Life History of Short leaf Pine By - Wilbur Reed Malt o on Forestry SD397 P617 M3 JUljp i. 39. Hill IGtbrarg Nortlj (Carolina ^tatp Mniopraitg Forestry SD397 P617 M3 LIBRARY S00426751 P THIS BOOK IS DUE ON THE DATE INDICATED BELOW AND IS SUB- JECT TO AN OVERDUE FINE AS LlPRAnV -M983 AUG 18IS95 '^^l ^ 1985,., mu t 1996 MAR 1 9 1998 MAY C 1 1986 AUG 2 9 2005 MAY S C (I Vi'^.n ^, BULLETIN OF THE No. 24i Contribution from the Forest Service, Henry S. Graves, Forester, July 21. 1915. (PROFESSIONAL PAPER.) LIFE HISTORY OF SHORTLEAF PINE. By WiLBUK R. Mattoon, Forest Examiner. CONTENTS. Page. Name and ideutifieation Geographical and economic range. Character of stands ■^'ze, age, and habit Demands apon soil and climate. . . Ivight requirements Reproduction Growth Causes or injury Yield Page. 14 NAME AND IDENTIFICATION. It is important to distinguish clearly the true shortleaf pine^ (Pinus echinata Mill.) — variously known throughout portions of its range as "yellow," "old field," "rosemary," "two-leaf," "heart," and "spruce" pine — from other so-called shortleaf pines of the Southern States. Confusion occurs because of the custom, more or less generally pre- vailing throughout the South, of distinguishing only two kinds of pine, shortleaf and longleaf. Under this custom, the pine most com- monly included with shortleaf is loblolly pine,- slash pine being classed in similar manner as longleaf pine. vShortleaf is most readily dis- tinguished from loblolly pine by means of differences in leaf and cone, described on page 7. Other pines associated with short- leaf are the smaller, crooked-stemmed scrub pine and the northern pitch pine which seldom forms old-field stands and grows both in wetter and colder situations. 1 Shortleaf pine was first described botanically by Miller in ITtiS. In 1803, the elder Michaux defined more fully the specific characteristics of the species under the name of Pinus mitis, widely circulated in his work on American forest trees and largely used in botanical literature. The name Pinus echinata, first given to the tree by Miller, was not taken up by any author of note until the publication of Sargent's Silva, Vol. XI, in 1897, and by the accepted rule of priority, this is the correct name of the species. ^ Pinus taeda, know locally by various names, as "old field," "shortleaf," "swamp," "bull pine," etc. Note. — This bulletin gives in detail the life history of shortleaf pine, known under various names through- out the South, where only it is found in commercial quantities. 92233°— Bull. 244—15 1 FOREST RESOURCES LIBRARY N. C. STATE UNIVERSITY 2 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. GEOGRAPHICAL AND ECONOMIC RANGE. Shortleaf pine occurs in 24 of the States. Its geographical range includes all the States east of the Mississippi River, except Wisconsin, Michigan, and New England, and six States west of the ^lississippi. It extends from the Hudson River VaUey in New York^ south through aU the Atlantic and Gulf States to eastern Texas and from West Virginia and Ohio southwestward through the Ohio and Missis- sippi Valleys to Missouri, Kansas,- and Oklahoma. The tree is dis- tributed over more than 440,000 square miles. This is much larger than the range in the United States of white pine, its nearest com- petitor among the pines. Table 1. — Comparative diMribution of eight species of pines havinrj the largest ranges tnthin the United States.'^ Species. Areaofdis- States rep- tribution. resented. Sq. miles. 440,000 381,000 360,000 350,000 317, 000 300,000 295. 000 Longleaf pine 171, 000 Shortleaf pine White pine Pitch pine Western yellow pine . Scrub pine Red pine Loblolly pine. 1 Areas derived from Forest Service data on the geographic distribution of pines in the I'nited States, including approximately the exterior boundary of the botanical range. From sea level shortleaf pine ranges up to an altitude of about 3,000 feet in the southern Appalachians. At or near sea level it covers more than 1 1 degrees of latitude, or about 800 miles. In the North the species is confined nearly to sea level. It attains its best development at altitudes of 600 to 1,500 feet over the Piedmont and at 400 to 1,000 feet in Arkansas. In both these localities loblolly pine reaches only to altitudes of about 500 to 600 feet, above which shortleaf is the only important southern pine up to 3,000 feet and the only conifer except scattering juniper above about 700 feet in Arkansas, Missouri, and Oklahoma. The commercial range of shortleaf pine comprises most of the botanical range except that portion lying in the States north of Vir- ginia and in the Ohio River basin. It includes preeminently the broad Piedmont region lying between the Appalachians and the Atlantic coastal plain from Virginia to South Carolina; the northern half of Georgia, Alabama, Mississippi, and Louisiana; aU of Arkansas; eastern Oklahoma; and eastern Texas. Shortleaf pine is the only commercial conifer on more than 100,000 square miles of upland 1 Sargent. Herbarium notes. May, 1913. 2 Britton and Brown. Flora of Northern United States and Canada. Illustrated. LIFE HISTORY OF SHORTLEAF PINE. 6 region between Virginia and northern Alabama and Mississippi. The total area of its commercial range covers not less than 280,000 square miles. The production reaches its maximum over the gently rolling and hilly country of the Mississippi basin in northern Louisi- ana, most of eastern Arkansas, eastern Oklahoma, and eastern Texas. In common ^\^th practically all other commercial pines, the economic range of shortlcaf has become greatly reduced, and over the extreme northern part it has been almost driven out by close utilization and Fig. 1. — Botanical and commercial range of shortleaf pine. the consequent encroachment of hardwoods. In the upper portions of the Atlantic coastal plain it is to a considerable extent being replaced by loblolly pine on abandoned fields. The early clearing for agriculture of the lighter and better-drained soils greatly decreased the shortleaf seed trees and correspondingly increased the relative proportion of loblolly seed trees, which were left growing along the watercourses and on low heavy soils, where they find a congenial home. 4 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. CHARACTER OF STANDS. PURE STANDS. Shortleaf is very well adapted for growth in pure stands, and it occure extensively in tliis fomi of forest. The stands are not usually continuous over large areas, but are separated by mixed stands of pines and hardwoods. Stands of pure shortleaf pine once covered a much larger area than at present. It is dou])tful whether shortleaf is now found in pure type on more than from 20 to 40 per cent of its former range. Mature shortleaf occurs over a large region centermg in western Arkansas and northern Louisiana. This is the last extensive region of virgin shortleaf forest left in the gradual progress of the lumber industry southward and westward following the coast line. At ele- vations of 400 to 1,200 feet the hilly country supports heavy stands of timber, which, however, are being lumbered at a rapid rate. In the higher mountainous regions, including the southern Appalachians from 1,000 to 2,000 feet in elevation and the Arkansas and Ozark National Forests, the warm south-facing slopes are generally covered with pine in pure stands, and the northerly slopes with little else than hardwoods, chiefly oaks and hickories. A considerable proportion of the pure stands of shortleaf is found in old fields fomierly under cultivation. Here the factor of early competition with hardwoods was eliminated and the pine took com- plete possession. This form of second-growth forest occm*s exten- sively from Virginia southward and westward throughout its entire commercial range and aggregates probably more than 68,000 square miles.^ It represents practically all the land within the shortleaf- pine belt that has at any time been cleared and subsequently aban- doned. During a period of 10 to 20 years, commencing in 1861, a vast acreage of such lands was "turned out" all through the South; but the process of "clearing up," "working out," and "turning back" land has been in connnon practice for a century or more in the older pai'ts of the Southern States. MIXED STANDS. CONIFERS. In its geograpliical relation to the other eastern pines of commercial importance, shortleaf occupies a position characteristically interme- diate between white and Norway pines on the north and lobloUy and longleaf on the south. Between these two widely separated groups of important commercial pines, shortleaf occupies and domi- nates a broad strip of country. 