Effect Of Different Rotational Grazing Time On The Plant Population And The Soil Of Desert Steppe

A study was conducted on family ranches in Stipa breviflora desert steppe. Made a comparative research on the plant population, community, physical and chemical characteristics of soil of 8 rotational grazing paddocks which are under the fixed rotating time around the year. The main results were as follows:1. The growth of Stipa breviflora, Cleistogenes songoriea and Convolvulus ammannii which are grazed in later time were better than grazed in early time. But not good for the growth of Allium polyrhizum. The plant cover of breviflora, Cleistogenes songoriea and Convolvulus ammannii which are grown in the districts of grazing in early time were higher than those in the districts of grazed in later time. Grazed in early time lower the plant cover of Allium polyrhizum. The plant cover of Neopallasia pectinata do not have the conspicuous differences among the grazing paddocks. The plant density of breviflora, Cleistogenes songoriea which are grown in the districts of grazed in early time were higher than those in the districts of grazed in later time and the density of Allium polyrhizum was declined conspicuously in the districts of grazing in early time.2. The important values of perennial forage pretend a high superiority in grazing paddocks while the important values of annual forage are low, but the important values of Enneapogon borealis was high in the districts of grazed in early time.3. The aboveground biomass in CK was the highest and the grazing time do not have the conspicuous influences on the aboveground biomass in different grazing paddocks. The results of plant nutrients analysis showed that phosphorous was higher in the district of grazing in early time, crude ash and nitrogen-free extract were lower. Grazing had a big influence on the underground biomass in surface soil layer. But the change rules which is affected by grazing time was not evidence. The underground biomass of grassland plants descend conspicuously in the districts of grazing in early time.4. grazing will affect on the soil moisture of the top soil (0-10cm) and the soil moisture of grazing district in later time was higher. There were not basic rules of the influences of different rotating time to the soil bulk in dissert grassland. The total phosphorous and soil available nitrogen in the district of grazing in later time were higher than those in the district of grazing in early time. The available phosphorous, available potassium and soil organism content were not conspicuously influenced by the grazing time.