Interannual Variability in Amazonian Net Ecosystem Production: Implication for Regional Carbon Cycle.

Interannual variability in Amazonian terrestrial ecosystems functioning during the past two decades is examined in order to estimate the range of variations in biogenic sources and sinks of CO2 as well as the changes in the biophysical conditions affecting regional climate. We simulated interannual patterns of vegetation characteristics using Ecosystem Demography (ED) model. This is a mechanistic terrestrial biosphere model which simulates both the fast time scales (hours) of carbon and water fluxes and the longtime scales of ecosystem dynamics. The NCEP/NCAR reanalysis climate data set and regional precipitation data sets drive the simulations of ED model. We explore sensitivities of tropical ecosystem photosynthetic production and respiration to variation in temperature, precipitation, atmospheric humidity, radiation and wind conditions. The simulated inter-annual variations in the state of Amazonian ecosystems suggests that short -term changes in the state of vegetation could have salient effect on the global carbon cycle as well as regional climatic conditions.