowns with a spread of only 3 or 4 feet and occupying only from 10 to 20 per cent of the stem length. In such cases the crown is usually irregular, and often appears as a mere bush at the top of the tree. In stands of moderate density the crown is still characteristically narrow, though more regular, and occupies from one-half to one-third of the stem length. Even in open-grown stands the crown seldom spreads more than from 16 te 20 feet, but the branches often come down nearly to the ground and the taper is usually rapid. CLIMATIC, SOIL, AND MOISTURE REQUIREMENTS. The climate of the lodgepole region is comparatively dry. Table 1 gives the essential climatological facts, so far as they are available from United States Weather Bureau reports. It indicates roughly the precipitation requirements of the various forest types of the region, data being given for stations in open country below timber line, where there is too little moisture to permit natural tree growth, up through the various timber types to the area above timber line. Lodgepole will probably grow only where the average annual precipitation is 18 inches or more. As a rule the best-developed stands occur where the precipitation exceeds 21 inches. It is not total precipitation alone, but the amount of available moisture in the soil, which determines the possibility of tree growth. This latter 4 ° BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. varies with the degree of slope, ground cover, and the permeability, kind, and depth of soil, and its degree of exposure to wind and sun. Air humidity also plays a part. TABLE 1.—Climate within the lodgepole region. {Compiled from United States Weather Bureau reports.] Ap- Annual precipi- Annual tempera- proxi- tation. ture. mate Type of land or forest period Ele- Station. at station—timbered aaHiCHl ees pLopen. aver- | 40D |, 00,,|Maxi-| Mini-|y-,,., | Maxi-| Mini- ages = *|mum.| mum. “| mum.| mum. are based tne, | Colorado: Years.| Feet. | In. In. In. |Deg. F.\Deg. F.|\Deg. F. Gunnison. ..... Below timber line... -. 21 | 7,670} 9.48} 13.45 | 6.86] 37.0] 96 —46 Moraine.......- Wellow\pine->. <=. - = DBO ioe Lose lWweodat |e lle | et OsSmleoO = 32 Marble. .......- Lodgepole......:--.... 4.| 7,951 | 29.60 | 35.66 | 21.82 | 40.2] 90 —29 Grand Lake....]..... GOVss DR er Se 5) |) 85153) | L766 | 2227745 | 12580 eae eae eer eee ae Georgetown....| Yellow bie (cut over)- 1D) 185550) 12582) | LONO5 sal 72 1 ese eee ee a ee Longs Peak... .. padeene Gee eee ee 18 | 8,600 | 20.00 | 29.84 | 13.93 | 387.8] 85 —31 ed clittes see |b Se Ore k oe cece 20 18; 695) 1920570) 130502) et OF 96 | aes yee tee Columbine. . ... inpelantl spruce. ... 31°85, 766) | 25.00 eS ae |e aes | ee | eee | eee Frances - -| Lodgepole. as eae 8 | 9,300 | 25.89 | 33.72 | 21.65 | 40.6] 86 —14 Breckinridge. - Bese WO ne. Soe cee 24 | 9,536 | 23.90 | 46.41 | 14.22) 33.7] 90 —37 Spruce Lodge.. -| Engelmann spruce.... 5) 1°95.600) |) 31564, S6502) |) 265020 see |ae i eee Leadville... --... Open jaeerent ce keel 15 |10,248 | 14.98 | 23.76 | 11.75} 35.0] 88 —27 Caronae-se ase Above timber line..... 6 |11,660 | 45.87 |°58.32 | 35.90} 26.2] 67 —30 Wyoming: Centennial... ... Below timber line..... 10 | 8,074 | 18.59 | 27.68 | 5.14] 38.8] 40.2 | —37.9 Woodrock!..... Lodgepole.-..........- 1), 8,500 [44539 44395 |e ee ales es So ern eel eee Dome wakes: s\eAlpimne. 22s: | eee Qi (BYSQT S48 | SSP ae eye 3047 Sears eee Yellowstone WNa- tional Park: Hort. ellow=9|| Juniper. . ss. 5.-4222--—- 9 | 6,200 | 16.93 | 20.35 | 13.31 | 38.3.| 40.2 | —36.3 stone. Tower Falls 3...| Douglas fir............ 3 | 6,250 | 16.27 | 19.29 | 13.63 | 35.6] 39.3 | —33.6 Riverside 3. .... odgepoles= =e 22-244. 4 | 6,500 | 19.58 } 23.85 | 14.38 | 35.3} 36.8 | —33.9 Sylvan Pass 3...]_.... COE seen Peers 4 | 7,000 | 25.48 | 27.72 | 24.03 | 34.2] 34.7 | —33.7 Snake River 3. .|..... One eee eee ee 4 | 7,000 |} 27.79 | 33.77 | 21.32 | 34.6] 36.2 ; —33.2 Fairview 3. .._-- Doupglasyires sss spe sass 6 | 7,000 | 16.11 | 18.83 | 11.51 | 34.9] 37.0 | —32.9 Fountain 3 Lodgepole Reyne 755th ee 3 | 7,220 | 17.90 | 19.07 | 15.88 | 33.2] 35.8 | —31/5 Geyser: Basineos |) >>» Oe rere seeeeeas ose 4 | 7,395 | 21.23 | 22.69 | 19.33 | 34.4] 36.2 | —31.6 Norris.) e252 do! i AO Seen eon 3 | 7,500 | 19.23 | 22.62 | 17.13) |- 33.4) 35.8)) —30)4 Lake Yellow- |..--. Gov eee eee 5 | 7,733 | 25.04 | 42.15 | 17.39 | 31.2] 33.7 | —29.4 stone. Grand Canyon3.|..... GOs aeereeas 2 | 7,900 | 25.72 | 27.81 | 23.62 | 31.9] 33.1 | —30.7 Montana: Helena........-. Below timber line. .... 33 | 4,110 | 13.42 | 19.94} 6.71 | 43.3 | 103 —42 , ivaineston = s\se- 2 < WO. sese ease oe 14 | 4,488 | 14.36 | 19.96 | 10.68 | 45.8 | 106 —34 a IBOZEMIAN sey ene GO n= SS pe ete 33 | 4,700 | 18.72 | 32.63 | 14.18 | 43.2 | 112 —53 4 Anaconda......- Juniper. ose sect eeee 11 | 5,300 | 14.99 | 18.89} 9.03} 42.1] 96 —33 i Buttes sae Below timber line..... 18 | 5,716 | 13.80 | 20.55 | 6.95} 42.1] 94 —29 3 Pipestone Pass.| Douglas fir............ 3 5s 800) (E1828 74) TONGC ML aOUe pees | eee Ue ee : IBOWeue sees Below timber line...-. | 6 | 6,060 | 13.75 | 18.56 | 10.10] 32.7} 90 —55 ; Fish Creek.....| Lodgepole-.-.......... 3 | 7,800 | 23.31 | 24.70 | 20.69 | 35.1] 80 —22 | 1 Probably reaches freezing every month; no temperature record. 2 Likely to get freezing temperature any ‘month. 8 Freezing pel er Saae or every month in year. tok * LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 5 “TABLE 1.—Climate within the lodgepole region—Continued. Ap- Killing frost. proxi- mate : Type of land or forest penieg en Spring. Fall. Station. at station—tim bered nich or open. whic snow- aver- fall ages Average | Latest | Average | Earliest. are latest. | known. | earliest. | known. | based Colorado: Years.| Inches. Gunnison. ..... Below timber line...-.. 21 46.5 | July 10 (1) Aug. 20 tY Moraine........ OLIOW, PiNGsck Mss 5552 23 96.1} June 17}, () Aug. 18 @ Marblescc: oc ee oe ee ee 4 157.4 | June 16} July 5] Aug. 26} Aug. 3 SUSE A 2 be 00 (0 5 173.2 (2) (2) (2) (2) Georgetown. . ¥élloy pine (cut over). 11 94.0 (7) (2) (2) (2) Longs Peak. ... .| Lodgepole. See eae 18 119.5 | July 10 (@) Aug. 28 (1) Hed clive Sse he BORE eco ec oes 20 205. 4 2) (2) () ty Columbine. ....| Engelmann spruce.... 3 21105 (2) (2) (2) (2 Frances. SE ek 6 27 010) (oe 8 183.5 | May 29] June 14] Sept. 10| Aug. 25 Breckinridge. - SLO ee ees 24 193.9 | July 21 (1) Aug. 9 () Spruce Lodge... :| Engelmann spruce.... 5 270. 7 2 2 2 (2) Leadville....... Minera: £25 SF 15 134.9 | June 15 | June 21] Aug. 31| Aug. 3 Garons=s co s2cek Above timber line..... 6 346.5 | July 18 Aug. 19 (4) Wyoming: Centennial. ....| Below timber line..... 10 134.8 | June 23 | July 9/{| Sept. 8} Aug. 25 Woodrock3..... odsepoles. hse 2258 1 321.1 3 (3) Dome Lake. ..| Alpine................ 2 2 Yellowstone Na- tional Park: Fort Pes ae UiSrerig) ee ae 9 ston aaa Falls5... Wouclas ins =. a2. 2 3 Riverside5.....| Lodgepole.-........... 4 Sylvan Pass 5...]..... OF eacc = =. 4 Snake River5...|..... Oe ae Rae ge ee 4 Fairview 5...... DWouelas fir ss. se). 65 2 6 Fountain 5...... Lodgepole............ 3 Geyser Basin5..|..... CO Se 4 INOLRIS DE. -o ce nob acess LO en bom alls 3 Lake Yellow- |..... OBa ees Hest 5 stone.5 : Grand Canyon5,.|..... OS. 88 Fase 2 1 SSH 5b este een ete oss | cree [ eee es oe Montana: HIDIGHR Ecos eat Below timber line..... 33 54.7 | May 7/| June 9 | Sept. 28| Sept. 5 Livingston. ....|..... oe: SEN ale eR 14 40.4 | May 20} June 20 | Sept. 17 ty) BOZEMAN wee es eo GOS et se eee a 33 ile tal May. i28il sed Osee sp SCD lan dal eAUea. Lo Anaconda... AUPE TOYS ee ie eee a 11 40.6 | June 17| July 8| Sept. 6| Aug. 14 Buttes: esa-2 <6 Below timber line...-. 18 55.2] June 5] June 26] Sept. 15 | Sept. 5 Pipestone Pass.| Douglas fir............ 3 LOIS) | seeaaeecee | Fecrsres sich stall Recents eae eeecioerae tay Bowenr-c* fei 5.2 Below timber line..... 6 LOMIE |Eaeseee Haart neem (eae ayaa aS eee Fish Creek. -...| Lodgepole............ 3 182.5 1 Midsummer. 2 No data. 3 Probably reaches freezing every month; no temperature record. 4 Likely to get freezing temperature any month. 5 Freezing temperatures every month in year. In southwestern Montana lodgepole occurs at elevations as low as 4,500 feet on northern exposures, where there is the greatest atmos- pheric humidity and the least evaporation from the soil. South slopes at this elevation, if timbered at all, usually support only such Species aS juniper (Juniperus scopulorum) or Douglas fir (Pseu- dotsuga taxifolia), which require less soil moisture than lodgepole and are better constituted to resist transpiration. Lodgepole is found on southern exposures at about 6,000 feet, provided the gradient is less than 10 per cent. A steep south slope is generally too dry for the species. At the upper limit of its range lodgepole gives way to other and more tolerant trees. Increase in soil and atmospheric moisture en- courages such species as Engelmann spruce (Picea engelmanni) and 6 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. Alpine fir (Abies lasicarpa), while the relatively short growing season at high elevations does not furnish the total amount of heat which lodgepole needs for its growth. The range of the species is thus limited on one hand by lack of moisture and on the other by lack of heat. Lodgepole occasionally endures for short periods extremes of tem- perature varying from approximately 100° F. to —55° F. The growing season of the region is short, since killing frosts are lkely to occur until about the middle of June and the first autumn frost comes early in September. In the lodgepole zone frost and snow may occur at any time during the growing season. May and June are the months of heaviest precipitation, but in the lodgepole zone much of this is in the form of snow, which usually covers the ground until late April or the middle of June, depending upon the elevation and aspect. Too much soil moisture is unfavorable to lodgepole, and good drainage is essential. The tree will not stand a water content of more than 35 per cent in a loam soil and only about half as much in gravel or sand. The best water content is between 12 and 15 per cent, though in gravel it may even fall below 5 per cent without effect upon the tree beyond a decrease in its rate of growth. In respect to their moisture requirements the different conifers of the region may be grouped as follows, those demanding the least mois- ture being placed first: Juniper, limber pine (Pinus flewilis), yellow pine (Pinus ponderosa), Douglas fir, lodgepole, white bark pine (Pinus albicaulis), Alpine fir, and Engelmann spruce. Lodgepole is not exacting in its soil requirements, though it does best on deep, fresh, well-drained agricultural land. It is able to make good growth, however, on shallower, poorer soils, provided a reasonable amount of moisture is available. The typical soil of the lodgepole region is gravelly, with a considerable admixture of loam in valley bottoms and open benches, but with little or none on ridges and steep slopes. Unless lightened by a mixture of sand, gravel, or loam, clays are usually not well enough drained, while limestone soils are apt to be too dry to enable the tree to make a normal growth. In the Big Horn Mountains in Wyoming, for example, lodgepole is rarely found on the limestone soils, though granitic soils immedi- _ ately adjoining show extensive areas of the lodgepole type. LIGHT REQUIREMENTS. In relation to light, lodgepole pine exhibits three striking char- acteristics—intolerence of any considerable degree of overhead shade; ability to survive for long periods in a badly crowded or suppressed condition in pure, even-aged stands; and ability to recover and make 1 Forest Service Bulletin 79, The Life History of Lodgepole Burn Forests. _ LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 7 increased growth after being released from suppression. For its best development lodgepole requires considerable light from