Ecological, topographic and successional patterns across wetlands in a rugged land uplift coast in Nyby, northern Finland URN:NBN:fi:tsv-oa51315 DOI: 10.11143/51315 Ecological, topographic and successional patterns across wetlands in a rugged land uplift coast in Nyby, northern Finland JARMO LAITINEN, JARI OKSANEN, TUIJA MALINIEMI, EERO KAAKINEN, KAISU AAPALA AND SAKARI REHELL Laitinen, Jarmo, Jari Oksanen, Tuija Maliniemi, Eero Kaakinen, Kaisu Aapala & Sakari Rehell (2016). Ecological, topographic and successional patterns across wetlands in a rugged land uplift coast in Nyby, northern Finland. Fennia 194: 1, 89–116. ISSN 1798-5617. We studied 45 mid-boreal wetlands in a rugged land uplift coast with a thin cover of till. Wetlands ranged from 1 to 53 m a.s.l. and were of highly various sizes. Our aims were to examine, if vegetation types are valid in comparing wetlands, what kind of ecological major pattern the vegetation type composi- tion of wetlands shows and how vegetation types distribute across altitudes. On those ground we discuss the wetland succession of the study area. We used the Finnish mire site types as vegetation types. Mire site types could be used for an ecological classification and ordination of the wetlands. As was expected, the major gradient consisted of the transition from mire margin (swamp) to expanse. The distribution of the Major Vegetational Wetland Groups (MVWG) responded to a general water-flow pattern in the landscape. Partly different peatland suc- cession sequences occur in areas with small mire basins and in areas with larger mire basins with evolving mire complexes. Sequences of small wetlands and those of mire complexes follow the same trajectory only as far as the major gra- dient is considered while they differ with regard to the vegetation type composi- tion of locally rare vegetation types and with regard to peatland morphology. Trajectories of mire complexes at catchment divides differ from those at catch- ment centers where the waters in the landscape tend to gather. Peatland forms of aapa mires experience a change reaching altitudes of 30–50 m a.s.l. Small bog complexes at catchment divides reach a stage of an unpatterned Sphagnum fuscum bog in the study area. Mature mixed complexes with aapa-mire parts and patterned sloping-bog parts only occur at altitudes higher than 60 m a.s.l. Peculiarities in the succession of the wetlands of Nyby, which include the pres- ence of separate incomplete successional sequences in the same area, are main- ly caused by the peculiar topography with various sub-areas and with an abun- dance of rock outcrops. Keywords: Gulf of Bothnia, vegetation survey, cluster analysis, aapa mires, mire site types, peatland forms Jarmo Laitinen, Jari Oksanen & Tuija Maliniemi, University of Oulu, Department of Ecology, PO Box 3000, FIN 90014, Finland. E-mail: jarmo.laitinen@oulu.fi, jari. oksanen@oulu.fi, tuija.maliniemi@oulu.fi Eero Kaakinen, Kurkelantie 1 D 38 Oulu, Finland. E-mail: eero.kaakinen@dnain- ternet.net Kaisu Aapala, Finnish Environment Institute, PO Box 140, 00251, Helsinki, Fin- land. E-mail: kaisu.aapala@ymparisto.fi Sakari Rehell, Metsähallitus, PO Box 81, Veteraanikatu 5, FI 90101 Oulu, Finland. E-mail: sakari.rehell@metsa.fi Introduction Boreal landscape is characterized by coniferous forests and peatlands. From south- to mid-boreal (Hämet-Ahti 1981) lowlands around the northern part of the Baltic Sea, the Gulf of Bothnia, new landscape is emerging from the sea as a result of the glacio-isostatic land uplift. Associated primary © 2016 by the author. This open access ar- ticle is licensed under a Creative Com- mons Attribution 4.0 International License. 90 FENNIA 194: 1 (2016)Jarmo Laitinen et al. succession on uplands leads to various types of forests (Svensson & Jeglum 2000) and succession on depressions to ponds and various types of peatlands (Brandt 1948; Rehell & Heikkilä 2009). The coasts of the Gulf of Bothnia in the glaciated shield area differ topographically. In general terms, the western (Swedish) side of the Gulf of Bothnia has a more rugged coast with a steeper general gradient of the ground surface near the sea level and the eastern (Finnish) side has a gen- tler gradient from the seaside far to the inland (Seppälä 2005). Bedrock topography ultimately determines the major lines for landforms, includ- ing the size and proportion of depressions occu- pied by wetlands in the emerging landscape, and topographically different coasts provide different prerequisites for wetland succession. This has not been much stressed in botanical peatland studies in general. The bedrock topography has a special prominent role for the landforms of Nyby study area with a thin and discontinuous cover of till (Alalammi 1990). Recent investigations for con- servation purposes in Finland (Kaakinen et al. 2008) and partly old work (Aario 1932) concen- trate on the vegetation and succession of mires in median to large bedrock basins with evolving mire complexes, while the vegetation and the succession of mires in small depressions are partly ignored (see Lindholm 2013a). This implies that possible differences between the succession of small wetlands among rugged topography and the succession of wetlands into mire complexes among flatter topography are not specifically stud- ied. Classic works on boreal mires on the land uplift coast provide a basic information about the historic and morphologic characteristics of a ma- ture ombrotrophic mire complex type in a south- boreal area (Aario 1932), about vegetation stages along the succession of small swamps to fens and to bogs in a south-boreal area (Brandt 1948) and about the plant communities, gradients and ecol- ogy of low-altitude mires in a mid-boreal coastal rich fen area (Elveland 1976). Recent research on mire succession in northern Finnish coast, on the one hand, aims to study specific patterns for the relationships of the vegetation and topography at different scales (Rehell & Heikkilä 2009; Rehell et al. 2012a, 2012b), and research of another kind, on the other hand, focuses on general functioning of boreal successional mire ecosystems, especial- ly applying research on gas exchange (e.g. Lep- pälä 2011). The study of Tuittila et al. (2013) sug- gests using spatial age transects as a model of vertical peatland formation. Similarity of certain degree was found between the current spatial vegetation gradient in peatland succession and the vertical temporal vegetation gradient observed in the oldest peatland in the same study area. Walker et al. (2010), however, warn of a false use of chronosequences stating that they are often used inappropriately, leading to false conclusions about ecological patterns and processes. Mid-boreal wetlands of Nyby in northern Fin- land provide a group of mineral wetlands (small reed marshes) and peatlands (small mires and mire complexes, mainly aapa mires) on the northeast coast of the Gulf of Bothnia, where a small area topographically resembles a typical (more rugged) Swedish coast more than a typical Finnish coast. Small wetlands among rugged bedrock topography with a thin and discontinuous cover of till near the sea and some larger wetlands among slightly flatter bedrock topography in the inland provide a suita- ble object for a survey on the variety of wetlands. We consider the mire succession in terms of the change in the vegetation type composition and peatland topography, and hypothesize that the suc- cession of small mires and aapa mires differ in those respects. We additionally suppose that the succession of peatlands building up mire complex- es near catchment divides is different from the suc- cession of peatlands at catchment centers, in which the rates of the water flow and the supply of nutri- ents are higher than at catchment peripheries (Ivanov 1981; Seppä 2002). In this study we have several aims. First, are the Finnish mire vegetation types valid as data for analyzing differences be- tween wetlands generally and for successional wetlands on the land uplift coast specifically. Sec- ond, we approach the ecological–hydrological pat- tern across Nyby wetlands asking (a) what is the major vegetation (type) gradient for the whole group of studied Nyby wetlands, (b) do the major vegetational wetland groups relate to the altitude gradient and to wetland sizes, and (c) do they relate to a landscape-level water-flow pattern. Third, we ask how vegetation types with different climatic fo- cus are distributed along the altitude gradient and across local topographic groups of wetlands. Fourth, we discuss the peatland succession of Nyby and boreal regions generally asking (a) does the succession of wetlands in small bedrock basins dif- fer, and how, from that of mires in larger bedrock basins, and (b) what kind of trajectories occur in the succession of mire complexes and what are the ultimate causes for those trajectories. FENNIA 194: 1 (2016) 91Ecological, topographic and successional patterns Study area and field work The study area is located in the mid-boreal (Hämet- Ahti 1981) lowlands of Fennoscandia, ranging from the seaside to the altitude of about 55 m a.s.l. (Fig. 1). Wetlands of Nyby, as called in this re- search, refer to wetlands of highly various sizes (0.1–185 ha) on the northeast coast of the Bothni- an Bay. Climatic conditions are practically con- stant across the whole study area. As counted from an interpolated European climatic data (Haylock et al. 2008), the mean annual temperature is 1–4 °C, average 2.5 °C, and the mean annual precipi- tation is 400–700 mm, average 500 mm, for Nyby area (1980–2010). The basal gneiss area runs to the seaside around Nyby (Alalammi 1990). Gla- cioisostatic land uplift ranges from 7 to 8 mm in a year (Taipale & Saarnisto 1991). The study area situates below the highest Holocene coastline. Nyby area differs from the surroundings in having rock outcrops (bedrock terrain, Alalammi 1990) and varying topography with relatively small mire basins. The 2.5 km wide belt at the seaside north of Nyby is most sloping and forms a threshold in the topography. Moreover, the mire basins are the smallest of all within the study area. There is only one short stretch of an esker in the area (Alalammi 1990). Relatively high lowland altitudes, the level of 50–60 m a.s.l., are reached in a horizontal dis- tance shorter than in any other district in the Finn- ish coasts. The study area belongs to the southern aapa mire zone (Ruuhijärvi & Hosiaisluoma 1988). Peatlands cover 40% of the land area, and only about one fourth of the peatland is drained, while in the surroundings the proportion of drained peat- lands is much larger. Fig. 1. The location of study area in Fin- land and studied wetlands, which are indicated with grey on the map: 1–4 Ma- java; 5–8 and 14 Ruonalampi; 9–11 Ru- ukinlahti; 12 Kellarioja; 13 Korkiansal- mi; 15 Lastenkallio; 16 Ruonajärvi; 17– 18 Ämmäjärvi; 19–20 Pikkuniitty; 21 northwest of Mustikkakangas; 22 Äm- mäjärvi-Hevosjärvi; 23 northwest of Ämmäjärvi; 24 Lapinjärvi; 25 Lapinjär- vi-Mustikkakangas; 26–28 Hoikkalam- pi-Koiralampi; 29 Soidinräme; 30 west of Sulajärvi; 31 Parviaisenkangas; 32–33 southeast of Mustikkakangas; 34 Jäkäläsuo; 35 Ulkusuo; 36 Honkisuo; 37 Käärmesuo; 38 east of Ulkusuo; 39 Anti- naapa; 40 Antinjärvenaapa-Pahasuo; 41 west of Lakkasuo; 42 Lakkasuo; 43 Lamminniitty; 44 Tukalasuo; and 45 Mustanlammenaapa. Contour lines are at the intervals of 10 m. 92 FENNIA 194: 1 (2016)Jarmo Laitinen et al. We selected 45 study localities from about 70 pristine or nearly pristine wetlands of the study area for a vegetation survey in order to investigate a