Paper published as Bulletin 18 in the UM Bulletin Forestry Series. This paper is a reprint from Proceedings of the Montana Academy of Sciences, volume 19, pp. 135-141.https://scholarworks.umt.edu/umforestrybulletin/1007/thumbnail.jp

Cox, C. S.

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University of Montana

University of Montana ScholarWorks at University of Montana Bulletin: Forestry, 1949-1982 University of Montana Publications 1-1959 Root Distribution in Ponderosa Pine Stands Growing on Three Soils C. S. Cox Montana Forest and Conservation Experiment Station Follow this and additional works at: https://scholarworks.umt.edu/umforestrybulletin Let us know how access to this document benefits you. Recommended Citation Cox, C. S., "Root Distribution in Ponderosa Pine Stands Growing on Three Soils" (1959). Bulletin: Forestry, 1949-1982. 8. https://scholarworks.umt.edu/umforestrybulletin/8 This Article is brought to you for free and open access by the University of Montana Publications at ScholarWorks at University of Montana. It has been accepted for inclusion in Bulletin: Forestry, 1949-1982 by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact scholarworks@mso.umt.edu. If ARCHIVESRoot Distribution in Ponderosa Pine Stands• Growing on Three Soilsc. s. coxMontana Forest and Conservation Experiment StationSCHOOL OF FORESTRYMontana State UniversityMissoula, MontanaBulletin No. 18 1959a reprint fromProceedings of the Montana Academy of SciencesVol. 19 pp 135-141Proceedings of the Montana Academy of Sciences 19:135-141.Root Distribution in Ponderosa Pine Stands Growing on Three SoilsGene S. CoxThe root systems of forest trees are of interest in the study of forest soils because of the intimate association between the soil and the roots of trees, and the effect of soil properties on the absorption of water and nutrients. The ex­tent and efficiency of the root system determines to a large degree the quantity absorbed of the available water and nutrients in the soil.The purpose of this investigation was to determine the distribution of roots in ponderosa pine stands in the different soil horizons and, if possible, to re­late their distribution to soil texture.Relatively little information is available on the extent of root systems of mature, forest-grown trees. Much of the information has been obtained by exca­vating the root systems of individual trees, and since this is a laborious and expensive method, few observations have been made. Weaver and Kramer (9) found that the roots of mature bur oak extended laterally 20 to 60 feet and vertically to a depth of 14 feet through soil which was fairly heavy in texture.Longleaf pine growing on a sandy soil was found by Heyward (6) to have a tap root over 14 feet deep and lateral roots up to 75 feet long. McQuilkin (8) reported that pitch pine, 12 to 30 years old, growing on sandy soils had lateral roots 25 to 35 feet in length.In a study of root distribution on Colorado watersheds, Berndt and Gibbons (1) noted that ponderosa pine, Douglas fir, and lodgepole pine roots reached maximum depths between 4 and 5.6 feet, except where downward penetration was limited by bedrock. Quaking aspen had some laterals up to 48 feet in length? other tree species had laterals less than one-half this length.Coile (3) studied the root concentration in five forest types in the lower Piedmont of North Carolina. He found that the concentration of roots less than J»1 inch in diameter increased rapidly in the Ai and A2 horizons during the first 20 to 30 years of the pine stage in the succession toward a.n oak-hickory climax forest. Concentrations increased at a much slower rate after this stage. Sub­soil root concentrations did not increase after the pine stands were 20 years of 59e. He concluded that after fully stocked forest stands have reached a certain J9e, the number of small roots in the surface soil reaches a near constant. This is considered to be the root capacity of the soil.In a study of the soil characteristics influencing the distribution of white i>ine roots in New Hampshire, Lutz, Ely and