Ash, Birch and Alder/Willow Woodlands

ASH WOODLAND

Ash is a tree which is particularly associated with limestone areas. The Undercliff, near Lyme Regis in Dorset, is a typical example of an Ash woodland, with the trees perched on steep limestone hillsides.

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Ash trees have finely divided compound leaves and a fairly loosely branched overall structure. As a result, they cast a relatively light shade which allows a variety of other plants to grow beneath them. There is therefore often a rich shrub and field layer in Ash woodlands.

The associated plants are frequently also lime-loving species, so Hart's Tongue Fern is a common associate growing on the woodland floor, as is Lesser Celandine. This can create glowing golden carpets of bright yellow flowers beneath the trees in early spring.

While Ash is not particularly favored by invertebrates, supporting only 41 different species (roughly one tenth of the number supported by Oak), it is rich in its lichen flora, supporting 255 different species of lichen.

In areas suitable for the growth of Beech, Ash woods will often in time give way to a later succession of Beech woodland. However, in areas unsuitable for Beech, Ash may be the natural climax community of the area.

BIRCH WOODLAND

There are two common native species of Birch in Britain, Silver Birch, Betula pendula, and Downy Birch, Betula pubescens. Both species favor acid soils, with Silver Birch tending to occur on sandy, gravely soils, while Downy Birch prefers wetter soils and a cooler climate. Neither species is commonly found on chalk. The two species can often be found together in the same areas.

	Birches are pioneer tree species, often rapidly colonizing areas such as forest clearings and heathlands with their tiny wind-blown seeds. This begins a process of succession which will eventually convert the area into woodland, provided there is no outside intervention in the form of grazing or human activities. Scots Pine (left-hand tree) and Birch (right) are both pioneer tree colonizers of heathland areas.
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	Birches are not long-lived trees, rarely exceeding 80 years old. As a pioneer species they also require fairly high light levels. Therefore, as other slower-growing tree species such as Oaks grow up around them, the Birches will begin to be shaded out. Their relatively slender forms will gradually be over-topped and out-competed by the more dominant trees. In time then, many Birch woodlands will give way to Oak woodland in a natural succession.

Birches are very hardy trees. They were among the first tree species to establish in Britain after the Ice Age retreated. They are therefore also one of the dominant woodland trees in the more extreme climate of Northern England and Scotland, together with other hardy natives such as Scots Pine and Rowan.

Birch woods may have a very diverse invertebrate life as the trees will support over 300 different species of insects and mites. This in turn attracts a variety of birds, particularly willow warblers and chaffinches. Birch also has a number of fungi associated with it including Fly Agaric (the red toadstool with white spots of Fairy rings) and a variety of bracket fungi.

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