Resource islands and its roles in the thicketization of grasslands and thicketization-grasslands

In this paper the mechanisms of resource island formation in semiarid grasslands is reviewed.Thicketization of grassland is considered a deformation of a resource island under perennial grass tussock in conjunction with the formation of resource island under shrub-thicket.In terms of source-sink relationship in soil resources,the resource island under shrub patches acts as a sink for soil resources in the thicketization of grasslands.The development of a shrub resource island is firmly related to thicketization of grasslands,and determines the basic ecosystem function,especially the primary productivity of thicketization-grasslands.Finally,for research on the thicketization of steppe and thicketization-steppe in Xi-li River Basin,Inner Mongolia,the significance of the related theory on resource islands is discussed.