How forest types shape soil quality: The evidence from eastern China’s north sub-tropical ecosystems

The factors influencing soil quality might vary across different forest types. However, the impact of root systems on the variations in soil quality might be ignored. This study evaluated the soil quality of bamboo forest (Z), pine forest (S), and oak forest (M) by incorporating the soil physico-chemical properties with the parameters of root morphological traits ( RMT ). The minimum data set ( MDS ) derived from principal component analysis ( PCA ) and Pearson correlation analysis was constructed to select the key soil quality indicators. Additionally, the two models, linear ( SQI-L ) and non-linear ( SQI-NL ), were employed to standardize the indicators in MDS . Soil quality index ( SQI ) was used as a tool to assess the different effects of forest types. The results indicated that the SQI at the three forest types demonstrated a decreasing tendency with increasing soil depth. The SQI in the topsoil (0–20 cm) was the highest in the bamboo forest compared to the other two forest types. In contrast, the SQI in the subsoil (20–50 cm) was significantly higher in the oak forest than that in the bamboo and pine forests. The SQI across the soil profiles (0–50 cm) derived from both the SQI-L model and SQI-NL model at the three forest types was in the following order: oak forest > pine forest > bamboo forest. In the bamboo forest, the relative importance of RV with the 1- to 3-mm diameter class and silt was the highest. RL with the 3- to 4-mm diameter class and SBD were the indicators with the highest relative importance in the pine forest, while the most primary indicators contributing to the changes in SQI were RAD and TK in the oak forest. It is the first time to construct the SQI incorporating the RMT with the soil properties. This study could offer important insights for the assessment of soil quality and the selection of the suitable forest types in maintaining the sustainable forestry management.