【作者】 王平；

【导师】 黄耀；

【作者基本信息】 南京农业大学 ， 生态学， 2009， 博士

【摘要】 温室气体引起的全球气候变暖已成为全世界面临的重大环境问题。甲烷(CH4)是重要的温室气体之一。2005年大气中CH4浓度为1774 ppb,比工业革命前增加了1059 ppb,但自二十世纪80年代以来其增长速率呈下降趋势。灌溉稻田是大气中CH4的重要来源。中国作为水稻生产大国,其稻田对全球CH4排放的影响已经成为全球变化研究的焦点之一。近50多年来,我国水稻种植面积和农业管理方式等发生了巨大变化。大量研究表明,有机肥是稻田甲烷产生的重要基质来源。毫无疑问,水稻种植面积和施肥结构等的变化必然影响我国稻田CH4排放量。估计我国的稻田CH4排放量,研究其时空变化规律,不仅对于我国的科学研究和国家利益具有一定的重要性,同时也是全球变化研究的内容之一,有助于评价我国水稻生产在区域稻田甲烷排放中的作用,同时为有效制定农业温室气体减排对策提供科学依据。本文的研究目的为：通过调研我国1955-2005年水稻生产农业耕作变化数据库,估算1955-2005年中国稻田CH4排放的情况,并分析中国稻田CH4排放的时空变化规律。本研究通过水稻农业生产管理信息农户问卷调查,结合现有文献资料调研的基础上,采取一定的规则对所获取的数据进行整理后,建立了包括1950s-1990s中国水稻田农业耕作变化数据库,包括水稻种植面积、产量、有机肥施用量及结构、化肥施用量及类型、水分管理方式等要素；在已建立的1950s-1990s中国水稻田农业耕作变化数据库的基础上,根据中国水稻种植制度区划,估算了中国稻田历年外源有机碳投入情况；将我国不同区域水稻生产及其与CH4排放有关的数据和其他输入参数代入CH4MOD运行,估算1955-2005年稻田甲烷排放的时空变化。研究结果表明,1955-2005年我国水稻种植面积变化极其明显。1950s中后期为31.1×106hm2左右,至1960s下降到29.2×106hm2左右；其后稳步上升,至1970s达到历史最高,约34.9×106hm2,这主要是由于大力推广双季稻,1950s中期双季稻种植面积约占水稻总面积的50%,1970s中期超过70%；由于双季稻种植面积逐年减少,1970s中期以后全国水稻面积下降,2001-2005年平均种植面积为28.4×106hm2,双季稻面积所占比例在45%左右。1955～2005年间中国水稻田外源有机碳投入持续增加。1950s-2000s每个年代的平均有机碳投入分别为2.96、3.00、3.41、3.64、3.83和4.28 tC·ha-1.其中来源于秸秆根茬的有机碳投入呈增加趋势；而来源于农家肥的有机碳投入则呈降低趋势,其占总投入比例从1950s的77.7%降低到2000s的37.2%；绿肥有机碳投入占总有机碳投入比例不高,其变化范围为1.5%-8.5%,基本上呈现出先增加后减少的趋势。在空间分布上,水稻田有机碳投入高值区主要集中在华中和华南地区,近50年其范围基本保持在2.88～5.61 tC·ha-1,而低水平投入区则在东北、西北区投入水平变化范围为1.11～2.47 tC·ha-1。来源于秸秆根茬的有机碳投入增加是稻田有机肥投入增加的重要原因。上世纪五十年代中国稻田秸秆根茬有机碳投入为0.63 t Cha-1,约占总投入的20.4%,到二十一世纪初期,秸秆根茬有机碳投入为2.64 t Cha-1,约占总有机碳投入的61.1%。秸秆根茬投入增加是秸秆还田率提高和作物产量增加的共同作用。近50年来中国大陆水稻生长季甲烷排放总体呈增加趋势,1960-1975年增加速率最快,年均增加167Gg；自1970s中期开始增加速率减缓,年均增加量54Gg。1960s、1970s、1980s和1990s年均排放量分别为3.18±0.53、4.71±0.27、5.21±0.24和5.79±0.34Tg/yr,2000-2005年平均排放量为6.25±0.36Tg/yr。由于未考虑杂交稻种植和化肥氮施用对CH4排放的影响,估计值可能偏高。中国稻田CH4排放具有较强的时空变异性。中国稻田甲烷排放高值区主要分布在湖南、湖北、江西、广东、广西、江苏和安徽省,约占全国稻田甲烷排放总量的73%。在区域水平上,我国各水稻种植区CH4排放总量自1950s以来均呈增加趋势。自20世纪70年代以来,华中和华南地区稻田CH4排放的增加趋势减缓,但1980-2005年间东北三省CH4排放增加显著,这主要归因于该区水稻种植面积的迅速扩大和气温升高。本研究通过覆盖中国主要水稻种植区的水稻农业耕作农户问卷调查,建立了1950s-1990s中国水稻农业基础耕作变化基础数据库。将稻田甲烷排放模型CH4MOD和GIS空间化数据库结合,模拟估计了中国大陆1955-2005年水稻生长季稻田甲烷排放量,研究了较长时间序列内中国稻田CH4排放的时空变异规律,系统的回答了中国稻田CH4排放的过去,这将有助于我们评价中国水稻历史生产在区域稻田CH4排放中的贡献,同时可以为制定有效温室气体的减排措施提供科学支持。更多还原

