Elevation-Dependent Driving Mechanisms of Alpine Swamp Wetland Dynamics: A Case Study of the Shule River Basin on the Northeastern Edge of the Qinghai–Tibet Plateau

Alpine wetland ecosystems play a vital role in water conservation, runoff regulation, biodiversity preservation, and carbon sequestration in watersheds. Climate warming has led to pronounced spatiotemporal distribution heterogeneity in alpine swamp wetlands. This is particularly critical for arid inland river basins, whose runoff is largely replenished by alpine ecosystems. Because alpine wetlands are a core component of these systems, it is both scientifically and practically imperative to systematically analyze their change characteristics and underlying driving mechanisms. This study used long-term wetland distribution data from 1987 to 2021 in the alpine mountainous areas of the Shule River basin (China), integrated meteorological, topographic, and permafrost factors, and employed Geodetector and Pearson correlation analysis to separately identify the dominant drivers of alpine swamp wetlands (swamp meadows and marsh wetlands) along elevation gradients, and to quantify the relative contributions of climatic, topographic, cryospheric, and anthropogenic factors to the evolution of swamp wetlands in the study area. The results showed that swamp meadows were mainly distributed in permafrost regions at elevations of 3700~4300 m in the source area of the Shule River‘s main stream. Their distribution was primarily influenced by temperature, as well as other factors such as permafrost, with explanatory power q-values ranging from 0.47 to 0.6. Meanwhile, the drivers of dynamic changes in swamp meadows varied distinctly with elevation. Below 3700 m, the expansion of swamp meadows was more influenced by temperature, with a correlation coefficient of about 0.4. In the 3700~4000 m elevation zone, precipitation became the dominant factor, with a correlation coefficient of up to 0.6. Above 4000 m, swamp meadows exhibited a relatively high negative correlation with low permafrost temperatures, with a correlation coefficient of up to 0.48, and an obvious lag period was also evident. Driven by topography and geomorphology, marsh wetlands were mainly concentrated on both banks of the main channel in the source area of the Dang River at elevations of 2800~3200 m. Their rapid expansion was mainly driven by increased growing-season precipitation in the study area, with a correlation coefficient close to 0.5, and showed a significant negative correlation with glacier area. These results could inform decisions on protecting wetlands in alpine mountainous areas of arid inland river basins.