The soil landscapes of Scotland
The Southern Uplands
Several different soil patterns are found in the Southern Uplands. These result both from natural processes and human influence. The patterns are reflected in a variety of habitat types and land uses. One of the main controlling factors is altitude. In the east of the region, the soils often gradually change with increasing height, for example on the Pentland, Lowther and Lammermuir Hills. They generally become shallower, peatier, stonier and less fertile. This is because, as rainfall increases and temperature decreases with height, many of the chemical and biological processes involved in soil formation become slower.
Further west, soil patterns are often more complicated. For instance, in lowland Galloway, the ways in which material was deposited by retreating glaciers greatly influence the soils. The Galloway Hills are more similar to parts of the Highlands and Islands than the easterly hills. They are more rugged with large areas of bare rock, thin covers of glacial deposits and shallow soils. The soil characteristics change rapidly and frequently over short distances.
Land Use
Land use in the Southern Uplands is governed by certain limiting factors, such as slope, temperature and wetness. The altitude at which good quality pasture is possible declines from east to west as rainfall increases. Artificial drainage is often used in the wetter areas to produce grassland suitable for grazing. This alters the characteristics of the soils, for example by reducing waterlogging. Soils in the western Southern Uplands may be stonier and shallower than their eastern counterparts. This places further restrictions on grazing through reduced grass growth (less soil for roots), and therefore the number of animals that the land can support. Agriculture is by far the biggest land use in the Southern Uplands, although forestry has undergone a great deal of expansion in recent decades.
Few of the familiar scenes described here are natural. Apart from the higher hill tops, virtually all the land in the Southern Uplands has been modified by mankind for his own purposes. Historically, most of the area was covered by mature woodland, as indeed was much of Scotland. This was rapidly cleared by early human settlers to provide fuel, building materials and land for agriculture. The soil and vegetation patterns in many areas have changed drastically as a result, particularly at lower altitudes. The landscape that we see around us is, in effect, a man-made one.
The Central Lowlands
The Central Lowlands extend across Scotland between the mountains of the Highlands and the hills of the Southern Uplands. The soil distribution is mainly controlled by the type of material deposited by retreating glaciers following the last Ice Age. This material often contains many small particles, and can produce poorly drained soils, especially in the west where rainfall is higher. Moving towards the drier east, the soils gradually change. Gleys first, then brown forest soils with gleying and finally freely drained brown forest soils on coarser sandy material. This latter soil occurs particularly in river valleys. On higher ground, such as the moors and uplands of Cumnock and around Muirkirk, peats and peaty gleys can be found.
Land Use
Human influence on the vegetation of the Central Lowlands has been profound. A good example is the widespread planting of plantation woodland, both coniferous (for commercial forestry) and deciduous (in estates). Grasses, herbs and rushes have invaded former mining and industrial areas between Edinburgh and Glasgow as these industries disappeared.
Apart from agriculture and forestry, the main land use in the Central Belt is urban and industrial. The conurbations of Edinburgh and Glasgow accommodate a large proportion of the Scottish population. The legacy of land use for mining and other industry is evident to anyone travelling between the two cities and has completely transformed the nature of the landscape. But aside from the visual element, what effect has this had on the soils in the area? In terms of mining and other extraction industries, the soil is often regarded as a hindrance to be removed in order to get at the valuable resource under the surface. Towns, buildings and roads are often located on the best quality soils in a given area. This is because the soils are usually associated with other environmental factors like good drainage, a flat surface for building, and shelter. The soils are effectively rendered unusable and even if they are re-exposed at some time in the future, their characteristics will have been drastically altered. In the past, there were far fewer controls than now on the environmental impacts of development and on disposal of waste materials the consequences of this are obvious in many parts of the region.
In recent years legislation has been greatly improved to protect land. And there is a growing interest in the reclamation and restoration of derelict areas. Areas can be reclaimed by importing topsoil and spreading it over the land surface. However, this can be a very expensive operation. Often a more practical solution is to use the existing material and establish vegetation that can adapt to the conditions. Over time, the soil quality can improve. Derelict land is often deficient in nitrogen, an essential plant nutrient. Legumes plants which can take up nitrogen directly from the atmosphere are very useful in these situations. The nitrogen is released into the soil when the plant dies and decays. Some other plants are tolerant to high concentrations of certain metals, and others still of very acid conditions. The rate of improvement may be increased by adding organic waste by-products, including animal slurry, sewage sludge and other recycled organic wastes. Many of the large number of coal and oil shale bings in, for example, the area around Hamilton and Motherwell, have been successfully reclaimed in this way. The restored land is put to a variety of uses.
The Highlands
The Highlands of Scotland form the largest of our geographical regions and probably the most diverse in terms of landscape and soil patterns. The soil pattern in the Highlands is influenced to a large extent by climate, especially temperature and rainfall. Changes in soil type with altitude are quite marked. Many Highland soils are stony and coarse textured: they are also characterised by being wet and acid, with high organic contents. These are properties inherited from the parent materials of the region. A typical soil pattern is podzols and brown forest soils on gentle slopes, with gleys and peats in depressions.
A hard brittle layer known as an indurated horizon is often found in Highland soils. It usually occurs close to the soil surface (within about 40cm). It is thought to form as a result of freezing and thawing cycles which redistribute the soil material. Indurated horizons can be found in many different soil types. They are important because they can block drainage and also stop plant roots reaching far into the soil. Most Highland soils are very shallow, often due to shallow parent materials. Peat is very common throughout the Highlands, in fact, it occurs more widely in Scotland than anywhere else in Europe, except Ireland.
