Effects of Growth Stage and Topography Factors on Soil Physicochemical Properties of E. urophylla × E. grandis Plantation

Purpose: The main purpose of this study is to analyze the consequent changes in soil physicochemical properties under a chronosequence Eucalyptus plantation in the southern Sichuan Basin, China. Methods: : In order to evaluate the changes in soil bulk-density, soil porosity, water holding capacity of soil, and soil nutrient availability, a chronosequence of Eucalyptus plantation (young forest (YF), immature forest (IF), near-mature forest (NF), mature forest (MF), and over-mature forest (OF)) were selected. In addition to soil physicochemical properties, the soil quality index has also been evaluated in our study. Results: : The results revealed that soil bulk density decreased with increasing plantation age. Whereas, the total pores in soil, soil capillary porosity, and saturated water holding capacity increased. The mature and over-mature stands exhibited significantly higher values for these physical parameters. In contrast, chemical properties i.e. soil organic matter (SOM), available nitrogen (AN), and available phosphorus (AP), showed varied responses. SOM content peaked at the near-mature stage before declining, while AN and AP fluctuated across different stand ages, indicating complex nutrient dynamics in response to plantation age. A superior soil quality of the immature and near-mature stands compared with other age groups were determined through soil quality index (SQI) among different stand ages. Conclusion: This study provides insights to the significant influence of chronosequence of Eucalyptus plantation on the physical and chemical properties of soil, with long-term potential effects on soil structure enhancement and challenges posing to nutrient retention. These findings provide intuitions for sustainable forest management practices for eucalyptus plantation.