Seasonal fluctuations of marsh wetlands in the headwaters of the Brahmaputra, Ganges, and Indus Rivers, Tibetan Plateau based on the adapted LandTrendr model

Marsh wetlands present a rich variety of ecosystem goods and services, including important carbon sinks, of great significance to changes in the global environment. However, seasonal responses of marsh wetlands remain understudied and poorly understood. Therefore, this study adapted the Landsat-based Detection of Trends in Disturbance and Recovery (LandTrendr) model using field and Landsat data during 1990–2017 to identify the seasonal and spatial variations in marsh wetlands in the headwaters of the Brahmaputra, Ganges, and Indus Rivers (HBGIR) and analyze the drivers of their spatiotemporal changes. The spatiotemporal change in the marsh wetlands was divided into the three stages of expansion (1990–1998), retreat (1998–2004), and stability (2004–2017). The marsh wetland area showed an increasing trend before 1998 and a stable and slightly increasing trend after 2004. The expansion area of the marsh wetlands was located in the reserves of Shiquanhe and Manasarovar and their surrounding areas. The marsh wetlands were subjected to the largest expansion in summer (114.45 km2), followed by spring (80.45 km2). The expansion of the marsh wetlands in summer was mainly driven by snow depth and temperature, with the strongest interaction factor of 0.6 between them. However, the retreat of the marsh wetlands was driven by the expansion of construction and cultivated lands in the HBGIR. Finally, the LandTrendr model modified in this study was useful for improving the change-detection accuracy of the marsh wetlands. This study provides an important theoretical basis for wetland protection and management for the Tibetan Plateau.