Artikkelit jotka sisältää sanan 'succession'

Although carbon (C) gas exchange during the summer largely determines the annual C balance of mires, the wintertime fluxes cannot be ignored. Decomposition continues as long as the soil is not frozen and a proportion of the gases produced during summer are also released during winter. We measured carbon dioxide (CO2) and methane (CH4) fluxes along a successional mire sequence during two winters following growing seasons with divergent weather conditions. We studied the successional trends in wintertime C release in boreal mires, and quantified the contribution of wintertime C fluxes to annual fluxes. Wintertime CO2 and CH4 fluxes from the successional mire sequence were related to the flux rates during the previous summer. Average winter CO2 release along the successional sequence varied between 19.5 and 44.9 g CO2-C m–2 winter–1(6-months), and accounted for 8–14% of the annual CO2 release. There was no clear successional trend in CO2 fluxes. Average winter CH4 release along the successional sequence varied between 0.20 and 7.29 CH4-C g m–2 winter–1(6-months).The winter CH4 fluxes accounted for up to 38% of the annual CH4 emissions. Occasional CH4 uptake was detected at the younger successional stages during winter following the dry summer, while after the wet summer all sites emitted CH4. In general, most of the winter C losses were composed of CO2.

• Leppälä, Mirva Leppälä, Finnish Forest Research Institute, FIN-91500 Muhos, Finland. Current address: Metsähallitus, Natural Heritage Services Ostrobothnia, BOX 81, FI-90101 Oulu, Finland, email: mirva.leppala@metsa.fi Sähköposti: ei.tietoa@nn.oo
• Laine, Sähköposti: ei.tietoa@nn.oo
• Tuittila, Sähköposti: ei.tietoa@nn.oo

Maankohoamisesta johtuvan rannansiirtymisen tuloksena on Perämeren rannikolle syntynyt aapasoiden nuorista kehitysvaiheista koostuvia sukkessiosarjoja. Ne ovat ekologisesti ja tieteellisesti arvokkaita ekosysteemejä, jotka ovat ainutlaatuisia maailmassa. Näiden soiden ekologiaa ja nykyistä tilaa on kuitenkin tutkittu verrattain vähän. Tämän tutkimuksen tavoitteena oli tuottaa tietoa aapasoiden nuorten kehitysvaiheiden suojeluarvon ja niiden säilymiseen liittyvien uhkien arviointiin ja selvittää soistumiseen liittyviä syitä sekä kasvillisuuden ekologisten vaihtelusuuntien ilmenemistä hydrologialtaan erilaisissa osissa suoaltaita. Tässä tutkimuksessa esitetään tuloksia nuorten (alle 2000 vuotta), luonnontilaisten aapasoiden määrän arvioinnista ja niiden kasvillisuuskartoituksesta kahdelta laajimmalta yhtenäiseltä aapasoiden sukkessiosarja-alueelta Perämeren rannikolla. Alueista toisen maaperä on moreenivaltainen ja toisen hiekkavaltainen. Tulokset osoittivat, että aapasoiden kehitysvaiheissa on suuri osa lettomaisia ja keskiravinteisia nevoja ja vain hyvin rajallinen määrä rahkasammalten kasvusta eroaa rämeiden sukkession alkuvaiheiden kehityksestä. Aapasoiden sukkessiosarjat ulottuvat koko valuma-alueen soistumiseltaan useiden satojen hehtaarein alueelle. Hydrologialtaan erilaiset valuma-alueen osat kehittyvät yhdessä muodostaen yhden kokonaisuuden. Vedenjakajien tuntumassa primääristä soistumista ilmenee pienien painanteiden ja lampien soistumisena, missä rahkasammalten kasvu painanteiden yli on hyvin nopeaa. Valuma-alueen alajuoksun osissa primääristä soistumista tapahtuu laajoilla märillä luhdilla, jossa veden virtaus on voimakasta. Myöhempi suon kehitys, jossa tapahtuu mm. ympäröivien kangasmetsien soistumista näyttää johtavan aapasuokompleksin muodostumiseen, jossa reunaosat ovat rahkasammalen vallitsemia ja keskusosat rimpipintaisia. Tulokset osoittavat, että nuorten aapasoiden suojelussa olisi olennaista kiinnittää huomiota soistuvien valuma-alueiden hydrologian säilyttämiseen. Valitettavasti hyvin harvat tällaisista valuma-alueista ovat enää nykyisin luonnontilaisia.

