Artikkelit kirjoittajalta Juha Heiskanen

Meeri Pearson, Markku Saarinen, Juha Heiskanen, Tytti Sarjala, Jukka Laine. Kasvualustan kuivumisen vaikutukset rahkasaraturpeeseen istutettujen männyntaimien ensikehitykseen.
English title: High and dry: Consequences of drought exposure in Scots pine seedlings grown in authentic peat soil.
Original keywords: männyntaimet; Pinus sylvestris; kuivuus; rahkasaraturve; fotosynteesin tehokkuus (Fv/ Fm); mykorritsat; polyamiinit; juurten ja versojen kasvu
English keywords: drought; Fv/Fm; mycorrhizal colonization; Pinus sylvestris seedlings; poly-amines; root and shoot growth; Sphagnum-Carex peat
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Should the frequency of drought increase in boreal forests due to climate change, seedlings planted in prepared peat mounds could become more susceptible to soil desiccation. The resistance of Scots pine (Pinus sylvestris L.) seedlings to drought will thus be a key factor in the regeneration success of pine-dominated, forestry-drained peatlands. In this study, we evaluated the physiological, metabolic, and morphological responses of year-old seedlings gradually exposed to extreme drought in highly decomposed Sphagnum-Carex peat blocks. Drought clearly suppressed root and shoot growth as well as fractional colonization of ectomycorrhizal fungi. Sustained declines in photochemical efficiency (Fv/Fm) of previous-year and current-year needles did not occur until the volumetric soil water content had dropped to 30% and 10%, respectively. Polyamine analysis revealed that new needles are preferred in protecting the different parts of the seedlings against drought stress. Despite growth losses, the maintenance of rather high photochemical efficiency in current-year needles under severe water stress would appear to indicate a potential for seedling recovery if water availability in the peat improved. Given the high tolerance exhibited by Scots pine seedlings, death by drought seems a lesser concern.
  • Pearson, Finnish Forest Research Institute, Parkano Research Unit, Kaironiementie 15, FI-39700 Parkano, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Saarinen, Sähköposti: ei.tietoa@nn.oo
  • Heiskanen, Sähköposti: ei.tietoa@nn.oo
  • Sarjala, Sähköposti: ei.tietoa@nn.oo
  • Laine, Sähköposti: ei.tietoa@nn.oo
Juha Heiskanen. Kasvualustana käytetyn heikosti maatuneen rahkataturpeen lämmönjohtavuus.
English title: Thermal conductivity of low-decomposed Sphagnum peat used as growth medium.
Avainsanat: water content; peat substrate; water retention; sandy soil; thermal soil properties
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The thermal conductivity of low-decomposed Sphagnum peat, used as a growth medium for container seedling production in tree nurseries, and of a sandy mineral soil was studied using the single thermal probe method in the laboratory. The thermal conductivity of the peat was low and decreased from 0.5 to 0.05 W m-1K-1 when the water content decreased from near saturation to air-dry. In comparison, the thermal conductivity of the sandy soil was much higher, decreasing steeply from 1.5 to 0.5 W m-1K-1 with decreasing water content. Results are in accordance with those reported earlier for similar media. The results suggest markedly weaker and more delayed temperature fluctuations in pure peat media compared with media containing mineral soil, which is in agreement with observations made in tree nurseries.
  • Heiskanen, Finnish Forest Research Institute, Juntintie 40. FIN-77600 Suonenjoki, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
Antti Wall, Juha Heiskanen. Metsitettyjen turvepeltojen maan fysikaaliset ominaisuudet.
English title: Physical properties of afforested former agricultural peat soils in western Finland.
Avainsanat: Bulk density; organic matter; water retention; peat fields; soil aeration
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The bulk density, organic matter content and soil water-retention characteristics of twenty-one afforested former agricultural peat soils were studied. Soil samples were collected from 5-10 cm, 15-20 cm, 25-30 cm and 35-40 cm soil layers. The studied soils' physical properties differed from those of undrained peatlands and peatlands drained for forestry mainly due to the mixing of mineral soil with the peat during cultivation. In the case of thick peat soils (peat layer >30 cm), the bulk density was at a maximum (0.37 g cm-3) and the organic matter content at a minimum (54%) in the uppermost soil layer. In the case of shallow peat soils (peat layer <30 cm), bulk density increased and organic matter content decreased with increasing soil depth. In thick peat soils, total porosity and water retention at selected matric potentials were at their highest in the lowermost soil layer while in shallow peat soils, the uppermost soil layer possessed the highest total porosity and water retention. Most of the water was retained within the range -100 to -1500 kPa in both soil types. This indicated that small pores were predominant. Air-filled porosity at -10 kPa matric potential (about field capacity) was, on average, 16% in thick peat soils and 17% in shallow peat soils in the uppermost soil layer and decreased with increasing soil depth. The results suggest that the physical properties were generally rather unfavourable for adequate soil aeration and water availability as needed for satisfactory tree growth.
