Study on Greenhouse Gas Emissions from Sandy Soil of Eastern Henan with Poplar-Crop Agroforestry System
In order to study the contribution rate of soil greenhouse gas emission in agroforestry,polar-crop agroforest-ry systems with two typical densities of shelterbelt(shelterbelt distance with 1000 m×1000 m(BT)and 200 m×200 m(ST)respectively)and 5-10 years old planted forest(CK)were investigated in eastern Henan.The seasonal emission fluxes of soil greenhouse gases(CO2,N2O,CH4)in poplar-crop agroforestry systems with different densities of shelterbelt were measured in field situ by the static chamber-gas chromatograph method.The results showed that arable land in eastern Henan was the sources of atmospheric CO2 and N2O,the sink of atmospheric CH4.Different agroforestry composite models have different characteristics on the intensity of soil greenhouse gas emissions or absorption.The flux of CO2 of all the treatments reached maximal seasonal emission in July.The values of the flux for the three treatments were 1163.17,1005.91 and 923.53 mg/(m2·h)respectively.Flux of N2O from BT reached maximal seasonal emission in July,but that of ST and the CK in August.N2O emission fluxes varied from 4.29 to 313.28 μg/(m2·h).The maximal absorption flux of CH4 was in July,the value of BT was the largest,with 4.41 mg/(m2·h).Different agroforestry affect greenhouse gas emissions from farmland soil by affecting farmland microclimate such as soil and air temperature and humidity.Warming and drying enhanced the characteristics of soil CO2 and N2O emission,but increased the function of soil as atmospheric CH4 absorption sink at the same time.The global warming potential(GWP)of BT,ST and CK was 1.50×105,1.03×105,0.885×105 kg C/hm2 respectively.Among all the treatments,the agroforestry with large shelterbelt distance has the biggest global warming potential,but forest has the smallest.Properly increasing the density of shelterbelt is conducive to reducing the GWP of farmland ecosystem.
AgroforestryGreenhouse gas emissionFarmland shelterbeltGlobal warming potential