Assessing alteration of soil quality, degradation, and resistance indices under different land uses through network and factor analysis

Abstract

Over-increasing population and their needs necessitate sustainable use of soil and the other natural resources. In these circumstances land use changes may occur for supplying the food and settlement requirements of the increased population. Therefore, it is needed to evaluate and monitor quality and degradation of the soils. Recently, identification of appropriate soil quality (SQI) and degradation (SDI) indices for assessing sustainable use of soil resources has received increased attention. However, evaluation of quality, degradation, and resistance indices through various new approaches (e.g., network, NA and factor, FA analysis) particularly under different land uses to determine their susceptibility have been rarely conducted. The present study aimed to i) determine SQI, SDI, and resistance (SRI) indices NA and FA approaches under different land uses; ii) investigate the most influential attributes to soil quality (SQ); and iii) to compare SQIs obtained using two different Integrated (IQI) and Nemoro (NQI) Quality Indices, and indicator selection (Minimum Data Set, MDS and Total Data Set, TDS) approaches. Composite soil samples of cropland, forestland, and rangeland were collected and twenty-one soil physicochemical and fertility indicators were measured. MDS was determined using principal component analysis (PCA). The SDI and SRI were computed and compared. Results revealed that the SDI was -13.8% and -4.6% for the cropland and rangeland, respectively indicating inappropriate soil managerial practices in cropland. SRI was 0.01 and 0.41 for the cropland and rangeland, respectively. The lowest SRI values were obtained for critical level of organic matter (CLOM), organic matter (OM), zinc (Zn) and manganese (Mn) showing that these properties, compared with the others, are more sensitive to land use change. Regression equations between SDI and SRI revealed that these substantial relationships show similar trends indicating that these are useful indices to determine SQ and evaluate the effect of land use change and managerial practices. Soils in cropland had a significantly lower deterioration index (DI) (-66.70) than that of the other land uses. SQI in the cropland was the lowest, especially when screened with the NA method. Furthermore, SQI showed the highest correlation with clay and CLOM. The linear SQI value derived from correlation-based-NA method showed greater max/min ratios than that of the FA. Therefore, the NA-based-SQI, as a novel statistical approach, would be more effective than the SQI-derived-FA for evaluating the effects of land use changes and managerial practices. In general, the mentioned technique is a relatively comprehensive approach integrating different influential soil indicators with various weights showing their contributions to soil quality or degradation process.