Woodland Flowers

The woodland flora lies at the heart of a complex web of relationships. Many of these benefit the plant, as for example when insects pollinate flowers, birds distribute berries, or mycorrhizal fungi make mineral nutrients more available. However, there seems to be no obvious advantage to the plants when their leaves are eaten by deer and cows, or by tiny caterpillars that mine their way through the tissues of a leaf. Some plants have defences against grazing in the form of prickles and stinging hairs on their stems (roses, nettles), deposits of silica on and in their leaves (grasses and sedges), or poisonous chemicals, stored in cells (Bracken). These are only partly successful, and the investment in defence structures takes up resources that the plant might have used to produce more seeds. Defence efforts may be reduced when there is less of a threat: for example, the upper leaves of Holly, out of reach of large herbivores, lack prickles; conversely, brambles may respond to increased browsing by becoming thornier (Bazely et al. 1991).

Some plants, such as Bracken, are eaten by only a few species of insects, others by a lot; even in Tolkien’s Mordor, the hobbits, Sam and Frodo, found that the brambles had ‘maggot-ridden buds’. Invertebrate attacks may be specific to individual species or groups of species, and to individual organs on those plants. The Strawberry Tortrix moth feeds and form webs on the leaves of Water Avens, which are mined by sawfly larvae (Metallus lanceolatus), while small midges (Contarina geicola) form galls on the buds of flowers or leaves. Only rarely do the invertebrate impacts cause significant conservation concern for woodland ground flora plants. Usually this is where they feed on seeds and reduce the reproductive potential of rare plants. The annual appearance of the Lady’s-slipper orchid has, on occasion, been cut short by a slug. More is also probably happening below ground; experiments in old fields have shown that the composition of the plant community does change when the soil is treated with insecticide.

However, the most obvious effects on woodland plants are the above-ground attacks by mammals. The larger herbivores, from rabbits and hares upward, alter the vegetation patterns in woods dramatically, and both the impacts, and the herbivores themselves, may once have been bigger.

Several hundred thousand years ago, giant elephants roamed Great Britain, pushing over trees and crashing through scrub, while spreading nutrients and seeds about the landscape in their dung. During the last Ice Age, large numbers of Mammoth and Woolly Rhinoceros lived in a steppe-like vegetation south of the major ice-sheets (Yalden 1999). Sadly, this mega-fauna has disappeared from the world, partly through the efforts of our ancestors (Stuart 2005). In Siberia there is, however, an inspirational project to see if the impact of Mammoth and Woolly Rhinoceros can be mimicked by Bison, Musk Ox and cattle, to switch the current tundra and low-productivity forest vegetation back to open, productive grassland (Zimov 2005).

In Great Britain, the remains of mega-beasts have been found, but they have left no direct legacy in our current vegetation. Less mega, but still large, herbivores such as Bison and Wild Horse roamed the Continent in the immediate post-glacial period but did not survive in Great Britain for long. There were though Wild Ox, Elk, Red Deer and Roe Deer (Yalden 1999). Wild Boar were present, and although these are omnivores, their impact on woodland vegetation is considered here, alongside those of wild cattle and deer.

Wild animals, such as deer, were hunted for food by early humans, but with the introduction of farming, they might also be killed because they competed with domesticated animals for grazing and fed on crops planted for human consumption. From the Neolithic period onward, medium to large wild herbivores declined over most of the country until the last century. The Wild Ox was probably extinct in Great Britain by about 3,500 years ago. Deer survived where they were given special protection, perhaps in prehistoric times by taboos on hunting them; then in the medieval period through the provisions of Forest Law, which was concerned primarily with protecting resources such as deer for the Crown; and later in the parks and stalking grounds of wealthy landowners. Elsewhere they were largely hunted out as the Wild Ox had been before.

Meanwhile, the numbers and biomass of domestic livestock increased to dwarf those of all wild mammals put together (Yalden 1999). New plant-eating species have been added, accidentally or deliberately, to the countryside, notably grey squirrels, rabbits, Fallow Deer, Muntjac and Sika.

A Neolithic farming village of about 3 0 people might have needed a clearing of about 13 hectares for their crops, but 250 hectares of surrounding land for the grazing/rootling of their cattle, sheep and pigs (Gregg 1988). The composition of early Neolithic pig bones indicates that they were foraging in woodland more then, than later during the Iron Age (Hamilton et al. 2009).

