EGI OpenIR
降水变化、增温和氮沉降对天山高寒草原温室气体排放的影响
Alternative TitleEffects of Precipitation Change, Climate Warming and N Deposition on Greenhouse Gases Emissions in an Alpine Grassland of Tianshan Mountains
耿凤展
Subtype博士
Thesis Advisor刘学军 ; 李凯辉
2020-08-30
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Discipline理学博士
Keyword温室气体 天山高寒草原 降水变化 氮沉降 变暖 Greenhouse Gas Tianshan Alpine Grassland Precipitation Change Nitrogen Deposition Warming
Abstract伴随着全球气候变化和人为活动的加剧,大气温室气体浓度处于不断升高的状态。占地球陆地面积 40%的草原和 41%的干旱生态系统,在全球陆地生态系统碳氮循环中扮演重要的角色。长期处于低温环境的高寒生态系统和缺乏降水的干旱生态系统, 对增加温度和降水等气候变化因子具有较高的敏感性, 可能对土壤温室气体排放等碳氮循环过程会产生深远的影响。 但以往研究较少关注天山高寒草原这一脆弱生态系统对降水、温度和氮沉降变化的响应及其机理。本研究依托中国科学院巴音布鲁克草原生态系统研究站,自 2016 年 5 月至2018 年 9 月,利用静态箱-气相色谱法,在长期围封的紫花针茅(Stipa purpurata)群落,开展了模拟氮沉降、降雨变化和远红外模拟增温等多因子控制试验, 分析了气候变化和长期氮沉降对新疆天山高寒草原的 CO2、 CH4 和 N2O 等主要温室气体通量的影响。 本研究的主要结果如下:(1) 天山高寒草原是大气 N2O 的源,在小于 90 kg N ha-1 yr-1 的中高量氮沉降范围内, 长期氮沉降加剧能够促进土壤 N2O 排放。低于 10 kg N ha-1 yr-1 氮沉降的作用不显著,超过 30 kg N ha-1 yr-1 的氮沉降,表现出显著的促进效应。 该区域氮沉降对 N2O 排放的释放因子仅为 0.19%,远低于 IPCC 缺省值 1%,使得IPCC 高估了氮沉降对 N2O 释放的影响。 2013 至 2017 年,氮沉降显著增加了土壤累积 N2O 释放量,且随时间的延长有增加的趋势。此外,氮沉降时间越长,N2O 释放变异性越弱。长期氮沉降模拟试验显示, 超过 30 kg N ha-1 yr-1 氮沉降量对 N2O 排放有显著的影响,但释放因子较低, IPCC 缺省值在非氮饱和的高寒草原生态系统,应该被重新估算。(2) 天山高寒草原年积累 N2O 排放量约 0.18 kg N ha-1,降水增加与氮沉降交互作用, 以及降水减少与氮沉降交互作用,年积累 N2O 排放量分别达到0.33 kg N ha-1 和 0.30 kg N ha-1。降水增加或减少对 N2O 排放没有显著影响。 在氮沉降加剧背景下,降水增加显著促进了 N2O 排放,降水减少的促进作用不显著。不同的降雨条件下,氮沉降显著或不显著地促进了 N2O 释放。巴音布鲁克高寒草原表现出了较强的 CH4 库,年积累 CH4 吸收量是 5.66 kg C ha-1。降雨增加和氮沉降交互作用显著抑制 CH4 吸收,年吸收量可减少至 4.81 kg C ha-1 yr1,而减水增氮则显著促进了 CH4 吸收,年累积吸收量为 7.24 kg C ha-1 yr-1。正常降雨和减少降雨背景下,氮沉降显著促进了 CH4 吸收,而在增加降雨背景下则表现为微弱的抑制吸收的作用。 两种氮沉降背景下, 降水增加均抑制了 CH4吸收,减少降水反之。 天山高寒草原是较强的 CO2 源,年生态系统呼吸释放量为 7136 kg C ha-1。氮沉降和降水增加交互作用显著抑制了 CO2 排放,而减水加氮交互作用反之。通过分析净全球变暖潜势(GWP)发现,氮沉降均促进了温室效应,增加降水显著促进了 19.24%的 GWP, 而减少降水则显著抑制了47.44%的 GWP。氮沉降和增加降水交互作用,显著促进了 62.26%的 GWP。 而和减少降水交互抑制作用不显著。(3)气候变暖和雨水增加共同作用抑制了 N2O 排放,年累积排放量为0.13 kg N ha-1。 无论增温与否,增加降水都不会显著影响 N2O 排放。而气候变暖的影响, 在增加降水的背景下表现出显著的抑制作用。正常降雨背景下,气候变暖并没有显著影响 N2O 排放。气温和降水共同增加,显著降低 CH4 年吸收量至 5.18 kg C ha-1。 不同温度背景下,增加降水均显著抑制了 CH4 吸收, 而气候变暖影响不显著。 但是不变暖背景,增加降水对 CH4 吸收的抑制效应为11.03%,高于变暖背景下 7.65%的抑制效应,说明了变暖降低了降水对 CH4 吸收的抑制效应。未来的暖湿环境显著增加了 23.18%的年累积生态系统呼吸量。雨水增加能够显著促进 CO2 排放,以在气温变暖背景下的促进效应最高,为26.92%。在两种不同降雨量背景下, 气温升高都不会显著影响 CO2 排放。通过分析净 GWP 发现, 无论未来气候变暖与否, 降雨增加对温室效应表现出正的效应。不同的降水条件下,气候变暖均不会显著影响净温室效应。而降雨增加和气候变暖共同作用显著促进了净 GWP。(4)非生长季 CO2 排放占全年的 10.38% - 22.13%。相比冻融季(FTP),非生长季期间的非冷冻季(NFS)有较长的持续天数,同时 NFS 相比冷冻季(FS)有较高的排放速率,使 NFS 占年累积排放通量的 5.35% - 16.24%,均高于非生长季其他两个时期的比例(FS: 2.89% - 6.11%; FTP: 0.75% - 2.07%)。非生长季占全年 CH4 累积吸收量的 11.06% - 55.24%,具有较大的年际间变异性,可能与冬季积雪变异以及全年累计吸收量有关。 NFS 占比高达 13.18% -37.58%,远高于 FS 和 FTP 占比。 N2O 非生长季排放占全年排放量的 0.15% -56.30%,且具有较大的年际间变异,可能与 N2O 排放量较低、 非生长季的低温和自身不稳定性有关。非生长季 N2O 排放占比以 FS 最高(-5.19% - 35.27%),其次是 NFS(-2.11% - 14.39%),变异性较大。(5)生态系统呼吸与土壤温度、土壤湿度、硝态氮和可溶性有机碳有显著的相关性,结构方程模型分析发现土壤湿度是影响生态系统呼吸的主要因素,解释率达 73%。甲烷吸收与土壤温度、土壤湿度、硝态氮具有显著的相关性,土壤湿度和硝态氮的解释度为 55%和 33%。另外, 降雨增加和氮沉降对与碳循环相关的纤维素酶活性的影响与其对生态系统呼吸的影响具有显著的正相关关系, 而气候变暖的影响不显著。氮沉降对木质素酶活性的影响与其对生态系统呼吸的影响具有显著的正相关关系, 对纤维素酶和木质素酶活性的影响与其对 CH4 吸收的影响均具有显著正相关关系。综上, 本研究初步明晰了全球变化三个重要驱动因子,通过影响天山高寒草原土壤水分、 温度、 土壤养分以及酶活性, 进而产生不同的温室效应。氮沉降和雨水减少显著降低了 GWP,而氮沉降和雨水增加相反。另外,气候变暖和雨水增加共同作用对高寒干旱草原 GWP 有显著增加,对温室效应产生更大的促进作用。 在全球变化背景下,开展长期、多水平的驱动因子对天山高寒草原温室气体排放影响的试验, 可为深入解析天山高寒草原温室气体排放的响应规律和机理提供科学依据。
