Hölttä T, Vesala T, Perämäki M, Nikinmaa E
Department of Physical Sciences, University of Helsinki, FIN-00014, Finland.
J Theor Biol. 2002 Mar 7;215(1):23-38. doi: 10.1006/jtbi.2001.2485.
A model for embolism in the sapflow process was developed, in which embolism is described as a physical process linked to real physical properties of the conduits and the thermodynamic state of water. Different mechanisms leading to embolism and their effect on water relations and especially diurnal diameter changes in a tree were examined. The mechanisms of heterogeneous nucleation, air-seeding, and bubble growth have been considered. The significance of embolism has been revealed here by examining diameter changes, which is an easily measurable quantity under field conditions. The most fundamental effects of embolism on sapflow are decrease in permeability and release of water from embolizing conduits to the transpiration stream. These can be indirectly detected by observing diameter changes. If possible changes in elasticity are not accounted for, embolism generally tends to enhance the amplitude of the diurnal diameter changes due to reduced permeability and increased tensions. In the case of reduced elasticity, embolism gives rise to smaller amplitudes of diameter changes.
建立了一个用于描述液流过程中栓塞现象的模型，其中栓塞被描述为一个与导管的实际物理特性以及水的热力学状态相关的物理过程。研究了导致栓塞的不同机制及其对水分关系的影响，特别是对树木昼夜直径变化的影响。考虑了异质形核、空气进入和气泡生长等机制。通过研究直径变化揭示了栓塞现象的重要性，直径变化是在野外条件下易于测量的量。栓塞对液流最基本的影响是渗透率降低以及栓塞导管中的水释放到蒸腾流中。这些可以通过观察直径变化间接检测到。如果不考虑弹性的可能变化，由于渗透率降低和张力增加，栓塞通常会增强昼夜直径变化的幅度。在弹性降低的情况下，栓塞会导致直径变化的幅度变小。
