Effects Of Different Amount Of Swine Manure Biochar On Environmental Quality Of Red Paddy Soil

The rapid increase of greenhouse gases in the atmosphere leads to global warming,which has become a hot issue of human concern in recent decades.CH4 is an important greenhouse gas,and its contribution to the greenhouse effect is only lower than that of CO2.It is one of the important means to understand the global production and consumption of CH4 to study and summarize the transportation of CH4.Forests,effectively the"lungs of the earth",are the main body of terrestrial ecosystem that play an important role in global greenhouse gas exchange.Chinese fir(Cunninghamia lanceolata)is a unique fast-growing timber species in China.In the process of extensive planting,the source and sink of soil greenhouse gases have also been widely considered.In this study,based on the data of atmospheric CH4 fluxes and meteorological gradients from 2016 to 2018 measured by the national field scientific observation and the Huitong Chinese fir plantation ecosystem research station,the temporal variation characteristics of CH4 flux and its relationship with environmental factors were studied.The main results are as follows:(1)The diurnal variation of atmospheric CH4 flux of Chinese fir in the Huitong station was shown a single peak "V" shape.The annual diurnal variation of CH4 flux was positive(source)at 20:00～5:00 through the night and negative(sink)at 6:00～19:00 during the day.The minimum value appeared at 13:00(-0.409μg CH4·m-2s-1),the maximum value appeared at 03:00(0.014μg CH4·m-2s-1),and the annual diurnal range was 0.423μg CH4·m-2s·1.The sink duration and average daily range of CH4 flux varied with seasons.The duration of CH4 sink in spring,summer,autumn and winter was 6:00～18:00,6:00～19:00,7:00～18:00 and 6:00～17:00,respectively,and the duration was 13 h,14 h,13 h and 12 h,respectively.These results show that the duration of CH4 sink(negative value)is gradually prolonged from winter to spring to summer,while the duration of CH4 sink is gradually shortened from summer to autumn to winter.The average daily range in spring,summer,autumn and winter was 0.138,0.802,0.376 and 0.114μg CH4·m-2s-1,respectively.From winter to summer,the diurnal range of CH4 fluxes increased gradually,while from summer to winter CH4 fluxes of diurnal range decreased gradually.Under different weather conditions,the diurnal range of CH4 flux was sunny day>little cloud>overcast>cloudy day.The absorption capacity of the Huitong plantation ecosystem on a sunny day was the highest,while the absorption efficiency of cloudy weather was significantly reduced.(2)The annual variation of CH4 flux in the Huitong Chinese fir plantation ecosystem was low in summer and high in winter.The maximum value generally appeared in winter from December to February of the next year,and the maximum value in February in 2016,with the value of-23.237 mgC·m-2mon-1.The maximum value in December in 2017 and 2018 were-70.810 mg C·m-2mon-1and-65.589 mg C·m-2mon-1.The minimum value generally occurred in July of summer(in 2016～2018,the maximum value was-134.281,-204.767 and-180.780 mg C·m-2mon-1,respectively).From 2016 to 2018,the annual net emissions of CH4 flux were-1260.267,-1232.766 and-1538.123 mg C·m-2a-1,respectively.In other words,the Chinese fir ecosystem presents an obvious sink.(3)The CH4 flux of the Chinese fir plantation has a very significant quadratic polynomial relationship with soil temperature on a daily scale,and the saturated water vapor pressure difference,soil moisture,and pressure all present a very significant linear relationship;On a monthly scale,there is a very significant linear negative correlation with soil temperature and saturated water vapor pressure difference,a very significant linear positive correlation with soil moisture,and a significant linear positive correlation with pressure.(4)Three flux correction methods-double coordinate rotation,correction of spectral loss,and correction of storage—have significant effects on CH4 flux.By averaging the three-year data from 2016 to 2018,the CH4 flux increased by 72.1%,inducing CH4 sink with double coordinate rotation method,with an increase of 82.0%in the daytime and a decrease of 197.2%in the night.Using the correction of spectral loss method,CH4 flux was reduced by 9.1%,Which decreased by 8.4%during the day and increased by 10.5%at night;Finally,with the correction of storage method,CH4 flux increased by 49.1%,with an increase of 124.7%during the day and a decrease of 111.9%during the night.