Temperature-driven changes in tree species abundance and carbon cycling along latitudinal and altitudinal gradients

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Temperature-driven changes in tree species abundance and carbon cycling along latitudinal and altitudinal gradients ***Global warming is expected to alter the composition and productivity of forests, particularly at high latitudes and altitudes where temperature will increase the most. These changes may have significant economic and social consequences, as well as cascading environmental impacts, such as changes in forest carbon storage that may exert a positive or negative feedback on the rate climate change. Predicting the impacts of global warming requires a better understanding of how temperature influences the species composition and productivity of forests. Toward this end, the proposed research will use forest inventory data to examine how trees and forests respond to spatial variation in temperature. Employing space-for-time substitution, the inventory data will also be used to parameterize a model for predicting how forests will respond to global warming, including responses that may exert a positive or negative feedback on climate change. ****The two study regions span broad latitudinal and altitudinal gradients: a) northern forests spanning the temperate-boreal ecotone in eastern North America, from 35° to 50° latitude; b) montane forests spanning the deciduous-coniferous ecotone in the Swiss the Alps, from 500 to 1500 meters above sea level.*** ****The four main objectives of the research are: 1) to determine how geographic variation in temperature influences the recruitment, growth and mortality of different tree species; 2) to assess the relative importance of recruitment, growth, and mortality in limiting abundance near species' range limits; 3) to elucidate how geographic variation in temperature influences forest productivity and biomass turnover, both directly though changes in tree growth and mortality, and indirectly via changes in species composition; 4) to predict how the direct and indirect effects of temperature will alter carbon cycling over the next century of global warming.****The proposed research will be of broad interest to scientists studying climate change because it will test fundamental hypotheses regarding the species composition and productivity of forest ecosystems that play a key role in the global carbon cycle. The results will also be valuable to society at large, including natural resource managers and policy makers who need to know how climate change will impact forests and the wildlife and humans that inhabit them. Finally, the predictions regarding changes in forest composition and productivity will be of economic interest to the forest sector, whose silvicultural strategies and production forecasts must adjust to the impacts of global warming.**