Knowledge Resource Center for Ecological Environment in Arid Area
| 温带沙质荒漠温室气体通量对水分、温度和氮沉降升高的响应 | |
| 其他题名 | Response of greenhouse gases fluxes to increasing precipitation, warming and nitrogen deposition in the temperate sandy desert |
| 岳平 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 刘学军 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 全球气候变暖已是不争的事实，而土壤温室气体排放失衡是造成全球气候变暖的最重要原因；在广袤的荒漠生态系统，土壤温室气体排放发生微弱的变化，都将可能对气候变化产生深远的影响。温带荒漠是全球最为脆弱的陆地生态系统之一，对降水格局改变、气候变暖和大气氮沉降升高的响应十分敏感，这将深刻影响荒漠系统土壤温室气体的排放。然而，由于荒漠土壤碳储量较低，关于土壤温室气体排放的研究一直缺乏足够的重视和系统的研究。本研究自2014年6月至2017年10月，以中国科学院新疆阜康荒漠生态国家野外科学观测研究站为试验平台，利用静态箱-气相色谱法，在古尔班通古特沙漠沙质荒漠典型区域，开展了降水、增温和氮沉降升高的多因子控制实验，研究温带沙质荒漠土壤主要温室气体通量 (CO2，CH4 和N2O) 对增加降水、气候变暖和氮沉降升高的响应特征与驱动机制，为IPCC准确评估干旱区温室气体排放清单提供重要的数据支撑和理论依据。本研究主要得出以下几方面的认识：荒漠土壤主要温室气体排放 (CO2，CH4 和N2O) 对降水事件的响应具有十分快速且短暂的特征，正如5 mm降水事件对三种主要的温室气体通量(CO2，CH4 和N2O)的影响也仅能持续2-3 天，这主要归因于土壤表层0-5 cm处水分的迅速变化。温带沙质荒漠土壤是大气N2O一个微弱的源，每年向大气中排放0.13 kg N2O-N ha-1，非生长季土壤N2O排放量占全年排放量的42.5%，这主要由含amoA功能基因的硝化微生物产生。增加30或60 kg N ha-1 yr-1显著的促进N2O排放55-132.5%，但是增加降水和气候变暖并没有改变土壤N2O年通量，尽管增加降水偶尔出现N2O排放峰，这主要受土壤氮素的限制。土壤N2O排放与土壤温度、土壤湿度和土壤铵态氮含量具有显著相关性，但结构方程模型发现土壤铵态氮含量是控制N2O排放最重要的因素。温带沙质荒漠是大气CH4一个微弱的汇，每年从大气中吸收0.83 kg CH4-C ha-1。这主要受含有pmoA功能基因的微生物 (甲烷氧化菌群)的调控。增加30%降水和低氮沉降量 (30 kg N ha-1 yr-1)分别显著的增加土壤CH4的汇高达62.3 和52.6 %，但是高氮沉降量(60 kg N ha-1 yr-1) 并无显著的影响；相反，增温每年减少CH4吸收1.61%。然而，在极端干旱或者极端降水事件后，增温对土壤CH4吸收的影响是变化的，这主要取决于土壤湿度的变化。CH4吸收对降水、增温和氮沉降的交互效应的响应显著的低于任何单因素效应。CH4吸收与土壤可溶性有机碳 (DOC)，土壤湿度和短命植物地上生物量显著正相关，但是与土壤温度显著负相关。冗余分析的结果表明，土壤CH4吸收主要受土壤底物浓度的控制，主要是土壤可溶性有机碳的影响，而受环境因素和生物因素影响较低。这可能表明气候变化和大气氮沉降对荒漠土壤CH4吸收的影响可能是间接的。增加降水和氮沉降显著的促进土壤呼吸，但是增温减少土壤呼吸，这主要取决于表层土壤湿度的变化，且土壤呼吸对增加降水和氮沉降的交互效应显著的低于任何单因素；并且发现降水和高量氮沉降的交互效应减少土壤呼吸4.25%。非线性回归分析表明土壤呼吸与土壤温度、土壤湿度和土壤铵态氮呈现单峰变化趋势。但是从结构方程模型的结果发现土壤温度是控制土壤呼吸最重要的因素。此外，土壤呼吸年际变化主要取决于短命植物生产力的变化，而日变化主要受土壤温度的控制。温带沙质荒漠生态系统是大气主要温室气体(CO2，CH4 和N2O)一个重要的汇，每年从大气吸收的当量二氧化碳 (eCO2)为623 kg ha-1。增加降水和大气氮沉降显著增强荒漠生态系统温室气体的汇，但是持续增强的气候变暖将削弱温室气体的汇。然而，降水、气候变暖和氮沉降的交互效应是低于单因素的效应，除了降水和低氮沉降量的交互。这表明高量的，长期高量氮沉降和气候变暖可能减少荒漠生态系统温室气体的汇，应该加强防范措施。综上表明，荒漠土壤温室气体排放对降水、温度和氮沉降的升高十分敏感，且在未来温带荒漠降水增加，气候变暖和一定量氮沉降升高的背景下将增加该系统温室气体的汇，这将对气候变化产生正反馈，对于减缓气候变暖具有重要意义。 |
| 英文摘要 | Global warming was considered as an indisputable fact and soil greenhouse gas emission imbalance was the most critical cause. As for the vast expanse of desert ecosystems area, weak changes in greenhouse gas emissions of the soil could have a profound impact on climate change. The temperate desert is one of the most vulnerable terrestrial ecosystems in the world, is sensitive to the response of precipitation patterns, climate change and atmospheric N deposition, which will profoundly impact on the flux of greenhouse gases in desert ecosystem. However, there was still lack of sufficient attention and systematic research on the soil greenhouse gas emission as the low carbon reserves in desert soils.An multi-factor field experiment were conducted in situ to investigate the Response characteristics and driving mechanism of warming, increasing precipitation and N deposition to greenhouse gases(CO2, CH4 and N2O) emissions in the Gurbantunggut Desert northwest China from July 2014 to October 2017. Greenhouse gas fluxes were measured using gas chromatography and static chambers (50 × 50 cm × 10 cm). The field experiment provided an important theoretical basis on accurate assessment of IPCC greenhouse gas sources and sinks in arid areas. The study reached the following conclusion:The rapid and transient response of the three main greenhouse gas (CO2, CH4, and N2O) emissions were found to precipitation events in desert soil, which mainly depends on the rapid change in moisture of soil layer 0-5 cm, for instance, the 5 mm precipitation event could exert evident emission only last for 2-3 days. It was found that temperately sandy desert e was weak source for N2O, which was 0.13 kg N2O-N ha-1 yr-1, mainly from the nitrification microorganism with amoA functional genes. The non-growing season emission accounts for 42.5% of the annual N2O emission. N2O emission significantly increased by 55-132.5% with N addition rate of 30 and 60 kg N ha-1 yr-1, but no changes in annual N2O emission flux were found by increasing 30% precipitation and