Drought intensity shapes soil legacy effects on grassland plant and soil microbial communities and their responses to future drought (prokaryote sequences)

Drought can have long-lasting legacy effects on terrestrial ecosystems via persistent shifts in soil microbial community structure and function. Yet, the role drought intensity plays in the formation of soil-mediated drought legacies, and in determining plant and microbial responses to subsequent droughts, is unknown. Here, we evaluate how soil-mediated drought legacies shaped by the intensity of an initial drought event influence plant and microbial communities in the following year, and their response to a subsequent experimental drought. In an outdoor mesocosm experiment, we determined the soil legacy effects of increasing drought intensity in the previous year (i.e., 2020) on grassland plant and soil microbial (prokaryote and fungal) communities and their responses to a drought in the subsequent year (i.e., 2021). Using two model grassland plant communities with contrasting strategies, we investigated whether plant resource acquisition strategy (fast-strategy versus slow-strategy) modulate the soil legacy effects of increasing drought intensity. We hypothesized that: (1) increasing drought intensity leaves increasingly pronounced soil legacy effects on the composition and function of the soil prokaryote and fungal community in the subsequent year; (2) increasing drought intensity leaves more pronounced soil legacy effects in fast resource strategy, compared to slow resource strategy plant communities; and (3) soil legacies of increasing drought intensity will decrease microbial and plant community resistance to and recovery from a subsequent drought. We found that the intensity of the initial (i.e., past) drought shaped the composition, network structure, and functioning of soil microbial communities, with stronger effects on prokaryotes than fungi. Moreover, drought intensity determined soil-mediated legacy effects on plant response to a subsequent drought: increasing past drought intensity decreased drought resistance of the slow-strategy plant community and reduced productivity overshoot in the fast-strategy community after re-wetting. Our findings demonstrate that increasing drought intensity can lead to distinct legacies in soil microbial community composition and function with impacts on plant responses to future droughts. This dataset presents the prokaryote (16S) sequences. A sister dataset (Bio project number xxxx) presents the fungal (ITS2) sequences.