Climate change is expected to increase the frequency and severity of droughts and is increasingly affecting also ecosystems, which have so far been rarely exposed to drought events. Next to concurrent effects, droughts can induce lasting legacies on ecosystem structure and functioning and can thereby also alter ecosystem responses to subsequent droughts. In this talk I will highlight some key insights from a recently published review paper on drought legacies (Mueller & Bahn 2022, Global Change Biology) and will provide examples from two long-term drought experiments in the Austrian Alps, suggesting some mechanisms by which recurrent drought can alter drought responses of plant-, soil- and ecosystem processes. These included a.o. adaptive responses of water-use efficiency and of plant and microbial community composition and functioning, which were associated with improved resistance to and recovery from recurrent drought. At the same time, we observed negative effects of recurrent drought on soil aggregate stability and pore size distribution, which led to a reduction in plant-available water. Thus, processes related to adaptation and degradation can simultaneously shape drought legacy responses. I will conclude the talk by outlining some pressing research challenges and possible avenues to advancing our understanding of drought legacies in a rapidly changing climate.