above. With full sunlight as standard, no vigorous seedlings were found in Colorado in light values of from 0.08 to 0.05. Since the light values in mature forests range from 0.12 to 0.05, with an average of 0.08 or 0.07, it is obvious that satisfactory reproduction can not be ex- pected in such stands.1. Seedlings often start under the partial shade of moderately open stands, particularly in restricted groups in small openings, but their growth and development is slower than in the open. Full sunlight will result in the best development at all ages, provided sufficient soil moisture is available. In the order of their tolerance the species of the lodgepole region may be grouped as fol- lows: Alpine fir, Englemann spruce, Douglas fir, white bark pine, lodgepole pine, yellow pine, limber pine, juniper. Although not as tolerant as most of its associates, lodgepole is truly remarkable for its ability to live for long periods in a badly- suppressed condition in the shade of larger trees of the same species. It is this characteristic which makes dense reproduction undesirable. The extremely dense stands which follow fire will remain dense in- _ definitely to the practically complete stagnation of growth. Some stands over 50 years old have more than 50,000 live trees per acre from 8 to 10 feet high. On Buffalo Creek on the Deerlodge National Forest, Mont., in a 70-year-old stand on a north slope, a count on 1 square rod in a fairly typical situation showed a density at a rate of 101,000 live trees per acre, together with 79,000 dead ones. (PI. I fig. 2.) The “trees,” which could be pulled up like so many weeds, had an average diameter of about three-tenths inch at 1 inch above ground and a height of about 4 feet. The largest tree was 8 feet high and 1.5 inches in diameter. The wonderful persistence of the individual is shown by the loss of only 45 per cent in numbers after 10 years of crowding. This behavior of lodgepole, which is evident in Colorado and Wyoming, as well as in Montana, contrasts strongly with that of yellow pine, an area of which near Missoula, Mont., showed only 1,300 live trees per acre after 30 years in a stand which had originally numbered 3,500 trees per acre. Of the surviving trees, moreover, 310 completely Josnueunea the rest. In overdense stands of lodgepole the side branches are killed by shading for the better part of the distance up the bole. In moder- ately dense stands, however, natural pruning of the side branches is not extensive enough to result in the production of clean stems. It has been estimated that reproduction at the rate of about 8,000 seed- lings per acre is necessary to secure a high degree of natural pruning. In a stand of 1,500 to 2,000 seedlings per acre, well distributed, the lower side branches will remain small and die at an early age. Many 1 Forest Service Bulletin 79, History of Lodgepole Burn Forests, and Forest Service Bulletin 92, Light in Relation to Tree Growth. é 8 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. of these dead branches will, of course, persist for years, but they will not be large enough to detract from the value of the timber for the - purposes to which it is best suited. Even this moderate density would be undesirable, however, if the stand could not be thinned fairly — early in its life—when from 40 to 60 years old. Trees which have come up in openings in stands grow more slowly than trees which start in full sunlight, but, on the other hand, develop small side branches on the lower stem and in the end produce better timber. In a typical dense stand of merchantable lodgepoles there is usu- ally a large number of suppressed trees from 2 to 6 inches in diam- eter. These are not younger than the larger trees in the stand, as might be supposed, but are generally of about the same age. There is a general belief that lodgepole will not recover from suppression when openings are made in the stand. Recent investiga- tions, however, prove that recovery does take place and often to a remarkable degree. The photograph of the cross section of lodge- pole pine (Pl. II) shows the effect of a very heavy thinning in which the stand was well opened. This particular cross section was selected for photographing because the rings formed previous to the release are large enough to show, which is not the case In many badly suppressed trees. Another tree studied was released from suppression 16 years ago, when 94 years old. Since then its diameter has increased from 1.44 inches to 5.06 inches and its height from 15 feet to 25 feet. The rate of growth has increased from 1 inch in diameter in 67 years to an inch in 4 years and from 1 foot in height in 7 years to 1 foot in 1.6 years. After its neighbors were removed the rate of diameter erowth increased immediately, but for the first 8 years it grew in height only at the rate of 1 foot in 4 years. During the last 8 years, however, it has been growing in height uniformly at the rate of a foot a year. The rate of volume growth has increased 4,680 per cent. Another tree which, at the age of 50 years, had a stump diameter of nine-tenths of an inch and a height of 5 feet, was opened to the light by a cutting made 43 years ago. After 43 years of sunlight the tree had grown to a diameter of 6.6 inches and a height of 27 feet. The volume of wood produced in the period of accelerated growth was about 25,600 per cent more than that produced during the period of suppression. -~Even small seedlings which have been badly suppressed will re- spond vigorously when the stand is well opened. A seedling about 30 years old, three-tenths of an inch in diameter at the ground, and 91 feet high, grew to a diameter of seven-tenths of an inch and a height of 6 feet in 5 years after its release. Whether or not a tree will recover from suppression depends upon the condition of its crown at the time of release, the amount of light Bu |. 154, U. S. Dept. of Agriculture. testi m) ce eee ee a a et ie eee PLATE |. Fic. 2.—DENSE LODGEPOLE REPRODUCTION. Fia. 1.—DENSE LODGEPOLE REPRODUCTION. This stand is the result of fire. gnation in the he Note the debris from t acre, with resulting sta previous stand only partially decayed after being dead 70 years. tuated on a north slope, has approximately i The better trees bear cones. 101,000 green ‘‘trees’’ per This 70-year-old stand, s growth. soon as possible so that the It runs about 3,500 green trees per acre Many of the larger trees are suitable for lagging. The stand should be thinned as better trees left may growr apidly to stull size. and is about 50 years old. Bul, 154, U. S. Dept. of Agriculture. PLATE Il. -_e LOD GEPOLE FU a ——_ ~ ~ the P Léeriode age Wat = ems ELLECT OF 7HINI EFFECT OF THINNING LODGEPOLE. After its release this tree increased in diameter from 3.5 to 6.3 inches in 12 years. In the last 12 years the tree has been growingat the rate of an inch in diameter in 4 years, while in the previous 12 years it had been growing at the rate of an inch in 25 years. The tree has been growing 772 per cent faster in v olume in the last 12 years than in the preceding 12 years. Note the thin bark. LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 9 admitted to the stand, and probably to some degree upon the tree’s height. Tall trees with very poor crowns are often killed outright when exposed to full sunlight. The more thrifty and vigorous the crown and the shorter the tree, the surer the recovery. Trees which stand full light immediately show the greatest increase in growth. Observations made so far do not tend to show that the quality of the site has any effect upon recovery from suppression. REPRODUCTION. CONE AND SEED PRODUCTION.1 Lodgepole pine usually produces a fair crop of seed each year. Particularly abundant seed production may occur at two or three year intervals, but it is not yet possible to say whether there is any uniform periodicity in such years, as is often the case with yellow pine and Engelmann spruce. Open-grown trees produce seed at an earlier age and in larger quantities throughout life than do trees in dense stands. Seedlings in the open have been known to mature cones at the very early age of 5 years, while crowded trees in the forest may reach an age of 50 years without doing so. In somewhat open stands moderate seed production usually begins when the trees are from 15 to 20 years old. Careful tests show that seed from trees less than 10 years old have as high a germination per cent as seed from mature trees. Typical lodgepole cones vary in diameter from 1 to 2.5 inches. _ The cones are generally larger on open-grown than on close-grown trees, and tend to increase in size with the age of the tree up to its maturity. They are nearly always flattened on the side oppressed - to the parent branch. The extreme basal scales of the cone and from 3 to 6 scales at the tip do not bear any seeds, but the remainder of the scales, between base and tip, nearly always do. Seed-collecting _ operations on nine National Forests in Colorado and Wyoming show an average of about 26 seeds per cone. The number of cones per tree, and consequently the total seed production, varies greatly. Clements has estimated the average annual production of seed per tree in certain cases at from 21,000 to 50,000. Hence the total seed production of a stand may be enormous. Lodgepole is unquestion- ably a more prolific and regular seed producer than any of the species commonly associated with it. SEED DISSEMINATION. Lodgepole cones ripen in late August or September of their second year. It is a notable characteristic of the species, however, that the cones often fail to open and discharge the seed as soon as mature. 1 Detailed results of an investigation on this subject made by F. E. Clements in Colo- _ rado are given in Forest Service Bulletin 79. 62799°—Bull. 154-152 , 10 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. Sealed cones as old as 75 and 80 years have been found attached to the parent tree. Sometimes the lower part, or even the entire cone, | is embedded in the wood. Closed cones are more common on old than on young trees, and on trees growing in dense stands*than on ~ those in the open. MacDonald found on the Targhee Forest that on trees less than 55 years old five-sixths of the cones opened at ma- turity, while on trees over 55 years old only one-fourth of the cones opened. Seeds retain their vitality for many years in sealed cones, and in one case had a germination per cent as high as 8 after being locked up for about 75 years. Clements states that cones open normally as a result of the drying out of the cone scales rather than from the action of heat alone. The majority of cones capable of opening normally probably do so within a short time after maturity, and scatter their seeds while still attached to the tree. Some cones, however, after remaining upon the tree closed or only partly open for a number of years finally fall to the ground with more or less seed still in them. There appear to be two distinct periods of general opening, the first in the years immediately following maturity and the second from 10 to 13 years later. The opening during the second period is prob- ably due to the fact that the pedicel of the cone breaks about this time and the cone no longer receives moisture from the tree. - The size of the cone appears to have no effect upon the time when it opens. Tower? states that the amount of lime in the soil has a strong influence upon the time when the cones open; that on soils rich in silica and deficient in lime the majority of cones open at maturity, while on soils rich in lime they remain closed and persist on the trees for many years. Observations by other investigators in Colorado and Montana, however, indicate that this tendency is not sufficiently marked to constitute arule. Individual trees in the same stand show the most extreme differences in cone opening; one tree may have all of its cones open, while beside it another