稳定性同位素技术与Keeling曲线法在陆地生态系统碳/水交换研究中的应用

doi:10.17521/cjpe.2005.0113

摘要/Abstract

摘要：

稳定性同位素技术和Keeling曲线法是现代生态学研究的重要手段和方法之一。稳定性同位素能够整合生态系统复杂的生物学、生态学和生物地球化学过程在时间和空间尺度上对环境变化的响应。Keeling曲线法是以生物过程前后物质平衡理论为基础,将CO₂或H₂O的同位素组成(δD、δ¹³C或δ¹⁸O)与其对应浓度测量结合起来,将生态系统净碳通量区分为光合固定和呼吸释放通量,或将整个生态系统水分蒸散区分为植物蒸腾和土壤蒸发。在全球尺度上,稳定性同位素技术、Keeling曲线法与全球尺度陆地生态系统模型相结合,还可区分陆地生态系统和海洋生态系统对全球碳通量的贡献以及不同植被类型(C₃或C₄)在全球CO₂同化量中所占的比例。然而,生态系统的异质性使得稳定性同位素技术和Keeling曲线法从冠层尺度外推到生态系统、区域或全球尺度时存在有一定程度的不确定性。此外,取样时间、地点的选取也会影响最终的研究结果。尽管如此,随着分析手段的不断精确和研究方法的日趋完善,稳定性同位素技术和Keeling曲线法与其它测量方法(如微气象法)的有机结合将成为未来陆地生态系统碳/水交换研究的重要手段和方法之一。

关键词: 稳定性同位素, Keeling曲线, 通量区分, CO₂再循环, 陆地生态系统

Abstract:

Stable isotopes are used as both natural integrators and tracers of complicated biological, ecological and biogeochemical processes, and their responses to environmental changes at different spatial and temporal scales. In this article, the application of stable isotopes and the Keeling plot approach to carbon and water exchange studies of terrestrial ecosystems were reviewed. We focused mainly on the current applications and potential development of stable isotope techniques and the Keeling plot approach in conjunction with concentration and flux measurements of CO₂ and water in terrestrial ecosystems. For these applications it is critical to know the isotopic identities of specific ecosystem components, such as the isotopic compositions of CO₂, organic matter, liquid water, and water vapor, as well as the associated isotopic fractionations, in the soil-plant-atmosphere continuum. Based on the principle of mass conservation, the Keeling plot approach combines measurements of stable isotope ratios and concentrations of CO₂, water or other trace gases, and allows the identification of the contributions of various ecosystems, or ecosystem components, to the net exchange fluxes between the terrestrial biosphere and atmosphere, and the estimation of net ecosystem isotopic discrimination and disequilibrium effect. Net ecosystem carbon fluxes can be partitioned into C uptake during photosynthesis and C release during respiration or evapotranspiration into leaf transpiration and soil evaporation by the Keeling plot technique. This approach also allows partitioning urban CO₂ sources into gasoline combustion, natural gas combustion and biogenic respiration. Recent modifications of the Keeling plot approach permit examination of CO₂ recycling in forest ecosystems. At the global scale, we can estimate relative contributions of terrestrial and ocean ecosystems to the global carbon cycle by combining stable isotope techniques, the Keeling plot approach and terrestrial ecosystem models. However, applications of stable isotope techniques and the Keeling plot approach to ecological research are sometimes constrained by the heterogeneity of terrestrial ecosystems. In addition, selection of suitable isotopic sampling protocols is another factor that we should consider in its application. Nevertheless, with new improvements in analytic protocols in the near future, stable isotope techniques and the Keeling plot approach will become one of the most effective techniques for understanding carbon and water relationships in terrestrial ecosystems.

Key words: Stable isotopes, Keeling plot approach, Flux partitioning, CO₂ recycling

孙伟, 林光辉, 陈世苹, 黄建辉. 稳定性同位素技术与Keeling曲线法在陆地生态系统碳/水交换研究中的应用. 植物生态学报, 2005, 29(5): 851-862. DOI: 10.17521/cjpe.2005.0113

SUN Wei, LIN Guang-Hui, CHEN Shi-Ping, HUANG Jian-Hui. APPLICATIONS OF STABLE ISOTOPE TECHNIQUES AND KEELING PLOT APPROACH TO CARBON AND WATER EXCHANGE STUDIES OF TERRESTRIAL ECOSYSTEMS. Chinese Journal of Plant Ecology, 2005, 29(5): 851-862. DOI: 10.17521/cjpe.2005.0113

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