Spatial distribution and influencing factors of topsoil organic carbon density in Fujian Province, China

Abstract

为准确估算福建省表层土壤有机碳密度，确定其空间分布和影响因素，基于2016—2019年采集的4 350个表层土壤样本，利用地统计学方法与ArcGIS技术分析土壤有机碳密度空间分布，并通过随机森林模型分析影响土壤有机碳密度的重要因素。结果表明：福建省表层土壤有机碳密度范围为0.03~14.68 kg·m^-2，平均值为4.06 kg·m^-2。全省表层土壤有机碳密度在空间上聚集分布，具有中等程度空间自相关性，空间变异主要由结构性因素主导，呈现自南向北、从沿海向内陆山地逐渐升高的空间分布格局。降雨量、海拔、土壤质地和土壤pH是影响有机碳储量的主要因素，地貌类型、土壤类型和作物类型影响相对较弱，且随着化肥（磷肥和钾肥）施用量的增加，表层土壤有机碳密度显著降低。研究表明，福建省表层土壤有机碳密度不高，空间分布聚集，自然气候变化、地形因子和人类活动都会影响土壤有机碳密度，其中降雨量、海拔、土壤质地和土壤pH为主导因素。

This study aimed to accurately estimate the organic carbon density of topsoil in Fujian Province and determine the spatial distribution and influencing factors of topsoil organic carbon density. Using 4 350 topsoil samples collected from 2016 to 2019, the spatial distribution of organic carbon density was analyzed by geostatistics and ArcGIS, and the influencing factors of soil organic carbon density were analyzed using a random forest model. The topsoil organic carbon density was 4.06 kg•m^-2(range, 0.03-14.68 kg•m^-2). The topsoil organic carbon density was spatially concentrated and distributed with a moderate degree of spatial autocorrelation. The spatial variation was mainly dominated by structural factors, showing a spatial distribution pattern that gradually increased from south to north, from coastal to mountainous areas. Precipitation, altitude, soil texture, and pH were the main factors affecting the organic carbon density. Landform type, soil type, and crop type exerted relatively weak effects, and the soil organic carbon density reduced significantly with the increase in chemical fertilizer(phosphorus and potassium) application. These results showed that the topsoil organic carbon density in Fujian Province is not high, and the spatial distribution is concentrated. Natural climate change, terrain factors, and human activities all affect the soil organic carbon storage level, with precipitation, altitude, soil texture, and pH being the dominant influencing factors.