Bottom -up effects of roots on belowground fungal communities in tropical land-use systems

The conversion of highly diverse tropical lowland rainforests to monocultures of oil palm and rubber leads to drastic changes in fungal community structures. The magnitude of structuring effects, driven by changes in root or soil properties, on trophic groups with different ecological functions (mycorrhiza, saprotrophs, and pathogens) remains unknown. Here, we investigated shifts in the composition of different ecological groups of soil- and root-inhabiting fungi in response to changes in the soil and root chemistry of different land-use systems. We found an unexpectedly high turnover and low nestedness between local root and soil communities. In addition to soil pH, the root chemistry, especially root C/N, had strong bottom-up regulatory effects on the root-associated fungal assemblages, while root vitality had strong effects on the soil-residing fungi. Changes in root and soil chemistry drove divergent responses in different functional groups and had a stronger impact on fungal community structures than geographic distance. Our results suggest that changes in root chemistry promote the assemblage of specific root-associated fungal communities, largely independent of the surrounding soil community. Consequently, the recovery of root traits in intense land-use systems may stabilize the fungal communities against abiotic changes.