【Abstract】 Methane (CH4), one of the most important greenhouse gases in the atmosphere, has been paid much attention due to its substantial contribution to global warming. The concentration of methane in the atmosphere is 1774 ppb in 2005, much more 1059 ppb than before the PreIndustrial Revolution, but its growth rate declines since the 80s twenty century. Irrigated rice fields have been recognized as an important source of global CH4 emission.China is one of the most important rice-producing countries in the world.The impact of Chinese rice fields on atmosphere CH4 incurs increasing attentions. The rice-planted area and agricultural management ways have changed dramatically in the past 50 years. A large number of studies have showed that organic manure input is the main sources of methane emissions from rice fields. Undoubtedly, the changes in rice-planted area and fertilization will inevitalbly affect the methane emissions from Chinese rice fields. Estimates of CH4 emission from Chinese rice fields over the past decades, is of great importance not only for evaluation the role Chinese rice production have played in regional methane emissions, but also helps to provide support for making effecticve mitigation countermeasures against climate change.The objectives of this study are to estimate methane emissions from Chinese rice fields over the past fifty years and analyze the changes in temporal and spatial based on model and database of changes in Chinese rice agricultural cultivation.In this study, we collected 1950s-1990s rice agricultural cultivation data through farmer questionnaire survey, combined with formal statistical data, including rice yield, planted area, organic fertilizer application rate and structure, the proportion of crop residue returned to rice field, chemical fertilizer application rate, water management and so on. According to Chinese rice-planted planning and the established agricultural cultivation changes in rice production from 1950s-1990s, annul organic carbon to Chinese rice fields was estimated;Combined the agricultural cultivation in rice-production database between 1950s-1990s with other input parameters into CH4MOD, the methane emissions from Chinese rice fields can be estimated during 1955-2005.The results showed that the annual organic carbon input to rice fields has been increasing in the past 50 years. The average organic carbon inputs is 2.96,3.00,3.41, 3.64,3.83 and 4.28 t Cha-1 in the 1950s,1960s,1970s,1980s,1990s and 2000s separately. The input from crop residue and roots has been increasing, with the proportion accounting for the total organic carbon input increased from 20.4% in the 1950s to 61.7% in the 2000s;while the input from farmyard manure has been decreasing, with the proportion accounting for the total input decreased from 77.6% in the 1950s to 36.1% in the 2000s;the organic carbon input from green manure accounting for the total input remained 1.5-8.5%, taking on a increase and then downward trend. At the spatial distribution, the high value of organic carbon input to Chinese rice fields mainly concentrated in the central and southern China, keeping from 2.88-5.61 t Cha-1, while the lower-level organic carbon input is located in the northeast and northwest region, ranging from 1.11-2.47 t Cha-1 during 1950s-2000s.The methane emissions from Chinese rice fields increased in general over the fifty years. The quantities of CH4 emission were estimated to be 3.18±0.53,4.71±0.27,5.22±0.24 and 5.79±0.34Tg/yr in the 1960s,1970s,1980s and 1990s, respectively. The mean amount of CH4 emission from 2000 to 2005 was estimated to be 6.25±0.36Tg/yr. Rapid increase occurred in the period 1960-1975 with a mean growth rate of 167Gg per year, while the growth rate decreased from 1976 to 2005 with 54Gg per year. Higher CH4 emissions was distributed in Hunan, Hubei, Jiangxi, Guangdong, Guangxi, Jiangsu and Anhui Province, accounting for approximately 73% of the national total CH4 emission in rice fields. Methane emissions from each rice-growing region in China have increased since 1950s. The increase of methane emission from Central and Southern China slowed down since 1970s. Methane emission in northeast China was estimated to have increased significantly since the early 1980s,which is mainly attributed to an expansion of rice cultivation and increase of air temperature.In this study, database of agricultural cultivation in rice production in China during 1950s-1990s was established through large samples of farmer survey. Based on the database set up, combining with the characteristic of rice cropping regime, the annual organic carbon input to Chinese rice fields was estimated. On the foundation of methane emission estimation model and the support of GIS technology, grid-based datasets and CH4MOD were combined to simulate methane emission from Chinese rice fields in long time series and its temporal, spatial variation. The study answers the methane emissions from Chinese rice fields in the past, which not only helps to evaluate the role the Chinese rice production have played in regional methane emission, but also provide scientific support for the making effective countermeasures concerning agricultural greenhouse gases mitigation.更多还原