Wendy Peterman and Dominique Bachelet, Conservation Biology Institute, Corvallis, OR
Climate change is an important factor leading to forest dieback and species migration as they relate to drought, water stress, early snow melt, reduced snow cover, pest outbreaks and fire risk (McKenzie et al. 2004, Mote et al. 2005, van Mantgem et al. 2009, Allen et al. 2010). In the North Pacific landscape, precipitation as rainfall is projected to increase in winter and spring, and decrease in summer, while temperatures rise from 2 to 5o C by 2080 (Mote and Salathe, 2010). Current models suggest that forest cover may increase briefly at high elevation in response to wetter winters, and dramatically decrease at lower elevation due to severe competition for water from shrubs and grasses (CIG, 2011). Others, however, suggest that there may be a vegetation shift to lower elevations due to a more favorable water balance (Crimmins et al, 2011). In order to reconcile these differing views, we will examine the soil characteristics that govern the reception, storage, and redistribution of precipitation, which in turn determine the supply of plant-available water seasonally and spatially. A closer examination of soil characteristics can give scientists and managers the tools they need to predict where trees will be most vulnerable to water stress in changing climates. This project will develop a soil vulnerability index and map indicating where forest cover will be most affected by climate change. Using this map, we will develop a greater understanding of potential changes in soil moisture and temperature regimes under future climate conditions. We will evaluate how this information can be used to improve vegetation models across the landscape. We will compare the results of different modeling approaches to the soil vulnerability map, synthesize the state of knowledge and uncertainty, and introduce management implications for action.