The topography of these heaths is generally gentle and there are
large areas of low-lying land supporting humid and wet heathland
although, in places, steep hills support dry heath. Three sites,
Ash Ranges, Pirbright Ranges and Chobham Common, account for three
quarters of the heathland in the Thames Basin; nevertheless other
smaller sites have considerable importance in maintaining biodiversity
across the range of heathland within the Natural Area.
b) Wealden Greensand.
Heathland on the Wealden Greensand makes up one third (about 1,000
hectares) of the county’s heathland and forms part of a larger area
extending into Hampshire and West Sussex. With the notable exception
of Thursley National Nature Reserve and its environs (which supports an internationally
important mire), the Wealden Greensand heaths are predominantly
dry sites, lying on the Folkestone, Sandgate and Hythe Beds of the
Lower Greensand. The topography of these heaths, especially in the
south west of the area, is more varied than in the Thames Basin
– higher ground often rising steeply and forming a deeply incised
landscape as at the Devil’s Punch Bowl. The bulk of the surviving
heathland is centred on or close to Thursley, Hankley and Frensham
Commons, with Blackheath an important outlier to the north east.
Fragments of heathland at higher altitude and of different character
persist further east at Leith Hill and on the Hurtwood in the characteristic
‘Surrey Hills’ landscape, now heavily wooded.
c) North Downs
In a very few places, superficial deposits over the chalk of the
North Downs support heathland. The largest example is Headley Heath
where the more ‘typical’ acidic heathland plant communities are
accompanied by small areas of ‘chalk heath’ that are interesting
mixtures of chalk downland and heathland species. There are probably
no more than 20 hectares of heathland over the chalk.
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