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Multilevel approach
in
mire mapping, research,
and classification

Viktor Masing,
University of Tartu
Contribution to the IMCG Classification Workshop
March 25-29, 1998, Greifswald

Mire science, called (telmatology) by J. Klinge (in his lectures in 1891) and (Moorkunde) by recent German scientists, has its roots both in botany (as Moorbotanik or Hydrobotanik), studying wetland plants and plant communities, and in geology (as Moorgeologie, Torfkunde), investigating peat and peat deposits. It was already shown in the 19^th century that plants growing on inundated soils and decomposing incompletely constitute peat forming plants, and that water and peat together in their mutual interdependence form a natural phenomena called, in English, bog, fen, swamp or moor, united nowadays in the term mire (in German Moor, in Finnish suo, in Russian boloto, etc.). Yet the dualistic origin of mire science has influenced the development of mire terminology in two directions, and botanical (phytosociological, ecological) classifications exist in parallel to geological (geomorphological) ones.

Already in the classical works by A. Cajander (1913), Hugo Osvald (1923) and others, the term bog had two meanings: a kind of plant community (classified as associations or other kinds of syntaxonomical units), and a landform (a concave depression or a convex mound consisting of peat and covered with a specific vegetation). The latter was named Grossmoor and classified according to its surface topography (Grossform) or peat characters.

The third (intermediate) structural level of bogs was first described by A. Cajander (as Kombination von Moortypen") and H. Osvald (as Assoziationskomplex). These were bog sites with certain regularly alternating plant communities on hummocks, hummock ridges and the hollows or flarks between them. It can be observed that these kinds of complexes occupy a certain position in convex bogs. The ridge-and-hollow complexes are situated on gently sloping areas, ridge-and-pool complexes are developed from the latter in the principal direction of surface runoff. These complexes have been named and classified according to their constituent parts.

The next step in the differentiation of bog structural levels was made by Jekaterina Galkina, a Russian geographer who has worked since the 1930-s with aerial photographs and their deciphering for geobotanical mapping purposes. During the Leningrad blockade of World War II her excellent knowledge was used for solving military problems. After the war in 1946 she published her study dividing all mire landscape structures visible from the air into 3 levels differing in scale: (i) mikrolandschaft (mikrolandscape), (ii) mesolandshaft (mesolandscapes), corresponding to Grossmoor, mesotope or bog complex, and (iii) makrolandshaft (macrolandscape or mire-system consisting of joint bogs and bog water bodies).

Galkina's ideas at once found practical applications in mire hydrology. A microlandscape can be treated as the smallest hydrographical unit with unidirectional water movement (in bogs across ridges and longitudinal pools). A mesolandscape has in the simplest case a radial network of outflow directions - centripeal in depressions and centrifugal in convex bogs. In their further development and expansion the bog peat body is divided by outlet brooks into two or more secondary centres which also have a concentric structure visible from the air. Macrolandscapes are vast mire territories containing a number of joined bogs in different stages, or separated by streams.

These regularities were used in the hydrological theory of water movement in mires by K. Ivanov (1953, 1957). He was the first to construct mathematical models of bog growth and development.

Galkinas's ideas were widely accepted among Russian mire explorers. Unfortunately, the terms derived from the German Landschaft were deemed unsuitable for use in the Russian language, and so Galkina decided to rename the microlandscape fatsia (from Latin facies) and the mesolandscape was called an urotshishtshe - a word absolutely unpronounceable for foreigners - or a mire massif. The term mire facies (bolotnaya fatsia) found approval in Russian literature inspite of its somewhat different meaning in geology and palaeontology.

All the above mentioned classical works together with the general system theory by Bertalanfy and the universal concept of levels of integration (organization) by American biologists influenced me (then as a postgraduate) to elaborate a general approach of bog structure applicable for vegetation mappping and research (Masing 1963). In Estonia we have a fascinating variety of bogs, then nearly untouched by human activity, which were already valued by foreign scientists visiting Estonia (H. Gams, I. Kujala, I. Paasio and others).

My first attempt to use the traditional syntaxonomy for mapping purposes in bogs failed. The plant communities in bogs are mostly dispersed in small patches. This kind of patchiness could be described better using the Scandinavian (Du Rietz) approach or using the synusial method elaborated by our professor T. Lippmaa (1933). In this way it was not yet possible to give an adequate description of the bog surface structure.