large number of wetlands in a short time (see Locky et al. 2005). Map contour lines were used for selecting belts with 5 and 13 localities repre- senting altitudes 0–2.5, 2.5–5, 5–10, 10–20, 20– 40 and 40–60 m a.s.l. The sampled belts repre- sented smaller altitude ranges at lower altitudes following the result of Brandt (1948) with narrower belts nearer the seaside. The largest mires for each belt and the variation from mires representing lo- cations in the central parts of catchment areas and at the catchment divides were included. We listed the vegetation types a priori (Eurola et al. 1995) for each wetland using a limited time. About one day was used for the field survey of large mire complexes, and a shorter time was used for small mires near the coast. To achieve a list rep- resentative enough for each wetland, the route of walking was chosen across various topographic units of mires visible on air photos (Laitinen et al. 2005, 2007). Observed communities were as- signed to vegetation types in the field, no vegeta- tion survey plots were used for community-to-type assignments (cf. Oliver et al. 2013). For minimiz- ing subjective variability in the assignments, all the study localities were surveyed by the same author. In the Sphagnum fuscum bog -case, some assign- ments were based on air photo interpretation. Ob- served minimum surface areas varied considerably according to typical surface areas described for mire site types (Ruuhijärvi 1960; Eurola 1962), with the smallest observed areas ranging from 1 to 100 m² (micro sites), mostly constituting areas larger than 100 m² (even several hectares etc.). Communities of different spatial scales (Gonzáles- Megías et al. 2007) were included and analyzed jointly in order to stress the overall variation be- tween wetlands, rather than to analyze the major variation based on large vegetation patterns only. The field survey was made 25.8.–1.10.2012. Material and basic concepts Peatland vegetation types The ecologically detailed Finnish mire site type classification (Ruuhijärvi 1960; Eurola 1962; Euro- la & Kaakinen 1978; Ruuhijärvi 1983; Eurola et al. 1984, 1995, 2015; Laine & Vasander 2005), which is a national vegetation classification for peatlands, was briefly analyzed by Pakarinen (1976) as well as Pakarinen and Ruuhijärvi (1978), and its history and current usage trends were critically discussed by Lindholm (2013b). In the present survey we use Finnish mire vegetation types as a data for a case study of 45 boreal mires of various sizes (0.1 to 185 ha) occupying altitudes from 1 to 53 m a.s.l. on a boreal land uplift coast, and interpret ecological differences between wetlands on the basis of the vegetation type data of each wetland. Six main mire vegetation units and the vegetation types in the Finnish typology are thought to form fixed points in a network of three major gradients (poor- rich, mire margin to expanse, mire surface level). In the present study, the type lists recorded in the field for each wetland were used to compare the studied wetlands in relation to those major gradients. Es- tablished type abbreviations and the types of Euro- la et al. (1995) were used, while the English de- scriptions are in Eurola et al. (1984) (cf. Ruuhijärvi 1983; Heikkilä et al. 2001). The poor-rich gradient (Rydin et al. 1999a) as used in the present study corresponds to the trophic gradient of Eurola et al. (1984, 1995, 2015) as follows: extremely poor (fen) corre- sponds to oligotrophic, moderately poor (fen) to mesotrophic, intermediate (fen) to meso-eutroph- ic and rich (fen) to eutrophic. Six main mire veg- etation units in the Finnish typology (Eurola & Kaakinen 1978; Eurola et al. 1984, 1995, 2015) represent a specification for the mire margin to expanse gradient of Sjörs (1948): spruce mires (Bruchmoore, Ruuhijärvi 1960; Eurola 1962), swamps (Sumpfmoore, Brandt 1948) and spring vegetation (spring fens, springs) represent mire margin vegetation, and treeless poor to intermedi- ate fens including treeless lawn and flark level bogs (Weissmoore, Ruuhijärvi 1960; Eurola 1962), rich fens (Braunmoore, Ruuhijärvi 1960; Eurola 1962) and hummock-level pine mires (Reiser- moore, Ruuhijärvi 1960; Eurola 1962) represent mire expanse vegetation. Treed fens are viewed as combination site types. Spruce mire influence (Eurola et al. 1984, 1995, 2015) (Bruchmoorig- keit, Ruuhijärvi 1960; Eurola 1962) refers to a spe- cies composition of mire margin vegetation partly transitional to boreal mesic heath forests (Picea abies, Carex globularis, Equisetum sylvaticum. Sphagnum girgensohnii etc.) or herb-rich forests. Swampy vegetation features (Eurola et al. 1984, 1995, 2015) (Sumpfigkeit, Ruuhijärvi 1960) refer to treeless or treed (Betula pubescens, Alnus sp., FENNIA 194: 1 (2016) 93Ecological, topographic and successional patterns Salix sp.) wetlands with species typical of shore habitats (Equisetum fluviatile, Potentilla palustris, Lysimachia thyrsiflora, Calliergon cordifolium, Sphagnum squarrosum, S. riparium etc.) (Eurola & Kaakinen 1978; Eurola et al. 1984, 1995, 2015). Vegetation features of springs and spring fens form the third form of mire margin vegetation indicat- ing groundwater influence (Eurola et al. 1984, 1995, 2015) (Quelligkeit, Ruuhijärvi 1960). Mire expanse vegetation is characterized by the lack of mire margin species of aforementioned three spe- cies groups. The third major mire vegetation gra- dient is the gradient along mires surface levels reflecting mean water table levels (Laitinen et al. 2008a). A division into a hummock level, an inter- mediate mire surface level (lawn) and a flark level (carpet and mud bottom) is used in Finland. We supplemented the list of vegetation units for the analysis data on three ecological/ successional grounds. Firstly, the group of Sphagnum compac- tum fens (cf. Ruuhijärvi 1960; Eurola et al. 1995) (OlScomN, MeScomN, OlScomNR, MeScomNR) was regarded as separate from corresponding Sphagnum papillosum fens (OlKaN, MeKaN, Ol- KaNR, MeKaNR), because the former represent vegetation with unstable water regimes, while the latter represent vegetation with stable water re- gimes (Havas 1961; Kaakinen et al. 2008; Laitinen et al. 2008a, 2008b). On the same grounds, rare mud bottom flark fens dominated by Rhynchos- pora fusca (MeRhyfusRuRiN, MeRhyfusRuRiLN) were handled separate from the rest of mud bot- tom flark fens (Laitinen et al. 2008a). Secondly, micro sites (from 1 to 100 m2) of intermediate fens, rich fens and spring fens were included in the analysis in order to stress the overall vegetation variation rather than hold to a group of communi- ties with large surface areas only: intermediate Loeskypnum badium fen (LoebadLN) (Drepano- cladus badius Braunmoor Weissmoor, Ruuhijärvi 1960, meso-eutrophic Bryales fen, Eurola et al. 1995), rich Campylium stellatum fen (CaL), rich Scorpidium revolvens flark fen (RevRiL) and Warn- storfia sarmentosa spring fen (WarnsarmLäN) (mesotrophic spring fen, Eurola et al. 1995). The latter represents a poorly documented micro site occurring in the starting points of narrow soaks with sparsely growing Carex rostrata and Eriopho- rum angustifolium occurring as dominants in the field layer and with the bottom layer being charac- terized by Warnstorfia sarmentosa with mud bot- tom (cf. Laitinen et al. 2011). Thirdly, five local communities from low altitudes (2 to 10 m a.s.l.) were included in the analysis, because the Finnish mire site type classification does not specifically describe the unestablished plant communities of the land uplift coast. Extremely poor swampy tall sedge fen (OlLuSN) was a Carex rostrata–Carex aquatilis–Sphagnum riparium community in small depressions in the seaside birch forests. Alnus in- cana swamp (HaLu) (Kaakinen et al. 2008) is a poorly documented local community at the coast of the Bothnian Bay. Minerotrophic Sphagnum fus- cum mires (MiRaR) were small-sized communities with scattered minerotrophic species (e.g. Erioho- rum angustifolium) on a uniform Sphagnum fus- cum surface with a discontinuous dwarf-scrub cover (see Elveland 1976). Swampy sedge fen with flark character (LuRiSN) was a local community in a young mire (17, Fig. 1) with flark species (Carex chordorrhica, Carex limosa, Menyanthes trifoliata) dominating in the field layer but with a uniform Sphagnum layer with species indicating surface water influence as dominants (Sphagnum flexuo- sum or Sphagnum obtusum and Sphagnum ripari- um). Moderately poor swampy sedge fen with flark character (MeLuRiSN) was a local community in a developing young aapa mire central basin (21, Fig. 1) with an Equisetum fluviatile–Carex chordorrhi- za–Menyanthes trifoliata–Utricularia intermedia– Warnstorfia procera–Cinclidium subrotundum stand. At higher altitudes the rich pine fen (LR) in mire 35 (22 m a.s.l.) represented an unusual com- munity with a Carex lasiocarpa–Equisetum fluvia- tile–Carex chordorrhiza–Tomentypnum nitens stand with Sphagnum papillosum hummocks. We additionally treated Phragmites australis stands as marshes according to Keddy (2000) (cf. Brandt 1948; Eurola et al. 1995) in order to make a deli- cate difference between treeless swamps resem- bling thin-peated mires and treeless marshes more resembling mineral wetlands. One small Phrag- mites australis stand was further away from the seaside (4 m a.s.l.), and had an evident peat layer. The distinction of marshes from swamps was sup- ported by the ordination. Climatic distribution features for vegetation types We applied three scales for the discussion about the climatic distribution patterns of vegetation types related to successional altitudes, including a global scale, a scale across nemoral (temperate) and boreal zones, and a pattern on a minor scale 94 FENNIA 194: 1 (2016)Jarmo Laitinen et al. across boreal subzones. For a global scale, the eco- climatic peatland model of Eurola & Kaakinen (1979) provides a tool for scrutinizing the distribu- tions of Finnish main mire vegetation units global- ly. Major Fennoscandian distribution of various vegetation across nemoral vs. boreal vegetation zones are visible in Scandinavia (Moen 1999; Ry- din et al. 1999a), while the Finnish distributions of single (national) vegetation types show patterns on a minor scale across boreal subzones (hemiboreal, south-boreal, mid-boreal, north-boreal). Current distributional focuses of the national vegetation types were recently specified in order to evaluate their state of being threatened (Kaakinen et al. 2008); present distributions still weakly reflect cli- matic patterns in spite of the selective cutting down of the habitats (vegetation types) caused by man. Peatland forms The successional stage of the central basins of aapa mires was roughly evaluated on the basis of morphologic features. The morphologic pattern of mire complexes was interpreted from air photos (not shown), and the major morphologic units of aapa mires according to Laitinen et al. (2007) were used. Peatland locations in catchment areas The concepts of peripheral vs. central parts of catchment areas were used to compare the loca- tions of wetlands in relation to landscape-level water-flow conditions. The periphery refers to catchment divides but additionally to areas near it, while the center refers to areas where the waters in the landscape tend to gather. It is question of rela- tive altitudes between close by bedrock basins rather than of precise boundaries of actual catch- ment areas of different ranks. Accordingly we showed the relative altitudes of close by wetlands (centers vs. peripheries of catchment areas) with maps having contours using no boundaries of