• Rehell, Sakari Rehell, Metsähallitus, luontopalvelut, PL 81, FI-90101, Oulu, Finland. e-mail: sakari.rehell@metsa.fi Sähköposti: ei.tietoa@nn.oo
• Heikkilä, Sähköposti: ei.tietoa@nn.oo

We investigated long-term dynamics of phosphorus (P) in ground vegetation, tree stand biomass and litterf all in two undrained and four drained oligotrophic pine fens in southern Finland. The study sites, which encompassed observation periods up to six decades after drainage, were chosen to form a chronosequcncc of sites initially similar floristically, showing different stages of the forest succession induced by drainage. The pattern of P allocation to above- and below-ground plant biomass followed the changes in growth form dominance from mosses, graminoids and shrubs to trees. Overall, net vascular plant uptake of P increased after drainage and remained on a higher level compared to that in the pristine fen. The amount of P in the drained ecosystem seems to remain high enough to support the uptake and continuing forest succession.

• Laiho, Peatland Ecology Group, Department of Forest Ecology, University of Helsinki, P.O. Box 27, FI-00014 Helsinki University, Finland Sähköposti: ei.tietoa@nn.oo
• Penttilä, Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo
• Laine, Sähköposti: ei.tietoa@nn.oo

The occurrence of raw humus layer and its relationship to the structure of the vegetation and the environmental variables were studied on 501 sample plots located systematically in drained peatland forests. The drainage had been done in the 1930s – 60s. The correlation between the amount of raw humus and the two-dimensional GNMDS (global nonmetric multidimensional scaling) ordination space was 0.57. The thickness of the raw humus layer increased in the direction of the drainage succession gradient. The correlations between the thickness of the raw humus and the measured environmental variables were weak. The strongest correlation was with the stand volume (0.31) and the drainage age (0.21). Weakness of these correlations was most probably due to the regressive succession on many plots. On average, the raw humus layer was thickest , 6.5 cm, in Vaccinium vitis-idaea transformed type I (developed from genuine forested mires) and 5.4 cm in type II (developed from treeless or composite types). In Vaccinium myrtillus types the corresponding mean thickness was 5.2 cm (I) and 3.2 cm (II) and in dwarf-shrub types 3.3 cm (I) and 4.6 cm (II). The secondary succession is slower and the amount of the needle litter (of Pinus sylvestris) smaller in the dwarf-shrub type than in the V. vitis-idaea type. In the V. myrtillus type the origin of the litter is more dominated by deciduous trees, the decomposition faster and the coverage of Pleurozium schreberi clearly smaller than in the nutrient-poorer types. P. schreberi tolerates the litterfall well and together with especially conifer litter, and maybe with slow decaying fine roots, too, it forms a loose raw humus layer on old drained peatlands. Being a poor germination bed, the raw humus makes successful stand regeneration difficult.

• Saarinen, The Finnish Forest Research Institute, Parkano Research Station, Kaironiementie 54, FIN-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo
• Hotanen, Sähköposti: ei.tietoa@nn.oo

Black spruce (Picea mariana, (Mill.) B.S.P.) has been traditionally managed as evenaged stands with artificial or natural regeneration on peatlands of northern Ontario Clay Belt region. However, lack of resources to make artificial regeneration on all clear-cuts and harvest methods unfavorable for natural regeneration often resulted in unsatisfactory regeneration. As a consequence, alternative management methods have been introduced for peatland black spruce, and this literature review discusses studies of these methods. In natural stands, both evenaged and uneven-aged structures may be found, while the second-growth stands originating from old horse-logging are mostly uneven-aged, with abundant advance growth. Currently, mechanized harvest with regeneration protection has been shown to sufficiently preserve residual trees and subsequently produce stands that are heterogeneous with respect to the size structure. In second-growth stands, uneven-aged management can be implemented with minimum diameter limits determined from stand structure and cut-to-length harvesting. Such management perpetuates a stand structure appropriate for uneven-aged management. Simulation study has been made to estimate black spruce yield under uneven-aged management with varying cutting cycle and minimum diameter limit. It seems that in some peatland sites uneven-aged management is a possibility to manage black spruce.