1 Based upon general forest studies in practically all of the States, and detailed examination of 21 counties in North Carolina. LIFE HISTORY OF SHORTLEAF PINE. 5 Altogether 10 different species share in varying degree the range of shortleaf. Pond and slash pines and spruce pine merely overlap along the southern margin, but pitch and scrub pines share as much as one-third to one-half the botanical range. In parts of Virginia and North Carolina, scrub pine occurs in varying proportion in the mixed shortleaf conifer stands,^ particularly in old fields, and it succeeds in getting a strong foothold in the poorer soils, dry pastures, and waste places. On the lower or warmer side, shortleaf throughout practically its entire range associates extensively mth loblolly pine. In this association the two maintain, to a large degree, the relation of complementary species, loblolly holding the heavier, moist soils and shortleaf the drier and lighter soils. Valuable and extensive commercial forests of this character occur in Georgia, Alabama, Mississippi, Texas, and especially heavy stands in Arkansas and Louisiana. Both of these pines to some extent, and particularly loblolly, are replacing the slower-growing longleaf on all situations, except the driest and most sandy soils, tliroughout their region of contact.^ In the longleaf region shortleaf occurs generally in groups or smaU stands on favorable situations, but in large areas west of the Mississippi the two occupy practically the same soil type, and in mixture they make up heavy stands of maximum development. HARDWOODS. A large number of broadleaf species are associated with shortleaf through its extended range. Oaks and hickories, however, are so constant in their association as to be characteristic in many of the mixed stands. Over the Northern Atlantic States chestnut oak, yellow oak, and red oak are the most typical associates. From Virginia southward throughout the Piedmont country, lying between the coastal plain and the lower slopes of the mountains up to 2,500 feet, shortleaf still maintains its position generally as the dominant tree in mixture with the upland oaks and hickories. The primary associated species arc yeUow and Spanish oaks, big-bud and bitternut hickories, and, on the thin ridges, post oak and black-jack oak. The amount of shortleaf in the mixture varies widely, but throughout the eastern range represents usually from 35 to 60 per cent of the stand. In the hiUy and mountainous parts of Arkansas, the mixed shortleaf and lobloUy type gives way at elevations above about 400 feet to heavy stands of nearly pure shortleaf up to about 1,000 feet, whence ' Followmp are bctanical and common names of pines mentioned: Loblolly pine {Pinus tacda Linn.)- Longleaf pine (Pinus paluslris Mill.). Pitch pine (^Pinus rigida Mill.). Pond pine {Pinus serotina Michx.). Table Momitain pine {Pinm pungens Michx.). * Ashe, ^y. W. Proceedings of the Society of American Foresters. Vol. V, No. 1, p. Norway pine {Pinus resinosa Ait.). Scrub pine {Pinus virginiana Mill.). Slash pine {Pinus caribaea MoreL). White pine {Pinus strobus Linn.). 6 BULLETIX '2U, V. R. DEPARTMENT OF ACRICULTURE. the sliortleaf-hardwood mixed forest ascends the uiountaiii slopes to about 2,000 feet. The prevailing associates west of the Mississippi River are oaks and hickories, particularly yellow oak, bitternut and pignut hickories; on the dry ridges post and black-jack oaks; and in the fresher soils white and red oaks, big-bud or mocker-nut hickory, and red gum/ The commercial importance of all the hardwoods typically associated with shortleaf is comparatively small, except white oak in the region of its better development. Several inferior species, including pei'simmon, sassafras, and dogwood, are nearly everywhere represented in the mixture. Table 2. — Forest composition of the Arkansas and Ozark National Forests.' Arkansas National Forest. 2 Ozark National Forest.' Species. Total stand. Per centage of total stand. Diameter. Total stand. Per centage Average. Maxi- mum. of total stand. Shortleaf pine Board feet. 1,500,000,000 300,000,000 100,000,000 3.50, 000 3,348,000 96, 302, 000 75.00 1.5. 00 .5.00 .02 1.67 3.31 Inches. 18 17 16 16 16 Inches. 34 36 18 22 Boardfeet. 108, 890, 000 605, 925, 000 252, 809, 000 40,271,000 63,248.000 1,174,000 10 15 White oak oti. 51 Red and black oak 2i 57 :i76 Red gum 5.90 Miscellaneous . U Total 2,000,000,000 100.00 1,032,317,000 100.00 » Figures for the Arkansas Forest secured during reconnaissance in 1913. Figures for Ozark Forest from Bulletin 106, Forest Service, " Wood-Using Industries and National Forests of Arkansas." 2 Area of Forest, 750,000 a;cres. » Area of Forest, 481,575 acres. The percentage of shortleaf is relatively small in the Ozark, which is farther north, and increases outside of both Forests because of the lower elevations and warmer situations. Under virgin conditions the progressive changes within this mixed type resemble in some respects those that occur with white pine. By the thinnmg or removal of the valuable shortleaf pme, oppor- tunity has been afforded for the more rapid reproduction of tolerant hardwoods already on the ground. Thus, some territory formerly dominated by shortleaf in mixture is now held almost exclusively by hardwoods. 1 Names of hardwoods mentioned: Big-bud hickory (Hicoria alba Britt.). Black gum {Nyssa sylvatica Marsh.). Black-jack oak {Quercus marilai^ica Muenchh.). Dogwood ( Cornus florida Linn.). Chestnut oak (Quercus prinus Linn.). Persimmon (Diospyros virginiana Linn.). Pignut hickory (Hicoria glabra Britt.). Post oak (.Quercus minor (Marsh.) Sarg.). Red gum (Liquidambar styraciflua Linn.). Red maple (Acer rubrum Linn.). Red oak (Quercus rubra Limi.). Sassafras (Sassafras sassafras (Linn.) Karst.). Scarlet oak (Quercus coccinea Muenchh.). Spanish oak (Quacus digitata (Marsh.) Sudw.). White oak (Quercus alba Linn.). Yellow oak (Quercus velutina Lam.). LIFE HISTORY OF SHORTLEAF PINE. 7 SIZE, AGE, AND HABIT. Over much of its range the average height attained by shortleaf is between 80 and 100 feet, and in regions of better development between 100 and 120 feet, with a maximum of about 130 feet. Mature diameters of from 2 to 3 feet are most common; those of 4 feet are rare except in trees grown in the open. The tree commonly reaches an age of between 200 and 300 years, a maximum of about 400 years being occasionally attained. In size, shortleaf holds about middle ground between longleaf and loblolly pines. Loblolly gi-ows to an equal height and a greater diameter, but is not so straight a tree, Longleaf averages a little higher, but has a somewhat smaller trunk at maturity. A long clear straight bole with small taper and short crown makes shortleaf pine almost an ideal tree for the saw. These characteristics are so much more pronounced in shortleaf than in several of its pine associates, for example, pitch, scrub, and loblolly pine, that they serve commonly as distinguishing marks. In early hfe the tree has a narrow pyramidal stem, which later becomes more cylindrical (Pis. I and II). Tables showing the form or taper of the stem, both out- side and inside the bark, wdl be found in a forthcoming bulletin on the importance and management of shortleaf pine. These include tables for North Carolina and Arkansas, showing inside bark meas- urements at intervals of 8.15 feet above a 1.5 foot stump for trees from 40 to 120 feet in height and of corresponding diameter classes. The tables are adapted for use in calculations of cubic volume of saw timber from 8 and 16 foot logs, allowing 0.3 foot additional length for each 16-foot log. The butt taper at 1-foot intervals of trees of vari- ous diameters is also shown, and there is a table of tapers outside the bark at 10-foot intervals above the ground for trees from 40 to 90 feet in height. CROWN AND BARK. A short crown composed of numerous small branches, foraiing a narrow pyramidal head, permits of the close density which charac- terizes shortleaf-pme stands. This inherent narrow crown habit is well shown in trees grown in the open, where it is conspicuous even to an advanced age. Although changes take place in the relative demand of the crown for light after the period of maximum height growth (about 50 to 70 years), the change in the general shape of the crown is shght. While the crown of longleaf in early life has about the same outline as shortleaf, though loss dense, in later Hfe it broadens out far more. Loblolly maintains a much wider and heavier crown at all periods of life than either of the other important southern pines. This habit is more pronounced on the drier soils; hence in 8 BULLETIN 244, U. S. DEPAETMENT OF AnRICULTURE. the upper portions of its range, where associated witii short leaf, this difference in outline and internal branching of the crowns becomes striking and serves as a distinguishing characteristic. In keeping with the small, close crown are the short, slender leaves of shortleaf pine. The leaf characteristics, together with the cone, afford the best