Hillslope roughness reveals forest sensitivity to extreme winds

Abstract

Windthrow, or the uprooting of trees by extreme wind gusts, is a natural forest disturbance that creates microhabitats, turns over soil, alters hydrology, and removes carbon from the above-ground carbon stock. Long recurrence intervals between extreme wind events, however, make direct observations of windthrow rare, challenging our understanding of this important disturbance process. To overcome this difficulty, we present an approach that uses the geomorphic record of hillslope topographic roughness as a proxy for the occurrence of windthrow. The approach produces a probability function of the number of annual windthrow events for a maximum wind speed, allowing us to explore how windthrow or tree strengths may change due to shifting wind climates. Slight changes to extreme wind speeds may drive comparatively large changes in windthrow production rates or force trees to respond and change the distribution. We also highlight that topographic roughness has the potential to serve as an important archive of extreme wind speeds.

Quantifying patch size distributions of forest disturbances in protected areas across the European Alps

“…In contrast, the dominant processes causing the largest disturbance patches in the Alps (i.e. avalanches and wind) are triggered by climatic extremes and their impact is modulated by topography (Doane et al., 2023; Schweizer et al., 2003; Teich et al., 2012). While effect sizes for individual variables had wide confidence bands, temperature amplitude was found to be the most important factor influencing disturbance size distributions.…”