Partial mutual exclusion of ectomycorrhizal and saprobic fungi in a tropical seasonal rainforest

Abstract

Spatial distributions of ectomycorrhizal and saprotrophic fungi may differ in tropical forests for several reasons. If they do, it could have profound implications for carbon cycling across landscapes. We examined distributions of ectomycorrhizal and saprotrophic fungi in a 20 hectare forest study plot in China by collecting and identifying sporocarps (mushrooms) over two years. We found that for sporocarp numbers, species, and contributions to Shannon diversity, saprotrophic fungi were highest near stream channels and decreased with distance therefrom. Ectomycorrhizal species numbers and contributions to Shannon diversity were highest in plots most distant from stream channels. Earlier research here showed soil phosphorus availability to decrease away from stream channels, and ectomycorrhizal fungi should be favored where soil phosphorus is low. Aggressive negative interactions between these fungal guilds should intensify this pattern. We suggest that litter decomposition rates here should be highest near stream channels, because of strong domination by saprotrophic fungi.