DNDC模型对川中丘陵区稻田CH_4、N_2O排放的模拟对比分析

Research of tillage-cropping systems on CH_4 and N_2O emission from permanently flooded rice fields in a central Sichuan hilly area of southwest China

利用IKONOS高分辨率(1m)卫星遥感图,进行典型抽样和地形→土地利用→土地覆盖→综合信息提取的方法,选定了代表川中丘陵区类特征的四川省金堂县为研究区域,通过对研究区域中不同固定耕作制度下代表性田块的选取,于2005年5月—2006年5月对田块管理者进行作物田间管理、作物产出等农业生产实际情况调查和分析,进行土壤理化性状、水样的测定,并结合当地的气象资料,利用DNDC模型模拟川中丘陵区不同耕作制度下稻田温室气体的排放情况。结果表明:冬水田-水稻田(PF)水稻生长期CH4排放通量为2.24 kg.hm-2.d-1,占年排放量的80.73%;水稻生长期和冬闲期N2O通量分别为0.033和0.003 6 kg.hm-2.d-1,水稻生长期排放量为4.28 kg.hm-2,占年总排放量的83.59%。CH4和N2O排放量在水稻整个生季节存在明显的互为消长关系。油菜-小麦田(RR)水稻生长期CH4排放通量为1.16 kg.hm-2.d-1,是休闲期的20.71倍,水稻生长期CH4排放量占年排放量的90.48%;水稻生长期和非水稻生长期N2O排放通量分别为0.070和0.027 kg.hm-2.d-1,水稻生长期N2O排放量为8.01 kg.hm-2,占年排放量的54.19%。小麦-水稻田(RW)水稻生长期CH4排放通量为1.24 kg.hm-2.d-1,是休闲期的21.02倍。水稻生长期CH4排放量占年排放量的89.75%;水稻生长期和非水稻生长期N2O排放通量分别为0.089和0.030 kg.hm-2.d-1,水稻生长期N2O排放量为9.61 kg.hm-2,占年排放量的55.23%。PF年CH4排放量是RR和RW的近3倍,且少一季作物产量,应尽量将冬水田改为两季田。

Used the high resolution（1 m） IKONOS satellite,selected representative of the middle Jintang hilly area feature as the study area.Researched of CH4 and N2O emissions from three kinds of paddy-rice fields-permanently flooded paddy fields（PF）,rapeseed-paddy rice fields（RR） and winter wheat-paddy rice fields（RW） from May 2005 to May 2006.Had some detailed farmer investigations,include crop type,tillage,fertilizer,manure type,irrigation,output.And determined and statisticsed soil pH,N con-centration in rainfall,meteorological data and so on.The results show that： The average CH4 fluxes from a permanently flooded rice field with a single middle rice crop and flooded with PF were 2.24 kg·hm-2·d-1 and 0.512 kg·hm-2·d-1 during rice-growing and non-rice growing periods,respectively.The annual CH4 emission was mainly occurred in the rice growing period,being only 29.27 % of the total annual CH4 flux emitted from the non-rice growing period,though the latter occupied two thirds of a year.The annual average flux of nitrous oxide was 0.014 kg·hm-2·d-1.N2O emission also intensive in the rice growing period.However,being only 16.41 % of total annual N2O flux emitted from the non-rice growing period.There was a clear trade-off between CH4 and N2O emis-sion in paddy fields during the growth period of paddy-rice.CH4 emission flux in rice growth stage of RR was 1.16 kg·hm-2·d-1,it was 20.71 times of leisure period.CH4 emissions of rice growth stage account for the total emissions was 90.48%.N2O emission flux in rice growth stage and leisure period of RR were 0.070 and 0.027 kg·hm-2·d-1,respectively.N2O emissions of rice growth stage account for the total emissions was 54.19%.CH4 emission flux in rice growth stage of RW was 1.24 kg·hm-2·d-1,it was 21.02 times of leisure period.CH4 emission of rice growth stage account for the total emissions of RW was 89.75%.N2O emission flux in rice growth stage and leisure period of RW were 0.089 and 0.030 kg·hm-2·d-1,respectively.N2O emissions of rice growth stage account for the total emissions was 55.23%.CH4 emissions of PF was nearly 3 times of RR and RW,and less one season of crop yields.Should as far as possible to change PF to RR and RW.