Gwernaffel Dingle

Also within

Powys County

Habitats

Bracken scrub, Fast flowing river and stream

Geology & landscape

Geological Feature: Gorge / Ravine · Geological Period: Silurian

Landscape processes: Fluvial

Description

Description The site is one of the largest of Radnor’s ancient mixed broadleaved woodlands. It provides excellent examples of four distinctive nationally recognised woodland types, which together comprise a woodland whose species composition is intermediate in character between the sessile oakwoods of upland western Radnor and the base-rich dingle woodlands of southern Radnor. Locally uncommon plant species are present. The woodlands are situated in a generally steep-sided dingle developed in Silurian Shales, with a variety of aspects. The southern tributary stream passes through a small gorge approximately 5 metres deep. Much of the woodland is fenced out from stock, but the northern part of the dingle is subject to some grazing. The woodland structure is varied, with the areas of ash Fraxinus excelsior wood frequently having a well developed shrub layer of hazel Corylus avellana, and often field maple Acer campestre. An area of relatively young ash is of plantation origin, but elsewhere trees are of uneven age and include some large, mature specimens. The shrub layer is also well developed in the southern oakwood, but is sparse or absent under a type of sessile oak high forest in the west-facing northern part of the site. Locally, there is dead standing wych elm Ulmus glabra, with young suckers. Alder Alnus glutinosa is a frequent component of areas of impeded drainage, and downy birch Betula pubescens is also well represented through the site. Other trees and shrubs present include rowan Sorbus aucuparia, cherry – particularly Prunus padus, guelder-rose Viburnum opulus, red currant Ribes rubrum and crab apple Malus sylvestris. When not dominated by alder, much of the dingle streamside and lower slopes support the ash/field maple vegetation type, with abundant tufted hair-grass Deschampsia cespitosa and a species-rich herb layer which includes dog’s mercury Mercurialis perennis, enchanter’s-nightshade Circaea lutetiana, yellow archangel Lamiastrum galeobdolon, herb-Paris Paris quadrifolia and early-purple orchid Orchis mascula. In the southern arm, the gorge contributes additional species diversity with a range of mosses and ferns, including the locally uncommon oak fern Gymnocarpium dryopteris. Opposite-leaved golden-saxifrage Chrysosplenium oppositifolium is locally abundant and wood melick Melica uniflora also occurs. On the supper slopes of the southern half of the site the vegetation is a herb-rich example of the oak/bracken/bramble Quercus robur/Pteridium aquilinum/Rubus fruticosus vegetation type. As noted above the shrub layer is well developed, and locally abundant bluebell Hyacinthoides non-scripta, wood sorrel Oxalis acetosella and variable quantities of creeping soft-grass Holcus mollis and meadow-grasses Poa spp. are characteristic of the field layer. By contrast the west-facing northern part of the site is a high forest of standard oaks, with very few shrubs, and a ground layer either grass-dominated, with abundant sweet vernal-grass Anthoxanthum odoratum, or moss-dominated, with abundant Dicranum scoparium. The former vegetation type relates to a type of oak/birch/common sorrel (Quercus/Betula pubescens/Rumex acetosa) woodland, and the latter to a type of oak/birch/wavy hair-grass (Quercus/Betula pubescens/Deschampsia flexuosa) woodland in which bilberry Vaccinium myrtillus and broad buckler-fern Dryopteris dilatata are represented. There are affinities to the western sessile oakwoods, but typical western oceanic bryophyte species are not well represented. A number of non-native species have been planted within the site, as evidenced by small areas of larch, spruce, Douglas fir, beech and southern beech.

Species mentioned

Plant communities