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

Climate change is increasing the frequency and severity of short-term (~1 y) drought events—the most common duration of drought—globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function—aboveground net primary production (ANPP)—was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.