大兴安岭多年冻土泥炭沼泽地—气间温室气体交换的观测和模拟

发布时间：2018-04-05 20:09

本文选题：碳循环　切入点：温室气体交换　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

【摘要】：IPCC报告指出,北方高纬地区是气候变化敏感区,气候变化对该地区水热条件影响显著,近几十年来,全球温度的上升造成该地区多年冻土的持续退化。北方高纬泥炭沼泽碳储量占全球土壤碳库的1/3,在气候变化的作用下,北方高纬泥炭沼泽有可能从碳汇转化成为碳源,对气候变化起到反馈作用。目前关于气候变化对北方高纬泥炭沼泽碳循环影响的研究还很薄弱。因此,本研究选取大兴安岭多年冻土泥炭沼泽为研究对象,采用涡度协方差法,对生态系统二氧化碳(CO_2)和甲烷(CH_4)交换通量进行连续定点观测,通过对数据的整合分析,探究从日变化到季节变化尺度地-气间CO_2和CH_4交换的规律,分析不同时间尺度的环境控制因子,改进和完善现有统计模型,模拟不同时间尺度地-气间CO_2和CH_4交换,并根据增温实验的情境,预测增温对大兴安岭多年冻土泥炭沼泽地-气间CO_2和CH_4交换的影响。本研究主要有以下几方面的进展:1在涡度协方差法数据处理方面:以通量贡献区和湍流稳定性作为控制条件,采用更加严格的通量数据质量控制标准,建立通量数据筛选方案,能够显著提高了观测数据质量,减少观测数据总体不确定性。采取这种处理方法,能够揭示更高时间分辨率下地-气间CO_2和CH_4交换的规律,发现CH_4交换的日间变化规律呈现单峰分布趋势,CO_2交换在午前和午后呈现不同的光响应趋势。除此之外,地-气间CH_4通量呈现一定程度的空间差异性。2揭示了多年冻土泥炭沼泽地-气间CH_4交换通量的变化特征和环境控制因子:2014年和2015年生长季观测到CH_4交换通量的波动范围分别为1.8~40.2 mg CH_4 m-2 d-1和-3.9~15.0 mg CH_4 m-2 d-1。CH_4通量与深层(15 cm及以下)土壤温度、融深显著相关。据估计,2014年和2015年生长季后半段CH_4释放分别占整个生长季释放量的77.9%和85.9%。将标准化的融深作为模拟CH_4交换通量的控制系数加入指数型温度响应模型能够有效提高多年冻土泥炭沼泽CH_4通量模拟准确度。CH_4通量的季节变化受到多年冻土由表层到深层逐层进行的季节性融化特征以及季节性温度变化共同控制。强降水事件和生长季总降水量分别对CH_4通量的短期变化和CH_4释放的年际差异有显著性影响。3揭示了多年冻土泥炭沼泽地-气间CO_2交换通量的变化特征和环境控制因子:经典光响应方程适用于模拟研究区植被光合速率,在日变化尺度上高强度光照可能导致植物光合能力的降低,描述光合和呼吸速率的参数在季节变化的尺度上呈现显著的单峰分布趋势。与呼吸速率的温度响应方程相结合,利用改进的CO_2交换模型,模拟日CO_2净交换量波动范围在-4.42 g C m-2 d-1和2.90 g C m-2 d-1之间,2014年和2015年生长季(5月19日~10月8日)吸收量分别为78.35 g C m-2和90.07 g C m-2。表观光能利用率最大约为0.049 mol CO_2 mol photon-1,生态系统理论光合速率上限约为27.24μmol CO_2 m-2 s-1,而系统能够达到的CO_2净最大交换通量约-15μmol CO_2 m-2 s-1。每个生长季8月中下旬,系统由碳汇逐渐向碳源转化。4预测了在增温的情境下多年冻土泥炭沼泽CO_2交换通量的变化趋势:被动增温系统能够模拟变暖条件下环境因子的变化趋势,根据被动增温系统内环境数据记录,开顶箱内部气温和5 cm土温平均分别上升约0.81°C和2.42°C。根据这一情境,模拟气候变化条件下多年冻土泥炭的响应特征,系统的碳源特征逐渐减弱,至气温上升0.67oC,对应土壤温度上升约2.0oC时,估算全年尺度上多年冻土泥炭转化为净CO_2源,而当气温上升约1.0oC,土壤温度上升约3.0oC时,生态系统在生长季内向净CO_2源转化。
[Abstract]:IPCC report pointed out that the northern high latitude region is sensitive to climate change, the impact of climate change on the water and heat conditions in the region significantly, in recent decades, the global temperature rise caused by the continued degradation of the permafrost area. Northern high latitude peatlands carbon reserves accounted for 1 of the global soil carbon pool in /3, the effects of climate change. The northern high latitude peat swamp likely from carbon sequestration into carbon source, to a feedback effect on climate change. The research on climate change in the northern high latitude peatlands carbon cycle effect is very weak. Therefore, this study selected Greater Khingan Range permafrost peat as the research object, using the eddy covariance method, the ecological system of carbon dioxide (CO_2) and methane (CH_4) fluxes for continuous observation, through the integration of data analysis, the inquiry from the daily change to seasonal scale gas exchange between CO_2 and CH_4. Law, control factor analysis of different time scale environment, improve and perfect the existing statistical model, simulation of different time scales between CO_2 and CH_4, gas exchange, and according to the warming experiment situation, predicting warming on permafrost in Greater Khingan Range peat bog - gas between the CO_2 and CH_4 exchange effect. This research progress the following aspects: 1 in the aspect of data processing method: the eddy covariance flux contribution and turbulence stability as the control condition, the flux data quality control more stringent standards, establishing a flux data screening scheme, can significantly improve the quality of observation data, reduce the data overall uncertainty. This processing method can