Confronting a Process-based Model of Temperate Tree Transpiration with Data from Forests in Central Panama Exposed to Drought
Abstract
Process-based models of tree impacts on the hydrologic cycle must include not only plant hydraulic limitations but also photosynthetic controls because plants lose water to gain carbon. The Terrestrial Regional Ecosystem Exchange Simulator (TREES) is one such model. TREES includes a Bayesian model-data fusion approach that provides rigorous tests of patterns in tree transpiration data against biophysical processes in the model. TREES has been extensively tested against many temperate tree data sets including those experiencing severe and lethal drought. We test TREES against data from sap flow-scaled transpiration in 76 tropical trees (representing 42 different species) in secondary forests of three different ages (8, 25, and 80+ years) located in the Panama Canal Watershed. These data were collected during the third driest El Niño-Southern Oscillation (ENSO) event on record in Panama during 2015/2016. Tree transpiration response to vapor pressure deficit and solar radiation was the same in the two older forests, but showed an additional response to limited soil moisture in the youngest forest. Volumetric water content at 30 and 50 cm depths was 8% lower in the 8 year old forest than in the 80+ year old forest. TREES could not simulate this difference in soil moisture without increasing simulated root area. TREES simulations were improved by including light response curves of leaf photosynthesis, root vulnerability to cavitation and canopy position impacts on light. TREES was able to simulate the anisohydric (loose stomatal regulation of leaf water potential) and isohydric (tight stomatal regulation) of the 73 trees species a priori indicating that species level information is not required. Analyses of posterior probability distributions indicates TREES model predictions of individual tree transpiration would likely be improved with more detailed root and soil moisture in all forest ages data with the most improvement likely in the 8 year old forest. Our results suggest that a biophysical tree transpiration model developed in temperate forests can be applied to the tropics and could be used to improve predictions of evapotranspiration from changing land cover in tropical hydrology models.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.H21D1440E
- Keywords:
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- 1812 Drought;
- HYDROLOGYDE: 1818 Evapotranspiration;
- HYDROLOGYDE: 1836 Hydrological cycles and budgets;
- HYDROLOGYDE: 1843 Land/atmosphere interactions;
- HYDROLOGY