The highest recorded peat increment rates are 2-3 mm yr-1 in young coastal bogs (Mkil & Toivonen 2004b), while the lowest rates of under 0.mm yr-1 are found in the uplands of northern and eastern Finland. The average peat increment rate for the whole investigated area is 0.32 mm yr-1, while in the raised bog area it is 0.59 mm yr-1 and in the aapa mire area 0.25 mm yr-(Fig. 2). The rate in areas deeper than 2 metres, when northern aapa and palsa areas are excluded, is 0.40 mm yr-1.
The vertical peat increment rates continuously declined between the years 10 000–5000 cal BP (Fig. 2). Thereafter there has been an increase up to the present day. During the last 5000 years the long-term peat increment rates have grown more clearly in raised bog than aapa mire areas (Fig. 2). The increase in peat increment rates in raised bogs may indicate not only the development of Sphagnum dominated plant associations but also the change towards a cooler and moister climate. The highest vertical peat increment rates were characteristic of mires during the last 1000 years when the average rate was about 0.8 mm yr-1 in raised bogs, 1,8 mm yr-1 in young raised bog and 0.mm yr-1 in aapa mires (Fig. 3).
Fig. 2. The long-term peat increment in raised bog and aapa mire areas. The trend lines fitted to the raised bog and aapa mire data have been calculated by 6.rate polynomial.
Fig 3. Rate of vertical peat increment in raised bogs, in young raised bog and in aapa mires according to 39 dated peat profiles.
Discussion/Conclusions Peat increment depends on various factors, including the paludification mode, water permeability, bottom soil nutrient content, the topography of the area determining runoff conditions, plant ecology (species composition, diversity), changes in the water balance of the mire, the number of fires, the age of the deposits, the decay properties of the plant species and the climate (e.g. Tolonen 1973, Aaby & Tauber 1975, Johnson & Damman 1991, Korhola 1992, Mkil 1997). The highest recorded rates are found in young coastal bogs with clayey nutrient-rich bottom soil. The humid climate near the sea is favourable to Sphagnum peat increment and the growing season is long because of early, mild and snowless springs. High peat increment rates are also found in places where the mire basin is characterized by filled in water bodies and/or depressions in the bottom soil topography. The lowest rates are found in northern Finland in basins with a sloping well permeable bottom soil topography. The short growing season in northern Finland and severe winters with strong frost action have resulted in slower peat increment and higher compression compared to southern raised bogs. Mire fires have also slowed down the progress of vertical peat increment in eastern Finland (Mkil 1997, Pitknen et al. 1999). Peat increment is greater in bogs than in fens, because of efficient aerobic decay in minerotrophic fens receiving nutrients with oxygenated water from the adjacent mineral soils, while ombrotrophic bogs are fed only by rain water (e.g. Damman 1996, Mkil et al. 2001).
Fig. 4. The variability of the long-term peat increment in various parts of Finland.
The long-term peat increment in Finnish mires varies considerably, depending on many factors. For example, the peat increment rate is higher in geologically young mires than in old ones (Figs 3 and 4), higher in southern and western than in eastern and northern Finland, and higher in ombrotrophic bogs than in minerotrophic mires (Fig. 4). In addition, the rate has varied greatly during the Holocene (Fig. 3). Variations in peat increment rates can mainly be explained by the vegetation composition and decomposition rates due to natural mire succession and variations in local conditions, but the role of climate cannot be ignored.
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Damman, A.W.H. 1996. Peat accumulation in fens and bogs: effects of hydrology and fertility. In: R. Laiho, J. Laine & H. Vasander (eds) Northern Peatlands in Global Climatic Change. Proceedings of the International Workshop.
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101 pp., 54 figs, 19 tables and 7 appendices.
REGIONAL VARIATION AND PROTECTION OF MIRES IN NORWAY A. MOEN Norwegian University of Science and Technology (NTNU), Museum of Natural History and Archaeology, firstname.lastname@example.org Mire terminology, emphasis on geographical concepts During the work on the Norwegian national plan for mire nature reserves (started in 1969), classification systems founded on the Fennoscandinavian approach were used, based on works like Tuomikoski (1942), Sjrs (1948), DuRietz (1954), Ruuhijrvi (1960), Eurola (1962) and Malmer (1962). The main terms and subdivisions used in Norway are presented here, further description in Moen (1995b).
