基于随机森林和结构方程的大兴安岭天然白桦林碳汇驱动因素分析OA

[Objective]This study aims to quantify the impact of biotic and abiotic factors on the carbon sequestration capacity of natural Betula platyphylla forests in the Greater Khingan Mountains,and to identify and extract the key controllable factors that constrain their carbon sequestration function.The research provides a theoretical basis for enhancing the carbon sequestration function of natural B.platyphylla forests in this region.[Method]The research was based on data from 175 fixed plots of the 7th and 8th National Forest Inventory in the the Greater Khingan Mountains.It combined random forests and structural equation modeling(SEM)to quantify the direct and indirect effects of biotic factors(forest stand characteristics,biodiversity)and abiotic factors(terrain,climate,soil)on carbon sequestration.[Result](1)The results showed that the average annual carbon sequestration of natural B.platyphylla forests in the region was(1.48±0.84)t/(hm2·a).(2)Random forests results indicated that stand characteristics were the most dominant factor influencing carbon sequestration(contribution:60.09％),with their contribution approximately threefold that of soil indicators,sixfold that of climatic indicators,ninefold that of site condition indicators,and elevenfold that of tree species diversity indicators.(3)SEM results indicated that carbon sequestration increased with canopy density(total path coefficient β=0.030),while it decreased with stand average age(β=-0.643),diameter at breast height(DBH)(β=-0.498),stand average tree height(β=-0.298),slope(β=-0.133),soil organic matter content(β=-0.039),basal area at the stand level(β=-0.007).[Conclusion]Therefore,stand average age,stand average DBH,and stand average tree height were key manageable driving factors influencing forest carbon sequestration.In future management activities,appropriate thinning can be implemented to maintain a multi-layered and diverse forest structure,which can enhance the forest's carbon sequestration capacity.