Soil Total Nitrogen Mediated the Impact of Climatic Factors on Urban Soil Organic Matter Under Different Land Uses

The Xiong'an New Area (XNA) is a nationally designated region characterized by prominent emerging trends, intensive human activities, and rapid urbanization. However there needs to be more clarity regarding the comprehensive investigation of land use management impact and climate factors on soil properties within this area. We collected 544 composite topsoil samples from this region to investigate the relationship between soil properties and land use types. We analyzed how climate factors affects soil properties using geostatistics, ArcGIS, Mantel test, structural equation modeling, and random forest regression. We observed moderate levels of total nitrogen (TN), soil organic matter (SOM), total phosphorus (TP), and total potassium (TK) content, characterized by a strong overall trend in TP and TK. Furthermore, the spatial distribution of soil water content (SWC), salt salinity (SS), and electrical conductivity (EC) displayed a patchy pattern, with high-value regions predominantly concentrated in the southern, western, and northwestern areas. Path modeling unveiled the substantial influence of mean annual relative humidity (MARH) and mean annual temperature (MAT) on SOM in farmlands and park-green lands. In contrast, mean annual precipitation (MAP), MAT, and MARH exerted notable total effects on SOM in woodlands. Significant variations in soil physicochemical characteristics were observed among different land use types, particularly notable in farmlands and inland tidal flats compared to woodlands and park-green lands. These findings highlight the complex interplay between climatic factors and urban soil organic matter levels across diverse land uses, influenced by soil total nitrogen levels.