Transcript Document

UK ancient
woodlands
Peter Shaw
Introduction
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An initial reaction to hearing the word
‘conservation’ is ‘save the rainforests’.
Yes, splendid – but we have ancient
forests of our own. Some of the
communities therein are so scarce as to
make our ancient woods important at the
European level.
What I want to achieve today:
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that you understand what is meant by an
ancient woodland, and how to identify it.
To name some characteristic species of
ancient woodlands.
To teach you management techniques
suitable for these systems.
Preamble:
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You must understand that woodland is part of a larger
ecological process: terrestrial succession. Bare ground is
colonised by short-lived plants, which are shaded out by
scrub, shaded out in turn by forest trees.
Curiously, the trees in a wood tell you rather little about its
history. 100 year old systems look very similar to 10,000
year old – at first sight!
You need to distinguish 3 types of woodland:
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plantations: monocultures with even-aged trees in regular
rows. Often desperately dull. (Though our only golden
orioles nest in poplar plantations near Cambridge).
secondary woodland. This is woodland developed on waste
ground following human clearance.
ancient woodland. This is formally defined as woodland
continuously present since 1600, but carries the strong
implication of continuous woodland cover going back to the
last ice age.
The UK climax
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Any succession progresses
towards a climax community. Over
most of the UK, the many different
natural successions head towards
the same climax: oak woodland.
We have 2 native oaks: durmast
oak Quercus robur, and sessile oak
Quercus petraea.
These differ in their leaf stalks
(petiole) - absent in Q. robur.
Other oak spp have been widely
introduced, and all hybridise!
Local variants:
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On southern chalk, yew Taxus
baccata forms dense stable
forests.
In places beech woods develop,
usually chalk.
Limestone supports ash (Fraxinus
excelsior) woodland.
Wet soils head towards alder
(Alnus glutinosa) carr, often with
willows Salix spp.
Scots pine Pinus
sylvestris
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This is such a common,
widespread plant invading so many
heaths that we tend to assume it is
natural.
In fact the only wild populations are
in Scotland (more later) - all
English & Welsh pines are derived
from recent plantings.
(And we have no native spruces at
all).
Juniper Juniperus
communis
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The “common” juniper is one of our
3 native gymosperms - with a very
odd distribution.
It occurs as a nurse species to yew
on chalky soils in the south - Box hill
has a small population.
It also occurs under pines in the
highlands of Scotland, apparently as
the same species.
(This both flavours and gave its
name to gin)
Birch Pine
oak
grass
arable
Identifying ancient woodland
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There is only one formally correct solution here:
identify maps of your woodland going back before
1600, and check for continuous presence.
Luckily, there are signs that give away truly ancient
woodland without the need for archive-searching.
Medieval forest banks
 indicator species.
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Ancient woodland indicators
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These are organisms which are highly
adapted to the stable, predictable cycle
of conditions in woods but which are
poor at long-range colonisation. They
include insects, fungi and lichens, but the
easiest group to learn are the vascular
plants.
Ancient woodland indicator plants are
typically vernal species – flowering in
spring just as the leaf canopy starts to
cast shade.
They often reproduce clonally in
preference to sexually – creeping
sideways rather than dispersing seed on
the wind.
Dogs mercury Mercurialis
perennis. Unlovely, but a
good AWI in western UK
(less so in the east, oddly).
The worst sex life of any
UK plant.
Bluebells – poor
seed dispersers, but
often planted by gardeners.
Wood anemone or
windflower, Anemone
nemorosa. One of the
most reliable AWIs.
Lily of the valley
Convallaria majalis– a good
AWI but beware garden
transplants!
Herb Paris Paris quadrifolia.
Less obvious species:
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From a European perspective, UK ancient woodland is valuable
because of 2 groups. Both are very easily overlooked!
Group 1: Epiphytic lichens – we have some of the richest
woodland lichen floras in Europe due to our stocks of ancient
oaks (especially in park woodland, where the bark receives
plenty of sunlight).
Park woodland, which supports rare
lichens such as Lobaria pulmonaria
Group 2: Saproxylous
assemblages
The most valuable
trees are those
standing but
decaying inside.
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Our real speciality are the communities of
animals and fungi found in standing but
decaying timber. These communities are
known as saproxylous, and turn out to be
exceedingly slow to colonise new trees. The
dominant animals are wood-boring beetles,
which graze on fungus-rotted timber.
Oaks planted by Capability Brown in the
1700s have only just started to acquire a few
of the commoner saproxylous species.
Many of these are very host-specific: one
beetle is only found in standing beech trees
where the core has been hollowed out by a
particular brown-rot fungus.
The Rhinoceros beetle
Sinodendron cylindricum
Ampedus cardinalis - a very rare
beetle of brown-rotted oak
heartwood
The hairy fungus beetle Mycetophagus piceus feeds on the fungus
sulphur polypore inside decaying trunks. It is fed on by the larvae of a
rare click beetle Lacon querceus - only found in Windsor forest.
Our rarest beetle is saproxylous: the violet click beetle Limoniscus
violaceus. It was thought to be confined to one tree stump in Windsor –
which was badly damaged by the 1990 hurricane. I gather that a second
stump has been found in the midlands recently!
Traditional management:
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A key aim for preserving specialist species is to maintain a
continuity of management. What has always been done?
