The Thresholds Of Economical And Damage Of Rodent Control Under Different Grazing Patterns In Typical Steppe

Study on impact on rodent community and plant community from different grazing patterns was essential both for the calculation of damage threshold and economical thresholds(ET)and the management decisions.An experiment was conducted in typical steppe in Inner Mongolia in each autumn from 2012 to 2016,to investigate rodent density and aboveground biomass of forage.Rodents were captured with live method,and character of plant community was measured with qudrat method.The rodent damage was estimated using the density and daily intake of rodents to determine forage loss.The purposes of the research were to reveal the community dynamic of rodent and plant under different grazing patterns,and the relationship between rodent community and plant community.We analyzed the species number of rodent community and the population dynamic of each species under different grazing patterns.The annual of character of plant community in typical steppe were analyzed at the same time.The results are as follows:(1)The structure of the rodent community under different grazing patterns is consistent,but the number of species in over-grazing area is slightly higher than that in the grazing area and the grazing area.During the period from 2012 to 2016,the phenomenon of community succession occurred.There was no significant difference in the number of rodents captured under different grazing patterns,but the change rate of rodents in over-grazing area was significantly higher than prohibited-grazing area and rotational-grazing area.(2)The composition of plant communities in different grazing ways was similar.Only the density of Artemisia frigida showed a significant reduction in 2013-2015.The plant height was no significant difference in plant height among different grazing areas(P>0.05).But Density,biomass and forage loss ratio were significantly different(P<0.05),in over-grazing area the plant height,density,biomass and forage loss ratio were relatively low,while the prohibited-grazing area was relatively high.(3)The three-parameter sigmoid curve modeled the relation between rodents density and forage loss,which was better than that of other models,and the formula was:Loss=k/(1+ea-rdensity).The largest forage loss(=23.30%)occurred,when the rodents density was larger than 906 standard rodent units per hectare.The damage threshold was 174 standard rodent units per hectare in the typical steppe.(4)The economic thresholds were calculated during 2012-2016,and the average economic threshold for rodents was 172 standard rodent units per hectare in the five years.(5)The comprehensive damage threshold and the economical thresholds can be obtained.The threshold that without causing significant economic loss,nor does it cause a significant loss of forage was 172-174 standard rodent units per hectare.