Abstract ID: 3.10785 | Accepted as Talk | Talk/Oral | TBA | TBA

Australia’s relatively low elevation alpine and subalpine ecosystems are increasingly threatened by climate change factors, particularly warming and drying. The capacity for plants to respond to both heat and drought stress through phenotypic plasticity is important in the face of anthropogenic climate change. Both aboveground and belowground traits respond to the environmental conditions, potentially in co-ordination, but belowground traits are often neglected in ecophysiological studies. Here, we applied factorial heat and drought treatments using the Australian Mountain Research Facility’s FutureClim experiment: 20 future climate simulation plots with active heating (+4°C) and Drought Net-style shelters that reduce incident precipitation by 80%. We transplanted 600 plants (5 species and 3 growth habits: 1 graminoid, 2 forbs, 2 shrubs) in the FutureClim experiment and measured plant survival, growth, and performance over 19 months before destructive harvesting. Total mortality was 144 plants (24%), 94 of which occurred in drought and heat+drought treatments. Growth measures and water potentials were strongly impacted by treatment effects, but consistent trait plasticity across growth forms was only observed in leaf area and root-to-shoot ratio. Generally, forbs showed some negative responses to drought and mixed responses to heat+drought treatments but were unaffected by heat alone. Shrubs that survived the initial transplant, however, responded favourably and vigorously to heat and heat+drought treatments while largely not responding to drought alone. Across both aboveground and belowground traits, we observed strong species-specific differences in traits and their responses to treatments over time. Overall, our results from this field manipulation experiment show that different species have vastly different responses to heat and drought, alone and in combination, which potentially has consequences for community compositional change with ongoing climate change.