Artikkelit kirjoittajalta Pekka Pakarinen

Relatively low Hg concentrations are reported from Finnish collections of Sphagnum fuscum (21—63 ppb) and Cladonia sylvatica (9—101 ppb). While the difference in concentrations was not significant between Sphagnum and Cladonia, much higher Hg levels (176—495 ppb) were found in the corticolous lichen Hypogymnia physodes.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Häsänen, Sähköposti: ei.tietoa@nn.oo

The relationships between 32 peatland and forest vegetation types described from southern Finland were studied by different multivariate techniques. The material included regional averages (by Kalela 1977) of the following forest types (reference numbers, cf. Figs. 1-3, mentioned in parentheses): (1-2) CT, Calluna type, (3-7) YT, Vaccinium vitis-idaea type, (8-13) MT, Vaccinium myrtillus type, (14-19) OMT, Oxalis - Vaccinium myrtillus type, (20) Pyrola type, (21) OT= OMaT, Oxalis-Maianthemum type, (22) FT, Filices type (for characterization of vegetation, see Kujala 1961, Kalliola 1973). The following forested mire types were included in this study (described by Eurola 1962, cf. also Heikurainen & Pakarinen 1982): (23-26) IR, low-shrub pine bogs, (27-28) KR, spruce-pine swamps, (29-31) VK, ordinary spruce swamps, and (32) herbrich hardwood-spruce swamps. Mean percentage cover of bottom and field layer species was used in numerical analyses. A classification (Fig. 1) resulting from the agglomerative hierarchic clustering (Pritchard & Anderson 1971, Pakarinen 1976) shows four major groups: (A) dry heath forests - CT, VT, (B) mesic heath forests - MT, OMT, (C) spruce mires and herbrich forests, and (D) pine mires. Association analysis based on the presence-absence data (information-analytical method of Podani 1979) indicates that Luzula pilosa is primarily restricted to the upland (non-peaty) forests in the study area, and the reindeer lichen Cladonia stelloris (= C. alpestris) is limited in its occurrence to dry heath forests (Fig. 2); on the other hand Aegopodium podagraria and Anemone nemorosa appear to be differential species of herbrich forests. One should note, however, that the species mentioned are not constant in the primary material composed of site type means (not original sample plots). Therefore it is suggested that a threshold frequency go should be applied when developing identification keys to community types on the basis of individual species. An alternative approach, use of eigenvector methods (factor analysis, PCA, reciprocal averaging) is also briefly discussed in the paper (cf. Pakarinen 1979). Polar ordination (Bray-Curtis ordination, Fig. 3) based on percentage similarities (Jalas 1962, Gauch 1973) illustrates two major gradients in the study material: degree of paludification (x-axis), and trophic status (y-axis). While the material discussed in this paper represents the major types of mineral soil and peatland forests in their natural state in S Finland, description of different paludified forest types (with peat layer less than 30 cm) would complement the ordination diagrams. Much further research is still needed to elucidate the vegetational changes caused by nowadays common forestry practices, such as clear-cutting, peatland drainage, fertilization, etc.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo

