Knowledge Resource Center for Ecological Environment in Arid Area
| 荒漠河岸胡杨林生态系统水碳耦合特征及其影响因素研究 | |
| 其他题名 | Characteristics of water-carbon coupling and its environmental controls in a desert riparian forest |
| 马小红 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 冯起 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 在气候变暖、人口增加和淡水资源短缺的背景下，位于黑河下游极端干旱区的荒漠河岸胡杨林对于保障绿洲经济建设、维护绿洲生态安全起着极其重要的作用。与周围广袤的荒漠相比，荒漠河岸胡杨林的面积虽然不大，但是相对丰富的生物多样性、相对高的生产力和相对活跃的动态变化使其在整个流域的水碳循环过程中占据重要的位置。荒漠河岸胡杨林对气候变化和人类活动的响应十分敏感。目前，对荒漠河岸胡杨林水碳关系的研究多集中于小尺度（叶片或植株）的研究，而通过直接、连续和长期的观测数据所进行的生态系统尺度的水碳关系研究很少。涡度相关技术的应用和发展，使得从生态系统尺度对下垫面与大气之间的物质和能量交换进行长期、直接、连续地观测成为可能。深入探讨荒漠河岸胡杨林的水碳耦合特征及其对环境因子和人类活动的响应，不仅有助于完善河岸地区森林生态系统水碳耦合过程的相关理论体系，还能为额济纳绿洲的生态恢复与管理提供科学依据。本研究利用涡度相关技术对胡杨林下垫面与大气间的能量、水汽和CO2通量进行了为期四年的观测，其中2013-2016年5月至10月的通量数据被用于该研究。在收集荒漠河岸胡杨林生态系统的涡度通量数据、土壤数据、地下水位数据、植被数据和气象数据的基础上，结合历史研究资料和文献数据，以涡度相关技术为主要研究方法，评估了荒漠河岸胡杨林生态系统的能量闭合程度和能量分配特征，系统地分析了它的水、碳交换特征及其对环境因子的响应，重点研究了该生态系统的水碳耦合过程和机理，最后计算了生长季额济纳绿洲胡杨林总的固碳量和耗水量。主要结论如下：（1）荒漠河岸胡杨林生态系统的能量消耗以潜热通量为主，潜热通量占净辐射的72%。胡杨林生态系统蒸散量的季节变化趋势和年际差异主要受植物物候阶段、生长状况和生态系统水分状况的影响。在生长季的前期和后期，蒸散量年际差异主要受地下水埋深的影响。（2）荒漠河岸胡杨林是极端干旱区一个重要的碳汇，生长季总的净生态系统生产力为264 g C m-2，总初级生产力和生态系统呼吸分别为676 g C m-2和412 g C m-2。胡杨林生态系统的碳通量特征不受降水量的影响，与气温、辐射、水汽压亏缺密切相关。在相似的生理生态条件下，胡杨林净生态系统生产力的年际差异主要受气温和地下水埋深的影响。（3）生长季荒漠河岸胡杨林生态系统的总初级生产力为676 g C m-2，总蒸散量为864 mm，水分利用效率为0.79 g C kg-1 H2O。总初级生产力和蒸散量对气象因子的响应过程基本一致，二者均随着温度、辐射和水汽压亏缺（<3.8 kpa）的增加而增加。在生长季的不同阶段，总初级生产力和蒸散发对叶面积指数的响应过程不同：胡杨生长早期和晚期，总初级生产力和蒸散发与叶面积指数之间呈线性正相关关系，只是蒸散发与叶面积指数的相关关系较弱；胡杨生长旺季，总初级生产力和蒸散发与叶面积指数之间的关系不明显。水碳通量对气象因子和生物因子响应的相对一致性，使得水分利用效率与辐射、温度、水汽压亏缺和叶面积指数之间均没有明显的关系。只是受灌水的影响，9月胡杨林生态系统的水分利用效率随着叶面积指数的下降而下降，随温度的增加而下降。而且灌水的时间会在日尺度上影响水分利用效率的变化过程。 （4）生长季额济纳绿洲胡杨林总的净生产力为7.42×104 t C，蒸散量为2.74×108 m3，蒸腾量为0.97×108 m3，地表蒸发量为1.77×108 m3。对黑河下游地区胡杨的生长而言，适度的灌水是有益的，而大量的灌溉不仅不利于植物的生长还会增大无效的地表蒸发，导致水资源浪费。为避免水资源的浪费和土壤盐渍化程度的加剧，本研究认为胡杨生长的最适宜地下水埋深应为3.0-6.0 m。 |
| 英文摘要 | Under the background of global change, increasing population and crisis of water resources, the desert riparian forest plays an essential role in the conservation of biodiversity and development of economy of Ejin oasis. Desert riparian forest, as the primary body of the Ejin oasis, represents the majority of carbon-water coupling in hyper-arid spots. Although the area of the riparian forest in Ejin is not large, there are lot of biological importance due to abundant biodiversity, high productivity and vitality compared to surrounding deserts. Otherwise, the desert riparian forest is sensitive to the global change and human activities. So far, studies of water-carbon coupling process and mechanism in riparian forest at the lower reaches of Heihe River Basin had been characterized by small scale and short time series. However, little is known about the characteristics of water and carbon fluxes and their response to bio-meteorological conditions in the riparian forest on ecosystem scale. The use and development of the eddy covariance method has made it possible to directly and continuously measure the fluxes of matter and energy between the the biosphere and atmosphere in the long term. The further study of characteristics of carbon and water fluxes and their response to bio-meteorological conditions in desert riparian forest on ecosystem scale is necessary. It not only will be conductive to improving the theoretical system about water-carbon coupling process of forest ecosystem distributed in the riparian zone, but also helps to facilitate ecological rehabilitation and management for the Ejina oasis. Fluxes of energy, water and carbon between the forest and the atmosphere were measured using the eddy covariance (EC) method during May to October for 2013-2016 in this study. The systemic collection of the fluxes data, soil data, vegetation data and meteorological data of the riparian forest is the foundation of this research. And the eddy covariance method, a micrometeorological technique, is the main technique used in this study. Based on the assessment of the energy