We have a cold and often harsh climate, and that makes establishing trees quite difficult. A Scots pine that would normally reach maturity in 60 years in the south of England may take twice as long in the Highlands. To combat that, we do everything we can to improve conditions and to make sure that saplings have the best chance of survival.
The first and most important consideration when planting a tree is to make sure that it is planted in a suitable location, as different species require different conditions. Scots pine and birch prefer free-draining, drier sites, whereas willows and alders can tolerate wetter locations. Rowan and birch are suitable for higher ground, whereas oak and hazel need more fertile and sheltered conditions. We take this into account with our planting, so for example at Dundreggan we’ve planted oak and ash on the mineral-rich slopes of the low-elevation riparian zone by the River Moriston, at mid-elevations we’re planting Scots pine, birch, rowan and juniper, and at the treeline we’re planting dwarf birch.
Trees will more readily establish in bare soil, where the vegetation has been removed. One technique that we use to achieve this is known as screefing, which involves using a spade to remove the vegetation at ground level, before digging a hole for the tree. This is time consuming and hard work for an individual planter, so in commercial tree planting operations a mechanised technique known as mounding is normally employed. Machines dig a hole, turn the turf they have extracted upside down and lay it next to the hole. This has a wide range of benefits for the tree, but it leaves the land riddled with holes.
As we are aiming to restore the forest through creating as little disturbance as possible, we are pioneering a new technique at Dundreggan, known as inverted turf mounding.
This is basically the same technique as standard mounding, except that the turf is put back into the hole upside down, and compacted so there is no air space underneath it. This takes much longer and is more expensive, but it gives all the benefits of mounding whilst creating a natural-looking landscape for the young forest, rather than a highly modified site.
We fertilise all the trees that we plant at higher altitudes and on nutrient-poor sites. Nutrients have been lost from most of the Highlands, through deforestation and burning of the land, and by the ongoing sale of sheep and deer for meat – the nutrients in their bodies are permanently lost from the ecosystem. Adding rock phosphate helps the saplings to take root, and to grow faster and more healthily than those which are not fertilised.
Most of our trees are planted in fenced exclosures, to keep out deer. However in some sites, e.g. where we carry out enrichment planting of existing woodlands, or where we plant aspens, they are not always fenced, so it’s necessary to protect young saplings with tree guards. Trees that are browsed at an early age can still survive, but they will take much longer to establish, so protecting them at this vulnerable stage is very important.
Tree planting is at the heart of our work to restore the Caledonian Forest. Every year our dedicated volunteers plant thousands of native trees as part of our vision to restore this beautiful and diverse ecosystem to a spectacular wilderness region of the Scottish Highlands. To ensure that our planted forest resembles a natural one as closely as possible, we avoid straight lines and even spacing of our trees, and we don’t plant only one species in an area. Rather, we plant a variety of species and space them irregularly, with some in clumps and others further apart, to mimic nature as fully as possible.
In 2012 we reached a huge milestone – the planting of our Millionth Tree. Our new target, which we are now one year into, is to establish a Million More Trees in the next five years, through a combination of tree planting and natural regeneration. The techniques that we have developed mean that we are doing this in an environmentally sensitive fashion, whilst giving the trees that we plant the best chance of survival, so that they can grow to form a healthy and mature restored Caledonian Forest.
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