Responses of belowground bud banks and their relationships with aboveground vegetation to experimental drought along an aridity gradient in temperate grasslands

1. Climate change is expected to increase the magnitude and frequency of extreme drought in most grassland ecosystems. Exploring the responses of the belowground bud banks and their relationships with aboveground plant parts to drought is of great significance in explaining impacts of climate change on grasslands. However, studies on the response patterns of community-scale bud and shoot densities and their ratios to experimental drought along an aridity gradient are rare. 2. We experimentally removed 66% of growing season precipitation for 4 years in three temperate grasslands that spanned an aridity gradient in northern China, and tracked the legacy effects of drought on community belowground bud density, community aboveground shoot density, and the ratio of bud to shoot density one year following treatment. 3. Belowground bud density was the lowest at the highest aridity site for the entire community, while aboveground shoot density was the highest at the medium aridity site. Belowground bud and aboveground shoot densities were the lowest at the high aridity site for grasses, but the highest for forbs at this site. Bud:shoot ratios decreased with increasing aridity for grasses, yet remained constant for forbs along the aridity gradient. Experimental drought reduced community belowground bud density a year following drought at each site. Experimental drought did not alter belowground bud bank for grasses, but decreased forb bud banks across sites. Experimental drought had little legacy effects on aboveground shoot density and bud:shoot ratios for the entire community or each functional type (grasses and forbs) at each site. 4. We found that grasses and forb bud banks differ in their responses to both multi-year drought and long-term climate patterns, and that community meristem limitation may increase as grasslands get drier. Bud bank responses to climate will likely alter future plant communities and functioning, and incorporating bud bank dynamics may improve projections of grassland ecosystems under future climate changes.