tree of the same age may have all of its cones closed; and in most cases both open and closed cones are found on the same tree. Probably the differences in be- havior in this respect observed by Tower indicate merely the general tendency of cones to open less promptly on dry soils. This tendency is also indicated by the fact that fewer cones remain closed on the moister soils and in the moister climates of northwestern Montana, northern Idaho, and the Sierras in California. The opening of the cone frees the small, winged seeds, which are distributed mainly by the wind. Other agents of seed distribution are gravity, surface drainage and streams, and such animals as squirrels and mice. The distance to which wind distribution is effec- 1A Study of the Reproductive Characteristics of Lodgepole Pine, by G. E. Tower, in Vol. IV, No. 1, of the Proceedings of the Society of American Foresters. LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. lI] tive is very apt to be overestimated. One reason for this is that natural reproduction has often been credited to wind-sown seed, when in reality the seed was already present on the area in sealed cones. Hodson, as the result of a study on a large number of cut-over areas in Montana and Wyoming, concludes that “the largest amount of seed falls within a hundred feet of the seed tree, and the radius of effective reproduction is much less than is commonly supposed.” Clements states that the distance to which seed is carried by the wind “ was never found to exceed 164 feet.” Undoubtedly the dis- tances seeds are carried varies considerably with the topography and the situation of the seed trees. Trees on a ridge exposed to high winds will distribute seed the maximum distance. Until more definite in- formation is available, it is safe to assume that wind distribution ~ should not be relied upon for distances of more than 150 to 250 feet, according to the character of the situation. REQUIREMENTS FOR NATURAL REPRODUCTION. Owing to its intolerance of overhead shade, lodgepole pine will not reproduce satisfactorily without considerable direct light. Although _the seed will germinate with a vary small amount of light, the young seedling soon dies without it. In mature stands a heavy thinning which reduces the crown density to about one-half is usually neces- sary to permit a fair amount of reproduction to start and thrive. Where the stand is opened by the removal of groups of trees on areas of 3 or 4 square rods or more, reproduction will usually start and erow well in the openings. Reproduction starting in this manner is more apt to be uneven aged and better divided into height classes, and consequently in less danger of stagnation, than in the dense, even aged stands of uniform height which so often follow fire. Vigorous young growth has been observed under stands in which a heavy and uniform thinning had been made, causing the forest to resemble one undergoing regeneration by the shelterwood method. In stands of only moderate density, however, seedlings are apt to be spindling and slow of growth. The most favorable seed bed for germination of lodgepole pine seed is a mineral soil with plenty of available heat and moisture. Needles and undecayed humus are apt to dry out rapidly in the spring, before the rootlets of most of the seedlings can reach the mineral soil. That mineral soil is not always necessary for germina- tion, however, is shown by the fact that on old cuttings in Montana where there has been no fire, seedlings apparently start indiscrim- inately on patches of mineral soil and in small clumps of pine grass 1 Silvical Notes on Lodgepole Pine, by E. R. Hodson, in Vol. III, No. 1, of the Proceed- ings of the Society of American Foresters. 12 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. (Calemagrostis rubescens), the latter usually not more than 8 or 10 inches high. Furthermore, in full sunlight even mineral soil may — dry out so rapidly that many of the seedlings will be killed by drought. For this reason young stands are usually more dense on mineral soil lightly shaded by recently fire-killed trees than in the open. On the other hand, they are likely to be more open on sandy soil than on soils better able to retain moisture. The densest seed- ling stands are apt to occur on north slopes where there is a rela- tively small amount of direct sunlight and a large amount of moisture. | Competition with other native vegetation, such as blueberry (Vac- cimium) and kinnikinnic (Arctostaphylos), for light and soil mois- ture often greatly reduces the amount of lodgepole reproduction; and the seedlings which do start have a much slower growth than where there is no competition. Aspen also is a hindrance to lodge- pole, through its more rapid growth when young, wherever the two start on the same area. A light; overhead aspen cover, on the other hand, may be beneficial by protecting the soil. Rodents reduce the seed supply to a certain extent, but there is probably always enough seed left for satisfactory reproduction if other conditions are favorable. > OPTIMUM DENSITY. The right density for a stand of lodgepole is that at which the lower branches become suppressed and die while still small, but with- out overcrowding of the trees and consequent decrease in rate of growth. Hodson concluded that an original density of 8,000 seed- lings per acre is required to produce clean stems at maturity. Later investigations show, however, that while this number of seedlings would secure good natural pruning, it would be at a great sacrifice in diameter growth. In the reconnaissance work on the Deerlodge Forest a “normal” seedling stand is considered one of about 1,000 trees per acre, fairly well spaced and of fairly even height growth. By “normal” is meant that degree and character of stocking which. will produce the maximum yield of merchantable timber of the de- sired sizes at the end of the rotation. Stands containing too few, or too many, unevenly distributed trees, are abnormal to the extent to which they will fail to produce this maximum yield. Normality is” thus seen to differ materially from “density,” which refers to the extent to which the crown space is fully utilized. Stands with a density of 1.0 are nearly always too crowded for the most satisfac- tory development. The number of trees constituting a normal stand naturally de- creases with the age of the stand. While 1,000 trees per acre, evenly spaced, is a satisfactory stocking when reproduction first starts, this PLATE III. 154, U. S. Dept. of Agriculture. Bul. os eter: ieee PNT W ae om pr TE .* x Pt) SeQas > w* %, “S ee = ies ead oe 5 Oa Me ee ~~ Fic. 1.—LODGEPOLE TIMBER. Heavy stand of overmature stull timber about 200 years old, Deerlodge National Forest. pis bee Nailin: & i a ihe % . 3 ra t Pa ee a ie 7 J a PIR 7 “e ie fae / . ren: ! by) ¢ f pf ? ita & }) wana Ba Oks ead avte aw SN Meese Lies Sensi wg CA, news sree ni rare Ph gow * FIG. 2.—WELL-DEVELOPED YOUNG LODGEPOLE. The thinning was made although at that time the density was feet per acre. 0 trees per acre. 5 ees per acre stand now has-3,200 board earsago, which removed about 250 tr The about normal. ae stand is 60 years of age and now has about 2 v7 Bul. 154, U. S. Dept. of Agriculture. Fic. 1.—LODGEPOLE REPRODUCTION. In the center of the picture is a 20-year-old stand of lodgepole on an old cutting. PLATE IV. No fire has been over the area. The whitestreaks mark the location of the original windrows of brush only partly decayed. Fic. 2.—LODGEPOLE REPRODUCTION. Well-distributed seedlings coming up without fire on a cutting made 10 years ago. about 500 per acre, a density nearly ideal. The stand is LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 13 should be reduced to about 500 at the end of 30 years, to about 300 at the end of 90 years, and to about 250 by the one hundred and fortieth year, when the stand may be considered mature. Unfortu- nately, owing to the low mortality rate of lodgepole pine, a stand of 1,000 evenly distributed seedlings 10 years old will not, by natural means, be reduced to 500 at 30 years, 300 at 90 years, and 250 at 140 years. Ordinarily this could be brought about only by thinning. Tf, however, the stand is sufficiently open to arrive at maturity with 250 stems per acre without thinning, decidedly limby trees will be the result. On the other hand, a stand of 1,000 well-spaced seed- lings 10 years old, at which age a stand may be considered as established, probably will have about half that number of trees at maturity. In such a case those of fairly good form and diameter may be cut and the others left to grow for an additional period. Seedling stands of from 300 to 500 plants per acre are preferable to those of 8,000 or more, even when thinning is possible, since for many years the latter will not produce material which can be taken out with profit in the course of thinning. Thinnings, moreover, will probably be impracticable, except in a few localities, and for this reason from 300 to 500 seedlings may generally be considered preferable to 2,000 or more. A good volume of limby timber is better than a large number of poles; besides, the spaces in an open stand will gradually fill in with individuals of a more satisfactory form. Where thinnings are practicable a density of about 2,000 plants at the start is best. Plate ITT, figure 2, shows a well-developed - 60-year-old stand of lodgepole of something less than normal density. It should be borne in mind that the figures for density given in the preceding paragraph are more or less arbitrary, and in deter- mining the normality of a stand as much attention should be given to the spacing and height growth as to the-number of stems. A relatively large number of trees per acre is not undesirable, provided there is enough variation in the height of individual trees to pre- vent stagnation of growth. The production of clean stems is of comparatively little im- portance, since lodgepole is used mainly for mine timbers and rail- way ties, and in the future is not likely to have additional uses other than for telephone poles, pulp, and common lumber. Of far greater importance than clean stems are rapid growth and the production of large-sized timber. Lodgepole is slow-growing, and there is always an abundance of trees of small size. Ordinarily there is far greater danger of overstocking than of understocking. Ob- servations on 40,585 acres of young growth on the Deerlodge National Forest show 78.7 per cent of the entire area to be over- stocked, 20.5 per cent understocked, and only 0.8 per cent normally stocked. 