Today was good day for a forest wander with a purpose. I have recently been working on a conversion table to match the estimated age of a tree to its girth or circumference so armed with a tape measure we set out. Being still somewhat chilly meant that there was hardly any further show from the Celendines and Anenomes just starting to appear last week, but no matter. What we were after were trees, and our destination was one of the oldest parts of the forest, the Kerselaarsplein in the Joseph Zwaenepoel reserve. A Kerselaar is a Cherry Tree, none of which are to be seen here although many decades ago there was an attempt to diversify the forest trees and some of them, notably Thuja and related species can still be found. The Cherry trees are no longer. Joseph Zwaenepoel (Joe swan pond is a delightful name and should feature in literature) is a retired forestry engineer who, in 1983, initiated the establishment of a forest reserve that now bears his name. These areas are characterized by exceptionally old trees and rich biodiversity, evolving naturally without human intervention.
But first to Woodpeckers. We have three species around here, the Great Spotted, the Lesser Spotted and the Green. I'm sure you have heard them, drumming away on dead trees, signalling their prescence and territories. But is it possible to identify which woodpecker by the drumming pattern?
This is a Great Spotted Woodpecker and it is the one you are most likely to hear. It has a short, fast drum which tails off just at the end. The Lesser Spotted has a slightly longer drum with no tailing off. The Green drums rarely and Gorman (2004) says that when they do it is not very convincing and rather weak. You'd be better off listening for its call if you can't see it.
So to trees. I've made a handy tree girth vs age checker which is, naturally, somewhat approximate. Yes, I'm a Maths teacher and these type of things appeal to me. Local conditions are important with trees in the open growing quicker than those in the forest and Oaks grow more slowly than Beech. The oldest oak is named after Léon De Bruyn (1838 - 1908), a former Minister of Agriculture who unlike others in his position seems to have had an unblemished tenure.
When meauring tree girths you should do it 4ft from the ground. Yes, I'm old, that's more or less chest height for me. The De Bruyn Oak has a current girth of 4m 60cm (I'm bilingual, een echte Anglo-Belge) and was the biggest we saw. Using Desmos I have an equation which suggests that multiplying the girth in cms by 0.833 will give an approximate age. So the De Bruyne Oak, which I believe to be the oldest tree, is about 400 years old. Why are there no older ones? I have an answer to this question but that's something for another day.
Here's a picture from today's walk. I love this little tunnel under the Drève de Lorraine with its tiny cascade. Hope to see you on a walk sometime soon.
