The role of windstorm exposure and yellow cedar decline on landslide susceptibility in southeast Alaskan temperate rainforests

- 295 landslides were investigated for relationship with wind exposure and forest decline.
- Landslide occurrence positively correlated with exposure to wind disturbance.
- Cedar decline, significant at small scales, was not significant at large scales.
- Disturbance interactions were only significant at high slopes.
- Disturbance interaction research should focus on limiting factors for occurrence.

Interactions between ecological disturbances have the potential to alter other disturbances and their associated regimes, such as the likelihood, severity, and extent of events. The influence of exposure to wind and yellow cedar decline on the landslide regime of Alaskan temperate rainforests was explored using presence-only modeling techniques. The wind regime was found to be a significant influence on the spatial distribution of landslide events. This effect was mediated by slope, with little interactive effects at low angles and stronger influences on steeper slopes. Mechanistically, the interaction appears to be mediated by root strength, which is an important factor in stability of high-angle slopes. Yellow cedar decline, despite increasing landslide susceptibility in fine-scale studies, was not significant-although a stronger relationship may develop with time. Overall, inclusion of other disturbances in the modeling framework resulted in a significant spatial refinement when predicting landslide susceptibility. This results from the varying importance of individual disturbance drivers across the landscape, of which only a subset are exposed to potential disturbance interactions. This spatial effect is an important consideration when characterizing landscape-scale disturbance regimes and their interactions with other disturbances.