Abstract:
Objective The Northern Songnen Plain, recognized as China's primary black soil resource distribution area and a crucial commercial grain production base, was systematically investigated to characterize the spatial distribution patterns and driving factors of topsoil soil organic carbon density(SOCD, 0~20 cm depth). This study provides critical datasets to advance regional soil carbon cycling research, with direct implications for achieving China's "Dual Carbon Goals" and promoting the region’s agricultural economic sustainability.
Methods This study focuses on Wudalianchi City and Nenjiang City as representative study areas. Utilizing 1174 soil samples collected through field surveys (2022—2023), the density, stock, and spatial distribution characteristics of topsoil organic carbon were systematically quantified using geostatistics and ArcGIS analysis techniques. Advanced statistical approaches, integrating Pearson's correlation analysis with random forest regression modeling were implemented to elucidate the correlation and relative importance of driving factors.
Results (1) The 2023 SOCD in the study area ranged from 6.00 kg/m2 to 9.00 kg/m2 (mean = 6.32 kg/m2), yielding a total soil organic carbon stock(SOCR) of 145.02 Tg; (2) Spatial analysis revealed a west−to−east increasing gradient with moderate positive autocorrelation (Moran's I = 0.228). The optimal interpolation was achieved using an exponential semi variogram model, with structural factors dominating spatial heterogeneity; (3) Significant positive correlations were observed between SOCD and mean annual precipitation (r = 0.38), altitude (r = 0.19), soil C/N ratio (r = 0.56) and N/P ratio (r = 0.38), whereas effective accumulated temperature (≥10℃, r = −0.19) exhibited negative association (all P<0.001). (4) Random forest modeling identified mean annual precipitation (38.40% relative importance) and effective accumulated temperature (22.04%) as primary drivers, followed by altitude (17.22%), pH (9.26%), ground substrate configuration (7.23%), and slope (1.32%).
Conclusions The spatial distribution of topsoil organic carbon density in the Northern Songnen Plain demonstrates positive spatial clustering. Terrain attributes, climatic conditions, and soil physicochemical properties are closely linked to SOCD variations. Climatic factors (mean annual precipitation and effective accumulated temperature) emerge as the dominant controlling factors, followed by altitude, whereas pH, ground substrate configuration and slope exert relatively weaker effects.
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