抚育采伐对次生杨桦林空间结构的短期影响OA

To explore the effects of different felling intensities on the stand spatial structure of sec-ondary poplar-birch forests,four representative 1 hm2(100 m×100 m)sample plots with relatively con-sistent stand conditions in Zhangguangcailing area were selected as the research objects.Felling in-tensity gradients were set based on the breast height of the sample plots:0(control,ck),20%(light thinning,LT),30%(moderate thinning,MT)and 40%(heavy thinning,HT).Four stand spatial struc-ture parameters,including neighborhood pattern,neighborhood comparison,mingling and crowding indices,were quantified before and after felling to provide scientific basis for optimizing the spatial structure of secondary forests.The results showed that different felling intensities had varying effects on neighborhood pattern,neighborhood comparison,mingling and crowding.Quantitative analysis of neighborhood pattern indicated that after LT and MT,the horizontal distribution pattern of the stand shifted from an aggregated distribution(pre:0.534,0.521)to a random distribution(post:0.494,0.480),while HT changed changed from 0.540 to 0.521,with no significant change in the stand's horizontal distribution pattern.Neighborhood comparison showed no obvious variations across inten-sities(pre:0.488,0.492,0.509,post:0.486,0.495,0.502).The stand's mingling increased to varying degrees after felling(pre:0.681,0.774,0.657,post:0.790,0.789,0.799).The stand's crowding ex-hibited a decreasing trend after felling(pre:0.357,0.351,0.437,post:0.338,0.294,0.316).Differ-ences also existed in the effects of different felling intensities on nine major tree species.There was no obvious regularity in neighborhood pattern changes of each tree species among different felling in-tensities.Felling reduced neighborhood comparison of Betula platyphylla and Populus davidiana.MT treatment decreased neighborhood comparison of Ulmus davidiana var.japonica,Fraxinus mandsh-urica and Acer pictum Thunb.,while other species had varying degrees of increase with different felling intensities.Felling could increase mingling of each tree species,but LT and HT felling reduced min-gling of Tilia amurensisa and Albizia kalkora.Felling intensity reduced crowding of each tree spe-cies.In conclusion,felling can effectively optimize stand spatial structure and tress species composi-tion in short term,with 30%intensity(MT)demonstrating the optimal performance in adjusting neigh-borhood pattern,enhancing mingling and most significantly reducing crowding.