Scots pine is the most-widely distributed conifer in the world, with a natural range that stretches from western Scotland to the Okhotsk Sea in eastern Siberia, and from north of the Arctic Circle in Scandinavia to southern
Spain. The Scots pines of Stabbursdalen National Park in Norway form the northernmost pine forest in the
world, at a latitude of 70° 10' N., with some of the trees dated to 500 years old.
Despite the species' huge range, the native pinewoods of the Caledonian Forest are unique because of the
absence of any other conifers - elsewhere, Scots pine grows with other trees such as Norway spruce and Siberian
The Scottish pinewoods are also distinctive because of the oceanic nature of our climate, which gives rise to an abundance of mosses and lichens, especially in the more westerly woodlands, such as those at Beinn Eighe and
The oldest Scots pine known in Scotland is in Glen Loyne in Inverness-shire and was estimated to be about 550 years old in the late 1990s by scientists from the Forestry Commission's Forest Research agency. It was one of a group of ancient pines whose average age was put at about 440 years. That tree began its life when beavers and wolves still flourished in Scotland, and it was already 50 years old when Columbus sailed to the Americas in 1492.
However, there could be older pines still alive and growing, and waiting to be discovered somewhere in the Highlands, as dating work has only been carried out on a few selected stands in our pinewood remnants. Older trees are known from Scandinavia - a Scots pine in Sweden's Muddus National Park has been dated at 711 years, and one in Norway's Forfjorddalen Nature Reserve was 718 years old in 2001. Both of those trees are growing much further north than any pines in Scotland today.
While many conifers have a fairly uniform shape, Scots pine comes in an amazing variety of forms and sizes. Younger trees tend to have the classic conical form, but as the tree matures it can take a completely unique shape. This can range from fairly tall and narrow, with few side branches, to open and spreading with multiple trunks. Eleven main growth-types have been identified in the Caledonian Forest, although the variety is really infinite.
Genes influences a pine's shape and size, as they do ours, although there are also many environmental influences. If a deer nibbles the seedling, removing the lead
shoot, the tree is likely to develop interesting forms
as it grows to maturity. Trees growing close together will tend to be straighter and more uniform, while those
with some space around them usually develop more open, spreading crowns.
Those growing in relatively sheltered areas and on suitable soil can reach impressive sizes. The largest ones in Scotland can reach an impressive 20 metres (65 feet) or more in height and up to 3.6 metres (12 feet) in girth!
By contrast, pines on boggy ground, or on high, exposed sites are often gnarled, stunted and bonsai-like, even
after many decades.
If we could travel back around 6,000 years in time, we would see that pine woodland spread across a huge area - some 1,500,000 hectares of the Highlands of Scotland. The Caledonian Forest was a fantastic mosaic of pine and other woodland, glade and bog. Around 4,500 years ago pine began to decline. It is thought that this was partly
due to a shift towards a wetter, colder climate, but the arrival of early farmers soon afterwards certainly had a devastating effect on the forest.
Millennia of exploitation, including overgrazing by livestock, and clearance for agriculture and building materials, have reduced Scotland's pine forests to around 1% of their former range. Key species of pinewood wildlife, such as wolf, lynx and beaver have also been lost.
The remaining fragments are small and disconnected, and still suffer from overgrazing and ecological imbalance.
But Trees for Life and other organisations are working to expand and reconnect what's left. Using a
range of methods to protect the forest from overgrazing, as well as planting native trees and removing invasive, exotic species, the Caledonian Forest is returning once again.
See also: Human impacts on the Caledonian Forest, Deforestation.
Scots pine bark is a very characteristic part of the tree. In its earlier years (and higher up in mature trees) it has a wonderful orangey-red hue that looks fantastic in low sunlight. The younger bark also has paper-thin layers that peel quite easily.
As the tree matures, the bark becomes deeply ridged and fissured. It builds
up in thick, jigsaw-like layered plates, up to 5cm thick. This adds a whole new dimension to the forest, providing niches for mosses and lichens, as well as spiders and insects. These in turn attract birds such as crested tits and treecreepers, which probe the crevices for prey.
This thick bark has evolved partly as a protection against fire, which once played a key role in the life cycle of pine in parts of Scotland. Remarkably, in the east of its Scottish range, pine tends to have thicker bark - an adaptation to the more frequent fires that swept through the drier, eastern forests.
See also: Ecological features of the Caledonian Forest, Tree Bark.
It takes two years for pine cones to mature, after pollination
The sex life of Scots pine is perhaps topical with the approach of Valentine's Day! The male and female flowers appear on the same tree in May. The female flowers are found on the higher, more exposed branches, and the males tend to be clustered en masse on the branches below. The tree relies on wind to carry the male pollen to fertilise the female flowers of other pine trees.
Once the female flower is fertilised, it takes two years for it to develop into a mature cone, which ripens in April.
At any given time it is possible to see two sets of cones on a tree: the younger ones, which have been fertilised within the last year, and the ripe, or near ripe cones which will soon release their seeds.
In warm, dry weather, the cones open up, releasing the light seeds into the air. In a good year, a tree may
produce more than 3,000 cones, each with up to 25 seeds inside.
There is a saying: 'from acorns mighty oak trees grow', as a metaphor for how majestic achievements may have incredibly small beginnings. But to consider the transformation a pine goes through is even more impressive. A
tiny seed weighing around 0.005 grams contains the potential to become a majestic old granny pine many million
of times heavier.
