Legacy Effects of Extreme Drought on the Belowground Bud Bank of Bunchgrass and Rhizomatous Steppe Communities in Inner Mongolia

Belowground bud banks play a crucial role in plant population regeneration, community dynamics and ecosystem functions in response to environmental change and disturbance. In mesic grasslands, belowground bud banks are largely resistant to short-term drought. The sensitivity of belowground bud banks to long-term extreme drought in semiarid steppes is less understood. Here, we investigated the legacy effects of a 4-year experimental drought (i.e., 66% reduction in growing season precipitation) on belowground bud density, aboveground shoot density and their relationship (represented by the meristem limitation index-MLI) in two temperate semiarid steppes with different dominated plant growth forms (i.e., bunchgrass vs. rhizomatous grass). Measurements were made during the first recovery year following drought; thus, we reported the legacy effects of drought on belowground bud bank. Results showed that at community level the densities of both belowground buds and aboveground shoots decreased while there was no change in MLI. However, drought had no significant influences on belowground buds, aboveground shoots and MLI of the dominant plant growth form. The legacy effects of drought were largely dependent on plant community type and growth form. Specifically, due to their cluster/phalanx clonal growth, bunchgrasses and communities they dominated were characterized by greater meristem limitation compared with rhizomatous grasses. Our study implies that integrating belowground bud bank demography into the predictive model of community dynamics and ecosystem functions in response to climate change should be considered to understand the differing responses among community type and dominant plant groups.