Basic concepts. The Norwegian term "myr" meaning mire is defined as an area with a high water table, and usually with peat-forming vegetation.
Mire is thus a geographical concept that embraces both the vegetation and the substrate (i.e. the peat). In addition, the term mire is sometimes used to characterise the habitat. The term "torv", meaning peat, consists of the organic remnants accumulated in mire systems. Peatland (Norw.
torvmark) is an area covered by peat of a certain depth, usually at least 30 cm in Norway. Some areas of mire (e.g. shallow sloping fens) are not defined as peatland; likewise the opposite, peatland drained for agriculture and used intensively as pastures, or areas where peat is being cut, qualify as peatland (until the peat depth becomes too thin), but are no longer mire ecosystems.
Mires can be subdivided into two main types: ombrotrophic mires (= bogs, Norw. nedbrmyr) that receive only atmospheric (= ombrogenous) water, and minerotrophic mires (= fens, Norw. jordvannmyr) that, in addition, receive water from the mineral soil. The Scandinavian tradition has been to use the suffixes “-trophic” (fed) for geographical and biological terms, and “-genous” (made) as geological and hydrological terms.
The water level in the subsoil (the water table) is defined as the highest level at which free (hydrostatic) water occurs, and all water below this level is termed groundwater. Soil saturation occurs wherever the water table is close to the soil surface.
Hydrological subdivision. Mires can be subdivided hydrologically into ombrogenous and minerogenous (= geogenous) mires. Minerogenous mires can be further subdivided into: Topogenous mires which are influenced by stagnant water; the water table is more or less horizontal.
Soligenous mires are influenced by seepage water; the water table is not horizontal. Limnogenous mires receive periodical supplies of flood water from other sources; the temporary water table is horizontal, having an effect similar to that in topogenous mires. In general, the mineral subsoil beneath a soligenous mire is sloping, whereas it is flat beneath topogenous and limnogenous mires.
Springs carry minerogenous water to the surface; they are classified as either eustatic or astatic. The rate of water flow, the water temperature and the chemical composition of the water in a eustatic spring (Norw. stabil kilde) remain constant throughout the year, whereas these parameters vary in an astatic spring (Norw. ustabil kilde) (cf. Dahl 1957).
Geographical concepts of mire: feature, site, massif, system and region The concept "mire complex" was originally used by Cajander (1913). Sjrs (1948) proposed and defined the chain of geographical concepts: mire feature, mire site and mire complex. At the macro level, Russian and Estonian researchers (see Yurkovskaya 1995) separated between mire massifs and mire systems. An equivalent chain of four levels has been in common use in recent decades for the local geographical units, often with different names for the terms, for instance Ivanov (1981:
microform, microtope, mesotope, macrotope), Lindsay et al. (1988: microform, microtope, unit, complex). The following terms have been used in Norwegian mire reports and publications after 1980 (e.g. Moen 1985):
feature (Norw. myrstruktur), site (Norw. myrelement), synsite (Norw.
myrelementsamling), complex (Norw. myrkompleks). Masing (1984) added a regional level; his five levels being named: microform, site (association complex), complex, system and region. The following standard concepts are here proposed: mire feature, mire site, mire massif, mire system, mire region (nanotope, microtope, mesotope, macrotope, supertope).
Regional variation in Norway The variation between different parts of Norway when it comes to landscapes, types of ecosystems, plant and animal life is striking and can mainly be explained by the large differences in abiotic conditions. The regional variation is a response to climate, and vegetation zones and vegetation sections are the two main types of regional variation that have been distinguished and mapped (Moen 1999).