reveal the higher time resolution under the CO_2 and CH_4 gas exchange rules, find that the daily variation of CH_4 exchange of unimodal distribution trends, CO_2 exchange in morning and afternoon The different light response trend. In addition, gas CH_4 fluxes showed.2 spatial difference to a certain extent reveals the permafrost peat bog - gas between CH_4 flux variations and environmental control factors: 2014 and 2015 growing season observed CH_4 flux in the wave range were 1.8~40.2 mg CH_4 m-2 D-1 and -3.9~15.0 mg CH_4 m-2 d-1.CH_4 flux and deep (15 cm and below) soil temperature, thawing depth was significantly correlated. It is estimated that in 2014 and 2015 growth season CH_4 release accounted for the whole growth season, the release amount of 77.9% and 85.9%. will control the standardized coefficient of thawing depth as the simulated CH_4 exchange flux added index temperature response model can effectively improve the seasonal variation of permafrost peat CH_4 flux simulation accuracy of.CH_4 flux by permafrost from the surface to the deep layer by layer seasonal melting The common control characteristics and seasonal change of temperature and precipitation events. The growth of Ji Zong precipitation of short-term changes and CH_4 release of the annual variation of CH_4 flux has a significant impact.3 reveals the permafrost peat bog - gas change between the environment and the characteristics of CO_2 flux control factor: classical optical response equation is used to simulate the study on vegetation photosynthetic rate, diurnal changes in scale of high intensity light may cause the decrease of photosynthetic capacity of the plant, description parameters of photosynthetic and respiration rate showed a single peak distribution trend significant seasonal changes in scale. The equation combined with the respiration rate of the temperature response, exchange model using the improved CO_2 Simulation on the net CO_2 exchange volume fluctuation in the range between -4.42 g C m-2 D-1 and 2.90 g C m-2 D-1, in 2014 and 2015 growing season (May 19th ~10 8) uptake were 78.35 g and 90.07 g C m-2 C m-2. apparent light use rate is about 0.049 mol CO_2 mol photon-1, the ecological system theory of photosynthetic rate limit is about 27.24 mol CO_2 m-2 S-1 CO_2, and the system can reach the maximum net flux of about -15 mol CO_2 m-2 s-1. in each growing season 8 months late, the system consists of carbon sinks gradually to the carbon source conversion of.4 to predict the variation trend in the context of increasing temperature in permafrost peat swamp CO_2 exchange: passive warming system can simulate warming trend of environmental factors under the condition of increasing environmental temperature according to the passive data recording system, open top gas temperature and 5 cm temperature respectively increased by about 0.81 DEG C and 2.42 DEG C. according to this situation, the simulation response characteristics under the condition of climate change in permafrost peat, carbon source and characteristics of the system gradually weakened, and temperature rise of 0.67oC, the corresponding soil temperature rise of about 2.0oC, estimated the annual scale more The peat of permafrost is converted into a net CO_2 source, but when the temperature rises about 1.0oC and the soil temperature rises about 3.0oC, the ecosystem converts to the net CO_2 source in the growing season.

【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;X16

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