Chemical analyses of anaerobic ombrotrophic Sphagnum peats are presented from four southern Finnish raised bogs. Some characteristics of the study sites and samples are outlined in Table 1. Ranking of the elemental concentrations in Table 2 indicates that among the "trace metals", iron (380 ppm = 0.38 mg/g of dry peat) shows a greater mean concentration in deep ombrotrophic peat layers than the "macronutrients"" phosphorus (160 ppm) and potassium (100 ppm). The lowest averages were found for zinc (8.5 ppm), lead (6.0 ppm), manganese (5.7 ppm) and copper (1.3 ppm). Estimates of long-term accumulation rates of elements in peat (Table 2) are based on volume samples from radiocarbon or pollen-dated profiles (cf. Tolonen 1971, 1977). The average rate of nitrogen accumulation (3.6 kg ha-1 yr-1) appears to be somewhat lower than the corresponding values from Denmark (Jörgensen 1927), Sweden (Mattson & Koutler-Andersson 1955) and Germany (Aletsee 1967). A tentative comparison to watershed studies (Verry 1975, Kauppi 1979) suggests that roughly equal amounts of phosphorus are accumulated by ombrotrophic peat and lost by runoff waters, while in the case of nitrogen the retention by peat is relatively greater. The mean rate of past peat accumulation in the study material (50 g m-2 yr-1, cf. Table 1) is approximately 1/4 of the current mean annual production of Sphagnum fuscum (195 g m-2 yr-1, cf. Pakarinen 1978a) in the same area. A similar comparison of the past accumulation rates of chemical elements (Table 2) with the current retention (consumption) rates by the living moss layer (Pakarinen 1978a,b) gives the following order of elements (peat/moss % ratio in parentheses): N(26.4) > Mg(16.7) > Fe(14.5) > Ca(14.4) > P(11.9) > Zn(8.1) > Pb(7.2) > Cu(5.0) > Mn(0.8) > K(0.6). This comparison suggests that manganese and potassium are to a great extent depleted from peat (by recycling or leaching), while nitrogen is accumulated at about the same relative rate as organic matter. The relatively low percentage values of some elements (Zn, Pb, Cu) probably indicate an increase in atmospheric metal deposition in this century (cf. Aaby & Jacobsen 1979). Detailed budget calculations may not be possible, because no direct information is available on the atmospheric fallout or on the leaching rates 1000 or 2000 years ago. In any case it appears that on annual basis the past accumulation rates of chemical elements (exc. N) in ombrotrophic bogs are quite small. This study has been supported by the Natural Science Research Council, Academy of Finland (macronutrients) and by the Nessling Foundation (trace elements). "

• Pakarinen, Sähköposti: ei.tietoa@nn.oo

Four ombrotrophic Sphagnum fuscum peat profiles (0—50 cm) were analyzed for total sulphur. The study sites include two bogs from southern Finland (Munasuo and Suurisuo, 60—61 °N) plus two bogs from northern Finland (Jänkävuopaja and Ah-venjärvenvuoma, 67°N). Sulphur was determined gravimetrically with BaSO4- method (Horwitz 1965). Sulphur concentrations and their vertical distributions are indicated in Figs. 2—3. In the top layer (0—20 cm) the S content is low, between 0.5 and 1.0 mg/g dry weight. In the southern Finnish sites, higher values were found near the transition from aerobic to anaerobic conditions: in Munasuo at ca. 30 cm level and in Suurisuo at 45—50 cm level (Fig. 2). In northern Finnish sites, especially in Ahvenjärvenvuoma, the S concentrations of Sphagnum peat seem to be related to the dry volume weight (degree of humification) (Fig. 3), but further material will be needed to establish the commonness of "enrichment layer" of sulphur in these peats. The sulphur amounts per square meter for 0—20 cm and 20—50 cm layers are indicated in Table 1. In the 0—20 cm layer, which was in all sites weakly humified, it was possible to apply the moss dating method (Pakarinen & Tolonen 1977). Using the ages obtained for the top 20 cm layer (23 to 68 years), the annual accumulation rates of sulphur were found to range from 59 to 163 mg/m2 (Table 1). The estimated atmospheric sulphur deposition rates in the corresponding areas varied from 280 to 650 mg/m2 (according to data of Buch 1960, Haapala 1977, Järvi-nen 1978). Thus the retention % of S was estimated at 19 to 25 for the surface peat layer (0—20 cm), and it was concluded that the main part of the atmospheric S deposition is leached to deeper peat layers or more probably outside the mire ecosystem.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo

Concentrations of five metals — Mn, Fe, Zn, Pb, Cu — were determined in samples of a common dwarf shrub, Ledum palustre, collected from seven S. Finnish raised bogs (between 60 and 61 °N) in September-October 1977. The analyses were made separately for the twigs (stems) of last four years and for the leaves of last two years. The material was dry-ashed at 450°C, dissolved in cone. HC1 on hot plate, filtered and diluted to 50 ml with deionized H2O which solution was finally analyzed with an atomic absorption spectrophotometer (Varian Techtron AA-1200). Ash percentage and manganese showed identical distributions with maximum values on second-year leaves and a decrease of concentrations in stems with age (Figs. 2 and 3). Also the concentrations of Fe, Zn and Pb (but not Cu) increased from first- to second-year leaves. In stems, there was a fairly regular increase in Fe and Pb levels from first to fourth year, while Zn and Cu changed little or decreased with age (Fig. 3). Average concentrations in Ledum (leaves + stems of last two years) were compared with those in the substrate (Sphagnum fuscum peat). The results (Table 1) showed that manganese was the most favoured metal and iron the least. The relative enrichment of metals from the peat substrate to Ledum followed the order Mn >Cu >Zn >Pb >Fe.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Mäkinen, Sähköposti: ei.tietoa@nn.oo

