Effects of vegetation restoration on surface soil physicochemical properties in the ningnan mountainous area: A case study of the camel forest watershed in the liupan mountain

Background In order to investigate the effects of water conservation forest types, and restoration periods on soil physicochemical properties during the ecological restoration process in the camel forest watershed of liupan mountain area, and to provide theoretical basis and technical support for the construction of water conservation forest. Methods The effects of different typical water conservation forests with restoration periods of 7 and 15, including 7a larch (Larix gmelinii (Rupr.) Kuzen), 15a larch, 7a Chinese red pine (Pinus tabulaeformis Carr.), 15a Chinese red pine, 7a false acacia (Robinia pseudoacacia L), 15a false acacia, and 7a Sea-buckthorn (Hippophae rhamnoides L), on the main physicochemical properties of the soil in the camel forest watershed of liupan mountain area. Results The results showed that：compared to wasteland, the larch and pine patterns significantly increased soil porosity by 35.9% and 15.8%. As restoration periods from 7 to 15 years, the larch and pine patterns significantly reduced the Mean Weight Diameter (MWD) of soil aggregates by 77.9% and 49.4%. Large aggregates with particle size >5 mm in coniferous forest soils were gradually transformed into small aggregates with particle size <0.25 mm, and soil structural stability was gradually reduced. Sea-buckthorn and false acacia significantly increase soil organic matter content to 4.7 and 4.5 times that of wasteland. As restoration periods 7 to 15 years, soil organic matter content under larch and false acacia increases by 31.1% and 35.1%. Soil urease, alkaline phosphatase, and catalase activities increased gradually with the restoration periods. Under false acacia plantations, poorer soil moisture and aeration negatively correlate with surface soil enzyme activities, reduced microbial activity in surface soil. Conclusions Pinus tabulaeformis has the best performance in increasing soil fertility and water and fertilizer retention, and can be used as a suitable plant for planting deep-rooted plants to optimize the local soil ecological environment.