balance closure and energy partitioning, the characteristic of water and carbon exchange and their response to bio-meteorological conditions and human activities (i.e. irrigation) were analyzed in depth. Moreover, we focused on the carbon-water coupling process and mechanism, and then calculated the value of yearly carbon sequestration and water consumption for the desert riparian forest in Ejin oasis. The results showed as follows:(1) The latent heat flux was the main term of energy consumption at the whole growing season for the desert riparian forest. Moreover, the ratio of the latent heat flux to net radiation was 72%. The seasonal and inter-annual variaitons of evapotranspiration in the desert riparian forest was affected by plant phenology, growth and hydrological conditions. Otherwise, at the early and later growing season, the inter-annual variaitons was caused by the fluctuation of the groundwater depth caused by flood irrigation.(2) The desert riparian forest was an important carbon sink in the hyper-arid region. The cumulative net ecosystem productivity, gross primary productivity and ecosystem respiration during the growing season were 264 g C m-2, 676 g C m-2 and 412 g C m-2, respectively. The characteristics of carbon fluxes in the desert riparian forest were affected by temperature, radiation and vapor press deficit. There is no relationship between rainfall and carbon fluxes.(3) The cumulative gross primary productivity and evapotranspiration during the growing season were 676 g C m-2 and 864 mm, respectively. The ecosystem water use efficiency during the growing season were 0.79 g C kg-1 H2O. The response of gross primary productivity and evapotranspiration to climatic factors were similar, both of them increased with increasing temperature, radiation and vapor pressure deficit (<3.8 kpa). In addition, the response of gross primary productivity and evapotranspiration to leaf area index were various at the different growing stage. For example, there is a linear positive correlation between gross primary productivity and evapotranspiration and leaf area index at the early or late growing season, otherwise the correlation between evapotranspiration and leaf area index was weak. Moreover，there is no relationship between gross primary productivity and evapotranspiration and leaf area index at the vibrant growing season. The water use efficiency was not affected by radiation, temperature, vapor press deficit and leaf area index, because the patterns of the response of water and carbon fluxes to bio-meteorological factors were similar in the desert riparian forest. In September, the ecosystem water use efficiency decreased with increasing temperature and the decrease of leaf area index, which were affected by irrigation in September. Moreover, the process of ecosystem water use efficiency was affected by the time of irrigation at daily scale. (4) The total values of net ecosystem productivity, evapotranspiration, transpiration and evaporation in the desert riparian forest of Ejin oasis were 7.42×104 t C km-2, 2.74×108 m3, 0.97×108 m3 and 1.77×108 m3, respectively. Moderate irrigation is beneficial to the growth of P. euphratica distributed in the lower Heihe River Basin. However, excessive irrigation not only is unfavorable to the growth of P. euphratica, but also increase surface evaporation, resulting in wasted water resource. In order to avoid the waste of water resources and intensive soil alinization, the groundwater depth fluctuated between 3.0 m and 6.0 m will be appropriate to meet the water use demand without waste. |
| 中文关键词 | 水碳耦合 ; 荒漠河岸林 ; 黑河下游 ; 水分利用效率 ; 涡度相关 |
| 英文关键词 | Water-carbon coupling the desert riparian forest water use efficiency the eddy covariance method downstream of Heihe River |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288123 |
| 推荐引用方式 GB/T 7714 | 马小红. 荒漠河岸胡杨林生态系统水碳耦合特征及其影响因素研究[D]. 中国科学院大学,2018. |
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