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In the woods at Knockbarron one of the finest and most intact esker systems to be found anywhere in Ireland is preserved. This tells the fascinating story of how these landforms came to be at the very end of the last Ice Age.
This is also an area of old woodland with much of ecological interest at whatever time of year you visit. It is different at every season. Perhaps the best time for a first visit would be early May, when so much of the woodland floor is a blue haze of bluebells.
In mid-summer the woods settle into a few months of dark contemplation, except for the marsh, which is now drier and from which the newts that visit in spring to breed have mostly departed, but where that retiring and magic little fern-relative the adder’s-tongue, is beginning to show its tongues.
If you are interested in fungi, autumn is a great time to walk through Knockbarron: and if your main interest is geological heritage the best time is winter, when the eskers are less obscured by vegetation. At this time there is nowhere the informed imagination can more easily conjure up the boom of melting glaciers or the thunder of their meltwaters …
In other words, this is a place to visit time and again, at different times, in different ways. Each time the experience will be different.
Our walk starts at the entrance to the wood where the car park is. On your way along the road you will pass another entrance to the wood. A feature of special interest here is the colony of solitary bees that inhabit the roadside bank at the edge of the wood. You might think these little bees are all working together the way honeybees do, but in fact each little bee is working for herself (yes, they are all female). She makes a tunnel which she lines with special chemicals to keep it watertight, and at the end constructs brood cells in each of which she lays a single egg and provisions it with a sufficient supply of nectar and pollen. Then she seals the cell and starts another. The baby bee spends its childhood in this little brood chamber before pupating for the winter, and then makes its way out the following spring to continue the cycle.
From here continue down the road and enter the wood at the south-east corner and follow the trail markers up onto the esker ridge to the first stop. (As you make your way down the road you will see some fine spindle bushes on your right hand side: they will be much more obvious in autumn when they have their unmistakable cardinal’s-hat fruits.
Nowhere will you find a more spectacular example of a classical esker. Notice how narrow and steep sided it is: almost artificial you might think. Indeed, long ago eskers were thought to be man-made. At one time this esker system extended away over the fields across the road to the south-west (and at the other end of the wood into the fields to the north-east) but these extensions have mostly disappeared, quarried long ago for their content of coarse gravel and stone. Here in the wood the esker system is almost completely undisturbed.
In geological terms, eskers are sinuous, generally steep–sided ridges or concatenations of ice–contact stratified drift, often hummocky in form and pitted with kettle–holes. More simply, they are ancient river sediments – but not the sediments of ordinary rivers. Sand and gravel are the main constituents of eskers, although boulders are common in the gravels (including large and conspicuous erratics at times) and discontinuous and generally thin layers of silt also occur.These sands and gravels were laid down in rivers of meltwater that thundered at the base of the glaciers that covered much of Ireland at the very end of the last great Ice Age. The sand and gravel which they contain were the rock material which the glacier had picked up as it ground its slow way across the land, and were washed out as the ice melted. As these glacial streams were banked by walls of ice, their beds of sand and gravel were left as upstanding ridges when the ice melted. They formed at the very end of the glacial period, when extensive melting was taking place.
The word esker (eiscir) is an Irish word – one of the very few terms bequeathed to the science of geology by the Irish language. Esker ridges can be as long as 500 km, and they vary considerably in height and breadth. They are exceptionally well developed in Fennoscandia, Maine and across the Canadian Shield, but the eskers of the Irish Midlands are among the finest examples of Pleistocene eskers in Northern Europe, and are one of the most distinctive and unique features of the landscape of Central Ireland.
You will notice the markings on some of the beech trees. These are frame crop trees (i.e. final crop trees). They will be favoured through crown thinning, leaving openings large enough to encourage natural regeneration. The frame crop trees today are mainly beech, but over time the beech will be replaced by native oak, ash, birch, hazel, holly etc.
There are two small areas of marsh at this end of the woods. The flora and fauna of these areas is especially diverse, and include several species of special conservation interest. Both marshes occupy hollows in the esker network, but the upper one was drained in the 19th century and is drier than it once was. A host of wetland plant species occurs here, including several species of sedges, marsh bedstraw, marsh willowherb, wild iris, skullcap, marsh pennywort and dozens of others. Perhaps the most interesting plant, though one of the least conspicuous, is the unprepossessing fern-relative adder’s-tongue, which occurs in an abundance equaled in few other places in the county. The marshes are an important breeding place for smooth newts. There is a wonderfully diverse invertebrate fauna, at its most conspicuous at the end of summer.
So undisturbed is the esker system that you seldom have an opportunity to see what it is made of inside! But there are a number of places where the forest tracks cut into the esker and let you see what they are made of. Here where the track (the one that leads into the wood from where you saw the bees) cuts through it you can see the chaotic jumble of boulders, cobbles, gravel and coarse sand, all mixed up together, dumped by the turbulent meltwater in the ice tunnel in which the esker formed.
