Spatial distribution of soil nutrients after the establishment of sand-fixing shrubs on sand dune

Caragana microphylla was the dominant plant species to be used to control desertification in semi-arid Horqin Sandy Land, China. To elucidate the cover effect of Caragana microphylla planted for 25 years on spatial distribution of soil nutrients including C, N, P and K, soil samples were taken from four soil depths (0-5 cm, 5-10 cm, 10-20 cm, 20-40 cm) and three slope positions (windward slope, top slope, and leeward slope). Soil nutrients under shrubs (US) and between shrubs (BS) were compared to investigate the enrichment effect of plantation. The results showed that soil nutrients except total K were significantly higher in soil depths of 0-5 cm than in deeper soil layers. Significant differences were found in the concentrations of total organic C, total N, total P, and total K at different slopes. The levels of total organic C and total N were higher in US than in BS (P less than 0.05), but soil pH was lower (P less than 0.01). The establishment of Caragana microphylla increased the accumulation of soil nutrients, and played an important role in restoring sand dune ecosystems.