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.