Coevolving topography, patchy soils, and forest structure

• 成果类型: Article
• 署名作者: Rossi, Matthew W.; Tucker, Gregory E.; Anderson, Suzanne P.; Anderson, Robert S.; Mcglinchy, Joseph
• 署名单位: University of Colorado System; University of Colorado Boulder; University of Colorado System; University of Colorado Boulder; University of Colorado System; University of Colorado Boulder; University of Colorado System; University of Colorado Boulder
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2519374123
• 发表日期: 2026-03-24
• 页码: e2519374123
• 关键词: bedrock exposure; soil production; forest structure; lidar analysis; landscape evolution; Modeling; SOUTHERN ROCKY-MOUNTAINS; COLORADO FRONT RANGE; fire regimes; BEDROCK; surface; ALPINE; relief; permafrost; vegetation; emergence

摘要

The transition from soil-mantled to bedrock-dominated landscapes is important to hydrology, ecology, and landscape evolution. Where classical theory predicts that this transition abruptly occurs once erosion rates exceed soil production ones, actual landscapes show a much more gradual transition. The Rampart Range, CO, is an unglaciated, forested mountain range with uniform lithology that spans this transition, providing an opportunity to interrogate how topography, soil cover, and forest structure coevolve. Using drone imagery and airborne lidar, we show the utility of object-based methods that segment the lidar topography into individual outcrops. Lower elevation hillslopes are rockier (similar to 14% rock) than their higher elevation counterparts (similar to 2% rock) due to late Cenozoic incision of a regional, high elevation, low relief surface. After accounting for the erosional control on rockiness, we show that bedrock exposure also depends on topographic aspect. Equator-facing hillslopes are rockier (similar to 20% rock at low elevations; similar to 3% rock at high elevations) than their more heavily forested, pole-facing counterparts (similar to 11% rock at low elevations; similar to 1% rock at high elevations). To simulate these patterns, hillslope evolution models need humped soil production functions that can generate rocky outcrops within a soil mantle. When combined with depth-dependent soil creep, such models readily produce large gradients in the height and frequency of bedrock outcrops in response to aspect-dependent weathering. Given the correspondence between higher forest biomass (e.g., increased tree density, canopy height) with lower bedrock exposure on pole-facing hillslopes, we argue that forest dynamics may be an underappreciated regulator of hillslope morphology via root zone weathering.