Loch Lomond NNR
When out on the island of Torrinch this week we had a look for one of the island’s largest and oldest trees. It was the beautiful aspen. Aspen is a native tree with a restricted distribution across Scotland but is important as it is the tree that a number of rarer invertebrates live on. On Torrinch there are smaller aspen trees found all along the south-western end but why is this the largest and oldest tree on the island?
Well, the reason is that all of the small trees belong to the same plant. Aspen spreads by suckers i.e. it sends out roots under the ground that produce new saplings metres away from the adults. At Torrinch there are aspen that cover about 400m of the edge of the island. But are all of these the same plant? The suggestion is that in autumn you can tell different aspen plants apart as they will turn a slightly different colour to each other and lose there leaves at different rates. At Torrinch all of the trees we found were at a similar stage in losing their leaves and the leaves were generally a beautiful lemon yellow. So a 400m wide tree is pretty impressive.
Another distinctive feature of aspen (and others in their family – the poplars) are their trembling leaves. The leaves quiver, and move in the slightest of breezes when other trees around are not moving. They do this by having a flexible, long but flattened petiole (leaf stalk). But why? One theory is that there are times when light levels can be too high for tree leaves to photosynthesis. Aspens grows in glades and more open areas so they might be more prone to being in high light levels and so not able to produce food. By having constantly moving leaves it means that less light is captured by the leaves so enabling photosynthesis to continue in bright conditions.
Trees are brilliant.