catchment areas, which are highly complicated in the area near the coast. Peatland surface areas and altitudes Surface areas (hectares) and altitudes (m a.s.l.) of wetlands were determined for grouping wetlands on topographic grounds. Study localities were de- marcated on aerial photographs along the limits of mires and mineral soil areas by using topographi- cal maps as the aid for air photo interpretation. When mires formed connected networks, the mire complexes were demarcated by cutting them from the narrowest possible sites, also roads and limits of ditched areas were used. Small ditched parts situated between pristine mire parts were included only exceptionally. Small parts of brook sides in demarcated areas were not visited. In locality 39, the northern main part was taken with. In locality 26, the survey included the north-western half of the mire complex. ArcMap 10.2.1 software was used for digitizing the studied mires to get precise surface areas of the mires. Digital elevation model (DEM) with a resolution of 2 x 2 meters and an accuracy of 0.3 meters was used for getting the mean altitude of the mires (m a.s.l.) (NLS 2010). Methods Vegetational classification and ordination of wetlands To show the major ecologic pattern across the group of wetlands of Nyby and the distribution pattern of vegetation types in a compressed form on topographic map, the wetlands with a present- absent vegetation type data were grouped into Major Vegetational Wetland Groups (MVWGs) with cluster analysis. Dissimilarities among wet- lands were assessed using Raup-Crick index (Chase et al. 2011; Legendre & Legendre 2012). This is a probabilistic index that can be used for analyzing co-occurrences among items of differ- ent frequencies. Average linkage method was used in the cluster analysis of dissimilarities (Leg- endre & Legendre 2012). The data were ordinated with non-metric multidimensional scaling (NMDS) that is a robust method that can handle probabilistic measures like the Raup-Crick index (Minchin 1987). The ordination diagrams were in- terpreted fitting direction vectors and smooth nonlinear response surfaces. All statistical analy- ses were performed in the R statistical environ- ment (R Core Team 2014), and vegan package (R Core Team 2014) for multivariate analysis. Topographic classification of wetlands To introduce the successional patterns for the dis- cussion section, we formed two Major Topograph- FENNIA 194: 1 (2016) 95Ecological, topographic and successional patterns ic Wetland Groups (MTWGs) on the basis of the wetland size, and a set of Local Wetland Types (LWTs) on the basis of the wetland size, vegetation type composition and peatland morphology. Wet- lands close to each other were called Local Wet- land Groups (LGWs). The following abbreviations for wetland groups are used in this article: LWGs = Local Wetland Groups (A–E), MVWGs = Major Vegetational Wetland Groups (1–3), MTWGs = Major Topographic Wetland Groups (I–II) and LWTs = Local Wetland Types (1–10). Results Ecological pattern Three Major Wegetational Wetland Groups (MVWGs) (Fig. 2, 3, 4), (1) marshy mineral wet- land vegetation, (2) swampy mire vegetation and (3) mire expanse vegetation, formed with cluster analysis on the basis of the vegetation type com- position of the wetlands, introduced the major ecological pattern across the group of studied wet- lands (Fig. 5). The first group represents wetlands with marshy (Phragmites australis) vegetation in partly littoral zones near the seaside level. The sec- ond group represents mires with partly swampy mire vegetation at least in the central parts of the mire, and the third group represents mires with mire expanse vegetation prevailing and with only sporadically having swampy mire vegetation, be- fore all swampy Betula pubescens fen (LuNK). Sedge herb swamp (SRhLu) and Betula pubescens swamp (KoLu) confined to wetlands in MVWG 2, while vegetation types confining to wetland group 3 (mire expanse vegetation) were numerous in- cluding Carex globularis pine mire (PsR), dwarf shrub pine bog (IR), moderately poor Sphagnum papillosum tall-sedge fen (MeKaSN), extremely poor mud bottom flark fen (OlRuRiN) and practi- cally all the rich and intermediate fen types pre- sent in Nyby. Interpreted with the vegetation type composi- tion of the MVWGs and with the locations of them in the ordination, the major gradient in the mate- rial appeared in the transition from MVWG 2 to 3, and represented the mire margin to expanse gradi- ent with a diminishing of swampy vegetation fea- tures and an increase in mire expanse vegetation features. Group 1 with marshy vegetation near the seaside seemed to be the most separate group in relation to other groups according to the ordina- tion (Fig. 6). Major Vegetational Wetland Groups (MVWGs) broadly related to the altitude gradient (Fig. 6), while some wetlands of MVWG 3 (mire expanse Fig. 2. Wetland 4 at Majava close to the sea at 0.8 m a.s.l. The locality represents wetlands with marshy mineral wetland vegetation (MVWG 1): Phragmites australis dominates, and also small amounts of Myri- ca gale occur. Topographically the wetland represents small reed marshes (LWT 1) within the major group small wetlands of Nyby (MTWG I). The surroundings are seaside birch forests, partly seaside Salix thickets. Fig. 3. Wetland 9 at Ruukinlahti at 2 m a.s.l. The lo- cality represents wetlands with swampy mire vegeta- tion (MVWG 2): Potentilla palustris, Lysimachia thyrsi- flora and Sphagnum riparium indicate surface water influence (Sumpfigkeit). Topographically the wetland represents small tall sedge mires (LWT 2) within the major group small wetlands of Nyby (MTWG I). The surroundings are transitional areas from seaside birch forests to conifer forests. 96 FENNIA 194: 1 (2016)Jarmo Laitinen et al. vegetation) also occurred at relatively low alti- tudes quite close to the seaside (Fig. 7). Secondly the sizes of wetlands in MVWG 3 highly varied (Fig. 7). In the peninsula northwest of Nyby site (LWG A, Fig. 7, 8), wetlands in MVWGs 1–3 formed altitu- dinal belts in a relatively steep slope (threshold site) in the bedrock topography (Fig. 9, profile 1). In the peninsula south of Nyby site (LWG B, Fig. 7, 8) wetlands in MVWGs 2 and 3 occurred mixed with no belts from the seaside to the inland. Among nearby wetlands, wetlands in MVWG 2 (swampy mire vegetation) occurred at altitudes lower than those in MVWG 3 (mire expanse veg- etation). Irregularly rugged bedrock topography (Fig. 9, profile 2) prevailed in that area. At higher altitudes (LWGs C–E) mires mainly belonged to MVWG 3. Topographic pattern Small wetlands (I, Table 1) (0.1–1 ha, 1–10 m a.s.l.) had four Local Wetlands Types (LWTs). (1) Small reed marshes (0.1–0.7 ha) (Table 2, Fig. 8) did not belong to mires proper in having no peat layer and no mire vegetation. The centers of wet- lands were occupied by Phragmites marsh (RuLu) with scattered patches of Sphagnum squarrosum. In the peripheries of the depressions, Salix Myrica swamp (PaMyrLu) was found in some cases. The surroundings were partly Salix phylicifolia thick- ets, mostly coastal birch forests. (2) Small tall- sedge mires (0.1–0.7 ha) (Tables 2 and 3, Fig. 7) occurred in small depressions in seaside birch for- ests or near them. Three mires (Fig. 6, mires 6, 8, 10) were solely composed of swamp types includ- ing the sedge herb swamp (RuLu) and the Betula pubescens swamp (KoLu), while in the other mires swampy fen vegetation with monotonous tall- sedge stands (Carex rostrata, C. aquatilis) and uni- form Sphagnum cover (often S. riparium) domi- nated. (3) Small Sphagnum mires (0.1–1 ha) (Ta- ble 2, 3, Fig. 7) were either characterized by ex- tremely poor Sphagnum flark fen (OlSphRiN) or extremely poor short-sedge pine fen (OlLkR). (4) Small pine and spruce mires (0.4–0.7 ha) (Table 2, Fig. 7) were characterized by Carex globularis pine mire dominated by Sphagnum fuscum (PsR), other pine mires (RaR, IR, PsKR), swampy Betula pubescens fen (LuNK) and thin-peated Vaccinium myrtillus spruce mire (MKgK). Evolving mire complexes (II, Table 1) (2–185 ha, 4–53 m a.s.l.) had six LWTs (5–10). (5) Un- patterned swampy aapa mires (2–14 ha) (Tables 4, 3, 5, Fig. 7) were mainly relatively small mires and had central basins with at least partly swampy vegetation, while peripheral parts were variably developed and could have extremely poor lawn fen types (OlLkR, OlKaN with Erio- phorum vaginatum) (Table 4, mire 21). (6) Un- patterned lawn aapa mires of Nyby (4–6 ha) (Ta- ble 4, 5, Fig. 7) were relatively small sloping mires at low altitudes (10–17 m a.s.l.) near catch- ment divides. They had extremely poor lawn fen types (OlLkN, OlKaN, OlKaNR with Trichopho- rum cespitosum, OlLkR). Central basins were small and poorly discernible on air photos. (7) Unpatterned flark aapa mires (19–82 ha) (Table 5, Fig. 7) at the altitude from 18 to 22 m a.s.l. were characterized by central basins with con- siderable areas with moderately poor mud bot- tom flark fen (MeRuRiN) dominated by Carex livida. Such flark fens also occurred abundantly in patterned aapa mires at higher altitudes. In the peripheral parts of unpatterned flark aapa mires there also occasionally occurred moderately poor fen (Me-) types (MeKaSR, MeKaSN), which were absent from small unpatterned lawn aapa Fig. 4. Käärmesuo mire, locality 37 in the inland at 39 m a.s.l., bordering on rock outcrops. The locality represents wetlands with mire expanse vegetation (MVWG 3): species indicating surface water influ- ence (Sumpfigkeit) are lacking and there occur spe- cies of wet fens (flark fens). Topographically the wet- land belongs to semi-patterned aapa mires (LWT 8) within the major group evolving mire complexes of Nyby (MTWG II). Aapa-mire strings are hardly visi- ble in the field, but in air photos of larger scales, a weak flark-string pattern is visible in large parts of the mire complex. FENNIA 194: 1 (2016) 97Ecological, topographic and successional patterns Fi g. 5. C la ss ifi ca tio n of w et la nd s, b as ed o n th e ve ge ta tio n ty pe co m po si tio n of e ac h w et la nd . M aj or V eg e- ta tio na l W et la nd G ro up s (M V W G s) a re 1 m ar sh y m in er al w et - la nd ve ge ta tio n, 2 sw am py m ire v eg et a- tio n an d 3 m ire e x- pa ns e ve ge ta tio n. V eg - et at io n ty pe s ar e ar - ra ng ed ac co rd in g to th ei r m ea n al tit ud es . M ic ro s ite s (M IC RO ) w ith su rfa ce ar ea s fro m 1 to 1 00 m ² an d lo ca l m ire s ite s (L O - CA L) w ith a pl an t co m m un ity ha rd to pl ac e in to or di na ry m ire si te ty pe s a re p re - se nt ed . X1 –X 45 r ef er to w et la nd lo ca tio ns . X1 X4 X3 X2 X8 X10 X6 X31 X16 X7 X11 X5 X9 X13 X12 X24 X25 X17 X18 X21 X14 X20 X19 X15 X33 X32 X29 X43 X23 X22 X30 X35 X27 X28 X34 X26 X38 X37 X41 X44 X36 X42 X45 X40 X39 R hy fu sR uR iL N in te rm ed ia te m ud b ot to m fl ar k fe n d. b y R . f us ca Ke LR ri ch m ire e xp an se p in e fe n O lS co m N e xt re m el y po or S . c om pa ct um lo w −s ed ge fe n (M IC R O ) R ev R iL ri ch S co rp id iu m re vo lv en s fla rk fe n (M IC R O ) M eR hy fu sR uR iN m od . p oo r m ud b ot to m fl ar k fe n d. b y R . f us ca Sp hL N in te rm ed ia te S ph ag nu m (l aw n) fe n Lo eb ad LN in te rm ed ia te L oe sk yp nu m b ad iu m fe n (M IC R O ) R uR iL ri ch m ud b ot to m fl ar k fe n W ar ns ar m Lä N W ar ns to rfi a sa rm en to sa s pr in g fe n (M IC R O ) O lR uR iN R e xt re m el y po or m ud b ot to m fl ar k pi ne fe n M eK aN m od er at el y po or S . p ap ill os um lo w −s ed ge fe n Lh K th in −p ea te d ric h sp ru ce m ire (M IC R O ) O lS co m N R e xt . p oo r S . c