[Influencing mechanism of several shrubs and subshrubs on soil fertility in Keerqin sandy land].

Keerqin sandy land is one of serious desertification areas in the semiarid zone of north China, and shrubs are the dominant plant life form and play an important role in the region. The effects of "fertile island" and rhizosphere of several shrubs and subshrubs were studied. The results showed that the concentrations of organic C, total N and total P, and values of electrical conductivity (EC) in the soils under the canopy of shrubs increased by 56%, 51%, 37%, and 51%, respectively, compared with those of the soils in open spaces, but there was no significant difference in pH value between the soils under shrub canopies and in open spaces. Shrub rhizosphere soils had significant higher contents of organic C, total N, and values of EC as well as lower pH value compared to the bulk soils, but there was no significant difference in total P between rhizosphere and bulk soils. There were close relationships between the properties in soils under shrub canopies and the rhizosphere soils, indicating that the development of "fertile island" were favorable to root growth and induced greater amount of rhizodeposition, and vice versa. Soils under Artemisia frigida and Caragada microphylla canopies and rhizospheres had significant higher organic C and total N contents than those of Artemisia halodendron and Salix gordejvii. This results suggested that shrubs were of vital importance for accumulation of nutrients and maintenance of soil fertility in Keerqin sandy land ecosystem.