Microbial communities in soil macro-aggregates with less connected networks respire less across successional and geographical gradients. Microbial communities in soil macro-aggregates

The formation of soil aggregates relates to the stability of soil organic carbon, which distinguishes the living conditions of microbial communities in various micro-niches. Here, we investigated fungal and bacterial community structure, networks, biomass, and respiration in individual micro-niches between and inside soil aggregates using seven different chronosequences (both primary and secondary successions from pioneer stages to well-developed ecosystems) on a European-scale gradient from a maritime climate in Belgium to a more continental climate in Hungary. We showed that geographic area was the most crucial factor in shaping microbial community structures, while soil aggregates were the second most important factor than succession age and vegetation. Moreover, aggregates were the most important factor affecting the biomass of major microbial groups, followed by location and succession age. Interestingly, compared with other aggregate sizes, macro-aggregates had less connected microbial networks and low microbial respiration rates. We, thus, expect that embedding organic particles into the mineral matrix of macro-aggregates represents a key point in microbial community organization as indicated by microbial community network connectedness and microbial respiration. Our findings demonstrate the importance of soil aggregates in microbial community organization and C stabilization in soil.