warming, although some few N2O emission raises appeared after precipitation occasionally, which is largely due to the limited soil N content. It was found that soil N2O emission was significant related to soil temperature, soil moisture and soil ammonium content. Moreover, structural equation model showed that soil ammonium content is the most important factor in controlling N2O emission.Soil methane uptake was mainly attributed to the microorganisms that contains pmoA functional genes (methane-oxidizing bacteria group). The sandy desert is a weak sink of atmospheric methane, absorbing 0.83 kg CH4 C ha-1 yr-1. The increase of 30% precipitation and low N deposition rate (30 kg N ha-1 yr-1) significantly increased the soil methane to 62.3 and 52.6%, respectively. However, no significant impact on methane uptake was observed by the high N deposition rate (60 kg N ha-1 yr-1). Instead, warming decreased the methane uptake by 1.61%. After the extreme drought or extreme precipitation events, warming effect on the soil methane absorption was variable, which depended on the change of soil moisture. The interaction effects of precipitation, warming and N deposition on methane absorption were significantly lower than that of any single factor. The methane absorption are significantly related to soil dissolved organic carbon (DOC) and the soil moisture and the ephemerals aboveground biomass, but negatively correlated with the soil temperature. Redundancy analysis results showed that methane absorption mainly controlled by soil substrate concentration, especially the influence of soil DOC, rather than the environmental factors and biological factors. These results indicated that the influence are indirect of climate change and N deposition on the methane uptake in desert soil.Increasing precipitation and N deposition significantly promoted the soil respiration, but that reduced in warming treatment, which mainly because of the change of topsoil moisture. The interaction effect of precipitation and N deposition was significantly lower than any single factor; Moreover, the interaction effect of precipitation and high N deposition reduced soil respiration by 4.25%. Nonlinear regression analysis showed unimodal trends that were between soil respiration and soil temperature, soil moisture or soil ammonium N. However, structural equation model showed that soil temperature was the most remarkable controlling factor of soil respiration. In addition, it was found that the interannual variation of soil respiration mainly depended on the change of short-term plant biomass, while daily variation in soil respiration was mainly controlled by soil temperature.A temperate sand desert ecosystem was an important sink of atmospheric greenhouse gases (CO2, CH4 and N2O), absorbing 623 kg eCO2 ha-1 each year. Increased precipitation and lower N deposition significantly enhanced the greenhouse gas sink in desert ecosystems, but continued warming and high N deposition would weaken greenhouse gas sinks. However, the interaction effect of precipitation, climate change and N deposition is lower than that of single factor, except for the interaction effect of precipitation and low N deposition. The result indicated that long-term high N deposition and climate change might had little or negative influence on the GHGs sink of desert ecosystem. In summary, the desert soil GHG emissions were sensitive to precipitation, climate warming and the elevated N deposition. Furthermore, under the future background of increasing precipitation, climate warming and elevated N deposition, the temperate desert would increase the GHG sink, and would give a positive feedback to climate change, which was critically significant to alleviate global climate warming. |
| 中文关键词 | 降水格局改变 ; 氮沉降 ; 气候变暖 ; 沙质荒漠 ; 温室气体 |
| 英文关键词 | Precipitation pattern changes nitrogen deposition warming Temperate sandy desert Greenhouse gas emission |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院新疆生态与地理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288153 |
| 推荐引用方式 GB/T 7714 | 岳平. 温带沙质荒漠温室气体通量对水分、温度和氮沉降升高的响应[D]. 中国科学院大学,2018. |
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