means of identifying the species. (Fig. 2.) Special notice of this is essential, because confusion prevails generally in dis- tinguishing the various pines. Shortleaf belongs distinctly to the two-leaf group of pines. On the more vigorous portions of the crown, however, three leaves in the bundle are not uncommon. The leaves are mostly 3 to 5 inches long, in some localities appearing en masse of a slightly bronzed or pale-green color, in contrast to the glaucous or blue-green color in other locahties or regions. Short shoots and colonies of sessile leaf bundles are often scattered along the trunk and over the upper sides of the larger branches. These are found on the pitch pine of the North and the pond pine of the South ; hut since they occur in none of the important southern timber pines except shortleaf, they serve practically as a characteristic distinguishing shortleaf from both loblolly and longleaf pines. The size of the cones ("burrs") aids in recognizing shortleaf when otherwise it might be confounded with loblolly pine, its most common associate in the lower soils. The small cones of shortleaf (from 1^ to 2h inches in length) when open on the tree appear to be about the size of pigeon eggs; those of loblolly (from 3 to 5 inches in length) about the size of duck eggs. The individual scales composing the cone in shortleaf are armed wdth slender, needle-pointed prickles, broken off more easily than the stouter persistent prickles of loblolly cones. The seed of shortleaf (described on p. 19) is likewise much smaller than that of loblolly pine. A difference in the bark of shortleaf and loblolly is readily per- ceptible up to the beginning of old age. The bark of loblolly is on the average thicker, more deeply furrowed and ridged, and somewhat darker in color than that of shortleaf. After maturity these differ- ences in bark become less marked, or disappear. RELATION OF CLEAR LENGTH TO CROWN. Measurements taken in shortleaf stands of average density show much regularity in the relation of the length of the living crown to the total height of the tree. In stands about 10 feet in height the depth of the canopy averages 5 feet, or one-half the height of the stand. Above this height the canopy gradually becomes propor- tionately shorter, until at 80 feet clear lengths of 45 to 55 feet are reached. This is from about 60 to 70 per cent of the total height, varying with different quahties of site. The crown is relatively longer, in proportion to the total height of the tree, on the poorer situations, and, conversel}^, the clear length of the stem is shorter. LIFE HISTOEY OF SHORTLEAF PINE. r^^-p^'^^/y Fig. 2.-Sliortleaf pme leaves, seed, cone (burr), and seedling: a. Young seedling; b, same one month later; c, seedling at end of first season showing early bundles of true leaves; d, two-leaf and three-leaf clusters; e, branch with mature closed cones (burrs); f, cone scale and seed with wing detached; g, mature cone opened. (Drawn to scale from actual specimens.) 92233°— Bull. 24-1— l.i 2 10 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. Figure 3, based on measurements of 34 well-stocked shortleaf pine stands in Arkansas, represents graphically the proportion of clear length to crown length for trees of various heights on the better and poorer quality of situations. The lengths of the crown and clear stem and their proportion of the total height of the tree are given in Table 3. In New Jersey 70-year-old stands 65 feet high had practically the same actual depth of canopy as vigorous stands 50 years old and 80 feet in height in Arkansas. The proportion of clear length to total height in New SS -^ 33 32 ZS /3 /O S C ^- S /3 /S 2S 3/ '38 -^6 C6ea.^ 6ert^&/v of Vree'6el.o>v C/'oivn, — fee-b. Fig. 3.— Relative proportions of clear length and crown depth for shortleaf pine of various heights on better and poorer qualities of site in Arkansas. Jersey was about 48 per cent, as compared with 70 per cent for the better stands in Arkansas. Table 3. — Clear length and crown length of dominant trees in vell-slockeil stands of shortleaf pine in Arkansas. Total height of tree (feet). Better Quality site. Poorer quality site. Clear length. Crown length. Clear length. Crown length. Feet. 5 10 18 25 32 39 46 55 63 Perct. 50 50 60 63 64 65 67 70 Feet. 5 10 12 15 18 21 24 25 Per ct. 50 50 40 37 313 35 33 31 30 Feet. 4 8 13 19 25 31 38 46 53 Per ct. 40 40 43 47 50 52 54 57 60 Feet. 6 12 17 21 25 29 32 34 37 Perct. 60 30 57 40 ... 53 50 TO ... ... 46 SO 43 40 CROWN SPREAD AND TREE DIAMETER. In well-stocked stands of shortleaf pine a very close relationship has been found to exist between the diameter of the tree at breast height and the diameter of the crown. This relationship is strildng in its LIFE HISTOBY OF SHORTLEAF PINE. 11 constancy and, so far as is known/ has never before been found to exist in any Nortli American tree species. It was found to hold true for all crown classes within a range of ages from 20 to 80 years, rep- resenting average diameters up to about 16 inches. Indications point to this relation holding true beyond 80 years, although no meas- urements in pure shortleaf pine have been made. Later measure- ments by Prof. H. II. Chapman, of Yale Forest School, indicate a ?0 a Ifl / ^ IB ■ 14 * »< ^/ ^ \? .£ ^ f f. in <■ 1 , ^^ ■ > P 9 l^» n^ » 5 LEQENL ; r : l,yr o/d S 20 hind (Old (Fo (Old field) /■» 24 rest) 10 ■tirJd) 24 A /■ e 31 42- (Fc (.Old -est) S3 f,r:ld) 32 16 ? |>'1 ■»■ 5^" SO- A.^ragc S. rr,ph ^«« 13 12 Us 1 C/O) 2fl4 rof,,l 559 6 ^ 10 12 14 TREE DIAMETER BREAST HIGH-INCHES Fig. 4.— Uelal ion of crown widtli to diameter of tree. (f-:iiortleaf pine, 1 1 to GO yea ; old, in Arkansas.) constant relation between the diameter and crown in mixed short- leaf and lol)lolly pine stands from 80 up to 200 years; also recent deductions from yield and growth data of red spruce show a definite relation existing between basal area and gi'owing space in even-aged stands between 20 and 100 years.^ The evidence from which the conclusion is drawn is shown in figure 4, based on 545 trees on 25 sample plots, representing 16 different ages, 1 Determined in January, 1913, from measurements taken in November and December, 1912. » By L. S. Murphy, Forest Service. 12 BULLETIN 2U, U. S. DEPARTMENT OF AGRICULTURE. and the average tree on each of 14 other sample areas, or a total of 559 trees. All the trees of the three crown classes m the stand and on the different quahties of site are represented. Under the influence of all these different factors, which are considered variables in mat- ters of tree growth and volume increment, the size of both diameter and crown spread have been found to vary uniformly and in the same direction. This intimate relationship between tree diameter and crown spread is apparently an expression primarily of tolerance or relative demand of the species for hght. Table 4 gives the average crown spread in feet of each breast-high diameter class from 5 to 16 inches. It shows a perfect regularity between the size of the tree and the space occupied by its crown, irrespective of age and vigor. The table shows that for each increase of 1 inch in tree diameter the crown spread increases 1.4 feet in Arkansas and 1.75 feet in New Jersey. This difference in rate is probably due to the effect of differ- ent climatic conditions upon the tolerance of the species. During earlier life up to about 15 years the relation appears to be in the ratio of 1 foot of crown spread to each inch in tree diameter. This law of growth finds practical application in determining for any specified diameter class the total number of trees that can most profitably be grown per acre in a weU-stocked stand. Since diameter is a direct function of age in any given quality of situation, the tree density on the ground at any desired age can likewise be ascertained. Knowledge of this sort is fundamental in working out problems of thinning, cutting, and final yields of timber. Table 4. — Relation of tree diameter and crown diavuter for shortleaf pine trees iti fully stocked stands for all ages from 20 to 80 years — Contrast of regional difference for Arkansas and New Jersey. Crown diameter. Favorable region (Arkansas). Unfavorable region (New Jersey). Tree diameter breast, high (inches). Crown diameter. Amount of increase. DifTer- ence in crown diameter and tree diameter. Crown diameter. Amount of increase. DilTer- enco in crown diameter and tree diameter. 5 Feet. 5.2 6.6 8 9.4 10.8 12.2 13.6 15 16.4 17.8 19.2 20.6 Feet. Feet. 4.8 B.l 7.4 8.7 10.05 11.4 14' 15. 3 16.6 17. 95 19.3 Feet. 3.25 5 6.75 8.50 10.25 12 13.75 15.50 Feet. Feet. 2. 85 6 1.75 1.75 1.75 1.75 1.75 1.75 1. 75 4.5 6. 15 8 7.8 11 9.5 11.21 12. 