Effect Of Simulated Warming And Declining Rainfall On Soil Respiration And N₂O Emission From Arid Farmland

Global warming has become an important atmospheric environmental issue and has gotten the worldwide attention. The changes of the atmospheic circulation and hydrological model caused by the global warming can lead to the changes of global or regional precipitation patterns. Global warming and precipitation change have a major impact on crop growth and soil ecological processes. Main cause of global warming is the increase of greenhouse gases in atmospheric. Carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) are important greenhouse gases and farmland is one of the important emission sources of CH4 and N2O. To investigate the influence of diurnal warming and precipitation change on soil respiration and N2O emission fluxes, field experiments were adopted which include winter-wheat growing season and soybean growing season. The entire experimental field was divided into four equal-area sub-blocks, which are the control treatment (CK), the diurnal warming treatment (T), the precipitation reduction treatment (P) and the diurnal warming with precipitation reduction treatment (TP). Infrared radiation heating pipes are used for diurnal warming, precipitation reduction treatment using artificial rainfall interception methods. Soil respiration rates and soil N2O fluxes were analyzed by static chamber-gas chromatograph method. The study will provide the base to objectively evaluate the ecological effect of diurnal warming and precipitation reduction, as well as to estimate the regional farmland greenhouse gases emission and its’long term tendency in farmland under diurnal warming and reducing precipitation.Results indicated that:compared with CK, T, P, and TP treatments did not change the season pattern of soil respiration rates and soil N2O fluxes in winter-wheat farmland. T significantly increased soil respiration rates during the tiller-turning green stage, while, TP significantly reduced soil respiration rates during the jointing-booting and maturity stage. T significantly increased the cumulative emissions of CO2 during the tiller-turning green stage, while, TP significantly reduced the accumulation of soil CO2 emissions during the maturity stage. TP significantly decreased the cumulative of soil CO2 during the whole growth period. In the respect of N2O emissions fluxes, compared with CK, T significantly increased N2O fluxes, T, P, and TP had no significant effects on the cumulative emissions of N2O from soil in winter-wheat farmland.Compared with CK, T, P, and TP treatments did not change the season pattern of soil respiration rates in soybean farmland. T did not change the season pattern of soil N2O fluxes, P and TP may change the season pattern of soil N2O fluxes in soybean farmland. Compared with CK, T, P and TP had no significant effects on soil respiration rates during the soybean growth season. T significantly increased the average soil N2O fluxes during the three-leaf stage and branching stage, while, P and TP significantly reduced the average soil N2O fluxes. From the point of view of all the observation period, T significantly increased the average soil N2O fluxes, while, P and TP significantly reduced the average soil N2O fluxes. Compared with CK, T, P and TP were significantly increased the cumulative emissions of N2O during the branching stage. From the point of view of all the observation period, T significantly increased the cumulative emissions of N2O, while, P and TP significantly reduced the cumulative emissions of N2O.