DISSERTATION RESEARCH: Determining the drought sensitivity of the Amazon forest

Harvard University, Cambridge MA

Investigators

Abstract

Most large scale computer models are limited in their ability to predict the dynamics of forests under novel environmental conditions because the critical process of inter-plant competition and the physiological responses to water stress are not adequately represented. This project addresses these two fundamental problems by incorporating a more realistic hydrodynamic model of water movement in trees into a large scale model designed to predict changes in the composition and structure of forests. Direct field measurements of the conductivity of water in stems of trees and the point at which low water availability in the soil leads to a loss in plant vigor are required to constrain the model. This project will enable these critical field data to be collected. This research addresses the fundamental mechanisms that cause a tree to die under extreme water stress, particularly the physiological traits that control plant water use and adjust under water stress. That information will be formalized within the modeling framework that can then be used to identify the fundamental processes and associated tradeoffs that lead to survival or mortality within a dynamic tropical forest under extreme drought, and predict how shifts in species composition will play out as precipitation patterns change. This project will fill a large gap in our knowledge about water use and stress in tropical trees. With the models updated and coupled, advances can be made in terms of predicting how forests of the Amazon will evolve as climate change evolves over the next hundred years.