Rare microbial communities drive ecosystem multifunctionality in acidic soils of southern China

Soil microbial communities are important for maintaining ecosystem multifunctionality, and abundant and rare sub-communities often have fundamentally different characteristics and ecological roles. However, little is known about the links between microbial sub-communities and soil multifunctionality in acidic soils across large spatial scales. Here, we collected 52 soil samples from four locations spanning 961.3 km in the acidic soil region of southern China and characterized bacterial and fungal sub-communities and their contributions to soil multifunctionality. Sub-community compositions of both rare bacteria and rare fungi significantly explained changes in soil multifunctionality, but abundant sub-communities were not significantly related to soil multifunctionality. This suggested that soil multifunctionality might be mainly controlled by rare microbes in acidic soils. Rare fungal alpha-diversity, rather than rare bacterial alpha-diversity, was significantly and positively correlated with multifunctionality. Deterministic processes were the primary drivers of the sub-community assembly of rare bacteria and rare fungi and thus might have an important effect on soil multifunctionality. Soil pH was the most dominant soil factor driving rare bacterial and fungal sub-community structures and affecting soil multifunctionality. In the co-occurrence networks of bacterial and fungal communities, most of the keystone taxa were rare species. The numbers of positive interactions of rare fungal taxa, but not rare bacterial taxa, were positively related to soil multifunctionality. Our results provided evidence that rare microbial sub-communities are important for maintaining ecosystem multifunctionality in acidic soils, and rare bacteria and fungi may display the potentially different mechanisms to drive ecosystem functions.