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Tuomikoski linked the Finnish Cajanderian school of mire and forest site classification by its theoretical base close to the Central- European school of vegetation science and not close to the Swedish Uppsala school, which was rather dominating in the beginning of the 1900s in Nordic countries.The mire study of Tuomikoski remained rather unknown, probably because it was published in German language in Finland during the Second World War. After the war the vegetation science developed mostly in anglo- american world, where the German texts neither were understood nor read. Another probable reason was that the second part of his work with concrete data was never published.

The most comprehensive mire vegetation dataset have been published in the regional studies of Finnish mires by Ruuhijrvi (1960) and Eurola (1962).

In Finland there are also large unpublished mire vegetation datasets, which has been collected by botanists as a part of studies of peatland agriculture and National survey of forests. The modern vegetation science of mires in Finland was started by Pakarinen (1976, 1978, 1979, 1982, 1985). At present the use of different ordination and clustering methods is usual and almost a standard (e.g.

Heikkil 1987). It is important to note that these approaches have not changed the basic character and classification of the mire site system. The idea of multidimensional continuum system has even become clearer in modern thinking (fig.).

The difficulty to create uniform international mire classification is not only because of the different scientific schools, but also the differences of mires in different areas and the different way to separate mires from other ecosystems like forests. Also the difficulty to translate the national concepts and terms is great. So the best common understanding of mire vegetation and classification is reached by the understanding the ecological continuums in mires.

Different gradients, as the basis of mire site type description Ombrotrophy minerotrophy. The division of mires to those fed only by rain and those with rain and waters from mineral soil became as main concepts of general mire ecology after the studies of Sjrs (1948) and Du Rietz (1954). In Finnish mire complex and site type these concepts were adopted by Ruuhijrvi (1960) and Eurola (1962). The boundary between ombrotrophy and minerotrophy is a gradient like all boundaries in mire vegetation and different plants react to that in a different way. Plants are the only reliable way to measure this bog fen gradient.

In the climate of Finland this measurement is rather easy and the progressive development of mires even makes that more clear. We would loose lot of regional information of mires, if we would abandon these concepts as Wheeler & Proctor (2000) have proposed. In all cases ombro- and minerotrophy cannot be separated by chemical characteristics is not acceptable (Sjrs & Gunnarson 2002, Tahvanainen 2005).

Oligotrophy mesotrophy eutrophy. This concept divides the fertility gradient of mires from poor to moderate fertile to rich. These terms have no connection on to those used in limnology, where they are connected to production. The best explainer of the gradient is pH, the strongest of the chemical parameters in mire water (Tahvanainen 2005).

In rich mires also carbonate ions have a great role. Most of the oligotrophic vegetation can be found in the central parts of mires, and meso eutrophy can be found mostly on the margins of the mires. The mire plants explain clearly along this gradient.

Mire margin gradient. Mire margin is a special gradient, which is indicated by the species of forests, shores and springs. The special conditions they need are a result of thin peat, flow of spring waters or abundance flooding waters. The diversity is at the highest along the mire margin gradient. The biggest species group is the group of joint species of forested thin peated mire habitats and mineral soil forests. It contains about 250 species, i.e. about 60 per cent of all mire species. Also a good growth of tree stand is typical of this gradient when compared with other mire gradients. In Finland this mire margin gradient characterized by the effect of mineral soil is called to korpisuus (in German: Bruchmoorigkeit) (Heikurainen 1953, Ruuhijrvi 1960).

The abundance of common species with forests indicated that mires and forests belong to the same boreal vegetation system. Thus their regionality can be jointly studied in boreal forests mire biome.

