To reveal the characteristics and spatial differentiation mechanisms of soil fertility at different degradation stages of alpine marsh wetlands， 84 plots were selected in this study， including non-degraded， lightly degraded， and moderately degraded wetlands in Qilian Mountain National Park， Qinghai. An improved Nemerow index and principal component analysis were used to evaluate soil fertility， and the geographical detector model was employed to quantify the influence of environmental factors on its spatial heterogeneity. The results showed that soils at all degradation stages were within the fertile level. The comprehensive fertility index was the highest in non-degraded wetlands （2.03）， slightly decreasing in lightly （1.87） and moderately degraded wetlands （1.83）， with total nitrogen being identified as the main limiting factor. As degradation intensified， soil organic matter， cation exchange capacity， total nitrogen， and total phosphorus gradually decreased， whereas total potassium increased. Except for total potassium， all indicators declined with soil depth. Geographical detection revealed that mean annual precipitation （q=0.741）， altitude （q=0.403）， and mean annual temperature （q=0.402） were the dominant factors influencing the spatial differentiation of soil fertility. Among the multi-factor interactions， the combinations of mean annual precipitation and temperature （q=0.897）， and temperature and NDVI （q=0.870） showed the strongest explanatory power for the spatial pattern of soil fertility. These findings provide a theoretical basis for degradation diagnosis and ecological restoration of alpine marsh wetlands.

Alpine marsh wetland  /  Soil fertility  /  Geographic detector  /  Spatial heterogeneity  /  Qilian Mountain National Park