Bolstad 9806628 Work by scientists over the last decade strongly points to human-caused global warming, and several studies have predicted large changes in the wood production, water production, and distribution of our forests. Some scenarios suggest cool-loving trees such as spruces, firs, and some maples, will retreat northward as climates become too warm. Others suggest forests may die out altogether in some regions, to be replaced by grass or other more drought or heat tolerant life forms. The PIs' study is designed to identify the impacts of changing temperatures on the physiology of eastern deciduous forest trees, and so help better determine how the forests will respond to changing climate. All living organisms respire as the convert food into energy, and plants are no different. However in plants, there is a balance between food production (photosynthesis) and consumption (respiration), which changes, depending on the temperature. The PIs' study is designed to identify just how much plants have adapted to natural changes in temperatures. The PIs will measure respiration across the natural range for white oak and red maple, two species found from Florida to New England to Minnesota to Arkansas. By studying these species in their native locations, and by planting seedlings from all these sources in common gardens, the PIs will determine far plants have adjusted their physiology to natural changes in temperature, and improve our ability to predict how they will respond to future temperature changes.