Drought mildly reduces plant dominance in a temperate prairie ecosystem across years

1. Shifts in dominance and species reordering can occur in response to global change. However, it is not clear how altered precipitation and disturbance regimes interact to affect species composition and dominance.

2. We explored community-level diversity and compositional similarity responses, both across and within years, to a manipulated precipitation gradient and annual clipping in a mixed-grass prairie in Oklahoma, USA. We imposed seven precipitation treatments (five water exclusion levels [-20%, -40%, -60%, -80%, and -100%], water addition [+50%], and control [0% change in precipitation]) year-round from 2016-2018 using fixed interception shelters. These treatments were crossed with annual clipping to mimic hay harvest.

3. We found that community-level responses were influenced by precipitation across time. For instance, plant evenness was enhanced by extreme drought treatments, while plant richness was marginally promoted under increased precipitation.

4. Clipping promot...