Landscape evolution of the Western Hengduan Mountains with ecological implications

Mountains serve as natural laboratories for investigating how tectonics, climate, and erosion interact across timescales, and how these interactions shape biodiversity. The southeastern margin of the Tibetan Plateau, particularly the western Hengduan Mountains, is a key region where active strike-slip faulting, distinct topography, and exceptional plant diversity coincide. While previous work has established broad patterns of uplift, erosion, and biodiversity, important questions remain concerning high-resolution records of short-term erosion, the influence of paleoclimate, and the geomorphic and ecological implications of strike-slip fault related deformation. This thesis addresses these questions through three chapters. First, new cosmogenic nuclide-derived erosion rates are reported from tributaries of the Salween, Mekong, and Yangtze rivers, which flow closely and in parallel across areas of high relief. Topography is further characterized using trunk- and tributary-averaged channel steepness. The results show that precipitation gradients modify topography, while both local and regional tectonics exert strong controls on erosion. Specifically, the exceptionally high erosion rates and steep channels near the Meili Mountains can be explained by a restraining stepover, whereas the broader regional pattern of erosion is consistent with indentation from India and Burma. Second, this thesis examines whether paleoclimate variability influences the relationship between cosmogenic erosion rates and channel steepness. One-dimensional profile modeling demonstrates that the ratio of precipitation amplitude to mean precipitation (Pa / Pm) is the primary control on oscillations in instantaneous and cosmogenic erosion rates, as well as precipitation-modified channel steepness. These results imply that in regions with large Pa / Pm values, climatic cycles disturb the relationship between erosion rates and channel steepness, whereas in the Three Rivers Region, where Pa / Pm is small, paleoclimate corrections are not required. Third, this thesis investigates how strike-slip fault-related structures influence landscape and habitat dynamics. Simulations with the Divide and Capture landscape evolution model (DAC) show that landscape response depends jointly on kinematic parameters and structural geometry, including slip rates, the initial fault-river angles, and structural width. When coupled with an orographic precipitation model, these fault-related structures exert strong control on topography, precipitation patterns, and habitat dynamics, accounting for frequent river captures, transient basin formation, and fluctuating habitat fragmentation. Together, these findings highlight the interactions among tectonics, climate, landscape and biodiversity in the western Hengduan Mountains. By combining cosmogenic data, numerical modeling, and geomorphic-ecological perspectives, this thesis contributes insights into the processes shaping one of the world’s most dynamic and biodiverse mountain regions.