Simulations of future climate in tropical forests show a risk of increased mortality due to plant
water stress, unmitigated by rising CO 2 levels.
Robbins, Z., Chambers, J., Chitra‐Tarak, R., Christoffersen, B., Dickman, L. T., Fisher, R., … & Xu, C. (2024). Percentage of days with hydraulic failure at (a) > 60% and (b) > 80% loss of conductivity projected by the vegetation model, FATES-HYDRO, at Barro Colorado Island, Panama, under contemporary climate conditions), two future climate scenarios,and two CO2 levels.
The Science
There will be a future risk of increased tropical forest mortality under climate change due to increasing plant water stress due to warming temperatures. Rising atmospheric carbon levels do not mitigate mortality risk but increase plant productivity. We further find that plant traits are crucial to determining this mortality risk.
The Impact
Tropical forests have significant impacts on global water and carbon cycles. Adapting to global climate change will require an understanding of the change to these crucial resources. We show that increasing temperature and drying may increase tropical forest mortality. This is due to increased plant water stress. Increased atmospheric carbon levels were thought to potentially mitigate this loss, but our model shows it does not at these levels of warming. These increasing mortality levels could significantly reduce tropical carbon storage. Global climate change will increase the annual productivity of these forests but remove more water from these forests.
Summary
We used a dynamic vegetation model with plant hydrodynamics (FATES-HYDRO) to simulate the stand-level responses to future climate changes in a wet tropical forest in Barro Colorado Island, Panama. We calibrated the model by selecting plant trait assemblages that performed well against NGEE tropics observations of plant hydrodynamics. These assemblages were run with temperature and precipitation changes for two greenhouse gas emission scenarios (2086–2100: SSP2-45, SSP5-85) and two CO2 levels (contemporary, anticipated). Simulations show an increase of 5.7% to 10.1–11.3% under future climate scenarios due to increasingly negative leaf water potentials. Gross primary productivity increased 27–53% under future climate but decreased (-21%–8.6% ) without rising CO2. Minimum annual leaf water potential ( a measure of plant stress) under contemporary simulations decreased under both future scenarios with anticipated CO2 and under contemporary CO2 scenarios (indicating greater plant stress). Trait assemblage members which experienced hydraulic failure had substantially more negative minimum season leaf water potential (−1.376 MPa) than those who did not (−0.815 MPa). Simulation analysis shows plant traits played a more significant role in the risk of hydraulic failure (98%) than climate scenarios or models.
Contact:
Zachary Robbins
Los Alamos National Lab, Postdoctoral researcher
zjrobbins@lanl.gov
Chonggang Xu
Los Alamos National Lab, Staff Scientist
cxu@lanl.gov
Funding
This research was supported as part of the Next Generation Ecosystem Experiments-Tropics, funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research.
Publications
Robbins, Z. et al. Future climate doubles the risk of hydraulic failure in a wet tropical forest. New Phytologist (2024) doi:10.1111/nph.19956.