增温对大兴安岭多年冻土区泥炭地氮氧化物排放的影响研究

发布时间：2017-12-28 02:10

本文关键词：增温对大兴安岭多年冻土区泥炭地氮氧化物排放的影响研究　出处：《中国科学院大学(中国科学院东北地理与农业生态研究所)》2017年博士论文　论文类型：学位论文

【摘要】：北方高纬度地区是泥炭地的主要集中分布区,也是全球变暖的敏感区。近几十年来,北方高纬地区升温效果明显,导致该区多年冻土大面积退化。日益增强的人类活动更加剧了这种变化,泥炭地中碳、氮循环均受到了直接或者间接的影响,从而对气候变化产生正反馈或者负反馈作用。但国内关于气候变暖对多年冻土区泥炭地氮循环研究甚少,因此,本研究以大兴安岭连续多年冻土区泥炭地为研究对象,基于野外OTC原位控制增温实验,并与室内培养实验相结合,重点围绕增温、冻融作用、氮可利用性变化对泥炭地氮氧化物排放的影响,阐明增温背景下泥炭地氮氧化物排放的季节与年际排放动态,揭示了增温对泥炭地氮氧化物排放通量的影响及其主要影响因素,探讨了N_2O排放通量对冻融作用和氮可利用性变化的响应。主要取得以下结论:(1)基于野外OTC原位增温控制实验研究发现,增温对多年冻土区泥炭地表层土壤温度的增加幅度大于气温。其中,气温平均增加了0.6℃,5cm、10cm、20cm、30cm、50cm、100cm土壤温度分别平均增加了2.42℃、1.48℃、1.21℃、0.57℃、0.45℃、0.48℃。土壤温度的增加导致土壤融化深度平均增加了6.6cm,而增温对土壤含水量影响较小。(2)基于野外OTC原位增温控制实验研究发现,增温显著的促进了各观测年N_2O排放通量,提高了89%-223%。表现为:从年际增加幅度来看,柴桦-泥炭藓泥炭地在2013、2014和2015年N_2O排放通量的平均增加幅度分别为174%、128%和167%;狭叶杜香-泥炭藓泥炭地在2013、2014和2015年N_2O排放通量的平均增加幅度分别为165%、123%和122%。从月份增加幅度来看,柴桦-泥炭藓泥炭地的N_2O排放通量的增加幅度在8月份最大为223%,而狭叶杜香-泥炭藓泥炭地增加幅度在7月份最大为217%。研究表明,土壤温度和土壤融化深度是影响N_2O排放的主要因素。(3)基于野外OTC原位增温控制实验研究发现,增温显著的促进了各观测年NO排放通量,提高了75%-239%。表现为:从年际增加幅度来看,柴桦-泥炭藓泥炭地在2013、2014和2015年NO排放通量的平均增加幅度分别为176%、226%和133%;狭叶杜香-泥炭藓泥炭地在2013、2014和2015年的NO排放通量的平均增幅分别为154%、177%和127%。从月份增加幅度来看,柴桦-泥炭藓泥炭地在8月份达到最大增幅为239%,而狭叶杜香-泥炭藓泥炭地在7月份达到最大增幅为219%。研究表明,土壤温度是影响NO排放的主要因素。(4)基于室内冻融模拟实验研究发现,冻融作用和氮添加显著的促进了多年冻土区泥炭地N_2O的释放。冻融过程中观测到N_2O的排放峰值,并且冻融作用在硝态氮添加作用下尤为明显。N_2O排放量与NO3-浓度呈正相关关系,这说明冻融作用下多年冻土区N_2O的产生受到NO3-有效性和反硝化作用的影响。冻融作用与硝态氮添加的交互作用加速了多年冻土区泥炭地N_2O的大量排放。(5)通过模拟氮可利用性变化培养实验研究发现,土壤N_2O排放速率随着氮输入的增加而增强,氮输入对N_2O排放产生激发效应,但是底层土壤的激发效应与表层土壤相比出现延迟现象。氮输入对0-15cm土壤的N_2O通量影响最为显著,各个氮处理与对照处理的差异达到显著水平。氮输入对15-30cm土壤的N_2O通量影响不显著,30-45cm土壤的N_2O通量只有在高氮处理下影响显著。
[Abstract]:The northern high latitudes are the main concentrated distribution areas of peat land and a sensitive area of global warming. In recent years, the northern high latitude warming effect is obvious, the permafrost degradation in large area. The increasing human activity has made such a change. The carbon and nitrogen cycles in peatlands have been directly or indirectly affected, thus giving rise to positive feedback or negative feedback on climate change. But the domestic about climate warming on peatlands in permafrost regions of the nitrogen cycle research very little, therefore, the study on peat continuous permafrost zone in Greater Khingan Range as the research object, the control field warming experiment based on OTC in situ, and combined with indoor culture experiments, focus on increasing temperature, freezing and thawing, nitrogen effects on peatland the emission of nitrogen oxides by change, clarify the warming under the background of nitrogen oxide emissions from peatlands, seasonal and interannual dynamic emission, reveals the effects of warming on peatland nitrogen oxide emission flux and its main influencing factors, discusses the N_2O emission flux of freeze thawing and response to nitrogen availability changes. The main conclusions are as follows: (1) based on field experiments of OTC in situ warming control, it is found that the increase of soil temperature on the surface layer of peat in permafrost regions is greater than that of air temperature. The average temperature increased by 0.6 degrees. The soil temperature of 5cm, 10cm, 20cm, 30cm, 50cm and 100cm increased by 2.42, 1.48, 1.21, 0.57, 0.45, 0.48, respectively. The increase