【作者】 陈卫卫；

【导师】 张友民；

【作者基本信息】 吉林农业大学 ， 植物学， 2007， 硕士

【摘要】 氧化亚氮（N₂O）是目前了解较少而又非常重要的温室气体，它具有产生温室效应和破坏平流层臭氧的双重作用。稻田生态系统是大气中N₂O一个重要的生物排放源。中国是水稻生产大国，稻田生态系统对温室效应的影响是人们关注的焦点之一。国内研究主要集中在南方的稻作区，而对于我国东北的稻作区研究较少，尤其对我国东北重要的粮食产区—三江平原稻作区N₂O排放仅有零星观测。本研究主要以位于黑龙江省三江平原的中国科学院沼泽生态试验站为试验平台，于2004．11～2006．10连续两年对该地区寒地稻田生态系统N₂O排放进行了田间原位观测研究。研究了该地区稻田生态系统N₂O的排放特征及其影响因素；N肥施用对稻田生态系统N₂O排放的影响；水稻植株参与及不同种植密度下稻田生态系统N₂O的排放情况；并对该区稻田生态系统N₂O排放量进行了初步估算，为准确估计我国农田生态系统N₂O排放提供依据，从而为农业和环境的可持续发展提供科学依据。主要研究结果如下：1、三江平原稻田生态系统是N₂O排放源，观测期间稻田生态系统N₂O通量变化范围为-0.016～0.527mg·m^-2·h^-1。水稻生长季是N₂O排放的主要时期，平均通量为0.057±0.037mg·m^-2·h^-1，占全年N₂O排放总量的69.2％。非生长季N₂O排放显著减少，平均通量为0.016±0.007mg·m^-2·h^-1。但是由于非生长期时间很长，因此排放量也不容忽视，占全年N₂O排放总量的31.8％。2、三江平原稻田生态系统N₂O排放具有明显的季节变化、年际变化以及日变化特征。夏秋季节稻田生态系统N₂O排放大，冬春小，一般为夏／秋＞春＞冬，年际间有一定的差异。水稻生长期间，一般在施用基肥、追肥以及排水初期都会出现较明显的排放峰，同时在淹水期间如果出现明显土面落干情况，也会出现不同强度的排放峰。不同年份的淹、排水期的N₂O排放通量有一定差异，这主要取决于N₂O排放峰的大小和持续时间。但是由于大多数时间处于淹水状态，因此稻田淹水期的N₂O排放量显著高于排水期。按照水稻生育期划分，水稻分蘖期和长穗期N₂O排放速率和排放量均较高，而成熟收获期则占的比例最小。稻田生态系统N₂O排放在水稻非生长季节中明显减弱，冰冻期间N₂O排放微弱，冰雪覆盖时还出现吸收现象；冰雪融化期间，N₂O排放明显增加，因此也是一个不可忽视的排放时期。稻田生态系统N₂O排放日变化规律为白天高，晚上低。淹水期规律不明显，排水期稻田生态系统N₂O排放和气温和地温的变化趋势较为一致。3、水分管理是水稻生长期稻田生态系统N₂O排放季节变化的主要驱动因子，但是稻田生态系统N₂O排放和稻田积水深度则没有显著的相关性。温度是全年稻田生态系统N₂O排放的决定因子，同时也是稻田生态系统N₂O排放日变化的主要影响因子。4、氮肥是稻田生态系统N₂O排放的重要影响因子。化学氮肥的施用并未改变稻田生态系统N₂O的排放变化规律，只是排放峰的强度和数量有差异。低氮对稻田生态系统N₂O的排放影响较小，中高氮肥用量显著的增加了稻田生态系统N₂O的排放，随着氮肥用量的增加，N₂O的排放量也相应的增加。根据试验结果，三江平原稻田生态系统N₂O背景排放值分别为：水稻生长季节：1.192kgN·hm^-2，非生长季节：0.677kgN·hm^-2；全年：1.869kgN·hm^-2。氮肥用量为150kgN·hm^-2时，由氮肥产生的N₂O排放占生长期的比例和EF分别为41.29％和0.59％。氮肥用量为250kgN·hm^-2时，由氮肥产生的N₂O排放占生长期的比例和EF分别为57.52％和0.81％。综合考虑水稻产量和环境保护，氮肥用量为150kgN·hm^-2的处理较好。5、水稻植株生长对稻田生态系统N₂O排放影响明显，水稻叶面积和生物量和N₂O排放呈显著的乘幂相关关系。裸地土壤在稻田排水后排放强度很大，呈单峰排放型。水稻植株对氮素的大量吸收使稻田生态系统N₂O排放显著减少，稻田生态系统N₂O排放量仅为裸地土壤的1／4。不同种植密度下的稻田生态系统N₂O排放差异也较明显，稀植较常规种植下产量和生物量增加，同时N₂O排放降低。综合分析，16穴·m^-2的水稻种植密度最佳。6、结合三江平原稻田的种植面积，估算出了该地区稻田生态系统N₂O年交换速率为2.98kg·hm^-2·a^-1，年排放总量为3.17×10^-3Tg·a^-1。更多还原