85 14.5 16 LIFE HISTORY OF SHORTLEAF PIXE. 13 ROOT SYSTEM. Having strongly developed taproot and laterals, the tree is seldom thrown by wind except in the case of tornadoes. This root system also enables the tree to thrive in relatively dry situations. Taproots 14 feet deep have been found on 8-year-old saplings, which shows the abihty of the tree to search for moisture. (PI. I.) This root habit may account, in part at least, for the wide geographical dis- tribution of shortleaf pine, and, within much of its range, its suprem- acy over all other conifers, except red juniper, in successfully occupy- ing the driest upland soils and exposed ridges. It is significant that shortleaf pine, which maintains throughout life a higher tree density in pure stands than any other eastern or southern commercial pine, possesses inherently both a narrow crown and deep root system. Tlie distribution of loblolly pine over the tideland districts and along watercourses and the absence there of shortleaf pine is undoubtedly due to an ecological effect of root development and iuherent adaptation. DEMANDS UPON SOIL AND CLIMATE. Shortleaf occui*s on a wide variation of soil types, ranging from the gravels and sands to stiff clays. In respect to soil moisture, however, its-requirements m one particular are more exacting ; namely, under all conditions, shortleaf avoids very poorly drained or wet situations. Its home is essentially on the better-drained soils. In New Jersey it grows on the low ridges of gravelly loam, associated with chestnut oak. Over the extreme lower portion of the Atlantic coastal plain, from North Carolina through southern Georgia, Ala- bama, and Mississippi, its occurrence is always on the well-drained ridges and hummocks. The physiography and soil types of the Pied- mont region, from the upper coastal plain well into the lower slopes of the mountains, are favorable to its vigorous growth. The deep, well-drained, gravelly or clayey loam soils of this region favor short- leaf but discourage loblolly, which is much inferior in abihty to withstand drought. In the lower shortleaf range toward the south- ern coasts the lighter grades of sandy soils are occupied by longleaf , which possesses .remarkable tolerance for deep and very dry soil conditions. CLIMATE The broadness of the cHmatic conditions favorable to shortleaf pine is clearly indicated by the tree's wide geographical range The range of temperature is from the mean annual temperature of 48° F. in northern New Jersey, through 60° in central Arkansas, to 70° in southeast Texas. Of greater significance is the difference be- 14 BULLETIN 244, U. S. DEPARTMENT OP AGEICULTURE. tween the midwinter (January) mean of 26° in northern New Jersey and the midsummer (July) mean of 84° in southeast Texas. Within its geographical range occurs a total temperature range of 134° F., from a minimum of —22° in New Jersey to a maxinmm of 112° in northern Louisiana. The length of the growing season is indicated approximately by the period during which killing frosts do not occur. In New Jersey this period averages only five months, from May 1 to October 1 ; in northern Louisiana it is a little less than eight months, from March 16 to November 8. There is a variation in sno^\^'all from an average of 40 inches at the north to none whatever over the south- ern range of the species. In the northeast, the 45-mch Ime of amiual precipitation closely parallels the northern limit of shortleaf's range, and the line marldng an average of 40 inches of precipitation about coincides with its southwestern boundary in Kansas, Oklahoma, and Texas. Shortleaf advances farther into this region of low relative humidity than any other pine, and in its advance into Texas falls behind only cypress and eastern red cedar. The belt of maximum development of shortleaf — northern Louisiana and Arkansas and the southern Piedmont — coincides strikingly with the rainfall zone of 45 to 55 inches, or an average of 50 inches. In general, shortleaf pine reaches its best development under (1) a mean annual temperature of about 55° F., from a 35° average for the coldest months of the year to a 75° average for the warmest; (2) an annual precipitation of 45 to 55 inches, distributed through at least nine months of the year; and (3) in deep, porous or w^ell-drained, clayey, or gravelly loam. In less favorable conditions, the species shows considerable vigor of growth over regions of wide variation in temperature, atmospheric moisture, soil composition, and, exceptmg in the heavier, poorly drained soils, soil moisture. In demands upon both moisture and heat, shortleaf is clearly the least exacting of the important southern pines, which may be put in the following order: Slash, longleaf, lobloUy, shortleaf. LIGHT REQUIREMENTS. Shortleaf pine requires an abundance of direct overhead light fof development, yet at the same time it possesses to a remarkable degree both the power to withstand suppression for many years and the capacity of rapid recovery following suppression. The intimate relation between light supply and growth in early life is graphically shown in figure 5, drawn to scale from an 11 -year-old crowded short- leaf-pine stand. The adjacent stands cut off all side light and slightly reduce the overhead supply. The height growth increases at an accelerated rate as the distance from the adjacent stand increases, reaching its normal level of 22 feet at a distance approxi- LIFE HISTORY OF SHORTLEAF PIXE. 15 mately the same as the height of the marginal trees. IncidentaJly this close response in growth to varying degrees of light makes short- leaf a good recorder of unusual climatic or other events which strik- ingly alter existing light relations. Typical examples of this are given on page 32, under the discussion of recovery after suppression. Because of its inherently narrow cro^^l and medium light require- ments, the density of shortleaf stands remains high to a relativel}^ advanced age. So many factors enter into the problem that it is impossible to determine the absolute position of shortleaf in the scale of light requirements without a much greater number of exact meas- urements. To compare it, however, with other southern pines, under similar conditions of soil, heat, moisture, and age, shortleaf through- out life requires less light for development than longleaf, does not in early life tolerate shade so well as loblolly, but retains longer the Ai/erp.(pe height ZZ I fO 20 30 AO SO 60 0/SftUfCE Fig. 5.— Effect of light supply upon height growth, shown by a vertical section through a 2-year-old short- leafstand. Fully stocked, even-aged shortleaf stand, 11 years old and 22 feet high. (Drawn from actual stand.) power of growth under limited light supply, showing this retention of power by a relatively later and slower decrease in tree density. NATURAL THIN^fING AND STAND DENSITY. The dependence of shortleaf on a full supply of light in early life is seen in the rapid reduction of very high tree density in natural unthimied stands. A square rod of 8-year-old saplings, encroaching upon a cotton field in Nevada County, Ark., contained a stand of about 58,000 per acre. At 10 years, as many as 25,000 to 40,000 trees per acre over limited areas are not uncommon. At 20 years the normal stand contains from 900 to 1,200 trees. In fully stocked stands natural thimiing progresses very rapidly durmg the first decade and at an increasingly slower rate during the following 20 to 30 j'ears. After this period the loss of trees is very noticeably gradual for the remainder of life. Natural thinning is most rapid and culminates earliest in the best quaUty of situations both from a regional and local standpoint. In the central Mississippi 16 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. Age20Vears (800 Trees Per Acre) Age33Vears (580 Trees Per Acre) Valley region the first general period ends somewhere between the ages of 40 and 50 years, depending upon the local situation; in the central Atlantic coast belt apparently between 55 and 70 years. Figure 6, showing progressive stages of natural thinning and cro"\\ai, classed according to age, represents actual numbers of trees and outlines of crowns as they existed in four fully stocked stands in Arkansas measured for growth and yield. The 20-year-old stand contained 800 trees per acre; the 33-year-old stand, 580 trees; the 42-year-old stand, 400 trees; and the 52-year- old stand, 320 trees per acre. Shortleaf pine shows progressive changes in the character of the forest canopy other than the mere reduc- tion in number of trees. These changes are well illustrated in figure 6 for stands from 20 to 50 years old. In early life the tree crowTis are approximately circular in outline and closely approach each other, leaving very little un- occupied space. At the age of 50 years, however, the tree has become less tolerant, the crowns are quite irregular in outline, and crown isolation leaves relatively large light spaces in the canopy. The slow rate of natural thimiing after about 50 years undoubtedly is accompanied by relatively small changes in the tolerance of the tree. The climax of lateral growth or spread of the branches characteristic of the species seems to be closely ap- Age4-2 Years t400TreesPerAcre) Age52Year5 (320Trees Per Acre) Fig. 6.