Heathland: Greenham and Crookham Common, near Newbury.
In N-W Hampshire acid soils and heathland are rare, so seeking out a very contrasting environment is worthwhile. The plants and animals are quite different as they are surviving in acidic soils that may drain rapidly, yet nearby there could be waterlogged condition.
The script is heavily based on published materials.
This heathland is on top of a flat gravel plateau laid down at the end of the last ice age, and since then its use has been many varied, feeding pre-historic hunter/gatherers, used as common land by farmers, and later gaining significance as a military air base.
This is the largest single area of lowland heathland remaining in Berkshire and is just on the Hampshire border.
The Common is a high plateau lying between the Kennet and Enborne valleys consisting of deposits of Bagshot acid sandy clays formation over heavy London clay. This is overlain by plateau gravel deposits from meltwaters resulting from glacier retreat. It is interspersed with alkaline pockets caused by cement contamination from the runway construction and its final removal. This gives an unusual situation of acid and alkaline soils occurring in close proximity.
Greenham and Crookham Common is a special place with ancient woodlands, flower rich grasslands and the largest continuous tract of lowland heathland in Berkshire. If you were to walk around the common, you would encounter rare and protected plants and animals. You might spot birdlife such as Dartford Warblers, Skylarks, Woodlarks, Song Thrushes, Common Linnets and Willow Tits. There are 28 birds listed recorded here that appear in the Biodiversity Action Plan for the U.K. There are protected species such as the Little Ringed Plover and Lapwing in reasonable numbers. Nightjars are regular visitors in the spring and Nightingales can be heard singing on a summers evening, but their numbers are under threat.
The grasslands are rich in orchids. Other interesting flora are Solomon’s Seal and Lily of the Valley, Upright Chickweed, Knotted Clover, Heath Cudweed, Spiked Star of Bethlehem and Mochatel.
The Common is important nationally for its ecology, and as such it is designated as a Site of Special Scientific Interest to provide legal protection. The citation is copied in the Management plan.
Heathland habitat is ideal for certain species of birds because of its open nature, with just a few scattered trees and bushes for them to use as singing posts or look out points. It is also relatively warm and dry and has an abundant food source in the form of invertebrates. You may be lucky enough to hear the rich and varied song of a nightingale, or the warbling call of a skylark high in the sky.
In summer, the heath comes alive with over 30 species of butterflies including the small blue and the expertly camouflaged grayling. They are joined by dazzling displays from damselflies and dragonflies, all set to the unmistakable music of grasshoppers and crickets.
Great Crested, Palmate and Smooth Newts can be found in the many ponds and pools and specialist insects like the Grayling and Small Blue butterflies flutter around the gravelly heaths. A project exists to re-introduce the Silver Studded Blue Blutterfly. Green Tiger Beetles and Bog Bush Crickets are common in summer.
The heathland is characterised by a mixture of ling (Calluna vulgaris), bell heather (Erica cinereal) and dwarf gorse (Ulex minor), with, in some areas, an abundance of heath grass (Danthonia decumbens) and spring sedge (Carex caryophyllea), a community with a restricted distribution in England. Occasional patches of bare soil support an open acid grassland community with early hair–grass (Aira praecox), squirrel–tail fescue (Vulpia bromoides) and hair moss (Polytrichum spp). In some areas mouse–ear–hawkweed (Pilosella officinarum) is particularly abundant. Lichens are a conspicuous feature of the open patches, chiefly Cladonia spp., including the nationally scarce (C. cariosa). Dwarf cudweed (Filago minima), heath cudweed (Gnaphalium sylvaticum), bird’s–foot (Ornithopus perpusillus), and annual knawel (Scleranthus annuus) are frequent within this mosaic together with the nationally scarce fine–leaved sandwort (Minuartia hybrida) and upright chickweed (Moenchia erecta).
On damper areas the soil is colonised by many locally rare mosses and liverworts including swards of Archidium alternifolium and frequent Lophozia excisa and L. bicrenata. Also present is the nationally scarce liverwort Riccia subbifurca, the only known site in Berkshire for this small plant.
In hollows where water accumulates a flush–type community has developed with sharp flowered rush (Juncus acutiflorus), carnation sedge (Carex panicea), lesser spearwort (Ranunculus flammula) and mosses including Climacium dendroides. A calcareous influence further increases the diversity, with such plants as wild carrot (Daucus carota), dwarf thistle (Cirsium acaule), purging flax (Linum catharticum), pyramidal orchid Anacamptis pyramidalis, burnet saxifrage Pimpinella saxifrage and the mosses Trichostomum and Encalypta streptocarpa growing alongside more typically acid–loving plants.
The neutral grassland in the airbase includes locally uncommon plants such as green–winged orchid (Orchis morio), great burnet (Sanguisorba officinalis), hare’s–foot clover (Trifolium arvense) and meadow saxifrage (Saxifraga granulate).
On the southern slopes of the Common, on the terraces of gravels and sands, most of the former heathland is now overgrown with silver birch (Betula pendula), pedunculate oak (Quercus robur) and bracken (Pteridium aquilinum). This secondary woodland ground flora includes the moss Leucobryum glaucum, pale sedge (Carex pallescens), green–ribbed sedge (C. binervis) and bilberry (Vaccinium myrtillus).
The ancient woodland is dominated by ash (Fraxinus excelsior), alder (Alnus glutinosa), and hazel (Corylus avellane) with occasional hornbeam (Carpinus betulus) and aspen (Populus tremula). The ground flora includes hard shield–fern (Polystichum aculeatum), Lily of the valley (Convallaria majalis), Solomon’s seal (Polygonatum multiflorum), a species largely confined to central southern Britain, and large bitter–cress (Cardamine amara) which is on the south–western edge of its range.
A rich and varied flora characteristic of both base–rich soils and more acid conditions is typical of the alder gully woodlands. Broad buckler fern (Dryopteris dilatate) and male fern (D. filix–mas) are abundant, and scaly male fern (D. affinis) and lady fern (Athyrium filix–femina) are frequent. Other species present include marsh violet (Viola palustris), alternate–leaved golden saxifrage (Chrysosplenium alternifolium), thin–spiked wood sedge (Carex strigose), smooth–stalked sedge (C. laevigata), wood club–rush (Scirpus sylvaticus) and wood horsetail (Equisetum sylvaticum), all of which are uncommon in central England.
The two commons are rich in a wide range of invertebrates. Butterflies recorded include the purple emperor (Apatura iris), white admiral (Ladoga Camilla) and silver–washed fritillary (Argynnis paphia) from the woodland and the silver studded blue (Plebejus argus), grayling (Hipparchia Semele) and brown argus (Aricia agestis) from the heathland and grassland. The bog bush cricket (Metrioptera brachyptera) occurs on the heathland areas.
Breeding birds recorded include woodcock, nightjar, barn owl and nightingale in the woods and scrub, as well as a number of ground nesting birds in the more open habitats.
Adder (Vipera berus), grass snake (Natrix natrix), slow worm (Anguis fragilis) and common lizard (Lacerta vivipara) are found on Greenham and Crookham Commons, as are the common frog (Rana temporaria) and toad (Bufo bufo). All three British species of newt also occur; palmate, smooth and the great crested newt.
Two on-line walks are available:
Just north of Newbury is Snelmore Common, another wonderful heathland site.