INVESTIGATING THE EFFECTS OF SHORT- AND LONG-TERM CLIMATIC VARIATION ON THE WATER USE OF THREE NORTHERN HARDWOOD TREE SPECIES

Many tree species are expected to decline in the northern Midwestern United States due to climate change increasing annual temperature 3-5º C by 2100. Sugar maple (Acer saccharum), an economically important timber and syrup species, is not expected to be sustainable in its current range under projected future climate, while trembling aspen (Populus tremuloides) and red maple (Acer rubrum) are expected to react more favorably to climate change. The success of individual tree species is dependent on how climate change will alter a species environment in regards to water use. Climate change could potentially reduce available soil moisture, reducing potential transpiration within a forest. This dissertation had three objectives; 1) to investigate the effects of experimental soil warming and irrigation on transpiration rates of sugar maple over three growing seasons, 2) to investigate the effects of environmental drivers on water use of trembling aspen and red maple, and to 3) investigate the effects of wounding on the accuracy of sap flux estimates in heat dissipation sensors. Overall, we found that drought effects due to climate change could potentially decrease sugar maple productivity on drier sites within its current range. Further, trembling aspen had higher rates of transpiration, growth and water use efficiency than red maple indicating that trembling aspen may not react as unfavorably to climate change as expected. Finally, we found wounding effects caused an underestimation in sap flux data in sugar maple and trembling aspen when probes remained in trees for two years