SGER: An Analysis of Biotic and Physical Factors in El Nino-Induced Landslides

1997-1998年的厄尔尼诺（ENSO）事件在整个加利福尼亚中部沿海地区造成了极高的降雨，并产生了大量的山体滑坡。这些滑坡改变了景观的形状和植被特征。这些滑坡的分布似乎与物理和生物因素的特定组合有关。坡度、母质和土壤含水量影响滑坡和泥石流发生的概率，植被的生根特性和动物活动也影响滑坡和泥石流发生的概率。该项目将调查滑坡事件的分布，以检查这些生物因素的重要性及其运作机制。在圣巴巴拉附近的加州大学自然保护区系统的塞奇威克保护区，人们观察到，由于生长在上面的植被，具有相同几何形状和母质的山坡似乎表现出不同的滑坡概率。具体来说，沿海鼠尾草灌木群落的地区似乎比周围的草原更容易出现滑坡。本项目将记录这一现象，并检查可能导致这一现象的因素。特别是，它将研究根系密度的差异和下层植被的发生率作为导致滑坡的潜在原因。它还将测试在鼠尾草灌丛地区并不常见的地鼠，是否会通过挖洞来增加草原的排水。该项目将有助于了解生物对景观水文的影响，并为加州该地区的保护策略的发展提供重要信息。

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.