Locally, plant species richness supports many ecosystem functions. Yet, the mechanisms driving these often-positive biodiversity-ecosystem functioning relationships are not well understood. Spatial resource partitioning across vertical resource gradients is one of the main hypothesized causes for enhanced ecosystem functioning in more biodiverse grasslands. Spatial resource partitioning occurs if species differ in where they acquire resources and can happen both above- and belowground. However, studies investigating spatial resource partitioning in grasslands provide inconsistent evidence. We present the results of a meta-analysis of 21 data sets from experimental species-richness gradients in grasslands. We test the hypothesis that increasing spatial resource partitioning along vertical resource gradients enhances ecosystem functioning in diverse grassland plant communities above- and belowground. To test this hypothesis, we asked three questions: 1. Does species richness enhance biomass production or community resource uptake across sites? 2. Is there evidence of spatial resource partitioning as indicated by resource tracer uptake and biomass allocation above- and belowground? 3. Is evidence of spatial resource partitioning correlated with increased biomass production or community resource uptake? Although plant species richness enhanced community nitrogen and potassium uptake and biomass production above- and belowground, we found that plant communities did not meet our criteria for spatial resource partitioning, though they did invest in significantly more aboveground biomass in higher canopy layers in mixture relative to monoculture. Furthermore, the extent of spatial resource partitioning across studies was not positively correlated with either biomass production or community resource uptake. Our results suggest that spatial resource partitioning across vertical resource gradients alone does not offer a general explanation for enhanced ecosystem functioning in more diverse temperate grasslands.

中文翻译：

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温带草原生物多样性实验中空间资源划分的证据有限

在当地，植物物种丰富度支持许多生态系统功能。然而，驱动这些通常是积极的生物多样性-生态系统功能关系的机制尚不清楚。跨垂直资源梯度的空间资源分配是生物多样性更丰富的草原生态系统功能增强的主要假设原因之一。如果物种在获取资源的地点不同并且可以在地上和地下发生，就会发生空间资源划分。然而，调查草原空间资源划分的研究提供了不一致的证据。我们展示了来自草原实验物种丰富度梯度的 21 个数据集的元分析结果。我们检验了这样一个假设，即增加沿垂直资源梯度的空间资源分配可以增强地上和地下不同草地植物群落的生态系统功能。为了验证这一假设，我们提出了三个问题： 1. 物种丰富度是否会提高跨地点的生物量生产或群落资源吸收？2. 是否有空间资源划分的证据，如资源示踪剂吸收和地上和地下生物量分配所示？3. 空间资源划分的证据是否与增加的生物量生产或社区资源吸收相关？虽然植物物种丰富度提高了地上和地下的群落氮和钾的吸收和生物量生产，但我们发现植物群落不符合我们的空间资源划分标准，尽管与单一栽培相比，他们确实在混合种植的较高冠层中投资了显着更多的地上生物量。此外，跨研究的空间资源分配程度与生物量生产或社区资源吸收均不呈正相关。我们的结果表明，单独跨垂直资源梯度的空间资源划分并不能为更多样化的温带草原中增强的生态系统功能提供一般解释。