Spottiswoode birch cutting project providing real boost for rare moth
In our project at Spottiswoode to restore a former Sitka Spruce plantation to native woodland, natural regeneration of Birch has proved very useful and some areas have now gone back to natural woodland without any assistance.
In 15 years the growth of these trees has been astonishing and those areas are starting to look like proper woodland with some trees 10 metres or more tall. This means that tree planting efforts could focus on those areas where no natural regeneration was happening.
In one area, spruce trees had never grown well and heather had taken over, so the Forestry Commission allowed us to keep this as a small patch of heather moor. This turned out to be a great idea as it has created an open clearing in the woodland.
In the hills, muirburn is used to keep heather short to benefit both sheep and grouse. It also makes walking across the hills less strenuous! However, without muirburn, heather becomes tall and leggy, and under this canopy the shade and humidity create a special miniature habitat where some locally rare plants, fungi and insects get shelter and thrive.
Last year we did moth trapping regularly throughout the summer months and found moths such as the Northern Eggar living on our heather patch. Another unexpected find was the tiny Lesser Twayblade Orchid growing under a big clump of leggy heather.
Eventually, unmanaged heather moorland will start the long process of natural succession into woodland.
The tree best adapted to colonise is Birch which has tiny winged seeds that can blow long distances. This is exactly what has been happening to our heather area - birch trees have been gradually encroaching, so over the last few years we have had to remove some trees to favour the heather.
Our very helpful friends in Edinburgh known as the Lothian Conservation Volunteers visit each winter to help with tasks such as tree planting. On their last visit, removing birch trees from the heather was the task so we cut down about 200 trees in one day, using hand saws, keeping the trunks for firewood, and leaving the branches to decay naturally.
Another unexpected arrival has been a very rare insect, the Large Red-belted Clearwing Moth, previously unknown in southern Scotland.
In the spring the adults lay their eggs only on recently-cut birch stumps where the caterpillars burrow down and a year later emerge as adults.
So our efforts in clearing the birch trees we hope will give this insect a real boost this year.