Other AbstractAtmospheric greenhouse gas (GHG) concentrations are keeping rising, with thedramatic global climate change and anthropogenic activities. It plays an important rolein the carbon-nitrogen cycle of global terrestrial ecosystem in grassland and aridecosystems, which covers 40% and 41% of land area on the earth, respectively. Alpineand arid ecosystem are more sensitive to increased temperature and precipitation, andhave a profound influence on carbon and nitrogen cycling process such as GHGemissions, where low temperature and lack of precipitation last for a long time duringa whole year. Compared with temperate steppe, studies on responses and mechanismsto varying precipitation, temperature and nitrogen deposition in alpine grassland inTianshan Mountains are very limited.A multi-factors controlling experiment was developed in an ungrazed Stipapurpurata grassland using static chamber and gas chromatography at the BayinbulukGrassland Ecosystem Research Station of Chinese Academy of Sciences, whichcombined with increased N deposition, precipitation change and far-infrared climatewarming, from May 2016 to September 2018. It aimed to investigate the response ofecosystem respiration, CH4 uptake and N2O emission to climate change and long-termN deposition in an alpine grassland of Tianshan Mountain in Xinjiang. The main resultsare summarized as follows:(1) Alpine semiarid grassland of Tianshan Mountain is an atmospheric source forN2O. Long-term increased N deposition promoted soil N2O emission within 90 kg Nha-1 yr-1. N deposition did not significantly affect N2O emission below 10 kg N ha-1 yr-1, but promote it remarkably above 30 kg N ha-1 yr-1. The N2O emission factor was only0.19%, lower than the IPCC default value of 1%, which made the IPCC overestimatethe impact of nitrogen deposition on N2O release in the similar study area. Nitrogendeposition significantly increased the cumulative N2O flux from the soil. The longertime N added, the stronger and lower variability of cumulative N2O emission are. Thestudy clarified N deposition up to 30 kg N ha-1 yr-1 has a significant effect on N2Oemission with a lower emission factor. It should be re-estimated of IPCC default valuesin non-N saturate alpine grassland and other remote areas.(2) The results of three-year simulated precipitation change and increasingnitrogen deposition experiments showed that, the annual accumulated N2O emissionwas about 0.18 kg N ha-1 and rose up to 0.33 kg N ha-1 and 0.30 kg N ha-1 in the combined effects of increased precipitation and N deposition and the combined effectsof decreased precipitation and N deposition, respectively. Only increased or decreasedprecipitation did not affect N2O emission significantly. But under N deposition,increased