Evaluation of Soil Quality in Five Ages of Chinese Fir Plantations in Subtropical China Based on a Structural Equation Model

Soil quality evaluation provides necessary and fundamental data information for understanding the current situation of soils promoting sustainable use land resources. In this study, soil was assessed by developing a structural equation model (SEM) in five aged Chinese fir plantations, located same type, with similar site conditions, Subtropical China. A total 150 samples were taken from stands forests: 8-year-old young forests (stand I), 14-year-old middle-aged II), 20-year-old near-mature III), 26-year-old mature VI), 33-year-old over-mature V). Fifteen indicators, including bulk density (BD), capillary porosity (CP), (TCP), water holding capacity (WHC), organic matter (SOM), nitrogen (TN), available (AN), phosphorus (AP), potassium (AK), pH, acid phosphatase (ACP), invertase (INV), urease (URE), catalase (CAT), measured. The SEM used to determine weight each indicator, index (SQI) estimated plantations. Results showed that physical such as BD, CP, TCP, WHC, chemical SOM, TN, AN, significantly degraded stand II groups compared I groups, but recovered III groups. However, enzyme activity biological indicators had different patterns changes properties. calculated SQI studied ranged 0.4084 0.7298, which higher V lower (middle-aged stand) than other four (p < 0.05). analysis ACP most important affecting physical, chemical, properties study area. This provided an innovative scientific approach estimating theoretical basis practical application management forest ecosystems.