Presentation on theme: "UK ancient woodlands Peter Shaw. Introduction An initial reaction to hearing the word ‘conservation’ is ‘save the rainforests’. Yes, splendid – but we."— Presentation transcript:
Introduction 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: 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: 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: 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 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: 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 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 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)
Identifying ancient woodland 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.
Ancient woodland indicators 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.
Wood anemone or windflower, Anemone nemorosa. One of the most reliable AWIs. 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.
Lily of the valley Convallaria majalis– a good AWI but beware garden transplants! Herb Paris Paris quadrifolia.
Less obvious species: 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 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 most valuable trees are those standing but decaying inside.
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! Ampedus cardinalis - a very rare beetle of brown-rotted oak heartwood The Rhinoceros beetle Sinodendron cylindricum
Traditional management: 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: 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 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: 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
The reddish buff moth Acosmetia caliginosa 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. RIL: see UKW v1/5 p. 273, 6/2 p. 106 RIL: see UKW v1/5 p. 273, 6/2 p. 106
The Caledonian forest 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 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 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! 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. Highland Deer Forest
Fences 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! The solution seems obvious. Re- introduce 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 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.