Long-term grazing and rootling gradually open up woodland by slowing down regeneration. This effect might spread out from pre-existing glades, increasing the light reaching the ground and favouring the development of more grass-rich vegetation, with more potential food for stock. The animals would tend to prefer glades where there was more food available, and where there was better protection from predators such as wolves. In this situation, more young livestock would be born, the herds and flocks could increase and there would be further opening-up of the landscape. Grazing animals could use lands where arable production might be marginal or where there was more land than the community could, or needed to, cultivate for crops. The animals produced valuable products such as meat, milk, wool and hides, and were probably (as in similar societies today) a measure of wealth and status in themselves.

The practice of combining grazing livestock and wood production in generally rather open woodland is now known as wood-pasture (Hartel & Pleininger 2014). Iconic forest landscapes in Great Britain, such as the New Forest, Sherwood Forest and the major native pinewoods, are a product of wood-pasture management. Often, these sites are on relatively infertile soils, because the more fertile ground was generally favoured for crops, including hay. Stock grazed on the wood-pastures might be kept elsewhere at night, or over the winter, and slaughtered in a different place for food. Nutrients in their dung and bodies would gradually be transferred out of the forest. Over centuries this could lead to further reductions in soil fertility, as indicated by remnants of richer soils preserved under prehistoric burial mounds. The ground flora structure and composition changed, to favour generally low-growing or unpalatable plants and those that can tolerate low-nutrient soils.

Across Europe, wood-pasture is now in decline (Hartel & Pleininger 2014). Farming systems have changed and extensive grazing, perhaps guided by a herdsman, has often been abandoned. Increasingly, areas are either used just for grazing and arable, or for wood production. Large areas of traditional wood-pastures survive in central and eastern Europe, but even these systems are under threat. Forestry regulations may make it illegal to graze livestock in woodland. The wave of agricultural and forest management improvements that swept through western Europe in the post-war period is catching up with these landscapes, to the detriment of their conservation interests, as we have found in Great Britain. Here wood-pastures were grubbed up or ploughed in areas where the land went down the farming route after the Second World War. Where the foresters took control, the open spaces were planted with trees or filled up with natural regeneration (Kirby et al. 1995).

The conservation priorities in most wood-pastures today tend to be associated with the veteran trees and the species that live on or in them – the lichens that encrust their trunks and the deadwood beetles and flies that inhabit the rot in the middle of the trees (Harding & Rose 1986, Rose 1993). In between the trees, there may be rough grassland or heath as in the New Forest, but often the land has been improved (in agricultural terms) through ploughing or reseeding.

Epping Forest on the edge of London illustrates some of these trends. The Forest was the subject of a major conservation campaign to stop it being cleared in the late 19th century, meaning it still survives as a mixture of open and closed habitats. However, it is now more closed than it was because pollarding of the branches of the old trees for charcoal at a height above the reach of cattle largely stopped in the late 19th century. The branches have got bigger since and carry more foliage. The Forest was still regularly grazed by cattle when I was young, but by the mid-1970s none of the remaining commoners were willing to put stock on to the Forest. Glades filled with young trees. Thorns and Oak spread out on to the grassy plains. Some open semi-natural grass/grass-heath and wetland areas disappeared. Uncommon species such as Lousewort Pedicularis palustris declined even where the glades stayed open, because the grass growth became too tall and dense for it. More recently, the Corporation of London has restored grazing to parts of the Forest to reverse these trends (Dennis 2014).

Superficially, the flora of many wood-pastures can look rather uniform – a mixture of rough grasses, such as Sweet Vernal-grass, Common Bent, Creeping Soft-grass, or Wavy Hair-grass. Herbaceous species, such as Sheep’s Sorrel and Tormentil, may be mixed in, but very bitten back. Species richness is encouraged, even under high grazing pressure, if there are variations in the landscape, because of irregular topography or soil conditions. A diversity of structure in the tree and shrub layer also helps. Woodland plants that are sensitive to grazing may survive and flower, for example, at the edge of thorn bushes.

The range of woodland plant species in working wood-pastures such as the New Forest can be as high as in neighbouring coppices (Chatters & Sanderson 1994). However, the New Forest is a special case: its size, and variety of soil nutrient and drainage conditions, are unparalleled in the south of England. Its location means that southern Continental species such as the Wild Gladiolus can establish a toehold in Great Britain. The relatively high average humidity permits Atlantic species such as the Hay-scented Fern to occur further east than might be expected from the general pattern of their distribution.

