Soil fungal community dynamics under elevated and depleted nutrient conditions in sagebrush steppe and cheatgrass-invaded ecosystems

Background/Question/Methods Non-native invasive plants affect not only aboveground vegetative components of ecosystems, but also soil microbial and invertebrate communities. In the northern Great Basin, Bromus tectorum (cheatgrass) invasion into sagebrush steppe ecosystems has brought about a number of biologically significant changes in microbial communities that may have consequences for restoration of these systems. We examined soil fungal communities associated with sagebrush, native perennial bunchgrasses, cheatgrass, and bare interspace areas that had been unamended and amended with sucrose or ammonium-nitrate. Application of sucrose is a restoration tool used to stimulate microbial nitrogen immobilization, thereby reducing nitrogen availability to plants and limiting plant growth. Soil fungi were examined using terminal restriction fragment length polymorphism (T-RFLP), in which individual restriction fragments (RFs) can be roughly likened to distinct fungal species. Results/Conclusions Preliminary analyses with nonmetric multidimensional scaling (NMS) and multi-response permutation procedures (MRPP) revealed that fungal communities differed under each cover type (A = 0.11, p < 0.0001). The greatest percentage of rare fungal species (i.e. RFs found in 3 or fewer samples) was found in sagebrush rhizosphere soils (35.3%), while cheatgrass rhizosphere soils had the lowest percentage of rare species (15.1%). Indicator species analysis identified two fungal RFs that could be used as indicators for sagebrush samples, nine RFs for bunchgrass samples, two RFs for cheatgrass samples, and six RFs for interspace samples (Indicator Value > 50, p < 0.05). Soils treated with sucrose had a lower percentage of rare species compared to unamended plots (27.1% and 39.9%, respectively). Our preliminary results indicate that cheatgrass invasion into the sagebrush steppe is accompanied by significant changes in soil fungal community composition and decreased fungal species richness. These data also suggest that the addition of sucrose to cheatgrass-invaded areas may promote the proliferation of a few dominant soil fungal species and contribute to a reduction in fungal diversity.