Drought legacies weaken resistance and plant‐mycorrhizal associations but not recovery

Drought legacies can shape how grasslands respond to increasingly frequent climate extremes, yet their influence on future resistance and recovery remains unclear, particularly in mesic grasslands, where productivity is strongly linked to precipitation availability.

Using a long‐term field experiment, we tested how zero, one or two prior experimentally imposed extreme droughts influenced grassland resistance to a subsequent 4‐year extreme drought (2018–2021) and recovery after drought in 2022. We quantified above‐ground net primary productivity and species composition, as well as plant functional traits and arbuscular mycorrhizal (AM) fungal colonization of the dominant grasses at the site, to evaluate above‐ and below‐ground legacy effects.

Differences in productivity resistance among drought‐legacy treatments were small during the first three drought years and became evident only in the final, most severe drought year, when resistance was lowest in plots exposed to two prior droughts. However, above‐ground productivity recovered to similar levels across all treatments in 2022, demonstrating substantial short‐term recovery despite contrasting drought histories. The dominant grass, Andropogon gerardii , exhibited higher specific leaf area and greater leaf production during the recovery year, indicating increased investment in rapid resource capture and regrowth. Additionally, AM fungal colonization of A. gerardii declined with repeated drought exposure and remained lowest in plots exposed to two prior droughts even after above‐ground productivity recovered. In contrast to these traits and below‐ground changes, species composition, including richness, evenness, turnover and absolute cover, remained stable across all treatments and years.

Synthesis: Repeated drought reduced resistance under the most severe drought conditions, yet this mesic grassland recovered rapidly once drought ended. At the same time, AM fungal colonization of the dominant grass remained reduced, revealing a mismatch between above‐ground recovery and below‐ground legacies and showing that different ecosystem components can recover at different rates.