This indicates that they were deposited by running water that was flowing at a very high rate. Try to visualise the power of such a high flow regime by imagining how much fast flowing water is needed to transport boulders of the size you see here. Some disturbed (‘faulted’) beds indicate that the sediment pile slumped when the active ice surrounding it disappeared due to melting, after the gravels were deposited.
The summit of Knockbarron dominates the landscape of moraine and esker north of Kinnitty, separated from the Slieve Bloom foothills by the valley of the Camcor river. At the foot of Knockbarron, on a gravel ridge high above the marshy fringes of the river, are the medievel remains of St Bairrfhionn’s church of the holly ridge - drom chuilinn (Drumcullen). The site of this monastery was chosen with careful deliberation. It is very likely that the hill was already a place of veneration; a cluster of named wells surrounds it, and two others overprinted with the names of saints Martin and John; St John's Well, just below the summit, is the most important. It was visited on the St John's eve (23 June); you wait by the well until midnight, when the water would boil, and for the first hour after the water was at its most efficacious. Nearby is St John's rock, a large limestone erratic in the crevices of which even today pilgrims place coins and small pieces of white quartz, which must be brought up from the river. One of the townlands at the foot of the hill is Kilrubbrid (wood of springs), and the land to the west of the hill is still known as Springfield. It is very likely that the pre-Christian festival of midsummer was celebrated on the hill; the feast of St John the Baptist is the Christian 'cover version' of the festival of the solstice. The deliberate naming of the hill for St Bairrfhionn (Cnoc Bairrfhionn) suggests that the earlier name may have referred to its pagan significance.
The monastery at Knockbarron was supposedly founded by Colmcille in the 6th century, and subsequently handed over to the care of Bairrfhionn, who was a relation and disciple of the great saint. From Drumcullen Bairrfhionn later moved to Kilbarron near Ballyshannon in Donegal, and is even credited in legend with being the first European to set foot in America. He died around 590 and his feast is 21 May.
The construction in the early 13th century of a Norman motte and bailey beside the church on a spur of moraine above the river Camcor attests to the political and strategic significance of the site in medieval times, a time no doubt when much of the earlier sacred 'presence' of the place was still coherent and felt. In the 18th-19th centuries, when it belonged to the Drought estate, the hill was an area of open landscape abundantly planted with trees, in which the wells and rocks had a respected place. Today's hill is well-farmed land inherited from this estate landscape. Most of the trees are gone, and the wells and stones have been all but lost sight of: they have – though perhaps not irrecoverably – lost their place in the heart of the community, and so in the landscape itself.
A renewal of interest in recent years has seen an attempt to clean up the church and graveyard, and access along the lane leading to the site has been improved. This reawakening sense of the spiritual value in the landscape has not yet penetrated to the older layer beneath the Christian. St John's Well is dry and overgrown, and the other wells have fallen into disuse.
Knockbarron has a diverse and interesting flora and fauna, which is perhaps best appreciated in spring, before the tree canopy closes over and limits the amount of light reaching the woodland floor. The most striking aspect of the flora is the profusion of bluebells that carpets large areas of the wood in spring. This reflects Knockbarron’s status as an ancient wood, because although it has always been a managed wood, sections of it at least appear never to have been anything but woodland.
You can see bluebells along most of the walk when they are in flower (mainly April to June). There are here all the time of course, but their flowering season is these few weeks at the beginning of summer before the canopy of leaves overhead closes and blocks off most of the light from the woodland floor.
At this point you can see one of the ancient enclosure banks that are found in several areas of the wood; this aspect of its history is one of the things we hope will be studied more carefully in the years ahead. These may have been woodbanks, ancient enclosures constructed hundreds of years ago to keep animals from straying into managed forest. There is also the possibility that they pre-date the forest itself.
Knockbarron Forest (or the Glen Wood as it is often known locally) came under state forest management around the 1940s. At that time a variety of trees were planted: Grand Fir, Scots Pine, Norway Spruce, Sitka Spruce and Beech. Coillte has shown that it is possible to manage forest and land resources commercially while providing social and environmental benefits. This practice has been recognized by Coillte obtaining the Forest Stewardship Council (FSC) certification. It means that our forests are managed in accordance with strict environmental, social and economic criteria.Being under state ownership also means that the esker complex is safeguarded against exploitation.
Part of the certification process was to identify 15% of the estate to be managed for biodiversity. Knockbarron Wood is one such area, the main features of importance being the intact esker complex, the marsh areas, and the mixed forest. The aim is to maintain the seasonally flooded area in its present good condition; and to create a mainly broad-leaved forest of good structure and a rich calcareous ground flora by gradually increasing the native broad-leaved element, especially ash, during the normal conifer felling programme.
