Abstract:
Objective The aim of this study is to clarify the effects of different forest management measurements on soil aggregate stability and fine roots distribution in Chinese fir (Cunninghamia lanceolata) plantations.
Method The plantation of Chinese fir in Huaying Mountains of East Sichuan was selected, and the untreated plots were used as control to compare and analyze soil aggregate stability and fine roots distribution characteristics after thinning, understory removal, intercropping with Cinnamomum camphora, and litter removal.
Result Among the five forest management measurements in each soil layer, the percentages of > 0.25 mm mechanical-stable aggregates (DR0.25) and water-stable aggregates (WR0.25) were the highest in the thinned forest, and the mean weight diameter (MWD) of dry sieving and wet sieving of each soil layer were also the highest. Compared with the control, the MWD of dry sieving of each soil layer of thinned forest increased significantly (P < 0.05) by 46.76%, 34.63% and 43.78%, respectively, and the MWD of wet sieving of each soil layer of thinned forest increased significantly (P < 0.05) by 45.23%, 70.11% and 77.98%, respectively. The fine root length density (RLD) and the fine root mass density (RMD) of the five forest management measurements in the 0 - 10 cm soil layer were significantly higher than other soil layers (P < 0.05). With the increase of soil depth, the RLD and RMD of the five forest management measurements were significantly decreased (P < 0.05), the RLD and RMD of intercropping with Cinnamomum camphora in the 0 - 10 cm soil layer were the highest. The growth of fine root contributes to the increment of RLD and RMD after thinning and understory removal. The results of correlation analysis showed that the root characteristic factors RLD and RMD under forest management measurements can significantly alter the content of aggregates > 0.25 mm, thereby influencing the stability of soil aggregates.
Conclusion The soil structure of Chinese fir plantations improves effectively, and the aggregate stability of the soil is at its highest after thinning. The development degree of surface fine roots in Chinese fir plantations is higher after intercropping with Cinnamomum camphora and thinning. Therefore, it is recommended that moderate thinning should be given priority in the management of Chinese fir plantation in eastern Sichuan.