浙江定海次生林内物种丰富度与生物量和生产力关系的环境依赖性

迄今生物多样性与生态系统功能关系的研究主要在物种组成随机配置的人工生态系统中进行, 在自然生态系统中研究较少, 且未考虑环境因子如何影响生态系统功能及其与生物多样性的关系。本研究选取亚热带广泛分布的次生林为研究对象, 利用模型拟合的方法, 探讨亚热带次生林中物种丰富度与生物量和生产力之间的关系, 以及环境因子(海拔、坡度、坡向、土层厚度)和次生林恢复时间(林龄)对生物量、生产力、物种丰富度与生物量和生产力间关系的影响。结果表明, 当不考虑环境因子时, 物种丰富度与生物量之间存在显著的线性正相关关系, 而与生产力之间存在显著的二次关系(先增加后减少的驼峰型)。当考虑环境因子时, 个体密度和土层厚度对生物量具有显著影响, 而环境因子对生产力并无显著效应。在坡度较陡、坡向朝南及土层较厚的环境条件下, 物种丰富度与生物量具有显著的线性正相关关系; 而在坡度较缓、坡向朝北及土层较薄的环境条件下, 物种丰富度不影响生物量。在较高海拔环境条件下, 生产力随物种丰富度先增加后减少(驼峰形状), 而在其他环境条件下, 生产力均不响应物种丰富度。以上结果说明自然森林生态系统中物种丰富度与生物量和生产力的关系存在差异, 且其相互间的关系依赖于环境因子。

Relationships between species richness and biomass/productivity depend on environmental factors in secondary forests of Dinghai,Zhejiang Province

Experimental studies of the relationship between biodiversity and ecosystem functioning (BEF) have mainly been conducted in artificial ecosystems with randomly assembled species, highlighting the need of testing this relationship in real world. In particular, these studies did not consider the effects of environmental factors on the relationship between biodiversity and ecosystem functioning. Hence, we used secondary forests, which are widely distributed in the subtropics, as research objects. We used model fitting methods to study the relationship between species richness and biomass/productivity. Meanwhile, we also explored the effects of environmental factors (e.g., elevation, aspect, slope, and soil depth) on biomass and productivity and on BEF relationships. Our results showed that there was a significant linear correlation between species richness and biomass, and a quartic correlation between species richness and productivity (i.e., humped curve) when environmental factors were not considered. Considering that biomass was significantly affected by stem density and soil depth, while productivity was not affected by environmental factors, we found that only under the environmental conditions characterized by steep slopes, south aspects, or higher soil depths, was species richness significantly correlated with biomass. The relationship between species richness and productivity showed a significant quadratic correlation under higher elevation, but not under any other environmental conditions. These results suggest that the relationship between species richness and productivity is different from the relationship between species richness and biomass, and both these relationships depend on environmental factors.