New research conducted on bog restoration
A new Research Note published by the Forestry Commission should help to take some of the guesswork out of projects to restore afforested peat bogs.
The Note presents the results of recent Forest Research experiments with different methods for restoring peat bogs that have been converted to forest.
Large areas of peat bog were planting with trees during the 20th century in the drive to re-establish a strategic timber reserve in post-war Britain.
However, bogs’ values as open habitats, and as carbon stores that can help tackle climate change, have been increasingly recognised in recent years. These values can be lost if they are converted to forestry, and there has been growing interest in restoring bogs where it is still practicable.
This can involve damming the drains and plough furrows to allow the water table to return to its previous levels, and felling the trees and either removing them or allowing them to be incorporated into the reforming bog (known as "felling to waste"). Research has been continuing to determine the most effective and cost-effective combination of methods and treatments in different circumstances.
The Research Note, written by Russell Anderson from Forest Research, describes the results of two experiments: one on a ’blanket’ bog and the other on a ’lowland raised’ bog, after five years. It provides practical, effective advice for practitioners.
In the blanket bog experiment, the researchers found that treatments that involved both felling trees and damming furrows were more successful than others in terms of raising the water table. Bog vegetation recovered rapidly in the felled treatments, particularly those where the furrows were dammed.
In the lowland raised bog experiment, the water table rose dramatically in all treatments. Only during a prolonged dry summer was there a difference between treatments, the water table falling lower in the whole-tree removal than in the fell-to-waste treatment, with conventional harvesting intermediate. Bog vegetation recovered best when the trees were removed, and least well in the fell-to-waste treatments.
Felling the trees is always necessary for restoring afforested bogs, the researchers found, but removing "lop and top" (the branches and tree tops) is not. Damming plough furrows can also help to restore blanket bog, but is ineffective if the peat is severely cracked, and just damming the main drains can be enough on lowland raised bogs.
The researchers also found that new trees often start to colonise bogs that are undergoing restoration, but removing the "brash mats" after harvesting, and periodic maintenance thereafter, should reduce this problem. (Brash mats are layers of branches and foliage laid on the ground to support forestry machines.)
Russell Anderson said,
"The great benefit of this research is that it has taken some of the guesswork out of bog restoration. In the past it has been largely a matter of getting rid of the trees and blocking the drains, and hoping that would be enough.
"Now, armed with the results of this research project, site managers can make better informed decisions resulting in more efficient operations, leading to cost savings in many cases and better outcomes in the end."