14 -BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. EFFECT OF FIRE. Fire has been one of the most important agencies in the reproduc- tion of lodgepole pine. Its effect is fourfold: (1) By softening the > resin and drying out the cone scales it opens the sealed cones’and - makes available the accumulated seed production of many. years; (2) by reducing the density of the ground cover it admits plenty of light; (8) by exposing the mineral soil and removing the ground cover it prepares a favorable seedbed; (4) by killingand driving away for a time the rodents and birds it saves the seed from being eaten. Thus aided by fire, lodgepole has been able to replace to a consider- able extent all the species within its range, since these usually pro- duce seed in abundance only once in several years and discharge it immediately. Most of the extensive lodgepole stands now in existence have come in as a result of fire. On the other hand, areas formerly covered with lodgepole have been made barren by “ double burns,” where stands of young growth which followed the first fire have been destroyed by a second one before they were old enough to produce seed. Areas of this kind on which all of the trees have been killed will not reforest naturaliy for many years, since the only way repro- duction can take place is by seeding from the sides. Fire in a mature stand is usually followed by too dense a reproduc- tion to permit the most satisfactory development of-the young trees. Sample plots on the Gallatin National Forest, Mont., show repro- duction after the fires of 1910 with a maximum density of about 300,000 one-year-old sedlings per acre. On the Deerlodge National Forest stands following fire have been found which, at the age of 8 years, had a maximum density of about 175,000 live seedlings per acre, averaging about 2 feet high. Ten small sample plots on the Arapaho National Forest, Colo., in a 22-year-old stand, showed an average of nearly 44,000 trees per acre. These figures, of course, rep- resent maximum densities on small areas, but as extreme illustrations they show that severe overstocking is more than likely to follow fire. The effect of fire on cut-over areas may be very different. Where all the trees have been felled and the brush piled in windrows—a practice in many private operations—a fire in the slash may be fol- _ lowed by reproduction of moderate density. Such a fire usually de- stroys all the seeds in the windrows, the locations of which are marked by the absence of reproduction, while a moderately dense stand starts in the intervening spaces from cones which did not get into the windrows and thus escaped destruction. On unburned, cut-over areas reproduction is apt to be much less dense, and therefore more satisfactory than in the case of burned- over uncut stands. Throughout the Rocky Mountains are thousands of acres of old cuttings, untouched by fire, upon which the repro- duction is decidedly satisfactory. This is-especially true of the Deer- lodge Forest, near Butte, Mont., where it is unusual to find an old La LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 15 eutting on which reproduction is not taking place. Observations on 32 separate tracts in the 20 and 30 year age classes on this Forest show a far more satisfactory reproduction on unburned cut-over areas than where stands have been killed by fire. On many clean-cut areas which have been left practically without seed trees reproduction has taken place solely from cones which remained on the ground after logging. Nearly all mature trees bear a considerable number of per- sistent, closed cones, some of which fall on the ground when the tree is cut, while others remain attached to the branches. These gradu- ally open and drop their seed, resulting in fairly uniform reproduc- tion if the brush is scattered. If it 1s piled in windrows, which decay very slowly, the spaces so occupied will not reproduce. (Plate IV, fig. 1.) Where the stand is not cut clean, or where clean-cut only over small areas, seed comes from above or from the side, as well as from the cones left on the ground and in the tops of felled trees. Sample plots in an unburned stand on the Arapaho National Forest, measured six years after the removal of about one-half of the original trees for ties, showed an average of 6,000 seedlings per acre, of which 3,500 had started since the cutting. Even with the same number of seedlings per acre reproduction is apt to be more satisfactory on an unburned than on a burned area, since the young growth comes in more gradually, giving trees of different heights and so materially lessening the danger of stagnation. The greater part of the reproduction which comes in after either fire or cutting usually starts within a comparatively short time. The following figures, which represent averages obtained from 181 small sample plots, both burned and unburned, in Montana and Wyoming, show the proportion of reproduction which came in during each 5-year period for the first 80 years after the stand was opened up: Per cent. LES ES oe oe leat ENR a 69.5 OSES ELG ENE SYS S a ees fae BE EAN SR ice He em a 21.0 A Ver Venn s oie Pin jet a nes Sis 3 il go aa pen ae 5.4 TEES LEAR AVES STS RE ace a er 9 USI Reema hh eng Se 2. 5 EB ES St a ill Ea ES ee 2S eee ee Mi 100. 0 It will be seen that nearly 70 per cent of the reproduction started in the first 5 years and over 90 per cent in the first 10 years. Unfor- tunately, it is not possible to separate the figures for burned and unburned plots. Similar observations on a 9-year-old burn on the Arapaho National Forest showed over 49 per cent of the reproduc- tion to have started in the first four years and nearly 75 per cent in the first six years after the fire. In most places the character of the seedbed is so changed in the 10 years following a cutting or fire by 16 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. - the formation of a thick sod of grass that comparatively few seed- lings are able to gain a foothold after that time. ae GROWTH. The rate of growth of lodgepole varies greatly with the quality of the site and the density of the stand. Other conditions being the same, the most rapid growth takes place on the best sites, but over- stocking often reduces the rate of growth in such situations to a point at which it is considerably less than in more normally stocked stands on poorer sites. The effect upon growth of the density of the stand is discussed under “ Factors influencing yield.” On account of the wide variation in lodgepole’s rate of growth, it is impossible to give figures which will be universally applicable. Table ‘2 shows what may be expected under certain conditions. The data were obtained from 468 average trees cut by the arbitrary group method in the course of a yield study on the Deerlodge Forest, con- ducted in fully stocked stands on sites better than the average for that Forest. Since the stands were approximately fully stocked, and in some cases overstocked, the diameter growth shown is somewhat less than that which may be expected in the case of trees growing in stands of moderate density. On the other hand, since the sites were better than the average, the height growth shown is somewhat above the average. TABLE 2.—Average growth of lodgepole pine in fully stocked. stands on the Deerlodge National Forest, Montana, on slightly better than average sites, based on 468 average trees, of which 158 were dominant. Pee wiche ar Height. Volume. Age in years. 4 | Average | Doms Average Den Average ee Average Poult, trees. Z trees. _ trees. trees. a trees. trees. trees. trees Board Board Cubic Cubic Inches. Inches. Feet. Feet. feet. fect feet.2 Seet.2 Oa es er 0.4 0.5 3 ’. amie ay Coen mR NRE Od RE oa eee we ena PE 8 tl P/V ee es Sa i eee 2 1.9 10 1D ae ee ae ee Ae oe ee | ee ee eee See eo se ee eee Peek By 19 20) ee cl Sica Berets | ee ete 0.5 ile AQ RN WE oN er = 3.0 4.4 27 BD: taal eet See ee | ee te 9 2. CTU a Las oo ras Sete 3.8 5.6 33 BS. Sales Sees | eeeaeee 1.5 3. COR ee eee 4.5 6.6 38 7. Vasa ie espe ea 5 PAA | 5: NO See Sora ASS aes 5.2 7.4 42 AGG tae ee 20 3.0 “ls RO eae Ss Se ae eyes 5.8 8.2 47 OAS ies Shee: 35 4.1 9. ee ae ae 6.4 8.9 51 58 5 45 6.2 12. O02 See ae ee 6.9 9.5 54 62 20 60 8.6 15. IO Ree ene oe 7:4 10.1 58 66 30 75 10.0 18. AZO ere oa ae oe 7.9 10.7 61 70 40 90 11.4 2a. P3022 ees oat Sec ee SR Sete TD, 65 ke 50 105 UBB) 26. TAQ SS Ee Pe oe ee eee 8.7 11.8 68 76 60 120 15e5 30. 150) ee aS ees 9.2 12.3 (Al 79 70 135 18.0 34. AGO Sor ete a ee oe 9.6 ADS 74 81.5 80 150 20.0 39. 17 (Vb oe eae ee as Se 10.0 gy a 77 84 90 170 22.0 44. TOS Soe = OE ae 10.4 13.8 80 86.5 100 190 24.2 49. OO Se ee ee foe 10.8 14.3 83 89 110 215 26.5 54. Uh Deen ee ae aes HAE 14.7 85 91.5 125 240 30.0 60. 1 The board foot volume is based on a minimum log of 6-inch top diameter and 16-foot length, scaled by the Scribner Decimal C rule. 2 The cubie foot volume includes only the usable portion of the trunk from above the stump, usually from 6 to 10 inches high, to a diameter of 3 inches in the top. LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 17 This table shows how comparatively slow is the growth of lodge- pole pine. One of the most striking points brought out, however, is the relatively rapid growth of the dominant trees, particularly in volume, amounting to approximately twice that of the average tree. This indicates clearly the need for sufficient growing space if the maximum development of individual trees is to be secured. Measurements which would permit of comparison between the rate of growth in Wyoming and Colorado with that in Montana are not available. Table 3, however, shows the diameter growth by decades on two widely separated Forests in Wyoming, the Medicine Bow and the Bighorn. In both cases the growth is typical of the average sites on which the bulk of the lodgepole forests of the region are found. Since in this case the measurements were collected by fol- lowing the sawyers through the woods, the data secured represent the growth of trees of more than the average diameter, since only the larger timber was cut. Also, the stand on the Medicine Bow was probably denser than on the Bighorn, which accounts for the slower rate of growth upon the former. On similar sites, and with the same stand density, the rate of growth for the two Forests would probably be about the same. TABLE 3.—Average diameter growth of lodgepole pine on average sites on the Bighorn and Medicine Bow National Forests, Wyo. Bighorn Medicine Bighorn | Medicine National Bow National Bow Forest. 2 Forest. 8 Forest .2 Forest.3 Age in years. pba A PL nO Age in years. Diameter | Diameter Diameter | Diameter breast high. | breast high. breast high. |breast high. Inches. Inches. Inches. Inches. 2 Let 5 ae ne hae ee lee OE SniL 20 eb yavais eee re ah ol eteress 10. 7, Wet SA EO ee Ss ol 5 ee ae 3.0 UG | ISOS sas aR eee ae ial 8.2 DE ace Be ate See OEE ee 4.4 DeBus UAOe aps pee sent ee 11.6 8.6 OLA 5 Sees Ben se ee bere S307 bi 3108 See aren er ae ae 12.1 9.1 TGA Oe eee ee 6.7 BAS INGO cre ators opel ite, oper se aa 12.5 9.6 (U2 Aas nS ee Bae ee 7.6 BLOM WO eaters cere ea eee eevee te 12.8 10.0 ‘ah ES ae ee ee 8.4 AOI USO Cee see eee ee ND 1B}, 97 10. 4 pee ete eee set LS 9.1 GZ ELOO Piet stesso se kecciclaee 1355 10.8 RR errata See Ge AR 9.7 Dhol hel0 Us newtnae ic ae Seoe ese 13.8 rei LI Saas hCe ee 10.3 7.2 1 From Forest Service Circular 126, ‘‘ Forest Tables: Lodgepole Pine.”’ 2 Based on decade measurements on 49 stumps of various heights, 72 to 340 years old. 3 Based on decade measurements on 430 1-foot stumps, 159 to 300 years old. The growth in height of young seedlings in Montana and Colorado is shown in Table 4. Figures for Montana are based on measure- ments of 86 trees on the Deerlodge National Forest made to deter- mine the average age required to reach various stump heights; figures for Colorado are the results of measurements of reproduction on a burned area on the Arapaho National Forest. In the white-pine region of Northern Idaho lodgepole makes a more rapid height growth in the seedling stage than does any other species, with the 62799°— Bull. 154—15——8 18 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. possible exception of larch. Lodgepole seedlings from 5 to 7 years old with leaders 36 inches long have been noted. In one case a young tree, about 8 years old, had made a height growth of 74 feet in the last 3 years. Another young tree of about the same age had a-45-inch leader. TABLE 4.