— Progressive change in tree density by natural thinning in pure even-aged stands of shortleaf in Arkansas: D, Dominant classes; I, intermediate; S, suppressed classes. Areas, 33 by 06 feet. (Drawn from actual stands.) 3ul. 244, U. S. Dept. of A^ Plate I. j|. 244, U. S. Dept. of Agriculture. Plate II. m:f^'£M "^.i^-^^^-^-r*:-' wo ■i ^^^^^!^ fPff y- .^ ^ sf "^ "'^^^ ||o|t . ^ ^l-.J |/* >^^ p^--; " ' H ^^^^^' 1,,'^ W'^ i '^^SSUPy^f^r^Ww^rV^^^ ^^^^^^H^B^I ^^^mM^ '^Jf^ '( H ''W rA.>A * ''"''''fl^^^l 9P' jOff ' -J-"J#^ ^^ ^ "iM e %- IW^ ^.dl fi-. /^ ^^^nPifx-i^ Rv ^ ^Si^^^l mm' #^ ''^P| -ff^B ^ Wi ■ ^ , ^H '' n ^^^H^ "H^M^M VSlVfcM, i '■ Z UJ jl. 244, U. S. Dept. cf Agricultu Plate III. Bui. 244, U. S. Dept. of Agriculture. Plate IV. Fig. 1.— Shortleaf Pine Fire Coppice 4 Years Old in Foreground from 6-Year- Old Sprout Parent Stock. A Few Trees of the Former Stand, now 10 Years Old, are Seen in Center. Fig. 2.— Thrifty Stand of Shortleaf Pine Reproduction, 3-Year-Old Fif;E Coppice, from 3-Year-Old Seedlings Parent Stock. Arkansas National Forest. LIFE HISTORY OF SHORTLEAF PINE, 17 proached at about the age oi 50 or 60 years on the best sites and 70 to 90 years on the poorer sites. In respect to the number of trees per acre at these ages, shortleaf somewhat exceeds longleaf and notably surpasses loblolly on similar qualities of site. At ages, ranging mostly from 175 to 225 years, natural thinning of stands, due to old age and overmaturity, goes on at a more rapid rate. This is closely associated with the incoming of the new generation and the sudden and rapid increase in numbers per acre. The number of trees per acre in well-stocked stands decreases as the quality of the site improves. At 20 years, well-stocked stands in the Arkansas region have usually from 1,000 to 1,300 trees per acre; in North Carolina, 1,400 to 1,800; and in central New Jersey, 1,800 to 2,400. In general, this regional difference holds good for several decades; so that at 50 years well-stocked unthinned stands have approximately 300, 355, and 500 trees per acre, respectively, in the above three regions. The relation of the density to the quahty of situation, both in one locality and in widely separated regions, appears to be constant and regular. The difference in densities in normal or well stocked stands in North Carolina and Arkansas is well shown by the contrast between Table 5 and Table 6. Table 5. — Number of shortleaf trees per acre in stands of different densities in Arkansas.^ Age (years). Under- Well Over-" stocked. stocked. stocked. 840 1,130 1,540 475 600 1,000 290 400 550 210 300 400 170 250 325 140 215 280 100 185 250 80 145 185 80 128 175 75 118 160 Age (years). Under- Well stocked. stocked. 75 115 70 110 65 105 65 102 60 100 60 100 60 100 55 55 95 Over- stocked. I Based on measurements in 38 even-aged stands. The number of trees per acre vary quite widely in each case in accordance with the quality of the situation, and the numbers should be considered approxi- mate rather than exact. Table G. — Number of trees per acre for well-stocked shortleaf stands in North Carolina. Age (years). j Q"f ^y Quality Quality Age (years). Quality Quality ftuaj.,. 20 1,000 675 510 410 340 280 235 1,635 1,095 765 600 509 420 355 2,4.50 1,880 1,405 1,045 795 655 550 200 165 140 120 100 90 310 270 230 205 180 155 30 65 370 35 70 330 40 50 92233^ ' Based on measurements of 80 sample plots; area, 21.6 acres. -Bull. 244—15 3 18 BULLETIN 244, U. S. DEPARTMENT OF AGEICULTURE. As a result of repeated burnings the density of natural stands is usually very variable. Occasionally second-growth stands have been protected by surrounding cultivated fields and the watchfulness and care of their o\^Tiers. Such stands show striking regularity of tree density and much quicker wood production than unprotected stands, which is due to the influence of a protective mulch consisting of leaves C'pine straw"), twigs, and bark. REPRODUCTION. Few of the valuable pines in the United States reproduce as vig- orously as shortleaf . The regeneration is accomplished by seed and by complete sprouting during the period of early life when the tree is most susceptible to severe injury. Reproduction by means of nat- m-al seeding is successful and heavy, because of the frequent and full seed crops, the lightness and short germinating period of the seed, and the high resistance of the seedling to unfavorable conditions of temporary shade and drought. Abandoned fields and openings made by lumbering, windfall (in the tornado belt west of the Mississippi), and fires are quickly occupied by shortleaf pine. Ten representative counties in western North Carolina contain 393,670 acres of old-field stands of mostly pure short- leaf pine. This is 14 per cent of the total area, or 27 per cent of the forested area, of the counties. Such old-field stands characterize the forest lands of the upland regions from Virginia southward and west- ward throughout the range of the species. The extensive pineries near Lakewood, N. J., are mostly pure stands of shortleaf C' two- leaf ") pine of similar origin. (PI. II.) In mixture with the inferior pitch pine in New Jersey and loblolly pine in the lower or outer por- tions of the shortleaf range, it has not successfully held its former place of importance. The cause lies chiefly in the much closer utili- zation of the shortleaf and the resulting relatively greater abundance of seed trees of the associated species. In the southern mixed hard- wood forest there has been a notable extension of the importance and commercial range of shortleaf. This has been due to the successive clearing, working, and "turning out" of fields and to the extensive ranging of hogs. The hogs consume practically aU of the oak and hickory seed and at the same time prepare excellent seed beds for shortleaf pine by uprooting soil and humus in the fall of the year. Some seedlings, of course, are later destroyed by the same process. The results of these two agencies, operative for periods of 75 to 200 years, have been cumulative and have produced marked changes in the composition and density of the forest in various parts of the South. On the National Forests of Arkansas natural reproduction is heavy except on the cool northern exposures, and the encroachment of LIFE HISTORY OF SHOETLEAF PIXE. 19 shortleaf pine into the oak and hickory tj-pe is particularly notice- able. Fresh openings become fully stocked usually during the first four years; and, normally, in the mixed pine-and-hardwood type, groups of pure young pine of a few prevailing age classes are numerous. SEED. The seed of shortleaf is very small, varying usually from 50,000 to 70,000 to the pound. The cones which produce them are among the smallest for all pines — from 1^ to 2| inches in length. They persist on the trees for periods of about four years on vigorous shoots to seven or eight 3^ears on suppressed portions of the crown. Ripen- ing in early autumn, the seeds fall by the middle of November and he dormant during the winter. Germination usually takes place during March or April. In ordinary seed years the seed averages 50 to 60 per cent germination, varying quite widely below this stand- ard in unfavorable seasons and with unhealthy or old-aged trees. One tree 280 years old had a full crop of cones bearing apparently good seed. The germinative power of shortleaf pine is retained to a large degree for several years. Seed of the 1911 seed crop, kept at ordinary living temperatures, gave 56.8 per cent germination in the spring of 1914. The seedlings, however, were apparently somewhat lower in vigor than those grown from fresh seed. The seed of the shortleaf has some advantages over seeds of other species. A marked abihty to germinate successfully in grass and leaf litter, as compared with other southern pines, has been ob- served.^ This is in line with the inherent capacity of the species to thrive on the lighter upland soils deficient in soil moisture. The very small size of the seed gives it an advantage over larger seed in quickly reaching mineral soil. By means of a relatively large wing the seed is readily borne by the wind. A breeze will carry seed a distance of from 2 to 5 times the height of the tree; and strong winds will carry it from one-eighth to one-fourth of a mile. Seed is produced both abundantly and regularly. Full crops occur at an average interval of about three years, with intermediate or partial crops almost every season. In a typical region of the Arkansas National Forest, during a period of 13 years commencing in 1901, shortleaf pine bore four full seed crops, seven partial crops, and failed entirely during two seasons.