KMS XINJIANG INSTITUTE OF ECOLOGY AND GEOGRAPHY，CAS
| 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 | |
| 岳平 | |
| Subtype | 博士 |
| Thesis Advisor | 刘学军 ; 李凯辉 |
| 2018-06-05 | |
| Degree Grantor | 中国科学院大学 |
| Place of Conferral | 新疆乌鲁木齐 |
| Degree Discipline | 理学博士 |
| Keyword | 降水格局改变 氮沉降 气候变暖 沙质荒漠 温室气体 Precipitation pattern changes nitrogen deposition warming Temperate sandy desert Greenhouse gas emission |
| Abstract | 全球气候变暖是科学界讨论的热点问题，而土壤温室气体排放失衡是造成全球气候变暖最重要的原因；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(CO2， CH4 和 N2O)通量对增加降水、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和荒漠生态系统稳定性提供重要的数据支撑和理论依据。本研究的主要结果如下：(1) 温带荒漠土壤呼吸， CH4 和 N2O 通量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 CO2， CH4 和 N2O 三种温室气体通量的影响也仅能持续 2-3 天，这主要归因于土壤表层 0-5 cm 处水分的迅速变化。(2) 温带荒漠土壤是大气 N2O 一个微弱的源，每年平均向大气中排放 0.13kg N2O-N ha-1，生长季和非生长季土壤 N2O 排放量分别占全年排放量的 57.5 和42.5%。氮沉降增加 30 或 60 kg N ha-1 yr-1 显著促进 N2O 排放 55-132.5%；但是增加降水和增温并没有显著改变 N2O年通量，尽管增加降水偶尔出现 N2O排放峰，这可能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 排放最重要的影响因素。(3) 温带荒漠土壤是大气 CH4一个微弱的汇，每年从大气中吸收 0.83 kg CH4-C ha-1。这主要被含有 pmoA 功能基因的微生物 (甲烷氧化菌群)的所氧化。增加30 %降水和适量氮沉降 (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。(4) 温带荒漠生态系统是大气 CO2 不可忽视的汇，每年从大气中固持176±43.51 kg CO2-C ha-1，增加降水和氮沉降显著的增强荒漠生态系统碳汇的功能，这主要是增加了短命植物和梭梭的碳汇能力。 增加降水和氮沉降显著促进土壤呼吸，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以及增温其交互效应的影响显著的低于任何单因素的影响， 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含量呈现单峰变化趋势。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。总之，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。(5) 初步发现温带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±163 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，但是长期的气候变暖将削弱温室气体的汇功能， 且降水、温度和氮沉降升高的交互效应的影响低于单因素的独立效应。综上表明， 温带沙质荒漠土壤呼吸， CH4 和 N2O 通量对降水、温度和氮沉降升高的响应十分敏感，并且该荒漠生态系统是大气主要温室气体重要的汇，增加降水和氮沉降显著的增强该温室气体汇的功能，这将对气候变化产生正反馈效应，对减缓气候变暖具有重要的意义。然而，值得警惕的是长期的气候变暖和全球变化多因素交互效应对于该区域温室气体汇的影响并不显著。 |
| Other Abstract | Global warming was considered as a disputable problem and soil greenhouse gasemission imbalance was the most critical cause. As for the vast expanse of desertecosystems area, weak changes in greenhouse gas emissions of the soil could have aprofound impact on climate change. The temperate desert is one of the most vulnerableterrestrial ecosystems in the world, is sensitive to the response of precipitation patterns,climate change and atmospheric N deposition, which will profoundly impact on the fluxof greenhouse gases in desert ecosystem. However, there was still lack of sufficientattention and systematic research on the soil greenhouse gas emission as the low carbonreserves in desert soils.An multi-factor field experiment were conducted in situ to investigate the responsecharacteristics and driving mechanism of warming, increasing precipitation and Ndeposition to greenhouse gases (CO2, CH4 and N2O) emissions in the GurbantunggutDesert northwest China from July 2014 to October 2017. Greenhouse gas fluxes weremeasured using gas chromatography and static chambers (50 × 50 cm × 10 cm). Thefield experiment provided an important theoretical basis on accurate assessment ofIPCC greenhouse gas sources and sinks in arid areas. The study reached the followingconclusion:(1) The rapid and transient response of the three main greenhouse gas (CO2, CH4, andN2O) emissions were found to precipitation events in desert soil, which mainly dependson the rapid change in moisture of soil layer 0-5 cm, for instance, the 5 mm precipitationevent could exert evident emission only last for 2-3 days.(2) It was found that temperately sandy desert was weak source for N2O, which was0.13 kg N2O-N ha-1 yr-1. The non-growing season emission accounts for 42.5% of theannual N2O emission. N2O emission significantly increased by 55-132.5% with Naddition 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 N2Oemission raises appeared after precipitation occasionally, which is largely controlleddue to the limited soil N content. It was found that soil N2O emission was significantrelated to soil temperature, soil moisture and soil ammonium content. Moreover,structural equation model showed that soil ammonium content is the most importantfactor in controlling N2O emission.