摘要：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
CO2 exchange 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
CO2 uptake with temperature was observed and dryness influence overrules temperature
influence.