om pa ct um lo w −s ed ge p in e fe n (M IC R O ) R hK gK th in −p ea te d he rb s pr uc e m ire M eK aN R m od er at el y po or S . p ap ill os um lo w −s ed ge p in e fe n M eS co m N m od . p oo r S . c om pa ct um lo w −s ed ge fe n (M IC R O ) Sp hL N R in te rm ed ia te S ph ag nu m (l aw n) p in e fe n Sc oR iL ri ch S co rp id iu m s co rp io id es fl ar k fe n O lK aN R e xt re m el y po or S . p ap ill os um lo w −s ed ge p in e fe n Kg R th in −p ea te d pi ne m ire M eR uR iN R m od er at el y po or m ud b ot to m fl ar k pi ne fe n TR E . v ag in at um p in e bo g O lK aS R e xt re m el y po or S . p ap ill os um ta ll− se dg e pi ne fe n O lR iK aN e xt . p oo r S . p ap ill os um lo w −s ed ge fe n w ith fl ar k ch ar M eS R m od er at el y po or ta ll− se dg e pi ne fe n C aL ri ch C am py liu m s te lla tu m fe n O lR uR iN e xt re m el y po or m ud b ot to m fl ar k fe n M eK aS N m od er at el y po or S . p ap ill os um ta ll− se dg e fe n M eK aS R m od er at el y po or S . p ap ill os um ta ll− se dg e pi ne fe n IR d w ar f− sh ru b pi ne b og M eL kN m od er at el y po or lo w −s ed ge fe n Ps R C . g lo bu la ris p in e m ire O lL kN e xt re m el y po or lo w −s ed ge fe n O lK aN e xt re m el y po or S . p ap ill os um lo w −s ed ge fe n R aR S . f us cu m b og R hK h er b. ..g ra ss s pr uc e m ire Sp hK uN S ph ag nu m h ol lo w b og O lK aS N e xt re m el y po or S . p ap ill os um ta ll− se dg e fe n O lL kR e xt re m el y po or s ho rt se dg e pi ne fe n M eS N m od er at el y po or ta ll− se dg e fe n O lS ph R iN e xt re m el y po or S ph ag nu m fl ar k fe n LR ri ch p in e fe n (L O C A L) R uR iL N R in te rm ed ia te m ud b ot to m fl ar k pi ne fe n R uK uN m ud b ot to m b og M eR uR iN m od er at el y po or m ud b ot to m fl ar k fe n O lS R e xt re m el y po or ta ll− se dg e pi ne fe n O lS ph R iN R e xt re m el y po or S ph ag nu m fl ar k pi ne fe n M eS K m od er at el y po or ta ll− se dg e B .p ub es ce ns fe n M K gK th in −p ea te d Va cc in iu m m yr til lu s sp ru ce m ire Ps K R C ar ex g lo bu la ris s pr uc e pi ne m ire R uR iL N in te rm ed ia te m ud b ot to m fl ar k fe n O lS K e xt re m el y po or ta ll− se dg e B .p ub es ce ns fe n O lS N e xt re m el y po or ta ll− se dg e fe n O m Lk N o m br ot ro ph ic lo w s ed ge fe n M eS ph R iN R m od er at el y po or S ph ag nu m fl ar k pi ne fe n N ig N K C ar ex n ig ra B .p ub es ce ns fe n Lu N K s w am py B .p ub es ce ns fe n M iR aR m in er ot ro ph ic S . f us cu m m ire (L O C A L) M eS ph R iN m od er at el y po or S ph ag nu m fl ar k fe n M eL uR iS N m od p oo r s w am py s ed ge fe n w ith fl ar k ch ar (L O C A L) Lu R iS N s w am py s ed ge fe n w ith fl ar k ch ar ac te r ( LO C A L) Lu N s w am p fe n H al u A ln us in ca na s w am p (L O C A L) Te Lu A ln us g lu tin os a sw am p O lL uS N e xt re m el y po or s w am py ta ll se dg e fe n (L O C A L) Ko Lu B et ul a pu be sc en s sw am p SR hL u se dg e he rb s w am p R uL u P hr ag m ite s m ar sh Pa M yr Lu S al ix M yr ic a sw am p 1 2 3 98 FENNIA 194: 1 (2016)Jarmo Laitinen et al. mires at lower altitudes. Large unpatterned flark aapa mire 35 (Ulkusuo) had a high number of vegetation types including intermediate (SphLNR) and rich fen types (CaL, ScoRiL). Sev- eral areas of Sphagnum fuscum bog occurred. (8) Semi-patterned aapa mires (22–31 ha) (Table 5, 6, Fig. 7) were characterized by weakly discern- ible strings at least in small parts of their central basins. (9) Aapa Sphagnum fuscum bog 34 (Jäkäläsuo) (24 ha) (Table 6, Fig. 7) was domi- nated by a bog part, which was unpatterned and nearly treeless, but additionally had a minor aapa mire part with a flark-dominated central ba- sin (with a poorly developed flark-string pattern) and a narrow lawn-dominated peripheral part. (10) Patterned aapa mires (14–185 ha) (Table 5, 6, Fig. 7) had clearly discernible strings at least in small parts of their central basins. Proportions of flark-level dominated central basins, lawn- dominated peripheral parts and small Sphagnum fuscum bogs varied among mires. The distal parts of two mire complexes (number 41 and 42) had outlet fens (Laitinen et al. 2007) with a highly dense flark-string pattern. The locality at the low- est altitude (30 m a.s.l.), which was ascribed to patterned aapa mires (Honkisuo, mire 36), was specified by the occurrence of broad Molinia caerulea strings clearly visible on air photos. Among both MTWGs, LWTs with marshy or at least partly swampy vegetation (LWTs 1, 2, 5) mainly located in the central parts of catchment areas (Table 1). LWTs among small mires with mainly mire expanse vegetation (LWTs 3, 4) lo- cated in the peripheral parts of catchment areas. LWTs among aapa mires with mainly mire ex- panse vegetation (LWTs 6–10) had variation with regard to the location of mires in catch- ment areas. Distribution of vegetation types across topographic groups Two thirds of frequent vegetation types were com- mon to small wetlands and evolving mire com- plexes (Table 7), while only one fifth of infrequent communities and vegetation types were common to two MTWGs (Table 8). Vegetation types com- mon to small wetlands and aapa mires occurred across the whole range of altitudinal variation pre- sent, from about 1 to 53 m a.s.l. (Table 7, 8), while only two communities (Salix Myrica swamp, Pa- MyrLu, and extremely poor swampy tall-sedge fen, OlLuSN) were present in small wetlands but not in mire complexes (Table 8). Vegetation types present only in evolving mire complexes occurred at the altitude from about 6 to 53 m a.s.l, and their bulk occurred from 11 to 53 m a.s.l, where wetlands belonging to small wetlands were absent in the present material. Moderately poor fen (Me-) types with mire expanse vegetation did not occur until at evolving mire complexes, and among them they −0.6 −0.4 −0.2 0.0 0.2 −0 .3 −0 .2 −0 .1 0. 0 0. 1 0. 2 0. 3 NMDS1 NM DS 2 X1 X2 X3 X4 X5 X6 X7 X8 X9 X10 X11 X12X13 X14 X15 X16 X17 X18 X19 X20 X21 X22 X23 X24 X25 X26 X27 X28 X29 X30 X31 X32 X33 X34 X35 X36 X37X38 X39 X40 X41 X42 X43 X44 X45 3 1 2 Fig. 6. Ordination of wetlands and contours (m a.s.l.) as mean val- ues. Major Vegetation- al Wetland Groups (MVWGs) are 1 marshy mineral wet- land vegetation, 2 swampy mire vegeta- tion and 3 mire ex- panse vegetation. The locality numbers of wetlands are in boxes. FENNIA 194: 1 (2016) 99Ecological, topographic and successional patterns did not occur at the lowest altitudes. The most fre- quent vegetation type of this group was moder- ately poor Sphagnum papillosum tall-sedge fen (MeKaSN) (Table 7). Among frequent vegetation types (Table 7), swampy birch fen (LuNK) had a wide range across local wetland types both within small wetlands and mire complexes. Extremely poor Sphagnum flark fen (OlSphRiN) characterized small Sphag- num mires (4–6 m a.s.l.) among small wetlands and showed the highest frequency of all the vege- tation types across the whole set of evolving mire complexes. Extremely poor short sedge pine fen (OlLkR) showed the same pattern. Sphagnum fus- cum bog (RaR) occurred among small wetlands from small Sphagnum mires (4–6 m a.s.l.) to small pine and spruce mires (7–9 m a.s.l.). The occur- rence of Sphagnum fuscum bog (RaR) in mire complexes strikingly resembled its occurrence in small wetlands: it was most frequent at relatively high altitudes in both groups, while it occurred across the whole set of mire complexes. The pat- tern of Carex globularis pine mire (PsR) resembled that of the Sphagnum fuscum bog. Among infrequent vegetation types (Table 8), Sa- lix Myrica swamp (PaMyrLu) confined to the pe- ripheral parts of reed marshes (LWT 1). Betula pu- bescens swamp (KoLu) occurred both in small wet- lands and aapa mires but confined to swampy local types, to small tall-sedge mires (0.7–3 m a.s.l.) and to unpatterned swampy aapa mires (4–18 m a.s.l.). Rare Alnus glutinosa swamp (TeLu) and rare Alnus incana swamp (HaLu) confined here to the unpat- terned swampy aapa mire 24 (Fig. 1), but the find- ings, however, did not represent totally intact veg- etation, because they were affected by the addi- tional water flow and supplementary nutrients de- rived from a former, overgrown artificial ditch. Moderately poor swampy sedge fen with flark char- acter (MeLuRiSN, incl. Cinclidium subrotundum) was a significant community confining to unpat- terned swampy aapa mires (locality 21, Fig. 1). In- termediate mud bottom flark fen (MeRuRiLN) oc- curred scantily across almost the whole set of mire complexes. A specific group of vegetation types not present until in some of patterned aapa mires of LWG E at high altitudes (43–53 m a.s.l.) (Table 6) were moderately poor spring fen patches (Warn- Fig. 7. Major Vegetational Wetland Groups (MVWGs: 1 marshy mineral wetland vegetation, 2 swampy mire vegetation, 3 mire expanse vegetation) and local wetland groups (LWGs A–E) in the map on the left. Local wetland types (LWTs 1–10, where transitional mires (0) refer to wetlands not classified on the level of local wetland types) and the locations of two altitude profiles (Fig. 9) in the map on the right. Contour lines are at the intervals of 10 m. 100 FENNIA 194: 1 (2016)Jarmo Laitinen et al. sarmLäN), patches and small areas of intermediate Loeskypnum badium fen (LoebadLN), small areas of intermediate Sphagnum (lawn) fen (SphLN), patches or small areas of rich mud bottom flark fens (RuRiL) and rich Scorpidium revolvens flark fens (RevRiL) and moderately poor and intermedi- ate flark fens dominated by Rhynchospora fusca (MeRhyfusRuRiN, RhyfusRuRiLN). Discussion Use of vegetation types for analysis Classification and ordination approaches were used for the analysis of the wetland groups and for the interpretation of the succession in this re- search. However, instead of the plant species lists recorded from small sample plots of a standard size (Rehell et al. 2012a, 2012b; Tuittila et al. 2013), we used the vegetation type lists of the Finnish mire site types, recorded from whole wet- lands of highly various sizes. The approach seemed to operate, as the results were reasonable. Vegeta- tion type lists, along with species lists, are fre- quently used in Finland in practical projects for comparing the conservation values of localities, using official conservation status for national veg- etation types (Raunio et al. 2008). Generally, the relying on vegetation types is a result of a long his- tory in practical vegetation science in Finland (Ok- sanen 1990; Lindholm 2013b). Scientific research has not previously used vegetation type lists as Fig. 8. Local Wetland Groups (LGWs): A wetland group (1–10 m a.s.l.) in peninsula north of Nyby site, B wet- land group (2–6 m a.s.l.) in peninsula south of Nyby site , and C wetland group (6 – 18 m a.s.l.) in the inland near the seaside. Major Vegetation Wetland Groups (MVWGs) are 1 marshy mineral wetland vegetation, 2 swampy mire vegetation, 3 mire expanse vegetation. Contour lines are at the intervals of 5 m. For the vegeta- tion type compositions of wetland groups A, B and C, see Table 2, 3 and 4, respectively. For vegetation type compositions of wetland groups D and E, see Table 5 and 6, respectively, and Fig. 7. FENNIA 194: 1 (2016) 101Ecological, topographic and successional patterns data for analyses because vegetation types are subjective units compared to normally used spe- cies. In our opinion, however, this kind of usage of the vegetation types is valid for a large-scale veg- etation survey intending to show only major trends between entire wetlands. Another special question for the usage of the vegetation types in the present study is the