Seasonal dependence of deterministic versus stochastic processes influencing soil fungal community composition in a lowland Amazonian rain forest

The contribution of deterministic versus stochastic processes to the spatio-temporal assembly of soil microbial communities in tropical forests requires quantification so that responses to climate change may be accurately projected. Here we report the spatio-temporal composition of soil fungal communities in a topographically homogeneous forest area in central Amazonia. Soil fungal communities have a greater turnover in space than over time. Stochastic processes are inferred to dominate in the rainy season and deterministic processes in the dry season. Our study highlights the importance of spatial heterogeneity in the absence of environmental gradients and its relationship with seasonal patterns that modulate spatial heterogeneity and contribute to environmental determinism versus stochasticity for fungal community assembly. This baseline may serve to assess deviations in community patterns caused by changes in biotic interactions with above-ground vegetation, such as those resulting from shifts in taxonomical/functional composition of trees driven by climate change. In an Amazonian lowland rainforest, spatial distance exerts a stronger influence on soil fungal community assembly than seasonal patterns linked to precipitation regime, according to repeat observations made along a transect during different seasons in a central Amazonian tropical rainforest.