揭示林分空间结构对桉树人工林地上生物量的影响机制,可为优化林分空间结构、提升其固碳能力提供理论依据。以广西国有黄冕林场2~7 a生巨尾桉人工林为研究对象,选取角尺度、大小比数、开敞度和竞争指数表征林分空间结构,采用逐步回归和灰色关联分析方法,识别不同生长阶段影响地上生物量积累的关键空间结构因子,并探究其与地上生物量的动态关系。结果表明:1)向后逐步回归模型的决定系数(R²)为0.928,模型拟合优度高。大小比数、开敞度和竞争指数与地上生物量呈显著负相关(P<0.05)。2)开敞度的回归系数绝对值最大(1 480.402),其对地上生物量累积的负向影响权重最大,为主导因子。3)空间结构因子与地上生物量的关联性随林龄呈动态变化,在生长初期(2~3 a),角尺度和大小比数对地上生物量灰色关联度较高;随着林龄增长,竞争指数的灰色关联度显著增加并逐渐成为主导因子;开敞度与地上生物量的灰色关联度整体较高,随林龄增长呈现出“降低-升高-降低-升高”的波动变化趋势。为充分提高林地资源利用率并增强地上生物量积累能力,建议在巨尾桉生长初期(2~3 a),优先优化林木相对大小(大小比数)与空间分布格局(角尺度);进入近熟林阶段后(4~7 a),通过间伐降低种内竞争压力(竞争指数);在整个生长周期中,维持适宜的开敞度。

This study elucidates the mechanisms through which stand spatial structure influences above-ground biomass(AGB)in Eucalyptus grandis×urophylla plantations,providing a theoretical basis for optimizing stand spatial structure and enhancing carbon sequestration capacity.Using Eucalyptus grandis×urophylla plantations aged from 2 to 7 years in Guangxi’s Huangmian State-owned Forest Farm.Stand spatial structure was characterized using the uniform angle index,size ratio,opening degree,and competition index.Backward stepwise regression and grey relational analysis were employed to identify key spatial structure factors influencing AGB accumulation across distinct growth stages.The regression model exhibited high explanatory power(R²=0.928).Size ratio,opening degree,and competition index showed significant negative correlations with AGB(P<0.05).Opening degree demonstrated the strongest inhibitory effect on AGB,evidenced by the largest absolute regression coefficient(-1480.402).Grey relational analysis further revealed dynamic age-dependent relationships between spatial structure factors and AGB changes.Early growth stages(2 to 3 years),uniform angle and size ratio exerted dominant influences on AGB.Pre-maturation stages,competition index emerged as the primary limiting factor.Opening degree maintained consistently high relevance across all stages,though its association with AGB exhibited non-monotonic fluctuations with stand age.To optimize resource utilization and AGB accumulation,optimize tree size hierarchy(size ratio)and spatial distribution(uniform angle)at early growth stages(2 to 3 years),implement thinning to alleviate competition pressure(competition index)at near-maturity stages(4 to 7 years),and sustain appropriate canopy openness(opening degree)throughout the rotation cycle.These stratified interventions provide a scientific basis for precision forestry aimed at carbon sequestration enhancement.