【作者】 王乐；

【导师】 李凤民；

【作者基本信息】 兰州大学 ， 生态学， 2013， 硕士

【摘要】 近年来,全球温度的不断上升,极端天气气候事件发生频率的不断增加,使得人类开始更加关注自身的生存环境以及人类活动对生态环境所带来的巨大影响。大气中温室气体的不断增加是全球变暖和气候变化的主因,因此,探索不同类型人为排放源的排放机理,对控制人为温室气体的排放具有重要意义。农田生态系统是人类食物和工业原料的重要来源,亦是温室气体的重要排放源。地膜覆膜作为一种重要的旱作农业技术,应用十分广泛,但对其温室气体氧化亚氮的排放研究尚未深入。本研究立足我国较为典型的早作农业区,以玉米为研究对象,研究了施用氮肥和地膜覆盖处理对农田氧化亚氮排放特征、排放量和地下气体浓度的影响。使用静态箱-气象色谱法,测定了氧化亚氮的气体浓度,并计算不同处理的氧化亚氮通量。结合测定的土壤速效氮含量、地上生物量和土壤温度数据进行进一步的分析,可得出如下主要结论如下：1、本实验中,在测定不同处理氧化亚氮地下气体浓度和地上排放量的同时,还对地上生物量的变化进行了持续的测定。结果表明：不论是在覆膜还是不覆膜条件下,施用氮肥均对玉米地上生物量的积累具有重要的促进作用,该作用在玉米生长的后期显现的较为明显。地膜覆盖能显著促进玉米地上生物量的积累,其中,双垄沟覆膜施肥处理(DRM)在植株生长的初期显著地促进了玉米植株地上生物量的积累,其地上生物量显著高于齐垄覆膜施肥(M1N1)等其余处理,显示了双垄沟覆膜技术所具有的独特优势。2、对氧化亚氮通量的三次日变化监测发现：典型晴朗天气条件下(6月14-15日,8月28-29日),氧化亚氮的通量变化呈现比较规律的双峰曲线,即于正午12：00左右达到第一次排放峰,随后排放量下降,并于凌晨3：00左右到达第二次排放峰。在阴天并伴有短时小雨天气条件下,氧化亚氮的排放并无明显的排放峰,而是在12：00-15：00左右出现一个排放低点。3、对氧化亚氮气体地下浓度的监测发现：5月20日第一次采集地下气体时,M1N1处理0-l0cm氧化亚氮浓度为747.3138ppb,显著高于DRM处理的539.4266ppb,而DRM处理的氧化亚氮浓度又显著高于其余处理,其余各处理间氧化亚氮浓度并无显著差异。此后各个处理的0-10cm氧化亚氮浓度均迅速下降,至6月15日左右所有处理的氧化亚氮浓度均保持在325-350ppb之间,并维持在这一水平直至收获。4、对氧化亚氮通量的监测发现：观测期内,氧化亚氮通量并无明显的季节性变化规律。整体上来看,所有处理的氧化亚氮浓度均呈现先下降,到达最低后又开始缓慢上升,并于收产时到达第二个排放高点,收产一周后所有处理的氧化亚氮排放量迅速下降。6月9日开始第一次通量测定时,DRM处理氧化亚氮通量显著高于覆膜不施肥的M1N0处理和不覆膜施肥的MON1处理。6月15日时,DRM处理氧化亚氮通量显著高于其余各个处理。此后,各个处理间氧化亚氮通量的差异逐步缩小,各个处理间的排放量较为接近。5、影响氧化亚氮排放的各个因素间的相关性分析：对土壤0-l0cm温度与氧化亚氮通量间的相关性分析发现,晴朗天气条件下,两者间呈现显著的线性负相关关系。而在阴雨条件下,两者间呈现显著的指数型负相关关系。对土壤0-l0cm温度和氧化亚氮浓度间的相关性分析发现,温度与氧化亚氮浓度间均存在显著的指数型或者线性的正相关关系。20-30cm处的氧化亚氮浓度与氧化亚氮通量间均呈现显著的正相关关系。整个观测期内的土壤速效氮浓度与地下气体浓度间呈现显著的指数型相关关系。更多还原

【Abstract】 Rising global temperature and frequently occurred extreme weather-climate event arouse people’s concern towards the tremendous impact human caused on global environment change. Numerous researches on climate change have proved that increasing greenhouse gases concentration in atmosphere account for the global warming occurred. Thus, exploring greenhouse gases emission mechanism is vital for the control of human-induced emission source. Farmland supplies human being with food and industrial material, but an important gases emission source also. Plastic mulching is a technique which has been widely adopted in rainfed farming areas, but research on greenhouse gases emission of fields with plastic mulching, however, is not deeply investigated. In the present study, maize field with plastic mulching in typical rainfed area-loess plateau was chosen to investigate the effect of plastic mulching on nitrous oxide flux, diurnal variation and concentration in different soil depth. Nitrous oxide (N2O) concentration was determined using chamber-gas chromatography method, and flux was then calculated. Combining with other data obtained, such as aboveground biomass, soil temperature and soil ammonium and nitrate content, further analysis was conducted. Some major conclusion can be drawn as follows:1. Both urea application and plastic mulching stimulate maize aboveground biomass accumulation. But the different is that urea application reveal its stimulate effect at late growth stage. Treatments with plastic mulching exhibit its stimulate effect at the very beginning of the growth stage. In particular, the treatment, two ridges and furrow mulched by plastic film with urea application (DRM), present its advantage over other treatments, both mulching and non-mulching.2. N2O flux diurnal variation showed different pattern according to the weather condition. In typical sunny days (June14th-15th and August28th-29th), soil N2O flux showed a two-peak curve, with one flux peak around12:00and the other around3:00. In a cloudy and rainy day, soil N2O flux reached the lowest point at around12:00-15:00and showed no flux peak.3. Soil N2O concentration monitoring result showed that:on May20th, the first soil N2O concentration determination, N2O concentration in0-10cm ridge soil of the treatment alternating ridges and furrows mulched by plastic film with urea application (MINI) was747.3138ppb, which is significantly higher than DRM (539.4266ppb). The concentration of DRM is higher than all other treatments left with a significance at p<0.05. Henceforth N2O concentration in0-10cm soil decreased gradually. Around June15th, all treatment kept an N2O concentration about325-350ppb, and kept at this level until harvesting.4. N2O flux was monitored in partial of the growth period. No seasonal variation was observed in the test period. On the whole, N2O flux of all treatments decreased gradually until reached the lowest point, afterwards, flux of all treatments increased and reached the highest point around harvesting. A week after harvesting, N2O flux decreased sharply. On June9th, the first N2O flux determination, DRM N2O flux was significantly higher M1N0and M0N1. On June15th, DRM N2O flux was significantly higher than all the other treatments. Afterwards, N2O flux difference among treatments diminished.5. Correlation analysis between0-10cm soil temperature and soil N2O flux proved that:in typical sunny days, soil temperature showed a significant negative linear correlation with N2O flux. While, in cloudy and rainy day, soil temperature showed a significant negative exponential correlation with N2O flux. Correlation analysis between0-10cm soil temperature and20-30cm soil N2O concentration proved that:soil temperature showed a significant positive linear or exponential correlation with20-30cm soil N2O concentration.20-30cm soil N2O concentration showed a significant positive correlation with N2O flux. During the test period, plant available nitrogen content (soil nitrate and ammonium content) showed a significant exponential correlation with20-30cm soil N2O concentration.更多还原