In both the New Forest and Epping Forest, one of the winners from reduced grazing has been Holly. Birds disperse its seeds in their droppings and young hollies often turn up at the base of old Oaks. Holly seedlings can establish and grow under deep shade, although they remain vulnerable to grazing until they have reached a couple of metres or more. They may then form dense thickets that are virtually impenetrable. This can be seen at Hainault Forest in Essex, at Sutton Park, on the edge of Birmingham, and at Ebernoe Common in Sussex.

Staverton Park in Suffolk indicates what holly-invaded sites can become. In the southern part of the site, The Thicks, there are ancient hollies that share the canopy with the great Oaks. Some gaps allow light down to ground level, but the vegetation cover is very sparse compared to the northern half where Holly is largely absent. Holly was probably always present in the Park and may have been cut for winter browse for the deer. The exceptional growth in The Thicks seems to have arisen from a spell of regeneration in the early 19th century when this area was not as heavily grazed as in the north (Peterken 1969).

As the tree cover in Great Britain declined from the Neolithic period onward, those trees that were left became more valuable as a source of wood. Where tree cover was limited, it was often more efficient and effective to separate the grazing from the wood-growing places. Many of the latter came to be managed as coppices (Buckley & Mills 2015a, 2015b). Coppice woods and other forms of closed canopy woodland accumulated plant species tolerant of shade and/or relatively intolerant of grazing (Rackham 2003).

Animals were sometimes let into the later stages of coppice, as at Hatfield Forest in Essex (Rackham 1989), although there is little fodder under the shade of a well-stocked, mature coppice. In addition, if the animals damaged the coppice stems by eating the bark this reduced the value of the coppice to a degree that might outweigh any benefits from the grazing. At Hatfield Forest there are reports from 1612 that the underwood was patchy because of the grazing pressure. Grazing could also take place in open areas such as rides and glades. Up until the 1970s a couple used to still let two cows graze in Whitecross Green Wood in Oxfordshire and the couple also made hay from the grass on the rides.

The incentive to keep livestock out of the woods became less as the value of the coppice products declined. Sheep came to be a regular feature of the western oakwoods for example, the animals benefiting from the shelter of the trees in bad weather, as well as whatever grazing was available. As a result, whereas in wood-pastures we have seen changes to the flora because animals have been removed from sites previously grazed, in other woods the changes occur where heavy grazing has been introduced to woods that had long been largely ungrazed. Both processes can be studied using fenced exclosures.

In the New Forest, in 1963, 11 hectares were fenced and split into an ungrazed exclosure and a plot grazed by deer. The vegetation was recorded in 1969, 1978 and 1985 (Putman et al. 1989). Initially the amount of above-ground vegetation in the fenced area increased, compared to the adjacent grazed plot. Trees and shrubs grew up from ‘seedlings’ that had established some time before but had been grazed back whenever they got above the height of the grass. As trees became denser, some ground flora species were shaded out in the ungrazed paddock and the overall cover and species richness declined. Palatable species such as Heather and Gorse, which had initially grown well in the ungrazed plot, died out as the shade increased. By 1985 there were similar numbers of species in both plots but less ground flora cover in the ungrazed than in the grazed plot. Ivy, Bramble and Honeysuckle were still noticeably more abundant in the ungrazed plot, whereas Bent and Tufted Hair-grass were still common in the grazed area. Unfortunately, fences are difficult and costly to maintain, the experiment has now been abandoned, and deer now roam through both paddocks.

In an alderwood at Coedydd Aber in North Wales, a shift from open grassy vegetation to more woodland species was seen after 20 years of excluding sheep from a five-hectare block (Latham & Blackstock 1998). Honeysuckle, Bramble and Ivy increased in cover, along with Broad Buckler-fern, Wild Angelica and Smooth-stalked Sedge. The nearby site of Coed Gorswen, a mixed Oak–Ash wood, was mostly fenced to keep out sheep and cattle in 1960 (Linhart & Whelan 1980). By 2009, as at other sites, Bramble, Honeysuckle, Ivy and Bilberry were doing better in the ungrazed sections, which were shadier because of more tree and shrub regeneration. Many ground flora species recorded in 1964 were less frequent, particularly light-demanding species. In the long term, species richness might decline, as in the New Forest study, or this decline might be reversed if natural disturbances start to open up the canopy, for example through windthrow of trees or through Ash Dieback.

