Diversity and nitrogen addition have positive relationships with plant productivity, yet climate-induced changes in water availability threaten to upend these established relationships. Using long-term data from three experiments in a mesic grassland (ranging from 17 to 34 yr of data), we tested how the effects of species richness and nitrogen addition on community-level plant productivity changed as a function of annual fluctuations in water availability using growing season precipitation and the Standardized Precipitation-Evapotranspiration Index (SPEI). While results varied across experiments, our findings demonstrate that water availability can magnify the positive effects of both biodiversity and nitrogen addition on productivity. These results suggest that productivity responses to anthropogenic species diversity loss and increasing nitrogen deposition could depend on precipitation regimes, highlighting the importance of testing interactions between multiple global change drivers.

中文翻译：

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在长期草地实验中，水资源可用性改变了对生物多样性和氮的生产力反应

多样性和氮添加与植物生产力具有正相关关系，但气候引起的水资源可用性变化有可能颠覆这些既定的关系。使用来自中等草原的三个实验的长期数据（从 17 年到 34 年的数据），我们测试了物种丰富度和氮添加对群落水平植物生产力的影响如何随着水资源可用性的年度波动而变化使用生长季降水和标准化降水蒸散指数 (SPEI)。虽然结果因实验而异，但我们的研究结果表明，水资源的可用性可以放大生物多样性和氮添加对生产力的积极影响。