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干旱区绿洲棉田土壤CO2/N2O排放特征及减排潜力研究
俞永祥
学位类型博士
导师赵成义
2017-05-01
学位授予单位中国科学院大学
学位授予地点新疆乌鲁木齐
学位专业理学博士
关键词绿洲棉田 土壤co2/n2o排放 地膜覆盖 施肥 硝化抑制剂
摘要农田生态系统作为温室气体排放源之一在全球碳氮循环中起到了重要作用。新疆绿洲农田是干旱区典型的灌溉农田生态系统,受人类活动的强烈影响,农田土壤CO2/N2O排放强度远高于同区域的其他生态系统,研究绿洲农田土壤CO2/N2O排放特征及调控措施具有重要的理论及实践意义。论文以干旱区绿洲棉田为研究对象,采用静态箱-气相色谱法阐明了绿洲棉田土壤CO2/N2O排放特征及主要影响因素,假设覆膜增加了土壤CO2排放、减少了土壤N2O排放,施肥促进了土壤CO2/N2O排放;大田和培育试验相结合探明了不同管理方式下棉田土壤CO2/N2O减排潜力,假设分期施肥降低了土壤CO2/N2O排放;基于DNDC模型提出了实现绿洲棉田土壤CO2/N2O减排的优化管理模式,预测了未来气候变化对棉田土壤CO2/N2O排放的影响,为干旱区绿洲农业生产管理和温室气体减排提供科学依据。主要结论如下:(1)绿洲棉田土壤CO2排放高峰期发生在棉花生长的花铃期(7-8月)。土壤CO2排放速率随温度升高呈指数增加,过高或过低的土壤含水量下土壤CO2排放速率均较低。全生育期内,58-77%的土壤N2O排放发生在滴灌施肥期(7-8月),土壤温度、湿度和矿质氮含量增加均利于土壤N2O产出与排放。较高的土壤温度和滴灌施肥措施可增加土壤硝化和反硝化细菌活性,利于土壤硝化和反硝化过程产出和排放N2O。(2)覆膜对土壤CO2和N2O排放的影响机制不同。覆膜保温保湿促进棉花生长,利于自养呼吸产出的CO2通过膜间土壤排放到大气中,土壤CO2排放量可增加7-9%。覆膜既能提高植物氮素利用效率减少土壤N2O产出,也可抑制土壤N2O传输利于N2O还原,全生育期土壤N2O排放量可减少19-28%。(3)施肥显著促进土壤CO2/N2O排放。土壤CO2排放量随施氮量增加呈线性增加,可能是施肥促进了棉花生长,增强了土壤微生物活性,利于土壤自养呼吸和异养呼吸产出和排放CO2。施氮肥为土壤微生物的硝化和反硝化过程提供底物,土壤N2O排放量随施氮量增加呈线性增加。观测期内,土壤N2O排放系数范围为0.28-0.70%,表明采用IPCC推荐的N2O排放系数(1%)会高估新疆干旱区绿洲膜下滴灌棉田土壤N2O排放量约一倍左右。 (4)培育试验中,分期施肥和施用硝化抑制剂均有效减少了土壤CO2/N2O排放,但分期施肥方式降低了施用硝化抑制剂下土壤N2O减排效率。田间试验中,施用硝化抑制剂没有显著影响滴灌施肥棉田土壤CO2排放,但抑制土壤铵态氮转化为硝态氮的硝化过程,土壤N2O排放量可减少23-42%。施用硝化抑制剂对棉花产量没有显著影响,降低土壤N2O排放产生的碳交易收益(6-11 RMB ha-1)远低于硝化抑制剂的成本投入(150 RMB ha-1),该方法不适用于减少新疆绿洲棉田土壤CO2/N2O排放。(5)DNDC有效模拟了覆膜对棉花生长和土壤CO2/N2O排放的影响。优化管理模式下模型模拟的结果表明,覆膜使棉田灌溉量和施氮量分别减少120 mm和10 kg N ha-1,使棉花产量、土壤CO2排放量和土壤有机碳增量分别增加了9%、10%和4%,使土壤N2O排放量减少了4%。不同气候变化情景下的模拟结果表明,未来气候变化使膜下滴灌棉田的棉花产量、土壤CO2排放量和作物经济收益分别增加了5-6%、7-9%和9-10%,土壤N2O排放量和棉田土壤有机碳增量分别减少了9-15%和21-29%。总之,未来气候变化利于新疆绿洲棉花增产,对土壤CO2/N2O排放产生的增温效应影响不大。
其他摘要Agricultural soils are important source of greenhouse gas emissions that contributes to global warming. In the arid region of China, soil CO2/N2O emissions in agricultural systems are greater than in natural ecosystems, because irrigation and fertilizer application increases the growth of agricultural crops and therefore stimulates soil CO2/N2O emissions. The objects were to characterize the temporal variation of soil CO2/N2O emissions in Aksu oasis cotton field and analyze the relative influence factors in explaining the variation of soil CO2/N2O emissions based on chamber method, we hypothesized that plastic mulching increase soil CO2 emission but decrease soil N2O emission, the application of nitrogen (N) fertilizer increase soil CO2/N2O emissions; assess the potentials of reducing soil CO2/N2O emissions through changing agricultural management practices, we hypothesized that split fertilization decrease soil CO2/ N2O emission; evaluate the best management practices to reduce soil CO2/N2O emissions and predict soil CO2/N2O potential emissions and crop production under future climate change scenarios using the DNDC model. (1) The highest soil CO2/N2O emissions were observed during the boll-forming stages of cotton (July to August). Soil temperature and moisture are two major abiotic factors controlling soil CO2 emission. Soil CO2 emissions increase exponentially with increasing temperature, but showed two distinctive phases with respect to soil water content, with CO2 emission increase with increasing soil water content whereas excessive soil moisture depresses soil CO2 emission. The split application of N fertilizer along with irrigation induced several peaks in the N2O emissions, which coincided with high temperature, WFPS and mineral N contents. During the fertigation period, the cumulative N2O emissions from the fertilized soil accounted for 58-77% of the total N2O emissions in the observation period.