鄂西犟河流域表层土壤有机碳时空变化及其影响因素

目的] 研究土壤有机碳（SOC）在小型丘陵山地集水区的分异规律及其影响因素，为土壤资源的可持续利用以及保护南水北调水源地提供科学依据。方法] 基于数字高程、Landsat 8 OLI影像和2016—2018年实测土壤有机碳等数据，运用相关分析、主成分分析法等研究湖北省十堰市犟河流域表层土壤有机碳含量的时空变化，厘清其影响因子和主导因素。结果] 犟河流域SOC含量整体呈条带状分布的格局，由东北向西南逐渐增加，呈中等强度变异。夏秋两季SOC处于流失状态，而冬季SOC含量明显增加。不同质地SOC的平均含量：石灰性冲积土 > 简育高活性淋溶土 > 不饱和雏形土。不同覆盖下SOC平均含量：农田 > 园地 > 混交林 > 针叶林 > 灌木。土壤SOC含量呈现随地表曲率绝对值增大而增大，随比值植被指数（RVI）和归一化植被指数（NDVI）增加而增加的趋势。结论] 地形因子（地表曲率）是影响犟河流域土壤有机碳的主导因子，植被因子（NDVI和RVI）是次要因子。改变局部小地貌、增加林种、改善水肥管理等措施均可以提高流域土壤有机碳含量。

Temporal and Spatial Variation in Soil Organic Carbon and its Influencing Factors in Jianghe Small Watershed of Western Hubei Province

Objective] The law of soil organic carbon (SOC) differentiation and its influencing factors in small hilly and mountainous catchment areas was studied to provide a scientific basis for the sustainable utilization of soil resources and the protection of water sources of the South-to-North water diversion project.Methods] The spatial and temporal distribution and influencing factors of SOC in the Jianghe watershed, Shiyan City, Hubei Province were analyzed, based on the digital elevation models (DEM), Landsat 8 OLI products, and measured SOC data from 2016 to 2018. These were analyzed using a correlation analysis and principal component analysis methods.Results] Regarding the spatial distribution, the SOC had a banded distribution and the concentration of SOC in northeast of the watershed was smaller than that in the southwest. The variability of the SOC was of a middle intensity. The SOC concentration decreased in summer and autumn, whereas it accumulated in winter. For different soil types, the SOC concentration exhibited the following order: calcaric fluvisols > haplic luvisols > dystric cambisols. For different landcover types, the SOC concentration exhibited the following order: farmland > garden plot > mixed forest > evergreen coniferous forest > deciduous shrubs. The SOC increased along with the absolute value of the earth''s surface curvature and the values of ratio vegetation index (RVI) and normalized difference vegetation index (NDVI).Conclusion] The topographic factor is the main influencing factor of SOC concentrations in the Jianghe watershed, and vegetation factors (RVI and NDVI) were the second principal components for the SOC variation. The SOC concentration can be increased by changing local small landforms, increasing forest species, and improving water and fertilizer management.