poor specification of the mire vegeta- tion types near the coast (Brandt 1948), perhaps partly with the exception of the swamp vegetation (Eurola & Kaakinen 1978; Eurola et al. 1984, 1995, 2015) at the lowest altitudes. This brings a possible cause for a mistake, which we tried to overcome by providing supplementary communities fre- quently observed in the zone above the coastal marshes and swamps. The additional communi- ties, however, are only shortly described with no basic documentation with sample plots. This ap- proach to describing plant communities is not valid from the point of view of a specific descrip- tion of new plant communities but may be applied for the present study representing a survey-like geographic investigation with a limited time for the field work. Ecological and hydrological patterns across wetlands The major vegetation type gradient for the whole group of wetlands of Nyby was interpreted with the classification and ordination of entire wetlands on the basis of their vegetation type composition (Fig. 5, 6). After several attempts and comparisons, it appeared that a solution in clustering with no more than three MVWGs (1 reed marshes, 2 swampy mire vegetation, 3 mire expanse vegeta- tion) is valid. The three-division into MVWGs, and the locations of each group in the ordination, highlight the major vegetation type gradient among Nyby wetlands. Reed marshes (1) seem a relatively separate group, and they represent main- ly mineral wetland vegetation dominated by Phragmites australis (e.g. with Myrica gale) with an occasional surface water influence of the brackish water along with the surface water influence of the fresh water (Sumpfigkeit, Tuomikoski 1955; Ruuhi- järvi 1960). The transition from MVWG 2 to 3 rep- resents a classic mire margin to expanse gradient with the mire margin vegetation here referring to swamps (Eurola et al. 1984, 1995, 2015) and the mire expanse vegetation mainly referring to tree- less poor to intermediate fens including treeless lawn and flark level bogs (Weissmoore, Ruuhijärvi 1960; Eurola 1962) and to hummock-level pine mires (Reisermoore, Ruuhijärvi 1960; Eurola 1962), and for a diminutive part to rich fens with mire expanse vegetation (Braunmoore, Ruuhijärvi 1960). The gradient from swamps to mire expanse vegetation represents a highly expected pattern, which is indirectly shown with vegetation descrip- tions as a major gradient from south-boreal coastal mires to raised bogs (Aario 1932; Brandt 1948) and as a gradient from mid-boreal coastal mires to aapa mires (Kukko-oja et al. 2003). In the latter study area (Siikajoki sand area), the universally much used fen to bog gradient was shown as a major succession gradient in the study of Tuittila et Fig. 9. Altitude relationships of the study area. The lo- cations of the profiles 1 and 2 are indicated in Fig. 7. 102 FENNIA 194: 1 (2016)Jarmo Laitinen et al. al. (2013). This is not, however, necessarily at odds with the result of Kukko-oja et al. (2003) and with the result of the present study, because the study of Tuittila et al. (2013) holds to the ombro-minero gradient, not specifically dealing with the mire margin to expanse gradient, and because ‘bog’ is used in a wide and general sense avoiding the questions of specific mire complex types such as aapa mires vs. raised bogs. We conclude that the result of the present study, as far as the major veg- etation gradient is concerned, contributes to a pat- tern already established for mires at different alti- tudes on the land uplift coast rather than provides new viewpoints for the gradient relationships of boreal coastal mires. From other aspects of mire margin vegetation, spruce mire influence (Bruchmoorigkeit, Ruuhijärvi 1960) occurs spo- radically at different altitudes in the wetlands of Nyby, while groundwater influence (Quelligkeit, Ruuhijärvi 1960) is highly scanty. The scantiness of the spruce mires and spring fens is probably af- fected by the prevailing bedrock terrain, as called by Alalammi (1990). In hydrological interpretations between the veg- etation and the water-flow pattern, the entirety of mineral-soil areas, brooks, ponds, wetlands and man-made ditches etc. exactly shows the actual pattern. The present material has a constraint of 45 wetlands in this study representing a sample of wetlands (which, however, constitutes the bulk of Topographic pattern Ecological pattern Principal locations of wetlands Major Topographic Wetland Groups (MTWGs) Local Wetland Types (LWTs) Major Vegetational Wetland Groups (MVWGs)  wetland size  wetland size  vegetation type composition  peatland morphology  vegetation type composition (cluster a.)  littoral of the sea  central or peripheral part of a catchment area I Small wetlands (0.1–1 ha, 1–10 m a.s.l.) 1 Small reed marshes (0.1–0.7 ha, 0.8–1.2 m a.s.l.) 1 Marshy mineral wetland vegetation Littoral Center 2 Small tall-sedge mires (0.1–0.7 ha, 0. 7–3 m a.s.l.) 2 Swampy mire vegetation Center 3 Small Sphagnum mires (0.1–1 ha, 4–6 m a.s.l.) 3 Mire expanse vegetation Periphery 4 Small pine and spruce mires (0.4–0.7 ha, 7–9 m a.s.l.) II Evolving mire complexes (2–185 ha, 4–53 m a.s.l.) 5 Unpatterned swampy aapa mires (2–14 ha, 4–18 m a.s.l.) 2 Swampy mire vegetation Center 6 Unpatterned lawn aapa mires (4–6 ha, 10–18 m a.s.l.) 3 Mire expanse vegetation Periphery 7 Unpatterned flark aapa mires (9–82 ha,18–22 m a.s.l.) Center or Center–periphery 8 Semi-patterned aapa mires (22–31 ha, 25–40 m a.s.l.) Center–periphery 9 Aapa Sphagnum fuscum bogs (24 ha, 34 m a.s.l.) Periphery 10 Patterned aapa mires (14–185 ha, 30–53 m a.s.l.) Center or Center–periphery Table 1. Topographic and ecological patterns of Nyby wetlands based on the wetland classifications. The char- acteristic locations of wetlands on catchment areas are shown. FENNIA 194: 1 (2016) 103Ecological, topographic and successional patterns wetlands present in Nyby area). The following pat- tern, thus, seems evident in Nyby. The distribution of vegetation types in small wetlands (1–10 m a.s.l.) in LWG B (Fig. 8) south east of Nyby site shows a pattern related to the locations of those wetlands in peripheries vs. centers of minute catchment areas. Wetlands on hills, which are in the peripheral parts of catchment areas, have mire expanse vegetation (MVWG 3), while wetlands in depressions, which are in the central parts of catchment areas, have swampy mire vegetation (MVWG 2) (Sumpfigkeit, Tuomikoski 1955; Ruuhi- järvi 1960). This simple topographic pattern highly agrees with the hypothesis of Ivanov (1981) for larger mire complexes, according to which the rate of acrotelmic flow of water in the catchment centers of mires exceeds that in the catchment pe- ripheries of those mires. We conclude that the dis- tribution of the Major Vegetational Wetland Groups (MVWGs) among this coastal group of mires specifically responds to a hydrological pat- tern suggested by Ivanov (1981). There is evidence (Hose et al. 2014) that this pattern refers to a gen- eral pattern in wetlands: the vegetation structure of wetlands highly responses to even slight altitude differences (one or a couple of meters) in the land- scape, and even the vegetation of separate wet- lands at slightly higher altitudes deviates from that in the corresponding nearby wetlands at slightly lower altitudes. This highlights the significance of the water-flow pattern in the landscape and the ne- cessity to consider the vegetation of mires in con- nection with their topographic positions and in connection with the vegetation of close by mires. Topographic and climatic distribution of vegetation types Vegetation types in Nyby and the Finnish main mire vegetation units (Eurola et al. 1984) have various climatic distribution features and relation- ships to primary succession. Swamps (as a group) with a southern global distribution (Eurola & Kaakinen 1979) and with a Finnish distribution focus in the hemiboreal zone (Eurola et al. 1995; Kaakinen et al. 2008) concentrate on low alti- tudes in Nyby (Table 7, 8) as in the south-boreal Wetland location 1 4 3 2 8 10 6 7 11 5 9 14 20 19 MVWG 1 1 1 1 2 2 2 2 2 2 2 3 3 3 MTWG I I I I I I I I I I I I I I LWT 1 1 1 1 2 2 2 2 2 2 2 3 4 4 Altitude (m a.s.l.) 0.8 0.8 1 1 0.7 1 1 2 2 2 2 5 7 9 Area (hectares) 0.2 0.7 0.1 0.0 0.4 0.1 0.6 0.4 0.6 0.2 0.7 0.4 0.7 0.4 Vegetation type PaMyrLu Salix Myrica swamp X X X RuLu Phragmites marsh X X X X SRhLu Sedge herb swamp X X X X X KoLu Betula pubescens swamp X OlLuSN Extremely poor swampy tall sedge fen (LOCAL) X LuN Swamp fen X X X X LuRiSN Swampy sedge fen with flark character (LOCAL) X LuNK Swampy Betula pubescens fen X X X X X X X OlSN Extremely poor tall-ssedge fen X OlSK Extremely poor tall-sedge Betula pubescens fen X X PsKR Carex globularis spurce pine mire X MKgK Thin-peated Vaccinium myrtillus spruce mire X X X OlSphRiN Extremely poor Sphagnum flark fen X RaR Sphagnum fuscum bog X PsR Carex globularis pine mire X X IR Dwarf-shrub pine bog X   Table 2. Local Wetland Group A in peninsula north of Nyby site (1–10 m a.s.l., all wetlands below one hec- tare). For each wetland location (see Fig. 1 for place names), Major Vegetational Wetland Group (MVWG), Major Topographic Wetland Group (MTWG), Local Wetland Type (LWT), altitude, area and vegetation types are shown. Wetlands are arranged according to vegetation type composition (1 marshy mineral wetland veg- etation, 2 swampy mire vegetation, 3 mire expanse vegetation) and altitude within each major group. Vegeta- tion types are arranged according to their mean altitude in the whole material. LWTs are 1 small reed marshes, 2 small tall-sedge mires, 3 small Sphagnum mires and 4 small pine and spruce mires. For summary of local wetland types, see Table 1. LOCAL refers to a local community. 104 FENNIA 194: 1 (2016)Jarmo Laitinen et al. raised bog zone of Finland (Brandt 1948). The southern character of the swamps, included with the reed marshes (Brandt 1948; Eurola et al. 1984, 1995, 2015), deserves consideration, as accord- ing to an optional mire zone and section division of North Fennoscandia (Eurola & Vorren 1980), a narrow coastal zone around the northern end of the Gulf of Bothnia (with a part of Nyby study area) belongs to the south-boreal zone instead of the mid-boreal zone. In our opinion, however, the preference of swamps near the seaside is perhaps a successional feature rather than a climatic or vegetation-zonal feature because there is no evi- dence from a climatic difference between the sites near the sea and the sites at slightly higher alti- tudes in the lowland. Vegetation types with a current mid-boreal fo- cus in Finland (Kaakinen et al. 2008) mainly avoid the lowest altitudes characterized by the reed marshes and swamps in Nyby. Such vegetation Wetland location 13 16 17 18 15 22 23 MVWG 2 2 2 2 3 3 3 MTWG I I II I I I I LWT 2 2 5 0 3 3 3 Altitude (m a.s.l.) 2 3 4 5 4 6 6 Area (hectares) 0.2 0.4 3 1 0.1 1 0.7 Vegetation type RuLu Phragmites marsh X SRhLu Sedge herb swamp X KoLu Betula pubescens swamp X OlLuSN Extremely poor swampy tall sedge fen (LOCAL) X LuN Swamp fen X X LuRiSN Swampy sedge fen with flark character (LOCAL) X MiRaR Minerotrophic Sphagnum fuscum bog (LOCAL) X X LuNK Swampy Betula pubescens fen X X NigNK Carex nigra Betula pubescens fen X X OlSN Extremely poor tall-sedge fen X X OlSK Extremely poor tall-sedge Betula pubescens fen X X X X MKgK Thin-peated Vaccinium myrtillus spruce mire X MeSK Moderately poor tall-sedge Betula pubescens fen X X OlSR Extremely poor tall-sedge pine fen X X X OlSphRiN Extremely poor Sphagnum flark fen X X OlLkR Extremely poor short sedge pine fen X X X X OlKaSN Extremely poor