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Research article - Peer-reviewed, 2021

Isotopic Branchpoints: Linkages and Efficiencies in Carbon and Water Budgets

Marshall, John D.; Laudon, Hjalmar; Makela, Annikki; Peichl, Matthias; Hasselquist, Niles; Nasholm, Torgny

Abstract

Forests pass water and carbon through while converting portions to streamflow, soil organic matter, wood production, and other ecosystem services. The efficiencies of these transfers are but poorly quantified. New theory and new instruments have made it possible to use stable isotope composition to provide this quantification of efficiencies wherever there is a measurable difference between the branches of a branchpoint. We present a linked conceptual model that relies on isotopes of hydrogen, carbon, and oxygen to describe these branchpoints along the pathway from precipitation to soil and biomass carbon sequestration and illustrate how it can be tested and generalized.Plain Language Summary The way a forest works can be described in terms of carbon and water budgets, which describe the ways that carbon and water flow through the forest. The paths of such flows are frequently branched and the branches are often different in their stable isotope composition. This means that stable isotopes can be used to describe the branching events. We present isotopic methods of quantifying several such events, then link them in a chain that begins with the evaporation of water and ends with biomass production.

Keywords

carbon-use efficiency; ecosystem model; eddy covariance; photosynthesis; transpiration; water-use efficiency

Published in

Journal of Geophysical Research: Biogeosciences
2021, Volume: 126, number: 1, article number: e2020JG006043
Publisher: AMER GEOPHYSICAL UNION