Soil moisture is an important factor that affects terrestrial vegetation ecosystems and biological growth and development, and water deficit is one of the major environmental factors threatening vegetation restoration in the Loess Plateau. To determine the change in the soil water deficit characteristics from farmland to forestland on the Loess Plateau, in this study, we measured the soil water storage and deficit in abandoned grassland, shrubland, pioneer forestland and climax forestland along with vegetation succession. The results showed that the soil water content and the soil water storage with natural vegetation recovery from the abandoned grassland to shrubland and forestland showed a gradual declining trend, while on the contrary, the soil water deficit was increasing during succession, it was more severe in the deep soil than in the shallow soil layers, and the soil water deficit in July and September of the rainy season as well as that the vigorous growing period of plants was more serious than that in May and November, which are in the non-rainy season of the Chinese Loess Plateau. The vegetation types, soil texture and soil depth were the key factors affecting the soil water deficiency status in the process of vegetation succession. The results could have great potential in the sustainable development of forestry and provide a theoretical basis for effective water management and reasonable vegetation restoration in arid and semiarid loess regions.

Secondary forest restoration can alter terrestrial ecosystem processes and potentially impact subsurface carbon dynamics. However, the effects of long-term forest restoration on the soil microbial metabolic activity remain unclear. So, the aim of this study was to explore the response of soil microbial metabolism to forest restoration. Among them, the soil basal respiration (BR), microbial quotient ( qMB), and metabolic quotient ( qCO 2) were studied. This study investigated a natural vegetation restoration sequence approximately ~160 years after farmland abandonment on the central Loess Plateau, China, corresponding to five vegetation restoration stages including farmland, grassland, shrubland, pioneer forests, and climax forests. The results showed that BR and qCO 2 were increased following forest restoration, whereas qMB showed the opposite trend. Forest restoration also increased the activities of β-1,4-glucosidase and β-D-cellobiosidase. Restoration age, litter traits such as nitrogen, cellulose and lignin decomposition rates, dissolved organic carbon contents, fungi and bacteria composition were also important indicators affecting microbial metabolic activities. Long-term forest restoration can change soil microbial community structure, reduce carbon mineralization efficiency, improve soil microbial carbon utilization efficiency, and promote soil organic carbon accumulation.