In 1955 a simple step method (a kind of line intercept method along transect) for mapping purposes and the description of microtopography was elaborated (Masing, Trass 1955; Masing 1996).

Thus an important subject appeared to be the single forms of the bog surface which we named microforms (a form of microrelief): moss hummock, hummock ridge, hollows covered with Sphagnum or bare mud. Later we added compound microforms, such as hummock-ridges and bigger hollow-pools (Zobel and Masing 1987). These microforms mostly have a mosaic of vegetation patches with their own microsuccessions, but the hummocks as a rule appeared to be very stable and old. Their orientation was initially obviously determined by the main outflow direction (Ivanov 1953), but with the growth of the bog as a whole this can change. One case has been described where a ditch dug a hundred years ago caused the formation of new ridges at a right angle to the former ones (Masing 1982 p.70). This example shows the importance of the description of microtopography on a microform level.

During decades of studying the dynamic structure of bog vegetation the problem arose, which structural element of the vegetation is the most important as an elementary part, as a molecule", of the plant cover. Phytosociologists have insisted that the fundamental (basic) building block" in vegetation ought to be the plant community, classified into associations and other units of the syntaxonomy. Scandinavian and Estonian botanists have preferred a smaller elemtary unit, a sociation, layer society" or synusia. In forests and grasslands the latter approach has justified expectations. In poor fens, red beds and marshes it is hardly possible to find another vegetation unit more suitable for description and mapping purposes. In flood plains strong sedge tussocks can be treated as the smallest natural elements of this vegetation.

In the complicated microtopography of bogs, associations are represented only as fragments dispersed on micrforms of the same type; the moss hummock seems to be a more natural element of vegetation. Hummocks grow and their development seems to be regulated by hydrological conditions. Isolated hummocks such as pool islands become round in shape and develop a more or less distinct diameter (Mets 1978). In these cases hummocks behave" as natural vegetation entities. More frequently hummocks join into ridges and form compound microforms of different size and appearance.

Taking into account that the surface of virgin bogs is densely coverd with mosses, it is justified to look for the smallest element of vegetation in this layer. Patches of Sphagnum mosses of different species and of various combinations of coexisting species (included fungi and algea) have different growth parameters, vitality and density, they have different influences on other plants competing for space, light and nutrients. Vegetative reproduction, branching and spreading is regulated by water input, but in experiments a kind of self-regulation can be observed (Smolyanitski 1980). Little is still known about the life history of Sphagnum clones, but often degeneration of moss patches can be observed (Masing 1984). Weakened moss cover gives intruders a chance - dwarf shrubs and graminoids - and in such a way a characteristic mosaic of sphagnophilous and sphagnophobous plant species develops in the moss and field layers of bog communities. All these considerations give reason to speak about clonal level in moss-covered bogs where a Sphagnum clone with its companions and symbionts is the smallest element of plant cover.

Summing up all the abovementioned considerations six typological and one regional level of investigation of boreal mires can be proposed (Table).

Table: Levels of investigation in boreal mire research (Masing 1984, improved)
 

These structural elements of mires, which to a greater on lesser extent possess mechanisms of selfregulation, are from the standpoint of a system approach, more important (informative) and more integral. Such qualities can be found in Sphagnum clones on a population level, on certain kinds of hummocks on a microstructural level and in growing bogs on a mesostructural level. Microtopes are merely parts of the bog complex or mesotope as a whole. Phanerogam plant communities, their fragments and complexes - the most intensively described component of mires - are important for mire development primarily due to their ability to describe the qualitative properties and diversity of peat producers, but their regulative role is moderate. Only trees (in Estonia bog ecotypes of Scotch pine) in certain conditions may suppres the growth of Sphagnum mosses.

The division of mire features into levels and the quantitative limits of the latter are elaborated for the boreal zone. Investigations carried out in other climatic zones (Botch & Masing 1983; Lappalainen 1996) have shown significant differences in the factors influencing mire formation and have demanded different methods of mire research, including even the number of levels of investigation.

