Many experiments have shown that biodiversity enhances ecosystem functioning. However, we have little understanding of how environmental heterogeneity shapes the effect of diversity on ecosystem functioning and to what extent this diversity effect is mediated by variation in species richness or species turnover. This knowledge is crucial to scaling up the results of experiments from local to regional scales. Here we quantify the diversity effect and its components—that is, the contributions of variation in species richness and species turnover—for 22 ecosystem functions of microorganisms, plants and animals across 13 major ecosystem types on Mt Kilimanjaro, Tanzania. Environmental heterogeneity across ecosystem types on average increased the diversity effect from explaining 49% to 72% of the variation in ecosystem functions. In contrast to our expectation, the diversity effect was more strongly mediated by variation in species richness than by species turnover. Our findings reveal that environmental heterogeneity strengthens the relationship between biodiversity and ecosystem functioning and that species richness is a stronger driver of ecosystem functioning than species turnover. Based on a broad range of taxa and ecosystem functions in a non-experimental system, these results are in line with predictions from biodiversity experiments and emphasize that conserving biodiversity is essential for maintaining ecosystem functioning.

许多实验表明，生物多样性增强了生态系统的功能。然而，我们对环境异质性如何影响多样性对生态系统功能的影响以及这种多样性影响在多大程度上是由物种丰富度或物种周转率的变化所介导的了解甚少。这些知识对于将实验结果从地方扩大到区域规模至关重要。在这里，我们量化了坦桑尼亚乞力马扎罗山 13 种主要生态系统类型中微生物、植物和动物的 22 种生态系统功能的多样性效应及其组成部分——即物种丰富度和物种周转变化的贡献。生态系统类型的环境异质性平均增加了多样性效应，从解释生态系统功能变化的 49% 到 72%。与我们的预期相反，物种丰富度的变化比物种周转更强烈地介导了多样性效应。我们的研究结果表明，环境异质性加强了生物多样性和生态系统功能之间的关系，并且物种丰富度比物种更替是生态系统功能更强大的驱动力。基于非实验系统中广泛的分类群和生态系统功能，这些结果与生物多样性实验的预测一致，并强调保护生物多样性对于维持生态系统功能至关重要。我们的研究结果表明，环境异质性加强了生物多样性和生态系统功能之间的关系，并且物种丰富度比物种更替是生态系统功能更强大的驱动力。基于非实验系统中广泛的分类群和生态系统功能，这些结果与生物多样性实验的预测一致，并强调保护生物多样性对于维持生态系统功能至关重要。我们的研究结果表明，环境异质性加强了生物多样性和生态系统功能之间的关系，并且物种丰富度比物种更替是生态系统功能更强大的驱动力。基于非实验系统中广泛的分类群和生态系统功能，这些结果与生物多样性实验的预测一致，并强调保护生物多样性对于维持生态系统功能至关重要。