Exploring how groundwater buffers the influence of heatwaves on vegetation function during multi-year droughts

Abstract. The co-occurrence of droughts and heatwaves can have significant impacts on many socioeconomic environmental systems. Groundwater has the potential to moderate impact by moistening soil enabling vegetation maintain higher evaporation, thereby cooling canopy. We use Community Atmosphere Biosphere Land Exchange (CABLE) land surface model, coupled a groundwater scheme, examine how influences ecosystems under conditions co-occurring heatwaves. focus specifically south-east Australia for period 2000–2019, when two multiple extreme heatwave events occurred. found plays an important role in helping transpiration, particularly first 1–2 years multi-year drought. impedes gravity-driven drainage moistens root zone via capillary rise. These mechanisms reduced forest canopy temperatures up 5 ?C during individual heatwaves, where water table depth is shallow. diminishes as drought lengthens beyond 2 reserves are depleted. Further, lack deep roots or stomatal closure caused high vapour pressure deficit reduce additional transpiration induced groundwater. capacity both heat stress simultaneous not represented most global climate models, suggesting that model projections may overestimate risk these future.