Updated 5 Nov 2003 |
Planting a new oakwood in Dorset |
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Hot weather causes chaos to the eco-system |
In 2003 Dorset suffered from 8 months of drought (March to October). |
Hot weather causes chaos to the eco-system |
By Dennis Furnell |
Broadleaved trees like oak, beech and ash are shedding their leaves. At this time of year, these trees should be growing new foliage in response to summertime insect damage. They are past masters at this, evolving over millions of years to cope with attack from a host of leaf eaters. Without the oak Britain would enjoy a much less interesting variety of wildlife. Many small birds, particularly members of the titmouse family, such as blue tit and great tit, are almost totally dependent on the productivity of the oak for caterpillars to feed their young. If a late frost should blight the oak leaves when they are in bud, there will be nothing for the caterpillars to feed on, the titmouse eggs will hatch to famine, and the young birds will not survive. Fortunately, the oak is capable of amazing feats of re-growth and later in spring, in time for a second laying of titmouse eggs to compensate for the loss of the first brood, the oaks will throw out new leaves that caterpillars will later be able to feed on. In the past oaks were vital for the economy, not only for wildlife but humankind, too. Oak wood is celebrated for its strength, resilience and ability to resist rot and insect damage – one of the main reasons why it was preferred for the planking and ribs of "ships of the line" and for the merchant fleets that plied the oceans. The timber was also used, indeed still is, to make barrel staves for storing and maturing wine and beer. One of the many virtues of oak timber is tannin – a natural acidic compound developed in the ongoing chemical warfare waged between predator and prey species. In excess tannin is a poison employed by the tree to build a barrier to protect the leaves and bark against fungal and insect attack. Nature has a way of getting round every form of defence, however, and in the case of leaves, predators eat them as they unfurl from the bud before the tree has had time to build up enough tannic acid to protect them. When the caterpillars have gorged, if birds have not picked them off, they will drop off the tree and bury themselves in the soil beneath to pupate. The result of this level of insect attack can be dramatic, stripping the leaves from a whole section of the tree, leaving it looking literally moth eaten. Oaks are long lived though and have a trick or two tucked away among the branches. As August reaches its crescendo, the “Lammas growth” begins to dress the tattered branches with fresh new leaves from hidden buds – just in time to take advantage of the last of the sun’s power before winter sets in. Because of the good weather there’s a lot going on at the moment. The acorns are ripening fast. In a good year an oak can produce nearly a ton of acorns, and this productivity ensures survival. An oak is capable of living for four centuries, and it needs only one of the many acorns to germinate and grow to maturity for the genes to be carried forward. In the past, when there was a particularly large fall of acorns it was known as pannage. Those who owned common pannage rights in a forest or woodland pasture would let their pigs roam free to gorge on the acorns. Apparently pigs are immune to the drastic effect that tannin can have on the human digestion and, grown fat on the acorns, these pigs provided an abundance of pork and bacon. The pigs were useful too in that they buried as many acorns as they consumed, naturally fertilising them in the process, and thus ensuring the continuation of the forest. This year is a variable pannage year. The acorns that survive the predations of grey squirrels in the branches will fall to the ground to be found by wood mice and voles and by the industrious jays – another creature that plays a key role in planting acorns along the woodland margins. Part of the behaviour pattern of this colourful bird is to bury enough acorns in autumn to last through the winter. Research has shown that they are good at remembering where they stored them. As long as they are not shot or taken by a bird of prey they will collect and eat many of the stored acorns during the winter, but it is inevitable that they won’t eat them all and some of those left behind will germinate the following spring. These days the oak woods are no longer needed for firewood, or charcoal and bark (the prime ingredients for tanning leather) and though oak is still a valuable timber crop, many woodlands and forests exist for the sheer delight of walking in them and enjoying the birdsong. Our near neighbours in France have some wonderful woodlands and whether we agree with it or not, many are preserved for hunting and a few support the wild boar (pictured). In Britain wild boar were hunted to extinction 200 years ago, although in one or two forests in Kent and Dorset, escapees have set up small herds and snuffle and root in the leaf litter for acorns re-enacting a positively medieval scene. Wild boar are regarded, and quite rightly so, with some nervousness. They have a well-earned reputation for ferocity when attacked or threatened. But having watched them living out their day-to-day life in a Dorset wood, they reminded me very much of the red-furred Tamworth pigs my father owned when we lived in Devon. The Tamworths and the wild boar seem to fit into a deeply rural woodland landscape. I would not recommend them in public woodlands, but they could really liven up a picnic. 12:39pm Thursday 28th August 2003 |