Then do it!
The commonest form of management was coppicing, in which
trees were cut to ground level on a 5-10 year cycle, for
firewood. Often a few mature trees were left for timber – this
is known as ‘coppice with standards’.
The effect of coppicing is to maintain a mosaic of habitats,
with warm sunny glades and dense shady patches.
Woods need to be disturbed!
Traditionally woods were heavily used, with soil disturbance by foresters
and their horses etc.
At least one group of insects have declined dramatically for want of
disturbance. These are the five spp. of violet-feeding fritillaries (pearl
bordered and small pearl bordered Boloria, high brown, dark green and
silver washed Argynnis). Their caterpillars are black, and feed on violets
in sunny spots in woodland.
Violets are common, but sunny spots have declined as woodland
management has changed. These butterflies have vanished from nature
reserves as well as economic woods - all due to the lack of ground-level
sunlight.
Well-meaning enemies of
woodland conservation:
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The tidy-minded forester, who removes fallen
timber. As far as possible, leave logs to rot.
The 1987 hurricane flattened thousands of
trees, but the greater damage to the forest
ecosystem was done by heavy machinery
removing the timber.
The NIMBY protester who objects to trees
being felled or cut back. Some tree felling is
sheer vandalism, but much more is useful
management. Think before you complain!
Conservation work
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You may well choose to become
involved in volunteer work in a
woodland reserve somewhere.
Be warned that you are much more
likely to end up chopping things
down than planting!
Typical conservation work involves
coppicing, bramble bashing, and
attempting to exterminate
Rhododendron ponticum. Expect
chainsaws and bonfires!
One example from
many:
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There is an endangered moth known as the
reddish buff, whose only food plant is a spiky
plant of disturbed woodland soil known as
sawwort Serratula tinctoria.
This is now confined to the Isle of Wight, where
its only remaining colony was being overgrown
by brambles.
The solution was to clear the scrub. Rather
than employ people, English Nature tried goats
RIL:
see UKW
v1/5 p.buff moth Acosmetia caliginosa
The
reddish
273, 6/2 p. 106
feeds
on the Sawwort Serratula tinctoria,
growing by woodland rides in the Isle of
Wight.
Goats were brought in to control the scrub. Their udders kept being
lacerated by brambles and blackthorn, leading English
nature to invent a goat udder-guard. The goats also tended to wander
into surrounding woodland, and after one became tangled
in an electric fence the project had to be aborted as employing a
goat-herder was not cost effective.
The Caledonian forest
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There is a totally different ancient
forest in the Scottish Highlands - the
remnants of the Caledonian forest.
This is a pine-birch woodland, which
also goes back to the end of the last
ice age.
As mentioned, it has isolated relict
populations of crossbills, crested tits,
and various boreal plants.
It once covered most of central
Scotland, but now is confined to
pockets around the Cairngorms,
notably Speyside.
Caledonian plants
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Just as ancient oak forests have indicators, so do
ancient pine forests. These include scarce boreal
plants such as twinflower Linnea borealis, the
orchid creeping ladies’ tresses Goodyera repens.
As you might expect, there are also important
lichen communities here.
One Caledonian lichen has become nationally
dominant: the “pollution lichen” Lecanora
conizeiodes was only found in the extreme acidity
of decaying pine logs in the Spey valley, until
Victorian times. The widespread acidification
caused by SO2 led to this species becoming the
commonest lichen in the UK!
Pine problems
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The decline of the Caledonian
forest was initially caused by
logging for timber, fuel etc.
For the last 100 years this has
been overshadowed by a second
man-made problem: deer.
The highlands contain red and roe
deer, which graze on young
saplings, preventing regeneration.
“A mountain fears its deer”.
Wolves!
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Highland Deer
Forest
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There always have been deer.
They didn’t used to destroy the neolithic
forest because their numbers were kept
in check by predators, mainly wolves
(also lynx and perhaps bears).
Large areas of Scotland are called deer
forest – now without a tree in sight!
These used to be forest, but the trees
died of old age without leaving
descendents. You don’t need saws to
destroy a forest.
Fences
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The remaining areas of Caledonian
forest suffer badly from deer. The best
solution is to fence them out - HM is
said to be a keen deer fencer on the
Balmoral estate.
It is sad but frequent that the adjacent
unfenced land is littered with dead
deer after a hard winter, dying by the
fence as they try to get to the protected
grazing.
Here again, hunting is a real
conservation tool. The problem is that
hunters like high densities of deer.
More wolves!
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The solution seems obvious. Reintroduce wolves.
Oddly, this is not very popular.
We have a badly wolf-ist culture,
where it is OK to tell stories about
3 little piggies and the big bad wolf
while bears simply get cross with
Goldilocks. I make a point of
telling my kids that there are no
records of wolf predation on
humans, but hundreds of examples
of bears killing/eating people.
Other re-introductions
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UK populations of several other woodland
mammals have been driven to extinction in the
middle ages, but could be re-introduced.
Wild boar have already come back! They have
escaped from wild boar farms, and established
viable populations in woodlands (especially Kent).
Lynx could be introduced as deer-control in
Scotland. Sheep farmers are not happy.
European beavers could be re-introduced, again to
Scotland. Scoping experiments are being planned.