of soil temperature resulted in an average increase of 6.6cm in the depth of soil melting, while the effect of increasing temperature on soil water content was less. (2) based on the experimental study of OTC in situ temperature control in the field, it is found that the increase of temperature significantly improves the N_2O emission flux in each observation year and increases the 89%-223%. Performance: from the annual rate of increase, the birch - sphagnum peat in 2013, 2014 and 2015 N_2O emission flux average increase rate were 174%, 128% and 167%; Ledum palustre - sphagnum peat in 2013, 2014 and 2015 N_2O emission flux average increase was 165%, respectively. 123% and 122%. The increase of N_2O emissions from Chai Hua sphagnum peat in August is the largest in August, and the maximum increase is 223% in July. The results show that soil temperature and depth of soil melting are the main factors affecting N_2O emission. (3) based on the experimental study of OTC in situ temperature control in the field, it is found that the increase of temperature significantly improves the NO emission flux in each observation year and increases the 75%-239%. Performance: from the annual rate of increase, the birch - sphagnum peat in 2013, 2014 and 2015 NO emission flux average increase rate were 176%, 226% and 133%; Ledum palustre - sphagnum peat to an average increase of NO emission flux in 2013, 2014 and 2015 respectively 154%, 177% and 127%. From the monthly increase, the Chai Hua sphagnum peat land increased by 239% in August, while the narrow leaf duer sphagnum peat land reached a maximum increase of 219% in July. The study shows that soil temperature is the main factor affecting NO emission. (4) based on the indoor freezing and thawing simulation experiments, it is found that the freezing thawing and nitrogen addition significantly promote the release of N_2O in the peat land in permafrost regions. The peak of N_2O emission was observed during the freezing and thawing process, and the freezing and thawing effect was especially obvious with the addition of nitrate nitrogen. N_2O emission has a positive correlation with the concentration of NO3-, which indicates that the production of N_2O in permafrost region under freezing thawing is affected by the effectiveness of NO3- and denitrification. The interaction of freezing and thawing with the addition of nitrate accelerates the massive emission of N_2O in peat land in permafrost regions. (5) by simulating the change of nitrogen availability, we found that soil N_2O emission rate increased with the increase of nitrogen input, and nitrogen input had a stimulating effect on N_2O emissions. However, the excitation effect of the underlying soil was delayed compared with the surface soil. Nitrogen input had the most significant influence on the N_2O flux of 0-15cm soil, and the difference of nitrogen treatment and control treatment reached a significant level. Nitrogen input had no significant influence on the N_2O flux of 15-30cm soil, and the N_2O flux in 30-45cm soil was significantly affected by high nitrogen treatment.
【学位授予单位】：中国科学院大学(中国科学院东北地理与农业生态研究所)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：X171

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