A global meta-analysis on the individual and combined effects of multiple global change factors on plant species richness

Plant species richness (PSR) is of significant importance for terrestrial ecosystem functions, yet the effects of multiple global change factors on PSR are underexplored. We conducted a meta-analysis of 654 observations to examine the individual and combined effects of elevated CO2 (eCO2), warming, altered precipitation, and nitrogen (N) addition on PSR. Results show that eCO2 and increased precipitation stimulated PSR, whereas warming, decreased precipitation, and N addition suppressed it. Antagonistic impacts on PSR were found between N addition and both eCO2 and altered precipitation. However, the combined effects of warming with eCO2, altered precipitation, and N addition were additive. These effects varied with experimental facility, plot and sampling area, and duration as well as ecosystem, climate, and soil texture both in magnitude and direction. Our findings underscore the importance of incorporating experimental settings and site characteristics into regional-scale projections of species richness in response to anthropogenic atmospheric and climatic change.

植物物种丰富度（Plant species richness, PSR）对陆地生态系统功能至关重要，然而当前针对多重全球变化因子对PSR的影响研究仍较为不足。本研究通过对654组观测数据开展元分析（meta-analysis），探究了二氧化碳浓度升高（elevated CO2, eCO2）、增温、降水格局改变以及氮添加（nitrogen addition, N）等单一及复合全球变化因子对PSR的独立与联合效应。研究结果显示，二氧化碳浓度升高与降水增加可提升PSR，而增温、降水减少与氮添加则会抑制PSR。氮添加与二氧化碳浓度升高、降水格局改变对PSR的影响存在拮抗效应；但增温分别与二氧化碳浓度升高、降水格局改变及氮添加组合时，对PSR的效应则表现为加和性。上述效应的强度与方向会随实验设施、样地与采样区域、实验时长，以及生态系统类型、气候条件与土壤质地的差异而发生变化。本研究结果强调，在开展人为驱动的大气与气候变化背景下物种丰富度的区域尺度预测时，应将实验设置与样地特征纳入考量范畴。