Environmental, Physiological and Biochemical Processes Determining the Oxygen Isotope Ratio of Tree-Ring Cellulose
Xin Song, Andrew M. Lorrey, Margaret M. Barbour
Abstract
Abstract Analysis of the oxygen isotope ratioof tree-ring cellulose (δ 18 O cell ) is a promising tool for reconstructingpast climatic variations and their influence on terrestrial ecosystems, but control mechanisms of δ 18 O cell are multi-faceted, involving a number of fractionation steps along the oxygen transfer pathway from precipitation water to the site of cellulose formation. The goal of the current chapter is to provide an overview of the current knowledge concerning fractionation mechanisms related to δ 18 O cell . The review is organized by using the currently widely-used δ 18 O cell model as a reference context, and is focused on three main determinants of δ 18 O cell : source water isotope ratio (δ 18 O sw ), leaf water isotope enrichment (Δ 18 O lw ), and biochemical fractionations downstream of Δ 18 O lw . For each component, we summarize environmental, physiological, and/or biochemical processes underlying 18 O fractionations, and provide explanations of how these processes are critically relevant for linking δ 18 O cell to climatic factors in real-world scenarios. We identify knowledge gaps in mechanistic controls of δ 18 O cell , and highlight opportunities for more research to improve upon the existing model.