Sphagnum f uscum hummocks have been studied in a southern Finnish ombrotrophic bog in Kuhmoinen (62°N). The annual increments of Sphagnum have been distinguished by means of cyclic pigmentation (cf. Bellamy & Rieley 1967), branching pattern (cf. Maimer 1962) and changes in growth-direction due to pressure of snow-cover. These «innate markers» (cf. Clymo 1970) can be found in scattered individuals of S. fuscum particularly in the less compact parts of hummocks. In addition, Polytrichum affine (= strictum) growing mixed with Sphagnum was utilised as a re-ference mark for the increments (cf. Long-ton 1972). With the combination of these methods it was possible to date a Sphagnum fuscum hummoc down to ca. 50 years old layers (Fig. 3). In the same site, volume samples were taken and analyzed in a vertical profile (Fig 4). It appears that the growth rate of surface peat decreases with depth (maximum gradient in the top 10 cm layer) indicating a progress of humification process and autocompaction (Aaby & Tauber 1975). It is concluded that the pine method used earlier (Borggreve 1889, Saarinen 1933) gives not comparable values of growth-rate of surface peat particularly if pines of different age are used. It is also suggested that the long-term growth curves of peat accumulation (cf. Tolonen 1973, Zurek 1976) should not be extended to the surface but instead to the level where compaction process has terminated, i.e. often at 30—50 cm below surface. The «moss dating method» was also applied to Sphagnum fuscum hummocks in several other bogs in southern Finland. The preliminary results indicate a considerable variability in the vertical distribution of growth rates, even within one hummock, but the overall picture is similar as in Fig. 4. From the profile dated with moss method the peat samples were also analysed for cesium-137 and potassium. As illustrated by Fig. 5, 137Cs has become enriched to the Sphagnum layer (as also potassium) supposedly by an active uptake mechanism. Thus the peak of 137Cs fallout in 1963 (see Fig. 5) cannot be used as a dating method in peat profiles in contrast to lake sediments (cf. Pennington et al. 1973).

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo

This paper presents the results of heavy metal (trace element) analyses of plant samples collected from three undrained ombrotrophic bogs in southern Finland (60—61°N, Fig. 1). The species studied included three mosses — Sphagnum fuscum, S. balticum, S. majus — and four lichens — Cladonia stellaris (= C. alpestris), C. arbuscula, C. rangiferina, Hypogymnia (= Parmelia) physodes. Also the needles of stunted bog pines Pinus silvestris) were collected and separated according to age (current vs. 1—2-year-old needles). Collective samples (5—10 replicates) consisting only of the living top part were taken (lichens 4—5 cm, hollow mosses 3—6 cm, hummock mosses 2 cm). The samples were dry-ashed at + 500° C, then dissolved with cone, hydrochloric acid, diluted with distilled water and analysed for metals with Varian Techtron AA-1200 atomic absorption spectrophotometer at Botany Dept., University of Helsinki. Duplicate samples were also digested directly with HNO3 and HCl for control. The results of the former method are presented in Figs. 2—4 on oven-dry ( + 70°C) weight basis. Among bryophytes, the contents of Pb, Zn and Mn were in all cases highest in hummock species Sphagnum fuscum and lowest in the wet-hollow species S. majus. Among lichen species, the concentrations of lead and zinc decrease in the order: Hypogymnia physodes (epiphyte) > Cladonia rangiferina > C. stellaris, C. arbuscula. In Pinus the needles from the current year contain less metals than the needles from previous years. A comparison of different plant groups depends upon the element analysed (see Figs. 2—4). Mn content is highest in pine needles followed by Sphagnum fuscum and lowest in lichens and hollow mosses. Zn content is greatest in the epiphytic lichen Hypogymnia followed by pine needles, then by bog mosses and reindeer lichens. As opposed to zinc, the content of lead is lowest in pine needles which fact suggests a low absorption capacity of atmospheric heavy metals by pine needles. On the other hand, zinc and manganese seem to be actively translocated by pine. Consequently, needle analysis does not appear to be an appropriate method for monitoring the deposition of heavy metals. Both lichens and mosses (with the exception of hollow species), however, seem to be efficient accumulators of zinc and lead at least. If the annual primary production of mosses can be determined, it becomes possible also to estimate the deposition rate per surface area of some heavy metals.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Mäkinen, Sähköposti: ei.tietoa@nn.oo