(3) Soil methane uptake was mainly attributed to the microorganisms that containspmoA functional genes (methane-oxidizing bacteria group). The sandy desert is a weaksink 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 thesoil methane to 62.3 and 52.6%, respectively. However, no significant impact onmethane uptake was observed by the high N deposition rate (60 kg N ha-1 yr-1). Instead,warming decreased the methane by 1.61%. After the extreme drought or precipitationevents, warming effect on the soil methane uptake was variable, which depended on thechange of soil moisture. The interaction effects of precipitation, warming and Ndeposition 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 negativelycorrelated with the soil temperature. Redundancy analysis results showed that methaneabsorption mainly controlled by soil substrate concentration, especially the influenceof soil DOC, rather than the environmental factors and biological factors. These resultsindicated that the influence are indirect of climate change and N deposition on themethane uptake in desert soil.(4) Temperate desert was an important carbon sink, the carbon uptake rate was176±43.51 kg CO2-C ha-1, which was significantly increased by elevating precipitationand N deposition. Increasing precipitation and N deposition significantly promoted thesoil respiration, but that reduced in warming treatment, which was mainly because of the change of topsoil moisture. The interactive effect of precipitation and N depositionwas significantly lower than any single factor; Moreover, the interactive effect ofprecipitation and high N deposition reduced soil respiration by 4.25%. Nonlinearregression analysis showed unimodal trends that were between soil respiration and soiltemperature, soil moisture or soil ammonium N. However, structural equation modelshowed that soil temperature was the most remarkable controlling factor of soilrespiration. In addition, it was found that the interannual variation of soil respirationmainly depended on the change of short-term plant biomass, while daily variation insoil respiration was mainly controlled by soil temperature.(5) A temperate sand desert ecosystem was an important sink of atmosphericgreenhouse gases (CO2, CH4 and N2O), absorbing 623±163 kg eCO2 ha-1 each year.Increased precipitation and N deposition significantly enhanced the greenhouse gassink in desert ecosystems, but continued warming would weaken greenhouse gas sinks.However, the interaction effect of precipitation, climate change and N deposition islower than that of single factor, except for the interaction effect of precipitation and lowN deposition. The result indicated that long-term high N deposition and climate changemight had little or negative influence on the GHGs sink of desert ecosystem.In summary, the desert soil GHG emissions were sensitive to precipitation, climatewarming and the elevated N deposition, and the desert soil was important for GHGssink. Furthermore, under the future background of increasing precipitation, climatewarming and elevated N deposition, the temperate desert would increase the GHGs sink,and would give a positive feedback to climate change, which was critically significantto alleviate global climate warming. However, it was alarming that no significantimpact on GHGs sink was found by warming and the interactive effect of climatechange and N deposition. |
| Subject Area | 生态学 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.xjlas.org/handle/365004/14944 |
| Collection | 研究系统_荒漠环境研究室 |
| Affiliation | 中国科学院新疆生态与地理研究所 |
| First Author Affilication | 中国科学院新疆生态与地理研究所 |
| Recommended Citation 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]. 新疆乌鲁木齐. 中国科学院大学,2018. |
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