The effect of temperature on CO2 flux
Collaborators:
Steve Oberbauer - Florida International University - Miami, FL.
The standard ITEX experiment originally focused on the phenology and growth of individual plants and later, communities, in response to experimental warming. However, the standardized ITEX experiments also represent a tremendous opportunity to examine ecosystem function in response to warming across latitudinal and moisture gradients. One integrative measure of ecosystem function is net ecosystem exchange of carbon (NEE), which has relevance to biogeochemical cycling at larger scales.
As part of the North American ITEX project (NATEX), we initiated measurement of carbon fluxes of the ITEX warming experiments across the latitudinal and moisture gradients represented by our sites (Alexandra Fiord, Barrow, Atqasuk, and Toolik). Fluxes were assessed using static chamber techniques conducted over 24 hr periods sampled regularly throughout the summer of at least two years for each site. At Toolik, warming increased carbon losses at both moist and dry sites.
In contrast, at both Atqasuk and Barrow, warming increased carbon uptake at wet sites and increased carbon losses from dry sites. At Alexandra Fiord, warming increased uptake at moist sites, but for both wet and dry sites the response depended on the sample year. For both wet and dry sites in Alaska, warming increased gross photosynthetic uptake, even in sites that had greater net carbon losses with warming.
The results indicate that the respiration response to warming determines whether the carbon balance of a site becomes more positive or negative with warming.