The influence of snow cover dynamics on gross primary productivity of cultivated land in Northeast China

Snow cover is a crucial factor influencing gross primary productivity (GPP), but the various regulatory mechanisms across different geographical zones in Northeast China remain unclear. This study comprehensively analyzed the dynamic changes in snow cover and GPP in Northeast China from HY2001 to HY2020. Specifically, the study area was divided into six subregions to investigate the impact of snow cover on cropland GPP. The results revealed that the snow water equivalent (SWE) decreased in 63 % of the croplands in Northeast China, while the snow cover duration (SCD) increased in 54 % of the croplands. Additionally, delayed snow cover end dates (SCEDs) were observed in 61 % of the croplands, with 74 % showing significant increases in cropland GPP. In terms of cropland types, SCD showed the strongest positive correlation with dry lands, while paddy fields were more sensitive to SCED variations. Geographically, the Changbai Mountain, Sanjiang Plain, and Khingan Ranges exhibited more pronounced GPP changes due to SCED. In contrast, the Liaohe Plain and Western Sand Area were predominantly affected by SWE, while the Songnen Plain showed greater sensitivity to SCD. These findings elucidate the critical role of snow cover in modulating cropland GPP variations across different geographical zones, providing valuable insights into the influence of similar climatic conditions on cropland ecosystems.