Area: 10.7 hectares.
Description and Reasons for Notification:
Tidcombe Lane Fen contains a type of wetland habitat that is now scarce nationally and rare in Devon, only one other undisturbed example being known to remain in the county. The fen meadow vegetation present contains a wide diversity of plants and displays an unusual variation in its flora composition.
The site occupies the shallow valleys of the Alsa Brook and one of its tributaries, on the outskirts of Tiverton in mid-Devon. The water-logged soils are generally iron-rich alluvial gleys, with a thin humic surface layer and a moderately rich base status.
The majority of the site supports vegetation that closely conforms to the blunt-flowered rush Juncus subnodulosus–marsh thistle Cirsium palustre community, a habitat that has greatly declined in extent in recent decades throughout the county. One particularly interesting feature of the Tidcombe Lane site is that the blunt-flowered rush has been replaced as a dominant by lesser pond-sedge Carex acutiformis, so much so that the stands of this species present are matched in area by only one other tall sedge bed in the county. Otherwise, however, the site is strongly representative of the community named above.
In the wettest parts of this community, tussock sedge Carex paniculata assumes dominance, the tussocks rising above one metre high in places. An area of willow Salix sp. carr adds further structural diversity to the site.
Over one hundred species of flowering plants have been recorded. Among the most characteristic are common sedge Carex nigra var.subcaespitosa, meadowsweet Filipendula ulmaria, wild angelica Angelica sylvestris, purple loosestrife Lythrum salicaria, fleabane Pulicaria dysenterica, water mint Mentha aquatica, marsh-marigold Caltha palustris, marsh valerian Valeriana dioica, ragged robin Lychnis flos-cuculi and southern marsh-orchid Dactylorhiza praetermissa. Less base-rich conditions are indicated in places by the presence of bog pimpernel Anagallis tenella and bogbean Menyanthes trifoliata.
The better-drained parts of the site support a grass-dominated sward. Here Yorkshire fog Holcus lanatus, soft-rush Juncus effusus and creeping buttercup Ranunculus repens are particularly prevalent.
The fauna of the site is as yet poorly known but preliminary investigations have shown the presence of a species of snail new to Devon, Euconulus alderi, and another that is of restricted distribution in the south-west, Zonitoides nitidus.