Sphagnum papillosum tall-sedge fen X RaR Sphagnum fuscum bog X X OlLkN Extremely poor low-sedge fen X PsR Carex globularis pine mire X IR Dwarf-shrub pine bog X   Table 3. Local Wetland Group B in peninsula south of Nyby site (2–6 m a.s.l., below 1–3 hectares). For each wetland location (see Fig. 1 for place names), Major Vegetational Wetland Group (MVWG), Major Topograph- ic Wetland Group (MTWG), Local Wetland Type (LWT), altitude, area and vegetation types are shown. Wet- lands are arranged according to vegetation type composition (2 swampy mire vegetation, 3 mire expanse vegetation), and altitude within each major group. Vegetation types are arranged according to their mean alti- tude in the whole material. LWTs are 0 transitional mires (not classified into LWTs), 2 small tall-sedge mires, 3 small Sphagnum mires and 5 unpatterned swampy aapa mires. For summary of LWTs, see Table 1. LOCAL refers to a local community. FENNIA 194: 1 (2016) 105Ecological, topographic and successional patterns types include lawn-dominated extremely poor fen types, the Sphagnum papillosum pine fen (KaR), the short-sedge pine fen (LkR) and the Sphagnum papillosum fen (KaN) (Table 7), which occupy the bulk of peripheral lawns (Laitinen et al. 2007) of several local wetland types among evolving mire complexes. The aapa mire chronosequence of Ryöskäri–Nikkilänaapa–Kairavaara (0–70 m a.s.l.), 15 km north of the study area, shows a pattern re- sembling that of Nyby. There the focus of Sphag- num papillosum is at the altitudes of 30–50 m a.s.l. (Rehell & Laitinen 2014). Mid-boreal focus of the above-mentioned vegetation types is trivial and climatically expected, as the mid-boreal zone of Finland is characterized by the lawn in mires, while the north-boreal zone is characterized by the flark level according to Ruuhijärvi (1960, 1983) and Eurola et al. (1984). Above-mentioned vegetation types avoiding the lowest altitudes rep- resent classic mire expanse vegetation (Weiss- moore, Weissmoor-Reisermoore, Ruuhijärvi 1960; Eurola 1962), whereas their lack from the lowest altitudes partly reflects the major gradient in the whole group of Nyby wetlands, the mire margin to expanse gradient. Also the vegetation reported highly boreal as contrast to nemoral vegetation (Rydin et al. 1999b) avoid the lowest altitudes in Nyby. Carex Table 4. Local Wetland Group C in the inland near the seaside in Nyby area (6–18 m a.s.l., below 1–6 hec- tares). For each wetland location (see Fig. 1 for place names), Major Vegetational Wetland Group (MVWG), Major Topographic Wetland Group (MTWG), Local Wetland Type (LWT), altitude, area and vegetation types are shown. Wetlands are arranged according to vegetation type composition (2 swampy mire vegetation, 3 mire expanse vegetation), and altitude within each major group. Vegetation types are arranged according to their mean altitude in the whole material. LWTs are 0 transitional mires (not classified into LWTs), 5 unpat- terned swampy aapa mires, and 6 unpatterned lawn aapa mires. For summary of LWTs, see Table 1. LOCAL refers to a local community. Wetland location 24 25 21 32 33 30 (MVWG 2 2 2 3 3 3 MTWG II II II II II II LWT 5 5 5 0 0 6 Altitude (m a.s.l.) 6 6 7 11 13 18 Area (hectares) 3 2 6 3 0.5 4 Vegetation type SRhLu Sedge herb swamp X TeLu Alnus glutinosa swamp X HaLu Alnus incana swamp X LuN Swamp fen X X X MeLuRiSN Moderately poor swampy sedge fen with flark character (LOCAL) X MeSphRiN Moderately poor Sphagnum flark fen X X NigNK Carex nigra Betula pubescens fen X MeSphRiNR Moderately poor Sphagnum flark pine fen X LuNK Swampy Betula pubescens fen X OlSN Extremely poor tall-sedge fen X X X X OlSK Extremely poor tall-sedge Betula pubescens fen X X X MKgK Thin-peated Vaccinium myrtillus spruce mire X X X MeSK Moderately poor tall-sedge Betula pubescens fen X X X OlSphRiNR Extremely poor Sphagnum flark pine fen X OlSR Extremely poor tall-sedge Betula pubescens fen X X MeRuRiN Moderately poor mud bottom flark fen X X X OlSphRiN Extremely poor Sphagnum flark fen X X X MeSN Moderately poor tall-sedge fen X X OlLkR Extremely poor low-sedge pine fen X X X OlKaSN Extremely poor Sphagnum papillosum tall-sedge fen X X RhK Herb grass spruce mire X RaR Sphagnum fuscum bog X OlKaN Extremely poor Sphagnum papillosum low-sedge fen X X OlLkN Extremely poor low-sedge fen X MeLkN Moderately poor low-sedge fen X MeKaSN Moderately poor Sphagnum papillosum tall-sedge fen X X MeSR Moderately poor tall-sedge pine fen X   106 FENNIA 194: 1 (2016)Jarmo Laitinen et al. Table 5. Local Wetland Group D in central inland in Nyby area (10–30 m a.s.l., 4–82 hectares). For each wet- land location (see Fig. 1 for place names), Major Vegetational Wetland Group (MVWG), Major Topographic Wetland Group (MTWG), Local Wetland Type (LWT), altitude, area and vegetation types are shown. Wetlands are arranged according to vegetation type composition (2 swampy mire vegetation, 3 mire expanse vegeta- tion), and altitude within each major group. Vegetation types are arranged according to their mean altitude in the whole material. LWTs: 5 unpatterned swampy aapa mires, 6 unpatterned lawn aapa mires, 7 unpatterned flark aapa mires, 8 semi-patterned aapa mires and 10 patterned aapa mires. For summary of LWTs, see Table 1. LOCAL refers to a local community. Wetland location 31 26 27 28 29 35 38 36 MVWG 2 3 3 3 3 3 3 3 MTWG II II II II II II II II LWT 5 6 6 6 7 7 8 10 Altitude (m a.s.l.) 17 11 13 16 18 22 26 30 Area (hectares) 14 4 5 6 19 82 22 43 Vegetation type SRhLu Sedge herb swamp X LuNK Swampy Betula pubescens fen X X X X NigNK Carex nigra Betula pubescens fen X OmLkN Ombrotrophic low-sedge bog X X OlSN Extremely poor tall-sedge fen X X X X X OlSK Extremely poor tall sedge Betula pubescens fen X RuRiLN Intermediate mud bottom flark fen X X PsKR Carex globularis spruce pine mire X X MKgK Thin-peated Vaccinium myrtillus spruce mire X X MeSK Moderately poof tall-sedge Betula pubescens fen X X X X OlSR Extremely poor tall-sedge pine fen X X X X X X MeRuRiN Moderately poor mud bottom flark fen X X X X X X RuKuN Mud bottom bog X RuRiLNR Intermediate mud bottom flark pine fen X LR Rich pine fen (LOCAL) X OlSphRiN Extremely poor Sphagnum flark fen X X X X X X X X MeSN Moderately poor tall-sedge fen X X OlLkR Extremely poor short sedge pine fen X X X X X X OlKaSN Extremely poor Sphagnum papillosum tall-sedge fen X X X X X X SphKuN Sphagnum hollow bog X RaR Sphagnum fuscum bog X X X X X X OlKaN Extremely poor Sphagnum papillosum low-sedge fen X X X X X X OlLkN Extremely poof low-sedge fen X X X X X X PsR Carex globularis pine mire X X X IR Dwarf-shrub pine bog X MeKaSR Moderately poor Sphagnum papillosum tall-sedge pine fen X MeKaSN Moderately poor Sphagnum papillosum tall-sedge fen X X X OlRuRiN Extremely poor mud bottom flark fen X X X X X CaL Rich Campylium stellatum fen X MeSR Moderately poor tall-sedge pine fen X OlRiKaN Extremely poor S. papillosum low-sedge fen with flark character X X X X OlKaSR Extremely poor Sphagnum papillosum tall-sedge pine fen X TR Eriophorum vaginatum pine bog X MeRuRiNR Moderately poor mud bottom flark pine fen X KgR Thin-peated pine mire X OlKaNR Extremely poor Sphagnum papillosum low-sedge pine fen X X ScoRiL Rich Scorpidium scorpioides flark fen X SphLNR Intermediate Sphagnum (lawn) pine fen X MeScomN Moderately poor Sphagnum compactum low-sedge fen (MICRO) X MeKaNR Moderately poor Sphagnum papillosum low-sedge pine fen X OlScomNR Extremely poor Sphagnum compactum low-sedge pine fen X MeKaN Moderately poor Sphagnum papillosum low-sedge fen X   FENNIA 194: 1 (2016) 107Ecological, topographic and successional patterns globularis pine mire (PsR) (Table 7), representing a frequent boreal vegetation type characterizing acid areas (Kaakinen et al. 2008; Rydin et al. 1999b), is common in Nyby at the altitudes from 6 to 53 m a.s.l, occurring in small wetlands and in evolving mire complexes. The scattered oc- currences of intermediate fens (LN) (Table 8) confine to still higher altitudes, mainly to alti- tudes from 43 to 53 m a.s.l. The high-altitude position of the intermediate Loeskypnum badi- um fen (LoebadLN) in Nyby partly agrees with the abundant occurrence of Loeskypnum badi- um at medium to high altitudes (15–50 m a.s.l) along the aapa mire chronosequence of Ryöskäri–Nikkilänaapa–Kairavaara (Rehell & Laitinen 2014), where the rich and intermediate fens with mire margin vegetation, absent from the wetlands of Nyby, occupy low altitudes above the swamp belt (Rehell et al. 2012a, 2012b). The high-altitude position of the inter- mediate Loeskypnum badium fens in mid-boreal Nyby area is additionally in agreement with the statement of Persson (1962) that the community represents classic mire expanse vegetation. The point for the Nyby study area is that this com- munity does not seem to occupy its highly spe- cific microsites until at the highest altitudes, within patterned aapa mires: increasing in mire expanse character of the vegetation was the main trend along increasing altitudes in Nyby. It is, however, remarkable that the microhabitas occupied by the community locate like habitats having groundwater influence, forming narrow lawns resembling micro soaks in the gently slop- ing proximal margins of fens, often surrounded by Sphagnum fuscum surfaces, as Ruuhijärvi (1960) states, and sometimes with micro soaks of Warnstorfia sarmentosa spring fens (Warn- sarmLäN) in the vicinity. The latter, representing a poorly documented northern boreal commu- nity in the central Finnish Lapland (Laitinen et al. 2011) and a subalpine to alpine community in the western Italian alps (Miserere et al. 2003), represents almost the only sites with evident groundwater influence in Nyby. To conclude, the mire communities representing highly bore- al vegetation in Nyby occur outside the lowest altitudes in the mid-boreal coastal lowland and either occupy scattered special patches of the sloping proximal margins of fens associated with groundwater influence (Quelligkeit, Ruuhi- järvi 1960), or they occupy frequent, larger and flatter thin-peated treed areas (Bruchmoorigkeit, Ruuhijärvi 1960; Eurola 1962) in the peripheries of mires. Both the directions of variation (Tuo- mikoski 1942, 1955) are avoided by the wet- lands at the lowest altitudes in Nyby but are abundantly present in the wetlands at low alti- tudes (1.5–15 m a.s.l.) along the aapa mire chronosequence of Ryöskäri–Nikkilänaapa– Kairavaara (Rehell et all. 2012a, 2012b; Rehell & Laitinen 2014). Successional patterns General remarks and constraints in the material In succession studies, the concept chronose- quence is much used. For example Walker et al. (2010) state that chronosequences should be used only in cases when there is evidence that sites of different ages are following the same trajectory. In the wetlands of Nyby it seems that a couple of slightly different trajectories or stretches of trajec- tories appear among wetlands, including those within small bedrock basins and those within larg- er bedrock basins. The approach used in this study allows for the reconstruction of the local wetland succession at a rough scale marked out by the MTWGs and the LWTs (Table 1), while the approach of Rehell et al. (2012a, 2012b) states for the initiation and the tra- jectory of specific mire surface levels in details. For the interpretation of the succession of the wet- lands of Nyby, there are several constraints. Firstly, at the lowest altitudes, the bedrock basins large enough for the formation of mire complexes are lacking. Secondly, in the material the small wet- lands at higher altitudes are lacking. Third notion is the same as for the hydrologic