Isotope Tracer Study of Soil Erosion in a Typical Sub-watershed in the Eastern Tianshan Mountains, China

Soil erosion represents a critical ecological and environmental challenge on a global scale. In this study, the Baiyang River sub-watershed, located in the eastern Tianshan Mountains of Xinjiang, China, was selected as a representative area for the quantitative analysis of soil erosion. The dual isotope tracer technique, utilizing Cs and Pb, was employed to investigate the distribution patterns of these isotopes within soil profiles and to assess soil erosion dynamics under varying land-use types. This approach aimed to elucidate the influence of different land-use practices on soil erosion rates and nutrient contents to support sustainable land management strategies. The results indicated that the distribution of Cs and Pb followed an exponential pattern in woodland and grassland, whereas in cropland, these isotopes exhibited a relatively uniform distribution. The average soil erosion rate in the study area followed the pattern: cropland (20.39 t ha·yr) > grassland (13.21 t ha·yr) > woodland (1.86 t ha·yr). The contents of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) exhibited the opposite trend, with woodland > grassland > cropland. Furthermore, nutrient loss was lowest in woodland, highlighting its superior capacity to retain nutrients. SOC and TN demonstrated stronger correlations with soil particle size and isotopic composition, whereas phosphorus showed weaker correlations, suggesting that the distribution and transport processes of phosphorus differ significantly from those of carbon and nitrogen. The application of the Cs and Pb dual isotope tracer technique offers a novel approach and valuable data for the quantitative assessment of soil erosion in arid regions, contributing significantly to ecological conservation and sustainable land management.