Many fenced plots have been set up in western oakwoods because of concerns about the lack of Oak regeneration, for example in the RSPB’s Nagshead reserve in the Forest of Dean and at Wistman’s Wood, high up on Dartmoor. A detailed record is available for an Oak stand at Yarncliff Wood, south-west of Sheffield, which was partly fenced off in 1955 by the National Trust. At that time, the ground flora was close-grazed Wavy Hair-grass, with sparse Bilberry, some Cowberry on the tops of rocks and small fronds of Bracken. After the fence was put up, the Wavy Hair-grass grew taller and there was recovery of the Bilberry shoots. By 1981 the Bilberry had overgrown much of the Cowberry and an unusual hybrid between the two species had disappeared. Bramble, Hairy Wood-rush and Climbing Corydalis Ceratocapnos claviculata increased and the regeneration of Oak, Birch and Rowan was able to get away (Pigott 1983). By 2018 sheep had been fenced out of most of the rest of the wood. Regeneration of Oak and Rowan is now widespread throughout, with tall Bilberry and patches of Bramble, Great Wood-rush and Broad Buckler-fern. The original exclosure area can be found from the remnants of the original fencing and there was still a clear difference with the small area of grazed woodland to the north and open moor to the west and south, with the tall Bilberry more or less stopping at the fenceline.

At Roudsea Wood in Cumbria an oakwood exclosure established in 1 976 shows more luxuriant Honeysuckle, Bilberry and Wavy Hair-grass, while a second exclosure on limestone has abundant Bramble contrasting with the False Brome of the surrounding areas. Another limestone example comes from Rassal Ashwood (Wester Ross), which has large open-grown Ash that probably started their lives about 200 years ago. These trees grow mainly on rock outcrops and stone piles, perhaps because the better soils in between were cultivated in the past. In the wooded meadows of Estonia, the trees and shrubs similarly occupy the stonier patches and the grass between is mown for hay.

In 1975 two hectares of the open Ash–Hazel wood at Rassal were fenced to exclude sheep and deer. By 1985, within the fence, regeneration of Hazel, Rowan, Goat Willow and some Ash had reduced the cover of grasses, although some clearings remained. Tall herbs such as Meadowsweet and Hogweed flourished, and, under the Hazel, shade-tolerant herbs such as Upland Enchanter’s-nightshade, Bluebell, Wild Strawberry, Herb-Robert, Wall Lettuce and Primrose were common (Peterken 1986). Alison Averis noted that the exclosure was ‘a magnificent spectacle’ with tall flowering Lady’s-mantle, Melancholy Thistle, Water Avens and bluebells amongst a rich matrix of grasses. By 2001 this rich flora had declined. The fenced areas were a dense Hazel thicket over a few grasses with scattered plants of Meadowsweet and Water Avens dotted here and there. Ivy formed tight mats over the rocks through a blanket of moss (Averis 2002). The whole wood had been fenced in 1990, so even outside the original exclosure the formerly-short turf vegetation grew taller and small species such as the elegant Fairy Flax Linum catharticum were shaded out.

By 2018, cattle grazing had been reinstated in the main reserve block, to judge from a faded notice warning of cows, calves and a bull! The young Ash and Rowan were being browsed. The vegetation was probably still too rank for Fairy Flax, but there was a good mix of the grasses and tall herbs recorded previously. Around the base of the big Ash were woodland species such as primroses, Upland Enchanter’s-nightshade, Herb-Robert and Wood Willowherb. The original exclosure was still stockproof, although there were signs of deer within it. The canopy was of the tall Hazel and Ash that regenerated shortly after the fence was put up in the 1970s. The woodland flora included much Bluebell, Wood-sorrel, Primrose, Barren Strawberry as well as grasses and ferns. Bracken was less abundant than in the open grazed sections.

The species that flourished in the early years after fencing, as at Rassal Ashwood, and in the birchwoods of Creagh Meaghaid National Nature Reserve in the central Highlands following a reduction in deer numbers, can also be found in places that sheep and deer cannot easily reach, such as small islands and steep stream-sides. Derek Ratcliffe (1977) listed 12 species characteristic of the tall herb community found on cliff ledges in the Highlands. One, Tufted Hair-grass, is a regular feature of rough pasture, but the other 11 show signs of sensitivity to grazing (Melancholy Thistle, Marsh Hawk’s-beard, Meadowsweet, Water Avens, Angelica, Great Wood-rush, Red Campion, Common Valerian, Wood Crane’s-bill, Stone Bramble and Globeflower). The ledges do appear to be acting as grazing refugia.

