Scale-dependent influences of distance and vegetation on the composition of aboveground and belowground tropical fungal communities

Fungi provide essential ecosystem services and engage in a variety of symbiotic relationships with trees. In this study, we investigate the spatial relationship of trees and fungi at a community level. We characterized the spatial dynamics for above- and belowground fungi using a series of forest monitoring plots, at nested spatial scales, located in the tropical South Pacific. Fungal communities exhibited strong distance decay of similarity across our entire sampling range (3-110,000 m), and also at small spatial scales (< 50 m). Unexpectedly, this pattern was inverted at an intermediate scale (3.7-26 km). At large scales (80-110 km), belowground and aboveground fungal communities responded inversely to increasing geographic distance. Aboveground fungal community turnover (beta diversity) was best explained, at all scales, by geographic distance. In contrast, belowground fungal community turnover was best explained by geographic distance at small scales, and tree community composition at large scales. We demonstrate scale-dependent spatial dynamics of fungal communities, synchronous spatial dynamics for trees and fungi, and the varying influence of habitat versus geographic distance in structuring Soil, Selaginella sp., and Understory fungal communities.