Summer and winter concentrations of sodium, potassium and calcium in some maritime Antarctic cryptogams

(1) The source and availability of nutrients to the predominantly non-vascular cryptogam vegetation of Signy Island. South Orkney Islands, in the maritime Antarctic, are briefly discussed. (2) The concentrations of total Na, K and Ca were determined for fifteen species of moss, one species of liverwort, one species of alga and nine species of lichen growing in a wide range of habitats. (3) In all species examined the concentration of Na was considerably higher in summer than in winter, the difference being least in the lichens. Species occupying wet habitats or habitats near the shore had the highest Na concentrations (up to 0.53% of dry weight). There was a strong correlation between Na content in the plants and the distance both vertically and horizontally from the sea. (4) Potassium concentrations were higher than those of Na, but the concentration in summer was frequently less than that in winter, particularly in those mosses and lichens growing in relatively dry rock habitats. As with Na, the higher K concentrations appeared to be correlated with increased moisture availability, with the highest K values (up to 1.41% of dry weight) in species growing on wet rocks. (5) The concentrations of Ca varied considerably and showed little conformity in fluctuation in all groups of species. The highest concentrations of the element (up to 2.29% of dry weight) were in species associated with mineral substrata and a high Ca content. There was a strong correlation between the Ca concentration in the plant material and the pH of the substratum. (6) The difference between summer and winter concentrations of the three cations suggests the probability of an annual cycle of mineral elements within the plants, with relatively high spring to early summer levels and winter minima. However, this cycle may not be complementary with the seasonal trends in soil elements. (7) The mineral-ion concentration within the plants varied considerably, not so much in relation to species but to environment, and to some extent to growth form which is strongly correlated with environment. Different species associated with a particular habitat tended to have similar concentrations of specific mineral elements, whereas the same species growing in a variety of habitats tended to have a range of mineral-ion concentrations. (8) The simple mechanism of uptake and storage of mineral-ions in these non-vascular species is considered to be a response to the moisture regime of the habitat and to the concentration of the elements in the substratum or in precipitation. The concentrations within the plants tend to be proportional to those occurring in the substratum, although some degree of accumulation, despite the absence of specialized storage tissues, is suspected.


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Authors: Smith, Ronald I. Lewis

1 January, 1978
The Journal of Ecology / 66
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