Soil seedbank analysis under experimental drought and delayed monsoon treatments in blue grama and black grama grassland at Sevilleta

This study investigated the question, "Does climate change affect vegetation and seed bank composition in desert grasslands?" The work was done in the Sevilleta National Wildlife Refuge, New Mexico, USA, in in the Extreme Drought in Grassland Experiment (EDGE). Vegetation and seed bank species composition were recorded in black grama (Bouteloua eriopoda) and blue grama (B. gracilis) grasslands at Sevilleta. At each site, two rainfall manipulations and ambient controls were established in 2013 (n=10). Treatments included extreme drought (-66% rainfall reduction) and delayed monsoon (precipitation captured during July-August and reapplied during September-October). Aboveground species composition was assessed and composite soil samples were collected in 2017, five years after the experiment started. Seed bank composition was evaluated using the seedling emergence method. Rainfall treatments increased aboveground species richness at both sites, and seed bank richness only in the blue grama community. Vegetation cover was reduced by both rainfall manipulations, but seed bank density increased or remained the same compared with controls. In aboveground vegetation, cover of annual and perennial forbs increased, and dominant perennial grasses decreased. In the soil seed bank, species composition was similar among all treatments and was dominated by annual and perennial forbs. The seed bank was more resistant to drought than aboveground vegetation. Because seed banks enhance long-term community stability, their drought resistance plays an important role in maintaining ecosystem processes during and following drought in these grassland communities.