【目的】量化生物和非生物因素对大兴安岭地区天然白桦(Betula platyphylla)林碳汇量的影响,识别制约其碳汇功能的关键可控因子,为提升该地区天然白桦林碳汇功能提供理论依据。【方法】以大兴安岭地区第7次和第8次森林资源一类调查的175块固定样地数据为基础,结合随机森林算法和结构方程模型,量化生物因子(林分、生物多样性)和非生物因子(地形、气候、土壤)对天然白桦林碳汇量的直接和间接影响。【结果】①大兴安岭天然白桦林的年均碳汇量为(1.48±0.84) t/(hm²·a)。②随机森林算法结果表明,林分特征是对碳汇量影响最大的因子(贡献度60.09%),其影响分别约为土壤指标、气候特征、地形指标、生物多样性指标的3、6、9、11倍。③结构方程模型结果显示,天然白桦林碳汇量随着郁闭度的增加而增加(总路径系数β=0.030),而随着林分平均年龄(β=-0.643)、平均胸径(β=-0.489)、平均树高(β=-0.298)、坡度(β=-0.133)、土壤有机质含量(β=-0.039)和林分断面积(β=-0.007)的增加而减少。【结论大兴安岭天然白桦林林分平均年龄、平均胸径和平均树高是影响森林碳汇量的关键可控驱动因子,在未来经营活动中,可通过合理疏伐维持多层次、多样化的森林结构,以提高森林碳汇能力。

【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.