Suo - Mires and peat vol. 47 no. 2 | 1996

Raija Laiho. Vedenpinnan alenemisen vaikutus sararämeen pintakasvillisuuden biomassaan ja lajistoon.
English title: Changes in understorey biomass and species composition after water level drawdown on pine mires in southern Finland.
Avainsanat: Drainage; peatland; succession; ground vegetation; field layer; moss layer
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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 (sähköposti)
Jyrki Kangas, Risto Lauhanen. Kunnostusojitusvaihtoehtojen vesistövaikutusten asiantuntija-avusteinen arviointi ja liittäminen päätösanalyysiin.
English title: Assessing the impacts of ditch network maintenance on water ecosystems on the basis of expert knowledge and integrating the assessment into decision analysis.
Avainsanat: environmental protection; AHP; Delphi; ditch network maintenance; forest planning
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Abstract: The study applies the combined use of the Delphi technique and the analytic hierarchy process to the assessment of ditch network maintenance alternatives and their impacts on water ecosystems. The results of the assessment are utilised in multi-criteria decision support. Impacts of ditch network maintenance on water systems need to be assessed on the basis of expert knowledge, because no quantitative impact assessment models applicable in numerical decision analyses are available. Ideally, the assessment process results in a compromise between the opinions of several experts involved. If no consensus can be reached, the final results are calculated as weighted means of the opinions. For the weighting stage, the competence of the experts should be determined. The method is illustrated and tested in the light of a case study where five experts assessed five ditch network maintenance alternatives with respect to the protection of nearby water ecosystems. The case study area is located in western Finland. It is a peatland site with an old ditch network needing maintenance from the viewpoint of wood production. With the volume increment of the tree stand and the protection of water systems as the criteria, and utilising ecological expertise in the assessment of alternatives concerning the protection criterion, multi-criteria analysis recommended the 'no treatments' alternative. Key words: AHP, Delphi, ditch network maintenance, environmental protection, forest planning
  • Kangas, The Finnish Forest Research Institute, Kannus Research Station, P.O.Box 44, FIN-69101 Kannus, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Lauhanen, Sähköposti: ei.tietoa@nn.oo
Hans Gustav Gustavsen. Pituusboniteettisovellus ojitusalueiden metsille.
English title: Site index model approach for drained peatland forest stands.
Avainsanat: Drainage; growth and yield; site classification
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The site index system presented is intended as support for the idea of developing a more hierarchical and integrated forest classification system in Finland. The data used were obtained from stands growing on old permanent experimental plots laid out in drainage areas in southern Finland. The model, describing the post-drainage development of stand dominant height as a function of drainage age (time elapsed since drainage), is based on successive measurement data (465 observations), collected from 89 plots, each representing a single stand. The site indices H40dr are post-drainage dominant height values 40 years since drainage, given in 2-meter classes. Post-drainage dominant height is defined as the difference between the current dominant height and the dominant height at the time of drainage. In classification work, one needs to know (or measure) the two aforementioned height characteristics, together with age since drainage. If the dominant height at the time of drainage is not known, it can be estimated from a function presented herein and based on current dominant height and drainage age. The mean annual volume increments at 40 years since drainage (MAI40) are also presented. There is still a need for examining separately the accuracy of the model with new data from spruce-, pine- and birch-dominated stands, collected for numerical constructions of site index curves. Therefore, the site index model and its characteristics must be seen more as outlines than as a final system for practical application. A well-functioning ditch network is a default when applying the site index curves.
  • Gustavsen, The Finnish Forest Research Institute, Joensuu Research Station, P.O.Box 68, FIN-80101 Joensuu, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)

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