Abstract:
Objective As the principal component of terrestrial soil carbon pools, soil organic matter (SOM) plays a pivotal regulatory role in global carbon cycling and soil fertility, directly underpinning national food security. Qiqihar, widely recognized as the "Hometown of Black Soil," is characterized by its distinct accumulation of organic matter. To further elucidate the drivers of its spatial heterogeneity, this study employs accurate, intuitive, and efficient analytical methodologies to map the spatial distribution patterns of SOM across the region. Furthermore, it quantitatively investigates the coupled driving mechanisms of natural and anthropogenic factors, thereby revealing the stability of the black soil carbon pool and its associated environmental implications.
Methods Based on test data from a surface substrate survey of the chernozem in the Qiqihar region of the Songnen Plain, this study employed a Geographically Weighted Regression (GWR) model to predict and analyze the soil organic matter content. The analysis focused on the plain areas of eight counties in Qiqihar—Yi’an, Fuyu, Baiquan, Keshan, Kedong, Nehe, Longjiang, and Gannan—across three depth layers: shallow (0~100 cm), middle (100~200 cm), and deep (200~300 cm).
Results The analysis revealed that the GWR model predictions for organic matter content at different depths were largely consistent with the measured values. Both showed a spatial pattern of higher concentrations in the northeast and lower concentrations in the southwest. For the shallow layer, the average GWR-simulated soil organic matter content was 26.50 g/kg, compared to a measured average of 27.75 g/kg. In the middle layer, the GWR-simulated average was 10.07 g/kg, versus a measured average of 10.05 g/kg. For the deep layer, the GWR-simulated average was 6.48 g/kg, closely matching the measured average of 6.47 g/kg.
Conclusions The results indicate that soil physicochemical properties, including K2O, total phosphorus, and total nitrogen, as well as environmental factors such as mean annual temperature, mean annual precipitation, and elevation, all exert varying degrees of influence on the soil organic matter content at different depths.
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