Chapter 3 Physical causes and consequences for Landslide Ecology

1. The propensity for a landslide to occur is largely determined by potential slip planes, or weakness planes in the geological substrate, where the driving forces exceed resisting forces. 2. Landslide occurrence across the landscape is often unpredictable; substrates can be resistant to slippage for centuries and then suddenly experience instability that may result from human or non-human changes that disrupt the balance between driving and resisting forces at a slip plane. 3. Post-landslide erosion is common and can contribute as much as 33% of the total sediment loss from the site of landslide initiation. Such post-landslide erosion can continue for years, which reduces rates of ecosystem recovery on landslide scars and alters down slope habitats and watersheds. 4. Landslides greatly alter soils through physical losses, gains, and mixing, as well as through chemical changes. Soil organic matter contains critical nutrients and retains moisture; it facilitates soil and plant recovery in microhabitats present after a landslide. In warm, tropical regions, some landslide soil chemistry may recover to pre-landslide conditions within 55 years, yet such recovery is much slower in cooler, temperate regIons