Growth of Loblolly Pine Stands After the First Five Years of Uneven - Aged Silviculture Using Single - Tree Selection

The cjfects oftlzree levels cfresidual basal area 140,60, and 80,ft2/rac), rr~uxirnurn dbh (12, 16, and 20 in.) and site index (QO,ft) otr the grvwth qt'loblullvpine {Pjnus taeda L. i srarzds after 5 yyrof uncvcn aycd rilvici~ltrrr.~ were deterwtirzed jrnm plots located irz south Arkansas and tlorlh Z,onisiunir. Lksign~iteci 1ei)eZs of basal area and nzuximlim dbh were ac:hicved by hur-~wting; n q fncfor of 1.2 (using I irz. dB11 classes) was imposed on all plots as closely cu possible. Stand-level models were developed.for almidalper arra net volrrrwe growrh (rnrrchantiible rltbic.feer, sowtimber cubic feer, clnd sawtimber boardfeat, Doyle rule) and ltnnualper. ncre suwit.o~-gr-owth, ingl-owfh, arid mortulity c-orrrycmenfs of brzsul area growth. Growthfor all volume measures increased with an incrcasc in basalarea. Site indexdid notsignijicantly ~gfSect nten:h~zrrtahlr cr t t~i~.~j"c~~~(~i gr in'th but half apositive e&>ct on sa\vtinlber gro~vtlz in both cubic feet and board fcrf, T)oyyle. Incrrc~ses in mcz.xirnum d b f ~ decreased merchantable and sau*tinber cubic-foot growth but increased growth jio for b~crrd~foot vnlur~ze, Doyk. South. .I. A ~ I J . For. IR(.?): 128-132. N o information is available about the growth and yield of essentially pure loblolly pine stands that are managed under uneveti-aged silviculture with single-tree sclcction as the reprodtiction cutting method. The available data pertain only to loblolly-shortleaf pine stands, where Icrl,lolly pine may be the predominant specie5 hut where shortleaf pinc ( P . echinaia Mill.) is also present as acommon associate. Loblolly pine in the West Gulf Coastal Plain is usually favored over shortleaf hecallfie of tlic reputed slcrher growth and more erratic and lower sccd production of shortleaf pine. Reynolds (1959, 1969) 1-epa~ted productio~l averages over a 29-yr period Pur lublolly-shortleaf pine stands managcd by single-tree selection in southeast Arkansas (loblolly pine site index 90 ft, hase age SO) . Growtll was 84 rL31ac Fur merchantable trees ('3.6 in. cibh and largcr) and 432 bd ft (International 114-in. mle)in24 managedstands thatwerehanrested on 3-yr, 6-yr, arid 9-grcuttingcycles.Brender(1971) repurtedmerchanhblepwth of 74 ft3 ~atd 319 bd ft (International 1!4-in. rulc) for sawtimber in loblolly-shortleafpinestandsii~theGeo~-giaPied~~iot~l (luWully site index 77 ft, hase age 50). Although there wcrc minor merchantability differences bctwccn the Arkansas and Georgia smdies. the primary cause of the growth difference was site quality. Nrll t: The n ~ ~ r h o r s rhilnkrhe ArkansasF~restry Commission. Delt~cFarm and Tilnbe~, IIIC., Grurgia-PacificCnrporatinn. and PotlatrhCarporailon forthrir coopelatio~l and ass~starl~r i n llii:, s ~ u d y . More recently, Mul-pl~y and Farrar (1982a. 1983) and Parrar cr al. (1984) developed stand-level growth and yield models for IobloIly-shnitlaaf pine stands in tlre Wcsl Gulf region (site index 80 to YO ft, loblolly pine). Thcsc rnodcls predict future basal areas and current and future volumes, both cubic foot and board foot. As they are sland-level models, stand nr stock lablcs cannut be derived, and the applicable site indcx rangc i s rather narrow. Stand structure is an important adjunct of uneven-aged regulalion, but knowledge about the cffcct of structure on growth is fragmentary. Solnnlon (1977) created 12 different stand structures in a nn~thel-JI hardwoorl stand irl Ncw England by varying the total basal arca and percent basal area that was in sawtimber. He found that higher sawtimher productiu~l [incluchng ingrowth) was obtained whcrc thc proportior1 of sawtimbrr basal area was reduced. Sawtin~ber production (excluding ingrowth) was ln axi~nized where both a high sawtimher hasal ; m a and a high total basal arca were maintained. A methods-of-cutting study in south Arkansas (Baker and Murphy 1982) cornpal-ed four reproclucliurl cul ting methods. Two of itlast. rr~elhods were a 12-in. diameterliinit cr~t and singh-tree selection. The board-foot volulne production was not different between the two illethocls, even though tnuch higher densities were retained in thc singlc-trcc selection. Tn summary, 011s current knowledge uP uneven-aged stand cl ynarrlics and growth potential is quite limited, even for such 128 SJAF 18(3) 1994 Reprinted from the Southern Jourlzal of Applied Toresty, Vol. 18, No. 3, Augusl 1994. a widely studied species as loblolly pine. Consequently, a study was installed during 1983-1985 to investigate the effects of different stand and site variables on the growth and de\lelopment of loblolly pine stands that were put under uneven-aged silviculture with single-tree selection. Presented here are the initial 5-yr results.