precipitation promoted N2O emission significantly and decreasedprecipitation reversed it. N deposition facilitated N2O emission notably or not in thedifferent precipitation conditions. The alpine grassland was a stronger CH4 sink and theannual accumulated CH4 uptake was 5.66 kg C ha-1. The combined effects of increasedprecipitation and N deposition suppressed CH4 uptake and the combined effects ofdecreased precipitation and N deposition promoted it significantly. The annualaccumulated CH4 uptake were 4.81 kg C ha-1 yr-1 and 7.24 kg C ha-1 yr-1 respectively.N deposition stimulated CH4 uptake remarkedly under ambient and decreasedprecipitation. But under increased precipitation condition, N deposition suppressed CH4uptake weakly. Whether under N deposition or ambient deposition, increasedprecipitation suppressed CH4 uptake and decreased precipitation promoted it. TheTianshan alpine grassland acted as a stronger CO2 source with 7136 kg C ha-1 of annualaccumulated ecosystem respiration. The combined effects of N deposition anddecreased precipitation suppressed CO2 emission and the combined effects of Ndeposition and increased precipitation accelerated it. Through analyzing net GlobalWarming Potential (GWP), we found that, N deposition and increased precipitation allaccelerated net GWP, and decreased precipitation suppressed it. The combined effectsof N deposition and increased precipitation promoted GWP significantly, and thecombined effects with decreased precipitation decreased it insignificantly.(3) In the 3-year simulated climate warming and increasing precipitationexperiment, the results showed that the combined effects of climate warming andincreased precipitation suppressed N2O emission, and the annual accumulated N2Oemission decreased to 0.13 kg N ha-1. Increased precipitation did not affect N2Oemission significantly whether under ambient temperature or warming condition.Meanwhile warming notably depressed N2O emission only under increasedprecipitation. Warming did not affect N2O emission under ambient precipitation. Thecombined effect obviously reduced CH4 uptake to 5.18 kg C ha-1. Increasedprecipitation inhibited CH4 uptake markedly whether under ambient temperature orincreased temperature condition. Climate warming did not have an influence on CH4uptake. Warmer and wetter environment enhanced annual accumulated ecosystemrespiration by 23.18%. Increased precipitation also enhanced CO2 emission greatly.Increased precipitation under climate warming promoted more CO2 emission thanunder ambient temperature. Climate warming did not affect CO2 emission under thetwo precipitation treatments. Through analyzing GWP, we found that, whether climatewarmed or not, increased precipitation accelerated greenhouse effects and showedpositive effects on climate warming. In contrast, climate warming did not affectgreenhouse effects in different precipitation conditions. The interaction vastlystimulated GWP.