The Plant Colonisation of Merse Lands in the Estuary of the River Nith

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Abstract
On a salt marsh near the Solway Firth in southwestern Scotland a study was made of the plants and the conditions surrounding them in an effort to ascertain the succession which takes place in the conversion of naked flats of mud and sand to moderately firm ground. The numerous fauna including birds, mollusks and crustaceans were noted. Observations were made on the aeration of the soil by the roots of the plants and burrowing animals. The study showed that the mud flats exposed at low tide are consolidated by the shells of cockles, the burrows of lobworms, the carapaces of crustaceans, the droppings of seabirds, and green algae; and raised by sedimentation until only intermediate flood tides submerge the land. Then Glyceria and occasionally Salicornia become established where the current is not too strong. Usually Glyceria, the pioneer and predominant plant of the marsh, creeps down by means of its stolons. The dead roots of the first plants keep the soil porous and it is aerated by the suction caused by the ebbing tide. As the height increases with sedimentation and the leavings of the birds, a sward of Glyceria, Armeria, Glaux, Plantago, Coch-learia, Aster, Suaeda, Spergulana, etc., is established which may be grazed, having high nutritive value. As the plants continue to grow thicker and finer and are grazed by cattle, sheep and geese, the sward resembles a lawn. Such conditions choke out the Salicornia, Suaeda, and Spergularia, while the Glaux plants become small and short-rooted. By the time the soil level is raised above all but storm tides, the clay loses its flocculation and porosity and, for want of oxygen, tends to become sour. Then in absence of artificial drainage it may become a swamp supporting much vegetation, especially grass, but no marsh plants except perhaps the Triglochin and Plantago.

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