Positive biodiversity–ecosystem functioning relationships have been widely reported, predominately from grassland ecosystems. However, this does not necessarily have to apply accordingly in more complex situations such as in forests across different vertical strata. For instance, overstorey tree species richness has been shown to be associated with a lower understorey productivity. Whether or not tree species richness effects add to understorey productivity by increasing (i.e. due to habitat heterogeneity) or reducing resource availability (i.e. through increasing competition) and whether understorey productivity is indeed being governed more strongly by tree species identity are likely to change over time. Moreover, studies also suggested that richness–productivity relationships change with the environmental context. Using an experimental forest plantation with manipulated tree species richness, this study examined these temporal and environmental dynamics across strata.

中文翻译：

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下层生物量的驱动因素：在年轻的森林中，树种身份比丰富性更重要

广泛报道了积极的生物多样性与生态系统功能的关系，其中主要是草原生态系统。但是，这不必一定适用于更复杂的情况，例如在不同垂直地层的森林中。例如，已经表明，过高的树木物种丰富度与较低的低层生产力相关。树种丰富度的影响是否通过增加（即由于栖息地异质性）或减少资源可利用性（即通过增加竞争）而增加了林下生产力，以及林下物种生产力的确确实受到树种身份的强烈控制可能会随着时间而改变。此外，研究还表明，丰富度与生产率之间的关系随着环境的变化而变化。