Fencing large herbivores out of the woods clearly benefits some species, at least initially, but there may then be declines in species richness and cover where the trees and shrubs increase their shade, or one of the more competitive ground flora species becomes dominant. Trying to reduce the numbers of animals using a wood might be a better solution for the flora overall than simply fencing them out.

Red Deer have long been an issue in Scottish woodland management because they have been encouraged for stalking since Victorian times. Much of the year the deer feed on the open hill, but in the winter, they move to lower ground, where many of the remnant broadleaved and native pinewoods occur. Because of this, many woods are relatively open, with little regeneration, little shrub layer, few of the palatable trees such as Aspen or Sallow, and a generally bitten-back ground flora.

By contrast, during the 19th and early 20th centuries in England and Wales deer were quite scarce. Roe Deer disappeared from large areas; Red Deer survived in south-west England because of hunting interests, and for their ornamental appearance in parks such as at Windsor. Fallow Deer were mainly confined to parks, although a distinctive dark-coloured herd roamed Epping Forest.

Since the Second World War, deer numbers have built up through most of Great Britain (Ward 2005). Hunting has declined, and, thanks to the mechanisation of farming, there are now far fewer people out in the fields, day in, day out, to disturb the animals. Milder winters, and the availability of more food, in the form of green crops in the fields over the winter, have reduced the number that die in bad weather. Roe Deer have recolonised most of England, while Red Deer have shown local spread plus deliberate reintroduction to some areas. The Fallow Deer expansion is partly linked to park escapes during and following the Second World War. Two other species, Sika and Chinese Water Deer, were introduced in the late 19th and early 20th centuries and have built up significant populations in a few areas. A third new arrival, the Muntjac, has spread rapidly across much of England. For a long while, deer were scarce in Wales, but numbers are now rising across the Principality.

Great Wood-rush – interesting in small quantities

Despite its robust appearance, Great Wood-rush Luzula sylvatica is grazing-sensitive and in many upland woods it is largely confined to rock ledges. In ungrazed situations, Great Wood-rush may spread to the virtual exclusion of other species, as in parts of Wistmans Wood on Dartmoor and in the Great Wood of Cawdor near Nairn, perhaps the finest oakwood in north-east Scotland. Its competitiveness means that it can be grown en masse in gardens to suppress weeds.

Great Wood-rush is widespread in Europe, and through northern and western Great Britain. It is also quite common in south-east England, south of the Thames. It grows up to 80cm, with clumps of glossy, bright green leaves. It tends to be common on damp acid soils, for example along streamsides. A study in Belgium suggested that it prefers cool soil temperatures and high humidity (Godefroid et al. 2006). This may explain its scarcity in central and eastern England, particularly when many of the ancient woods were being managed for coppice, and why in the Highlands it can grow well outside woods.

There are reports that the leaves, which remain greenish for most of the winter, are picked by Golden Eagles to line their eyries, but I have never been close enough to an eyrie to check!

Great Wood-rush flowers.

Great Wood-rush dominance at Cawdor Wood, near Nairn.

Wytham illustrates the trend: a few fallow deer were kept in the park prior to the Second World War and subsequently colonised the Woods. In 1959 there were thought to be about six adult deer in the whole 400ha. In the hard winter of 1962–3 a herd of 13 were tracked in the snow as they crossed the frozen Thames and back. Fallow were joined in 1967 by another species, as Charles Elton noted in his diary. ‘There is excitement at the arrival… of 4 muntjac deer’. By the mid-1970s obvious impacts on the vegetation had begun to appear; the numbers of Fallow were estimated to be up to 60 in 1979, plus a few Muntjac (probably quite a lot!). By 1987, the numbers were considered unacceptably high – 200 or so Fallow and perhaps 300 Muntjac – but numbers continued to rise until the mid-1990s. Roe Deer recolonised the Woods.

