Long-term ecological effects of two artificial forests on soil properties and quality in the eastern Qinghai-Tibet Plateau.

Afforestation is an essential process of ecological restoration, landscape reconstruction, and environmental improvement. While large-scale plantations have restored the fragile ecosystems of the Qinghai-Tibet Plateau, they have also changed local soil characteristics. A 30-year-old typical planted forest on the eastern Qinghai-Tibet Plateau was selected to determine the long-term ecological effects of artificial forests on the soil in this study. Physicochemical soil characteristics at varying soil depths and relative soil parameters, such as element stoichiometry and growing stock, were quantified on the different plantations. This soil quality information was used to construct an MDS-SQI Model. Our findings revealed that soil TN, TK, TP, and AP content was higher than pre-afforestation baseline values, while SOC and pH values were lower. Amounts of soil nutrients SOC, TN, TP, TK, AP, and AK, were positively correlated in the artificial forests. The ratio of soil C/N was higher and ratios C/P and N/P were lower in poplar than the Chinese pine plantation. The soil quality index values calculated from the MDS model were 0.31 and 0.40 for poplar and Chinese pine plantations in the top 30 cm and 0.55 and 0.46 in the 100 cm depth, respectively, which indicated that the two plantations had low-quality soil. LiDAR satellite imagery was used to estimate a growing stock of 7723 m3 and 435 m3 in the poplar and Chinese pine plantations. The results suggest that the artificial forest improves soil properties overall but that different stand forests have discrete effects on the soil environment.