School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China; Forest Ecosystem Research and Observation Station in Putuo Island, Zhoushan, Zhejiang 316100, China; Tiantong National Forest Ecosystem Observation and Research Station, Ningbo 315114, Zhejiang, China.
Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada T6G 2E3.
Sci Total Environ. 2017 Jan 1;574:654-662. doi: 10.1016/j.scitotenv.2016.09.022. Epub 2016 Oct 14.
Subtropical forests are globally important in providing ecological goods and services, but it is not clear whether functional diversity and composition can predict aboveground biomass in such forests. We hypothesized that high aboveground biomass is associated with high functional divergence (FDvar, i.e., niche complementarity) and community-weighted mean (CWM, i.e., mass ratio; communities dominated by a single plant strategy) of trait values. Structural equation modeling was employed to determine the direct and indirect effects of stand age and the residual effects of CWM and FDvar on aboveground biomass across 31 plots in secondary forests in subtropical China. The CWM model accounted for 78, 20, 6 and 2% of the variation in aboveground biomass, nitrogen concentration in young leaf, plant height and specific leaf area of young leaf, respectively. The FDvar model explained 74, 13, 7 and 0% of the variation in aboveground biomass, plant height, twig wood density and nitrogen concentration in young leaf, respectively. The variation in aboveground biomass, CWM of leaf nitrogen concentration and specific leaf area, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf explained by the joint model was 86, 20, 13, 7, 2 and 0%, respectively. Stand age had a strong positive direct effect but low indirect positive effects on aboveground biomass. Aboveground biomass was negatively related to CWM of nitrogen concentration in young leaf, but positively related to CWM of specific leaf area of young leaf and plant height, and FDvar of plant height, twig wood density and nitrogen concentration in young leaf. Leaf and wood economics spectra are decoupled in regulating the functionality of forests, communities with diverse species but high nitrogen conservative and light acquisitive strategies result in high aboveground biomass, and hence, supporting both the mass ratio and niche complementarity hypotheses in secondary subtropical forests.
亚热带森林在提供生态商品和服务方面具有全球重要性，但目前尚不清楚功能多样性和组成是否可以预测这些森林的地上生物量。我们假设，高地上生物量与高功能发散（FDvar，即生态位互补）和特征值的群落加权平均值（CWM，即质量比；由单一植物策略主导的群落）相关。结构方程模型被用于确定林分年龄的直接和间接影响以及 CWM 和 FDvar 对中国亚热带次生林 31 个样地地上生物量的剩余影响。CWM 模型分别解释了地上生物量、幼叶氮浓度、植物高度和幼叶比叶面积变异的 78%、20%、6%和 2%。FDvar 模型分别解释了地上生物量、植物高度、嫩枝木材密度和幼叶氮浓度变异的 74%、13%、7%和 0%。联合模型解释了地上生物量、叶片氮浓度和比叶面积的 CWM、植物高度、嫩枝木材密度和幼叶氮浓度的 FDvar 变异的 86%、20%、13%、7%、2%和 0%。林分年龄对地上生物量有强烈的直接正向影响，但对地上生物量的间接正向影响较低。地上生物量与幼叶氮浓度的 CWM 呈负相关，与幼叶比叶面积的 CWM 和植物高度呈正相关，与植物高度、嫩枝木材密度和幼叶氮浓度的 FDvar 呈正相关。叶片和木材经济谱在调节森林功能方面是解耦的，具有多种物种但高氮保守和光获取策略的群落导致高地上生物量，因此，支持次生亚热带森林中质量比和生态位互补假说。