【Abstract】 Nitrous Oxide （N₂O）, which is a very important greenhouse gases in the atmosphere but known less at present, could produce the greenhouse effects and destroy the stratospheric ozone. The paddy field ecosystem is an important biological source of the atmospheric N₂O emissions. China is a country of the rice with a big amount of production, so the impacts on greenhouse effects of paddy field ecosystem have become one of the focuses which people pay attention to closely. Most of studies of the greenhouse effects on paddy field ecosystem are carried out in the South of China and less in the Northeast of China, especially, the region of paddy field of Sanjiang Plain in Heilongjiang Province, which is the very important grain producing region of the Northeast of China.In order to understand of N₂O emissions from the paddy field ecosystem of Sanjiang Plain in Heilongjiang Province of Northeast of China, a field experiment was conducted in situ for two years in Sanjiang Plain Experiment Station of Wetland Ecology of Chinese Academy of Sciences （CAS）. In this study, the characteristic of N₂O emissions was investigated from the paddy field ecosystem, and the effects of N, crop plant, plant density and other environment factors on N₂O emissions were analyzed. Based on the area of paddy field in Sanjiang Plain, the amount of N₂O emissions was estimated from the paddy field ecosystem in this region, which offered the basis for estimating N₂O emissions accurately from farmland ecosystem and the scientific basis for sustainable development of agriculture and environment. The main conclusions of study are as follows:1. The paddy field ecosystem of Sanjiang Plain is the source of N₂O emissions, the range of N₂O fluxes is from -0.016 to 0.527 mg.m^-2.h^-1. The growth season is the main period of N₂O emissions from paddy field ecosystem and the average flux is 0.057±0.037 mg·m^-2·h^-1, which accounts for 69.2% of the total amount of N₂O emissions of the year. Compared with the growth period, N₂O flux reduced obviously in non-growth season and the average flux of N₂O is 0.016±0.007 mg·m^-2·h^-1, which is the 31.8% of the total amount of N₂O. Because of the long non-growth season, the N₂O emissions couldn’t be ignored either.2. The N₂O emissions have obviously seasonal, yearly and annual variations from the paddy field ecosystem in this region. The N₂O emissions in summer and autumn are more than that in spring and winter. In the growth season, it has obvious emissions after using base manure, topdressing and in initial stage of draining off water. If there is no water on the surface of soil in flooding period, it will have the discharge peak of different intensity. The N₂O fluxes have certain differences in different years in flooding and drainage period, which mainly depend on the amounts of emission peak and the duration, but most of the time in rice growth season is flooded, the amount of N₂O emissions in flooding period is more than in drainage period. According to the growth stage of rice, the N₂O flux and the amount of N₂O emissions in tillering stage and in earring stage is relative higher than that in other stages, The N₂O flux and amount of N₂O emissions in ripe-drainage stage is the lowest. The N₂O flux is obviously low in non-growth season, it discharges faintly in icy and presents the phenomenon of absorbing N₂O while the snow covering. When the ice and snow is melted, The N₂O emissions were increased obviously, so it could not be ignored during freezing and thawing. For diurnal variation of N₂O fluxes, it is always higher in daytime than in nighttime, there is no rule in the flooding stage, but it is identical with the air temperature and soil temperature variation in drainage stage.3. Seasonal variation of N₂O fluxes was controlled by the water management from paddy field ecosystem, but there is no prominent relevance between N₂O emissions and water depth of paddy field. The temperature is a decisive factor of N₂O emissions in different month of the year and it is the main influence factor for diurnal variation of N₂O fluxes.4. Manuring is an important influence factor for N₂O emissions. Using fertilizer could not change the rule of N₂O emissions, but there are certain differences for intensity and quantity of the peak of N₂O emissions. There is little effect on N₂O emissions in the low nitrogen treatment, but the N₂O emissions were increased obviously in middle and high nitrogen treatments. According to the experimental data, the background value of N₂O emissions from paddy field ecosystem in Sanjiang Plain is 1.192kgN·hm^-2 in the growth period, 0.677kgN’hm^-2 in the non-growth period and 1.869kgN.hm^-2 for the year respectively. When the nitrogen consumption is 150kgN·hm^-2, the proportions of N₂O emissions of the total amount in growth period caused by nitrogen and Effect Factor （EF） are 41.29% and 0.59% respectively. When the nitrogen consumption is 250kgN.hm^-2, the proportions of N₂O emissions of the total amount in growth period caused by nitrogen and Effect Factor （EF） are 57.52% and 0.81%. Considering rice output and environmental protection synthetically, the nitrogen consumption of 150kgN·hm^-2 applied is better than the others.5. The N₂O emissions of paddy field ecosystem were influenced obviously by the rice plant. There is an apparent relevance among the leaf area indexes （LAL）, over-ground biomass of rice and N₂O emissions. The N₂O emissions from bare soil are high in drainage period, and it presents the unimodal type. Compared with the bare soil, because of the nitrogen absorbed by the rice plant, the N₂O emissions were decreased obviously from paddy field ecosystem and its number is only one fourth of that from bare soil. There are obvious differences among different treatments of rice densities. Compared with normal planting density, the output and biomass of rice were increased and the N₂O emissions were decreased in appropriately sparse planting. Comprehensive analysis, the planting density of 16 caves per square meter is relatively better.6. According to the area of paddy field and the experimental data of N₂O emissions in Sanjiang Plain, the average N₂O flux and the total amount of N₂O emissions per year are 2.98 kg-hm^-2·a^-1 and 3.17×10^-3Tg·a^-1 respectively.更多还原