不同管理措施下农田土壤温室气体排放对降水的响应

发布时间：2018-11-08 19:09

【摘要】：降水变化是影响土壤温室气体排放的重要因素,而不同的管理措施,如秸秆覆盖、施肥以及作物的种植等也都对农田土壤温室气体的排放起到一定的影响作用,为了解不同管理措施下降水对农田土壤温室气体的影响,本研究进行了夏闲期的盆栽模拟降水及生育期的小麦田模拟降水,运用静态箱-气相色谱法对三种温室气体(CO2、CH4、N2O)对不同管理措施下降水的响应规律进行了相应的研究,主要结果如下:1)通过盆栽降水试验和生育期降水量试验,发现较低含水率时,土壤呼吸和N2O均表现为较低的排放,而CH4则表现为被吸收。降水可以有效地促进土壤呼吸,也有将土壤由CH4的汇转变为CH4的源的趋势,同时降水还可以促进土壤的反硝化作用,促进N2O的排放。但不同降水量对三种温室气体影响的方式有所不同,总的来看,降水量较低时(0-8mm),三种温室气体会在1-4h内达到排放峰值,而高降水量降水会对排放峰产生明显的延后效应。2)在盆栽和生育期降水试验均发现,土壤呼吸在各降水量时均和土壤温度有着显著地关联,只是在低含水率时,土壤温度是土壤CO2排放速率的主要控制因素,在土壤水分含量较高时温度和水分共同影响土壤呼吸的速率;对于CH4来说,排放只受土壤水分的控制,与土壤温度无明显关系;而对于N2O,低含水量时土壤N2O的排放同土壤温度有着明显的关系,但在增加降水后,N2O的排放与土壤水分和温度的关系则比较复杂,还需要进一步探究。3)盆栽试验表明,不同的土壤处理措施对土壤温室气体的排放影响不一。秸秆覆盖可以促进土壤CO2和N2O的排放;而在低降水量时,秸秆覆盖对土壤CH4的排放有减弱的趋势,随着降水量的增大,这种趋势会被水分的升高而弥补,从而显示为促进CH4的排放,即在高降水量时,CH4排放的主要影响因素为水分,但排放量仍低于无秸秆覆盖处理。同时,施氮可以减少土壤CO2排放,降低土壤呼吸的温度敏感性,极大地增大N2O排放的趋势,但对CH4的排放无明显影响。对比不同降水量下的三种温室气体排放量,施氮条件下降水会极大增大N2O的排放,而对CO2和CH4的排放趋势无较大影响。4)生育期两次降水量试验表明,高降水量处理均会不同程度的延迟土壤温室气体的出峰时间:0-16mm降水量的土壤呼吸在4h到达最大值,而32mm高降水量处理则会延迟4h;CH4和CO2的出峰规律相似,0-8mm为降水后4h,16、32mm为降水后8h;而对于N2O,降水后峰值出现的时间为:0-8mm降水土壤N2O排放最大值出现在8小时,而16mm为12-24h,32mm为48小时。与此同时,反复的干湿交替会降低CO2和N2O的排放,促进CH4的释放。
[Abstract]:The change of precipitation is an important factor that affects the greenhouse gas emission of soil, and different management measures, such as straw mulching, fertilization and crop planting, also play a certain role in the greenhouse gas emission of farmland soil. In order to understand the effect of different management measures on greenhouse gases in farmland soil, pot simulated precipitation during summer free season and simulated precipitation in wheat field during growth period were studied. Three greenhouse gases (CO2,CH4,) were determined by static box gas chromatography. The main results are as follows: 1) through pot precipitation experiment and growth period precipitation experiment, we found that the water content is low. Soil respiration and N _ 2O emission were lower, while CH4 was absorbed. Precipitation can effectively promote soil respiration and change soil from sink of CH4 to source of CH4. Precipitation can also promote denitrification and N2O emission. However, the effects of different precipitation on the three greenhouse gases are different. Generally speaking, when the precipitation is low (0-8mm), the three greenhouse gases will reach the peak emission within 1-4 hours. However, precipitation with high precipitation has a significant delayed effect on the emission peak. 2) in both pot and growth stage precipitation experiments, soil respiration is significantly correlated with soil temperature at different precipitation levels, but only at low moisture content. Soil temperature is the main controlling factor of soil CO2 emission rate. When soil moisture content is high, both temperature and moisture affect soil respiration rate. For CH4, the emission was only controlled by soil moisture and had no obvious relationship with soil temperature. However, for N _ 2O, the emission of N _ 2O from soil under low water content has a significant relationship with soil temperature, but the relationship between N _ 2O emission and soil moisture and temperature is more complicated after increasing precipitation. 3) the pot experiment shows that the relationship between N _ 2O emission and soil temperature is more complex. Different soil treatment measures have different effects on greenhouse gas emissions. Straw mulching could promote the emission of CO2 and N2O from soil. However, at low precipitation, straw mulch has a tendency to weaken soil CH4 emissions. With the increase of precipitation, this trend will be compensated by the increase of water content, which shows that it can promote the discharge of CH4, that is, when the precipitation is high, The main influencing factor of CH4 emission was moisture, but the discharge was still lower than that without straw mulching. At the same time, nitrogen application can reduce soil CO2 emissions, reduce the temperature sensitivity of soil respiration, greatly increase the trend of N 2O emissions, but have no significant effect on CH4 emissions. Compared with the three kinds of greenhouse gas emissions under different precipitation, precipitation increased the emission of N2O greatly under the condition of nitrogen application, but had no great effect on the emission trend of CO2 and CH4. The peak time of soil greenhouse gas was delayed to some extent by high precipitation treatment: the soil respiration of 0-16mm reached the maximum at 4 h, while that of 32mm high precipitation delayed 4 h; The peak of CH4 and CO2 were similar, 0-8mm was 4 h after precipitation, 1632 mm was 8 h after precipitation, and for N 2O, the maximum time of N2O emission from 0-8mm precipitation soil appeared at 8 hours, while that of 16mm was 12-24 h and 32mm was 48 hours. At the same time, repeated dry-wet alternation can reduce the emission of CO2 and N 2 O, and promote the release of CH4.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S154.1

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