DISSERTATION RESEARCH: Determining the drought sensitivity of the Amazon forest

大多数大型计算机模型预测新环境条件下森林动态的能力有限，因为植物间竞争的关键过程和对水分胁迫的生理反应没有得到充分体现。该项目解决了这两个基本问题，方法是将树木中水运动的更现实的水动力学模型纳入旨在预测森林组成和结构变化的大尺度模型。为了约束模型，需要直接实地测量树木茎中水分的电导率，以及土壤中水分利用率低导致植物活力丧失的点。该项目将能够收集这些关键的现场数据。本研究探讨了导致树木在极端水分胁迫下死亡的基本机制，特别是控制植物水分利用和适应水分胁迫的生理特性。这些信息将在建模框架内形式化，然后可以用来确定极端干旱下动态热带森林中导致生存或死亡的基本过程和相关权衡，并预测随着降水模式的变化，物种组成的变化将如何发挥作用。这个项目将填补我们在热带树木用水和压力方面的知识空白。随着模型的更新和耦合，可以在预测亚马逊森林将如何随着气候变化在未来一百年的演变方面取得进展。

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.