Community Response to Extreme Drought (CRED): a framework for drought-induced shifts in plant–plant interactions

As climate changes, many regions of the world are projected to experiencemore intense droughts, which can drive changes in plant community composition through a variety ofmechanisms.During drought, communitycomposition can respond directly to resource limitation, but biotic interactions modify the availability of these resources. Here, we develop the Community Response to Extreme Drought framework (CRED),which organizes the temporal progression ofmechanisms and plant– plant interactions that may lead to community changes during and after a drought. The CRED framework applies someprinciples of the stress gradient hypothesis (SGH), which proposes that the balance between competition and facilitation changeswith increasing stress. TheCRED framework suggests that net biotic interactions (NBI), the relative frequency and intensity of facilitative (+) and competitive (−) interactionsbetweenplants,will changetemporally,becomingmorepositiveunder increasing drought stress andmore negative as drought stress decreases. Furthermore,we suggest that rewettingrates affect the rate of resource amelioration, specifically water andnitrogen, altering productivity responses and the intensity and importance ofNBI, all of whichwill influence droughtinduced compositional changes. System-specific variables and the intensity of drought influence the strength of these interactions, and ultimately the system’s resistance and resilience to drought.