Assessing Ecosystem-Level Water Relations Through Stable Isotope Ratio Analyses

Abstract

Virtually all elements of biological interest have multiple stable isotopic forms and the fractionation events associated with biological and physical processes help to create spatial and temporal variations in isotopic abundance that can be used to understand the dynamics of ecological systems. Stable isotope ratio analyses at natural abundance levels can provide integrated information on ecosystem functioning, such as variations in water-use activities by different elements within an ecosystem (Ehleringer et al. 1993; Dawson and Ehleringer 1998). Stable isotope ratio analyses do not provide information on water flux rates through the ecosystem, but instead they help constrain the analysis of flux data, such as through identifying those specific soil layers that are the source of current moisture use by the vegetation or the ratio of carbon dioxide-to-water (CO2-to-H2O) flux.