Spatial-temporal Dynamic Balance between Livestock Carrying Capacity and Productivity of Rangeland in Gannan of Gansu Province,China

By use of rangeland and livestock data investigated during 2005-2007 and Terra/MODIS(Moderate-resolution Imaging Spectroradiometer) daily surface reflectance product of MOD09GHK from 2005 to 2007 in Gannan,rangeland productivity and livestock carrying capacity on the spatial-temporal scales were studied.The models of monitoring rangeland aboveground biomass,available forage,theoretic livestock carrying capacity and balance between forage and animal were established based on the average available yield of rangeland in growth season in Gannan prefecture.Results suggested that: 1) the total available green forage yield in Gannan prefecture was 61.9×108 kg,of which warm seasonal grazing rangeland was 35%,cool seasonal grazing rangeland was 24%,and all season grazing rangeland was 42%.2) The total theoretic livestock carrying capacity in the three years was 689.5×104 sheep units,the overgrazing rate was 82% for cool seasonal grazing rangeland and 84% for all season grazing rangeland.However,overgrazing rate in warm seasonal grazing rangeland was 37%.For the rangeland of the Gannan prefecture,the average overgrazing rate for the three years was 26%.3) There were a great differences between rangeland supply and livestock demand in Gannan prefecture.If the overgrazing livestock couldn't be fully decreased,about 26×108 kg of forage will be supplemented,which covers 42% of the total available green forage yield in rangeland of Gannan prefecture.This condition isn't feasible in theoretic and practice.If the overgrazing livestock decreased by 50% and 80% for agriculture and rangeland mixed area and pastoral area,supplemented forage will be about 13×108 kg and 5.2×108kg,they account for 21% and 8.4% of the total available green forage yield in rangeland of Gannan prefecture.