降水变化对黄土高原旱作冬小麦农田土壤温室气体排放的影响

发布时间：2018-06-06 20:40

本文选题：温室气体排放 + 降水变化　；参考：《西北大学》2015年硕士论文

【摘要】：降水作为旱作农田生态系统的主控因子,不仅影响着作物生产力的形成过程,同时对农田温室气体(CO2、CH4和N2O)排放及相应的综合增温潜势具有重要影响。本研究以黄土高原冬小麦田生态系统为对象,基于人工降水模拟系列实验,采用静态箱-气相色谱法田间原位系统研究了降水变化(降水量、降水频率和季节分布)对土壤C02、CH4和N2O通量变化的影响规律,主要结果如下：1、不同降水量对土壤CO2和CH4排放的影响。试验设计在冬小麦拔节期和休闲期进行人工模拟降水试验,观测降水后0-72h土壤CO2和CH4排放对不同降水量(1、3、8、16和32mm)的短期响应。结果表明：降水后土壤CO2排放速率随降水量的增大而增强,1-16mm降水在降水后4h出现土壤CO2排放峰值,而32mm降水土壤C02排放峰值出现时间滞后了4h。土壤CO2排放速率(Rpi)脉冲强度随降水量(P)增大呈指数增加(拔节期：Rpi=0.97P0.09, R2=0.5, P0.05;夏闲期：RPi=1.07P0.09, R2=0.98, P0.01).降水后72h土壤CO2累积释放量(CO2-P)与降水量呈线性相关(拔节期：CO2-P=0.03P+5.99,R2=0.58, P0.05;夏闲期：CO2-P=0.11P+6.04, R2=0.86, P0.01)。土壤CO2排放温度敏感性系数(Q10)和降水量之间存在二次曲线关系(拔节期：Q10=-0.005P2+0.18P+1.47,R2=0.37, P0.05;夏闲期：Q10=-0.007P2+0.21P+1.18,R2=0.95,P0.01)。与较小降水量相比,较大的降水量能增加土壤CO2排放但会推迟土壤CO2排放峰值出现时间。模拟降水后,低降水量(1-8mm)处理土壤CH4排放通量为波动变化,高降水量(16和32 mm)处理呈单峰型的变化。降水后72 h土壤CH4累积通量(CH4-C)与降水量(P)呈显著线性正相关(冬小麦拔节期：CH4-C=2.45P-6.09, R2=0.92, P0.01;夏闲期：CH4-C=2.43P-4.73, R2=0.91, P0.01)。相关分析表明,降水后土壤CH4通量与土壤含水量和土壤微生物量碳含量显著相关,而与土壤温度不相关。少量降水(1-8mm)可以在短期内促进旱作农田土壤对CH4的吸收,加强土壤作为大气CH4汇的强度,然而这种促进作用也会随降水量的增大和降水的下渗而削弱。较大降水(16和32 mm)可以刺激土壤产甲烷菌活性促进CH4释放,在短期内使旱作农田土壤由单一的汇功能转变为汇源双重功能。2、夏闲期不同降水频率对土壤CO2和CH4排放通量的影响。试验设计在冬小麦夏闲期(60天)模拟每隔5天(I5)、10天(I10)和20天(I20)三个降水频率的降水,模拟降水总量(控制为240mm)不变,观测了不同降水频率降水后土壤CO2和CH4的通量特征。结果表明：不同频率I5、I10和I20处理单次降水后土壤CO2排放速率是降水前的4-5倍表现出显著的‘Birch effect".随着降水次数的增加降水事件对土壤CO2排放的激发效应被削弱,降水频率越高削弱的越明显,且I5和I10土壤CO2累积释放量高于I20处理。土壤CO2通量和土壤水热因子呈非线性的关系,土壤水分解释了43%-76%的土壤CO2通量变化,且二者的相关性随降水间隔的增加而增强,Q10值随降水间隔的增加而降低,说明高频率降水处理土壤CO2通量的温度敏感性更高。高频率降水(I5处理)可以增强土壤氧化吸收大气CH4的速率,增强大气甲烷汇的功能。低频率降水(单次降水量提高)可以使冬小麦田在短时间内由大气CH4的汇转变为大气CH4的源。旱地农田土壤CH4通量强度受温度和水分的共同影响,不同降水频率的降水对土壤水分和温度的影响改变了土壤吸收氧化和产生CH4的过程,甚至改变了土壤对大气CH4的源汇功能。3、作物关键生育期增加降水对土壤温室气体排放和净综合增温潜势的影响。试验设计在自然降水的基础上再分别在冬小麦生育关键时期拔节期(5月8日)和孕穗期(5月28日)增加0mm (10)、8mm (18)、16mm (116)、32mm (132)和64mm(I64)的降水,探讨增加降水对土壤CO2、 CH4和N2O通量及其综合增温潜势和作物产量的影响。试验结果表明：旱作冬小麦田为大气CO2和N2O的排放源,是大气CH4的汇。生育关键期增加降雨使CO2的排放量增加了2.50%-9.07%,N2O的排放量增加了4.33%-11.68%,对CH4的排放量无显著影响。与IO相比,I8、I16、I32和I64处理冬小麦产量分别增加了24.46%、28.93%、31.70%和34.01%(p0.05),地上生物量分别提高了13.74%、18.99%、24.36%和25.11%。生育期增加降水降低了麦田NGWP和GHGI。增加降水不仅强化了土壤CO2和N2O源的特征,同时降水增强了土壤水分和养分有效性提高了作物产量,产生的补偿效应使麦田由温室气体的源转为汇。
[Abstract]:As the main controlling factor of the drought cropland ecosystem, precipitation not only affects the formation process of crop productivity, but also has an important influence on the emission of greenhouse gases (CO2, CH4 and N2O) and the corresponding comprehensive temperature increasing potential. The effects of precipitation changes (precipitation, precipitation frequency and seasonal distribution) on the changes of soil C02, CH4 and N2O flux were studied by the state box gas chromatography in situ system. The main results were as follows: 1, the effects of different precipitation on the CO2 and CH4 emission of soil. Experimental design was designed in the jointing and leisure periods of winter wheat at the jointing and leisure periods. The short-term response of 0-72h soil CO2 and CH4 emission to different precipitation (1,3,8,16 and 32mm) was observed after precipitation. The results showed that the CO2 emission rate of soil increased with the increase of precipitation, and the CO2 emission peak of 4H appeared after precipitation in 1-16mm after precipitation, while C02 discharge time of 32mm precipitation soil lagged behind the velocity of 4h. soil. Rpi pulse intensity increased exponentially with the increase of water reduction (P) (jointing stage: Rpi=0.97P0.09, R2=0.5, P0.05; summer leisure period: RPi=1.07P0.09, R2=0.98, P0.01). The cumulative release amount of CO2 in 72h soil (CO2-P) was linearly correlated with precipitation after precipitation. 1). There are two curves between the temperature sensitivity coefficient of soil CO2 emission (Q10) and precipitation (jointing period: Q10=-0.005P2+0.18P+1.47, R2=0.37, P0.05; summer leisure period: Q10=-0.007P2+0.21P+1.18, R2=0.95, P0.01). Compared with the smaller precipitation, the larger precipitation can increase the soil CO2 emission but will delay the occurrence of the peak value of the soil CO2 emission. After simulated precipitation, low precipitation (1-8mm) treated soil CH4 emission flux was fluctuant, high precipitation (16 and 32 mm) showed a single peak change. The CH4 cumulative flux (CH4-C) in 72 h soil after precipitation was significantly linear and positive