Observations are presented from an excursion made by the authors in 1973 to the peatlands in the vicinity of Heart Lake, located 40 to 50 km west of the city of Hay River in the Mackenzie District, N.W.T. Two mire complex types were distinguished, namely aapa-mires and raised bogs. Apparently referring to similar peat-land types, Zoltai et al. (1974) have used the terms «string fens» and «peat plateaus», respectively. The extensive aapa-mires of the study area (southwest of Great Slave Lake) have a reticulate structure, i.e. the strings (= peat ridges) form a continuous net which alternates with wet flarks (= rimpis). It is noticed that aapa-mires with similar surface pattern have been described from N. Finland just south of the palsa mire zone (Ruuhijärvi 1960). Due to the calcareous nature of bedrock, the aapa-mires in the Heart Lake area studied are strongly minerotrophic (eutrophic). Particularly the moss species, but also many vascular plants allow a comparison to the mire types in northern Finland; such homologues are for example the «Rimpibraunmoore», «Campylium stellatum -Braunmoore» and «Braunmoor-Reisermoore» described by Ruuhijärvi (1960). Special attention was paid to the plant species indicating a transition from minerotrophic (aapa-mire) to ombrotrophic (raised-bog) conditions. «Fen windows» or minerotrophic hollows (cf. Sjörs 1963) in raised-bog were characterized by Carex aquatilis and Sphagnum riparium. In the marginal parts of the raised bog, several sedge species, Equisetum spp., Betula glandulosa and Larix laricina were the last remaining indicators of minerotrophic effect. Tamarack (Larix) is relatively easy to identify also from aerial photographs and therefore it could probably be used in mapping extensively bogs and fens in the northern boreal (or subarctic) zone. Trichophorum caespitosum, Drosera anglica and Carex limosa were commonly found in the minerotrophic peatlands visited, but these species were lacking in ombrotrophic sites with comparable water level. In less continental climate — e.g. in Ontario (Sjörs 1963) or in Finland — these three species are, however, frequent components of ombrotrophic bog vegetation. It is assumed that the low nutrient content of mire water in northern continental raised bogs restricts the occurrence of many species to minerotrophic sites. The vegetation of treeless bogs in the Heart Lake area will be treated in detail in a future publication (Talbot & Pakarinen, in prep.).

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Talbot, Sähköposti: ei.tietoa@nn.oo

The article deals with the oligotrophic-eutrophic and ombrotrophic-minerotrophic gradients in peatlands. The use of these terms in Finland, Sweden, the Soviet Union, Central Europe, Canada and England is briefly reviewed. In the case of peatlands, the concept of eutrophy, as defined by most authors, implies high pH, high levels of calcium and nitrogen, but its relationship to phosphorus and potassium levels (which greatly affect the tree growth and productivity) is not so clear. It is important to make a distinction between trophic series related: (1) to primary production, and (2) to pH (Ca)gradient. For the former, the terms oli-go-, meso- and eutrophic seem appropriate (as in the case of limnology); for the latter, the following four categories could be used: ombrotrophic, weakly-, moderately- and strongly minerotrophic. Apparently some authors have also used the terms soligenic or rheotrop-hic as synonyms for minerotrofic.

• Pakarinen, Sähköposti: ei.tietoa@nn.oo

• Pakarinen, Sähköposti: ei.tietoa@nn.oo

• Pakarinen, Sähköposti: ei.tietoa@nn.oo

• Pakarinen, Sähköposti: ei.tietoa@nn.oo
• Tolonen, Sähköposti: ei.tietoa@nn.oo