间伐强度对长白山红松天然次生林林分结构的影响OA

[Objective]This study aims to determine the appropriate thinning intensity for Pinus koraiensis broadleaved forests in the Changbai Mountain region from a stand structural perspective,providing scientific support for improving the quality and ecological functions of natural secondary Pinus koraiensis forest resources in this region.[Method]P.koraiensis broadleaved forests in the Changbai Mountain region were selected as the study subject.In 2014,different thinning intensities were applied(control(no thinning),light,moderate,and heavy thinning).Using tally data from 2022,we analyzed the changes in the vertical and spatial structure of the forest stands along the thinning gradient.A comprehensive evaluation of the spatial structure for each thinning treatment was conducted using the unit circle and squared mean distance index(FSS),and the optimization degree of different management intensity on stand structure was discussed.[Result](1)Thinning promoted the growth of trees in the middle canopy layer.Under light and moderate thinning,the peak of the diameter distribution curve shifted rightward,and the tree diameter increased by 16.02%and 20.94%respectively compared with the control.All thinning intensities facilitated the accumulation of P.koraiensis volume in the middle forest layer.(2)The zero-order distribution results indicated that stand crowding gradually decreased with increasing thinning intensity,while mingling initially,increased and then began to decline under moderate thinning.(3)The multivariate distribution results showed that,relative to the control,light thinning increased the proportion of sparsely and randomly distributed individuals among the four major tree species by 25.44%.Moderate thinning mainly altered the horizontal distribution patterns and size differentiation,resulting in a 30.60%increase in the proportion of subdominant trees.Heavy thinning primarily affected crowding,increasing the proportion of individuals in a very sparse state from 8.17%to 40.11%.(4)Comprehensive forest spatial structure evaluation revealed that thinning improved certain structural attributes;however,only light thinning enhanced overall spatial structural quality.[Conclusion]Light thinning most effectively optimized stand spatial patterns in natural secondary Pinus koraiensis broadleaved forests,enhanced canopy stratification complexity,and facilitated the growth of small-and medium-sized trees.It also strengthened the competitive dominance of P.koraiensis,thereby accelerating positive forest succession.