The spatial pattern of soil water content (SWC) determines the success of vegetation restoration in semi- and arid regions. The Qilian Mountains in China are in a semi-arid area where decades of environmental degradation prompted large-scale restoration efforts with a native constructive species Picea crassifolia. However, the relationships between SWC and landcover are not clear in this area, hindering woodland restoration. In this study, we determined spatial distribution and characteristics of SWC in the Qilian Mountains in four main types of landcover. Our results revealed that 1. SWC decreased in the order of natural forest, brushland, grassland, planted forest, and mixed forest, but it was significantly different only in natural forest (p<0.05); 2. planted forest exhibited a lower SWC at young ages (less than 50 a) than natural forest, brushland or grassland, and the ecohydrological effect of afforestation exhibited hysteresis at long time scales; 3. a variogram analysis and Kriging interception of the spatial pattern of SWC showed that shrubland and grassland exhibited superior adaptability to local SWC compared with afforestation. The differences in SWC among various landcover types indicated that strengthening the maintenance and protection of natural forests is more important for restoration efforts than afforestation; furthermore, in semi-arid regions, shrubs and grasses are more suitable for use in ecological restoration than forest plantations.

Afforestation has been implemented on a large scale in the Loess Plateau of China since 1999. This paper aimed to judge the influence of plantation tree types on soil aggregate stability and carbon stocks. The results showed that : (1)the content of soil organic matter and macro-aggregates, the water stability of aggregates were significantly higher in P. tabuliformis plantation compared with R. pseudoacacia and M. pumila plantations, conversely, the content of soil calcium carbonate in P. tabuliformis plantation was the lowest; (2) the content of soil organic matter and organic carbon density were significantly negatively correlated with soil depth, while soil carbonate calcium and in-organic carbon density fluctuated with the increasing of soil depth; (3) compared with topsoil, subsoil was important carbon sink because there were more in-organic carbon; (4) Aggregate organic carbon increased while inorganic carbon decreased with the increasing of aggregate size respectively. We concluded that: (1) R. pseudoacacia played a more important role in soil carbon sequestration compared with P. tabuliformis; while P. tabuliformis was more beneficial to improve soil organic matter and soil structure; (2) subsoil and in-organic carbon were important carbon sinks compared with topsoil and organic carbon; (3) the bigger water stable aggregates having the higher content of soil organic matter and the lower carbonate calcium.