The vegetation zones display variations from south to north and from lowland to upland, and are linked with the demands of the plants for warmth during the growing season. In the lowlands, it is the nemoral zone which predominates furthest south. If we stay at sea level and travel northwards, we meet the other zones one after the other, the boreonemoral, southern boreal, middle boreal, northern boreal and southern arctic (furthest north in Finnmark). In alpine areas, three zones are distinguished above the northern boreal zone, the low, middle and high alpine zones, thus giving a total of nine vegetation zones distinguished in Norway. In Svalbard, the middle arctic zone predominates in the central lowland areas, and the high arctic zone in the greater part of the islands.
The variation in the zonal vegetation in most parts of Norway is greatest where there are short distances from the lowlands to the mountains, such as in the counties of western Norway (e.g. Sogn & Fjordane). There, the boreonemoral and southern boreal zones are found at sea level, whereas all the zones from the boreonemoral to the high alpine are represented in the altitudinal direction.
The vegetation zones reach their highest altitude in southern Norway and decline towards the north. The upper boundary of the northern boreal zone forms the climatic forest limit. This limit reaches its highest altitude in the Jotunheimen mountains and drops from there in all directions. Towards the north, it reaches sea level in Finnmark; north of this limit is the southern arctic zone.
The vegetation sections display the variation between coast and inland (or west-east) and five sections are recognised in Norway. These are the highly oceanic (O3; often subdivided into winter-mild and humid subsections), markedly oceanic (O2), slightly oceanic (O1), indifferent (OC) and slightly continental (C1) sections. These sections are tied to differences from oceanic to continental climates.
Sogn & Fjordane and Sr-Trndelag are the only counties where all five vegetation sections are represented, although the slightly continental section is only just present. The other counties along the coast from Hordaland in the south to Troms have four sections. Most of the remaining counties have three vegetation sections represented.
Vegetation ecological regions are obtained by combining vegetation zones and sections. Altogether 36 such regions are defined in Norway; see Figure 1. If the three alpine zones and the southern arctic zone are combined into one zone, Norway has 26 ecological regions (Moen 1999). Sogn & Fjordane is the county with the largest regional variation, 22 of the 26 regions occurring there.
Mire regions. The mire regions should be defined on the basis of variations in hydromorphological mire types and the plant cover of the mires. The regions are a response to variations in the climate, combining the zonal and sectional variations described earlier. Mire zones and sections were mapped by Eurola & Vorren (1980) in north Norway; by kland (1990) in southeast. Norway is separated into six main mire regions in Figure 2.
Mire types The Norwegian plan for mire reserves has used a detailed classification system throughout Norway in which mire types (i.e. hydromorphologically characterised mire massifs) are defined (Moen & Singsaas 1994). A revised system is presented in Table 1 that includes the subclassification of minerotrophic mires made by Succow & Joosten (2001). The hydromorphological mire types are based on the external shape of the mires and the hydrology. Five groups of mire types and 21 individual mire types have been distinguished (Table 1 and Fig. 3). Each of the types may be further subdivided into subtypes on the basis of differences in surface features, degree of slope, etc. Many of these mire types and subtypes (e.g. concentric raised bogs and palsa mires) are easily recogFigure 2. Mire regions in Norway based on the distribution of hydromorphological mire types, vegetation and flora on the mires (after Moen 1994).
nised and mapped by studying aerial photographs. A great diversity of hydromorphological mire types is found in Norway, embracing almost every known type of mire (Gore 1983).
Raised bogs (group A) are defined sensu stricto, i.e. the bog massifs are distinctly domed. The four first-mentioned types usually have a distinct marginal forest and a lagg. Concentrically raised bogs have circular features on their surface; they are rare in Norway, but are found in the lowlands (boreonemoral vegetation zone) of south-eastern Norway. Eccentrically raised bogs (the highest point close to one side, with regular, not circular features) and plateau raised bogs are mainly found in the lowlands (in the nemoral, boreonemoral and southern boreal zones), outside the most oceanic areas. Ridge raised bogs occur in oceanic areas in the southern and middle boreal zones. Atlantic raised bogs generally have several domes in a mire landscape where it is often difficult to determine boundaries between raised bogs, blanket bogs and other types of mire.
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