Effects Of Summer And Winter Rotational Grazing Of Tibetan Sheep On Plant,Soil And Livestock Of Alpine Ecosystem

Alpine grazing system is one of the world's unique ecosystem.Therefore,We selected Tibetan sheep rotational grazing as research object from 2010-2012 in alpine meadow of Qinghai-Tibetan plateau,and overall observed soil-grassland-livestock system response to grazing management in roder to provide decision-making basis for sustainable development in alpine pastoral area.1)Non-grazing and 16 sheep/ha reduced species richness,Shannon Wiener index and plant density,but 8 sheep/ha significantly increased the species richness,Shannon Wiener index and plant density.The relationship between plant diversity and standing crop showed hump curve(Y=-0.0033x²+0.4875x-1.3179).Fencing enhanced alpine meadow plant productivity.With the increase of stocking rates,grazing reduced the density of grasses,sedges,high palatable,plant which height is between 20cm-40cm.At the same time,grazing increased the the density of forbs,low palatable plant,unpalatable plant and plant which height is less than 20cm,but had no obvious effect on the density of legume,medium palatable plant and plant which height is more than40cm.2)Body weight of 8 sheep/ha was higher than 16 sheep/ha 15.7%(P=0.021)and8.8%(P=0.024)in 2011 and 2012 respectively,but there was no significant difference in 2010(P=0.612).Average daily gain of 8 sheep/ha was 17.4%(P=0.011)higher than 16 sheep/ha in 2011 but there was no significant difference in 2010(P=0.214)and 2012(P=0.072)respectively.Dry matter intake of 8 sheep/ha was 9.6%(P=0.004),14.5%(P=0.001)and 12.4%(P=0.001)higher than 16 sheep/ha in 2010,2011 and 2012 respectively.Dry matter intake(R²=0.9285,P<0.001)and Average daily gain(R²=0.2415,P=0.015)had a positive relationship with Shannon-wiener diversity index,so increasing grassland plant diversity can benefit to livestock productivity.3)After 24 month decomposition,8 sheep/ha dung decomposition rate of weight,nitrogen,phosphorus and potassium was higher than 0 sheep/ha 20.1%(P<0.001)?21.9%(P=0.001)?25.5%(P=0.001)18.6%(P<0.001)?17.6%(P<0.001).Compared with 0 sheep/ha 8 sheep/ha significantly decreased the dung content of lignin(P<0.001),Ca(P<0.001),Mg(P<0.001),Zn(P<0.001),S(P<0.001)and Cu(P<0.001)and significantly enhanced dung content of ash(P<0.001),C/N(P<0.001)and C/P(P<0.001).16 sheep/ha significantly decreased NDF(P=0.002)and ADF content(P<0.001).The fastest decomposition rate of the warm pasture was9.92 sheep/ha.50%and 90%decomposition need about 15 and 53 month in warm pasture.The fastest decomposition rate of the cold pasture was 9.73 sheep/ha.50%and 90%decomposition need about 17 and 60 month in warm pasture.Dung weight(R²=0.5982,P<0.001),N(R²=0.7187,P<0.001),organic carbon(R²=0.6253,P<0.001),P(R²=0.6543,P<0.001)and K(R²=0.6516,P<0.001)content were positively related with Shannon-wiener diversity index,so high plant diversity could speed up dung material circulation.4)In 2012 compared with 0 sheep/ha,8 sheep/ha significantly increased f orage 16.2%CP(P<0.001),13.1%P(P<0.001),9.5%EE(P=0.015),13.8%WSC(P<0.001),10.6%ash(P<0.001),19.2%K(P<0.001),8.1%Mg(P<0.001),12.9%Zn(P<0.001)content and 8 sheep/ha decreased 9.6%Mn(P=0.005),14.6%Cu(P=0.001),11.3%NDF(P=0.003),4.8%ADF(P=0.015),20.4%C/N(P<0.001)and 18.5%C/P(P<0.001).Stocking rates has n o significant effect on forage organic carbon and Ca.Forage CP(R²=0.6654,P<0.001),P(R²=0.7595,P<0.001),K(R²=0.642,P<0.001),WSC(R²=0.4145,P<0.001),crude fat(R²=0.5531,P<0.001),ash(R²=0.4822,P<0.001),Mg(R²=0.5784,P<0.001)and Zn(R²=0.5371,P<0.001)content were pos itively related with Shannon-wiener diversity index so maintain high grassland plant diversity could improve forage quality.5)With the increase of stocking rate,grazing reduced soil organic carbon,total nitrogen,K and S content.Compared with 0 sheep/ha,8 sheep/ha significantly enhanced P,Cmic,Nmic content 15.1%(P<0.001)?38.3%(P<0.001)?65.1%(P<0.001),16 sheep/ha significantly reduced Ca,Zn,Mn and Mg content 16.9%(P<0.001)?32.6%(P<0.001)?10.1%(P<0.001)and 16.1%(P<0.001).Stocking rates had no significant effect on soil Cu content(P=0.5351).Soil P(R²=0.5931,P<0.001),C_mic(R²=0.5931,P<0.001),N_mic(R²=0.4197,P<0.001)and Mg(R²=0.1678,P<0.001)content were positively related with Shannon-wiener diversity index so high plant diversity could enhance microbial activity.6)After 24 month decomposition,8 sheep/ha litter decomposition rate of weight,nitrogen,phosphorus and potassium was higher than 0 sheep/ha 23.9%(P<0.001)?21.1%(P=0.001)?22.1%(P=0.001)?20.2%(P<0.001)?23.2%(P<0.001).Compared with 0 sheep/ha 8 sheep/ha significantly decreased the litter content of lignin(P<0.001),Ca(P<0.001),Mg(P<0.001),Zn(P<0.001),S(P<0.001)and Cu(P<0.001)and significantly enhanced litter content of ash(P<0.001),C/N(P<0.001)and C/P(P<0.001).16 sheep/ha significantly decreased NDF(P<0.001)and ADF content(P=0.011).The fastest decomposition rate of the warm pasture was9.92 sheep/ha.50%and 90%decomposition need about 15 and 53 month in warm pasture.The fastest decomposition rate of the cold pasture was 9.73 sheep/ha.50%and 90%decomposition need about 17 and 60 month in warm pasture.Dung weight(R²=0.8809,P<0.001),N(R²=0.5791,P<0.001),organic carbon(R²=0.3143,P<0.001),P(R²=0.6171,P<0.001)and K(R²=0.7055,P<0.001)content were positively related with Shannon-wiener diversity index,so maintain high plant diversity could accelerate litter material circulation.This study showed that stocking rates had significant effect on soil physic al and chemical properties,forage productivity and quality,plant diversity,litte r and dung decomposition in alpine meadow.From these indexes,the study de fined suitable stocking rate for revealing material circulation of soil,plant and livestock,and had theory and practice value for sustainable management of alpi ne grazing system.