(4) The accumulated CO2 emission in non-growing season (NGS) occupied 10.38%to 22.13% of annual accumulate CO2 emission in the Bayinbuluk alpine grassland. Thenon-freezing season (NFS) during NGS lasted longer time than freeze-thawing period(FTP). And higher CO2 flux emitted in NFS than freezing season (FS). The accumulatedCO2 emission in NFS accounted for 5.35% to 16.24% of annual accumulate CO2emission, which was higher than FS and FTP (FS: 2.89% to 6.11%; FTP: 0.75% to2.07%). The accumulated CH4 uptake in NGS accounted for 11.06% to 55.24% ofannual emission and has higher annual variability because of the higher annualvariability of snow in winter and annual CH4 uptake. NFS has the highest occupation(13.18% to 37.58%) than FS and FTP during NGS. The accumulated N2O emission inNFS occupied from 0.15% to 56.30% of annual accumulative emission with highervariability, which could be because of the lower and unstable N2O emission in NFS. InNGS, the ratio of N2O emission in FS (-5.19% to 35.27%) was highest, and thesecondary was NFS (-2.11% to 14.39%).(5) The ecosystem respiration in the experimental region has significantcorrelations with soil temperature, soil moisture, nitrate nitrogen and soluble organiccarbon, in which soil moisture was the most direct and important factor affectingecosystem respiration with 73% interpretation rate. There was a significant correlationbetween methane uptake and soil temperature, soil moisture, and nitrate nitrogen. Theinterpretation of soil moisture and nitrate nitrogen were 55% and 33%. In addition, theeffects of climate change factors such as increased rainfall, and nitrogen deposition, oncellulase activity related to the carbon cycle have a significant positive correlation withtheir effects on ecosystem respiration, but climate warming had no relevance to it. Theeffect of nitrogen deposition on ligninase activity has a significant positive correlationwith its effect on ecosystem respiration, and the effect of it on ligninase and cellulaseactivity had significant correlations with its effects on CH4 uptake.In general, the study analyzed the effects of three main global change drivers ongreenhouse effects in Tianshan alpine grassland through analyzing the soil moisture,soil temperature, microbial enzyme activity, and soil nutrient environment. Thecombination of N deposition and decreased precipitation reduced GWP, while thecombination of N deposition and increased precipitation promoted it. In addition, thecombined effects of climate warming and increased precipitation showed strongereffects on GWP and had much promoting GHG effects. The effects of long-term andmulti-level driving factors on GHG fluxes would be needed and provide scientificevidence to clarify the response mechanisms of GHGs in Tianshan alpine steppe inresponse to climate change.
Subject Area生态学
Language中文
Document Type学位论文
Identifierhttp://ir.xjlas.org/handle/365004/15417
Collection中国科学院新疆生态与地理研究所
研究系统
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
耿凤展. 降水变化、增温和氮沉降对天山高寒草原温室气体排放的影响[D]. 北京. 中国科学院大学,2020.
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