  • Wall, Finnish Forest Research Institute, Kannus Research Station, Box 44, FIN-69101 Kannus, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Heiskanen, Sähköposti: ei.tietoa@nn.oo
Risto Rikala, Juha Heiskanen. Turpeen puristenesteen sähkönjohtavuuden riippuvuus vesipitoisuudesta.
English title: Relationship between electrical conductivity and water content in peat growth medium.
Avainsanat: fertilization; nutrient monitoring; TDR
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The relationship between electrical conductivity (EC) of press-water extract and water content (WC) of peat growth medium at desorption was studied. A simple time-domain reflectometer (TDR), traditional laboratory conductivity meter and gravimetric weighing were used to measure EC and WC. The relationship between EC values measured with a laboratory conductivity meter from press-water extract and those measured with TDR directly from peat medium was curvilinear. The relationship between WC of peat measured with TDR and that determined gravimetrically, although nearly linear, was slightly sigmoidal. Empirical curve between EC values and WC values measured with TDR was close to the theoretical curve, which was calculated on the basis of increase in ion concentration at desorption. Transformed EC values of press-water extract were higher than the theoretically calculated values. For comparison of EC values measured from press-water extracts in various water contents, transforming coefficients were derived. Key words: nutrient monitoring, fertilization, TDR
  • Rikala, The Finnish Forest Research Institute, Suonenjoki Research Station, FIN-77600 Suonenjoki, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
  • Heiskanen, Sähköposti: ei.tietoa@nn.oo
Juha Heiskanen. Turvepohjaisten kasvualustojen tiivistyminen yksivuotisessa paakkutaimikasvatuksessa.
English title: Compaction of growth media based on Sphagnum peat during one-year culturing of container seedlings.
Avainsanat: shrinkage; nursery management; soil physical properties; substrate; water retention
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Changes in bulk density and water retention during one-year culturing of container seedlings were studied in pure, low-humified Sphagnum peat and in peat-based two-component growth media. In all growth media, the bulk density increased slightly with time. The corresponding decrease in total porosity was negligible (< 1 %-unit for pure peat). At matric potentials < -1 kPa, water retention of growth media tended to increase somewhat with time. On the other hand, shrinkage at desorption decreased during seedling culturing. The results suggest that, from the standpoint of seedling growth, the structure of growth media based on Sphagnum peat does not markedly change or deteriorate during one-year culturing of seedlings. However, in seedling culturing peat growth media containing hydrogel may possess restricted aeration due to excess water retention, while addition of coarse textured materials, such as perlite, to peat can increase aeration. Key words: nursery management, soil physical properties, shrinkage, substrate, water retention
  • Heiskanen, The Finnish Forest Research Institute, Suonenjoki Research Station, FIN-77600 Suonenjoki, Finland Sähköposti: ei.tietoa@nn.oo (sähköposti)
Juha Heiskanen. Kaksiosaisten turvepohjaisten kasvualustojen vaikutus männyn paakkutaimien kasvuun.
English title: Effect of peat-based two-component growth media on the growth of containerized scots pine seedlings.
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One-year-old containerized scots pine seedlings (Pinus sylvestris L.) were grown in two-component growth media mixtures containing 75% (by volume) light, low humified Sphagnum peat and under an irrigation regime where the seedlings were abundantly reirrigated after -10 to -15 kPa matric potential was achieved in the growth media. The greatest seedling growth was in pure peat and in peat to which coarse perlite had been added. The poorest growth was in mixtures of peat and hydrogel and of peat and water repellent rockwool. Intermediate growth was found in peat to which fine perlite or water absorbent rockwool had been added. During drying in the range -2 to -90 kPa matric potential of the growth medium, the decrease in the net photosynthesis of seedlings at the bud formation phase was linear when aeration was not a restricting factor. During drying, the net photosynthesis was relatively large and was of a similar magnitude in pure peat and in peat to which coarse or fine perlite had been added. Significantly smaller net photosynthesis was observed in peat to which water repellent rockwool or water absorbent rockwool or hydrogel had been added. During drying under wet conditions (-1 to -4 kPa matric potential) when limited aeration was a restricting factor, the net photosynthesis increased linearly. Due to better aeration, the, net photosynthesis was higher in the mixture of peat and coarse perlite than in pure peat. Keywords: aeration, nutrients, photosynthesis, physical properties of soil, substrate, water retention J. Heiskanen, The Finnish Forest Research lnstitute, Suonenjoki Research Station, FIN-77600 Suonenjoki, Finland
  • Heiskanen, Sähköposti: ei.tietoa@nn.oo (sähköposti)
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)

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