Response Of Soil Seed Bank To Different Grazing Intensities In The Stipa Breviflora Desert Steppe

In Inner Mongolia Stipa breviflora desert steppe, a randomized complete block design was used with three replication and four stocking rate treatments Control(CK),light stocking rate (LG), moderate stocking rate (MG) and heavy stocking rate (HG)by sheep in a continuously grazed system(June to November).the use of random field sampling and laboratory germination of fixed-point method of combining for the 5 years under different grazing intensities of the fence the grass soil seed bank do a research in 2007 to 2009.Discussion of different grazing intensity under the desert grassland soil seed bank and formation mechanism of the change in mechanism for the restoration of desert grassland vegetation and provide a theoretical basis.The results are as follows:The total density decreased with the grazing intensity increasing.The layer which soil seed bank of all the experimental plots mainly distributed in was 0～10cm,percentage of total density was 65%～90%.The density of soil seed bank decreased gradually in 0～10cm,10～20cm soil layer with the grazing intensity increasing.Density of Perennial decrease along with grazing intensity increasing in various pilot areas.The change of annual and biennial plants is big with the season,mainly in the June and October.The ratio increased in high grazing plots.Small semi～shrubs did not change while the perennial plant is the main species in the persistent seed bank in the pilot area.Species diversity,richness,evenness with increasing grazing intensity decreased,but changes with the seasons is not a certain regularity.