A wealth of old oakland

In Brackloon Wood the birches are in leaf, a fresh green mist stealing through the clearings to heal their raw disorder. "When I see birches bend to left and right/Across the lines of straighter, darker trees," wrote Robert Frost, "I like to think some boy's been swinging them." At Brackloon, however, the leaning birches are a sign of a serious, grown-up game: one meant to swing the whole wood round - back to its own nature, and away from all those lines of "straighter, darker trees".

Brackloon covers 74 hectares of undulating hillside above Clew Bay, a few kilometres to the east of Croagh Patrick. The distant peak frames up in the oaks that tower above the birches, boughs braced in muscular curves against the wind. They will not break into leaf before May, so one notices the green of polypody ferns and leafy lichens living on the rough bark, gathered there slowly over the better part of two centuries.

This does not make the trees particularly ancient: even the oldest ones, at around 180 years, will still be producing worthwhile crops of acorns for another half-century or more. What is exciting ecologically is that they all grew naturally, springing up from seedlings or as shoots sprouting from the stumps of still older, felled oaks - and these, in turn, had grown naturally.

In fact, there seem to have been self-generating oaks at Brackloon since before Lord Altamont came to his estate in 1650 and found it a continuous forest. The greatest pressure on the trees until modern times was the production of charcoal for local iron furnaces: the remains of a charcoal pit have been discovered in the wood.

Brackloon was bought from Lord Sligo in the 1940s by the Forestry Division and underplanted with conifers 20 years later, the stands of "wild" oaks remaining as islands among the infant battalions of spruce. Enough of the old broadleaf fabric remained to retain the wood's shape and atmosphere, and alder, rowan, willow, birch. Plant life continued to flourish in the shelter of rocky outcrops, in the grassy rides, and around the marshy pool at the heart of the wood.

From the 1970s onwards, Brackloon began to register with a succession of government wildlife scientists. They were fascinated with wood's stubborn richness of species, suggesting great age. One of them found the narrow-leaved helleborine, Cephalanthera longifolia, a rare, white orchid of wet places in old woods. First, it was just the oaks that seemed worth saving: then, the whole of Brackloon.

Twelve years ago it was proposed as a woodland nature reserve, a process that still grinds along. The wood's conservation status has been going up and up, through the whole gamut of acronyms - ASI, NHA, SAC; even (we will come to this later) FERG. Brackloon now has international importance as one of our last few fragments of semi-natural Atlantic oakwood, with a unique Irish community of plants - in botanical language, Blechno- Quercetum petraea sub-association scapanietosum. But the aim is now more than mere protection - rather, to restore the wood in all its native diversity, and to use it as a living laboratory for monitoring environmental change.

The fresh impetus has come from FERG, the Forest Ecosystem Research Group headed by Prof Ted Farrell in UCD. It was one of the group - a soil scientist, Dr Declan Little - who, coming upon Brackloon in some magical autumn evening light in 1990, developed "a close bond" with the wood. He used it for his own studies of oakwoods on acid soils and began to press the case for restoration.

Coillte, to its credit, has responded by taking out most of the underplanted conifers - hence the drunken birch and ash saplings left between the stumps - and by deciding to manage Brackloon for conservation. Its head man in Westport, Co Mayo, Paudy Blighe, a great fan of oaks, reckons that to restore the wood to a full mature canopy from its own genetic resources might take two or three centuries.

There are 19 hectares of pure sessile oak, and any one of the trees can produce about 50,000 acorns in a good mast year. Unfortunately, these exceptional years can come a decade apart. Last November, a group from Conservation Volunteers Ireland searched in vain for acorns and ended up transplanting seedlings from previous years which had germinated under dense shade.

Some of the wood can be left to regenerate on its own, but the clearfelled areas will be replanted with oaks and other broadleaves from Brackloon's own gene-pool. Once the last conifer has gone, not even a sycamore or alien beech will be allowed to intrude on its relict Irish community of trees and shrubs, herbs and grasses. Once a forgotten remnant of ancient forest, Brackloon is becoming a key resource for ecological research. Since 1991, FERG has been monitoring the nutrients it gets from rain, part of an EU-wide network of forest health observation. Now, with the help of money from the National Council for Forest Research and Development (COFORD), the wood is serving as "the flagship site" for an Irish Ecological Monitoring Network.

This extends the monitoring to every conceivable aspect - not just the plants, insects, birds, bats and badgers but the soil and vegetation dynamics, radionuclide cycling, pollen history, even the archaeology (there are two ring-forts).

But Brackloon is not all for science. As the moss creeps over the conifer stumps and covers up the sawdust, the wood is reclaiming its old wildness and mystery. This is what brings the CVI volunteers to annual summer work-camps, to tackle the invasive rhododendron and help restore the fences. It is what intrigues the local schoolchildren, brought in for "education days" - or, crowding beneath the old oaks, to think of Robin Hood.

Not everyone, unfortunately, appreciates the fences and the new gate with its stile. On the day I came by, some vandal had sawn down the gate to put his sheep illegally in the wood, thus warranting, to put it mildly, an arrow up his arse.