Comprehensive Evaluation of Soil Quality under Different Vegetation Types in the Green Heart Area of the Changsha-Zhuzhou-Xiangtan City Cluster
The effects of different vegetation types on soil quality in the Green Heart Area of the Changsha-Zhuzhou-Xiangtan City Cluster were evaluated to provide a reference for selecting suitable afforestation species and improving forest soil quality. Seven vegetation types (mixed forest, broad-leaved forest, coniferous forest, economic forest, shrub forest, grassland, and abandoned cropland) with similar site conditions were studied. Eleven soil physicochemical indicators were measured, and soil quality was assessed using principal component analysis (PCA), Pearson correlation, total data set (TDS), minimum data set (MDS), and entropy-weighted TOPSIS methods. Results showed no significant differences in soil water content, soil bulk density, and C:N ratio among vegetation types, while significant differences were found in total porosity, capillary porosity, saturated water content, field water holding capacity, total carbon, total nitrogen, available potassium, and available phosphorus. Compared with abandoned cropland, soil water content, total porosity, field water holding capacity, saturated water content, total carbon, total nitrogen, available potassium, and available phosphorus were significantly higher, and soil bulk density was significantly lower. Mixed forest soil exhibited the highest values for field water holding capacity, total porosity, saturated water content, total nitrogen, total carbon, available potassium, and available phosphorus. Correlation analysis revealed that soil bulk density was extremely significantly negatively correlated with soil water content, total porosity, and saturated water content, and significantly negatively correlated with field water holding capacity, total carbon, and total nitrogen. Soil capillary porosity, field water holding capacity, total porosity, and saturated water content were extremely significantly positively correlated with soil nutrients, while soil bulk density showed varying degrees of negative correlation with soil chemical nutrients. Soil chemical properties and stoichiometric ratios showed varying degrees of significant positive correlation. The order of soil quality under different vegetation types was mixed forest > broad-leaved forest > shrub forest > economic forest > grassland > coniferous forest > abandoned cropland. Mixed forest soil quality was the best and significantly higher than other vegetation types, with significant differences among vegetation types. Mixed forest soil quality was clearly superior. In vegetation restoration and plantation establishment in the Green Heart Area, the principle of matching tree species to site conditions should be followed, with a focus on mixed forests to improve overall soil quality and enhance ecological benefits of artificial vegetation restoration.