Das Projekt "Regional response of forest productivity to the North American Monsoon System along a broad climatic gradient" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: University of Arizona, Laboratory of Tree-Ring Research.Forests worldwide act an important sink and compensate for a large portion of anthropogenic fossil fuel emissions. However, the lack of large-scale and long-term empirical data linking absolute estimates of ecosystem productivity with climate variability and change is a major caveat for reliable quantifications of the terrestrial carbon balance. Thus, the proposed study aims to comprehensively assess regional-scale forest productivity and its short to long-term trends in response to the dominant atmospheric circulation patterns. Research will be conducted in the Southwestern United States where climate variability is primarily driven by the North American Monsoon System (NAMS). A combination of innovative and well-established methodologies (e.g. tree-ring based annual biomass estimates, tree-ring stable isotope chronologies, eddy-covariance measurements and terrestrial biosphere models) will be utilized to empirically assess regional annually resolved net ecosystem productivity (NEP). Thereby, a broad climatic gradient ranging from drought to temperature stressed sites will be covered and observed changes in forest carbon stocks attributed to NAMS variability. In addition to addressing regional impacts in the southwest USA, the investigated climate regimes serve as a warm and dry analogue to predicted European climate. It is anticipated that this research will also provide valuable insights as to future forest productivity and related carbon sequestration potential in Europe and many other mid-latitude regions. This study is expected to i) provide valuable annually-resolved empirical data on forest productivity, ii) contribute to reduced uncertainties in assessments of regional forest carbon sink dynamics, iii) allow conclusions to be made for future ecosystem productivity, and iv) support integrated assessments of major atmospheric circulation patterns and their impacts on the terrestrial carbon cycle.