Assessing the Influences of Grassland Degradation on Soil Quality Through Different Minimum Data Sets in Southwest China

Establishing a suitable and useful soil quality (SQ) assessment tool is imperative for the accurate evaluation of the effect of environmental changes on SQ. This study constructed four soil quality indexes (SQIs) based on different minimum data sets and weighted additive models to evaluate the influence of grassland degradation on SQ in northwest Guizhou, China. A total of 19 soil properties, including six physical properties, six chemical properties, and seven microbial properties, were measured at soil depths 0–20 cm to construct the SQI_S. Results showed that 18 soil indicators were selected as the potential SQ indicators in the total data set. Based on the principal component analysis, four indicators, soil organic carbon (SOC), mean weight diameter, α-glucosidase, and β-acetylglucosaminidase, were selected in the minimum data set (MDS). However, six indicators, SOC, pH, β-1,4-xylosidase, β-acetylglucosaminidase, Clay, and Bulk Density, were selected for the selective MDS. Despite the notable inter-correlation among the four established SQIs, the SQI derived from the selective MDS and weighted additive model demonstrated heightened sensitivity and capacity for differentiation with respect to grassland degradation because of the high values of F and CV. Grassland degradation significantly reduced the SQ, and the value of SQ under severely degraded grassland was reduced by 51% compared with that under non-degraded grassland. Under the lightly degraded grassland, the reduction in soil physical quality was the primary reason for the total SQ decline, while the reduction in soil microbial and chemical reduction resulted in a significant decline in total SQ under the severely degraded grassland. In conclusion, greater attention should be paid to the SQ reduction resulting from grassland degradation in the study area, and the SQI established by selective MDS and weighted additive model should be used as a suitable and useful SQ assessment tool to evaluate the influence of environmental changes on SQ in Southwest China and other similar areas.