Climate control of terrestrial carbon exchange across biomes and continents

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45°N). The sensitivity of NEE to mean annual temperature breaks down at ∼16 ®C (a threshold value of mean annual temperature), above which no further increase of CO,.2uptake with temperature was observed and dryness influence overrules temperature influence. © 2010 lOP Publishing Ltd

Climate control of terrestrial carbon exchange across biomes and continents

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Climate control of terrestrial carbon exchange across biomes and continents This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 Environ. Res. Lett. 5 03400

Climate Control of Terrestrial Carbon Exchange across Biomes and Continents

Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predicate future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate-carbon cycle feedbacks1, 2. However, knowledge of even the broad relationships between climate and terrestrial CO2 exchange with the atmosphere on yearly to decadal scales remains highly uncertain. Here we present data describing net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 132 unique sites including various ecosystems over 6 continents with a total of 583 site-years. With respect to controlling factors we find two distinct groupings of sites: (1) a temperature-limited group where NEE has an exponential relationship with mean annual temperature; and (2) a dryness-limited group where NEE has an inverse exponential relationship with the dryness index7. A strong latitudinal dependence emerges, with 92% of the temperature-limited sites located above 42oN, and 77% of the dryness-limited sites located below 42oN. The sensitivity of NEE to mean annual temperature breaks down at a threshold value of ~16oC, above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence. Our findings suggest that (1) net ecosystem carbon exchange is highly limited by mean annual temperature at mid- and high-latitudes, and (2) net ecosystem carbon exchange is highly limited by dryness at low latitudes.JRC.H.2-Air and Climat