Encouraging the survival of the forest

Seen against a morning sun in May, the new foliage of oaks glows with luminous ambers and brassy lemon-greens of a vibrancy quite different from the stagy shades of autumn. In Brackloon Wood, below Croagh Patrick in Co Mayo, the colours in the trees' high canopy are picked up nearer the ground, in leaves fanned out by whip-slender saplings. At long last, scattered across the island, we are beginning to have joined-up trees again: old oaks with young ones coming along below.

Brackloon's trees are themselves not especially old - perhaps 180 years, at most. But they all grew naturally, springing up from acorns or sprouting from the stumps of still older, felled oaks. These, in turn, had grown naturally, in continuity from the native forest that greeted Lord Altamont when he came to his Westport estate in 1650.

The modern trees survived a Land Commission underplanting with conifers, now mostly felled and cleared away. The scattered stands of oak, and others mixed from ash and willow, cover almost 20 hectares - about a quarter of the wood - providing living remnants of the natural forest climax of the west.

Along with Coillte's decision to restore the wood as a pure broadleaf forest, using the trees' own genetic stock (a process that could take a century or more), Brackloon has become the focus of close scientific attention. Since 1991, the nutrients it gets from rainfall have been monitored for a Europe-wide programme of forest health. More recently, with funding from the National Council for Forest Research and Development (COFORD), it has been serving as "the flagship site" for an Irish ecological monitoring network based in UCD.

This entails continuing scrutiny of every conceivable aspect of the wood - not just plants, insects, birds, bats and badgers, but soil and vegetation dynamics, along with a study of the wood's pollen history and even its archaeology (there are two ring-forts).

Some measure of the thoroughness is the botanical survey just published by UCD's department of environmental resource management, which lists no fewer than 775 different plants and fungi found in Brackloon. No one should be too surprised by the figure, say the survey team - ancient woodland habitats are supposed to be species-rich. Indeed, they promise, an even closer look should find a good many more.

There's nothing spectacular about Brackloon's plant list, with the exception of one very rare white orchid, the narrow-leaved helleborine. Most of the species are lichens, ferns, mosses, toadstools and slime moulds - plant groups predictably rich in an oakwood kept moist by the nearby Atlantic.

As in so many oceanic woods (and most abundantly at Killarney), the boughs of Brackloon's oaks are virtual hanging gardens of polypody ferns. And many of the lichens and mosses are quite invisible to people walking through the wood - they grow on particular zones of high twigs, boles and branches, and reach the ground only when a gale whips through the trees, snapping off dead twigs and dislodging cushions of moss.

The wood's canopy actually holds the species most sensitive to environmental change. During the survey, led by lichenologist Howard Fox of the National Botanic Gardens, one 17-metre-high oak tree was specially felled so that the entire bark surface could be screened for lichens. There were 51 different kinds, and the resulting map of their zones will help in conservation management. How they are to be monitored every five years, without sacrificing another oak, may call for some ingenuity.

I TRUST the felled tree will now be left where it lies, so that a new survey can examine all the species involved in consuming it - the hundreds of specialised "saproxylic" organisms (burrowing beetles, fungi and so on) - which return to the forest ecosystem all the energy locked up in dead wood. Brackloon's insects and invertebrates are, indeed, the focus of the next big search.

Lichens, liverworts and slime moulds (30 kinds of slime mould, actually) may not be everyone's idea of the "biodiversity" we should care about. A white orchid is so much prettier. But these are the life-forms enriching - and even essential to - a forest ecosystem.

The Brackloon team confess to being outraged by the destruction of living organisms in deciduous woodland habitats in the past few decades, and their report insists, rather touchingly, that the Department of Finance, county councils and other funding bodies should not feel shy about releasing money for basic floristic research in woodland nature reserves and other conservation areas.

The very phrase "ancient woodland", carries a powerful cultural resonance, especially on an island that has so few fragments left. In England, which has a lot more to explore, there has been considerable study of woodland plants that indicate long continuity. Even such common plants (in England) as the wood anemone and dog's mercury are reckoned to mark ancient woodland.

In Ireland, destructive grazing of woods has extinguished much of the flora that might have survived, and only such unpalatable plants as the woodland horsetail and the bluebell may remain as indicators. In the case of our Atlantic woodlands, suites of lichens, mosses and liverworts, disdained by livestock or safely out of their reach, may hold the ultimate clues to a long and shady past.

Along with Brackloon, eight existing native woods across the country are being restored and replanted as People's Millennium Forests. Ecological reports can be read on the project's website, www.millenniumforests.com/ 16forests/surveys/eco.htm

Some are outstandingly thorough and interesting, notably that on Ballygannon Wood in the Vale of Clara, just north of Rathdrum in Co Wicklow, by John Wann, which heads the list. But while birds and animals are allowed their common names, the plant lists are left in Latin. Not everybody who loves bluebells will recognise them as Hyacinthoides nonscriptus - or has a Webb's Irish Flora to help recognition.

Eye On Nature

Why have pigeons a totally different song to other birds? And how do birds hold so much in their mouths and not drop it while picking up more?

Kathleen O'Connor, Blackrock, Co Dublin

Variations between the songs of birds en- able them to recognise each other. The differences arise from the shape of a bird's syrinx. In the pigeon, membranes on the inside wall of the syrinx vibrate to give a cooing sound. In evolution, pigeons with that formation of syrinx may have survived better than those with a different song. The roof of a bird's mouth is hard and has a row of backward-pointing horny papillae running down the middle. The tongue also has backward-pointing papillae, and these allow it to hold food or nest material and gather more.

On May 2nd in the early afternoon, I saw a bat about the size of a sparrow flying low over the pond in Ranelagh Park. He was obviously hunting insects and would dip and skim the surface of the water. Mark Hackett, Roundwood, Co Wicklow

Bats often fly in daylight in spring when they emerge from hibernation and are hungry. Daubenton's bat is the one most often associated with daylight flight.

Eye on Nature is edited by Michael Viney, who welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. E-mail: viney@anu.ie Observations sent by e-mail should include a postal address. Please do not send attachments.