—Average height growth of lodgepole pine seedlings on the Deerlodge National Forest, Mont., and the Arapaho National Forest, Colo. ; Height. | Height. | 5 : f Age in years. Deerlodge | Arapaho | Age in'yeals. Deerlodge | Arapaho National National || National National Forest. Forest. ; Forest. Forest. Feet. Feet. Feet. Feet. seas RA ae see ee een Qu ee SSeS eee as Mee See 0.8 1.4 52 BCR ac 2 ck ee Ye an PRES shape NC EO 5B. cata I oe ice ae aii 1.0 1.9 Si pS TE are CC aeae s Spo tee 0.4 4 | i A) Messer pee ea ok US ES aisles a eh en a 4.5 BS pees Sh eee apes 2 .6 9 | 1 Netaaeet Sao eae case Wine Rivers ce ler 7.9 The growth figures so far given all apply to unthinned stands. If it were possible to make thinnings when needed that would favor the best trees, the growth of the latter would undoubtedly equal, or even considerably exceed, that shown for the dominant trees shown in Table 2. Such intensive management, however, could be under- taken only in a few favored localities where the market is unusually good. Lodgepole pine stands have been thinned in the past only in the course of ordinary lumbering, which has usually left the smaller, poorly developed trees, many of which could take no advantage of the operation. That even trees of this character often respond to such haphazard thinning with a remarkable increase in rate of growth has already been stated. Out of 91 average trees measured on the Deerlodge Forest, representing those which remained when the surrounding stand was cut, 54 trees, or 59 per cent of the total number, showed a marked increase in growth, while the remainder, or 41 per cent, showed no increase. Differences in rate of growth before and after cutting are shown in Table 5. TABLE 5.—Effect of thinning; average diameter growth of lodgepole pine trees left after cutting, Deerlodge National Forest, Mont. Part I. [Based on 91 trees, irrespective of whether they showed increased growth or not.] Periodic annual diam- eter growth for 20 Time required to grow 1 inch in diameter. Diameter years. breast Trees. high. Before After Before After thinning. | thinning. | thinning. | thinning. Inches. | Number. Inch. Inch. Years. Years. 3 8 0.028 0. 034 36 29 4 10 j - 031 . 042 32 24 5 15 . 037 . 039 27 25 6 17 - 051 . 041 20 24 7 at Cs | - 047 . 057 21 18 8 15 | 059 064 17 15 9 6 | 050 .046 20 | 21 10 S| -058 | . 094 17 18 LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 19 TABLE 5.—LHjfect of thinning; average diameter growth of lodgepole pine trees left after cutting, etc.—Continued. Part II. [Based on the 54 trees which showed an increased growth. Periodic annual diam- eter growth for 20 | /imerequired to grow | Rate of Diam- years. 1 inch in diameter. increase in oter Trees volume breast ° a a iT at CC CLONL LL high. Before After Before After pce thinning. | thinning. | thinning. | thinning. mS: Inches Number. Inch. Inch. Years. Years Per cent 3 5 0. 029 0. 045 34 2 140 4 6 . 030 050 33 20 169 5 7 . 023 049 43 20 127 6 8 . 029 039 34 25) 59 7 13 . 038 061 26 16 112 8 9 . 047 072 21 14 98 9 4 . 027 042 37 24 70 10 2 . 022 047 45 21 125 CAUSES OF INJURY. FIRE. Fire has been the most important agent in the destruction of lodgepole pine forests, as well as in their establishment. Though in some places it has enabled lodgepole to take possession of the ground, in others repeated fires have practically eliminated forest growth. Lodgepole pine is less susceptible to fire than Engelmann spruce and Alpine fir, but more susceptible than the other pines with which it grows or Douglas fir. Its susceptibility is due chiefly tq its thin bark, which at stump height is only from two-tenths to four-tenths of an inch thick. Fire is most destructive in dense young stands of “jack pine,” as the young trees are often called. Crown fires are in- frequent, but may occur with high winds or when a large amount of débris litters the ground. When a lodgepole stand is killed by fire a period of from 15 to 30 years elapses before the dead trees fall to the ground. Fire-lilled timber does not completely decay until from 60 to 120 years after the fire. Such débris, of course, greatly increases the fire danger in a new stand. In comparatively open stands which have reached maturity with- out being burned over there is usually not much débris on the ground and consequently less danger of crown fires. Even here, however, there is in most cases a ground cover of grasses, weeds, needles, and similar litter to invite surface fires, which destroy reproduction, occasionally kill mature trees, and seriously injure the butts and lessen the vitality of many others. These ground fires, too, by de- stroying the organic content of the soil, reduce both its water-holding power and its productive capacity, which necessarily results in de- creased growth of the surviving trees. 20 BULLETIN. 154, U. S. DEPARTMENT OF AGRICULTURE. INSECTS. Although lodgepole pine in the Rocky Mountains has not suffered | severely from insect attack in recent years, bark beetles have un- doubtedly killed more mature timber than has any other agency — except fire. In Montana the mountain pine beetle (Dendroctonus monticolae Hopk.) has done some damage in the vicinity of Swan Lake on the» Flathead National Forest, and in 1911 an aggressive attack by this beetle in the Big Hole Basin on the Deerlodge and Beaver Head Forests developed serious proportions.t. In that year approximately 15,000 trees were killed on an area of about 1,500 acres. On some portions of the area practically all the trees over 5 inches in diameter were either killed or badly infested, while on the remainder of the area the attack was confined to the larger and less vigorous trees. The attack appeared to radiate from several centers where the damage was particularly severe. It appears likely that this infestation resulted largely from injury to the trees by adverse weather conditions during the winter of 1908-9, the in- sects taking advantage of the trees’ weakened condition. The un- usually dry summer of 1910 was also thought to have favored the attack. Fortunately many of the insects were destroyed during the winter of 1911-12, apparently by winter killing, to which the thin bark of lodgepole renders them lable. In regions other than the one considered in this bulletin, damage by the mountain pine beetle has been very severe. On the Wallowa and Whitman National Forests in eastern Oregon it has recently killed 100,000,000 board feet of lodgepole. Here the infested area, which in 1906 covered only about a section, had by 1912 grown to approximately 320,000 acres, and the beetle was then extending its attack to yellow pine. The presence of the mountain pine bark beetle is first made evident by pitch tubes, boring dust, and woodpecker work. Most of the adult beetles emerge during August, and by early fall are well estab- lished in their new hosts. The trees thus attacked usually remain green until the following spring, when their tops first turn a yel- lowish and then a reddish color. By the time the red-top condition is reached practically all the beetles have left the tree. The species apparently prefers to attack injured and felled trees; the more vigorous, and particularly the younger trees, are often able to drown the beetles in exudations of pitch. Thrifty trees, however, are some- times Inlled. In Wyoming and Colorado the most common insect enemy of lodge- pole pine is the lodgepole pine beetle (Dendroctonus murrayanae 1 For a complete description of this and other bark beetles of the genus Dendroctonus, together with methods of control, see Bureau of Entomology Bulletin 83, Part I, by Dr, A. D, Hopkins: LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 21 Hopk.). A few trees apparently killed by its attack have been found on the Medicine Bow and Bighorn National Forests in Wyoming, and on the Arapaho Forest in Colorado. The attack was confined mainly to the bases of the trees and to unhealthy individuals. The Oregon tomicus was also found, but it is probable that the dendroc- tonus made the first attack. A weevil similar to the eastern white pine weevil (Pissodes strobi) has also been found on the Arapaho National Forest. This insect destroys the terminal shoot, resulting in crooked and forked trees. FUNGI AND MISTLETOE. Lodgepole has, on the whole, suffered comparatively little damage from fungi. This is due chiefly to the dry climate of its range and to the fires which have renewed the stands from time to time, thus preventing any extensive development of the fungous diseases. Often badly fire-scarred trees may remain sound as long as 40 or 50 years, except for a small amount of blue stain along the edges of the scar. One of the two most common diseases of lodgepole is that caused by the ring scale fungus (Zrametes pint), often called by woodsmen “ white rot” or “red rot.” Another common disease is caused by the fungus Polyporus schweinitzi. The ring scale fungus attacks chiefly the older trees, which it may enter at almost any point where a dead limb or wound affords an opening. From the point of infection it sometimes extends throughout the trunk. The wood at first turns a dark reddish brown, the trees at this stage being known to lumber- men as “red rot” or “red heart” timber. Later the color of the wood becomes lighter and small white spots and strands appear, increasing in size and number until the entire heartwood is filled with small holes lined with the thin, white cellulose of the wood which has not been used as food by the fungus. The wood never rots entirely away, but eventually becomes a mass of soft, spongy tissue. The fungus Polyporus schweimitzt%i usually causes a heart rot at the butt. Since it is confined to the first or second logs it is less destructive than the ring scale fungus. When the roots are infected _ the tree may fall;‘in other cases it may break off close to the ground _ before the rot has had time to spread far into the trunk. The affected wood turns a light yellow and gradually dries out so that numerous fissures appear. In overmature lodgepole stands from 7 to 10 per cent, or on limited areas even 15 to 20 per cent, of the timber may be affected by one or both of these fungi to an extent rendering it unmerchantable. It is seldom, however, that an entire tree is made worthless by rot, and one or more sound logs or ties can usually be obtained. The blue stain, which may appear almost immediately in the sapwood of fire-killed _ or insect-killed trees, does not render them unfit for use. 22 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. In some localities a rust (Peridermium montanum) attacks the leaves of lodgepole, causing them to fall prematurely. Another rust (Peridermium harknessti) attacks lodgepole in western Montana, © causing galls to form on the trunk and branches, which stunts-and — sometimes kills the tree. One of the false mistletoes (Razowmfskya americana) is often found on lodgepole, but does little serious damage except in certain localities, where it may greatly affect the growth of the tree. It usually attacks young stands, and in dense ones most of the trees may be infested. Mistletoe causes an abnormal growth at the point of attack, which on side branches forms a compact, bushy mass of twigs commonly called “witch’s broom.” In small trees infested stems or branches are sometimes swollen to twice their natural diameter. SMELTER FUMES. The Washoe smelter at Anaconda, just outside of the boundary of the Deerlodge National Forest, is the largest copper smelter in the world, handling approximately 10,000 tons of ore daily and pro- ducing 25 per cent of the copper output of the United States. Chem- ists have estimated that at least 2,500 tons of sulphur dioxide and at least 25 tons of arsenic trioxide are daily thrown into the atmosphere from the top of the stack. The arsenic does not damage the timber, but when deposited on the forage is injurious and sometimes fatal to grazing animals. Sulphur dioxide is injurious to vegetation in general. Experiments have shown that as little as one part of sul- phur dioxide with a million parts of air will lull pine seedlings when the trees are exposed for any length of time. Even at a distance of many miles from Anaconda the air in the smoke stream may contain as many as 80 parts of sulphur dioxide to a million parts of air. At a distance of 10 miles from the smelter the sulphur is often so strong as to cause persons to cough. Sulphur dioxide injures trees by destroying the chlorophyll in the leaves, which first turn yellow and later red-brown. The damage usually extends over several years, especially if the trees are at some distance from the smelter. At first only the weaker leaves are lulled, but later the younger ones succumb to repeated baths in the smoke stream. Three