Little (7) reported the greatest con­centration of roots to be in the upper soil horizons. Factors causing the con­centration of roots in this area were: more favorable soil texture and structure; *19her moisture holding capacity; higher organic matter content; higher content ■ ’f total nigrogen; and higher total exchange capacity and higher content of ’’xchangeable bases.Gaiser and Campbell (5) found that the concentration and weight of roots Mne-fourth inch and less in diameter decreased rapidly in succeedingly deeper |’°il horizons in white oak stands in Ohio. Root concentrations were found to >"e nearly constant after the stands reached an age of 30 years, and were not < ffected by site quality, topography, or stand density.MethodsEven-aged ponderosa pine stands on each of three soil types were selected135Proceedings of the Montana Academy of Sciencesas locations for soil wells from which data on the distribution and concentrat: of roots were obtained. The stands were growing on a coarse-textured, a media textured, and a fine-textured soil. The mean ages of the stands were 51, 75, and 78 years. ’Soil wells were located with one end of the vertical face tangent to the trunk of a dominant ponderosa pine. The face of the well extended outward fron the reference tree along a contour. The wells were 120 inches long and 48 inch deep. One wall of the trench was divided into 12-inch squares by means of a $r made of cord. Root ends were charted on cross section paper, using symbols to denote the various size classes recognized. In order to avoid missing any root it was necessary carefully to work over the vertical wall with a sharp pointed instrument. Boundaries of all soil horizons were mapped.The soil profile was described and samples taken from each horizon for lab fatory analyses. Mechanical composition was determined by the hydrometer metho, PH samPles.was determined electrometrically with a Beckman met.The age, height, and diameter of the trees of the stand were recorded. Thr density of the species comprising the ground vegetation was noted on four one- quarter mil acre quadrats located adjacent to the soil wells.SoilsThe three soils in which root distribution was studied belong to the Gray ooded great soil group. The Gray Wooded soils are characterized by a well- developed platy A2 horizon, a blocky B horizon with a distinct accumulation of clay,and an ovexull gray appearance (4). If developed from calcareous parent material, a zone of calcium carbonate is usually present; but two of the profile examined, which were developing in non-calcareous materials, contained no free lime. Although the prominent gray A2 horizon would seem to indicate leaching comparable to that occurring in the Podzols, the Gray Wooded soils are usually neutral to mildly acid in reaction above the calcareous materials. One of the most striking features of these soils is their high base status which in the B£ horizon may be 8 to 10 times that of a typical Podzol profile (10).The three sites selected for this study were on a coarse-textured soil, Half Moon sandy loam, a medium-textured soil, Greenough silt loam (tentative series name, subject to final correlation), and a fine-textured soil, Lubrecht loam (tentative series name, subject to final correlation).Half Moon sandy loam is a minimal Gray Wooded soil developing in coarser textured glacial-lacustrine sediments. The profile sampled exhibited a duff mull humus layer 2 inches thick. Texture graded from a sandy loam surface soil to a silt loam subsoil (Table 1, Fig. 1). Horizons were poorly differentiated and boundaries were indistinct. Soil reaction was very slightly acid.The medium-textured Greenough soil is a medial Gray Wooded soil developing in calcareous Tertiary age sediments, the so-called Bozeman "lake beds". The S°il Wa? overlain with a duff mull humus layer from 2 to 3 inches in thickness. Horizon development was pronounced. The texture varied from a silt loam surface soil, through a clay loam B horizon, to a silt loam parent material (Table 1, Fig. 1). Soil reaction varied from medium acid in the A horizon to moderately alkaline in the parent material.The Lubrecht series are maximal Gray Wooded soils developing in the same parent materials as the Greenough soils. The striking features of the profile examined were the prominent light colored A2 horizon and the very strongly de­veloped blocky clay B2 horizon; the latter had prominent clayskins on the surface1 and in the pores of the peds. The clay content, as shown in Table 1 and Figure li is quite high. Soil reaction was slightly acid to strongly acid. The duff mull136Cox: Root DistributionFig. 