Land Use
The Highland soil conditions impose severe restrictions on land use. Steep slopes and wet, peaty surfaces make the use of agricultural machinery difficult. When rainfall is lower usually in late spring non-peaty soils can dry out quickly, creating further management problems. In the past, labour-intensive management allowed small patches of good land to be worked fairly easily. Modern developments in intensive agriculture the trend towards larger fields and machinery, for example are largely unsuitable here. In general, the land once used for cropping is now under grass. The main land use in the Highlands is rough grazing. Lower ground, in Strathspey for instance, is used for winter grazing and cropping.
Most woodlands in the Highlands are small and patchy larger areas (both coniferous and deciduous) are usually plantations. Oak and birch woodland are common at lower altitudes, on brown forest soils and podzols. The mix of species varies between the east and the west of the region. Recreation is an important land use in the Highlands and is both indirectly and directly related to soil type. Deerstalking and grouse shooting, for example, are associated with particular moorland habitats which are closely linked to the underlying soils.
In some parts of the Highlands, soil erosion is becoming increasingly significant. Given the vulnerability of the soils, it requires relatively little disturbance to cause damage, particularly on peaty surfaces. The causes of erosion can be complex and varied but overgrazing by sheep or deer is often involved. Recreational pressures from, for example, skiing developments or large numbers of walkers concentrated into small areas, also cause soil erosion.
Forestry is affected in a similar way to agriculture by soil limitations. Restricted root volume (due to shallow soils), lack of moisture and the suppression of many species by heather at planting time are the main problems. The best areas are in the lower sheltered glens where soils are deepest. In most areas, only Scots pine, lodgepole pine and sitka spruce are widespread.
The East Coast Belt
The eastern coastal belt forms the main agricultural zone in Scotland. It fringes the mountains of the Grampian Highlands, and extends northwards to the Moray Firth and Caithness and south to Fife, with parts of the Lothians and the Merse of Berwickshire. The most northerly part of the region, the Caithness Plain, contains soils which are rather different to the rest mainly gleys, with some peat. The dominant soils of the Moray Firth area are podzols developed on coarse, acid parent materials. Further south, the soil pattern becomes rather more complex, dominated by podzols and brown forest soils.
Land Use
Cereals and root crops are grown in many parts of the region; market gardening is also common. On parts of the coast itself, there are large areas of windblown sand. Here, the soil profile development is limited, due partly to the effects of continual deposition of sand. For example, soils on the windblown sands at Tentsmuir and at Culbin Sands are little more than a thin organic layer developing directly on the sand itself. Distinctive dune vegetation communities can be seen. Where the soils have been longer established, a greater variety of grasses can survive, making the land suitable for grazing or for use as golf links. The main restrictions on land use in the coastal strip are periodic drying out (due to sandy soils and low rainfall levels), and also exposure to strong winds. Where these limitations cause particular problems, the land is used for pasture rather than crops. There are recreational pressures associated with the use of the dune soils for activities like caravanning and camping. These include compaction and increased susceptibility to erosion.
Soil erosion is not widespread but can be locally significant. There may be a number of causes, for example leaving fields bare at vulnerable time of the year and removing field boundaries. A gradual decline in organic matter content (important in binding soil particles together), following centuries of cropping may also be involved. Another important issue is the use of fertilisers which, if applied in excess, can lead to nutrients like nitrogen and phosphorus being released into watercourses.
The Islands
Although we are grouping the islands of Scotland together into one region, they contain a wide variety of soil types and landscapes.
Western Isles
The landscape of the Outer and Inner Hebrides is very variable. This produces frequent changes in the soils over short distances. The pattern of outcrops and hollows, slopes, and depths of parent material are involved. Vast expanses of peat dominate the landscape.
Human influence can be important in areas where peat has been removed and the ground cultivated. Lewis, the Uists and Benbecula are examples. Cultivation is also carried out on the dune (machair) soils, for instance, along the coast around the western Uists. In the Outer Hebrides, most of the remaining land is moorland. Woodland is confined to very small sheltered areas. In the Inner Hebrides, grassland is more evident on the brown forest soils and the gleys. Small pockets of moorland occur on podzols. Most of the soils of both the Outer and Inner Hebrides are susceptible to damage by recreational activities, such as hillwalking and camping.
Orkney
Much of Orkney is either cultivated or under permanent pasture. Moorland is restricted to the more hilly areas. Most of the rough grazing is on the slopes, where soil improvement is rarely economically viable. Beef cattle and sheep are the main land use. The soils are quite vulnerable to physical damage, both by animals and by machinery. Forestry is not common on Orkney due to the frequency of gales, the salty air and the necessity to use the land primarily for agriculture. Because the soils are generally fairly fertile, level and relatively stone free, they can be drained where necessary and used for cropping. As a result, arable agriculture is common. As in the Hebrides, the soils are vulnerable to recreational pressures.
Shetland
Cultivated land in Shetland is mainly restricted to the mineral soils around the coast. Here, the centuries-old practice of manuring has helped to increase the depth and the quality of the topsoil quite significantly. Crofting is widespread and the landscape reflects this. Woodland is extremely scarce in Shetland as it is in Orkney. Soils are generally shallow and stony, low in fertility and with thick organic surfaces. There is however, considerable soil variation over short distances. This makes land drainage and widespread cultivation impractical. Rough grazing makes up around 90 per cent of the total land in Shetland.