stages in the defoliation of trees by smelter fumes have been recognized. The first is when the older leaves die and fall — prematurely, the tree still retaining a considerable amount of foliage and the appearance of health. In the second stage the foliage be- | comes decidedly thin, and in the last or acute one only the needles of the current year are left green on the tree. (Plate V, fig. 1.) - These latter are usually badly damaged or killed during the winter, and the-tree may fail to put forth fresh leaves in the spring. In some cases, however, the acute stage lasts for several years. The an- LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 23 nual rings of trees injured or killed by smelter smoke usually show a graduated decrease in size for the last six or eight years. With respect to their susceptibility to injury from smelter fumes, the species in the lodgepole region may be grouped as follows, the most easily killed coming first: Alpine fir. Douglas fir. Lodgepole pine. Engelmann spruce. Juniper. Limber pine. As between Douglas fir and lodgepole pine, the two most impor- tant species in the smoke zone, the former is considerably more sus- ceptible than the latter. Nearly all the lodgepole trees will remain green when practically all the Douglas firs in the same locality have been killed. Susceptibility varies among different individuals of the same species. A few green and flourishing Douglas fir trees will often be found after practically all the other firs in the vicinity have been killed. The injury is not the same in amount at all places equally distant from the smelter, since the smoke is carried by the prevailing wind along channels formed by the topography. Damage decreases both with distance from the smelter and distance from the main channels. In places the smoke seems to eddy in a peculiar manner, killing trees in isolated groups. The greatest damage, of course, is close to the smelter, but at places 9 miles distant most of the lodgepole is now dead and the remainder seriously injured. Slight damage at a dis- tance of 30 miles has been observed. WINDFALL, SUN SCALD, ETC. Lodgepole pine is generally regarded as being decidedly susceptible to windfall. While to a certain extent this is true, there is a tend- ency to exaggerate the danger. The extent of the development of the tree’s root system, as in the case of any other species, varies with the soil conditions and the density of the stand. On deep, fresh soil trees in moderately open stands develop good root systems, while on very shallow or very moist soils the root system is correspndingly shallow and the tree less wind firm. With the same soil conditions, the development of the root system varies inversely with the density of tlfe stand, so that the denser the stand the less windfirm are the individual trees. Experience shows that heavy thinnings in dense stands are very likely to result in serious windfall unless the situa- tion is well protected. For this reason the leaving of seed trees, either alone or in small groups, seldom works satisfactorily. On the more exposed situations, with shallow or wet soil, even unthinned 24 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. stands may be blown down. As a rule, however, solid stands, even when overdense, are windfirm, provided they are of sufficient ex- tent—not narrower than the height of the trees. Light or even heavy thinnings can usually be made without danger of windfall by con- forming the operation to the height, age, and density of the stand, the character of the soil, and the exposure. Haphazard thinnings made on the Deerlodge Forest from 13 to 25 years ago in the course of ordinary lumbering operations show a remarkably small amount of windfall. On only 2 of the 18 blocks examined was any windfall evident, and in each of these cases the stand had been very heavily thinned by the removal of 82 per cent of the original number of trees and 66 per cent of the cubic volume. On the remainder of the areas the stand was not so heavily thinned, though the cutting was heavier than would be considered advisable — in present-day Forest Service timber sales. In one of the early For- est Service sales on the Deerlodge Forest, on an area partly exposed and partly protected from the wind, where the soil was deep, fresh, and firm, a selection cutting removed about 40 per cent of the total number of trees and 59 per cent of the cubic volume. In the five years following the cutting only 3 trees out of the approximately 5,000 left blew down. All of these were on the exposed portion of the sale area, and in each case a defective root system, due to fire injury, was the main cause of the fall. These and other observa- tions indicate the importance of removing trees with defective root systems. Another climatic factor which may cause damage to individual seed trees is sun scald. In many cases seed trees which have with- stood the wind for a number of years have died apparently as a result of too great exposure to sun. Owing to the thin bark of lodgepole the cambium on the insolated side of the tree is killed first. Many of the trees crack open on the sunward side before they die. The drying out of the ground when it is exposed to the sun probably helps to kill such trees. If trees are left so that their trunks do not receive full sun during most of the day, the likelihood of damage from sun scald is very small. ~ Frost cracks sometimes appear in lodgepole pine, and when they take a spiral form lessen the value of the tree for saw timber. Strong — winds sometimes open these cracks in a way to form large seams or checks which afford ready entrance for insects and fungi. _ The damage appears to be more prevalent in overmature than in younger stands, and is more often encountered in Wyoming and Colorado than in Montana. Frost may also cause injury by heaving 1 or 2 year old seedlings out of the ground. Snow, accumulating on the tops of lodgepole trees 4 inches or less in diameter, especially when in dense stands, often bends the ; ? | PLATE V. Bul, 154, U. S. Dept. of Agriculture. ‘ulojS 94} Worf poddorp sARy plo siv9k do1IY] UVY] OLOU SOAVT OU} JO []B Vey OSTY ‘s001] PoIN(Ul-lo] [OWS YJLTA PorRduUloOd SB YIMOIS Sivdt O01) ISB[ UO OSBI[OJ JUBLINXNLAION ‘opBuL sBVM oinqord 9} I1OJO SUOSBIS SUIMOIS JIIY} PolInd900 oSvVUINp OU, ‘Q3Y3SA003Y FONIS LNG «'L139g a3y,, Ad G39VNVQ YNITGSS§ 310d39007—"g "DI ‘LOJ[OUIS Ol] ULOL OUIT LIV UV UL SOTLUT 6 UIYBL ‘SoPOUBA JOS|TLOY AM UdOAM Od VOUBISIP oJIOYS Aq UMOYS SIBAA MOF JSBl UL YIMOLS FUSLO JO OVI SUISBIIO -aq “avoad JUOLIND OY} JO VBYY ALUO ‘OSBILOF VUBOS OY} OJON "BOVLS «SLNOY,, NJ “SHOWS YALTAWS AG GAYNNPN] SONINGSSS 310d39007q—"} “dI4 LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 25 poles to the ground or breaks them off at a height of from 10 to 20 feet. Snow-break may be beneficial in overdense stands which are in need of thinning, but may also do considerable damage in thinned stands where the individual trees can no longer rely on their neighbors for support. The so-called “xed belt” injury is manifested by the sudden red- dening and subsequent death of practically all the needles on the exposed portions of the trees in a well-defined altitudinal belt. Some are killed outright, though usually the buds remain uninjured and the trees later recover, in some cases after complete defoliation. The most extensive damage of this nature on record occurred in Jan- uary, 1909, when large areas were affected in the Black Hills and throughout the Rocky Mountains from Montana to Colorado. The belt was generally from 200 to 400 feet in width between elevations of 6,500 and 7,000 feet in the lodgepole region, and at lower eleva- tions in the northwestern portion of Montana. Trees on all aspects were affected, but the greatest damage was done on southerly slopes and in situations exposed to the wind. The injury resulted from un- usual weather conditions during the winter. In 1909 it was caused by a chinook of several days, when the ground was frozen and cov- ered with snow. The air was quite warm and the sun very hot, especially when reflected from the surface of the snow, causing the leaves of the trees to transpire all of their available moisture. Since the roots were frozen and additional moisture could not be obtained from the ground, the leaves withered, and in some cases the buds also dried out excessively. The most satisfactory explanation of the occurrence of the injury in an altitudinal helt is that early in the winter, before the ground froze, snow fell at the higher elevations above the zone of injury. Later the ground in the belt froze solid, but not the ground in the zone below it nor that in the zone.above it. Later still the entire area was covered by a heavy fall of snow. In this way the belt was the only part of the region in which the ground was solidly frozen and no soil moisture was available to replace the water transpired by the leaves. Hedgecock grouped the species of the lodgepole region in respect to their susceptibility to this injury as follows, naming the most susceptible first: Yellow pine. - Douglas fir. Lodgepole pine. Limber pine. Engelmann spruce. Alpine fir. Juniper. Douglas fir unquestionably suffered more than did lodgepole on areas where the greatest damage occurred. Many Douglas fir 26 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. trees were killed outright, while even those lodgepoles which had their leaves killed retained their buds and put out new leaves the following spring. Lodgepole saplings affected in 1909 now present a peculiar banded appearance, that part of the stem which was above the snow at the time of the injury being bare of leaves, while that part below it, which was covered by snow, and that part above it, which has grown since, are green. The red belt injury has sometimes been confused with damage from smelter fumes, but its nature is entirely different. (Pl. V, fig. 2.) Trees killed by the former die quickly as compared with those killed by the fumes. Weather-damaged trees which have recovered show a quick resumption of normal growth rate and a general healthy appearance, a marked contrast to the trees suffering from the smoke fumes. ANIMALS. Porcupines damage lodgepole to some extent by gnawing the bark in order to get at the tender cambium. They confine their efforts chiefly to young or middle-aged trees, though trees as large as 18 inches in diameter have been found completely girdled. Usually the bark is gnawed near the base of the tree, but occasionally animals work in the tops, as high as 50 or 60 feet from the ground, causing the trees to become stag-headed. Small branches are sometimes girdled near their junction with the main stem. Sometimes the attack may result in a beneficial thinning in an overdense stand, but porcupines have done considerable damage to trees on the Routt National Forest, Colo., where more than half of the trees on areas from one to several acres have been girdled, and in several localities on the Bonneville National Forest, Wyo., where 25 per cent of the trees have been injured. Rabbits often bite through the main stem of young seedlings, particularly the slender ones in overdense stands. Squirrels may cause a slight decrease in the rate of growth by biting off a number of the cone-bearing twigs. They also eat considerable quantities of- seed, the result of which may be harmful in places where reproduc- tion is not up to the required density. Sheep grazing unrestricted may damage seedlings and very young growth by trampling. ASSOCIATED SPECIES. Over most of its range lodgepole pine occurs in almost pure stands. Other species, however, often grow in mixture with it, particularly at the upper and lower altitudinal limits of the lodgepole zone. At the lower limit its chief associate is Douglas fir, which tends to take possession of areas too dry for lodgepole. Fir reproduction often occurs under the latter, and many areas now