1. Clay content of Half Moon, Greenough, and Lubrecht soils.137iProceedings of the Montana Academy of Sciencesorganic layer was 2 inches thick.ResultsThe soil well in Half Moon sandy loam was located in a ponderosa pine stand 75 years of age. The density of the ground vegetation is given in Table 2. Root distribution throughout the profile (Table 3, Fig. 2) was sometdiat more uniform than in the Greenough soil and considerably more so than in the Lubrecht plot.Table 2. Density of understory vegetation on four one-quarter mil acre quadratsTotal number of roots was intermediate between the two other areas — 4,373 as compared to 4,993 and 4,032 for the Greenough and Lubrecht soils (Tables 3, 4, and 5). The number of roots over 0.1 inch in size was almost twice that of the138Table 1. Mechanical composition and pH of Half Moon, Greenough, and Lubrecht soils. Half Moon Greenough Lubrecht________  Horizon Percent of Percent of Percent of_________ Sand Silt Clay pH Sand Silt Clay pH Sand Silt Clay pH Ax________61.4 28.8 9.8 6.2 29.1 53.7 17.2 5.8 37.9 44.9 17.2 6.2A2 67.5 22.0 10.5 6.5 26.1 52.9 21.0 6.0 41.3 34.8 23.9 6.4B2-A2 71.1 18.2 10.7 6.5 22.3 54.7 23.0 6.3 39.6 31.9 28.5 6.4821 67.6 20.2 12.2 6.5B22 24.0 56.7 19.3 6.6 19.2 44.1 36.7 6.0 17.3 13.4 69.3 5.1B3 21.5 27.6 50.9 6.3C 28.8 43.0 28.2 6.3Deal 41.3 45-6 13-x 7-8Dca2 33.4 52.9 13.7 8.0_________ on Half Moon, Greenough, and Lubrecht soils.___________________________  ______________ Specimens per Mil Acre___________________ Species________________ Half Moon__________ Greenough__________ Lubrecht______Oregon grape 30 20 11Rose 5 5 2Snowberry 85 60Kinnikinnik - 39 —.Serviceberry - —3Douglas fir- 1 —Table 3. Root distribution in Half Moon sandy loam.Depth _____________ Number of Roots by Size______________________Horizon (inches) <0.1 0.1-0.3 0.3-0.5 0.5-1.0 1.0-2.0 >2.0________Al 0-2 479 32 1 - - -A2 2-5 574 21 3 - - -B2-A2 5-22 1638 151 32 9 2 -B21 22-43 1140 62 10 - - _B22 43-48+ 211______ 8________ -________ - _______ ___4042 274 46 9 2 -(feet) 0-1 1678 123 15 2 1 -1- 2 1132 86 22 7 1 -2- 3 633 33 4 - - -3- 4 599 32_______ 5_________ -_________ -________- .4Q42 274 46 9 2-Proceedings of the Montana Academy of SciencesLubrecht plot and was over three times that of the Greenough area*The Greenough silt loam plot was in a 51-year-old stand. This area was the only one in which kinnikinnik was present in the understory vegetation (Table 2). The total number of roots was the greatest of the three areas studied; also the only root over 2 inches in diameter found in the course of the study was mapped in this pit. There is a marked contrast in the number of roots less than 0.1 inch in size and those greater than 0.1 inch in size (Table 4).The influence of texture and structure is evident in the patterns of root distribution. The Lubrecht subsoil is the poorest medium for root growth of the three soils since it is a poorly aerated plastic clay. The concentration of roots drops abruptly below a depth of about 18 inches in this soil. The Half Moon soil is fairly well aerated throughout the entire profile as is evidenced by the more uniform distribution of roots. However, the water supplying capacity of this soil is not as favorable as that of Greenough silt loam, consequently root concen­140Table 4. Root distribution in Greenough silt loam.Depth ___________ Number of Roots by SizeHorizon__(inches) <0.1 0.1-0.3 0.3-0.5 0.5-1.0 1.0-2.0 >2.0_______Al 0^1 402 11 Z ~Z~ .