气候、植被及土壤因素交互作用对宁夏土壤有机碳的影响机制

基于宁夏全区121个土壤剖面样点，研究不同深度(0—30、30—80、80—120cm)土壤有机碳的空间分布特征，通过相关性、方差分解和构建结构方程模型，分析气候、植被和土壤因素对宁夏不同深度土壤有机碳的影响及其作用途径。结果表明：(1)宁夏不同深度土壤有机碳含量均呈现中间低南北高的空间分布趋势，0—120cm剖面土壤有机碳含量随着土壤深度的增加而降低，土壤有机碳含量均值为5.49g/kg,变异系数达90.71%,含量偏低且空间异质性强。(2)各土层土壤有机碳与年均气温、干燥度、碳酸钙、pH均呈现极显著的负相关性(P<0.01),与年均降水量、相对湿度、植被净初级生产力、全氮、全磷、全钾、钙离子、阳离子交换量、粘粒含量均呈现极显著的正相关性(P<0.01)。(3)各因素对不同土层土壤有机碳的作用方式和影响程度有差异。土壤全氮、全磷、碳酸钙、阳离子交换量均能直接影响土壤有机碳，年均气温和植被净初级生产力对土壤有机碳的直接影响效应不显著，主要通过土壤属性间接影响土壤有机碳含量。随着土层深度的增加，气候和植被因素作用明显减弱，土壤因素作用增强并成为主要影响因素。该结果有助于宁夏土...

Interaction mechanism of climate, vegetation and soil factors on soil organic carbon at different soil depths in Ningxia

Based on 121 soil profile sample points in Ningxia, the spatial distribution characteristics of soil organic carbon (SOC) and the effects of climate, vegetation and soil factors on soil organic carbon at different depths (0-30 cm, 30-80 cm, 80-120 cm) were studied through correlation, variance partitioning analysis and structural equation modeling. Results showed that:(1) The SOC content presented a spatial distribution trend of lower in the middle and higher in the north and south at different soil depths in Ningxia. In 0-120 cm section, the SOC content decreased with the increase of soil depth, with an average value of 5.49 g/kg and a coefficient of variation of 90.71% indicating low SOC content and strong spatial heterogeneity. (2) Soil organic carbon in all soil layers was negatively correlated with mean annual temperature, drought index, calcium carbonate, pH, and positively correlated with mean annual precipitation, relative humidity, net primary productivity of vegetation, total nitrogen, total phosphorus, total potassium, calcium ion, cation exchange capacity, and clay content. (4) The action mode and degree of each factor on SOC in different soil layers were different. Soil total nitrogen, total phosphorus, calcium carbonate, and cation exchange capacity could directly affect soil organic carbon. The direct effect of mean annual temperature and net primary productivity of vegetation on soil organic carbon was not significant, and the indirect effect on soil organic carbon was mainly through soil properties. With the increase of soil depth, the effects of climate and vegetation were weakened, while the effects of soil were strengthened and became the main influencing factors. The results are helpful for the index screening of prediction and assessment of soil organic carbon content in Ningxia, and provide a theoretical basis for the relationship between regional ecosystem environmental factors and soil carbon cycle.