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Two tundra Polytrichum moss species were sampled in the field near Barrow, Alaska, three times during the growing season. Lipid, sugar, and starch concentrations of the green above ground shoots and below ground rhizomes were analyzed. Lipid and TNC (sugar + starch) concentrations were higher in Polytrichum commune growing on raised polygon rims than in Polytrichum alpinum. There were no significant differences between the two populations of P. alpinum. Green parts had significantly higher lipid concentrations than rhizomes in P. commune but not in P. alpinum. Both species had significantly higher sugar concentration in green shoots and higher starch concentrations in the rhizome and sugar concentration varied significantly in both species. Seasonal variation of TNC concentration levels were significant only in P. commune. A statistically significant positive relationship was found between lipid and TNC concentration while a stronger statistically significant negative relationship was found between sugar and starch concentration. The first is interpreted as an adaptation to drought in surface waxes and osmoticum while the second is interpreted as conversion indicator depending on tissue and use. Polytrichum mosses resemble evergreen vascular plants in their seasonal stability of these compound groups.
Sveinbjörnsson et al. (Tue,) studied this question.