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{"Abstract":["Interactions between plants and soil microbes influence plant\n nutrient transformations, including nitrogen (N) fixation, nutrient\n mineralization, and resource exchanges through fungal networks.\n Physical disturbances to soils can disrupt soil microbes and\n associated processes that support plant and microbial productivity.\n In low resource drylands, biological soil crusts\n ("biocrusts") occupy surface soils and house key\n autotrophic and diazotrophic bacteria, non-vascular plants, or\n lichens. Interactions among biocrusts, plants, and fungal networks\n between them are hypothesized to drive carbon and nutrient dynamics;\n however, comparisons across ecosystems are needed to generalize how\n soil disturbances alter microbial communities and their\n contributions to N pools and transformations. To evaluate linkages\n among plants, fungi, and biocrusts, we disturbed all unvegetated\n surfaces with human foot trampling twice yearly in dry conditions\n from 2013-2018 in cyanobacteria-dominated biocrusts in Chihuahuan\n Desert grassland and shrubland ecosystems. Our study included\n microbial communities and N pools sampled at different time points\n in the disturbance treatments at one or both sites. We began our\n sampling after observations in April 2018 that the chlorophyll a\n content was at least double in control than disturbed plots in both\n ecosystems (Chung et al. 2019). Stomping occurred in May, and we\n collected soil and plant samples in June 2018 for N pools and soil\n and root fungal abundance. We collected additional soil samples in\n September 2018 and conducted the 15N tracer experiment to observe\n rates of N transfer from biocrust to plants before the fall stomp\n treatment in October. We collected chlorophyll a samples and soils\n for sequencing bacteria in September of 2019, also before the fall\n stomp treatment."]}