(2) The application of plastic film significantly influenced soil CO2/N2O emissions from the cotton field. Plastic mulching enhanced the production of CO2 via autotrophic respiration through increased the growth of cotton, and then increased cumulative CO2 emissions by 7-9%, which mainly released from the furrow soils. The application of plastic film reduced N2O emission by 19-28% via both enhanced the N2O consumption through restricted the N2O diffusion process, and limited the N2O production through reduced soil mineral N content.(3) N fertilization significantly increased soil CO2/N2O emissions from the cotton field. The cumulative CO2 emissions increased linearly with N fertilizer rates, because plant production and soil mineral N content increased following the application of urea, resulting in enhanced root and heterotrophic respiration rates. The cumulative N2O emissions increased linearly with N fertilizer rates, because the addition of N fertilizer to the agricultural soils provides substrates for microbial nitrification or denitrification to produce N2O. Across the two fertilizer rates, the multi-year mean emission factor was 0.46% (ranging from 0.28% to 0.70%) during the observation period, indicating that the IPCC default value of 1% may not be suitable for this agricultural system. (4) The results of incubation experiment showed both split fertilization and the application of nitrapyrin efficiently reduced soil CO2/N2O emissions, while split fertilization inhibited the efficiency of nitrapyrin to reduced N2O emission. In the field experiment, the application of nitrapyrin did not significantly affect soil CO2 emission, but significantly reduced cumulative N2O emission by 23-42% through inhibited the process of nitrification. However, because the application of nitrification did not significantly increased lint yield, while the income of carbon trading through reducing soil N2O emission (6-11 RMB ha-1) was lower than the input of nitrapyrin (150 RMB ha-1). Therefore, the use of nitrapyrin did not suitable to reduce soil CO2/N2O emissions in the fertigation agricultural system.(5) The DNDC model performed well in simulating temporal variations in soil CO2/N2O emissions and plant growth during the observation period, and was able to simulate the effects of plastic mulching on soil CO2/N2O emissions and crop yield. Based on the best management practice scenarios, our results showed plastic mulching reduced irrigation by 120 mm and N fertilizer rate by 10 kg N ha-1, respectively; increased crop yield, soil CO2 emission and soil organic carbon by 9%, 10% and 4%, respectively; reduced soil N2O emission by 4%. Overall, our results showed plastic mulching bring economic income by 1453 RMB ha-1 without influencing soil greenhouse gas emissions. Compared with the baseline scenario, future climate change significantly increased lint yield, soil CO2 emission and income by 5-6%, 7-9% and 9-10%, respectively; reduced soil N2O emission and soil organic carbon by 9-15% and 21-29%, respectively. Overall, our results showed future climate change was benefit for agricultural production without influencing soil CO2/N2O emissions.
学科领域自然地理学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14779
专题研究系统_荒漠环境研究室
作者单位中国科学院新疆生态与地理研究所
推荐引用方式
GB/T 7714
俞永祥. 干旱区绿洲棉田土壤CO2/N2O排放特征及减排潜力研究[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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