Suo - Mires and peat vol. 41 no. 4-5 | 1990

Petri Kärenlampi, Juha Suni. Motor-manual treatment of young stands on peatlands.
Avainsanat: peatlands; Ditches; nurse crop; terrain description; young stand treatment
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In connection with an Inter-Nordic research project concerning treatment of young forests, some aspects concerning peatlands were studied. A description of the difficulty of terrain and the importance of nurse crop were reviewed from the point of view of young stand treatment. A field experiment concerning the time needed to keep ditches free from slash was organized. Keywords: Ditches, nurse crop, peatlands, terrain description, young stand treatment
  • Kärenlampi, University of Helsinki, Department of Logging and Utilization of Forest Products, Unioninkatu 40 B, SF-00170 Helsinki Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Suni, Sähköposti: ei.tietoa@nn.oo
Juha Heiskanen. Näytelieriön täyttötavan vaikutus kasvuturpeen vedenpidätyskykyyn.
English title: The effect of sample handling on the water retention of growth peat substrate.
Avainsanat: water content; Compaction; matric potential; shrinkage
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The water retention of Sphagnum peat substrate as used in the production of containerized forest tree seedlings was determined at increasing matric potentials from saturation. Samples of commercially available peat substrate were taken and compressed to correspond to a wet bulk density of 0.2 g cm-3 — the value of the substrate used in practice in the nursery. The samples were saturated (-0.1 kPa) and the water content determined after applying successive matric potentials of -1, -10 and -100 kPa by means of a pressure plate apparatus. The effect of loosening the substrate was investigated, as was also the effect of applying the higher potentials directly to saturated samples. The volumetric water retention varied between 88-93% at -0.1 kPa, 72-85% at -1 kPa, 29-30% at -10 kPa and 18-25% at -100 kPa. Loosening the substrate between applying successively higher potentials to the same samples and, in the case of the higher potentials, determining retention directly from saturated samples gave the lower retention values. It was concluded that the most natural and practical way to determine water retention is to use the same samples, successively applying higher potentials without loosening between applications. Such a procedure includes the effect of increasing compaction and changes in pore size distribution of the substrate upon drying. Keywords: Compaction, matric potential, shrinkage, water content
  • Heiskanen, The Finnish Forest Research Institute, Suonenjoki Research Station, SF-77600 Suonenjoki, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
Martin Zobel. Maan happiolot soistuvissa havumetsissä.
English title: Soil oxygen conditions in paludifying boreal forest sites.
Avainsanat: Coniferous forest; oxygen conditions; paludification; suc­cession
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Soil oxygen conditions were characterized with the help of polycarbonate tubes, which were filled with water and inserted into the soil. The oxygen content of the water inside the tube was measured and compared with that in conditions of full aeration. Five forest sites were studied. Three of them form a moisture gradient — mesophyte spruce forest (MSF), paludifying spruce forest (PSF) and paludified pine forest (PPF). For comparison, three other sites were included: a dry pine forest (DPF), an alder carr mire (ACR) and an ombrotrophic bog. Soil aeration conditions were the most unfavourable at the PSF site at the beginning of June; the lowest values being recorded in depressions with Sphagnum girgensohnii. Considering the whole vegetation period, the bog site demonstrated the lowest soil aeration level. At the alder carr site, soil aeration conditions were dependent on precipitation. In forest sites the lowest aeration level was observed at the beginning of June, but in the ACR and bog sites, another minimum occurred in September after heavy rains. Keywords: Coniferous forest, oxygen conditions, paludification, succession
  • Zobel, Department of Botany and Ecology, Tartu University, Lai St. 40, Tartu 202400, Estonia Sähköposti: ei.tietoa@nn.oo (sähköposti)

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