Ground water effect creates springs in the mires and at the same gives a niche to meso eutrophic spring vegetation and flora. Springs are also cool, and in winter frostless habitats, giving a niche for frost sensitive plant species. The surface water effect creates the flooded habitat vegetation (in German: Sumpfigkeit). It is strongest on the sides of streams and lakes, which are flooded regularly. Weakest the flood influence is in the central parts of aapamires, where flood comes from the melting water of mire and its surrounding. That has been also called as melt water influence (Eurola & al. 1994). In fell areas and arctic areas the water of mires is mostly snowmelt water. Flood and more commonly melt water is an important source of minerotrophy. It also keeps aapamires in minerotrophic state. The water from outside of mire is less acid preserves and it dilutes the effect of humus acids and so prevents the mires to develop to ombrotrophic (Tahvanainen & al. 2003).



Mire expanse influence. The central part of mire is living with the nutrients fed by rain and with the available nutrients of peat. The mire expanse influence is identified by the presence of real mire plants and by the lacking of the species indicating mire margin influence. All ombrotrophic vegetation is mire expanse vegetation, and also the treeless open fens and thick peated minerotrophic pine.mires.

Mire water table. The surface of mires consists of several microtopographical cases, from dry hummocks to vegetationless mud bottoms and water pools. The differences in different mire water table are most clear in the mire expanse vegetation of bogs. The gradual moisture gradient is commonly divided on the basis of plant species to hummocks, lawns, moss carpet hollows and flarks to mud bottom. Many mire site types has typical several levels of moisture. Site type is named after the prevailing level of moisture and it is also possible to have more precise naming using less prevailing moisture level.

Some other gradients of mires. Mires can be seen also complex systems of hydrotopography. On raised bogs these approaches has been a tradition already for a long time (e.g. Weber 1902, Osvald 1923, Aario 1932). In the case of aapamires this approach has less used and it has not been equally logical, although the division into ombrotrophic, mire margin and sloping fen part is easy to make using aerial photographs (Ruuhijrvi 1960, Havas 1961). Recently Laitinen & al (2005) have made an excellent analysis on the structure of a case aapamire complex about the peripheral and central parts in relation to hydrological flows of surface and soil waters. They showed that doing this it is easier to explain the location of mire site types and surface topography and also the effect of the ground soil.

The hydrology and vegetation is also a result of climate, especially oceanity continentality gradient is important. Although mires can develop ombrotrophic everywhere in boreal and temperate vegetation zones, minerothrophic mires have, however, their spesific areas, where they are dominant among mires (Cajander 1913, Katz 1948, Ruuhijrvi 1960,, Yurkovskaya 1975 and 1995, Boch & Masing 1983) The spatial model of mire vegetation has also a fourth dimension; time.

While peat deposits are getting thicker and the moisture and nutrient relations of sites change also. The application of the slow natural change to the model is difficult, but important in forecasting future e.g the effect of global warming.

The drying of mires after drainage for forestry is fast and well documented.

The succession series of drainage areas: (drainage stage, transitional stage and peat heath stage) can be identified in the beginning to each mire site type and later in different nutrient level and mire margin influence level. These drainage succession habitats have studied actively in peatland forestry (Paavilainen & Pivnen 1995). Drainage has resulted in a remarkable change in Finnish mires, because more than half of the mire area has been drained. The drainage has destroyed over 90 percent of their area in the case of many forested mire site types habitats The hydrological effect of drainage reaches often outside the drainage area, causing slow succession.

The main elements of the vegetation system of mires The authors have studied and evaluated mires many ten years. During that period We have summarized with our field experience and with collected data our concepts of the character of mire vegetation and mire classification.

They are as following.

1. Mire vegetation forms a model of a multidimensional spatial system. It is possible also to determine it as a coordinate system or network, where the axes form the ecological gradients, including hydrology, topography, geographic regions and time.

2. Mire plants, and ecological groups of plants and plant communities are located in this model in serial order as a continuum, without boundaries and probably also without dense locations or nodes.

3. Thus there is order in mire vegetation, but not organization, no hierarchical classes as it is systematics of plants and animals. Language needs an organization and names, to make it possible to understand each other.