Foresters were well aware of the damage that deer did to young trees, but for a long while they were not seen as a conservation problem. Tansley (1939) says of Fallow Deer that ‘it is commonly kept in parks, often escapes and temporarily establishes itself in the more extensive woods till it becomes a nuisance and is exterminated’. Peterken (1993) considered deer in relation to wood-pasture management and woodland structure, but references to effects on the ground flora were few. Rodwell (1991) gives more detail on how grazing affects the ground flora, but deer impacts were not noted as particularly significant.

Rackham signalled a warning in his 1975 account of Hayley Wood, where he outlined the effect of deer on the growth and flowering of oxlips. Then, from about 1985, more and more examples were reported of direct deer impacts on the ground flora and of indirect effects on other species through deer changing the woodland structure, affecting nutrient cycling or promoting the growth of more grazing-tolerant species. The first signs of deer damage to the flora tended to be on palatable species, for example bitten-off stems of Bramble or Bilberry (Kirby 2001). Grazing of leaves and stems of Bluebell and Dog’s Mercury reduces the resources that they can put into growth and flowering, leading to smaller plants. Flowers may be directly grazed off, leaving just the lower stem, for example, of a Lords-and-Ladies spike. Trampling by the deer creates bare paths, and in Brigsteer Park in the Lake District, Wild Daffodil bulbs were damaged by the hoof-scraping of Roe Deer (Barkham 1980).

Grasses, rushes and sedges commonly increase in grazed woods. Grasses grow from the base of the leaf rather than the tip, which means that they can recover better after being grazed. Many grasses also contain high levels of silica, which discourages animals from eating too much of them. However, even some woodland grasses are sensitive to damage and so are more common in ungrazed or only lightly-grazed situations. Wood Fescue, for example, is mainly found in sheltered gorges and on rock ledges in western Great Britain, rarely spreading out across the slopes.

Plants that benefit from having grazers around include weedy species such as Nipplewort Lapsana communis, Docks and Oxtongue Picris hieracioides that can take advantage of the disturbed ground. Similarly, if a tall competitor species is eaten more than a smaller plant, then the old adage that ‘my enemy’s enemy is my friend’ applies. In Wytham Woods, tall plants such as Wild Angelica, Hogweed and Bramble became less abundant as the deer increased, but low-growing species such as Germander Speedwell and Wavy Bitter-cress increased. There was little change in overall species richness in the ground flora, but quite a change in the appearance of the Woods. Between 1974 and 1999 Bramble went from covering nearly a third of the woodland floor to just 5% cover; from thickets commonly over a metre high, to most plants measuring less than 30cm. As deer numbers have been reduced, so the Bramble cover has started to come back at Wytham. The grasses that had spread under heavy grazing are no longer so common. The recovering Bramble thickets provide good cover, feeding and nesting sites for many small birds and mammals. Not everyone, though, is happy with the Bramble resurgence; there are fewer earthworms for the badgers to feed on under Bramble, and the thickets are little easier for them to push through than they are for those researching the badgers!

If deer are changing the vegetation in undesirable ways, then their numbers need to be reduced. However, estimating deer densities is notoriously difficult. Structured night-time surveys, using heat-sensitive night vision, have become the preferred method although the equipment is expensive: the animals are easy to see against the cooler vegetation.

False Brome – a winner under high deer regimes

False Brome is a grass typical of basic to neutral soils, widespread across Europe and in Great Britain, except in parts of the Highlands. It occurs predominantly in woodland, although flowering is reduced in deep shade. In full sunlight it can suffer from photobleaching, which may restrict its ability to spread outside woods. Greater water loss may also be an issue in the open. There are two forms, a hairy-edged and a non-hairy-edged type. The hairy form loses less water when growing in the open compared to the non-hairy form but does not survive as well under shade (Davies & Long 1991).

In the National Vegetation Classification False Brome helped to distinguish the rather open, dry ashwoods of the Peak District and other northern limestones, from the less free-draining, but still nutrient-rich ashwoods further south and east. In the latter, the grass was generally not very abundant if present at all (Rodwell 1991). Since the 1980s, False Brome, along with Tufted Hair-grass and Pendulous Sedge, has increased with the rise in deer pressure in these southern woods. At Wytham it went from being present in 64 of the 163 vegetation plots in 1974, to present in 146 of them by 2011. The main reason for its spread may be the indirect benefit of the deer reducing the Bramble cover. Deer may also help spread the seeds, which catch easily on to their fur. Its cover is now declining again as the Bramble recovers.

