Turloughs are grassy hollows, sometimes extending over many acres, which, during wet weather, fill with water through subterranean passages in the rock, and empty by the same means. The rate of the rise and fall, and the duration and frequency, of the flooding varies from turlough to turlough, being dependant on several factors connected with underground drainage.

These changes are in many cases quite rapid; an appreciable amount of water can collect in one hour, and disappear in an equally short time. Some turloughs hold permanent water on their floors, others show no water at all when flooding is absent, the bottom as well as the sides being covered with a rich green sward. The effect of the frequent flooding in the turloughs is to alter profoundly the character of the vegetation. A dense covering of plants still prevails, but its composition is different from that of the limestone pavements.

The contrast between the areas which are subject to flooding and those free from it is increased because intermittent inundation and the very light deposit of limy sediment produces a sward particularly beloved by herbivorous animals, large and small. The vegetation of the turloughs is usually nibbled to the last leaf, and all are much dwarfed.

The most abundant plants are those which can best withstand submergence, or grazing, or both. There is a total absence of rushes, willows, alder and many other plants which one associates with marshes or wet ground. Many types of violet, shrubby cinquefoil and flecked marsh orchid are some of the plants which are found here.


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