Wetland
One major pragmatic consideration has
governed the management of the greater
part of the area within the present perambulation of the New Forest since the
eleventh century, and possibly before. The appropriation of the area by the Crown,
and its subsequent peculiar legal status as Royal Forest, prevented the reclamation
and cultivation of some 67,000 acres of land, even though the technical difficulties
of reclaiming even the most infertile soils were largely overcome during the
eighteenth century and despite the land hunger in Lowland Britain during the past
two hundred years. Within this 67,000 acres of Crown lands, successive Acts of
Parliament since 1698 provided for the enclosure of land by the Crown for the
growth of timber, and there are today about 19,600 acres of statutory silvicultural
enclosures, of which not more than 17,600 acres may be behind fences at any one
time.
Apart from roughly 2,300 acres which are
absolute freeholds of the Crown, the
remainder of the Crown lands, about 44,500 acres, are common grazings
embracing a mosaic of heathland, bog and woodland.
Bog and wet heath occupy a total area
of something of the order Of 7,000 acres of
the unenclosed Hampshire New Forest and are characterised by accumulations of
organic material-peat-in valleys and basins. The most extensive of the bogs occur
in the southern half of the area, where contour is gentlest and water receiving areas
tend to be wide and shallow with comparatively slow stream movement.
The Beaulieu River drains a complex of
heathlands, mainly on Barton Sands, lying
to the east of the central woodlands. Gravels overlay the higher heathlands, whilst
there are gravel deposits in the shallow valley of the Beaulieu River itself. In general
both the plateau gravels and the Barton Sands are strongly leached and dominated
by heather. Most of the small scattered areas of woodland-for example Pig Bush,
King's Hat Inclosure, Foxhunting Inclosure and Crab Hat Inclosure-occur on isolated
exposures of the Headon Beds. The extensive valley bogs in the area carry deep
accumulations of peat, all of which have been worked extensively in the historically
recent past. Peat workings show clearly on aerial photographs.
The Beaulieu River has left a wide deposit
of alluvial material along its valley, which
is characterised by a stream-side belt of deciduous woodland, alternating with
extensive 'lawns' which show up as bright green ribbons against the darker heather
of the adjacent heathland. Matley Bog, Denny Bog, and three short lateral bogs
draining into the Beaulieu River off Matley Heath, exhibit classic alder carr
development with flanking zones of bog and wet heath.
The Avon Water drains an area in the extreme
south-west of the Forest. Running
throughout its course on Headon Beds, it receives notably more base-rich water
than most Forest streams. and probably for this reason its valley bogs and flanking
grasslands are characterised by a notably rich flora.
Again, the aerial photographs show the
remains of formerly extensive peat The
expanse of Forest drained by the Millersford Brook, Black Gutter, the Latchmore
Brook, the Dockens Water and the Linford Brook-the northernmost of the water
courses draining west into the River Avon embraces the largest area of the Forest
undissected by main roads or lanes; at the same time it has a spaciousness in
many respects comparable to that of the higher moorlands of Exmoor and
Dartmoor. The streams today are of no great volume, but their forerunners have
bitten deeply into the Bracklesham and Bagshot Beds underlying the Plateau
Gravels. The northernmost of the streams-Millersford Brook and Black Gutter -run in
valleys lying between ridges which remain consistently above 300 ft Ordnance
datum, the valley bottoms lying 100 150 ft below. Working south, the Latchmore
Brook and Dockens Water valleys are comparatively wide-at Latchmore Bottom,
about a mile from ridge to ridge-and the intervening plateau has in parts been
reduced to low, undulating heathland; Barton Clays and Bracklesham Beds are
successively exposed along the flanks of both valleys. Further south still, the valleys
of the Linford Brook and Foulford Bottom are occupied by exposures of Barton
Clay, with Barton Sands outcropping on the extreme upper slopes immediately
below the Plateau Gravel.
Except where plantations have obscured
the patterns of the vegetation, the valley
slopes of these streams present a mosaic of wet heath, acid grassland-usually
associated with bracken and gorse-and relict woodland, whilst the plateaux are
dominated uniformly by heather. Almost all the valley slopes exhibit in some degree
the sudden breaks in slope caused by seepage at the junction of permeable with
impermeable material-often the junction of the plateau gravels with clay-below
which wet heath and bog conditions appear to have encouraged the 'slumping' of
the valley slope.
