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In situ observations of fossil and living specimens of the calcicolous mosses Bryum pseudotriquetrum, Cratoneuron commutatum and Catoscopium nigritum revealed very fast calcite depositional rates. Rhythmic layering in the fossil mosses corresponding with the seasonal climatic cycle suggests that the moss curtain occupied by these three mosses maintains the deposition of spongeous travertine layers at a mean rate of 4 cm a−1. A mean depositional rate of 4.2 cm a−1 may be calculated from measurements of the loss of bicarbonate from the springwater after it percolated through the moss curtain. These rates suggest that the 8 m high travertine terrace of Checa with a surface area of 800 m2 did not exist two millennia ago.Mosses could be put to man's use for creating natural overgrowths on artificial surfaces, an idea based on an allusion by Wallner. He observed that the thread-forming, blue-green algae Vaucheria builds travertine deposits at an annual rate of 0.7–1.4 cm. We observed that the mosses Cratoneuron commutatum and Bryum pseudotriquetrum may form spongeous travertine layers at respective maximum rates of 11 and 14 cm a−1. This would reduce the time required to build natural overgrowths on artificial objects to a practical period of months.

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Analysis of plant micro-and macrofossils from a sequence from Usselo (The Netherlands) allows a detailed reconstruction oflocal developments during a period of more than one and a half millennia, starting before the Belling period and lasting till the end of the Altered period. The sequence started in an oligotrophic shallow pool with a very low organic production in a barren sandy landscape. An early phase with G/oeotrichia type may be connected with the ability of N-fixation of these blue-green algae. This capacity may have initiated nutrient availability. Characeae played an important role on the initially sandy substrate. These pioneers opened up the site for other aquatics and helophytes, e.g. Potamogeton a/pinus, Carex rostrata, Phragmites australis, Equisetumfluviatile, followed by Menyanthes trifoliata, Myriophyllum spicatum and various Carex species. This sequence indicates a gradual eutrophication of the site, accompanied by an increase in production of organic matter (interrupted during the Older Dryas), as substantiated by the organic/inorganic ratio of the substrate. The tendency towards eutrophication ended when the vegetation at the mire surface lost its contact with the ground water. The sequence ended with a vegetation type dominated by Sphagnum and the occurrence of oligotraphentous Thecamoeba.These changes in local vegetation are explicable without resort to temperature fluctuations. The nutrient status of the habitat, and the water level(the latter influenced by sand and organic sediment deposition) were apparently the most important factors in the vegetation succession.