A numerical simulation model is presented in this paper,which comprises the processes of crop growth,soil organic carbon decomposition,and methane emissions in agroecosystems. Simulation results show that the model ca...A numerical simulation model is presented in this paper,which comprises the processes of crop growth,soil organic carbon decomposition,and methane emissions in agroecosystems. Simulation results show that the model can simulate the main process of methane emissions well, and the correlation coefficient between the simulated values and observed data is 0.79 with 239 samples,which passed a significance test of 0.01.The average error of methane emission simulation in whole growth period is about 15%.Numerical analysis of the model indicates that the average temperature during rice growth period has much impacts on methane emissions,and the basic trend of interannual methane emissions is similar to that of average temperature.The amount of methane emissions reduces about 34.93%,when the fertilizer is used instead of manure in single rice paddy.展开更多
CH_4 emission rates have been measured continuously for the early rice of 1988 and late rices of 1987 and 1988 during entire growing seasons in a rice paddy field in Hangzhou,Zhejiang Province,China,by using an automa...CH_4 emission rates have been measured continuously for the early rice of 1988 and late rices of 1987 and 1988 during entire growing seasons in a rice paddy field in Hangzhou,Zhejiang Province,China,by using an automatic sampling and analyzing system.During most parts of the seasons CH_4 emission rates showed strong diurnal variations.Bi-mode patterns with the highest value in the afternoon and a second peak at mid-night were generally found for the early rice,while the highest values were almost always found in the night for the late rice.Bi-mode patterns with a second peak in the afternoon were also found during the reproductive phase of the late rice plants.These diurnal variations may be explained by the diurnal variations of the soil temperature and the activity of rice plants.Strong seasonal variations with one peak in the tillering stage and two during the reproductive phase of rice plants were observed for all the three growing seasons.The seasonal variations may be explained by the activity of rice plants,availability of organic substrates in the soil,and the activity of soil bacteria related to soil temperatures,Fertilization did not show significant effects on the total seasonal CH_4 emissions but slightly changed the pattern of the seasonal variations of the CH_4 emission rates.Averaged over the measuring periods and 8 spots,CH_4 emission rates of 7.8 mg m^(-2) h^(-1) for the early rice and 28.6 mg m^(-2) h^(-1) for the late rice were obtained. Based on these measured data,the total global emission of CH_4 from rice paddies is estimated to be about 90 Tg/yr ranging from 70 to 110,accounting for 20% of the total source of CH_4.展开更多
基金This study is supported by the National Natural Science Foundation of China under the Program No.49899270.
文摘A numerical simulation model is presented in this paper,which comprises the processes of crop growth,soil organic carbon decomposition,and methane emissions in agroecosystems. Simulation results show that the model can simulate the main process of methane emissions well, and the correlation coefficient between the simulated values and observed data is 0.79 with 239 samples,which passed a significance test of 0.01.The average error of methane emission simulation in whole growth period is about 15%.Numerical analysis of the model indicates that the average temperature during rice growth period has much impacts on methane emissions,and the basic trend of interannual methane emissions is similar to that of average temperature.The amount of methane emissions reduces about 34.93%,when the fertilizer is used instead of manure in single rice paddy.
文摘CH_4 emission rates have been measured continuously for the early rice of 1988 and late rices of 1987 and 1988 during entire growing seasons in a rice paddy field in Hangzhou,Zhejiang Province,China,by using an automatic sampling and analyzing system.During most parts of the seasons CH_4 emission rates showed strong diurnal variations.Bi-mode patterns with the highest value in the afternoon and a second peak at mid-night were generally found for the early rice,while the highest values were almost always found in the night for the late rice.Bi-mode patterns with a second peak in the afternoon were also found during the reproductive phase of the late rice plants.These diurnal variations may be explained by the diurnal variations of the soil temperature and the activity of rice plants.Strong seasonal variations with one peak in the tillering stage and two during the reproductive phase of rice plants were observed for all the three growing seasons.The seasonal variations may be explained by the activity of rice plants,availability of organic substrates in the soil,and the activity of soil bacteria related to soil temperatures,Fertilization did not show significant effects on the total seasonal CH_4 emissions but slightly changed the pattern of the seasonal variations of the CH_4 emission rates.Averaged over the measuring periods and 8 spots,CH_4 emission rates of 7.8 mg m^(-2) h^(-1) for the early rice and 28.6 mg m^(-2) h^(-1) for the late rice were obtained. Based on these measured data,the total global emission of CH_4 from rice paddies is estimated to be about 90 Tg/yr ranging from 70 to 110,accounting for 20% of the total source of CH_4.
