Trends in alpha diversity, community composition, and network complexity of rare, intermediate, and abundant bacterial taxa along a latitudinal gradient and their impact on ecosystem multifunctionality

Soil microbial communities are key factors in maintaining ecosystem multifunctionality (EMF). However, the distribution patterns of bacterial diversity and how the different bacterial taxa and their diversity dimensions affect EMF remain largely unknown. Here, we investigated variation in three measures of diversity (alpha diversity, community composition and network complexity) among rare, intermediate, and abundant taxa across a latitudinal gradient spanning five forest plots in Yunnan Province, China and examined their contributions on EMF. We aimed to characterize the diversity distributions of bacterial groups across latitudes and to assess the differences in the mechanisms underlying their contributions to EMF. We found that multifaceted diversity (i.e., diversity assessed by the three different metrics) of rare, intermediate, and abundant bacteria generally decreased with increasing latitude. More importantly, we found that rare bacterial taxa tended to be more diverse, but they contributed less to EMF than intermediate or abundant bacteria. Among the three dimensions of diversity we assessed, only community composition significantly affected EMF across all locations, while alpha diversity had a negative effect, and network complexity showed no significant impact. Our study further emphasizes the importance of intermediate and abundant bacterial taxa as well as community composition to EMF and provides a theoretical basis for investigating the mechanisms by which belowground microorganisms drive EMF along a latitudinal gradient.