Ecological studies on the Silver Flowe Nature Reserve

Goode, David Anthony

Abstract

[Introduction:]
This thesis is concerned with the development of surface patterns on an area of blanket bog in south-west Scotland. The area concerned forms
part of a series of blanket bogs, collectively known as the Silver Flowe, all of which have conspicuous patterns of deep pools or hollows alternating with firmer areas of the bog surface. Such patterns are commonly found on blanket bogs in northern and western districts of Britain, and are particularly well developed on the extensive 'flows' in Sutherland and Caithness. Similar surface patterns have been described from many peat land areas elsewhere in the northern hemisphere, many of which occur on a scale far greater than those of the British peatlands .

The cause of such patterns has long excited speculation. A review of the literature was written by Auer as long ago as 1920 and a recent appraisal is given by Sjors (1961). In Britain bogs exhibiting these features have been curiously neglected by ecologists until quite recently. In 1956 Pearsall briefly described two such bogs in Sutherland and in 1958 Ratcliffe and Walker described the bogs forming the Silver Flowe. Very
different interpretations were offered to account for essentially similar features and neither of these contributions provides a completely satisfactory explanation of pattern development. Indeed Pearsall's contribution is largely speculation. More recently Boatman and Armstrong (1968) have described an area of blanket bog in west Sutherland, in which numerous deep elongated pools occur. They suggest a possible mechanism to account for pool alignment parallel to the contours of the bog surface.

My aim, in carrying out the investigations which form the basis of this thesis, has been to investigate in detail one area of patterned blanket bog with a view to understanding some of the processes involved in pattern formation. The Silver Flowe in Galloway was an obvious choice for a study area since, not only was it the nearest area of undamaged patterned bog, but it also had the safeguard of being a National Nature Reserve.

Early in planning the work it was decided that several lines of investigation would be adopted within the one study area. This policy arose from a consideration of the various suggestions which have been made, largely by Scandinavian and North American workers, to account for the development of patterned surfaces. In general terms there are two 'schools of thought'. Many workers have suggested that patterns are produced by physical processes by which peat already formed is subject to displacement, at least in the surface layers. Several distinct and unrelated phenomena have been relied upon to account for the development of essentially similar patterns. These include the lateral movement of peat owing to slope of the underlying mineral ground (Troll 1944, Pearsall 1956, Heinselman 1965); desiccation and subsequent shrinkage of peat, resulting in convolutions of the peat surface (Newbould 1958, Pearsall 1956) ; also frost-heaving and other phenomena related to periodic freezing and thawing whereby surface irregularities might be produced (Auer 1920, Drury 1956, Drew and Shanks 1965 and Sigafoos, 1952).

Others suggest that patterns are the result of a specialised form of bog growth, the ridges and hollows forming distinct ecological environments which, once initiated, become accentuated by differential rates of peat accumulation (Sjors 1963 1965, Granlund 1932, Lundqvist 1951, Boatman and Armstrong 1968).

In reviewing the subject of pattern development Ratcliffe (in Burnett 1964) suggests that three main problems require explanation. The first is the underlying cause of hummock and hollow development, in whatever situation. The second is the cause of aligned hollows on sloping bogs and the third is the development of extensive pool networks which he considers are due to erosion. These are still the basic problems. It is worth emphasising that many of the ideas advanced from both 'schools of thought' are in fact no more than speculation based on an examination of surface features. It is surprising, in view of the extent of patterned peatland in the Boreal Zone, and the number of areas which have been described in detail, that very few detailed investigations aimed at understanding the process of pattern formation have been carried out (e.g. Granlund 1932, Boatman and Armstrong 1968 and Ratcliffe and Walker 1958).

If patterns result from a physical process involving some lateral movement of peat then it is reasonable to expect that the distribution of patterns will show a relationship with the form of the underlying mineral ground. Accordingly it was decided that this relationship should be investigated in detail in the area selected for study. In addition analysis of peat stratigraphy was chosen as a second line of investigation in view of the fact that it would provide a most direct means of ascertaining the course of 'pool and ridge' formation .

Detailed examination of water level fluctuation in different types of situation within an area of patterned bog was adopted as the third major line of investigation. In considering the possibility that patterns result from a specialised form of bog growth the most obvious relationship is that of plant communities and microtopography to water table. In the case of the Silver Flowe, Ratcliffe and Walker demonstrated clearly the range of tolerance of different plant species in this respect and many other workers notably Sjors (1948) and Drury (1956) have emphasised the different ecological conditions prevailing in hummock and hollow. The behaviour of the water table in these different conditions had not however been investigated in detail at the time when this work was planned and it appeared that this would be a logical first step in understanding the process of pattern formation as it is occurring at present.

During the course of the work two particular features of the present bog surface posed additional problems which were considered to merit attention. One of these was the accumulation of wind-blown litter of molinia caerulea in pools and wet hollows, a feature which I considered might have an important influence on the present development of the bog surface. The other was the scarcity of aquatic species of Sphagnum in the deeper pools. The small amounts of Sphagnum growing naturally in such situations was observed to disintegrate in the late summer of two successive years and for this reason I decided to investigate the performance of Sphagnum introduced to such conditions.

These various lines of approach to the problem are presented in turn. Each forms the basis of a separate section but throughout the work, wherever it is relevant, the bearing of one line of research on another is discussed. The main points arising from the various sections are drawn together in the final discussion.

Citation

Goode, D. A. (1970). Ecological studies on the Silver Flowe Nature Reserve. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4218077

• Thesis Type: Thesis
• Deposit Date: May 16, 2016
• Publicly Available Date: Feb 23, 2023
• Keywords: Botany
• Public URL: https://hull-repository.worktribe.com/output/4218077
• Additional Information: Department of Botany, The University of Hull
• Award Date: May 1, 1970