Institute of Ecology, University of Innsbruck, Sternwartestr. 15, 6020 Innsbruck, Austria.
Plant Cell Environ. 2012 Apr;35(4):657-67. doi: 10.1111/j.1365-3040.2011.02451.x. Epub 2011 Nov 14.
The theoretical basis for the link between the leaf exchange of carbonyl sulfide (COS), carbon dioxide (CO(2)) and water vapour (H(2)O) and the assumptions that need to be made in order to use COS as a tracer for canopy net photosynthesis, transpiration and stomatal conductance, are reviewed. The ratios of COS to CO(2) and H(2)O deposition velocities used to this end are shown to vary with the ratio of the internal to ambient CO(2) and H(2)O mole fractions and the relative limitations by boundary layer, stomatal and internal conductance for COS. It is suggested that these deposition velocity ratios exhibit considerable variability, a finding that challenges current parameterizations, which treat these as vegetation-specific constants. COS is shown to represent a better tracer for CO(2) than H(2)O. Using COS as a tracer for stomatal conductance is hampered by our present poor understanding of the leaf internal conductance to COS. Estimating canopy level CO(2) and H(2)O fluxes requires disentangling leaf COS exchange from other ecosystem sources/sinks of COS. We conclude that future priorities for COS research should be to improve the quantitative understanding of the variability in the ratios of COS to CO(2) and H(2)O deposition velocities and the controlling factors, and to develop operational methods for disentangling ecosystem COS exchange into contributions by leaves and other sources/sinks. To this end, integrated studies, which concurrently quantify the ecosystem-scale CO(2), H(2)O and COS exchange and the corresponding component fluxes, are urgently needed.
本文回顾了将羰基硫（COS）、二氧化碳（CO(2))和水蒸气（H(2)O）的叶片交换与将 COS 用作冠层净光合作用、蒸腾和气孔导度示踪剂的假设之间的理论基础，并讨论了使用 COS 作为示踪剂的前提条件，以及在这些假设下需要做出的一些假定。结果表明，用于此目的的 COS 与 CO(2)和 H(2)O 沉积速率的比值随内部与环境 CO(2)和 H(2)O 摩尔分数的比值以及 COS 边界层、气孔和内部传导率的相对限制而变化。这表明这些沉积速率比表现出相当大的可变性，这一发现挑战了当前将这些参数视为植被特定常数的参数化方法。与 H(2)O 相比，COS 更能代表 CO(2)的示踪剂。由于我们目前对叶片内部 COS 传导率的了解不足，因此将 COS 用作气孔导度的示踪剂受到阻碍。估算冠层 CO(2)和 H(2)O 通量需要将叶片 COS 交换与 COS 的其他生态系统源/汇区分开来。我们得出的结论是，未来 COS 研究的重点应该是提高对 COS 与 CO(2)和 H(2)O 沉积速率比值及其控制因素的变异性的定量理解，并开发用于将生态系统 COS 交换分解为叶片和其他源/汇贡献的操作方法。为此，迫切需要开展综合研究，同时量化生态系统尺度的 CO(2)、H(2)O 和 COS 交换以及相应的分量通量。
