树冠结构对典型阔叶红松林生产力的影响

阔叶红松(Pinus koraiensis)林是东北东部山区的地带性森林植被, 阐明其生产力的影响因素, 对于理解温带森林生产力维持机制具有重要意义。该研究依托小兴安岭典型阔叶红松林9 hm²动态监测样地, 基于2005和2015年的30 m × 30 m样方内所有胸径>6.5 cm的木本植物的调查数据, 计算各样方的树冠结构复杂性、物种多样性和林分胸高断面积, 结合各样方的地形和土壤理化性质数据, 拟合结构方程模型, 定量分析影响典型阔叶红松林生产力的直接和间接因素。研究结果显示: 树冠结构复杂性和物种多样性与生产力显著正相关, 且树冠结构复杂性对生产力的影响显著高于物种多样性; 树冠结构复杂性对生产力的作用分为树冠垂直分层和树冠可塑性, 其中树冠垂直分层是树冠结构复杂性影响阔叶红松林生产力的主要因素, 而树冠可塑性无显著影响; 林分胸高断面积与生产力显著正相关, 其解释权重仅次于树冠结构复杂性, 树冠结构复杂性与物种多样性均通过影响林分胸高断面积对阔叶红松林生产力产生间接影响; 考虑不同树冠结构复杂性时, 坡度和土壤全磷含量代表的环境因素在调节生产力上发挥的作用存在差异, 移除树冠垂直分层的作用后两者与生产力呈显著的负相关关系。综上可知, 在典型阔叶红松林中, 树冠结构复杂性比物种多样性更有效地解释了生产力的变化, 同时不可忽视其他生物和非生物因素对生产力的作用。

Effects of canopy structure on productivity in a typical mixed broadleaved-Korean pine forest

Aims The mixed broadleaved-Korean pine (Pinus koraiensis) forest is a zonal vegetation type in Northeast China. Clarifying the influencing factors of productivity is of great significance for understanding the maintenance mechanism of productivity in temperate forests.Methods The study was conducted based on survey data of a 9 hm² permanent plot in a typical mixed broadleaved- Korean pine forest in the Xiaoxing’an Mountains. Census data of 2005 and 2015 for all individuals with diameter at breast height >6.5 cm within each 30 m × 30 m sub-plot were used to calculate canopy structural complexity, species diversity and stand basal area. We analyzed the direct and indirect factors affecting forest productivity using structural equation model and data on topography and soil physicochemical properties in each sub-plot.Important findings Both the canopy structural complexity and the species diversity were positively related to productivity, with canopy structural complexity having a significantly greater effect than species diversity. The effects of canopy structural complexity on productivity consisted of two attributes: the vertical stratification and the plasticity. The vertical stratification played a significant role in driving the changes in forest productivity, while plasticity had no significant effect. The stand basal area was positively related to productivity, but with less effect than the canopy structural complexity. Both the canopy structural complexity and the species diversity had indirect effects on productivity via stand basal area. However, the environmental factor representative of slope and soil total phosphorus played differential roles on productivity for varying canopy structral complexity, and it was significantly and negatively correlated with productivity after removing the effects of canopy vertical stratification. In short, in a typical mixed broadleaved-Korean pine forest, the canopy structural complexity is more crucial for explaining the diversity-productivity relationship than species diversity, and the roles of other biotic and abiotic factors in productivity should not be ignored.