Effects Of Seasonal Regulation Of Grazing Intensity On Typical Grassland And Livestock Production In Northern China

Grassland is one of the world most widely distributed vegetation types, it playsan important role in carbon and nitrogen cycle and climate regulation. Grassland areaaccounts for about46%in total area of the terrestrial ecosystem. In recent years,with the increasing of the number of population and livestock, most of the grasslandis in a state of overgrazing in our country. Heavy grazing make Grasslanddesertification and desertification. Grazing effect on grassland plant communitycharacteristics, grassland productivity, livestock feed intake, livestock productionperformance and grass nutrition. This study research on grazing intensity (heavygrazing, moderate grazing, rest grazing) and grazing season (spring grazing,summer grazing, autumn grazing) of grassland plant community characteristics,advantages of plant nutrition, soil nutrient, livestock feed intake and livestockproduction performance at Leymus chinensis grassland in north China.According tothe local climate characteristics and grazing management experience. Those are notobviously suitable for the local season grazing and grazing intensity combination areeliminated, An experimental design was used five seasonal regulation of grazingintensity. Five treatments are Respectively SA1(spring grazing prohibition-summerheavy grazing-autumn moderate grazing), SA2(spring grazing prohibition-summermoderate grazing-autumn heavy grazing), SA3(spring heavy grazing-summer heavygrazing-autumn heavy grazing), SA4(spring heavy grazing-summer heavygrazing-autumn moderate grazing), SA5(spring moderate prohibition-summermoderate grazing-autumn moderate grazing). Grazing time of Spring, summer andautumn are respectively from15th June to15th July,16th July to15th Septemberand16th September to15th October. The number of heavy grazing, moderategrazing and rest grazing were9.6,9.6and0.0hm-2.The results show that:1. The vegetation height, coverage and aboveground biomass of SA1and SA2were significant higher than other treatments, the spring grazing prohibition canavoid the grassland be treading, and it also was good for grass turn green, in orderto increase the height, coverage and biomass of the dominant vegetation. The vegetation height, coverage and aboveground biomass of SA3and SA4were notsignificant in spring, summer and autumn, the autumn moderate grazing was notsignificant affect to increase the vegetation height, coverage and abovegroundbiomass significantly after continuous heavy grazing; The summer vegetation heightand aboveground biomass were significant difference between the continuous heavygrazing and continuous moderate grazing, continuous heavy grazing decreased thevegetation height and aboveground biomass31%and17.5%respectively. Grazingintensity was important factor to influencing factors of grassland degradation.2. The Leymus chinensis crude protein content of Leymus chinensis grassland wassignificantly higher than artemisia and carex. The Leymus chinensis, artemisia andcarex crude protein content of SA3and SA4were significant higher than othertreatments, but the artemisia crude fat was significant lower than other treatments,those result show that the crude protein content of dominant plants of grassland wasincreased with enhancing of intensity，and the heavy grazing was harmful to crude fataccumulation.3. The results showed that soil organic matter, total nitrogen, nitrate nitrogenand ammonia nitrogen content decreased with soil depth. Soil organic matter and totalnitrogen content of SA3and SA4in the surface soil (0to10cm) was significantlyless than other treatment. with the increasing of grazing intensity, soil organic matterand total nitrogen content gradually reducing in the soil.Under continuous heavygrazing, soil total nitrogen content is significantly higher than other treatment.Moderate grazing could keep higher soil total N content.Soil total phosphorus,available phosphorus, total potassium and available potassium content differencewas not significant in all kinds of groups. It is not obvious that seasonal grazingregulation effect on soil phosphorus and potassium content.4. Treatment SA2sheep feed intake was significantly higher than that of SA1insummer and autumn, moderating grazing in summer is more advantageous thanautumn moderating grazing to feed sheep. Sheep intaking difference of SA3and SA4was not significant. Rotation of fall heavy grazing and moderating grazing was notsignificant effect on sheep intake. 5. Sheep weight difference of SA3and SA4was not significant, but significantlyless than other processing, sheep individual daily gaining decreased with theincreasing of grazing intensity;SA1and SA2were not significant difference in thesummer and fall.It was not significant that summer and autumn for rotation of heavygrazing and moderating grazing effect on sheep daily gaining.Processing SA3(continuous heavy grazing) weight gain at least in the spring and summer,decreasing of sheep weight is most severe in the autumn.Grassland can not by trampled when spring grazing prohibition which isbeneficial to growth of grass.It can increase the grassland vegetation height,coverage and biomass.Grass lay the good foundation for improving productivity.Thestudy found that spring, summer and autumn moderate grazing promote vegetationgrowth and accumulation of soil nutrients and improving the grassland productivityand livestock production performance. The heavy grazing treatment by concentratingsheeps in one area for a certain period of time in summer can avoid the decline of theoverall quality of grass community.