Rice-wheat Growth And Greenhouse Gas Emission And Model Simulation Under Nighttime Warming

Climatic warming is one of the main properties of climatic change,the range of air temperature increase showed obvious diurnal and seasonal asymmetry.Temperature is an important environmental factor,its change affects the farmland ecosystem.Field experiments were conducted to investigate the effects of night warming on crop growth and greenhouse gas emissions(methane and nitrous oxide)with the method of closed static chamber-gas chromatography in rice-winter wheat rotation system.DNDC(Denitrification-Decomposition)model was used to simulate greenhouse gas emissions.It is helpful in simulating and predicting future rice and winter wheat production and greenhouse gas emission under global climate change.The main results are listed as below:(1)Growth and yield of rice and winter wheatNighttime warming decreased tiller number,SPAD value,photosynthesis and transpiration parameters,and yield components(effective panicle number,grain number per panicle)in rice.Rice yield was reduced by 32.54%under nighttime warming.The average air temperature of canopy increased about 1.12℃ during the whole winter wheat growth period.The photosynthesis and transpiration parameters increased at joting stage,grain-filling stage,but decreased at heading-flowering stage.The decreases in leaf area index,effective panicle number,grain number per panicle,while increase in 1000-grain weight were observed under nighttime warming.(2)Greenhouse gas emission in rice-wheat rotation systemNighttime warming had no effects on seasonal dynamics of CH4 and N2O emissions in rice-winter wheat rotation system.CH4 and N2O fluxes and cumulative emssions were significantly increased.Nighttime warming increased the uptake of CH4 by soil at the early growth stages of winter wheat,but promote CH4 emission from winter wheat soil at its later growth stages.The total global warming potential increased by about 50.07%under nighttime warming.(3)Simulation and sensitivity analysis with DNDC modelDNDC model can be used to simulate crop yields and CH4 emission dynamics in rice-winter wheat rotation system,with higher correlation coefficients between the simulated and measured results.The sensitivity analysis showed that,rice yield was sensitive to temperature and nitrogen application rate.Winter wheat yield was sensitive to temperature and precipitation,and CH4 emission was sensitive to temperature,soil organic carbon content and clay content.