Impact of lime, nitrogen and plant species on fungal community structure in grassland microcosms.

A microcosm-based approach was used to study impacts of plant and chemical factors on the fungal community structure of an upland acidic grassland soil. Seven plant species typical of both unimproved and fertilized grasslands were either left unamended or treated with lime, nitrogen or lime plus nitrogen. Fungal community structure was assessed by a molecular approach, fungal automated ribosomal intergenic spacer analysis (FARISA), while fungal biomass was estimated by measuring soil ergosterol content. Addition of nitrogen (with or without lime) had the largest effect, decreasing soil pH, fungal biomass and fungal ribotype number, but there was little corresponding change in fungal community structure. Although different plant species were associated with some changes in fungal biomass, this did not result in significant differences in fungal community structure between plant species. Addition of lime alone caused no changes in fungal biomass, ribotype number or community structure. Overall, fungal community structure appeared to be more significantly affected through interactions between plant species and chemical treatments, as opposed to being directly affected by changes in individual improvement factors. These results were in contrast to those found for the bacterial communities of the same soils, which changed substantially in response to chemical (lime and nitrogen) additions.