Streamside lawns on alluvial deposits
are a recurring feature of the valley floors in
their lower reaches, whilst in the upper reaches bog, associated with an
inconsiderable depth of peat, is more usual.
The commencement of peat formation appears
to have been associated with two
main factors, the presence of impermeable material of transported origin in the
valleys; and the receipt of drainage and run-off water from the surrounding area.
Subsequent development has depended largely on the shape of the valley and the
volume of water entering it. With the onset of significant peat accumulation, the
valley bogs will have become increasingly water-retentive, which will have further
assisted the peat forming process. Where valley drainage has remained
unimpeded, often because the transported material which infilled the valley was
permeable, accumulations of humose, iron-rich alluvium have given rise to the valley
lawns.
No systematic investigation of the peat
deposits in New Forest valley bogs has
been attempted, but it is known that depths of up to 5 ft are common, and a depth of
about 20 ft has been recorded from Cranesmoor bog (SU195029). From pollen
analyses of the Cranesmoor peats it has been concluded that peat rapidly infilled a
wide shallow basin during Boreal and Pre-Boreal times. There was no evidence of
deposits more recent than the late Boreal or early Atlantic, though Seagrief clearly
recognised that the upper layers of the peat might have been removed in recent
times and the later pollen record thus destroyed. In fact, on air photographs
Cranesmoor, and indeed all the more extensive valley bogs of the Forest, exhibit
signs of systematic disturbance. These take the form of parallel lines across the
bogs at close and more or less regular distances which, when examined on the
ground appear to be slight ridges left between excavations, presumably for the
peat. The period during which excavation took place is unknown. From the remark
in the Government report of 1789 that 'those who make a trade of cutting peat and
turf, for sale, are becoming so daring as to threaten the burning of the Forest if they
are interrupted'4 it would seem likely that many excavations are fairly recent. Others
may have been medieval or earlier. At all events they have effectively truncated the
peat (and pollen) profile. Pollen analyses from sites carefully chosen as being the
least disturbed by man are badly needed, both for an elucidation of the more recent
history of peat accumulation and to provide a post Atlantic pollen record which may
be compared with the results of soil-pollen analysis.
Valley bogs
An essential ecological feature of the
valley bogs is that they receive some of the
products of leaching on the higher ground and they are thus in general likely to be
comparatively base-enriched, the degree of enrichment depending largely on the
base status of the materials from which they receive soil water. Soil water derived
from the Headon Beds or Barton Clays may be decidedly base-rich, as in the
central water courses on Denny Bog (SU347053), Matley Bog (SU335073) or
Holmsley Bog (SU240002), whilst that derived from sands and gravels may be
neutral or acid in reaction, as at the heads of Backley Bottom (SU223085), Harvest
Slade Bottom (SU216070) or Buckherd Bottom (SU214083).
In a comparative study of a number of
valley bogs in the Forest, three main plant
communities were distinguished, the distribution of each of which appears to be
determined mainly by the base status and distribution of the water flow through the
bog.
Where the central water flow of a bog
is alkaline in reaction the vegetation forms a
distinctive lateral zonation. The water course itself will usually be flanked by alder
carr with tussocks of the sedge Carex paniculata. In the middle or lower reaches of
such a bog the water course tends to become canalised into a definite stream,
which has often cut down through the peat into the underlying material. Flanking the
central carr, where the soil water tends to be intermediate in reaction and slow-
moving, occur communities in which purple moor grass is consistently present,
sometimes to the virtual exclusion of other species, but which variously include as
main components: bog myrtle (Myrica gale), bog-rush (Schoenus nigricans), reed
(Phragmites communis), bog-bean (Menyanthes trifoliata) and marsh cinquefoil
(Potentilla palustris).
On drier sites, particularly where the
central stream has bitten into the subsoil and
increased lateral drainage, bog myrtle may form a distinctive zone alongside the
carr, whilst the reed/bogbean/marsh cinquefoil assemblage occurs on the wetter
parts. These communities finally give way to an outer bog-zone dominated by
Sphagnum mosses, through which there is a diffuse seepage of basepoor water.
