Ecology of Alnus Glutinosa (L.) Gaertn.: II. Seed Distribution and Germination

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Abstract
Running water and wind-drift over standing water are shown to be the chief agents of dispersal of A. glutinosa in Britain, and this has important effects of seedling establishment and the form of populations. There is considerable variation (0-80%) in the viability of the seed set and low viability is almost wholly due to the failure of embryo formation. Optimal germination takes place at about 26[degree]C and is independent of light, normal temp. fluctuations and pH of substrate. High oxygen tension and high humidity in the surrounding air are necessary for satisfactory germination. Cold treatment of damp seeds at 0-4[degree]C for at least 6 weeks reduce the min. germination temperature from 18 to 7[degree]C and this has important ecological implications. The course of germination is described for laboratory and field seedlings. An important feature is the relative weakness of radicle elongation and the liability of the radicle to suffer damage by low temperature and incipient drying in the early stages of germination. This partly explains the hydrophytic behavior of the sp.