Exploring how groundwater buffers the influence of heatwaves on vegetation function during multi-year droughts
2021
Abstract. The co-occurrence of droughts and heatwaves can have
significant impacts on many socioeconomic and environmental systems.
Groundwater has the potential to moderate the impact of droughts and
heatwaves by moistening the soil and enabling vegetation to maintain higher
evaporation, thereby cooling the canopy. We use the Community Atmosphere
Biosphere Land Exchange (CABLE) land surface model, coupled to a groundwater
scheme, to examine how groundwater influences ecosystems under conditions of
co-occurring droughts and heatwaves. We focus specifically on south-east
Australia for the period 2000–2019, when two significant droughts and
multiple extreme heatwave events occurred. We found groundwater plays an
important role in helping vegetation maintain transpiration, particularly in
the first 1–2 years of a multi-year drought. Groundwater impedes
gravity-driven drainage and moistens the root zone via capillary rise. These
mechanisms reduced forest canopy temperatures by up to 5 ∘ C during
individual heatwaves, particularly where the water table depth is shallow.
The role of groundwater diminishes as the drought lengthens beyond 2 years
and soil water reserves are depleted. Further, the lack of deep roots or
stomatal closure caused by high vapour pressure deficit or high temperatures
can reduce the additional transpiration induced by groundwater. The capacity
of groundwater to moderate both water and heat stress on ecosystems during
simultaneous droughts and heatwaves is not represented in most global
climate models, suggesting that model projections may overestimate the risk of
these events in the future.
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
122
References
0
Citations
NaN
KQI