Reichman et al. 98 13668 The 1997-1998 El Ni o (ENSO) event has caused extremely high rains throughout central coastal California and these have generated a large number of landslides. These landslides change the shape of the landscape and its vegetational characteristics. The distribution of these landslides appears to be related to a specific combination of physical and biological factors. Slope, parent material and soil water content influence the probability of slumping and mudslides as do the rooting characteristics of vegetation and animal activities. This project would investigate the distribution of landslide events to examine the importance of these biotic factors and the mechanisms by which they operate. On the Sedgwick Reserve in the University of California Natural Reserve system near Santa Barbara, it has been observed that hillslopes with the same geometry and parent materials appear to exhibit different probabilities of slumping due to the vegetation that occurs on them. Specifically, it appears that areas with coastal sage scrub communities are much more likely to exhibit slides than are grasslands that surround them. This project will document this phenomenon and examine the factors that may be causing it. In particular, it will examine differences in root density and the incidence of understory vegetation as potential causal factors driving landslides. It will also test whether gophers, which are not common in sage-scrub areas, increase the drainage of water from grasslands through their development of burrows. This project will contribute to an understanding of biotic influences on landscape hydrology and provide important information for the development of conservation strategies for this region of California.
