Niche width of above‐ and belowground organisms varied in predicting biodiversity profiling along a latitudinal gradient

Biodiversity is the foundation of all ecosystems across the planet, and better understanding of its global distribution mechanism could be important for biodiversity conservation under global change world. A niche width model, combined with metabolic theory, has successfully predicted the increase of a-diversity and decrease of b-diversity in the belowground microbial community along an altitudinal mountain gradient. In this study, we evaluated this niche width model of aboveground plants (mainly trees and shrubs) and belowground bulk soil microbial communities (i.e. bacteria and archaea) along a latitudinal gradient of forests in China. The niche widths of plants and microbes both increased by increasing temperature and precipitation, and by nearness to circumneutral pH. However, the a- and b-diversities (observed richness and Bray-Curtis dissimilarity, respectively) could not be accurately predicted by a single niche width model alone, either temperature, precipitation, or pH. Considering the interactions among different niche width models, all three niche width models were combined together to predict biodiversity at the community level using structure equation modelling (SEM). The results showed that the niche width model of circumneutral pH was most important in predicting diversity profiling (i.e. a- and b-diversity) for both plants and microbes, while niche width of precipitation and temperature showed both direct and indirect importance for microbe and plant biodiversity, respectively. Since current niche width model neglects several scenarios related to taxon and environmental attributes, it still needs to be treated with caution in predicting biodiversity trends.