密度调控对杉木人工林及套种阔叶树生长的影响

Effects of density regulation on the growth of Cunninghamia lanceolata plantation and interplanted broadleaved trees

合理改造杉木人工纯林,可提高林分的稳定性、维持人工林的可持续经营。本研究以安徽省青阳县窑西林场内14年生杉木人工林为研究对象,设置低密度(675株/hm^(2),KL)、中密度(825株/hm^(2),KM)、高密度(1050株/hm^(2),KH)和对照(1740株/hm^(2),CK)共4种林分密度,抚育间伐后在林下套种阔叶树(浙江楠和檫木),测定密度调控后4年内乔木及林下植被的胸径、树高等因子,分析林分密度对杉木及林下阔叶树生长发育的影响。结果表明:①密度调控后同一时期,杉木林胸径、树高、单株材积均随林分密度减小而增大,低密度林分生长指标显著大于其他林分;②相同密度杉木林的胸径、树高、单株材积均表现为随林龄的增大而增大,密度调控4年后林分生长指标与刚调整时相比均存在显著差异;③适度的密度调控可促进杉木胸径、树高和单株材积生长量的增加,中密度林分生长量最大,但是随时间的推移杉木树高和单株材积生长量下降;④林下套种阔叶树地径和树高均表现为随林分密度减小而增大,低密度林分下阔叶树生长最佳。研究表明,减小林分密度可促进杉木及林下套种阔叶树的生长,低密度林分内杉木和套种阔叶树生长最佳。由此可见,适度降低林分密度是杉木纯林实现可持续经营的有效措施。

Rational transformation of Cunninghamia lanceolata plantation can improve the stability of stand and maintain the sustainable management of plantation.In this study,a 14-year-old C.lanceolata plantation in Yaoxi Forest Farm,Qingyang County,Anhui Province,was selected as the research objects.Four stand densities were set,including low density(675 tree/hm^(2),KL),medium density(825 trees/hm^(2),KM),high density(1050 trees/hm^(2),KH),and control(1740 trees/hm^(2),CK).After thinning,we interplanted broadleaved trees(Phoebe chekiangensis and Sassafras tzumu)in the understory.The DBH and tree height factors of trees and understory vegetation were measured within 4 years after density adjustment.The results showed that:①During the same period after density adjustment,DBH,tree height,and volume per plant of C.lanceolata plantations increased with the decreases of stand density,and the growth indexes of low-density stands were significantly higher than those of other stands.②The DBH,tree height,and volume per plant of the same density of C.lanceolata plantation increased with stand age.After 4 years of density adjustment,the stand growth indexes were significantly different from those before density adjustment.③Moderate density regulation could promote the increases of DBH,tree height,and volume growth per plant of C.lanceolata.The mediumdensity stand had the largest growth,but the height and volume growth per plant decreased with time.④The ground diameter and height of interplanted broadleaved trees increased with the decreases of stand density.The growth of broadleaved trees in low-density stands was the best.Our results indicated that reducing stand density could promote the growth of C.lanceolata and understory interplanted broadleaved trees,they grow best in low density stands.Therefore,moderate reduction of stand density is an effective measure to achieve sustainable management of C.lanceolata pure forest.