Data from: Multi-trophic guilds respond differently to changing elevation in a subtropical forest

Negative relationships between species richness and elevation are common and attributed to changes in single environmental properties associated to elevation, such as temperature and habitat area. However, research has lacked taxonomic breadth and comprehensive elevation studies that consider multiple groups from different trophic levels are rare. We thus analysed 24 groups of plants, arthropods, and microorganisms grouped into six trophic guilds (predators, detritivores, herbivores, plants, bacteria and fungi) along a relatively short elevational gradient (~600 m) in a subtropical forest in south-east China. The total species richness of all organisms was not related to elevation, nor was the richness of plants, herbivores or microorganisms. However, species richness and abundance in two major trophic guilds of arthropods changed with elevation, which was mediated by changes in elevation-associated habitat properties. Specifically, deadwood mass increased with elevation, which increased detritivore richness indirectly via detritivore abundance, thus supporting the ‘more individuals hypothesis’. In contrast, lower predator richness at higher elevations was directly related to lower mean temperatures, which had no effect on abundance. Our study demonstrates that even along relatively short gradients, elevation can have strong direct and abundance-mediated effects on species richness, but with effects varying from positive to negative signs depending on local resource availability and the characteristics of groups or trophic guilds. If elevation positively influences local environmental properties that benefit a given group, richness can increase towards higher elevations. Thus, the effect of global change in mountainous regions should be evaluated within the local environmental context using multi-taxon approaches.

物种丰富度与海拔之间的负相关关系较为普遍，这类关联常被归因于与海拔相关的单一环境属性变化，例如温度与栖息地面积。然而，现有研究在类群覆盖度上存在不足，同时兼顾不同营养级多个类群的综合性海拔研究仍较为稀缺。为此，我们在中国东南部亚热带森林中，沿一条相对较短的海拔梯度（约600米），对植物、节肢动物与微生物共24个类群展开分析，这些类群被划分为6个营养功能群（trophic guilds）：捕食者、腐食者、植食者、植物、细菌与真菌。所有生物的总物种丰富度与海拔并无关联，植物、植食者或微生物的物种丰富度亦是如此。然而，节肢动物两大主要营养功能群的物种丰富度与个体数量随海拔发生变化，这一效应由与海拔相关的栖息地属性变化所介导。具体而言，枯木生物量随海拔升高而增加，进而通过腐食者的个体数量间接提升其物种丰富度，这一结果验证了“更多个体假说（more individuals hypothesis）”。与之相反，高海拔区域捕食者的物种丰富度更低，这与较低的平均温度直接相关，而温度并未对捕食者的个体数量产生影响。本研究表明，即便沿相对较短的海拔梯度，海拔仍可对物种丰富度产生显著的直接效应以及通过个体数量介导的间接效应，且效应方向从正到负不等，具体取决于当地的资源可获得性以及类群或营养功能群的特征。若海拔升高对某一类群有益的本地环境属性产生正向影响，则该类群的物种丰富度会随海拔上升而增加。因此，在评估山区全球变化的影响时，应结合本地环境背景，采用多类群研究方法。