patterns: the ma- terial represents a sample including, however, the bulk of the wetlands in the study area. Finally, for the interpretation of the succession of the wetlands of Nyby, it is of some significance, into which MT- WGs some critical LWTs are placed. LWT 5, called here unpatterned swampy aapa mires (Table 1), seems an intermediate between the small wet- lands (MTWG I) and young successional stages of aapa mires (MTWG II) with the exception of mire 31 (Fig. 1), which is larger (14 ha) and locates at an altitude (18 m a.s.l.) higher than the rest of the wet- lands in that group. We, however, also regard the small wetlands (2–6 ha) at low altitudes (4–7 m a.s.l.) in LWT 5 (Fig. 7) as a young successional stage of aapa mires because they have at least a 108 FENNIA 194: 1 (2016)Jarmo Laitinen et al. Table 6. Local Wetland Group E at the highest altitude in the inland in Nyby (34–53 m asl., 14–185 hectares). For each wetland location (see Fig. 1 for place names), Major Vegetational Wetland Group (MVWG), Major Topographic Wetland Group (MTWG), Local Wetland Type (LWT), altitude, area and vegetation types are shown. Wetlands are arranged according to vegetation type composition (3 mire expanse vegetation), and altitude within each major group. Vegetation types are arranged according to their mean altitude in the whole material. LWTs are 8 semi-patterned aapa mires, 9 aapa Sphagnum fuscum bogs and 10 patterned aapa mires. For summary of LWTs, see Table 1. MICRO refers to a small-sized community. Wetland location 34 37 39 40 43 41 42 44 45 MVWG 3 3 3 3 3 3 3 3 3 MTWG II II II II II II II II II LWT 9 8 10 10 10 10 10 10 10 Altitude (m a.s.l.) 34 39 43 44 45 50 51 52 53 Area (hectares) 24 31 59 65 14 69 51 65 185 Vegetation type LuN Swamp fen X X LuNK Swampy Betula pubescens fen X X X NigNK Carex nigra Betula pubescens fen X OmLkN Ombrotrophic low sedge bog X OlSN Extremely poor tall-sedge fen X X X OlSK Extremely poor tall-sedge Betula pubescens fen X X RuRiLN Intermediate mud bottom flark fen X PsKR Carex globularis spruce pine mire X X MKgK Thin-peated Vaccinium myrtillus spruce pine mire X X X MeSK Moderately poor tall-sedge Betula pubescens fen X X X X OlSR Extremely poor tall-sedge pine fen X X X X MeRuRiN Moderately poor mud bottom flark fen X X X X X X X OlSphRiN Extremely poof Sphagnum flark fen X X X X X X X X X MeSN Moderately poor tall-sedge fen X X X X OlLkR Extremely poor short sedge pine fen X X X X X X X OlKaSN Extremely poor Sphagnum papillosum tall-sedge fen X X X X X X SphKuN Sphagnum hollow bog X RhK Herb–grass spruce mire X X RaR Sphagnum fuscum bog X X X X X X X OlKaN Extremely poor Sphagnum papillosum low-sedge fen X X X X X X X OlLkN Extremely poof low-sedge fen X X X X X X X X X PsR Carex globularis pine mire X X X X X X X X X MeLkN Moderately poor low-wedge fen X X IR Dwarf-shrub pine bog X X X MeKaSR Moderately poor Sphagnum papillosum tall-sedge pine fen X X X X MeKaSN Moderately poor Sphagnum papillosum tall-sedge fen X X X X X X X OlRuRiN Extremely poor mud-bottom flark fen X X X X X X CaL Rich Campylium stellatum fen (MICRO) X MeSR Moderately poor tall-sedge pine fen X X X X OlRiKaN Extremely poor S. papillosum low-sedge fen with flark character X X X X X OlKaSR Extremely poor Sphagnum papillosum tall-sedge pine fen X X TR Eriophorum baginatum pine bog X MeRuRiNR Moderately poor mud bottom flark pine fen X KgR Thin-peated pine mire X X OlKaNR Extremely poor Sphagnum papillosum low-sedge pine fen X X X ScoRiL Rich Scorpidium scorpioides flark fen X SphLNR Intermediate Sphagnum (lawn) pine fen X X MeKaNR Moderately poor Sphagnum papillosum low-sedge pine fen X X RhKgK Thin-peated herb spruce mire X OlScomNR Extremely poor S. compactum pine fen (MICRO) X X X LhK Thin-peated rich spruce mire (MICRO) X MeKaN Moderately poor Sphagnum papillosum low-sedge fen X X X X OlRuRiNR Extremely poor mud bottom flark pine fen X WarnsarmLäN Warnstorfia sarmentosa spring fen (MICRO) X X X RuRiL Rich mud bottom flark fen X LoebadLN Intermediate Loeskypnum badium fen X X X SphLN Intermediate Sphagnum (lawn) fen X X X MeRhyfusRuRiN Moderately poor mud bottom flark fen dominated by R. fusca X X X RevRiL Rich Scorpidium revolvens flark fen (MICRO) X X OlScomN Extremely poor Sphagnum compactum fen (MICRO) X KeLR Rich mire expanse fen X RhyfusRuRiLN Intermediate mud bottom flark fen dominated by R. fusca X   FENNIA 194: 1 (2016) 109Ecological, topographic and successional patterns weak central–peripheral pattern characteristic of aapa mires. Unpatterned lawn aapa mires of Nyby (LWT 6), which are as small (4–6 ha) as the bulk of swampy aapa mires, are undisputed aapa mires because of their treeless mire expanse vegetation and the relatively well-developed central–periph- eral topography (Laitinen et al. 2007). Succession of wetlands in small bedrock basins Part of the studied small wetlands (MTWG I) of Nyby seem to form a small successional group of its own. This concerns the wetlands near the sea- side in LWG A (Fig. 7), northwest of Nyby site, where the wetlands of various LWTs form narrow Abbreviation Vegetation type Altitude (m a.s.l.) Major Topographic Wetland Groupsa Small wetlands Evolving mire complexes Local Wetland Typesb 1 2 3 4 5 6 7 8 9 10 RuLu Phragmites marsh 0.8–4 ▄ ▬ SRhLu Sedge herb swamp 0.7–17 ▬ ▬ LuN Swamp fen 2–45 ▬ ▬ ▬ LuNK Swampy Betula pubescens fen 2–53 ▬ ▬ ▄ ▬ ▄ ▬ ▬ OlSN Extremely poor tall-sedge fen 2–45 ▬ ▬ ▬ ▄ ▄ ▬ OlSK Extr. poor tall-sedge B. pubescens fen 4–44 ▬ ▬ ▬ ▬ ▬ ▬ ▬ MKgK Thin-peated Vaccinium myrtillus spruce mires 4–53 ▬ ▄ ▬ ▬ ▬ OlSR Extremely poor tall-sedge pine fen 4–50 ▬ ▬ ▬ ▄ ▄ ▄ ▬ MeRuRiN Moderately poor mud bottom flark fen 6–53 ▬ ▬ ▄ ▄ ▬ OlSphRiN Extremely poor Sphagnum flark fen 5–53 ▬ ▬ ▄ ▄ ▄ ▄ ▄ OlLkR Extremely poor short sedge pine fen 4–53 ▬ ▬ ▄ ▬ ▄ ▄ ▬ OlKaSN Extr. poor S. papillosum tall- sedge fen 5–51 ▬ ▬ ▄ ▄ ▄ ▬ RaR Sphagnum fuscum bog 6–53 ▬ ▄ ▬ ▬ ▬ ▄ ▄ ▬ OlKaN Extr. poor S.papillosum low- sedge fen 7–53 ▬ ▄ ▄ ▬ ▄ ▬ OlLkN Extremely poor short-sedge fen 3–53 ▬ ▬ ▬ ▬ ▄ ▄ ▄ PsR Carex globularis pine mire 6–53 ▬ ▄ ▬ ▬ ▬ ▄ ▬ MeKaSN Mod. poor S. papillosum tall- sedge fen 11–53 ▬ ▄ ▄ OlRuRiN Extremely poor mud bottom flark fen 11–53 ▬ ▬ ▄ ▄ ▬ OlRiKaN Extr. poor S. papillosum low- sedge fen with flark char. 11–52 ▬ ▬ ▄ ▄ ▬ Frequency of vegetation types: ▄ constant ▬ not constant a Major Topographic Wetland Groups (MTWGs): I Small wetlands (1–10 m a.s.l.), II Mire complexes (4–53 m a.s.l.) b Local Wetland Types (LWTs): 1 Small reed marshes (0.8–1.2 m a.s.l), 2 Small tall-sedge mires (0.7–3 m a.s.l.), 3 Small Sphagnum mires (4–6 m a.s.l.), 4 Small pine and spruce mires (7–9 m a.s.l.), 5 Unpatterned swampy aapa mires (4–18 m a.s.l.), 6 Unpatterned lawn aapa mires (10–18 m a.s.l.), 7 Unpatterned flark aapa mires (18– 22 m a.s.l.), 8 Semi-patterned aapa mires (25–40 m a.s.l.), 9 Aapa Sphagnum fuscum bogs (34 m a.s.l.), 10 Patterned aapa mires (30–53 m a.s.l.) Table 7. Frequent vegetation types along the altitude gradient and across Major Topographic Wetland Groups (MTWGs) as well as Local Wetland Types (LWTs) in Nyby area. Vegetation types are arranged according to their average altitude in the whole material. 110 FENNIA 194: 1 (2016)Jarmo Laitinen et al. belts along increasing altitude (1–10 m a.s.l.), and where the local bedrock topography does not al- low the present minute wetlands to enlarge con- siderably in the future, unlike in evolving boreal mire complexes in larger bedrock basins (Bauer et al. 2003) with larger catchment areas. Those small wetlands show a possible successional pathway along the altitude gradient across all the local wetland types from small reed marshes (LWT 1) (0.8–1.2 m a.s.l.) and small tall sedge mires (LWT 2) (0.7–3 m a.s.l.) to small Sphagnum mires (LWT 3) (4–6 m a.s.l.) and to small pine and spruce mires (LWT 4) (7–9 m a.s.l.). Small reed marshes (LWT 1) and partly small tall-sedge mires (LWT 2) Abbreviation Vegetation type Altitude (m a.s.l.) Major topographic wetland groups Small wetlands Evolving mire complexes Local wetland types 1 2 3 4 5 6 7 8 9 10 PaMyrLu Salix Myrica swamp 0.8–1 ▬ OlLuSN Extremely poor swampy tall-sedge fen 2 ▬ KoLu Betula pubescens swamp 1–4 ▬ ▬ TeLu Alnus glutinosa swamp 6 ▬ HaLu Alnus incana swamp 6 ▬ LuRiSN Swampy sedge fen with flark character 4–5 ▬ ▬ MeLuRiSN Moderately poor swampy sedge fen with flark char 7 ▬ MiRaR Minerotrophic Sphagnum fuscum mire 4 ▬ ▬ RuRiLN Intermediate mud bottom flark fen 17–43 ▬ ▬ ▬ RuRiLNR Interm. mud bottom flark pine fen 22 ▬ LR Rich pine fen 22 ▬ CaL Rich Campylium stellatum fen 22–53 ▬ ▬ ScoRiL Rich Scorpidium scorpioides fen 22–43 ▬ ▬ SphLNR Interm. Sphagnum (lawn) pine fen 22–53 ▬ ▬ WarnsarmLäN Warnstorfia sarmentosa spring fen 43–51 ▬ RuRiL Rich mud bottom flark fen 44 ▬ LoebadLN Interm. Loeskypnum badium fen 43–53 ▬ SphLN Intermediate Sphagnum (lawn) fen 43–53 ▬ RevRiL Rich Scorpidium revolvens flark fen 43–44 ▬ KeLR Rich mire expanse pine fen 43 ▬ Frequency of vegetation types: ▄ constant ▬ not constant a Major Topographic Wetland Groups (MTWGs): I Small wetlands (1–10 m a.s.l.), II Mire complexes (4–53 m a.s.l.) b Local Wetland Types (LWTs): 1 Small reed marshes (0.8–1.2 m a.s.l), 2 Small tall-sedge mires (0.7–3 m a.s.l.), 3 Small Sphagnum mires (4–6 m a.s.l.), 4 Small pine and spruce mires (7–9 m a.s.l.), 5 Unpatterned swampy aapa mires (4–18 m a.s.l.), 6 Unpatterned lawn aapa mires (10–18 m a.s.l.), 7 Unpatterned flark aapa mires (18– 22 m a.s.l.), 8 Semi-patterned aapa mires (25–40 m a.s.l.), 9 Aapa Sphagnum fuscum bogs (34 m a.s.l.), 10 Patterned aapa mires (30–53 m a.s.l.) Fig. Table 8. Unfrequent communities and vegetation types along the altitude gradient and across major topo- graphic wetland groups (MTWGs) as well as Local Wetland Types (LWTs). The distribution of rare swampy communities and vegetation types (-Lu-), rare minerotrophic Sphagnum fuscum mires (MiRaR), intermediate fen types (-LN-), spring fen types (-LäN) and rich fen types (-L) are shown. Vegetation types are arranged ac- cording to their average altitude in the whole material. FENNIA 194: 1 (2016) 111Ecological, topographic and successional patterns of Nyby correspond to swamps (Sumpfmoore) of Brandt (1948) in the coast of the raised bog zone, while the small tall-sedge mires (LWT 2) partly correspond to Recurvum fens (Recurvum-Weiss- moore) of Brandt (1948) characterized by an inva- sion of Sphagnum to swamps, later also the occur- rence of Betula pubescens (swampy birch fens, LuNK, in Nyby wetlands). Small Sphagnum mires (LWT 3) of Nyby, which are currently experienc- ing both the appearance of the Sphagnum flark level with mire expanse vegetation (see Rehell et al. 2012b) and the change towards a poorer state along the poor-rich gradient (Tahvanainen 2004, 2011), do not seem to have a counterpart in the succession of mires in the raised bog zone (Brandt 1948). This is natural as the minerotrophic flark level with mire expanse vegetation is a feature characteristic of mires in the aapa mire zone (Ru- uhijärvi 1960). Small Sphagnum mires (LWT 3) of Nyby only show that also in the succession of small wetlands (MTWG I), a feature of evolving mire complexes (MTWG II), the appearance of the flark level, weakly appears. Small pine and spruce mires (LWT 4) of Nyby, which represent the suc- cessional stage at the highest altitude (7–9 m a.s.l.) along the succession of small wetlands pre- sent in the material, perhaps have a counterpart in Ledum mires of Brandt (1948) at the altitudes of 5 to 10 m a.s.l. To conclude the trajectory among the coastal group (MTWG I) of small wetlands northwest of Nyby site, it seems that it highly re- flects the mire