correlation with precipitation (P) (CH4-C=2.45P-6.09, R2=0.92, P0.01; summer leisure period: CH4-C=2.43P-4.73, R2=0.91, P0.01). The correlation analysis shows that the soil CH4 flux after precipitation is significantly related to soil water content and soil microbial biomass carbon content, but not related to soil temperature. A small amount of precipitation (1-8mm) can promote the absorption of CH4 in dry farmland soil in a short time, and strengthen the soil as the intensity of atmospheric CH4 sink, however, this effect will also follow. The precipitation (16 and 32 mm) can stimulate the activity of methanogenic bacteria in the soil to promote the release of CH4. In the short term, the soil from a single sink function is transformed from a single sink function to the dual function of.2, and the effects of different precipitation frequencies on the soil CO2 and CH4 flux in the summer leisure period are designed in winter wheat. The summer leisure period (60 days) simulated precipitation at three precipitation frequencies of 5 days (I5), 10 days (I10) and 20 days (I20). The total amount of simulated precipitation (240mm) was unchanged. The flux characteristics of CO2 and CH4 in soil after precipitation of different precipitation frequencies were observed. The results showed that the rate of CO2 emission of soil CO2 was 4-5 times as high as that of I5, I10 and I20 at different frequencies after single precipitation. The results show a significant 'Birch effect'. With the increase of precipitation times, the effect of precipitation on soil CO2 emission is weakened, the higher the precipitation frequency is, the more obvious the weakening of the precipitation frequency, and the cumulative release of CO2 in the I5 and I10 soils is higher than that of I20 treatment. The soil CO2 flux has a non linear relationship with the soil water heat factor, and the soil moisture explains the 43%-76% soil. The CO2 flux of the soil increased with the increase of the precipitation interval, and the Q10 value decreased with the increase of the precipitation interval, indicating that the temperature sensitivity of the CO2 flux in the high frequency precipitation treatment was higher. The high frequency precipitation (I5 treatment) could enhance the rate of the oxidation absorption of the atmospheric CH4 and enhance the function of the atmospheric methane sink, and the low frequency drop. The water (increase of single precipitation) can make the winter wheat field change from the atmospheric CH4 sink to the source of CH4 in a short time. The CH4 flux intensity in the dry farmland soil is influenced by the temperature and water. The influence of precipitation on soil moisture and temperature at different precipitation frequency changes the process of soil absorption and oxidation and the production of CH4, or even the soil. The origin and sink function of the soil to the atmospheric CH4,.3, the effect of increasing precipitation on the greenhouse gas emission and the net comprehensive temperature increasing potential in the critical growth period of the crop. Based on the natural precipitation, the experimental design increased 0mm (10), 8mm (18), 16mm (116), 32mm (132) and 64mm in the jointing period (May 8th) and the booting stage (May 28th) of the winter wheat breeding. (I64) precipitation to explore the effect of increasing precipitation on soil CO2, CH4 and N2O flux and its comprehensive temperature increasing potential and crop yield. The experimental results show that the dry winter wheat field is the source of CO2 and N2O in the atmosphere and the sink of CH4 in the atmosphere. The increase of rainfall in the critical period of fertility increases the emission of CO2, and the emission of N2O increases by 4.33%-11.. 68%, there was no significant effect on CH4 emissions. Compared with IO, I8, I16, I32 and I64 increased the yield of Winter Wheat by 24.46%, 28.93%, 31.70% and 34.01% (P0.05). The aboveground biomass increased respectively in 13.74%, 18.99%, 24.36% and 25.11%. growth periods. At the same time, precipitation enhanced soil water and nutrient availability, and increased crop yield. The compensation effect resulted in the conversion of wheat field from greenhouse gas to sink.
【学位授予单位】：西北大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S512.11;S154.1

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