^ The years of abundant seed were 1902, 1907, 1910, and 1913; 1903 and 1909 were blank years, and the others intermediate. Thrifty trees with good fight supply begin to produce seed at about 20 years. Exceptional trees have been noted with cones at 16 years. In open or mixed forest ' Proceedings of the Society of American Foresters, Vol. V, No. 1, "Loblollj- and Shortleaf Pines," by W. v. Ashe. ' Record of seed crops determined by study of crowns in a large logging area, Womble, Ark. 20 BULLETIN 244, U. S. DEPARTMENT OF AGEICULTURE. stands seed is produced at intervals tliroiighout life after about the thirtieth year. In crowded stands seed production is confined to the larger dominant trees and is deferred until about 40 years. SPROUT OR COPPICE REPRODUCTION. Shortleaf pine sprouts vigorously, and thus reproduces itself if killed back during the period of early life. This period fortunately is the time of greatest susceptibility to injury both by fire and various mechanical agencies. Its range over the drier uplands is coincident vnth a region of frequent forest fires, yet it is saved by notably abundant reproduction practically every^vhere. Of the important commercial pines in the United States shortleaf alone possesses tliis capacity of complete reproduction.^ A field investigation in 1912-13 showed clearly that comparatively very few seedlings reach ages of 3 to 6 years without being burned back, and that most forest stands have passed through this experience on repeated occasions. It has been found possible, although somewhat difficult, to trace the history of most stands and determine definitely their origin, whether of direct seedhng or coppice growth. Thus, the majority of all standing shortleaf timber examined in various portions of Arkansas was found to be of coppice origin. In abandoned fields fire less frequently sweeps over young stands because of the fu'e pro- tection afforded by the naked soil. In spite of this, many old-field stands have suffered from at least one fire. Observation in Georgia, South Carolina, Virginia, and New Jersey showed that similar con- ditions exist throughout the geographical range of the species. The property of sprouting accounts for the remarkable aggressiveness of shortleaf pine over the region in the South most endangered by fire. Second-growth forests of the Piedmont and Appalachian regions have been subject to frequent fires during more than a century. As a general law, it may be stated that, in any specified locality, the pro- portion of shortleaf pine of seedling origin varies inversely as the frequence and general prevalence of fires. Stands of direct seedling origin are on the whole of insignificant area, because there are few localities protected against fire by natural barriers or by man. In one locality of optimum shortleaf development in Pike County, Ark., the only stands of direct seedling origin found were located in low, moist situations where burnings have been infrequent. Obviously the perfection of vigorous reproduction by coppice, though limited to early years, is of high importance in the profitable management of a forest species. Since the occurrence of a commercial coniferous forest largely of coppice origin is very unusual in any other species, a discussion of the function of coppicing, the sprouting capacity of the tree, and the way in which the sprouts are produced is of interest. ' other pines which to a greater or less degree sprout when young are pitch pine (P. rigida), pond pine (P. serotina), and Pinus cWmahvxina along the Mexican border. LIFE HISTOEY OF SHORTLEAF PIXE. 21 EXTENT AND NATURAL LIMITATIONS. In open-grown, vigorous stands, shortleaf successfully coppices up to about the eighth year, and in slow-growing, crowded, or shaded stands, to the tenth or twelfth years. The upper limit of size at which coppicing may take place ranges from diameters near the ground of 3 to 4 inches for vigorous individuals down to 2 to 3 inches for trees of slow growth. Thus the chief limitation seems to be age, modified by the general vigor and size of the individual stem. Withm these limits shortleaf is known to coppice repeatedly. Regions of frequent fires afford opportunities to observe the effects of repeated burning to the ground upon younger-aged stands. Figure 7 shows diagrammatically a fully stocked stand in Arkansas, composed Fig. 7.— Vertical section through three successive generations of shortleaf pine fire coppice. PikeCounty, Ark. (Drawn from actual stand.) of three successive generations of coppice resulting from fires in 1902, 1904, and 1910. Each age class was regular and normally stocked. The heights averaged 17 feet for the 10-year-old, 11.5 for the 8-ycar-old, and 2.5 feet for the 2-year-old stand. Similar suc- cessive generations of coppice are commonly met throughout all the shortleaf region. Around the margin of a young stand, surface fires burn freely, fed by the better growth of grass and light dry materials deposited by the wind; while farther within the stand there is less ground litter, and the shaded surface is often too moist to burn in the cool season when fires prevail. The number of successive generations of sprouts that can be pro- duced from an original parent seedling is not known. Young coppice of the second generation of sprouts is readily identified under close observation. It occurs abundantly except in old-field stands. Three 22 BULLETIN 244, U. S. DEPAETMENT OF AGRICULTURE. successive generations of coppice have been definitely identified ; but beyond tliis, evidences of the past history of the tree become greatly obscured. In the third generation of sprouts the rate of height growth appears to be undiminished. Practically all of the root system is utilized by the new generation. As an effect of the root energy and stored-up food, the rate of early height growth is remark- ably rapid and, within limits, increases with the age of the parent tree when cut or burned back. As a rule, during the first two to four years, depending upon the age of the parent, the sprouts make up completely for the previous loss of time in growth. The most rapid height growth observed was in a 4-year-old fire sprout stand, many trees being from 5 to 8 feet in height and the tallest 9.6 feet. The growth in height of thrifty stands of fire coppice, based on measure- ments of both trees and whole stands up to 18 years old, is showTi in Table 6. The age at which trees of sprout origin grow at approxi- mately the same rate as seedling trees is not precisely known. Under average conditions this point is perhaps between the fifth and ninth years. In general, the great acceleration in growth in fire sprouts takes place at approximately the same rate in diameter and volume as in height. CAUSE AND METHOD. Fire and cutting are the chief external causes for the sprouting of shortleaf pine. The physiological cause lies in the capacity of short- leaf pine to develop on the upper portion of the root and lower portion of the stem special reproductive buds, at least one of which has the same function as the central terminal bud on the stem. The double crook, at the upper end of the taproot of shortleaf pine, characteristic of and always present in young trees, seems to be inti- mately associated with its power of reproduction by sprouts. By means of this double crook a horizontal section from 1 to 3 inches in length, varying with the age, is formed at the upper end of the tap- root. This form persists during the first 8 to 12 years, after which its identity becomes lost through the increasing thickness of the annual accretions. It is significant that the capacity for sprouting is coinci- dent with the period during which the root maintains this character- istic form. During this period adventitious stem buds are present and may readily be seen along the horizontal section of the root. The corky bark here is unusually thick, affording a high degree of protection against ordinary fires. The killing of the stem is followed by the development of a colony of sprouts at the base of the stem and top of the taproot, usually from 6 to 1 2, as shown in figure 8, and not infrequently 1 6 to 20. Normally one stem (occasionally two) assumes the function of leader, the others being more or less procumbent in habit and serving as laterals or LIFE HISTORY OF SHORTLEAF PINE. 23 Sprout' feader- Fig. 8.— Sprout shortleaf pine following fire, showing new upright stem, secondary sprouts,or "laterals/ and characteristic crook of the taproot. Three-year-old coppicefrom 7-year-old seedling parent. (Drawn from actual specimen.) 