4. Classes or mire site types are abstracts, averages and agreed. Multidimensionality makes the organization difficult, also different divisions are optional. Any of the divisions is necessarily not more correct than others. The question is how the spatial system and the time continuity has been divided to a specific need to use it.

5. It has been typical for the Finnish mire site classification system to use short site type names, but also to use with them names of plants, ecological adjectives and attributes contenting description. This makes it possible to describe gradual natural variation and the relationships between site types. Site type name is a short description and definition of the vegetation.

6. Mires (as well forests too) can be seen as a network of nature, a network which is like a general law of nature.. The same idea can be seen also inside living cells in network and interaction of proteins. Also the world wide web has similar way to function.

References:

Aario, L. 1932: Pflanzentopographische und palogeographische Mooruntersuchungen in N-Satakunta. - Fennia 55(1): 1-189.

Boch, M. & Masing, V. 1983: Mire ecosystems in the U.S.S.R. In: World ecosystems. Vol 4B. Mires: Swamp, Bog, Fen and Moor. Regional studies. Amsterdam, Elsevier. pp. 95152.





Cajander, A. K. 1906: Maamme soista ja niiden metstaloudellisesta merkityksest. I. Soittemme luonnonhistoria. [Mires and their importance in peatland forestry in Finland. I. Natural history of our mires.] Suomen Metsnhoitoyhdistyksen Julkaisuja 23(3): 172.

Cajander, A. K. 1909: ber Waldtypen. Fennia 28(2): 1175.) Cajander, A. K. 1910: Suot. [Mires] - Suomen Kartasto. 1910: 1-26. Helsinki Cajander, A. K. 1911a: Metshallituksen suonkuivaustiss kytetyt suotyypit.[The mire site types system used in drainage activities in National Board of Forestry.] Metshallinnon vuosikertomus 1911: 1-10.

Cajander, A. K. 1911b: Vesiperisten maiden kuivattaminen metsnkasvua varten. [The drainage of waterlogged soils for forestry.] Statistique Forestiere 15: 88 98.

Cajander, A. K. 1913: Studien ber die Moore Finnlands. Acta Forestalia Fennica 2(3): 1-208.

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Du Rietz 1954: Die Mineralbodenwasserzeigergrenze als Grundlage einer naturlichcen Zweigliederung der nord- und mittel-europischen Moore. Vegetatio 5 6 : 571585.

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Eurola, S., Hicks, S. & Kaakinen, E. 1984: Key to Finnish mire types. In:

Moore, P. D. (ed.) European mires. pp. 11-117. Academic Press. London Eurola. S., Huttunen, A. & Kukko-Oja. K. 1994: Suokasvillisuusopas. [Mire vegetation guide] Oulanka Reports 13: 1-81.

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Lukkala, O. J. & Kotilainen, M. J. 1945: Soiden ojituskelpoisuus. [Mires site types suitable for peatland forestry.] the 4th ed. Keskusmetsseura Tapio, Helsinki. 56 s.

Lukkala, O. J. & Kotilainen, M. J. 1951: Soiden ojituskelpoisuus. [Mires site types suitable for peatland forestry.] the 5th ed. Keskusmetsseura Tapio, Helsinki. 63 s.

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Pakarinen, P. 1976: Agglomerative clustering and factor analysis of south Finnish mire types. Annales Botanici Fennici 13: 35-41.

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Proc. Int. Symp. on Classification of peat and peatlands, Hyytil, Finland.

September 17-21, 1979. IPS. Helsinki. pp. 121-134.

Pakarinen, P. 1982: Etel-Suomen suo ja metstyyppien numeerisesta luokittelusta. (Summary: Numerical classification of South Finnish mire and forest types.) Suo 33: 97-103.

Pakarinen, P. 1985: Nuerical approaches to the classification of North Finnish mire vegetation. Aquilo Ser. Botanica. 21: 111-116.

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