Globally, forests are an important carbon sink that offset 25% of anthropogenic carbon dioxide emissions. Forests comprise 413 million ha (33% of the land area) of the eastern U.S. and are currently a net carbon sink. The dynamics controlling carbon sequestration are sensitive to climate. Mean annual air temperatures for the northeastern and southeastern U.S. are projected to increase 3 to 5 °C by the year 2100, which will increase the length of the growing season, but also increase the severity and frequency of water stress. Tree ring series offer opportunities to quantify relationships between tree growth and a suite of climate conditions and advance understanding of forest carbon cycling response to climate change. Tree ring width typically reflects the growing conditions during its corresponding year, and can be used to reconstruct past environmental conditions. We analyzed several thousand tree ring chronologies from the International Tree-Ring Data Bank and climate data (e.g., precipitation, temperature, and incoming short-wave radiation) from the National Centers for Environmental Prediction (NCEP I and II) and Climatic Research Unit -NCEP (CRUNCEP) to quantify relationships and regional variations in the response of tree growth to local meteorological conditions across the eastern U.S.
Results/Conclusions
We found that tree growth in the northeastern U.S. exhibited a strong, positive linear correlation with mean annual precipitation, but had little to no response to variations in mean annual air temperature. The trees in this region had a nonlinear relationship with shortwave-radiation that resulted in various thresholds of tree growth. We found that within the southeastern U.S., there are regional variations within some sites in the relationship between mean annual air temperature and tree growth beyond a mean annual air temperature of approximately 13°C where growth within the sites had a positive relationship with mean annual air temperature and growth in other sites showing a negative relationship with mean annual air temperature. These relationships highlight the importance of quantifying forest-atmosphere interactions for advancing our understanding of forest carbon cycle response to a changing climate. Ongoing analyses are exploring regional variations in tree growth response to drought and water stress.