• Hökkä, The Finnish Forest Research Institute, Rovaniemi Research station, P.O. Box 16, FIN-96301 Rovaniemi, Finland Sähköposti: ei.tietoa@nn.oo
• Groot, Sähköposti: ei.tietoa@nn.oo

Abstract: Understorey biomass and species composition were analyzed on six sites representing tall sedge pine fen at different stages of secondary succession caused by drainage for forestry. Two of the sites were undrained controls and the other sites had been drained 8 - 55 years earlier. Cyperaceous and herbaceous field layer was found to diminish permanently after drainage, whereas shrub and moss layers survived in the drainage succession in terms of biomass allocation although the species composition changed almost completely. On the oldest drained site the ground vegetation was dominated by typical upland forest species with the exception of Sphagnum russowii. Total understorey biomass varied from 260 g m-2 on sites drained 22-30 years earlier to 990 g m-2 on a site drained 8 years earlier. Key words: drainage, field layer, ground vegetation, moss layer, peatland, succession

• Laiho, Department of Forest Ecology, P.O.Box 24, FIN-00014 University of Helsinki, Finland Sähköposti: ei.tietoa@nn.oo

In this paper, the mire classification system and its development in Estonia are reviewed. In addition the utilization of mires for peat harvesting, forestry, agriculture and conservation are outlined. There are two main groups of mires in Estonia — an eastern and a western type. Mire vegetation has been classified according to site conditions, community composition and structure. During the primary succession of mire communities, a number of fen communities converge to a smaller number of bog communities. The post-drainage succession is also convergent. Estonian mires are intensively utilized for peat harvesting. There is a clear need for a comprehensive mire protection and utilization plan. Keywords: Classification, Estonia, nature conservation, succession, vegetation

• Zobel, Department of Botany and Ecology, Tartu University, Lai St. 40, Tartu, Estonia Sähköposti: ei.tietoa@nn.oo

The vegetation data from virgin and corresponding drained mire site types collected by Juhani Sarasto in the 1950's were reanalyzed using DCA and TWINSPAN. The main gradient in the material was a complex gradient called the mire margin-mire expanse -effect. During secondary succession, after forest drainage, the variation of mire site types diminished as the importance of hydrology decreased. The difference between the vegetation of treeless plus composite and forested mire site types could still be detected after the site types had reached the drained peatland forest type phase in their post-drainage succession. Keywords: Classification, ordination, succession

• Hotanen, The Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, SF-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo
• Vasander, Sähköposti: ei.tietoa@nn.oo

In Finland three different mire classification systems can be distinguished: 1) those for ecological purposes based on detailed botanical surveys, 2) those for scientific forestry research purposes, and 3) more extensive systems for practical forestry purposes. All systems are based upon Cajan-der's site-type principle whereby habitats which are ecologically similar are considered to support a similar vegetation. The classification (site type names, analogy/correspondence, nutrient status level) of spruce-pine mires and oligotrophic spruce mires according to the above-mentioned systems is compared. Some criticism concerning especially the confusing naming of the same type is presented. The varying post-drainage suc-cession in these site type groups is also discussed. Finally an attempt to distinguish the more oligotrophic spruce-pine mires from the less oligotrophic ones is made. Keywords: Drainage, mire classification, site type, succession, trophy

• Hotanen, The Finnish Forest Research Institute, Joensuu Research Station, P.O. Box 68, SF-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo

A review of the historical development of mire site classification in Finland with special emphasis on the studies and theories of post-drainage succession is made. Some criticism of the prevailing classification system is presented and a work model for guiding further study of drained mire classification is proposed. Preliminary results of a new approach to classify the vegetation of old peatland forests using TWINSPAN classification and DCA ordination techniques are presented. Keywords: Drainage, mire classification, site type, succession

• Reinikainen, The Finnish Forest Research Institute, Department of Peatland Forestry, P.O. Box 18, SF-01301 Vantaa, Finland Sähköposti: ei.tietoa@nn.oo

The aim of this research was to study how some species of mire plants with differing ecological characteristics react to environmental changes caused by drainage. The data has been collected from 254 sample plots, each 1 km2 in area, in the southern and middle part (60-66°N) of Finland during the years 1984-1986. The occurrence of each species was studied both in virgin and in drained peatlands, and the note about mire type and drainage succession stage were recorded. For cloudberry (Rubus chamae-morus), the abundance of vegetation and berries were also indicated. There is a clear decline in the appearance of sedge plants as the succession, caused by ditching proceeds. Of herbs, Athyrium filix-femina and Cirsium palustre, become more common after drainage, but the flark level species, Drosera anglica and Lysimachia thyrsiflora disappear. As the drainage proceeds there is a clear decline in the vegetation and berry production of cloudberry. On the most effectively drained peatlands, more than half of the observations of cloudberry vegetation and all the observations of berry produce, indicated scanty growth and crop. The most abundant vegetation and yield of berries occurred in virgin peatlands. Keywords: Drained mires, ground vegetation change, Rubus chamae-morus, succession

• Aapala, University of Oulu, Department of Botany, Linnanmaa, SF-90570 Oulu Sähköposti: ei.tietoa@nn.oo
• Kokko, Sähköposti: ei.tietoa@nn.oo