WCR: Vegetation Control of Ecohydrologic Processes

Trustees Of Boston University, Boston

Investigators

Abstract

0233643 Phillips As a major currency in the economy of terrestrial ecosystems, water is acquired, saved, and spent much like money in human economies. Like human use of financial resources, vegetation does not generally take up and release water at the same instantaneous rate, but rather buffers supply of and demand for water by banking this critical resource in internal storage organs. Understanding how and when vegetation captures, stores, and transports water from roots to and out of foliage is critical to quantifying diverse eco-hydrologic functions such as watershed buffering of rainfall-runoff relationships and flood responses, and ecosystem uptake of atmospheric carbon dioxide. This study examines the physiological controls exerted by vegetation on forest-atmosphere water transport, at Harvard Forest, Massachusetts. The specific objective of this proposal is to quantify, using a novel diagnostic method, how forest vegetation responds hydraulically to variation in environmental stimuli. The methodology used here imposes short-lived disturbances of humidity, light and rainfall on canopies and root systems, and then traces the propagation of these perturbations through trees and soil. This .ripple. effect contains the integrated signature of key hydraulic properties and processes within vegetation, that govern the overall control that vegetation exerts on ecosystem hydrology. This novel methodology is highly manipulative and produces large signal to noise ratios for analysis, but does not cause irreversible ecological disturbances, such as damage or destruction of plant roots, stems, and branches. Most importantly, this methodology will yield fundamental insights into the dynamic relationships and feedbacks among vegetation properties and physiology, atmospheric forcing, and evaporative fluxes from forests. Finally, this project provides broad educational impacts by integrating research with focused educational activities in three existing programs: