Data from: Erosion of beta diversity under interacting global change impacts in a semiarid grassland

1. Human impacts are often thought of as homogenizing natural communities, but it is unclear how these impacts interact to alter the beta diversity (spatial variability) of plant communities. 2. In a grassland with high beta diversity along a soil fertility gradient, we asked which combinations of nutrient enrichment, precipitation enhancement, and disturbance would homogenize communities along the gradient by allowing dominant species from one part of the gradient to increase their abundances in other parts of the gradient. In particular, joint addition of nutrients and water might especially benefit resource acquisitive and/or exotic species, which have been observed to compete well in resource-rich conditions; this would tend to reduce variation in species composition across the gradient. To alleviate dispersal limitation as a constraint on treatment responses, we added seeds of 15 species abundant in different parts of the soil fertility gradient to our 132 plots. 3. Fertilization and water addition allowed species from fertile soils to increase their abundance in infertile soils, an effect that strengthened with time. Disturbance permitted species from infertile soils to increase in abundance in infertile soils, but only transiently. Plant height, specific leaf area, and exotic status best predicted the abilities of species to attain greater cover in harsh habitats under ameliorated conditions. Among-habitat beta diversity of seeded species was reduced by the interactive effect of fertilization and watering, although not by watering alone. 4. Synthesis. Our findings are a novel demonstration of how interacting global change factors reduce beta diversity by eroding the biotic and abiotic resistances that control community structure along soil fertility gradients.1. 人类活动通常被认为会使自然群落趋于同质化，但目前尚不明确这类活动如何相互作用，进而改变植物群落的β多样性（beta diversity，即空间变异性）。 2. 本研究以一条沿土壤肥力梯度、具有较高β多样性的草原群落为研究对象，旨在探究养分富集、降水增强与干扰的哪些组合方式，可通过使梯度某一区域的优势种在其他区域的丰度提升，实现沿该梯度的群落同质化。具体而言，养分与水分的联合添加或许会格外有利于资源获取型物种和/或外来物种——这类物种已被证实能在资源丰富的生境中具备较强竞争能力；该效应将倾向于降低梯度间物种组成的差异。为缓解扩散限制对处理响应的制约，我们向132个样地中添加了15个在土壤肥力梯度不同区域广泛分布的物种的种子。 3. 施肥与水分添加使得源自肥沃土壤的物种在贫瘠土壤中的丰度提升，且该效应随时间推移不断增强。干扰仅能短暂地让源自贫瘠土壤的物种在贫瘠生境中丰度上升。植物高度、比叶面积（specific leaf area）以及是否为外来物种，能够最佳预测物种在生境改善条件下，在严苛生境中获得更高盖度的能力。尽管单独施加水分未产生该效果，但施肥与浇水的交互作用降低了播撒物种的生境间β多样性。 4. 研究总结。本研究首次证实了全球变化因子的交互作用，可通过削弱沿土壤肥力梯度调控群落结构的生物与非生物抗性，进而降低β多样性。