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PI-Submitted Research Highlights for
Terrestrial Ecosystem Science Program

Diversity in plant hydraulic traits explains vegetation dynamics in seasonally dry tropical forests

David Medvigy
University of Notre Dame

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Plant hydraulic-enabled ecosystem model simulates variations in tropical dry forest phenology and tree growth

The ScienceĀ 
Ecosystem models have struggled to accurately represent the effects of plant water stress. A team at the University of Notre Dame have developed and tested a novel model to describe how plant hydraulic traits constrain vegetation dynamics on multiple time scales.

The Impact
The team presents a demographic ecosystem model that mechanistically represents plant water stress based on hydraulic traits. They show that this type of model can explain why different plant functional types exhibit different leaf-area phenology and growth rates.

Summary
A team of researchers have updated the Ecosystem Demography model 2 (ED2) with a trait-driven mechanistic plant hydraulic module that can track water flows within trees. The model is also coupled with novel stomatal and drought phenology schemes. Four plant functional types with strategies ranging from conservative slow-growing to acquisitive fast-growing were parameterized on the basis of meta-analysis of plant hydraulic traits. Simulations from both the original and the updated ED2 were evaluated against 5 years of field data from a Costa Rican seasonally dry tropical forest site and remote-sensing data over Central America. Compared with the original ED2, predictions from their novel trait-driven model matched better with observed growth, phenology and their variations among functional groups. Notably, the original ED2 produced unrealistically small leaf area index (LAI) and underestimated cumulative leaf litter. Both of these biases were corrected by the updated model. The updated model was also better able to simulate spatial patterns of LAI dynamics in Central America. These results demonstrate that mechanistic incorporation of plant hydraulic traits is necessary for the simulation of spatio-temporal patterns of vegetation dynamics in seasonally dry tropical forests in vegetation models.

Contacts (BER PM)
Daniel Stover
SC-23.1
Daniel.Stover@science.doe.gov (301-903-0289)

(PI Contact)
David Medvigy
Associate Professor, University of Notre Dame, Notre Dame, IN 46556
dmedvigy@nd.edu

Funding
US Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program under award number DE-SC0014363. National Science Foundation CAREER Award DEB-1053237. NASA Carbon Cycle Science Program Award NNX11AD45G. Princeton Environmental Institute and the Andlinger Center for Energy and the Environment at Princeton University.

Publications
Xu, X., Medvigy, D., Powers, J. S., Becknell, J. M. & Guan, K. Diversity in plant hydraulic traits explains seasonal and inter-annual variations of vegetation dynamics in seasonally dry tropical forests. New Phytol. 212, 80-95 (2016).

Performers:

David Medvigy, Xiangtao Xu (Princeton University); Jennifer Powers (University of Minnesota); Justin Becknell (Brown University); Kaiyu Guan (University of Illinois Urbana-Champaign).

Principal Funding Source: US Department of Energy, Office of Science, Office of Biological and Environmental Research, Terrestrial Ecosystem Science (TES) Program under award number DE-SC0014363.

Other Funding Sources:

National Science Foundation CAREER Award DEB-1053237; NASA Carbon Cycle Science Program Award NNX11AD45G; Princeton Environmental Institute and the Andlinger Center for Energy and the Environment at Princeton University

Software Codes Advanced:

The ED2 model. Model code available on the journal website.

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