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Research article - Peer-reviewed, 2017

Informing climate models with rapid chamber measurements of forest carbon uptake

Metcalfe, Daniel B.; Ricciuto, Daniel; Palmroth, Sari; Campbell, Catherine; Hurry, Vaughan; Mao, Jiafu; Keel, Sonja G.; Linder, Sune; Shi, Xiaoying; Nsholm, Torgny; Ohlsson, Klas E. A.; Blackburn, M.; Thornton, Peter E.; Oren, Ram

Abstract

Models predicting ecosystem carbon dioxide (CO2) exchange under future climate change rely on relatively few realworld tests of their assumptions and outputs. Here, we demonstrate a rapid and cost-effective method to estimate CO2 exchange from intact vegetation patches under varying atmospheric CO2 concentrations. We find that net ecosystem CO2 uptake (NEE) in a boreal forest rose linearly by 4.7 +/- 0.2% of the current ambient rate for every 10 ppm CO2 increase, with no detectable influence of foliar biomass, season, or nitrogen (N) fertilization. The lack of any clear short-term NEE response to fertilization in such an N-limited system is inconsistent with the instantaneous downregulation of photosynthesis formalized in many global models. Incorporating an alternative mechanism with considerable empirical support -diversion of excess carbon to storage compounds -into an existing earth system model brings the model output into closer agreement with our field measurements. A global simulation incorporating this modified model reduces a long-standing mismatch between the modeled and observed seasonal amplitude of atmospheric CO2. Wider application of this chamber approach would provide critical data needed to further improve modeled projections of biosphere-atmosphere CO2 exchange in a changing climate.

Keywords

boreal forest; earth system model; model-data integration; nutrient limitation; photosynthetic downregulation; Pinus sylvestris

Published in

Global Change Biology
2017, Volume: 23, number: 5, pages: 2130-2139