Some clear-felling took place in the late 1980s and 1990s. As an approximate guide the current breakdown of tree cover is beech 25%, Norway spruce 23%, Scots pine 20%, Douglas fir 15%. Other conifers and broadleaves 7%, open area 10% (the forest extends over an area of some 85ha). The policy for areas which have been clearfelled is to replace them with native broadleaves . Further clearfelling will take place in different areas of the wood in 2006, 2009, 2014 and 2017. The beechwoods have already been thinned in 2002 and will be thinned again in 2007. Some areas of scots pine and beech will be allowed to develop to maturity.
You have now crossed onto a different – and equally spectacular – esker that runs more or less in the same direction as the one you started on. As you walk along this stretch keep an eye out for the thick rope-like stems of wild clematis that climb into the canopy of the trees. Wild clematis (or old man’s beard as it is sometimes called) is the only true liana in the Irish flora. Lianas are woody climbing vines, more typical of rain forests than temperate woodland. You won’t see much of the plant here though because it’s away up in the canopy where most of the light is, but if you keep an eye out you will see it in lots of other places in Knockbarron.
Family RANUNCULACEAE (buttercup family)
Wild clematis or old man’s beard
As August approaches and the first signs of autumn appear, the unobtrusive and generally scarcely-noticed flowers of wild clematis begin to open in hedges and high up in the tree canopy in those lime-rich areas of the county where it grows. Clematis is a liana: indeed, the only true liana in the Irish flora, with woody climbing stems that can be as thick as a man’s arm: strong enough to support any jungle-swinging Tarzan. The plant climbs by means of its leaf-stalks, which curl themselves round every branch they encounter, becoming as hard as wire after they have done so.
There is something quite Magnolia-like about the flowers. They have dispensed with petals, their function being taken by four tough, creamy-white and downy sepals, which fall soon after the flower opens. There is a feathery brush of around 50 stamens, and at the centre of the flower a cluster of greenish carpels tightly bunched together, each with a little crochet needle of a stigma. Each carpel has a coating of long, fine hairs, but this is not apparent at this stage since they are kept flat against the style and because of the way they are all bundled together. The flower is protandrous (i.e. the stamens first). In spite of their fragrance, the flowers produce no nectar, but the abundant pollen is sufficient incentive for insects (flies prominent among them) to visit.
After fertilisation the stamens soon fall away and a globular cluster of nutlets develops on the receptacle, each with a long, elegant plumed tail formed by a now greatly elongated style. The expanded plume has the pure whiteness of snow crystals, but the style remains green for a long time. The decorative streamers of plumed fruit-clusters often remain on the parent plant well into winter.
Lengths of the stem used to be smoked by gypsies, an application which is reflected in vernacular names given to the plant in several European countries: ‘smookout’ in the Netherlands, ‘bois à fumer’ in France, ‘Raunchholz’ in Germany, ‘gypsy’s bacca’ in Britain. One of its old English names, white vine, is a translation of the specific epithet in its scientific name, vitalba. The generic name comes from the Greek word klema, which means tendril or vine-twig. Wild clematis has vesicant juice (i.e. it causes blisters); it was used by beggars at one time (as were buttercups) to produce sores that would excite the pity of potential almsgivers.
In a number of areas in the woods you can find remnants of the oak that was more widespread in the Glen Wood when it was part of the estate of the Drought family (who lived at Droughtville, just beside Knockbarron). These are young trees: but if you look carefully you will see that many have developed from shoots that sprouted when a much older ‘parent’ was felled.
The management policy for Knockbarron will favour these trees, as well as all the others that establish themselves naturally, since it is on these in particular that the broader policy of enhancing overall biodiversity depends. Oak is one of the most important tree species for biodiversity support. It is capable of providing food and shelter for nearly 300 species of invertebrates (and all the invertebrates that feed on them in their turn), as well as habitat for the dozens of plants that live in their shade, and countless fungi.
The ridge is up to 20m high at some points. You may have noticed the way the esker rises and swells at intervals. Often it branches at these ‘beads,’ and there is often a change in the level at which the esker stands. These beads are thought to represent the end of a season’s deposition. The direction of branching gives us a clue as to the direction in which the torrential rivers in their ice-walled tunnels were flowing. Can you work out what this was for yourself?
This is another good place to see what the inside of the esker looks like (we saw it earlier at Stop 3). Look for the oak trees along the next stretch of the ridge.
The network of forest tracks further diversifies the plant and animal life of the wood, because different species occur along these more permanently well-lit areas.
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Type: Eco Walk-Loop
Trailhead: Start Finish Knockbarron Wood 1K from Kinnitty Co Offaly
Services: Kinnitty Co Offaly
Time : 1.2-2 Hours
Difficulty: Moderate to easy. Suitable for families.
Minimum Gear : Sturdy Walking Boots, Rain Wear, Fluids, Mobile Phone.