Effects Of Mowing And Grazing On Mineral Level In The Soil-Forage-Sheep System From Hulunbuir Grassland

Hulunbuir grassland is a world-famous grassland and has always been highly valued and concerned at home and abroad.Scholars have conducted research on it from production,ecology,life and many other aspects.In our study,the mineral element was taken as the entry point to explore the effect of mowing and grazing(including rest grazing)on the soil-forage-sheep system from Hulunbuir grassland.In order to provide a theoretical basis for the healthy development of Hulunbuir grassland husbandry,the distribution characteristics of mineral elements,utilization efficiency of forage and sheep and the mechanisms affecting minerals changes were comprehensively analyzed by combined field surveys and fixed-point tests.The main conclusions were shown as follows:1.The mineral levels had great differences in soil and plants on Hulunbuir grassland,and the concentration of mineral elements in both soil and plants showed moderate variations.The mineral levels in different plant species and the ability of plants absorbing mineral elements from soil were both different.The supply quantity of mineral elements in plants was different with the required amount of livestock,and some elements maybe not satisfy the nutritional needs of livestock.The mineral levels in plants on grazing grassland were higher than that on mowing grassland.2.On the meadow steppe,the concentration of Mg,Mn and Zn in soil gradually decreased with the growing season going on,while the content of Ca remained stable.The absorption efficiency of mineral elements of Leymus chinensis and Bromus inermis was different and fluctuated with the growing season.The distribution and transfer efficiency of mineral in roots,stems and leaves of plants were all dynamic variation.The concentration of mineral elements in plant changed with seasonal variation,and maintaining a proper proportion of high quality forbs on grassland can improve the mineral levels in grassland vegetation.During the grass growing season,the concentration of Ca in blood and Zn in wool of sheep was stable,while the other elements in blood and wool all changed in different degrees with grazing time going on.3.There was little effect of mowing and grazing on soil pH,bulk density and water content,the total amount and available concentration of mineral elements in soil during a short period.However,both mowing and grazing had changed the aboveground biomass and community structure of grassland,and increased the mineral levels in grassland vegetation.The changes of mineral elements in grassland vegetation were positively correlated with the proportion of forbs and the stems/leaves ratio of Bromus inermis,while negatively correlated with the aboveground biomass and the proportion of Leymus chinensis.Under barn feeding conditions with mowed forage,the utilization rates of mineral elements of sheep were maintained in a stable range,while in the condition of grazing,the environment and vegetation were more complicated,which lead to a large variation of utilization rates of mineral elements of sheep.4.Different grazing treatments had no significant effect on soil physicochemical properties and mineral elements during a short period,while had a significant effect on community structure of grassland and the stem/leaf ratio of dominant grass,which was related to selective feeding of sheep at each stage.The variation tendencies of mineral elements of forage of different grazing treatments were similar,but the impacts on mineral content of each grazing treatments were different at each stage.The amount of elements ingested by sheep was largest in continuous grazing,while the efficiency of elements ingested by sheep was highest if had a rest during the second grazing stage.