Informing climate models with rapid chamber measurements of forest carbon uptake.
Models predicting ecosystem carbon dioxide (CO2
) exchange under future climate change rely on relatively few real-world 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
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.
Metcalfe, DB; Ricciuto, D; Palmroth, S; Campbell, C; Hurry, V; Mao, J; Keel, SG; Linder, S; Shi, X; Näsholm, T; Ohlsson, KEA; Blackburn, M; Thornton, PE; Oren, R
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