Habitats in Britain &
Europe
1 - Forests and woodlands
2 - Grasslands and scrub
3 - Heathlands and moors
4 - Coastal habitats
Forests
Hazel
coppice with scattered mature oaks - a transitional woodland habitat
ideal for species such as Pearl-bordered Fritillary and Duke of
Burgundy �
Adrian Hoskins
Transitional woodland
There
are many different types of woodland in Britain, most of which are
plantations of oak, beech or conifers, managed by the government
agency Forest Enterprise.
Only a small number of
woods are now privately owned. Most of these are managed for timber,
and a tiny number are coppiced.
In coppiced woods the trees are
cut near the base of the trunk, which stimulates the growth of new
shoots. The shoots are used mainly for hurdle making or charcoal
production. Coppiced
woodlands are of huge value as butterfly habitats. The regular cutting
regime stimulates a continuous stable supply of larval foodplants and
adult nectar sources. It also creates a warm sheltered environment
that is ideal for butterflies.
Sweet chestnut.
After 8-12 years the shoots reach a diameter of about 8", and are
harvested again.
Trees which are traditionally coppiced
include hazel, sweet chestnut and hornbeam.
Hazel coppice is
particularly valuable as a butterfly habitat.
The fallen
leaves decompose very quickly, exposing the ground to direct sunlight,
which stimulates the germination of violets, primroses,
bugle,
trefoils, wild strawberry and other larval foodplants.
In sweet
chestnut and hornbeam copses however the leaves decompose slowly,
leaving a year-round carpet of dead leaves beneath the trees. This
reduces light penetration and stifles germination of wild flowers.
Consequently butterfly diversity and abundance is considerably lower
than in actively coppiced hazel woodlands.
In most coppiced woodlands a small number
of trees are allowed to reach maturity. These include oak, ash and
beech, sometimes supplemented by wych elm, lime or field maple. The
shrub layer also invariably includes several incidental species such
as
buckthorn, hawthorn, blackthorn,
sallow,
holly and
birch. A coppiced woodland thus includes a great diversity of trees,
shrubs, herbaceous plants and grasses, providing foodplants for many
caterpillars, and a variety of nectar sources for adult butterflies.
Butterflies confined
mainly to transitional woodland habitats include Wood Whites, Heath
Fritillaries, Pearl-bordered Fritillaries and Small Pearl-bordered
Fritillaries. Many other species also use such places as supplementary
or secondary habitats. These include Duke of Burgundy, Grizzled
Skipper, Dingy Skipper, Holly Blue, Orange tip, Green-veined White,
Brimstone, Peacock and Comma.
When
coppiced woodland reaches maturity the amount of light reaching the
forest floor diminishes, the herb layer virtually disappears, and
butterflies are unable to continue breeding.
Unfortunately most butterfly species have very poor powers of
dispersal and rarely travel more than about 100-200 metres from their
emergence site. It can take several years for successive generations
to find a new breeding area. During the intervening years they
struggle for survival, existing in only very low numbers, breeding
along the edges of sunny woodland rides.
Woodland
managers can help butterflies to win their struggle for survival by
creating networks of sunny rides which can be used as migration
corridors. If butterfly diversity and abundance are to be sustained it
is vital that the coppice cycle is maintained. This ensures a varied
age structure and diverse range of habitats, rich in the foodplants
and nectar sources on which butterflies depend.
Conditions similar to those of coppiced woodland can be found in
other transitional habitats such as the corridors of regularly
cleared woodland beneath electricity pylons, or sunny railway
embankments in wooded areas.
Ancient woodland
The New Forest in Hampshire is a
unique area. It covers an area of over 57000 hectares which is
largely managed by the government agency Forest Enterprise. It
comprises of a mosaic of heaths, mires, pastures, conifer
plantations and ancient oak / beech forest.
Records show
that a century or two ago it was the richest area of Britain for
butterflies, supporting a vast number of woodland, heathland and
grassland species. Sadly that is no longer the case. Wild ponies and
domestic cattle have been allowed to wander within the forest, and
grazing has been so intensive that the herb layer of much of the
area has disappeared, decimating butterfly populations.
Recently
a more enlightened management policy has improved the situation. A
small number of inclosures are now beginning to regain their former
glory, with violets, bugle and other wild flowers reappearing.
Consequently many species including Pearl-bordered, Dark Green and
Silver-washed Fritillaries are now flourishing.
Mature oak woodland in the New Forest �
Adrian Hoskins
Broadleaf and conifer plantations
The vast majority of
modern forests in Britain are plantations.
Some
are in private hands but most are state owned.
These
forests are typically broken up into small blocks of between 1-6
hectares in area, divided by firebreaks. Often several species of
tree will be planted, but each individual block will consist of a
monoculture of conifers such as pine, spruce, larch, cypress and fir
trees.
Butterflies cannot survive in the gloom within conifer plantations,
but when the trees are felled and sunlight once again reaches the
forest floor, millions of dormant seeds germinate, carpeting the
ground with violets, trefoils and bugle - the nectar sources and
larval foodplants of butterflies.
This abundance of food
sources however is very short-lived, because within about 4 or 5
years, the new trees will have grown sufficiently to shade out the
herb layer.
If
butterfly colonies are to survive, it is vital that plantations are
managed so that new clearings are created every year or two, to supply
a continuous availability of suitable breeding habitat. It is also
essential to give the butterflies a helping hand so that they can
easily and quickly find their way to suitable new areas of breeding
habitat. This can be done by creating wide sunlit rides which act as
migration corridors between the forest blocks. Scalloping ride edges,
and enlarging intersections provides additional temporary habitats
where butterflies can breed.
Pine
plantations are dark dismal places where butterflies cannot survive �
Adrian Hoskins
Timber nowadays offers little financial
return, and this fact, together with increasing public demand for
leisure facilities has brought about a change in Government forestry
policy. The tendency now is for the plantations to be periodically
thinned, rather than clear-felled and replanted, and for the woodlands
to become retained for their amenity value - many former timber
plantations are now Country Parks.
The edges of the tracks
and rides in plantations are often planted with a narrow strip of
amenity broadleaves such as oak, sallow, buckthorn, field maple and
wych elm. There are also often a few ornamental species such as
scarlet oak, sycamore, lime and cherry.
Most woodland blocks are
edged with drainage ditches and small embankments, while other
habitats may include small semi-permanent glades, grassy avenues,
riversides and ponds. A modern woodland is thus comprised of a
multitude of sub-habitats which support many native trees, shrubs and
bushes. The structure of the woodland usually ensures that there is an
abundance of sheltered sunny areas, supporting a rich variety of
grasses and wildflowers growing along the ditches, embankments and
ride edges.
Wide
grassy forest rides can be thought of as "linear meadows". Vetches,
trefoils and violets growing along the ride edges are used as larval
foodplants by many species, as are buckthorn, sallow, dogwood and
holly. Nectar sources also abound - hemp agrimony, thistles, bugle
and bramble each attracting numerous butterfly species.
The consequence of this
rich botanical variety is that many plantations in southern Britain
support not only true woodland butterflies such as Silver-washed
Fritillary, Purple Emperor, White-letter Hairstreak, Purple
Hairstreak and White Admiral, but also often have populations of
species normally associated with scrubby grassland - e.g. Dark Green
Fritillary, Brown Hairstreak, Grizzled Skipper, Dingy Skipper, Large
Skipper,
Marbled White,
Meadow Brown, Ringlet
and Gatekeeper.
Most species however
exist at very low densities and there is an absolute and immediate
need for landscape-level conservation management to be implemented
to prevent their continuing decline and ultimate extinction.
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