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.