Shrub facilitation of desert land restoration in the Horqin Sand Land of Inner Mongolia

To understand the status and roles of shrubs in recovery processes of desertified land in the semi-arid areas of China, we investigated the effects of shrub canopy on soil properties, organic litter, seed bank and understory herbaceous community properties in the Horqin Sand Land, Mongolia. The results showed that in shifting sand dunes, content of very fine sand, silt and clay, organic matter, total N and P, available P and soil moisture at 0–20 cm depth was higher under remnant shrub canopies of Caragana microphylla and Salix gordejevii than in open space. Soil seed density was nearly 12 times higher under Artemisia halodendron canopy than in open space. The herbaceous perennial Pennisetum centrasiaticum, usually restricted to fixed sand dunes, not only survived under shrub canopy in shifting sand dunes, but also had higher plant densities, plant height, cover and aboveground biomass. After fencing shifting sand dunes and establishing shrub plantings, fine soil particles, soil nutrients, plant species richness, vegetation cover and aboveground biomass increased gradually both under shrub canopy and in open spaces with increasing enclosure or plantation age, but the speed of restoration processes was significantly higher under canopy compared to open spaces. These results suggest that shrubs created significant “islands of fertility” and had an important role in maintaining or augmenting herbaceous species richness in shifting sand dunes, and could improve soil properties and facilitate vegetation recovery for controlling desertification processes.