Landscape-level patterns of fungal community composition parallel the spatial distribution of upland forest ecosystems

The specificity of some mycorrhizal symbioses, and the distinct metabolic capabilities of fungal saprotrophs suggest that plant communities, and the litter they produce, should be a primary factor structuring landscape-level patterns of fungal community composition.  We investigated the extent to which fungal community composition paralleled the landscape-level distribution of floristically and functionally distinct forest ecosystems in northern Lower Michigan.  We used random clone libraries and molecular fingerprinting (T-RFLP) to examine the similarity of fungal communities in the O and A horizons of three upland forest ecosystems (black oak–white oak (BOWO); sugar maple-red oak (SMRO); sugar maple–basswood (SMBW)).  Replicate stands in each ecosystem type were spatially distributed across 5000 km² area.  Our results showed that most fungal species exhibit patchy/discontinuous distributions at the landscape scale. Nevertheless, the fungal communities of each replicate of a forest ecosystem were more similar to each other than to those of other ecosystems, and community similarity was not significantly related to the distance between sites. Within all ecosystems, the fungal communities of the O and A horizons were markedly different. The presence of maple in the litter had a strong effect on the similarity of O horizon communities; while belowground the presence of oak was important. Overall, our results support the notion that the composition of the plant community plays a strong role in determining the composition of the fungal community, and further show that the factors influencing establishment by saprotrophic or mycorrhizal species may operate independently of each other