24 BULLETIN 244, U. S. DEPAETMENT OF AGRICULTURE. feeders. In the organization of the sprout colony, the correlation of the two classes of vegetative buds of the tree is thus carried out. In producing normally a single new upright stem, shortleaf resembles the hickories, in contrast to the oaks and chestnut, which commonly mature several main stems. In open situations and miderstocked stands a tendency to develop twin stems is sometimes seen in vigorous stands of shortleaf. A tendency to increase the number of stems above two appears to be caused directly by unfavorable factors of age, weakness of the parent, poor light supply, or climatic conditions. For example, as many as 42 coordinate upright stems have been counted on a stump 4 inches in diameter, cut in midsummer. In coppice stands up to 50 years old, a few twin trees will usually be found. The oldest tree of undoubted sprout origin observed was 226 years. 1 Table 7. — Height growth of doviinant shortleaf pine in pure, well-stocked stands of fire coppice origin. ^ Age (years). Height (feet). Age (years). Height (feet). 1.3 10 18.3 9 2.7 4.2 5.8 7.5 9.5 11.6 13.9 16.1 11. 20.6 3 12 23.3 26.0 5 14 28.8 6 15 31.7 16 34.7 37.9 9 18 41.0 1 Based on 100 individual trees and the average trees for 8 sample plots 9 to 18 years. An 18-year-old coppice stand, near Glenville, Nevada County, Ark., averaged 248 trees per acre. Of these, 71 trees had two stems each, 7 had three steins, and 1 had four stems, or a total of 336 stems per acre. Thus 33 per cent of the trees had more than one stem. The sprout origin of the stand was completely identified, but there is no record whether the cause was fire or chopping to clear a pasture. The stand was vigorous and averaged 44 feet high. The average diameters of all stems was 6.3 inches, while that of the trees proper, or each tree colony taken as a unit, was 7.4 inches. Three colonies of twin trees and some single stems are shown in Plate V. 1 A large twin-stemmed tree with single root system exposed by erosion on a stream bank. There were others of nearly the same size and form in the same stand. LIFE HISTORY OF SHORTLEAF PINE. 25 Table 8. — Number of trees per acre and number of tree stems per acre in 18-year-old coppice shortleaf stand, Nevada County, Ark. Diameter breast high (inches). Trees per acre.' Total stems per acre. Stems per tree colony. Total. 1 2 3 4 2 6 28 24 9 28 27 34 6 6 1 6 29 36 47 37 39 8 6 1 6 1 8 27 18 10 5 2 30 4 3 3 1 1 53 5 72 C7 9 1 10 1 . . . 1 i Total 1G9 71 1 7 1 1 248 336 ' Individual trees with one or more stems, as the case may be. As a result of the tree's vigorous coppicing during early life, short- leaf occurs characteristically in even-aged stands. A fire after 6 to 8 years reduces to a single age class all the several ages of young growth that may have come in during the period. This has been found to be the case in all of the regions studied. It is significant in this connection that in one region of abundance and good develop- ment of shortleaf/ two age classes strongly predominated throughout the whole stand. One group consisted of pure stands from 160 to 180 years old and the other of similarly pure stands from 60 to 70 years. The average between the two groups is 105 years. This may be looked upon as indicating the occurrence of periods of either tor- nadoes or unusually destructive crown fires. The 60-year-old age class is especially abundant over the region. Old local records may possibly confirm this supposition of some unusual occurrence of the sort indicated between the years 1848 and 1852, SEASON OF YEAR. In common with the broadlcaf species, the sprouting takes place least actively following midsummer cutting. Pastures and rights of way are thus commonly treated. In one instance a pasture con- tained a good stand of vigorous shortleaf-pine sprout saplings, 4 years old and from 6 to 10 feet high, representing the third generation of coppice from winter or early spring cutting. Along railroad rights of way in the Arkansas region, it is conmion to see dense sprout thickets of shortleaf pine due to repeated mowing. The forest-fire season occurs during the fall and late winter. This is during the period of vegetative inactivity, and such burnings generally result in vigorous sprout growth the following spring. 1 Montgomery and Pike Counties In western central Arkansas. fOREST RESOURCES I IRRARY 26 BULLETIN 244, U. S, DEPARTMENT OF AGRICULTURE. METHOD OF DETERMINING SPROUT ORIGIN. Determination of the sprout origin of sliortleaf pines during early- life is possible by means of external characteristics. The presence of a colony of two or more living stems, also the presence of dead stems or stubs of the parent tree (charred in the case of fire), and the large size of the sapling or pole in relation to its age are clear evidence of coppice origin. A clean, smooth base without scars or adjacent stubs indicates seedUng origin. This evidence is sufhciont and dependable up to about the eighth year. Dead stems from 2 to 5 feet high, when killed by fire, will ordinarily be found standing at the end of the third year. In very early life sprout stands may be found to contain a considerable number of twin and triple colonies, but the number decreases rapidly with advance in age. In the latter stands, Fig. 9.— Determination of origin of shortleaf pine by basal sections at the ground: A, Tree of seedling origin; B, coppice tree 64 years old. Diameter of core, or first year's growth, is 3 times and cross-section area 8.9 times that of tree {A ) of seedling origin. (From photographs.) trees are frequently seen with dead or dying stems, forked at an acute angle or emerging from their sides, at distances a few feet above the ground. Following the first 6 to 10 years no external characteristics are usually apparent except occasionally multiple living stems. The first year's stem growth of trees of seedling origm is about as thick as a darning needle and 2 to 4 inches high, while the corresponding growth of young coppice sprouts is commonly as large as an ordinary lead pencil in diameter and about double its length. (Fig. 9.) The following few years' growth in each case is on a proportional scale. Thus the character of early growth, particularly that of the first year, recorded in the base of the tree and visible when the tree is cut level with the ground, affords a dependable record of the origin of the tree. Coppice trees, furthermore, usually have some of the dead stubs of LIFE HISTORY OF SHORTLEAF PINE. 27 the former generation embedded at their bases. (Fig, 10.) In most cases fire has been the cause of the sprouting, and since both the inclu- sion of charred stubs and the size of the core can readily be ascer- Lateral root Taproot Fig. 10.— Vertical section through base of 18-year-old, thrifty shortleaf pine of coppice origin, inclosing stub of parent stem. (From photograph.) tained, if present, by an examination of the extreme base of the tree, these marks embedded similarly in a number of trees selected at random will serve to confirm the coppice origin of the whole stand. An indication of origin may be seen in low-cut stumps ^ in logging 1 In Arkansas 6 to 9 Inches high for small trees and 1 foot for the larger ones are customfffy heights. 28 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. areas, tlie core of coppice being composed of large conspicuous rings in contrast to the small rings of seedling trees. ECONOMIC VALUE. Fire as a menace to young pine in great measure prevents capital from going into what otherwise appears to be a paying investment. Wliite pme in New England is a well-known example. The case is somewhat different with shortleaf, in which practically the only fire loss is from exceptionally hot fires which destroy large sapUngs or pole stands too large to sprout. Repeated burning in the dormant seasons of the year, when almost all fires occur, seems to offer no appreciable setback for at least three sprout generations. Therefore the element of fire risk in the production of all important eastern coniferous species is reduced to the minimum in shortleaf pine by its vigorous sprouting habit. This feature highly recommends the species for profitable managment throughout its range. GROWTH. The long growing season throughout most of its range and its inherent vigor make shortleaf pine a tree of rapid height growth. In situations of equal favorableness it is more rapid than longleaf pine and only slightly less so than loblolly pine. On average upland soils typical of most of its range it excels its most common associates among the oaks and hickories. In Arkansas and adjacent States, on the better sites bigbud and bitternut hickories are distinctly below it, yellow and Spanish oaks nearly equal it, and sweet gum slightly exceeds it m height growth. In the Piedmont and Arkansas regions height growth is not widely different on similar qualities of site. Table 9 shows the rate of growth and relation of heights to age for the two reo;ions.