Scots pine has 'mast years' - years when it produces a huge glut of seed, satisfying and overwhelming hungry
mouths and guaranteeing that some seeds escape the seed predators and become seedlings. In a mast year a
pine can produce 3,000 cones, which will release tens of thousands of seeds.
The seed has a tiny 'wing' attached to it, allowing it to be carried an average of 100 metres by the wind, although
it can be carried much further if blown across icy ground. Pine is quite particular about where it grows, and
prefers to have plenty of light, well-drained mineral soil.
See also: Ecological features of the Caledonian Forest, Seed Dispersal.
When a Scots pine dies, its role in the forest is far from over. Pine contains lots of resins - chemicals that slow down fungal and insect attack. Because of this, a pine can remain standing for 100 years after it has died!
In this time it still supports a huge amount of wildlife including specialist dead wood insects, lichens and fungi, as well as birds such as crested tits that rely on dead pines in which to excavate a nest site. Woodpeckers, owls, bats and pine martens are among the many other forms of life that can thrive in the habitat provided by a dead pine.
All of this takes place before it has even fallen over, at which point it supports yet more life for the years it takes for its nutrients to be returned to the soil, ready to feed the next generation of trees.
Pinewoods are mobile and don't have fixed boundaries. If we had an aerial view of a pinewood over many centuries, we would see that the woodland would shift, with young trees seeding into open areas. The mature trees would eventually die, leaving space for younger trees to replace them. Scots pine doesn't like to grow in its own shade, preferring to be some distance from its parent. This helps to reduce competition for light and nutrients.
In the past there were many influences on the movement and regeneration of the forest. Fire played an important role in clearing thick vegetation, and exposing an ideal seed bed, free from competition. Storms blew over mature trees (as they still do), opening up the canopy. Scots pine would also have benefited from the rooting behaviour of wild boar, and the hooves of wild cattle. This disturbance would have resulted in the exposure of the mineral soil that pine seeds germinate best in.
Pines are wonderful trees in their own right, but they can also support a fantastic range of insect life. More obvious wildlife such as crossbills and squirrels get a lot of well-deserved attention, but insects are often overlooked, and are every bit as fascinating. Scots pine supports many different weird and wonderful insects, each of which has an intriguing lifestyle, and its own unique role in the forest ecosystem.
Larvae of the pine weevil burrow into the wood of the tree, and other insects live on the pine's foliage - aphids suck the sap, and caterpillars of species such as the sawfly and pine looper moth eat the needles. Wood ants feed on these caterpillars, thereby helping to protect the trees from defoliation. These insects, and hundreds more inhabit the hidden world of the Scots pine.
Fungi are the unsung heroes of the forest, playing a crucial role in helping nutrients flow through the ecosystem. Most trees, including Scots pine, have what are known as mycorrhizal relationships with certain kinds of fungi.
In these intriguing, mutually beneficial interactions, the thread-like filaments of the fungus wrap around or penetrate the roots of the tree. The fungus absorbs the sugars produced by the tree - food it can't produce on its own. In return, the fungus passes on nutrients from the soils that the tree wouldn't otherwise be able to absorb. The fungus can also help the tree absorb water, and protect it against disease.
Scots pine is known to have mycorrhizal associations with over 200 species of fungi in Scotland, including the chanterelle, and the extremely rare greenfoot tooth fungus. Some species of fungus rely solely on their interaction with pine for their survival.
Scots pine is the backbone of the Caledonian Forest ecosystem, and some other trees depend on it, literally, for their survival
Scots pine is an ecosystem in its own right, and there are many species that live on it and in it. As well as supporting birds, insects and mammals, there are even trees and other plants that grow within the lofty heights of pine. Rowan in particular can often be seen growing high up in the canopy of a Scots pine. The bright red berries of the rowan are carried in the guts of the birds that eat them, and the seeds then pass out in the birds' droppings, with some germinating and growing where the birds perch on a pine. Birch is another tree that is sometimes found in the canopy of pine.
Sometimes these hitchhiker trees are stunted, living on a small amount of soil that has developed in its niche in the canopy. In other cases they may send a root all the way down to the forest floor. A Scots pine with other trees in its canopy, and festooned with lichens, mosses and ferns is a fantastic sight - a veritable hanging garden!
Pine woodland once covered a huge area of Scotland, but has now been reduced to a tiny fragment of its former extent. There are a number of ways we know where Scots pine once thrived. Pollen grains are incredibly robust, and can survive in the peat for thousands of years, giving us an idea of where pine was at a given time.
Much more obvious are the ancient stumps and roots that look like bare bones as they become exposed when the peat erodes away. Some of these can be as much as 4,000 years old, and have been preserved by their high resin content, and the lack of oxygen in the peat, drastically slowing the process of decay. In some areas pine cones have also been found preserved in the peat, chewed by red squirrels thousands of years ago!
Scots pines vary across their range in Scotland, but only scientists can tell the difference between them
There is much more than meets the eye when it comes to Scots pine. Scientists have found that groups of pines in different parts of the Highlands have evolved unique characteristics and chemistry to help them survive in Scotland's diverse climates. In fact pines separated by a mere 20 kilometres between glens can have distinct differences - this is known as 'biochemical variation', and there are seven main biochemical zones for Scots pine in Scotland.
The chemicals (known as terpenes) serve the tree in a range of ways, such as defending it against insect and fungal attack. Remarkably, in the wetter western Highlands, pines tend to have more of the chemicals that protect the trees against fungi - essential in such a damp climate!
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For more detailed information about Scots pine, please see the Scots pine species profile on this site.