*Principal Investigator Does Thinning Improve the Soil Water Balance and Vegetation Health of Southern Californian Forest?

High levels of tree mortality occurred in Southern California forests in 2002-03 (Minnich 2007). This study uses two objectives (obj) to understand this mortality. Obj. 1 is to characterize the spatial patterning of dead trees and determine the role that plant and soil water availability played in structuring mortality patterns at multiple scales. Obj. 2 is to understand the physiological mechanisms driving this mortality and the importance of stand thinning on improving soil-water availability at the tree level. We have made significant progress on obj. 1 and have begun work on obj. 2 (see table 1). Approach and Procedures Fourteen 300m long belt transects spaced 400 feet in elevation spanned an elevation gradient along the north-west aspect of the San Jacinto mountains (fig 1a; transects in red). Cover was recorded along each transect by species for live and dead vegetation. Nearly all dead-trees from the 2002-03 mortality event remained standing and retained branches down to ~.25 inches at the time of the survey. We use these standing dead trees to quantify mortality (the cover that is dead). Diameter at Breast Height (DBH) was recorded in 0.1 ha plots located at each transect and seedlings were counted in the plots. Cloud-free, summer Landsat images from 1984 to 200