Understanding regional spatial pattern of soil organic carbon density (SOCD) and its potential influencing factors in cropland is of paramount importance when evaluating soil quality and assess the carbon sequestration potential. However, little information is available regarding the regional SOCD for the plough layer of the cropland soils with high‐density sampling sites. In this context, 14,058 soil samples were collected at a regional scale (21 × 10⁴ km²) to investigate the spatial variation in SOCD and to identify the dominant factors influencing this variation using classical statistics, principal component analysis (PCA), residual maximum likelihood (REML), and geostatistical methods, such as semivariogram and ordinary kriging methods. The results indicated that soil organic carbon (SOC) and SOCD both demonstrated moderate variability ranging from 2.61 to 35.67 g kg⁻¹ and 2.61 to 35.67 kg C m⁻², respectively. Geostatistical analysis showed that the nugget‐to‐sill ratios for SOC and SOCD were 0.59 and 0.61, respectively, which demonstrated moderate spatial dependence. The PCA and a minimum data set method identified that organic nitrogen fertilizer, accumulated temperature ≥ 0°C, rice straw incorporation, precipitation, and soil pH were the major factors affecting the spatial variability in SOCD. The REML analysis showed that geomorphologic features, soil types, and irrigation conditions also exerted substantial influence on SOC and SOCD. This study provided reliable estimates of spatial variation in SOCD and thus is helpful in the formulation of strategic sustainable SOC management and regional policy decision making.

中文翻译：

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土壤有机碳密度的区域格局及其对农田耕层的影响

在评估土壤质量和评估固碳潜力时，了解农田土壤有机碳密度（SOCD）及其潜在影响因素的区域空间格局至关重要。但是，关于具有高密度采样点的农田土壤耕层的区域SOCD的信息很少。在这种情况下，以区域规模（21×10 ⁴  km ²），以调查SOCD中的空间变化，并使用经典统计，主成分分析（PCA），剩余最大似然（REML）和地统计方法（例如半变异函数和普通克里金法）来确定影响该变化的主要因素。结果表明，土壤有机碳（SOC）和SOCD均表现出中等的变异性，范围从2.61至35.67 g kg ^-1和2.61至35.67 kg C m ^-2， 分别。地统计分析表明，SOC和SOCD的金块比分别为0.59和0.61，表明其具有中等的空间依赖性。PCA和最小数据集方法确定，有机氮肥，累积温度≥0°C，稻草掺入，降水和土壤pH值是影响SOCD空间变异性的主要因素。REML分析表明，地貌特征，土壤类型和灌溉条件也对SOC和SOCD产生了重大影响。这项研究为SOCD中的空间变化提供了可靠的估计，因此有助于制定战略性可持续SOC管理和区域政策决策。