Dense stands of False Brome can be quite species-poor, both here in Great Britain and in North America where it was introduced and, like several other European woodland species, has become invasive.

False Brome flowers.

Other techniques that have been tried include walking systematically through a wood and counting the deer seen; counting the piles of deer dung found in a given area; and looking for indirect signs such as deer tracks or lying-up places. A method developed by Arnold Cooke from his studies at Monks Wood National Nature Reserve in Cambridgeshire (Cooke 2006) involved sticking groups of short Ivy sprigs into the ground one metre apart. These sprigs were inspected after 24 hours, three days and seven days, to assess the number of stems partly eaten and the number defoliated completely. The length of time taken for the sprigs to be grazed gave a measure of the likely impact on the woodland.

Knowing how many deer there are, or what impact they are having, gives an indication of what sorts of effort might be needed to manage their population, but there are no easy solutions. Fencing deer out of woods or blocks of woodland is difficult and costly. If fences are not maintained regularly then the deer quickly get back in. Effective population control through the use of contraceptives has not so far proved possible. Shooting deer to control their numbers can be effective but takes a lot of effort to bring the population down and becomes increasingly difficult as the deer density declines. The hunters must spend more and more time in the field for each deer killed. Deer management has to be done across a landscape or the animals simply find refuge in the areas where no control is taking place, and there may be public objections to shooting deer.

In hindsight, it would have been better on many sites, such as in Wytham Woods, if we had started to tackle deer numbers before they had caused large-scale changes to the vegetation. We have, perhaps, the chance to apply this lesson across the country with reintroduced Wild Boar.

Boar were probably wiped out in the wild in Great Britain by the end of the 13th century though they may have survived later in parks. Various attempts were made to reintroduce them for hunting through to the 17th century, and they stayed in our memories in place-names such as Wildboarclough, heraldry (the badge of Richard III), and the odd folksong. During the 1980s increasing numbers were kept in farms for their meat, sometimes crossed with domestic pigs. Inevitably some escaped. Most were recaptured or shot, but in 1998 a government report concluded that there were populations of free-ranging Wild Boar living in Kent, East Sussex and Dorset (Wilson 2003). Later, a population established in the Forest of Dean and this has grown rapidly. Forestry England have a cull programme, although, even with the cull, the population is spreading out from the Forest. Wild boar or feral pigs (whichever you prefer) are back and seem likely to be here to stay.

The diet of Wild Boar includes acorns, seeds, roots, rhizomes, carrion, insects and live plants. These last are less important than for deer, but a wide range of species may be eaten. In Bia∤owieza Forest in Poland, boar eat Nettle, Marsh-marigold, Herb-Robert, Yellow Archangel, Touch-me-not Balsam, Dandelion, Dock, Rushes, sedges and grasses (Falinski 1986). They rootle around, disturbing the soil surface, in their search for bulbs, roots, insects, according to the season, and create wallows. Quite large areas of ground may be churned up in this way, both under the trees and in open areas in the woods and adjacent fields. The long-term effects of this are unknown, but in the Polish studies, much of the damaged vegetation was not eaten and the plants might recover. The disturbance aerated the soil and speeded up release of nutrients to the benefit of Nettle, Raspberry and Lesser Celandine. Similar activity can be seen in and around the Forest of Dean.

A study in south-east England looked more closely at boar impact on bluebells. In early spring Wild Boar did eat the bulbs, which led to less cover and density of bluebells, and fewer flowers (Sims et al. 2014). If given some protection, the Bluebell stands recovered quickly, and even without protection there were more seeds germinating in the disturbed ground. Provided the Boar do not come back to the same patch every year, Boar and Bluebell might thus be able to thrive in the same wood. Their soil disturbance looks unsightly, but it does break through the mats of grass and bracken rhizomes that form in some woods. Wild Boar have even been trialled as a possible way of stimulating woodland regeneration in Scotland by creating gaps in heather moorland (Sandom et al. 2013). The disturbed soil may create opportunities for smaller plant species to establish, some of which may come from seed carried to the site on the boar’s fur.

The Wild Boar story raises some interesting conservation issues: the releases were illegal, but the species was formerly native. The animals showed evidence of cross-breeding with domestic pigs, but were close enough to the wild type to justify them being considered a reintroduction. Now that they are re-established, do we accept their impact on the ground flora (and other aspects of the woodland system), even if they are damaging features that we currently value, such as Bluebell carpets? Do we try to maintain some woods in a boar-free state?

