Integrating soil biological properties at the landscape and microsite level into sagebrush steppe restoration efforts across the Great Basin

Non-native invasive plants affect not only the aboveground vegetative components of ecosystems, but also soil surface, microbial, and invertebrate communities. Bromus tectorum (cheatgrass) invasion into sagebrush steppe ecosystems has brought about a number of biologically significant changes in surface and belowground communities that may have consequences for restoration efforts in the Great Basin. Biological soil crusts, which are integral parts of healthy sagebrush systems, have been destroyed in many areas and replaced by thick layers of B. tectorum thatch or bare ground. Soil microbial communities have shifted from fungal-dominated under sagebrush to bacterial-dominated under cheatgrass, with concomitant changes in soil nematode community structure. In light of these findings, we characterized soil community composition at both the landscape and microsite level in conjunction with sagebrush steppe restoration experiments taking place in Oregon, Idaho, Nevada, and Utah. Soil microbial and nematode composition were strongly patterned by site differences, and those differences could be best explained by soil pH and surface cover type. Sugar applications (a management technique intended to immobilize soil nutrients and decrease cheatgrass biomass) had the effect of increasing nematode and PLFA fungal biomarker abundance at all sites. As a restoration tool, applying sugar may have the added benefit of helping to re-establish the fungal component of the soil ecosystem. Our findings suggest that soil communities can be used to identify “gradients of degradation” among cheatgrass-invaded sites, and we propose using soil biological, chemical, and physical properties as indicators of areas that may benefit from restoration efforts.