covered with lodgepole LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 27 would doubtless long since have given way to the more tolerant fir had it not been for recurrent fires. On south slopes and on dry, rocky knolls and ridge tops the fir may extend almost to the upper limits of the lodgepole belt. At the upper limit of the zone the chief associates of lodgepole are Engelmann spruce and Alpine fir, which come in on the moister sites. Spruce sometimes follows stream courses far down into the lodgepole type, where it takes pos- session of the moist bottomlands. Both the fir and spruce are much more tolerant than lodgepole, and reproduce under dense shade. At the higher elevations Alpine fir is apt to be more abundant in repro- duction than spruce, but the latter is a longer-lived tree and of much greater importance in mature stands. Both species when growing with lodgepole assist to a large extent in pruning the latter of its side branches. In Colorado and Wyoming limber pine and aspen also grow with lodgepole, though to a rather limited extent. In Montana white- bark pine is usually mixed with lodgepole toward the latter’s upper limit. PERMANENCY OF LODGEPOLE TYPE. Many of the present stands of lodgepole undoubtedly occupy areas previously covered with other species which have been driven out by repeated fires. If fire were kept entirely out of the forests, therefore, the lodgepole would in many situations be replaced by the original species—at the lower. altitudes by Douglas fir, at the upper ones by Engelmann spruce and Alpine fir. All of these species are fnore tolerant than lodgepole, and for this reason are able to crowd it out on sites adapted to all of them. It is likely, however, that there is a middle belt considerably narrower than the present lodgepole zone where conditions of soil and climate are more favorable to it than to competing species, and where it would probably be able to form a permanent type. In connection with the ability of lodgepole to maintain itself in competition with other species, it is interesting to know that Knowl- ton, in his studies of the paleobotany of Yellowstone Park, found in Tertiary deposits a serotinous cone of a tree species which he named Pinus premurrayana,: because he considered it the immediate an- - cestor of the lodgepole of to-day. A fossil cone, perfectly preserved, is slightly longer and narrower than typical lodgepole cones of the present. In Yellowstone Park Knowlton also found the fossil re- mains of species of Sequoia, Juglans, Hicoria, Fagus, Castanea, Ficus, Magnolia, etc. Of all the species now present in the park lodgepole is the sole survivor from the Tertiary age. - 17he form of lodgepolé pine occurring in the Rocky Mountains, now known as Pinus contorta, has also been known as Pinus contorta, var. murrayana, and as Pinus mur- rayand, , 28 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. GROUND COVER. Lodgepole stands, particularly in Montana and northern Wyoming, have a ground cover of grasses and weeds, many of which are yal- uable as forage. These include pine grass (Calamagrostis rubescens) in very large amounts, timber oats grass (Danthonia intermedia), lupine (Lupinus serviceus) , fireweed (Chamaenarion augustifolium), Indian paintbrush (Castilleja cRromosa), etc. Other plants worth- less for forage include huckleberry (Vaccinium scoparium), which is especially abundant on the poorer sites, arnica (Arnica cordifolia), and elk grass (Xerophyllum tenax). In moist places alder (Alnus tenuifolia) and willow frequently occur as underbrush. The forage | plants are less abundant in Colorado and southern Wyoming and the huckleberry more prevalent. Ordinarily fallen leaves disintegrate so rapidly that there is no accumulation of duff from this source. In mature stands there is very little litter as a rule, and one can ride through them almost anywhere. AGE CLASSES. A striking characteristic of lodgepole-pine forests is their even age. This, of course, is due to the fact that most of the present stands have originated as a result of fire, followed almost imme- diately by reproduction. Asarule, the burned areas thoroughly stock in a few years, though sometimes the reproduction is very open, the blanks filling in slowly with young growth and so producing an uneven-aged stand. Young stands often contain a few older trees, most of them limby and fire-scarred at the base, which have man- aged to escape destruction. Clear cutting is usually followed by even-aged stands, though the reproduction is apt to be slightly slower in establishing itself, par- ticularly if fire is kept out. Some areas cut over 20 years ago now have their blanks filled from seed produced by the rather scattered reproduction which followed the cutting. All the trees in even-aged lodgepole forests are not necessarily of the same size. Unless the stand is so dense as to cause stagnation some seedlings, especially on the more favorable sites, get a better - start and develop more rapidly than others. A small, suppressed tree often may be as old as another more vigorous one at its side two or three times as large in diameter. Fires have been so frequent in the region that they have brought about a wide range of age classes in the lodgepole zone as a whole. In Montana most of the stands are comparatively young. Figures collected there show that approximately two-thirds of the timbered area is now covered with nonmerchantable, immature growth, while the merchantable timber on the remaining third is partly immature, LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 29 partly mature, and partly overmature. In Wyoming and Colorado there is a much larger proportion of mature, and especially over- mature, lodgepole stands, a difference which leads to the conclusion that in the past fire has been less prevalent in Colorado and Wyoming than in Montana. YIELD. FACTORS INFLUENCING YIELD. The yield per acre of any stand varies with its age, density, and the quality of the site on which it grows. Ordinarily the better sites and older stands produce the heaviest yields, provided deterioration has not set in. With lodgepole, however, the yield, particularly in board feet, is determined more by the density of the stand than by either its age or the quality of the site. It is not unusual to find young, properly stocked stands of lodgepole with larger yields than older, overstocked stands on better sites. The effect of density on yield is illustrated in Table 6, which gives the results of measure- ments of 10 sample plots, all of approximately the same age. TABLE 6.—LHffect of density on yield per acre of lodgepole pine, Deerlodge National Forest, Mont. : Diameter of av- Trees per acre. Yield. Ratio erage tree. of ‘ board Heian Scale timber, | feet,6 2 2Ver Sample plot. Age. top diameter, | inches ee : inside bark, to—| top di- e ‘ Entire | Main | moo) ameter,| (dbh.8) All | Main stand. | stand.1 - |__| cubic! 12-)- | trees. | stand.1 6 8 feet. inches. | inches. Years.| No. No. Cu. ft. | Bd. ft. | Bd. ft. Feet. | Inches. | Inches. [28 Bae ey 8 110 501 293 4,187 | 10,542 3,217 2.52 59 Wee 8.4 Foz AS a} GY oie 109 701 325 5, 441 8, 682 1, 580 1.60 67 6.5 8.1 3S ae Se 109 764 338 | 6,286 | 19,440 | 4,387 3.09 71 6.6 8.4 ee at gee Shes) 108 810 338 7,331 | 20,400 2,456 2.78 72 6.6 8.6 i ley fry ea a 107 960 250 5,614 | 15, 260 1,190 22 69 Oud 7.9 (ee ae tae 107 987 303 6,178 | 12,070 1,610 1.95 69 5.9 7.8 #5 Se Sasa ee 107 1, 249 149 5, 080 24980 iS oe sea . 59 67 5.0 liao ‘1 See iy ee 104 1,495 124 4, 840 DEASO st eiteek oe shall 57 4.7 hee US ect Aa eee 101 1, 564 124 | 4,668 | 2,480 |.-.....- = (33 58 4.6 let UL ee SE ee ee 105 1,805 73 4,405 P4600) 5-5-8 5333 57 4.2 7.4 1 Includes all trees 7 inches and over in diameter, breast high. The table shows that an increase in the number of trees per acre beyond a certain point results in a marked decrease in the number of trees which will make scale timber, in the average diameter and height, and in the yield, especially in board feet. Much denser stands existed than any of those shown in the table, with corre- spondingly smaller yields. One plot 160 years old, for example, con- tained approximately 3,500 live trees per acre, not more than 4 inches in diameter. Such a stand produces only lagging poles. Other stands of the same age are still denser, producing nothing of value. 30 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. AVERAGE AND MAXIMUM STANDS. Reconnaissance estimates covering 65,000 acres on the Deerlodge. National Forest, which may be considered as fairly representative of the lodgepole region in Montana, show that the average stand of merchantable timber for all ages, densities, and sites is approximately 5,964 board feet per acre.t’ In Wyoming and Colorado the average stand of merchantable timber is estimated to run from 5,000 to 8,000 board feet per acre. Average stands on timber sale areas are apt to run much higher than this, because they usually consist of the better timber, and also because the reconnaissance figures apply to a con- siderable amount of cut-over land and to areas covered with young growth that is barely merchantable. Average stands actually found on timber-sale areas on the different National Forests are shown in Table 7. TABLE 7.—Average stand per acre of lodgepole pine and associated species on timber-sale areas in Colorado, Wyoming, and Montana. Yield per acre. National Forest. Lodge- Other pole. species. ATA ANOS OOE cert cee cece eee aie coke Se ok mS eee Cae ee eee 19° 4103|Ee eee 19, 410 WOCHELOPA COLORS s = eat ee ee See nent a oe te oe ee eee eee ee 6, 880 900 7, 780 RE TITITTISOTY MCOLO Re Pe ets eee eee ensene es ieee oe ee eerie an eae anne 2,500 925 3,4 MAT CInIs BOW Wy Os Sess. se cote ck eee, Fe en en Oe eee 14 2050 | be teehee 14, 225 EFA yen aWiy On ae Seen occ sb ait eect bat ng Se nieek Se ee ee ees ne Roem BB84 hana 8, 884 STOOL AAW iY. O fae eee oa Sete Ae et ete PE i 5 ee §, 3004| Seah eee 8, 300 STIG POR CWO os eee es ee ecb hen Ane oes ee ee, Coe yes 2,771 2,571 5, 342 Deerlodge: Monts. 22.222 Sco se 5 ot Cee ce es ccecitt ae oe ee lich, L438 se Serene 14,318 While the stands on the Arapaho, Medicine Bow, and Deerlodge National Forests are considerably better than the average, they are not as heavy as the stands sometimes found on limited areas in virgin forests. Five of the heaviest stands yet measured contained the fol- lowing amounts of lodgepole, together with small quantities of Engelmann spruce, Alpine fir, and Douglas fir: Board feet National Forest: per acre. APA DANO, OOUO =e a ss ee ee 27, 791 BRO CLO i a a Fe a a i 24, 400 White River, Golos 26. Hs ene 2 ast see Ses ee ee Ree ae eee 2 sae Medicine BO ws: WYO xa i a Pe I 5 ee i ee 34, 512 Beerlodgve,” Mont 26 2522 Bye ee i DT a a a ee 35, 9385 In addition to the 35,935 feet of green lodgepole pine, the stand on the Deerlodge Forest, which was 200 years old, also contained 4.610 feet of Englemann spruce and Alpine fir, and 8,090 feet of dead lodgepole, a total for live and dead timber of 48,635 board feet per acre. 1 All stands were considered merchantable which contained 2,000 board feet per acre or more, based on a minimum log 16 feet long and 6 inches in diameter at the smaller end. Many 7-inch lodgepole trees will yield such a log. ™~ ce as LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 31 DENSELY STOCKED STANDS. Table 8 shows the yield of stands which are densely stocked, but not so crowded as to cause stagnation of growth. The figures were obtained on the Deerlodge National Forest on the best quality of site. Most of the sample areas measured were 1 acre each. TABLE 8.