水稻品种对CH_4产生、排放及δ^(13)CH_4的影响

Effect of Rice Variety on Production and Emission of CH_4 and δ^(13)CH_4

水稻品种是调控CH4产生和排放的关键因素。关于水稻品种对稻田产生和排放CH4的稳定性碳同位素组成(δ13CH4)的影响研究鲜见报道。通过温室盆栽和室内培养试验并结合稳定性碳同位素方法,研究了持续淹水条件下4个水稻生育期镇稻624、农香98和中早33的土壤CH4产生潜力、土壤溶液CH4浓度、CH4排放通量及产生、排放CH4的δ13C值,为最终筛选优质高产且低CH4排放的水稻品种提供CH4排放相关过程及其稳定性碳同位素方面的参考数据。结果表明:在分蘖期和拔节期,镇稻624和农香98的土壤CH4产生潜力显著高于中早33,在灌浆期和成熟期显著小于后者(P<0.05)。三者土壤CH4产生潜力、土壤溶液CH4浓度最高值和土壤Eh的最低值依次出现在拔节期(2.6μg·g-1·d-1,346.9μmol·L-1,-296 m V)、拔节期(3.2μg·g-1·d-1,425.9μmol·L-1,-316 m V)和灌浆期(2.4μg·g-1·d-1、435.2μmol·L-1,-308 m V)。各品种土壤CH4产生潜力均与相应土壤溶液中CH4浓度显著正相关(P<0.01),且与土壤Eh显著负相关(P<0.01)。镇稻624和农香98在分蘖盛期CH4排放通量最大(67.1和68.7 mg·m-2·h-1),中早33则在拔节期(58.5 mg·m-2·h-1)。各品种CH4季节排放总量依次为55.29、55.74和40.82 g·m-2,前二者无显著差异,显著高于中早33,这可能是镇稻624和农香98的土壤CH4产生潜力在分蘖期和拔节期显著大于中早33,而各品种CH4排放又相对集中在分蘖期和拔节期的缘故。相关分析表明,各生育期CH4排放通量与相应的土壤CH4产生潜力显著正相关(P<0.01)。可见水稻品种通过影响土壤的CH4产生,进而影响稻田CH4的排放。镇稻624和中早33土壤产生CH4的δ13C值从约-67.0‰增至-55.5‰,农香98则先减后增,范围为-64.2‰^-52.9‰,这说明镇稻624和中早33的土壤CH4产生途径差异较小,而二者与农香98差异较大。各品种排放CH4的δ13C值均先减后增,分别为-67.6‰^-48.5‰、-73.0‰^-47.3‰和-60.9‰^-46.7‰,季节平均值依次为-52.7‰、-52.5‰和-54.8‰。总体上,水稻品种影响排放δ13CH4值的季节变化。

Rice variety is a key factor regulating CH4 production and emission. However, little has so far been reported on effect of rice varieties onδ13C-value of CH4 produced and emitted. Pot and indoor incubation experiments were carried out and with the aid of the stable carbon isotope method, CH4 production potential of the paddy soil, CH4 concentration in pore water, CH4 production and emission flux as well asδ13C-value of the CH4 emitted from the paddy soils cultivated with different varieties of rice （Zhendao 624, Nongxiang 98 and Zhongzao 33） under continuous flooding at four rice growing stages were studied and measured, with a view to providing some data in respect to CH4 emission processes andδ13C-values of CH4 emitted for reference in screening rice varieties for quality ones both high in yield and low in CH4 emission. Results show that the paddy soils under Zhendao 624 and Nongxiang 98 were significantly higher than that under Zhongzao 33 at the tillering and booting stages in CH4 production potential but significantly lower at the grain-filling and ripening stages. CH4 production potentials, the highest CH4 concentration in pore water and the lowest soil Eh of the three paddy soils under Zhendao 624, Nongxiang 98 and Zhongzao 33 appeared at the booting stage （2.6 μg·g-1·d-1, 346.9 μmol·L-1, -296 mV）, booting stage （3.2 μg·g-1·d-1, 425.9 μmol·L-1, -316 mV） and grain-filling stage （2.4μg·g-1·d-1, 435.2μmol·L-1,-308 mV）, respectively. Correlation analysis shows that CH4 production potential of the paddy soil was significantly positively related to CH4 concentration in pore water, but significantly negatively to soil Eh （P〈0.01）, regardless of rice varieties planted. CH4 fluxes from the plots under Zhendao 624 and Nongxiang 98 peaked at the booting stage （67.1, 68.7 mg·m-2·h-1）, while that from the plot under Zhongzao 33 did at the tillering stage （58.5 mg·m-2·h-1）. The total CH4 emission from the plots under Zhendao 624 and Nongxiang was 55.29 and 55.74 g·m-2, respectively, posing no obvious difference between the two, while that from the plot under Zhongzao 33 was 40.82 g·m-2 （P=0.05）, much lower than the former two, partly by reason that CH4 production potentials of the former two were significantly higher than that of the latter at the tillering stage and booting stage, when CH4 emissions occurred concentratedly in all the three. Correlation analysis also shows that CH4 flux was significantly positively related to CH4 production potential of the paddy soil at all the four stages （P〈0.01）, which fully demonstrates that rice plants different in variety affect CH4 production and then CH4 emission through regulating soil CH4 production potential. δ13C-values of the CH4 produced in the plots under Zhendao 624 and Zhongzao 33 gradually increased within the range of-67.0‰^-55.5‰, making no big difference between the two soils during the rice growing season, while that in the plot under Nongxiang 98 declined first and rose again within the range of-64.2‰^-52.9‰, which means that the soils in the plots under Zhendao 624 and Zhongzao 33 are quite similar in path way of CH4 production, but sharply different from that under Nongxiang 98. The CH4 emitted from the three plots all displayed a general trend inδ13C-value, declining first and rising again and varying in the range of-67.6‰^-48.5‰,-73.0‰^-47.3‰and-60.9‰^-46.7‰, respectively. To sum up, the effect of rice variety onδ13CH4 varies with the season.