耕作制度对川中丘陵区冬灌田CH4和N2O排放的影响

采用静态暗箱/气相色谱法连续2 a田间原位测定,研究川中丘陵区冬灌田CH₄和N₂O的排放特征和不同耕作制度对冬灌田CH₄和N₂O排放的影响.结果表明,1a只种1季中稻冬季灌水休闲的冬灌田(PF),在水稻生长期,CH₄平均排放通量为(21.44±1.77)mg·(m²·h)^-1,非水稻生长期为(3.77±0.99)mg·(m²·h)^-1,分别大大低于以前文献报道的在西南其它地方观测值;全年CH₄排放量以水稻生长期CH₄排放量为主,非水稻生长期CH₄排放量仅占全年总排放量的23.2%.冬灌田N₂O排放通量年均值为(0.051±0.008)mg·(m²·h)^-1,且主要集中在水稻生长季,非水稻生长期N₂O排放量仅占全年总排放量的8.1%.在采用水旱轮作制后,冬灌田CH₄排放量大大降低,稻-麦轮作(RW)和稻-油菜轮作(RR)全年CH₄排放量分别为PF的43.8%和40.6%.但冬灌田改为水旱轮作制后,N₂O排放量显著增大,RW和RR的N₂O年排放量分别是PF的3.7倍和4.5倍.综合考虑冬灌田在采用不同耕作制度后排放CH₄和N₂O的全球增温潜势(GWP),无论是短时间尺度还是长时间尺度,采用3种耕作制度全年所排放的CH₄和N₂O所产生的综合GWP都为:PF RW≈RR.在20a、100a和500a时间尺度上,PF分别约是RW和RR的2.6、2.1和1.7倍.冬灌田改为水旱轮作制度后能大大减少CH₄和N₂O所产生的综合GWP.

Effects of Tillage-Cropping Systems on Methane and Nitrous Oxide Emissions from Permanently Flooded Rice Fields in a Central Sichuan Hilly Area of Southwest China

Using the static opaque chamber method, a field experiment was conducted in situ for two years to study the effects of three cultivation systems on CH4 and N2O emissions from permanently flooded rice fields in a hilly area in Southwest China. The results show that the average CH4 fluxes from a permanently flooded rice field with a single middle rice crop and flooded with no winter crop (PF) were (21.44 +/- 1.77) mg x (m2 x h)(-1) and (3.77 +/- 0.99) mg x (m2 x h)(-1) during rice-growing and non-rice growing periods, respectively, where both values were much lower than many previous reports from similar regions in Southwest China. The annual CH4 emission was mainly occurred in the rice growing period, being only 23.2% 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 (0.051 +/- 0.008) mg x (m2 x h)(-1) and the N2O emission also intensive in the rice growing period. However, being only 8.1% of total annual N2O flux emitted from the non-rice growing period. After implementing the rice-wheat rotation (RW) and rice oil-seed rape rotation (RR), the CH4 emissions were reduced substantially, only 43.8% and 40.6% of those of PF, respectively. However, the N2O emissions were increased after conducting RW and RR systems, which were 3.7 and 4.5 times larger than those of PF. The global warming potentials (GWPs) of the CH4 and N2O emissions under the three tillage-cropping systems were assessed in an integrated way. The results show that the integrated GWPs of the CH4 and N2O emissions are in the following sequence: PF>RR approximately equal to RR. Within 20, 100 and 500 years spans, the GWPs of the CH4 and N2O emissions of PF were 2.6, 2.1 and 1.7 times larger than those of RW (or RR), respectively. After introducing rice-wheat or rice oil-seed rape rotation systems into the permanently flooded rice fields, the integrated GWPs of the CH4 and N2O emissions were decreased largely.