We have much less experience in Great Britain of dealing with Boar compared to deer and have had only limited success with deer management! In practice, any conservation case for Wild Boar management is likely to come second to concerns about them cross-breeding with outdoor pig herds, spreading swine diseases, causing public safety issues, or damaging people’s gardens. The potential for vegetation recovery in disturbed woodland areas is heartening but little consolation to a farmer whose improved grass has become more thistly where the Boar have been, or for the children whose school playing field has been ripped up.

It is hard now to imagine the densities of rabbits that existed in the 1940s and the impact that they had, not just on semi-natural vegetation, but on crops as well. Post-war tree plantings generally had to be rabbit-fenced as a matter of course; small stems of shrubs and trees were at risk from ring-barking. Coppice regrowth could be stunted, delaying canopy closure and allowing Bramble to grow up into dense thickets, as E.J. Salisbury described in his Hertfordshire Oak–Hornbeam woods. The disturbed, and nutrient-enriched, ground around warrens favoured unpalatable species such as Elder, Ground-ivy and Nettle. Old warrens in the woods may still be marked by patches of these species.

Then, in the 1950s, myxomatosis arrived, a disease that caused such catastrophic rabbit deaths that they ceased to be a significant ecological factor over much of the country for many years. There had been hundreds of rabbits killed each year on the Wytham Estate, but when Mick Southern went out in the snow in 1955 he found not a single track. The rabbit decline was followed by a burst of tree regeneration as seedlings and saplings, previously held in check, were finally able to get away in the decade or so before deer numbers built up. Rabbit numbers have recovered somewhat but they still have nothing like the influence that they once had.

Smaller mammals such as mice and voles are generally more influenced by the vegetation structure, rather than vice versa. High populations of small mammals developed in many of the first-generation afforestation sites in the uplands as the grasses, Bilberry and Heather grew luxuriant after the stands were fenced and sheep excluded. The boom was relatively short-lived because once the trees had closed canopy, tall grasses and herbs were largely confined to the rides and occasional gaps where the planted trees had not grown well.

In the New Forest exclosure study, Wood Mouse, Bank Vole and Common Shrew were all regularly recorded in the taller, denser, vegetation of the ungrazed plot, but only the Wood Mouse was found, and at lower densities, in the grazed plot (Putman et al. 1989). In Wytham Woods, Bank Vole numbers declined during the period when the deer took out the Bramble and other low cover. Where the Bramble remained vigorous in small deer-fenced exclosures the voles had approximately five times the density inside as outside the fence. The wood mice did not show such sharp differences. Bank voles rely heavily on vegetation cover to protect them from predators; wood mice are more agile and may depend less on cover and more on early detection of their predators to allow them to escape (Buesching et al. 2010).

Large herbivores are part of natural woodland systems. Deer have a positive role in spreading seeds through a wood and from one wood to another. Red and Roe Deer are undisputed native species; Fallow have been with us for about 1,000 years, so might be classed as honorary natives. The pigs in the Forest of Dean may not be pure Wild Boar but they are genetically not very different from Wild Boar in France. Even cattle in woods could be considered as analogues for the lost Wild Ox. Should we regard the return of these animals to our woods, after centuries of absence in some cases, as a conservation success?

At the same time there is no doubt that large herbivores cause major changes in the abundance of other valued species, not just amongst the plants. The loss of low vegetation cover in woodland, as a result of grazing, has contributed to reductions in woodland breeding birds and in Dormouse populations. Locally, changes have occurred in woodland butterflies and moths because of effects on host plants and nectar sources (Fuller & Gill 2001). Colin Tubbs, the Nature Conservancy Council’s representative in the New Forest, noted that the 19th-century Inclosures, which were ungrazed when first established, had once been renowned amongst butterfly and moth collectors. However, their interest declined from about the 1950s onward, partly because livestock were allowed into them (Tubbs 1986).

Many of the species assemblages and features we value have developed as part of cultural landscapes where the numbers of animals in woodland were controlled, but those control systems (whether through fences, herding or hunting) have broken down. If we had big enough areas, with fluctuations in numbers of animals and their impacts over time, then perhaps analogous assemblages and features could be maintained with unregulated numbers of grazing animals. Was this what the landscape looked like when wild herbivores predominated, in the time before farming?