In the Northern Subarctic zone of Eurasia palsa mires are regionally distributed.The main feature of these mires is the occurrence of cryogenic peat hillocks, named palsas, and sedge fens between them: this is equivalent to a structure between the macro- and mesostructural levels of our scheme, with the macrostructural level absent.

In the Arctic zone of Siberia peat has been accumulated only diffusely in hummock rows along frost cracks in the so-called polygon mires of tundra lowlands. Thus meso- and macrostrucural level are missing.

In Western Europe vast mire landscapes have been destroyed or have not existed at all. On the other hand, in East Europe and West Siberia bogs have in the course of time expanded, joined and formed large complexes of bog complexes" for which there is no term in English literature. The author has recommended the term mire system" for international use. Mire systems may be homonomous if the bogs united into one large mire system belong to the same mire (complex) type, and heteronomous, if they belong to different types (Masing 1972). Estonian mire systems have developed in postglacial lake depressions (limnogeneous) or in lagoons of the ancient sea coast (thalassogeneous) (Masing 1982) Now the term macrotope has been proposed (Joosten 1996).

Thus the question of investigation levels in mire research should be resolved independently for every climatic zone depending on the natural factors and processes which form and regulate the structural elements of mire ecosystems.

Botch, M. & Masing, V., 1983. Mire ecosystems in the U.S.S.R. - In: World ecosystems, Vol. 4B. Amsterdam, Oxford, New York, Elsevier, p. 95-152.

Cajander, A.K., 1913. Studien über die Moore Finnlands. Acta Forestalia Fennica 2, p. 1-208.

Galkina, E.A., 1946. Bolotnye landshafty i principy ikh klassifikatsii (Mire landscapes and principles of their classification). In: Sbornik nauchnykh rabot Botan. Instituta imemi V.L. Komarova AN SSSR, p. 139-156 (in Russian).

Ivanov, K.E., 1953. Gidrologiya bolot (Mire hydrology). Leningrad, 300 pp. (in Russian).

Ivanov, K.E., 1957. Osnovy gidrologi i bolot lesnoi zony (Fundamentals of mire hydrology of forest zone). Leningrad, 500 pp. (in Russian).

Joosten, H., 1996. A world of mires: criteria for identifying mires of global conservation significance. - In: 10^th International Peat Congress, Vol 3. Ed.: G. Lüttig, Stuttgart, p. 18-25.

Lappalainen, E. (ed.), 1996. Global peat resources. - International Peat Society, UNESCO, Geological Survey of Finland. 359 pp.

Lippmaa, T., 1933. Grundzüge der pflanzensoziologischen Metodik hebst einer Klassifikation der Pflanzenassoziationen Estlands. - Tartu Ülikooli juures oleva Loodusuurijate Seltsi Aruanded. XL. 1-2. P. 1-170. (In Estonian with German summary).

Masing, V., 1963. Methods and theoretical problems of the large scale mapping of vegetation. - Tartu Riikliku Ülikooli toimetised. 136, p. 220-243. (In Estonian with English summary).

Masing, V., 1972. Typological approach in mire landscape study (with a brief multilingual vocabulary of mire landscape structure) - In: Estonia. Geographical studies, Tallinn. P. 41-85.

Masing, V., 1984. Estonian bogs: plant cover, succession and classification. - In: European mires. Ed. P.D. Moore. Acad. Press, London. P. 120-148.

Masing, V., 1996. The step method - a rapid quantative method for mapping the surface topography of a mire. In: 10^th International Peat Congress, vol. 4, Ed. G.W. Lüttig. Stuttgart, p.31.

Masing, V. & Trass, H., 1955. Juhend soode geobotaaniliseks uurimiseks (Instruction for geobotanical investigation of mires). - Abiks loodusevaatlejale 23, Tartu, 82 pp. (In Estonian).

Mets, L., 1978. About the movement of water and development of the mire microrelief in a bog pool complex. - Acta et Comm. Univ. Tartuensis 440, p. 46-55. (In Russian with English summary).

Osvald, H., 1923. Die Vegetation des Hochmoores Komosse. - SV. Växtsoc. Sällsk 1, p- 1-436.

Zobel, M. & Masing, V., 1987. Bogs changing in time and space. Arch. Hydrobiol. Beih. Ergebn. Limnol. 27, p. 41-55.