Human activity has had
a particularly profound impact on the present
character and distribution of woodland in Britain, and there is a
considerable body of evidence to give a reasonably accurate picture
of this influence and its effects. Of the major formations, only
woodland has an extensive descriptive documentary record going back
to mediaeval times. A brief account of these historical features is
therefore helpful to an understanding of the present-day woodlands.
An outline of the prehistoric
spread and development of woodland in
Britain following the last Quaternary glaciation has been given in
Chapter 2. By the time early man first began to have a significant
influence, the general pattern was of a climax forest covering the
greater part of the country up to 460-610 m (lower in western and
northern Scotland) except on ground which was too wet, unstable or
wind-exposed. Various types of broad-leaved woodland prevailed in
the south but there were extensive pine forests in the Highlands.
Much of the diversity of woodland type was then related to
variations in soil conditions and climate on the local and regional
scales.
Mesolithic man was not
a cultivator and his numbers were too small
to have much influence. The real impact of man on our forests began
with the appearance of Neolithic agriculture around 3000 B.C.
Clearance of woodland directly by cutting and burning and indirectly
by grazing of domestic stock which prevented regeneration, and its
replacement by cultivated land, began and grew on an ever-increasing
scale. Areas cleared first were the most tractable for cultivation,
mainly on well- drained sites of intermediate elevation rather than
on wet valley bottoms. Steep and rocky ground tended to be avoided,
and there was a distinct preference for the fertile soils on chalk
and limestone. As clearance spread there was an avoidance of heavy
clays, wet peats and acidic sands which were either difficult to
work or of low fertility, so that extensive areas of woodland
remained long after the appearance of Neolithic man.
The Iron Age created a
need for fuel timber and saw an onslaught on
remaining extensive forest lands which had escaped the attentions of
cultivators. Smelting by charcoal led to clearance not only in
southern areas such as the Weald, but also in remoter country such
as the Lake District and western Highlands, where extensive tracts
of primaeval forest were devastated. It is also believed that
woodland was extensively burned in situ to remove refuges for
undesirable creatures such as wolves.
In early mediaeval times,
many of the remaining extensive tracts of
woodland were set aside as Royal Forests, under whose laws the
forests were kept as hunting preserves. The forests of some of these
royal chases have survived until today as important areas of
permanent woodland, the largest and best known being the New Forest
in Hampshire. On a smaller scale, many areas were 'emparked' during
mediaeval times for the holding of deer, and most of these appear to
have incorporated remnants of the original forest. Moreover, all
communities needed a supply of fuel and construction wood, and this,
coupled with the difficulty of timber transportation, led to the
retention of relatively small woods in every parish. Land closest to
the village was cleared and cultivated first, and today many woods
are adjacent to or astride parish boundaries. There is also a
tendency for present-day woods to occupy the heaviest or poorest
soil or steepest land in the parish.
The pattern of survival
of land with a continuous Postglacial
history of woodland cover ('permanent woodland') is thus largely the
result of what might be termed ecological chance, i.e. the
occurrence of conditions which discouraged forest clearance, in
relation to developments in human needs. Moreover, although there is
evidently a good deal of permanent woodland still left in Britain,
very little, if any, of this remains in an original state. A great
deal of re- planting has taken place, often using different species
or proportions of species compared with the original, and nearly
always there has been management which has resulted in some degree
of modification. Natural re-establishment of woodland after
clearance has often occurred when conditions allowed, and there has
been extensive human re-establishment of tree cover on ground
unwooded for varying periods. This is an additional complicating
factor in understanding the present nature and distribution of
woodland. Such redevelopment of woodland cover follows a change in
land use, which often in turn results from economic change, but
there is again a connection with the quality of land involved.
Naturally re- established woodland is especially characteristic of
such places as steep slopes in the Peak District and on the North
and South Downs, and on former common grazings in infertile lowland
areas. Large areas of moorland and sheep-walk which have become
uneconomic as grazing land, and are unrewarding for other types of
land-use, have been planted in recent years. The development of
extensive ombrogenous mires from Atlantic times onwards reduced
woodland cover in northern and western Britain but, with the recent
drainage and drying out of these peatlands, conditions favourable to
tree growth are returning over some of this ground, and birch is
especially able to take advantage of this change by spreading onto
the drying mire surfaces.
Woodlands offer special
opportunities for studying the influence of
man through the long-lasting effects of management practices
inscribed in the living trees; in their form, their age-structure,
and in the detailed distribution of species and individuals of
particular ages and growth forms within individual woods. Some of
these management practices have died out or have been so reduced in
scale that their consequences and variability can no longer be
observed, but in many woodlands the detailed effects of management
can be reconstructed. Such sites are therefore of particular
importance for reaching an ecological understanding of the present
character of woodland and for studying woodland management. Woods
for which there is in addition recorded information about past
management and character are especially important.
Woodlands, together with
grasslands and peatlands, have been an
important semi-natural vegetation type in local economies. The
location of woods is a reflection of local land-use history and
settlement pattern. Their management in the past has reflected local
patterns of ownership and rights, and the local and national
requirements for wood and, to a limited extent, pasture. Many woods
are, therefore, historical monuments whose significance ranks with
that of the more obvious historical monuments such as churches,
houses, bridges and earthworks.
Throughout lowland Britain
all but the steepest and wettest ground
has been ploughed at some time, or if there are any areas of
ploughable land that have not been ploughed, it is very difficult to
establish this fact with certainty. Ancient woodlands, however, once
delimited during the land settlement process, have remained
geographically stable, and until modern forestry techniques,
including deep drainage, were introduced into some woods the soil in
these woods was disturbed only on the surface. In lowland England,
these woods are thus the only sites where guaranteed undisturbed
soil profiles now occur. In the same way detailed pre-cultivation
morphology of the ground surface has been preserved more or less
undisturbed within these woods.
If truly natural woodland
(i.e. that uninfluenced by man) now
remains in Britain, it is as small fragments in un-cultivable and
inaccessible situations, such as steep screes, deep gorges and
broken cliffs or on the islands of freshwater lakes (the smaller
islands only; many of the larger wooded islands are or have been
grazed, burned or deliberately managed). Although these natural
fragments are especially interesting to the ecologist, we must
accept that nearly all our woodlands are semi-natural or artificial.
Different forms of management have affected species composition,
stocking density, growth form and age class distribution of the
trees themselves, and in consequence the composition of both plant
and animal communities which depend upon the trees. Breaks in
woodland continuity also have important effects as many associated
species of plant and animal appear to have an extremely limited
capacity for spreading back to lost ground even when favourable
conditions are restored. Plantations and other re-established
woodlands are thus usually floristically and faunally impoverished
by comparison with permanent woodlands in parallel ecological
situations.
Traditional forms of management
have declined in recent decades and
have been replaced by practices which have very different ecological
effects. Exotic species are widely planted, including conifers, most
of which, in their dense, even-aged stands, cast a shade too heavy
for many plants and animals. Broad-leaved trees are eliminated or
reduced in number and variety and the field layer is now much more
severely manipulated, often by the use of chemical herbicides.
Drainage operations and soil disturbance occur on a larger scale
than hitherto. These activities have led to substantial changes
which have involved a marked decline in floristic and faunal
richness in many woods.
