Environmental and ecological drivers of drought deciduousness across the Neotropics
Abstract
Ongoing changes in climate will increase the recurrence of extreme hot drought events across the tropics throughout the 21st century. To understand how ecosystems will respond to frequent water stress, terrestrial biosphere models must represent trade-offs between structural and physiological traits associated with primary productivity and drought adaptation. In this study, we focus on drought deciduousness, which is an important drought avoidance strategy that coexists with evergreenness at different abundance levels across the tropics. We implemented a tropical drought-deciduous plant functional type (PFT) into the Functionally Assembled Terrestrial Ecosystem Simulator coupled to the E3SM Land Model (ELM-FATES), a terrestrial biosphere model that represents the structural and functional diversity of vegetation canopies across landscapes along environmental gradients. To constrain the trait trade-offs between evergreen and drought deciduous PFTs in ELM-FATES, we pooled physiological and structural trait data from existing databases and published literature. To test the model's ability to represent different evergreen-deciduous coexistence levels, we selected multiple sites spanning across a broad precipitation gradient (500-3000 mm yr-1) in tropical South America. We focused on sites that had in situ forest structure data, meteorological drivers and eddy covariance flux towers. The model correctly represented the higher abundance of drought deciduous trees at the Caatinga dry forest sites as well as the seasonal cycle of evapotranspiration and gross primary productivity. At these regions, evergreen PFTs are outcompeted during the droughts of 2012 and 2015, due to extended periods of low productivity and high maintenance costs for living tissues. In contrast, ELM-FATES overestimated the abundance of drought deciduous trees in the Amazon, indicating that current trade-offs in the model under low water stress are not strong enough to capture the observed dominance of evergreen PFTs. Our results highlight the need to fully integrate field measurements and model development to better understand the drivers of functional coexistence and ecosystem response to gradients in water availability and to extreme events in the tropics.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.B52C..06L