—Average yield per acre of densely stocked stands of lodgepole pine at different ages on the best sites (Quality I), Deerlodge National Forest, Mont. Trees per acre. | A ver- Annual growth. ; Basal age ee oles . diame | height, Yield. years. || 5 Entire | Main 2” | main Peri Peri- feet. | stand.1| stand Seri stand. Mean. | odie, | Mean. | odie Bye See 106 | 1,550 50 ip SON [rustle AO OP ee ars cee lids TBs te | ea coer Pane nee an (A Sa Bis & Sons Ss 128 | 1,250 175 7.5 BGG 2, ZOOM Soe setae: 45 ol eS ere ics bres Se eee 144 |} 1,000 225 lent 56 | 3,100) 4,800 52 85 SOs |e ae ate (()) ae 156 825 255 8.1 60 | 3,800] 6,200 54.3 70 89 140 BUS =o 166 725 280 8.5 64} 4,350] 7,500 54. 4 55 94 130 eats Spe 174 650 300 8.8 66 | 4,900 | 9,000 54.5 55 100 150 OO 2s oe 180 600 320 9.0 68 | 5,400 | 10,800 54 50 108 180 PEO Foe 5 Fs. 184 535 330 9.4 70 | 5,800 | 12,600 53 40 115 180 J eee 188 500 345 9.6 72 | 6,200 | 14,800 52 40 123 220 3 eee 192 460 390 10.0 74 | 6,550 | 17, 200 50 35 132 240 LE Se eee 194 430 355 10.3 75 | 6,850 | 19,800 49 30 141 260 HO aln ee tci2 196 415 360 10.5 76 | 7,150 | 22,200 48 30 148 240 OO ay 5502 198 400 370 10.6 77 | 7,400 | 25,000 46 25 156 280 1 Includes all trees 3 inches and over in diameter, breast high. 2 Tncludes all trees 7 inches and over in diameter, breast high. 3 To a 6-inch top diameter limit. NORMAL STANDS. Normal stands are those which at maturity give the maximum yield possible to obtain under a given method on a given quality site. In the case of lodgepole pine properly or normally stocked stands are rare. Reconnaissance data, covering many thousands of acres of young growth in Montana, show that nearly 80 per cent of the area is overstocked, and that on the average the young growth is from one- half to six-tenths normally stocked. Because of its slow mortality lodgepole must start in comparatively open stands in order to yield the maximum amount of merchantable material at maturity. Such stands, however, are not dense enough to insure rapid, natural prun- ing. As already pointed out, the number of trees per acre adopted as the criterion of normality is 1,000 at 10 years, 500 at 30 years, 300 at 90 years, and 250 at 140 years. With these figures as a guide, and tak- ing into account the total yield of the stand, Table 9 has been con- structed from the figures obtained from those plots in Table 8 on which the stocking appeared to be most nearly normal. The amount of data is not sufficient to make the table anything more than indica- _ tive of what may be expected from normal stands of different ages on the best and on average sites. The original figures were secured on _ quality I sites, and the yields for quality II sites have been derived by * 32 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. multiplying the yields for quality I sites by 60 per cent, which seemed a fair reducing factor. In the case of board-foot yields strictly accu- rate results are not obtained when the same reducing factor is used for all ages and stands. The method is, however, sufficiently accurate to result in figures which indicate in a general way what results may be expected. TABLE 9.—Average yield per acre of normal stands of lodgepole pine at different ages, Deerlodge National Forest, Mont. BEST SITES—QUALITY IT. Yield. Annual growth. Board cone Cubic feet. Board feet scaling in top to— Age in Years. Cubic | feet. 6 inches. 8 inches. 6 inches. | 8 inches. | Mean. | Periodic. Mean. | Periodic.} Mean. | Periodic. | TOR et foe D5 On soe | ae Re 15 TS NOT Soe ec oie SN eee Re es | eee 7 a ABO ee Tes ee oak ee 22 30:0 [i cae |S eae ie SO ieee Pees | eee BOBS See 950 | GO0K Sena st ss 32 50. 0 30 OO se. 2 ee ro a ae 1,900 S000 1h: See eae 47 95.0 80 230 onc cael ee 50 Re ee 3, 050 Gai Beoeee eee 61 115.0 112 DAO) Sie Ps he a G(s 2 ee | 4,000 SOON Roe ae oe 67 95.0 135 2501 ose se eee OE ena 4,900 LO 00) Sac secs 70 90. 0 153 2607| SS Ra eae SOS. ese 2 5, 600 1S 400) Se eee ee oe 70 70.0 167 PH { OMA perme ie elite |p on Senet 89 TY eee 6, 300 AY S00 Wee een e sees 70 70.0 176 240 ie a | SO 1000S ss. 6, 800 18, 200 2,500 68 50.0 182 240 25 250 (ES eee 7,200 20, 500 5, 000 65 40.0 186 230 45 250 1D. | een 7, 450 22, 700 7,600 62 25.0 189 220 63 260 1631) eee 7,600 24, 600 10, 700 58 15.0 190 190 82 310 WAG he 7, 750 26, 400 14, 000 55 15.0 189 180 100 330 UG ee ee 7, 850 28, 200 17,300 52 10.0 188 180 115 330 UES ees 7,900 29, 800 20, 400 49 5.0 186 160 127 310 POSsae2 | 7,925 31, 200 23,300 47 Dro 184 140 137 290 SOP eee | 7,950 32,600 25, 800 44 2.5 181 140 143 250 19Q eter ee 7,975 33, 600 28, 000 42 2.5 177 100 147 220 DOE earn S| 8, 000 34, 600 30, 000 40 225 173 100 150 200 7A Fs ae 8,025 35, 600 31,500 39 2.5 170 100 150 150 77) ee 8, 050 36, 600 32, 800 37 2.5 166 100 149 130 } 1 AVERAGE SITES—QUALITY TI. Annual growth. Ratio of . F board Age in years. Yield. feet to Mean. | Periodic.| Mean. | Periodic. | cubic feet. Cu. ft Bd. ft. Cu. ft. Cu. ft. Bd. ft. Bd. ft TAG) a SAGO TAs ln ete nee ns 90) |e ocageet ee 9 | ies PAT eT ee rey oe | eg ee ene Dieigen Sree) ENE Tye. EM ad Sey. DO see eee ee 13 TBs | Sess NS le. ooo EL oe Oemae NAB eS I Noe on 570 | 540 19 30 18 54 0.95 AQ = BPP ee Me 0s Oe hoes 1,140 1,920 28 57 48 138 1.68 BN Us Sie St eS sear e aa 1,383 3,360 37 69 67 144 1. 84 GO ee nt es ae eee oe 2, 400 4, 860 40 57 81 150 2.02 OB Saas ss ei oS ea ea 2,940 6, 420 42 54 92 156 2.18 Se ABE Bh ele se Be A ro Rp ST 3,360 8, 040 42 42 100 162 2.39 Oise Se te re nae” he alias 3, 780 9, 480 42 42 105 144 2.51 1G 0, ee Anes A ak Pt eee ne ve eR 4,080 | 10,920 41 30 109 144 2.68 AT Opes cea 2 aie ee ee os 4,320 | 12,300 39 24 112 138 2. 85 IQ AES Bie iaese. aie cman 4,470 | 13,620 37 15 113 132 3.05 AS es a een, ee 4,560 | 14,760 35 9 114 114 3.24 TAQ 2 Re eenes A Eiaay oon ela Se hae Ee 4,650 |} 15,840 33 9 113 108 3. 41 BO Sees ee Serres ore te Al trp aie 4,710} 16,920 31 6 113 108 3.60 INURE aU 2 Loe oe Ne aE ae ee 4,740 17, 880 30 3 112 96 Beir 1 Board feet scaled to 6 inches in the top. & i me, 4 ; LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 33 It should be noted that these normal yields represent the best that have been found in unmanaged virgin forests, not the best which it is theoretically possible to obtain under proper methods of forest management. Table 2, for example, shows that a dominant tree at the age of 140 years is able to reach a diameter of about 12 inches and a height of about 75 feet, with a volume of 120 board feet. To determine in an approximate way how many trees could be produced per acre with the right kind of thinnings at proper intervals, the average space in the stand occupied by a tree of this size was meas- ured in a number of instances and found to average approximately 166 square feet. At this rate there should be 262 such trees per acre, with a yield of 31,400 board feet, which is 19 per cent greater than that given in the table of normal yield for 140-year-old stands on the best sites. While it is probable that such a yield could seldom be obtained even under intensive management, the illustration serves to show the possibility of securing better results with improved spacing. EFFECT OF THINNING. The marked effect which thinnings often have in increasing the rate of growth of individual trees is also notable in the case of stands. This effect is seen in a number of cut+over areas on the Deer- lodge Forest which were culled from 13 to 25 years ago. In every case the loggers removed only such timber as suited their purpose, in - some cases taking the larger material for ties, in others, removing the smaller trees for fence posts. Some of the trees left had thrifty crowns, and for this reason could be expected to benefit from the increased light; while others were very badly suppressed, with small crowns, and could hardly be expected to accelerate their growth to any extent. In collecting the data summarized in Table 10, average trees were selected for measurement irrespective of the probability of their showing an increase in the rate of growth. The various periods which had elapsed since the different cuttings were made averaged 20 years, and for purposes of comparison the figures were all worked up on the assumption that the cutting was done just 20 years before the date of the investigation. ~ 34 BULLETIN 154, U. S. DEPARTMENT OF AGRICULTURE. TABLE 10.—Effect of thinning on yield per acre of lodgepole pine in individual sample plots on the Deerlodge National Forest, Mont. PLOTS SHOWING NO INCREASE IN RATE OF GROWTH. > Stand 20 years ago. see Periodic annual |Increase P e Se ey er 20] or de- if rio a ss years) oftrees | crease ae since Trees. Volume. an Verses left. in rate thinning thin- ; of in years. | M28 | Browah 3 in after lyears.| Before | After | thin- " | Total.) Cut. | Left. | Total. | Cut. Left. Cut. Left. | thin- | thin- ning | ning. | ning. 5 | eee | : | | Num-| Num-| Num- Per ber. ber. ber. | Cu.ft.| Cu.ft. | Cu.ft. | Inches. | Inches.| Cu.ft.| Cu.ft.| cent. AS se | “18 |- 850 290 260 1,955 521 1, 484 4.3 6.1 45.5 15.6 —66 7h ete ne | 18] 430 320 110 2,336 1,486 850 5.9 6.7 27.0 19.8 —27 10622 -2.- | 14 | 1,600 | 1,200 400 | 6,136 3,396 | 2,740 4.5 6.2 34.0 Ded —19 10862222 | 20; 690 290 400 | 3,339 1,594 1, 755 6.0 6.1 a 0 4.7 —73 Ips eee | 20 | 1,730] 1,120 610 2, 267 1,028 1, 239 3.2 4.3 1 8.1 —33 PLOTS SHOWING INCREASE IN RATE OF GROWTH. CU Leeee 20 570 | 280} 290 | 951 399 552 4.2 4.1 16.1 22.6 40 ee 15 650 420} 230] 1,305 697 608 4.2 4.4 21.6 30.4 40 4552 = 15 910 500 410 | 1,434 563 871 3.5 4.2 31.8 36.3 14 9535255: 14 930 730 | 200; 3,146] 2,316 830 4.9 5.3 6.2 17.5 182 99025.< "52 20 | 1,050 500 550 | 2,049 985 1,064 4.3 3.7 15.0 Boe 121 Obi === es 940 610 330 2,412 1,058 1,354 4.1 5.2 SB Ry 24.7 80 100:22 2 = | 25 980 77 210 | 2,454 1, 430 1,024 4.1 5.6 8.2 21°53 160 18 ht eee 20 580 | 470 110 2,216 1, 335 881 5.5 6.5 10.1 15.1 50 2a ese 20 | 1,030 | 680 300 | 2,921 1,600 1,321 4.4 4.9 14.3 19.1 34 dO (eta 20 520 270 250 3,443 1,388 | 2,055 5.7 6.7 15.9 21.4 35 1 Yb Ee ee 13 840 490 300 | 5,178 2,887 | 2,291 6.0 5.9 15.9 28.8 81 j bog the pe 24 440 176 264 | 4,459 2,286 | 2,173 8.9 6.9 9.5 29.2 207 1h\: eee 24 585 485 100 | 3,769} 2,609 1,160 6.1 8.1 5.5 10.5 91 Of the 18 plots measured, 13, or 72 per cent, showed an increase in the rate of growth after the thinning. In other words, the small number of trees left after thinning produced more cubic feet of wood per acre than would have been produced by the entire stand had it been left unthinned and continued to grow at the same rate as before the thinning. This result is particularly remarkable when it is re- membered that all of the plots had reached an age when the periodic rate of growth would ordinarily be decreasing. Table 9 shows that in normally stocked stands the periodic rate of growth in cubic feet increases rapidly up to 50 years, after which it decreases slowly. For this reason the falling off in the growth of the 106 and 123 year old plots is no greater than would be the case in unthinned stands of the same age, and very likely it is even less. ‘he apparently abnor- mal rate of decrease in the rate of growth of the 48 and 49 year old plots is probably due to the fact that they were nearly normal at the time of cutting, as indicated by their volume, with the result that the rather heavy thining had an injurious effect upon the trees left. The 108-year-old plot is the only one for which the marked decrease in rate of growth can not be satisfactorily explained. errs . : ok — ee ee ee ee eee ee ee ee oe LIFE HISTORY OF LODGEPOLE PINE IN ROCKY MOUNTAINS. 35 If areas logged without thought for the future show such results, it is reasonable to suppose that thinnings made with the object of improving the stand will result even more satisfactorily, for the trees left will be thrifty-crowned specimens of moderate size, which are best able to take advantage of the increased light. Next to the exclu- sion of fire, the most important respect in which systematic manage- ment will improve the growth and yield of lodgepole forests is in bringing the stands to a density more nearly normal. ADDITIONAL COPIES @F THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE W+4SHINGTON, D. C. AT 10 CENTS PER COPY V WASHINGTON : GOVERNMENT PRINTING OFFICE: 1914