Purple moor grass is prominent in this outer zone, whilst a wide range of species,
including cross-leaved heath, bog asphodel (Narthecium ossifragum), sundew
(Drosera spp.), white beaked sedge (Rhynchospora alba) and cotton grass
(Eriophorum augustifolium), occur in both this and the flushed communities.
The Sphagnum-rich zone will in turn be
flanked by wet heath. The wet heath
community includes heather, cross-leaved heath, purple moor grass, lichens and
various species of Sphagnum moss, and is characterised by very shallow peat
formation. Associated species include sundew, brown-beaked sedge
(Rhynchospora fusca), butterwort (Pinguicula lusitanica), and deergrass (Scirpus
cespitosus), whilst the club-moss Lycopodium inundatum is virtually confined to this
vegetation type.
Bogs receiving neutral or base-poor water
lack the central zone of heavily flushed
vegetation-the alder carr-though willow-birch carr may develop locally, whilst on
other sites, the Sphagnum dominated vegetation may extend over most of the bog.
Modifications to the idealised zonation also arise where the water flow through the
bog is split. Newbould showed that at Cranesmoor bog, for example, there were
two main lines of flushed vegetation marginal to the bog, and that the Sphagnum-
rich community had developed in the shielded area between them. As he points
out, it is a short step from this situation to a typical raised bog, though further
development in this direction is presumably precluded by low rainfall.
Biodiversity
The Forest water courses with their associated
valley bogs. together with the liberal
sprinkling of ponds, mostly of an artificial origin, form an important series of
habitats and are, like the old timber of the unenclosed woodlands, outstanding for
the wide variety, and more particularly the high density of their insect populations.
The variety of insect species recorded is impressive even though little more than
casual, irregular and fragmentary recording has been carried out for most orders.
Perhaps because they are generally relatively large and conspicuous and the total
number of species which occur in Britain is relatively small, information is probably
most complete for the dragonflies. Of the fortythree British species, at least twenty-
five occur in the New Forest. many of them abundantly. Many species of dragonfly
are very susceptible to even slight water pollution and an important feature of the
Forest streams and water courses is that by and large they are free of pollution
from domestic or industrial effluent.
In the absence of quantitative data the
high density of insect populations
associated with fresh water habitats in the Forest is difficult to demonstrate. but it is
readily apparent in the field in the late spring and summer and is clearly reflected in
the breeding distribution of the red-backed shrike, a species which is largely
dependent on an abundance of the larger insectsand especially dragonflies and
beetles-for food: of the sixty-one pairs recorded in the survey of 1961. thirty-two
pairs bred in, or adjacent to, valley bogs or along water courses, the nest often
being actually in alder carr. Of the remaining twenty-nine pairs, most bred on valley
slopes with a scrub cover at points where shelter tended to form a 'sun trap' and
where insect life was prolific to the eye.
The valley bogs are also important during
the spring and early summer as feeding
grounds, and breeding sites for duck and for the wading birds which breed on the
Forest-curlew, lapwing (Vanellus vanellus), redshank and snipe (Capella gallinago).
A survey in 1961 gave a total of sixty breeding pairs of redshank, distributed
entirely on valley bogs and associated valley lawns; this excluded two sites which in
the following year carried fourteen pairs.
Management
From even a superficial assessment it
is apparent that the Forest offers a wide
variety of food sources, the extensive use of some of which may balance the
intensive use of others. A clear implication for management of the open Forest is
that whilst it is important to retain the natural lawns and useful to extend the re-
seeded areas, it is equally important to conserve the remaining natural vegetation
types and to resist any temptation. for example. to 'improve' the valley bogs (the
main source of pony feed, by bulk) by drainage. The range of food sources
available is also clearly greater than in most other areas where commonable stock
are depastured in numbers throughout the year (for example, the West Country
moorlands). An abundance of shelter and water, and a generally mild climate-the
last rendering the herbage available to the animals for the greater part of the winter-
are further factors which render the area, in the words of G. E. B. Eyre, 'a type of
what commonable pasture land should be.'
