Suo - Mires and peat vol. 49 no. 3 | 1998

Risto Lauhanen, Marja-Leena Piiroinen, Timo Penttilä, Eero Kolehmainen. Kunnostusojitustarpeen arviointi Pohjois-Suomessa.
English title: Evaluation of the need for ditch network maintenance in northern Finland.
Avainsanat: forest drainage; ditch cleaning; complementary drainage; tree stand; stand growth; decision making
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Factors affecting the need for ditch network maintenance in northern Finland were studied. In addition, the effect of ditch network maintenance on stand growth was estimated. A dataset containing ditch, tree stand, site type and climate variables was built up on the basis of the permanent sample plots (SINKA) on peatlands. Regression analysis as well as discriminant analysis were used to identify factors and criteria that could be used to identify sites that would respond to ditch network maintenance. Instead of the ditch condition class, ditch age and depth proved to be the variables reflecting the need for ditch network maintenance. The volume of the tree stand was influenced the most by the temperature sum and age of ditching. Stand volume growth was influenced the most by the volume of the tree stand. The site type index or the volume of the tree stand did not give useful information for the planning of ditch network maintenance. When ditch age was 10-40 years, complementary ditching increased annual stand growth of pine mires by 0.6-1.0 and 1.5-1.9 m3 ha-1 a-1 on spruce-birch swamps.
  • Lauhanen, The Finnish Forest Research Institute, Parkano Research Station, FIN-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Piiroinen, Sähköposti: ei.tietoa@nn.oo
  • Penttilä, Sähköposti: ei.tietoa@nn.oo
  • Kolehmainen, Sähköposti: ei.tietoa@nn.oo
Leena Hytönen, Jukka Aarnio. Kunnostusojituksen erilliskannattavuus muutamilla karuhkoilla rämeillä.
English title: Profitability of ditch-network maintenance on some oligotrophic pine mires.
Avainsanat: forest drainage; Scots pine; internal rate of return; net present value
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The paper presents the results of a study to assess the profitability of ditch-network maintenance on some oligotrophic pine mires. The alternative ditch-network maintenance methods compared were: ditch cleaning, complementary ditching, and ditch cleaning and complementrary ditching combined. Nine drained pine-dominated mires were chosen for investigation. Only the ditch-network maintenance costs were included in the calculations. Profitability was calculated for two cases: 1) the forest owner pays all the costs and 2) he obtains the maximum state grant. Without the state grant ditch-network maintenance provided a net present value of 870 FIM ha-1 with a 3 % rate of interest, of 220 FIM ha-1 with the 5 % rate of interest, and on internal rate of return of 5 %. With the state grant the results were: 1620 FIM ha-1, 970 FIM ha-1 and 10%, respectively. The conclusions were that in most cases ditch-network maintenance is profitable even without state grant. By using 3 % and 5 % interest rates, the complementary ditching and combination provided similar profitability, specially when the state grants were provided. Using the IRR criterion, the complementary ditching provided the best profit.
  • Hytönen, Finnish Forest Research Institute, Kannus Research Station, P.O. Box 44, FIN-69101 Kannus, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Aarnio, Sähköposti: ei.tietoa@nn.oo
Markku Saarinen, Timo Silver, Samuli Joensuu. Ojien mitoitus kunnostusojituksessa. Kirjallisuustarkastelu.
English title: Ditch dimensioning in ditch-network-maintenance areas. A literature review.
Avainsanat: peatlands; ditch network maintenance; drainage areas
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Drainage of pristine mires has been discontinued in Finland and now drainage activity focuses on remedial treatment of old ditch networks on transformed drained mires. In the era of first-time drainage, uniform regulations were applied in the dimensioning of ditches. Also the current national recommendations pertaining to remedial drainage and the dimensioning of ditches corresponds to the old regulations applied in first-time drainage. However, regional organizations have their own directives, and accordingly ditch depths show considerable regional variation. The purpose of this paper is to look for answers to questions which have arisen already some years ago, especially among practitioners responsible for forest-improvement works in non-industrial, private woodlots: Can the service life of ditch networks be increased by means of ditches which are deeper than those implemented at the time of first-time drainage and will this also result in a reduced impact on water ecosystems by reducing the number of remedial actions needed ? Is ditch depth in old, well-stocked drainage areas a more important factor than ditch spacing in controlling the drainage depth?
  • Saarinen, The Finnish Forest Research Institute, Parkano Research Station, Kaironiementie 54, FIN-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Silver, Sähköposti: ei.tietoa@nn.oo
  • Joensuu, Sähköposti: ei.tietoa@nn.oo

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