Tamnyrankin ASSI

This area is of special scientific interest because of its species-rich wet grassland.  Species-rich grassland tends to occur only where land management is not intensive, in particular where traditional farming practices have been maintained.  As a result, it is not a widespread habitat in Northern Ireland and is often fragmented, consisting of individual fields, parts of fields or banks.  Species-rich grasslands, like those found at Tamnyrankin, are a particularly scarce resource in Northern Ireland.

The area is situated in the eastern foothills of the Sperrin Mountains within the townland of Tamnyrankin, 2.7km north-west of Swatragh.  Tamnyrankin is in the marginal uplands with an altitude of approximately 190m above sea level. The underlying geology of Tamnyrankin is dominated by rocks of the Lower Basalt Formation of Palaeogene age (some 60 million years old).  This igneous rock occupies large areas of Antrim and north-east Londonderry and is the parent material from which the soils have developed.  Depending on factors such as rainfall, altitude, aspect and land gradient, basalt can have a range of soil types associated with it. At Tamnyrankin the soils are generally shallow and are of a type referred to as a Brown Ranker. These are often free draining and in places this has led to the development of heath vegetation but overall the site is wet and even waterlogged.  This may reflect the position of the site with surrounding ground delivering runoff while the soil may have a sufficiently high content of organic material and finer grade material to retain water and even impede drainage. This combination of underlying geology, topography and the related soil hydrology has resulted in a complex range of species-rich wet grasslands within a small area.