Area: 69.67 hectares.
Description and Reasons for Notification:
Blackhill forms an elevated ridge of Reading Beds and London Clay, overlain in part by plateau gravels, on the north-western edge of the Poole Basin. The south and west facing slopes support dry heathland grading through wet heath to bog and fringing wet woodland. Dry heath of different character covers the north-eastern slope. The site supports a variety of animals including scarce heathland spp. Former gravel workings occur on part of the ridge top.
Dry heath of the heather Calluna vulgaris / dwarf gorse Ulex minor type occurs widely and this community includes bell heather Erica cinerea and bristle bent Agrostis curtisii. On the ridge and the north-east slope particularly there is abundant bilberry Vaccinium myrtillus, an uncommon feature on the south-east Dorset heaths, occurring here in association with heather and bracken Pteridium aquilinum. Scrub of common gorse Ulex europaeus or downy birch Betula pubescens is also frequent in parts of the dry heath. There are stands of Scots pine Pinus sylvestris on part of the hill top and the southern slope.
With increasing ground water, wet heath communities occur, with heather, cross-leaved heath Erica tetralix, purple moor-grass Molinia caerulea, deer grass Trichophorum cespitosum and lichens of the genus Cladonia. At the foot of the slopes bog communities have developed dominated by a range of bog mosses Sphagnum spp. and including bog asphodel, Narthecium ossifragum, round-leaved sundew Drosera rotundifolia and, locally, bog myrtle Myrica gale.
The margin of woodland ranges from wet common sallow Salix cinerea and birch carr over tussocks of purple moor-grass and bog mosses to dry pedunculate oak Quercus robur and ash Fraxinus excelsior with some hazel Corylus avellana coppice.
The heathland fauna includes the local silver-studded blue butterfly Plebejus argus and bog bush cricket Metrioptera brachyptera. There is also a population of the rare and protected smooth snake Coronella austriaca. Restricted heathland birds of this site include hobby Falco subbuteo, nightjar Caprimulgus europaeus and the rare Dartford warbler Sylvia undata.