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

Abstract

As climate changes, many regions of the world are projected to experience more intense droughts, which can drive changes in plant community composition through a variety of mechanisms. During drought, community composition 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 of mechanisms and plantplant interactions that may lead to community changes during and after a drought. The CRED framework applies some principles of the stress gradient hypothesis (SGH), which proposes that the balance between competition and facilitation changes with increasing stress. The CRED framework suggests that net biotic interactions (NBI), the relative frequency and intensity of facilitative (+) and competitive (À) interactions between plants, will change temporally, becoming more positive under increasing drought stress and more negative as drought stress decreases. Furthermore, we suggest that rewetting rates affect the rate of resource amelioration, specifically water and nitrogen, altering productivity responses and the intensity and importance of NBI, all of which will 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.

Deciphering the stability of grassland productivity in response to rainfall manipulation experiments

“…Besides the drought characteristics and prevailing climatic conditions, the differential stability across grasslands might also be related to edaphic and/or intrinsic biological differences (Ploughe et al, ). Considerable evidence from both meta‐analyses (Craven et al, ; Ruppert et al, ) and several individual studies suggests that different aspects of biodiversity [species diversity (Kreyling, Dengler, et al, ; Pfisterer & Schmid, ; Vogel et al, ; Wagg et al, ), functional diversity (grass, legumes and forbs) (Byrne, Adler, & Lauenroth, ; Hofer et al, ; Stampfli, Bloor, Fischer, & Zeiter, ), and plant life‐history traits (annual versus perennial) (Hoeppner & Dukes, ; Wang et al, )] can significantly influence the ecosystem stability of grasslands in response to drought.…”

Global change stressors alter resources and shift plant interactions from facilitation to competition over time

“…Plant interactions, including competition and facilitation, are complex phenomena that are becoming increasingly unpredictable under global change (Brooker 2006, Ploughe et al 2019. Competitive outcomes depend on the type of limiting resource, identity of competitors, and seasonal context within which plants interact (Maestre et al 2003, Espigares et al 2004, Farrior et al 2013, Wright et al 2015.…”

Introduced goats reduce diversity and biomass of herbs in Caatinga dry forest

“…On the other hand, rare species ( 0 D) of the Caatinga are more associated with grazed areas that are expected to accumulate more species in total, probably because differential herbivory pressure by goats may disproportionally reduce dominant species through herbivores (Koerner et al, 2018). Yet, the rainiest periods of our study harbored the lowest diversity of both common and dominant species ( 1 D and 2 D, respectively), which can be explained by the increased relative frequency of negative inter-specific interactions among plants during wet periods (Ploughe et al, 2019). In brief, the structure of the herbaceous communities of the Caatinga rangelands is driven by environmental factors on top of which we must sum up the presence of goats whose effects are also complex but predictable.…”