Rapid changes of soil properties following Caragana korshinski plantations in the hilly-gully Loess Plateau

Abstract

In the semi-arid area of the Loess Plateau, Caragana korshinski, a leguminous shrub, is the dominant plant species widely used in vegetation rehabilitation programs. We collected soil samples in 8- and 18-year-old C. korshinski plantations to assess the effects of the shrub on the physical and chemical properties of the soil as well as enzyme activities. Soil samples were taken from two depths (0 20 and 20 40 cm) under the shrub canopy between shrubs. Results showed that shrub rehabilitation and development enhanced accumulation of organic C and total N. Carbon and nitrogen concentrations increased significantly with plantation age and had increased by 15.3 20.5-fold and 11.1 13.6-fold at 0 20 cm depth at the 18-year-old plantation compared with farmland soil. It was found that C. korshinski contributed significant enrichment of C and N contents under their canopies compared with farmland. The content of water stable aggregates in 18-year-old shrub land soil is higher than the 8-year-old shrub land, and the big aggregates (>5 mm) increased for the most part, by 67.4% and 59.0% in different layers, respectively. The contents of aggregates of over 0.25 mm in two shrub land soils in the upper layer (0 20 cm) increased by 4.6% and 14.1% compared with farmland. It indicates that C. korshinski afforestation can increase the content of aggregates. C. korshinski plantation can accelerate the increase of soil urea activity and invertase activity, respectively, especially in the upper layer.