The Silver Flowe: III. Pattern Development on Long Loch B and Craigeazle Mires

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Abstract
A general description of the vegetation of Long Loch and Craigeazle mires, Southwest Scotland, is given, with particular emphasis on the microtopographical variation (pattern) of the mire surface. On Long Loch mire the pattern consists of groups of permanent pools with a sparse flowering plant and bryophyte flora, hollows that are periodically dry and contain an almost continuous bryophyte cover, and intervening ridges, flat areas (lawns) and hummocks. Groups of pools overlie basins in the mineral material, while areas of hummock-hollow pattern overlie slopes and terraces. The stratigraphy shows that extension of pools and hollows on Long Loch mire occurs by the flooding of adjacent areas of formerly exposed vegetation. Similar observations on Craigeazle mire suggest that Sphagnum papillosum and S. magellanicum carpets can invade hollows filled with aquatic species of Sphagnum and also that hollows can extend over lawns of Sphagnum. Continuous records of water-level fluctuation reveal that during prolonged dry periods the fall of water-level changes at a certain depth, called the critical level, from continuous to stepwise with a 24-h period. Water is lost by run-off and evapotranspiration above the critical level but it is probable that very little, if any, water is lost by run-off below it. The critical level is nearer the surface in the neighborhood of pools than it is in areas of hummock-hollow mire. Intermittent measurements of water level in tube wells installed in patterned and non-patterned parts of Long Loch mire show that the amplitude of water-level fluctuation decreases in the sequence non-patterned, hummock-hollow and pool-ridge mire. An explanation of pool evolution based on the relief of the underlying mineral material, hydrological features and the ecological features of aquatic species of Sphagnum is given. Apparently, in the climate of the Silver Flowe, hollows are inherently unstable and gradually develop into pools unless they are temporarily invaded by semi-aquatic species of Sphagnum such as S. papillosum.

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