Impacts of Dung Combustion on Carbon Cycle of Grassland Ecosystem
摘要
There are two yak dung utilization pattern in north Tibetan,one is all dung remain in rangeland and return to soil to supplement the organic carbon and nutrition in soil and the other is dung removing out of grassland ecosystem and combusting as fuel.Comparing with the dung back to soil situation,dung combustion changes the carbon cycle and carbon balance in the grazing alpine meadow ecosystem.Consideration of dung combusted for energy,the net biome production(NBP)of the energy-grazing alpine meadow ecosystem can be accounted by adding the carbon import(dung production)to,while subtracting carbon export(livestock intake,dung combusted and dung respiration)from NEP(NEP=NPP-Rs).In order to depict the key stage of the carbon cycle of the alpine meadow,indicators were measured by various methods,for examples,with plot survey to get the data of biomass and NPP,the LI-8100 CO2 flux system(LI-COR Inc.,Lincon,NE,USA)used to measure the soil respiration(Rs),and application with household interview to get the data of yak dung(Dt,De).The yak intake(Gi)and dung respiration(Rd)is estimated by modeling.At presently,about 82.6%of yak dung was combusted for resident energy in north Tibetan.Impact of dung combustion on carbon cycle of alpine meadow ecosystem lies in:1)The direct effect is dung-derived carbon emission to atmosphere increase and that back to soil decrease.In the situation of dung combusted as fuel,the dung-derived C emission from both the process of dung heterotrophic respiration and dung combustion reached 10.09 gC/m2.a,which was 6.64 gC/m.2a more than that in the situation of dung back to soil.Correspondingly,the dung-derived C backt o soil is only 1.40 gC/m2.a,6.64 gC/m 2.a less than that in the situation of dung back to soil;2)The indirect effect is the primary production decrease for the soil infertile via dung removing out the ecosystem.The carbon captured by vegetation was only 304.33 gC/m2.a,which was 49.67 gC/m 2.a less than that in the situation of dung back