Dynamic Analysis of the Soil Seed Bank for Grassland in a Typical Prairie on the Loess Plateau

Field survey and laboratory experiment were conducted to study the characteristics of soil seed bank for the grassland in a typical prairie on the Loess Plateau,such as species composition,density,spatial and temporal pattern distribution,and diversity.Results showed that there were 37 species in the seed bank,which belongs to 11 families.For the species of seed bank,Gramineae,Compositea,Labiatae,Leguminosae,and Panunculaceae were dominant.From green up stage to withering stage,the percentage of Leguminosae,Gramineae,and Violaceae decreased and however,the percentage of Compositea and Labiatae increased greatly.Density of soil seed bank increased significantly.For the vertical distribution,the number of seeds took on a decreasing trend with soil depth increasing.In terms of the level distribution of soil seed bank,landforms were in the descendant order of fenced grassland and grazed grassland;lunar slope and solar slope;and top slope,middle slope,and bottom slope.Results from the study indicated that the Margalef and the Shannon—Wiener diversity indexes of soil seed bank were higher in the enclosed grassland,and Pielou evenness index was higher in the grazed grassland.They all decreased from green up stage to withering stage.