Patterned peatland
A patterned peatland (also called a patterned bog or mire) is a peatland whose surface is broken up into a regular pattern of wet hollows and pools, with drier ridges and hummocks between them. The surface of a natural bog usually shows this kind of small-scale patterning, which is created by the different ways that various species of Sphagnum bog moss grow.[1] On mineral soils, bumps and dips are mostly made by physical processes. On a peat bog, the patterns of pools, hummocks and ridges come directly from the growth of living plants and from the way water moves across the surface.[2]
The Flow Country
The best-known patterned bogs in Britain are in the Flow Country, in the far north of Scotland.[3] There the surface is mostly a spongy, living layer of Sphagnum bog moss that keeps building itself higher. In many places, swarms of small peaty pools break it into strange and distinctive patterns.[4] An early writer, Crampton (1911), was one of the first to describe the maze of peat lochans (in Gaelic, dubh lochain) on the higher, flatter parts of the Caithness flows.[5] Since then, many different explanations have been put forward for the striking surface patterns found on so many boreal mires.[6]
How patterns form
How complex the pattern is depends on the bog's water balance, which in turn depends on climate and slope.[7] Extra water is stored in hollows and pools. The more spare water there is, the larger and more complex the pool systems become.[8] In wetter periods of climate, more hollows and pools tend to form.[9] Most of these small-scale surface patterns are found in the bog's living top layer, called the acrotelm.[10]
Wildlife
A small patch of bog can look as if it has few species. However, looking closely at different parts of the pattern, and at different patterns across the bog, will often reveal a surprising variety of plants and animals.[11] Different species and groups of plants live in particular zones within the pattern, much like the bands of life on a rocky seashore. On a bog, though, all these zones are squeezed into a height range that is usually less than 50–75 cm.[12]
See also
References
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
the surface of a natural bog characteristically displays small-scale surface patterning, or microtopography, generally created by the varying growth-forms of differing Sphagnum bog moss species.
- ↑ The Flow Country: The peatlands of Caithness and Sutherland (PDF). Nature Conservancy Council. Retrieved 20 October 2026 – via JNCC.
In a mineral soil, such undulations and irregularities are largely a product of physical processes, whereas the patterns of pools, hummocks and ridges on a mire surface are a direct result of organic growth and surface hydrology.
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
the more celebrated patterned bogs of the Flow Country in the far north of Scotland.
- ↑ The Flow Country: The peatlands of Caithness and Sutherland (PDF). Nature Conservancy Council. Retrieved 20 October 2026 – via JNCC.
The surface is mostly a spongy, living layer of Sphagnum bog-moss which continually builds its level higher by upward growth but is in many places thrown into strange and distinctive patterns by swarms of small peaty pools.
- ↑ The Flow Country: The peatlands of Caithness and Sutherland (PDF). Nature Conservancy Council. Retrieved 20 October 2026 – via JNCC.
Crampton (1911) was one of the first authors to describe the maze of peat lochans (dubh lochain) which occupy the higher, flatter parts of the Caithness flows.
- ↑ The Flow Country: The peatlands of Caithness and Sutherland (PDF). Nature Conservancy Council. Retrieved 20 October 2026 – via JNCC.
a wide range of explanations has been proposed for the striking surface patterns which are found on so many boreal mires
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
The complexity of surface patterning depends on the hydrological balance of the bog, and is determined by climate and slope.
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
Significant quantities of surplus water are stored as hollows or pools, and the greater the quantity of available surplus water, the larger and more complex these pool systems will be.
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
during wet phases in the climate there will be a tendency for greater hollow and pool formation
- ↑ The Flow Country: The peatlands of Caithness and Sutherland (PDF). Nature Conservancy Council. Retrieved 20 October 2026 – via JNCC.
The acrotelm is the layer of most active water movement ... It is also the layer in which the vegetation, root mat and, more strikingly, most of the small-scale surface patterns so typical of bog systems occur
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
closer examination of differing parts within the pattern, and of differing patterns within the bog as a whole, will often reveal a surprising diversity of plant and animal species.
- ↑ "Peat Bog Ecosystems: Structure, Form, State and Condition" (PDF). Briefing Note No. 2. IUCN UK Committee Peatland Programme. Retrieved 20 October 2026.
Within peat bogs, individual species and vegetation groups occupy, or utilise, particular zones within the small-scale surface pattern which resemble the vertical zonation observed on rocky seashores, but squeezed into a total vertical range which typically occupies less than 50-75 cm.