margin (swamps) to expanse gradi- ent, which was shown as the major gradient for the whole group of 45 wetlands in Nyby. The above mentioned circumstance refers to the op- tion that mire expanse vegetation within the suc- cession of those minute mires (0.1–1 ha) is achieved during a time period shorter than (at lower altitudes than) in the mire complexes of Nyby, probably because of the smaller amounts of nutrients provided by the minute catchment areas surrounded by the small wetlands. Roughly speak- ing, considering only the major gradient at a high generalization level, it seems as if the aapa mires, during a longer time period, follow the trajectory of the small wetlands. We hypothesized that the succession of small wetlands differs from that of aapa mires with regard to vegetation type composition and peatland mor- phology. Observations largely support this pre- sumption. Firstly, evidence from the vegetation type composition agrees with this presumption, as locally rare vegetation types highly differed with regard to successional groups, and only locally common vegetation types were for the most part common to both the successional groups. Second- ly, evidence from peatland morphology mainly supports the concept of the difference between the succession of small wetlands vs. that of aapa mires. In minute depressions there is no space for a peat- land to form the complicated water-flow-depend- ent macro and microtopography characterized by climatic mire complex types (Ruuhijärvi 1960; Eu- rola 1962; Seppä 2002). Sphagnum fuscum sur- faces, however, develop in both cases. In the suc- cessional group of small wetlands, Sphagnum fus- cum surfaces finally occupy the mire centers in small pine and spruce mires (LWT 4, LWG A) (Fig. 7) like in raised bogs, referring to the oligocentral development of mires according to Ivanov (1981), while in aapa mires they occupy the peripheries of mire complexes referring to the oligoperipheral mire complex development of Ivanov (1981). In Kvarken archipelago, in the southern boreal zone, the bulk of mires are at altitudes (0–10 m a.s.l.) the same as the studied small wetlands of Nyby ac- cording to Harju (2008), who states that the mires (of several hectares) commonly develop into short sedge fens (LkN), while also Sphagnum fuscum surfaces are achieved at 10 m a.s.l. or even below. The slightly larger size of the mires described by Harju (2008) in comparison with the minute mires northwest of Nyby site suggest that intermediates between small wetlands and mire complexes are common (see the mire complex type of the land uplift coast of the Bothnian Bay, Auer 1951). Succession of wetlands in larger bedrock basins In the wetlands of Nyby it seems that more than one slightly different trajectories or stretches of trajectories appear among wetlands in bedrock basins large enough to allow the formation of mire complexes. It seems to be crucial for the tra- jectory of a mire complex if the bedrock basin is located in the central or peripheral parts of a larg- er catchment area. This location accordingly serves as an ultimate cause for the successional trajectory. Relative altitudes effect the general wa- ter flow pattern in the landscape, and the water flow pattern with the rate of the flow of mire water in each point (Ivanov 1981; Seppä 2002; Laitinen et al. 2007), associated with well-known mire- ecological factors and gradients (e.g. Sjörs 1948; Eurola et al. 1984; Tahvanainen 2004, 2011; Laitinen et al. 2008b, 2008a) directly effect on 112 FENNIA 194: 1 (2016)Jarmo Laitinen et al. plants and plant communities. Because the loca- tions of the mire basins in catchment areas are decisive in the study area, such trajectories repre- sent location-related successional pathways. a) Flark aapa mires The most evident location-related successional pathway among those mire complexes, which originally (before lateral site expansion) mainly lo- cate in the central parts of larger catchment areas, is shown by the transition along the altitude gradi- ent across the whole set of flark aapa mires (LWTs 5, 7, 8, 10) (Fig. 7). It is precisely the question of the trajectories of the central basins (Laitinen et al. 2007) of those mire complexes. Surface water in- fluence (Sumpfigkeit, Ruuhijärvi 1960) appears in the youngest successional stage of this set (unpat- terned swampy aapa mires, LWT 5), as in those small wetlands, which are located in the same way in the central parts of catchment areas. The actual initial stages of aapa mires are lacking in Nyby be- cause of the lack of bedrock basins large enough at the lowest altitudes (cf. the study area of Rehell et al. 2012a, 2012b). Unpatterned flark aapa mires (LWT 7) (18–22 m a.s.l.) are early flark aapa mires with mire expanse vegetation but with a lack of strings in central basins. Semi-patterned aapa mires (LWT 8) (25–40 m a.s.l.) are semi-mature flark aapa mires, which have poorly discernible strings in central basins, and patterned aapa mires (LWT 10) (30–53 m a.s.l.) are the mature stages of flark aapa mires with clearly discernible strings in central basins. It must be stressed that the lack of the patterning in wet central basins of an aapa mire may alternatively be due to the young succes- sional age of the site (Rehell et al. 2012a, 2012b) or a weak flow of mire water caused by a highly flat substratum of a certain part of the flark area (Laitinen et al. 2007). Accordingly, the state of the patterning in the central basins of mature aapa mires may vary within the frames of one and the same mire complex even so that those variations in the patterning are striking in some of the largest mature aapa mires of the lowland at higher alti- tudes (Hirvisuo, 120 m a.s.l., Laitinen et al. 2005). Also outlet fens (Laitinen et al. 2007) with a high rate of flow of the mire water and an exceptionally dense flark–string pattern totally confine to mature aapa mires in Nyby (to distal parts of mires 41 and 42) (Fig. 1). It seems that at a still higher altitude (75 m a.s.l., Hoikkasuo, Laitinen et al. 2007), the dense transverse patterning (of stings and flaks) in outlet fens even turns into an indistinct longitudi- nal patterning. It is not quite certain whether this topographic variation among outlet fens is due to the successional change (so related to time) or merely due to the present water-flow conditions (so related to hydrology). We conclude that the morphologic changes of aapa mire centers do not at all confine to young successional stages, as is also seen in the studies of Rehell et al. (2012a, 2012b), and that the increasing of the proportion of the mud bottom, the initiation and the forma- tion of the flark string pattern and especially the change towards a higher diversity in the micro- topography, characterize the trajectory of central basins of aapa mires. b) Mire systems (mixed complexes) and bog complex types Nyby area provides additional examples of evolv- ing mire systems (Heikkilä et al. 2001; see also Laitinen et al. 2007), which include both an aapa mire part and a bog complex part. Such systems, which are nowadays regarded fairly common in Finland (Heikkilä et al. 2006), were called mixed complexes by Tolonen (1967). Transition from small unpatterned lawn aapa mires 26, 27 and 28 (LWT 6) to the aapa Sphagnum fuscum bog Jäkäläsuo (LWT 9, mire 34) (Fig. 1, 7), in which the bog part is dominant, suggests a possible location- related successional stretch at catchment divides at relatively low altitudes (10–34 m a.s.l.). That stretch represents a change from a stage of young aapa mire with extremely poor fens to a stage of an unpatterned Sphagnum fuscum bog. Instead, pat- terned sloping bogs (eccentric bots) near the study area confine to higher altitudes (above 60 m a.s.l.), referring perhaps to a longer time period taken by the succession of that bog complex type. In the study area of Brandt (1948), in the (climatic) south- boreal concentric Kermi raised bog zone in Fin- land (Eurola 1962), there is a narrow coastal belt at the altitudes from 10 to 18 m a.s.l., where treeless Sphagnum fuscum bogs are abundant, while more or less mature concentric Kermi raised bogs begin to occur above that belt (18 m a.s.l. and above it). It has been hypothesized that unpatterned Sphag- num fuscum bogs on the coast of the Gulf of Both- nia represent younger stages of Kermi raised bogs (Kaakinen et al. 2008). As the wetland succession in general (Zweig & Kitchens 2009), the succession of flark aapa mires FENNIA 194: 1 (2016) 113Ecological, topographic and successional patterns may have multiple pathways created by hydrology and other factors. On air photos, the minerotroph- ic lawn-dominated peripheral part in the western side of Ulkusuo mire (number 35) (22 m a.s.l.) (Fig. 1, 7) seems a successional counterpart to the pat- terned sloping bog with Kermis in the western side of Iso Heposuo mire at the altitude of 60 m a.s.l., two km north of the Nyby study area. This example of a successional stretch implies that an area up to an altitude about 60 m a.s.l. in the lowland around Nyby, forms a successional belt, in which mire sys- tems, as called by Heikkilä et al. (2001) (see also Laitinen et al. 2007), are so far only forming. We conclude that two different trajectories character- ize evolving lawn-flark aapa mires (Laitinen et al. 2007; Eurola et al. 2015) represented by Ulkusuo, and the trajectory of the central basins seems pri- mary while that of the peripheral parts seems sec- ondary, because the latter trajectory is probably mainly associated with the mire complex parts, which are results of the lateral site expansion of mire complexes (Bauer et al. 2003; Rehell et al. 2012a, 2012b). The trajectory of the aapa-mire pe- ripheral parts (peripheral lobes, Laitinen et al. 2007) is characterized by a slow process of om- brotrophication (Tahvanainen 2011), while actual bogs (as complex parts of evolving mire systems) are only formed in hydrologically most beneficial sites at evident catchment divides. Conclusion The results of this study highlight two general points in boreal peatland succession. One, the sizes of bedrock basins and the sizes of their catch- ment areas affect the peatland succession so that partly different succession sequences may occur in areas with small mire basins and in areas with larger mire basins. Two, the locations of mire ba- sins either in the peripheral or central parts of larg- er catchment areas also affect the peatland trajec- tories. Additionally, there are some peculiar fea- tures in Nyby related to wetland succession. First- ly, only stretches of successional sequences can be shown. The circumstance is caused by the coastal topography with various sub-areas in rugged bed- rock terrain. Instead, the Ryöskäri till area and the Hailuoto sand area in the same lowland at the Bothnian Bay (Rehell et al. 2012a, 2012b) show uniform sequences of evolving aapa mires in topo- graphically uniform beds. Secondly, the highly scarce rich fens of Nyby confine to high altitudes in the lowland and represent mire expanse vegeta- tion. In Ryöskäri, instead, occur also rich fens with mire margin vegetation at low altitudes. Thirdly, the spruce mire influence (Bruchmoorigkeit, Ru- uhijärvi 1960) and especially the groundwater in- fluence (Quelligkeit, Ruuhijärvi 1960) appear to a lesser extent in Nyby, perhaps partly relating to the bedrock quality and to the abundance of rock out- crops and a shallow till layer in Nyby. Our research does not highlight diversity chances along succes- sion or along increasing altitudes generally in the lowland. 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