The news came through recently that one of Wales’ biggest oak trees had blown down, so we went to pay our respects. The Buttington Oak was enormous, measuring 36ft 2inches (11.03m) in girth, and was probably 8-900 years old. Plodding across the sticky alluvial clay of the Severn valley and feeling rather exposed in the unaccustomed flatness, we found the tree in a pasture just back from the riverbank. It was a colossal carcass, lying collapsed and crumpled like a shot elephant. The upturned butt was so big that the dog of a fellow pilgrim was able to walk about inside it. Despite being hollow through to the sky there was still a mass of living branches on its crown that, had it stood, would have been breaking into leaf next month. Sadly it seems that one more gale had been too much for this big-bellied ancient. I am told there has been a steady trickle of mourners to Buttington from around the country over the last couple of months; the craggy seniority and stubborn survival of very old trees seems to be an inspiration to many of us. They have a ‘presence’ that quietly puts human hubris in its place, giving rise instead to respect and even awe.
Not far away from Buttington is Chirk Castle where the National Trust boasts of 650 veteran trees in the parklands that surround the castle, so feeling enthusiastic about old trees we decided to go and pay them a visit. Some of the biggest oaks at Chirk grow along the route of Offa’s Dyke, which bisects the estate. Although not old enough to have seen King Offa build his dyke between Wales and England (AD 750) they do seem to have been planted or retained as marker trees along its route. One of the most remarkable of these at Chirk is the ‘Great Oak at the Gates of the Dead’, a split and crippled veteran with a blackened and hollow heart which stands guard at the site of the Battle of Crogen. Here in 1165 a Welsh army defeated the English (which always goes down well around here) and many of the dead are said to be buried in the adjacent field. This Methuselah, although only a teenager at the time, saw it all – and a lot more since.
My favourite tree at Chirk was a 500-year-old sweet chestnut, which apparently is five trees fused together into one squat mass. Crouched behind the parkland wall it has hunkered down for generations, all contorted rot and shedding skin it seemed the epitome of extreme old age, yet youthful shoots were still growing from its ancient bulk. Perhaps it is good for a few more centuries yet.
Appart from being remarkable organisms in their own right, veteran trees are important ecologically. They are often, in effect, complete ecosystems, with many invertebrates and lower plants completing some, or even all, of their lifecycle within a single tree. Remarkably 1700 species of invertebrates found in Britain depend at least in part on decaying wood, making this an important yet often overlooked habitat. These saproxylic creatures (fauna of decaying wood) are principally beetles and flies, which live and feed on the deep rot, accumulated debris and associated fungi (not to mention each other) found in old and damaged trees.The long process of wood decay, which can range from bone dry to waterlogged, provides a succession of conditions suitable for different species of rot loving invertebrates.Many of these are rare relicts of the fauna found in the primeval forest that once covered Britain. The bark of mature trees growing in the open can also develop a rich assemblage of lichens over time; the available light and warmth suits them as does the increasingly alkaline bark of oak trees as they age. In the original Wildwood it is likely that a spectrum of young to old trees would always have been available fairly close by, including those that were old and decaying. Once they had grown beyond the sapling stage there wasn’t much, other than lightening strikes or the collapse of an adjacent tree, to threaten them so many would have progressed from stout middle age through to decaying elders.
Historically humans have always cropped trees for timber. In times past no sensible person would have left a tree to go rotten but rather cut it down in its prime, to be used for building anything from houses to warships; what was left over went for firewood. Consequently, old and decaying trees have become uncommon in our woodlands, which has all but eliminated an element of their original fauna. Concentrations of old trees in Britain are now usually found only in ancient open commons or the parks around great houses, where they were retained beyond their years for ornamental reasons. Even there they were usually cleared up when they fell apart or died. Ecologically old trees go on being useful even when dead as standing or fallen trunks and limbs are still inhabited by lichens and rot dwelling insects. So it was good to see that at Chirk the National Trust were not clearing away the debris but often leaving it piled up around a splintered trunk.
Another problem facing the inhabitants of ancient trees is the ‘age gap’. It is only in the last 25 years or so that we have begun to realise that there are almost no middle-aged trees within beetle flight of the veterans. The National Trust have now planted many new trees in the parkland at Chirk, but whether these will have developed enough rot to support the specialist insects before the veterans finally disintegrate and compost down, must be touch and go. Oaks and beech need to be 200 years old before the conditions that support these insects start to be formed. In these more conservation conscious times some woodland trees are being allowed to grow elderly, so perhaps the ‘old forest’ faunas in these parkland refuges will in time be able to migrate back to their original habitat – if they can survive the ‘age gap’.