~ Z------------a2 1-4 753 22 2 - - 1B2-A2 4-11 1070 37 5 4 _ _B2 11-24 1597 7 - - _C 24-33 453 1 - - _ _Deal 33-42 593 4 - - - _Dca2 42+ 31______ -_______ -________ -________  _______  ________  •4899 82 7 4 Z 7-------------(feet)0-1 2203 67 6 4 - 11- 2 1539 10 1 - _ _2- 3 828 5 - - _ _3- 4 329______ -_______ -________ -________  _______  _______________________________  4899 82 7 4 - 1 ------The ponderosa pine stand on the Lubrecht loam site was 78 years of age. Table 2 shows the species density of the understory vegetation. As shown in Table 5, this area had the smallest number of roots; over one thousand fewer roots 0.1 inch in diameter or smaller than were present in the Greenough soil.Table 5. Root distribution in Lubrecht loam.Depth Number of Roots bv Size XHorizon (inches) <0.1 0.1-Q.3 0.3-0.5 0.5-1.0 1,0^2.0 >2.0 ~~Al 0-4 1013 41 1 ~_ ~~~A2 4-11 1027 70 10 2B2-A2 11-13 257 19 3 J _ _B2 13-33 1436 29 4 ' ) _ _B3 33-48+ 117______ 1_______ -________ _________  _______  _______3850 160 18 4 Z Z ’(feet)0-1 2062 113 11 21- 2 1249 38 7 22- 3 394 8 - _ _ _3- 4 145______ 1_______ -________ _________  _______  ______3850 160 18 4 -Cox: Root Distributiontrations are lower. The Greenough soil’ is the most favorable environment for root development as a result of good aeration and moisture availability.The percentages of the total number of roots less than 0.1 inch in diameter in the upp-r foot of soil on the coarse, medium, and fine-textured soils were 42, 45, and 54 respectively} for the 0-2 foot depth the percentages were 70, 76, and 86. This concentration is primarily a result of better aeration and greater ease of root penetration than exists in the deeper soil layers.The small number of roots over 0.3 inch in diameter is very noticeable (Tables 3, 4, 5, Fig. 2). The combined total in all soil wells was 91 roots of which 20 exceeded 0.5 inch in diameter.SummaryThe distribution of roots in ponderosa pine stands growing on a coarse, medium, and fine-textured soil was measured by the soil-well method.Greatest numbers of roots were found in the medium-textured soil and the smallest number in the fine-textured soil — 4,993 and 4,032 respectively.The concentration of roots decreased markedly in succeedingly deeper ho­rizons. Over 70 percent of the roots were concentrated in the upper two feet of the soil.Very few roots over 0.5 inch in diameter were present.Literature Cited1. Berndt, Herbert W. and Robert D. Gibbons. 1958. Root distribution of some native trees and understory plants growing on three sites within ponderosa pine watersheds in Colorado. Rocky Mtn. For. and Range Expt. Station Paper No. 37.2. Bouyoucos, George J. 1936. Directions for making mechanical analyses of soils by the hydrometer method. Soil Sci. 42:225-229.3. Coile, Theodore S. 1937. Distribution of forest tree roots in North Carolina Piedmont soils. Jour. Forestry 35:247-257.4. Cox, Gene S. 1957. The altitudinal distribution of soils in western Montana. Proc. Mont. Acad. Sci. 17:7-15.5. Gaiser, Richard N. and J. R. Campbell. 1951. The concentration of roots in the white oak forests of southeastern Ohio. Central States Forest Expt. Station. Technical Paper No. 120.6. Heyward, F. 1933. The root system of longleaf pine on the deep sands of western Florida. Ecology 14:136-148.7. Lutz, Harold J., Joseph B. Ely, Jr., and Silas Little, Jr. 1937. The in­fluence of soil profile horizons on root distribution of white pine. Yale Univ. Sch. Forestry Bull. No. 44.8. McQuilken, W. E. 1935. Root development of pitch pine with some comparative observations on shortleaf pine. Jour. Agr. Res. 51:983-1016.9. Weaver, J. E. and J. Kramer. 1932. Root systems of Quercus macrocarpa in relation to invasion of prairie. Bot. Gaz. 94:51-85.10. Williams, B. H. and W. E. Bowser. 1952. Gray Wooded soils in parts of Al­berta and Montana. Soil Sci. Soc. Amer. Proc. 16:130-133.School of Forestry, Montana State University, Missoula, Montana.141

Root Distribution in Ponderosa Pine Stands Growing on Three Soils

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Root Distribution in Ponderosa Pine Stands Growing on Three Soils

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