Effects Of Grazing Intensity On Performance Of Vegetation And Livestock In Typical Steppe

In the Chinese Academy of Agricultural Sciences Institute of grassland in Xilingol typical steppe grazing intensity level test demonstration base,the data of grassland vegetation monitoring and livestock weight gain were mainly selected during June to September in 2014,2015 and 2016.the characteristics of vegetation and livestock's ecological productivity index and grass-livestock transformation efficiency were analyzed under different grazing intensities,including contrast,light grazing,moderate grazing,high grazing and extremely high grazing,corresponding grazing pressures were 0.170.340.510.680(SU·d)/(y·hm2),climate(precipitation)fluctuations effect on interaction between grass-livestock were preliminary analyzed.Results: 1.From the analysis of the plant height of the population,the height gain of L.chinensis showed a linear decreasing trend with the grazing intensity,and the height of Stipa spp(including S.grandis and S.krylovii)showed a single peak trend with the grazing intensity,and there was a peak in the light grazing,there was no significant differences between the light grazing and the forbidden grazing.The increase of the differences would significantly reduce it,and the increase of rainfall was helpful to the maintenance and recovery of the height of four plant species,and the plants of the Stipa spp could tolerate mild grazing,but v they were not tolerant to severe and extremely severe grazing;the height of the plants was prolonged with the grazing years under moderate,severe and severe grazing,compared with the contrast,continue to decrease.2.There was no significant differences in the plant population densities under different grazing intensities(P>0.05).L.chinensis,Stipa spp(S.grandis and S.krylovii),and C.squarrosa were relatively abundant in rainfall(412.8 mm in 2015),and the density was the highest under moderate grazing intensity;With the extension of grazing age,population densities of L.chinensis,Stipa spp,and C.squarrosa increased differently under different grazing intensities.Population density of C.squarrosa was insensitive to grazing age.3.There was no significant differences in the biomass of the constructive population of L.chinensis under light grazing,the biomass of L.chinensis population under the other grazing intensities was significantly lower than that of the control,the population biomass of Stipa spp in light grazing and moderate grazing were no significant differences than the control(P>0.05).Severe grazing and extremely heavy grazing resulted in a significant decrease in the biomass of the population.In different grazing intensities,L.chinensis,C.squarrosa,C.striolata,annual and biennial plants and population biomass have important dependence on precipitation.Stipa spp biomass,Forb biomass,and L.chinensis relative biomass were weakly dependent on precipitation;the biomass of Stipa spp.and the relative biomass of L.chinensis had no obvious effect on the extension of grazing age;the biomass of C.squarrosa and annual and biennial plants under heavy and extremely severe grazing were more sensitive to the extension of the age.4.The index of the biodiversity index(Shannon-wiener index and Simpson index)were measured at the plant community level showed the highest when the medium grazing intensity,and the increase in precipitation had a certain positive effect on increasing the diversity,the extension of the grazing period did not deviated the pattern of highest biodiversity under the moderate grazing;Grazing utilization can promote the growth and material accumulation of forage grass,under light grazing,the net productivity of grassland vegetation is the highest,and the net productivity of grassland under grazing utilization is mostly manifested as different degrees of over-compensation.5.From the point of view of livestock production,the extremely heavy grazing and severe grazing will not obtain more grassland carrying livestock productivity per unit area.Under moderate grazing,both the higher unit livestock productivity level and the more ideal one can be obtained.From the unit grassland area calculate the weight gain of livestock,it was increased with the increase of grazing intensity,in 2014(the first year of the experiment),there was no significant differences between the moderate,heavy and extremely heavy grazing,there was no significant differences between heavy and extremely heavy grazing in 2016,but the grassland carrying livestock productivity per unit area in each grazing gradient was less than in 2014.Due to abundant rainfall,grassland carrying livestock productivity per unit area increased significantly with grazing intensity in 2015,and were moderate,heavy and extremely heavy grazing.grassland carrying livestock productivity per unit area with three heavy grazing intensities was higher than that in 2014 and 2016;With the increase of grazing intensity,the feed intake per unit area of forage grass is continuously increasing,and the feed intake per animal pasture is continuously decreasing,with the prolonged grazing period,the net productivity of vegetation is reduced,the feed intake of livestock under high and extremely high grazing is reduced,the precipitation significantly increased,the net productivity of vegetation increased,and the grass intake of livestock increased.The increase of grazing intensity increased the intake rate and showed a change of logarithmic function.The precipitation increased by 47.17% compared with the annual mean value of the area,and it could decrease by about 8% under different grazing intensity;In addition,from the three-year test data,it can be seen that under the light and moderate grazing intensities,higher grass and livestock transformation efficiency can be achieved.