PARENT SESSION
Oral Session #87: Ecosystem Ecology.
Presiding: B. Currie
Thursday, August 8. 1:00 PM to 3:45 PM. Graham Meeting Room, TCC.
Latitudinal variation in forest community productivity: A comparison between North America and Europe.
Ignace, Danielle*,1, Economo, Evan1, Enquist, Brian1, Huxman, Travis1, 1 University of Arizona, Tucson, AZ
ABSTRACT- The mechanistic link between species richness and ecosystem level processes such as productivity is one of the most debated issues in ecology. This is especially important in light of climatic change which will likely alter the distribution of species and potentially influence ecosystem processes. Obtaining accurate estimates of productivity has been a difficult task often involving the use of surrogate variables. We utilize a global database on terrestrial carbon flux to assess patterns of productivity, respiration (RE), and net ecosystem exchange (NEE) across broad biotic and abiotic gradients. Eddy covariance micro-meteorological techniques provide a more realistic and standardized method for measuring ecosystem level gross primary production (GPP). By using a latitudinal gradient as a surrogate for species richness we compare and contrast patterns of productivity in North American and European forests. In a previous analysis of European forests, Valentini et al. (2000) showed that GPP remained constant over latitude. Our results differ from Valentini showing that GPP and RE decreased with increasing latitude for North America and Europe, while NEE remained similar. We show how differences in calculations of daily respiration can yield important exceptions. Temperature appears to be influencing the differences in GPP and RE observed between North America and Europe. Accurate estimates of daily RE and GPP could influence the unification of our understanding of the relationship between productivity and species richness. This project represents the first time fluxnet data has been used to highlight macroecological properties of forest ecosystems. Our results are consistent with the expectation that temperature is driving the differences observed between North American and Europe, and not biotic patterns inherent to latitude, such as species richness or variation in physiological capacity.
KEY WORDS: Ecosystem Processes, Carbon Flux, Species Richness, Productivity, Respiration and Net Ecosystem Exchange