^ Table 9. — Height growth of shortleaf pine, based on Carolina.'^ in Arkansas and North V.^ESTERN ARKANSAS. Age (years). Height. Age (years). Height. Maximum. Average. Minimum. Maximum. Average. Minimum. 20 Feet. 51 56 59 62 64 66 68 69 71 72 74 75 76 78 Feet. 45 50 64 57 60 62 64 65 66 67 69 70 71 72 Feet. 37 43 48 52 54 57 59 60 62 63 64 65 65 66 90 Feet. 79 80 81 83 85 87 .89 90 91 92 93 93 Feet. 73 74 74 76 77 78 79 80 81 81 82 83 Feet. 67 25 95 30 100 68 110 70 45 130 71 50 140 71 55 150 71 60 160 72 170 72 70 ISO 72 75 190 72 80 200 73 85 1 Table 7 shows the height growth of shortleaf known to be of coppice origin. 2 The Arkansas table is based on age-height measurements of 285 trees and diameter-height of 3,214 trees; the North Carolina table is based on age-height measurements of 332 trees and diameter-height of 384 trees. LIFE HISTORY OF SHORTLEAF PINE. 29 Table 9. — Height growth of shortleaf jrine, based on age, in ArJcansas and North Carolina — -Continued . PIEDMONT REGION, NORTH CAROLINA. Age (years). Height. Age (years). Height. Maximum. Average. Minimum. Maximum. Average. Minimum. 5 Feet. 22 4S 63 69 71 73 74 75 Feet.' 13 29 42 50 57 61 63 65 Feet. 45 Icet. 75 76 76 i Feet. 67 68 69 70 70 70 71 Feet. 40 10 ih 15 20 25 29 33 36 50 55 43 45 20 60 4S 25 65 49 30 70 80 40 55 During early life the terminal leader of shortleaf pine commonly forms from two to four secondary or false terminal nodes during the growing season. These are accompanied by false rings of growth in the wood, usually plainly marked and apt to be mistaken for true rings. The influence of side light upon height growth is well illustrated in figure 5, showing a 10-year-old stand of shortleaf with the east and west side light cut ofi' by an adjacent stand. The heights increase from 2 feet near the margin to 22 feet under full hght. This illus- trates very well the need of light for development, and, at the same time, the power of endurance of shortleaf under limited light supply. A 9-year-old stand with 3,800 trees per acre averaged 19 feet high as compared with only 16 feet for a near-by stand of the same age and on similar soil with 12,200 trees per acre. Two adjacent young stands, similar in all points except tree density, averaged 9 feet high for 4,100 trees per acre and 5 feet high for 32,000 trees per acre. DIAMETER. The rate of diameter growth of shortleaf pine is intermediate be- tween that of loblolly and that of longleaf pine, the slowest of the important southern pines. Besides the well-defined annual rings of wood which clearly record diameter growth, from two to four ter- minal nodes in the stem of the tree, accompanied by shght resting periods in the tree's activity, usually occur during the period of vigorous growth in earlier Ufe. These growth periods are recorded by fine lines of denser wood within the true annual rings. Periods of injury, caused by insect attack, fire, or severe drought during which growth is temporarily checked, usually have the same effect. Such fines, forming false rings, are freciuent in shortleaf pine, and must be distinguished in examining a cross section for age. Prominent bands of wood stained brown in color are particularly apt to be found in 30 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. young shortleaf and erroneously mistaken for true annual rings of growth. Diameters throughout this bulletin, unless otherwise stated, are measured at breast height (4^ feet above the ground). Table 10 shows the diameter growth based on age for the Piedmont region of North Carolina and for western Arkansas. The tables may be con- sidered as broadly applicable to large areas within the two specified regions, since differences in growth over large areas are not important except as caused by local variation in quality of situation. Table 10. — Diameter growth of shortleaf pine, on the basis of age, in Arkansas and North Carolina.^ WESTERN ARKANSAS. Age (years). Diameter breast high. Age (years). Diameter breast high. Maximum. Average. Minimum. Maximum. Average. Mmimum. Inches. 7.2 8.6 9.9 11.0 12.0 12.8 13.6 14.4 15.1 15.7 16.3 16.9 17.5 18.0 Inches. 5.7 7.0 8.1 9.1 10.1 10.9 11.7 12.3 12.9 1.3.5 14.0 14.5 15.0 15.5 Inches. 4.3 5.4 6.4 7.4 8.2 9.0 9.7 10.3 10.8 11.3 11.8 12.2 12.6 12.9 90 Inches: IS. 5 19.0 19.4 20.3 21.1 21.7 22.3 22.8 23.2 23.6 23.9 24.1 24.3 Inches. 15.9 16.3 16.6 17.3 17.8 18.3 18.7 19.0 19.3 19.6 19.7 19.9 20.1 Inches. 95 95. 13.6 30 100 13.8 110 14.2 40 120 14.6 130 14.9 50 140 15.1 55 150 15. 3 60 160 15.4 65 170 15.5 70 180 15. 6 190 15.7 80 200 15.8 85 PIEDMONT REGION, NORTH CAROLINA. 2.0 5.9 9.2 11.6 13.3 14.5 15.6 16.5 45, 50, 55, 60 65 70 75, 80 17.1 10.5 17. 6 11.0 18.0 11.4 18.4 11.7 18.7 12.1 19.0 12.4 19.2 19.4 13.0 4.5 5.0 5.4 5.8 6.1 6.4 1 The table for Arkansas is based on breast-high diameter measxu-ements of 285 trees and 34 trees repre- senting the average of even-aged plots; the North Carolina table is based on decade measurements on 332 stumps, 26 to 89 years old. The close relation between tree density and growth in diameter is illustrated in Table 11, compiled from measurements on unit areas of different density of trees of a 30-year-old fully stocked shortleaf stand. In seven consecutive sample areas of one-tenth acre each, the size of the diameter class prevailing on each plot increased regu- larly with a corresponding regular decrease in the number of trees per acre. So far as is known this close relation holds true for all pure stands of shortleaf pine. LIFE HISTORY OF SHORTLEAF PIXE. 31 Table 11. — Relation of tree density and diameter grov.th in 30-year-old pure stands of shortleaf of varying densities, Arkansas National Forest} Prevailing diameter class (inches).2 Tree den- sity (trees per acre). Decrease (trees per acre). Prevailing diameter class (inches).^ Tree den- sity (trees per acre). Decrease (trees per acre;. 4 800 720 640 560 8 475 390 300 210 85 80 80 80 10 7 . ... 1 11 90 » Based on seven plots in the same stand of varying density, but having uniform soil conditions. * The diameter class having the largest number of trees in the individual stand. VOLUME GROWTH. The merchantable contents of a tree obviously depends upon total height and diameter taken at successive points along the stem. The rise in percentage of the rate of increase in the volume of shortleaf pine in common with most trees culminates at a comparatively early age, considerably prior to the year of maximum production of wood for the individual tree. Furthermore, the highest annual production of wood is reached somewhat earlier than the production of saw timber. In stands of relatively ecjual density those on the poorer sites and near the margin of natural distribution reach the maximum rate of volume production at a later age than similar stands on more favorable sites and more centrally situated within the region of distribution. For example, the individual trees in stands in Missouri, West Virginia, and New Jersey apparently show the gi'eatest annual wood increment at about 70 years, but in North Carolina the culmi- nation is reached at about 50 years, and in Arkansas at about 35 to 40 years.^ The contents in board feet and cubic feet of trees of different ages, up to 80 years, for two qualities of site, are shown in Table 12. Table 12. — Volume of shortleaf pine in North Carolina, hosed on age for two site classes. [Based on diameter growth of 332 trees, and volume table. Stump height 1.5 feet for trees 17 inches and over.] , 1 loot for trees 6 to 16 inches; Saw timber. Solid contents. 2 Age (years). Scribner rule. Doyle rule. Quality Quality Quality Quality Quality Qu^ality 15 Boardfeet. 51 100 147 186 221 251 275 2% 315 331 345 357 369 381 Boardfeet. Boardfeet. 50 87 125 160 191 216 237 255 271 284 295 306 316 Boardfeet. Cubic feet. 13.5 24 34 43 50 56 61 65 69 72 75 78 80 82 Cuhicfeet. 20 6 23 38 51 63 75 86 96 105 113 121 129 135 3 11 17 24 32 39 46 53 60 66 73 79 2.6 6.7 10.3 13.8 16.7 19.3 22.0 24.0 26.0 28.0 29.0 31.0 32.0 25 30. . . . 35 40 45 50 55. 60 65 70.... 75 80 » For volume tables of shortleaf pine based upon height and logs per tree, see a forthcoming bulletin on the Importance and management of shortleaf pine. * Total volume of stem, including bark, between stump and top diameter, outside bark, of 5.5 inches. 32 BULLETIN 244, U. S. DEPARTMENT OF AGRICULTURE. RECOVERY AFTER SUPPRESSION. Shortleaf pine possesses to a high degree the abihty to recover after suppression. This feature is well exhibited in a rapid increase in diameter growth following an increase in the supply of light. Events of any sort which produce changes in stand densities are recorded in quite a remarkable manner by shortleaf pine. 8 £QU/y/?l ^NT n/Ay ^j^r£/? Ol/r6/D£ S /!/?/< Of r/?££2.^ ^* ^xx >y5-CKX r y^ J ^ / ^ \ff / S V 1 /fi 0> k i r ^^ / ^ / ^ /f V fj K fi