Increase of N_2O fluxes in agricultural peat and sandy soil under elevated CO_2 concentration:concomitant changes in soil moisture,groundwater table and biomass production of Phleum pratense

摘要

The effects of elevated atmospheric CO_2 concentration on soil moisture,N_2O fluxes,and biomass production of Phleum pratense were studied in the laboratory.Farmed peat and sandy soil mesocosms sown with P.pratense were fertilized with a commercial fertilizer.In peat soil 10 g N m~(-2) of commercial fertilizer were added and in sandy soil 15 g N m~(-2).In both experiments,soil moisture was regulated with deionized water;18 mesocosms were tended to keep equally moist,and the other 18 were watered with equal amounts of water.Nine mesocosms from both watering treatments were grown under ambient (360 mu mol mol~(-1)) CO_2 concentration and the remaining nine under doubled (720 mu mol mol~(-1)) CO_2.N_2O efflux was monitored using a closed chamber technique and a gas chromatograph.The elevated supply of CO_2 increased production of above-and belowground biomass,soil moisture and N_2O fluxes,but decreased the total N content in the aboveground biomass,especially for the sandy soil.In similar water levels,N_2O efflux from the sandy soil was the same magnitude as that from the peat soil.In addition to moisture,N availability was the main limiting factor for N_2O production,but C availability also seemed to regulate the denitrification activity.In addition to an increase in C availability the increase in the N_2O efflux under the raised CO_2 concentration also required a simultaneous increase in soil moisture.