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Articles by Pekka Saranpää

Category: Research article

article id 248, category Research article
Tuula Jyske, Harri Mäkinen, Pekka Saranpää. (2008). Wood density within Norway spruce stems. Silva Fennica vol. 42 no. 3 article id 248. https://doi.org/10.14214/sf.248
We studied the variation in average wood density of annual rings, earlywood density, and latewood density in addition to ring width and latewood percentage within Norway spruce (Picea abies (L.) Karst.) stems from the pith to the bark, and from the stem base towards the stem apex. Moreover, the variation in wood density within annual rings was studied at the different heights and radial positions in the stem. The material consisted of 85 trees from central and south-eastern Finland. Variation between the annual rings accounted for 11–27% of the total variation in wood density. Only small differences (3–6%) in wood density were found between different heights in the stem. The largest (49–80%) variation in wood density was found within the annual rings. The difference in wood density between earlywood and latewood was smaller in the rings near the pith than in the outer rings. The increasing wood density from the pith outwards was related to increasing latewood density and latewood percentage, whereas the earlywood density increased only slightly from the pith outwards. In a given cambial age (i.e., given rings from the pith), the average wood density of annual rings increased with increasing stem height. In contrast, in the rings formed in the same calendar years (i.e., given rings from the bark), the average wood density of annual rings decreased with increasing stem height. The results of this study verify our knowledge of wood density variation and can further contribute to creating models to predict wood density.
  • Jyske, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: tuula.jyske@metla.fi (email)
  • Mäkinen, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Saranpää, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
article id 301, category Research article
Sanni Raiskila, Minna Pulkkinen, Tapio Laakso, Kurt Fagerstedt, Mia Löija, Riitta Mahlberg, Leena Paajanen, Anne-Christine Ritschkoff, Pekka Saranpää. (2007). FTIR spectroscopic prediction of Klason and acid soluble lignin variation in Norway spruce cutting clones. Silva Fennica vol. 41 no. 2 article id 301. https://doi.org/10.14214/sf.301
Our purpose was to develop a FTIR spectroscopic method to be used to determine the lignin content in a large number of samples and to apply this method studying variation in sapwood and heartwood lignin content between three fast-growing cutting clones grown in three sites. Models were estimated with 18 samples and tested with 6 samples for which the Klason lignin + acid soluble lignin content had been determined. Altogether 272 candidate models were built with all-subset regressions from the principal components estimated from differently treated transmission spectra of the samples; the spectra were recorded on KBr pellets of sieved and unsieved unextracted wood powder and subjected to four different preprocessings and two different wavenumber selection schemes. The final model showed an adequate fit in the estimation data (R2 = 0.74) as well as a good prediction performance in the test data (R2P = 0.90). This model was based on the wavenumber range of 1850–500 cm–1 of the line-subtraction-normalised spectra recorded from sieved samples. The model was used to predict lignin content in 64 samples of the same material. One of the clones had a slightly lower sapwood lignin content than the two other clones. The fertile growing site with fast growing trees showed slightly higher sapwood lignin content compared with the other two sites. The model was also used to predict the lignin content in the earlywood of 45 individual annual rings. Variation between individual stems and between annual rings was found to be large. No correlation was found between the lignin content and density of earlywood.
  • Raiskila, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Pulkkinen, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Laakso, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Fagerstedt, Department of Biological and Environmental Sciences, Plant Biology, P.O. Box 65, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Löija, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Mahlberg, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Paajanen, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Ritschkoff, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Saranpää, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: pekka.saranpaa@metla.fi (email)
article id 341, category Research article
Sanni Raiskila, Pekka Saranpää, Kurt Fagerstedt, Tapio Laakso, Mia Löija, Riitta Mahlberg, Leena Paajanen, Anne-Christine Ritschkoff. (2006). Growth rate and wood properties of Norway spruce cutting clones on different sites. Silva Fennica vol. 40 no. 2 article id 341. https://doi.org/10.14214/sf.341
The effect of growth rate on weight density and strength properties of three Norway spruce cutting clones growing on three different sites in different geographic locations was studied. The purpose was to follow variation in wood physical and mechanical properties and in quality between fast-growing clones grown in environments differing in nutritional and soil properties and climate within the boreal zone. The cloned trees had been selected on grounds of good growth, health and quality. The cuttings were collected from three-year-old seedlings and rooted. The rooted cuttings were planted in the 1970’s and they were on average 26 years old at a time of felling. The variation of weight density was studied within the annual ring and within the stem between the juvenile and mature wood from the pith to the bark with an X-ray densitometric method. The average annual ring width (and latewood proportion, %) varied between the clones from 2.92±1.36 mm (15.34%) to 3.30±1.25 mm (11.80%) and between the sites from 2.76±1.07 mm (14.71%) to 3.70±1.22 mm (13.29%). The mean weight density was 0.461±0.077 g cm–3 and latewood density 0.750±0.125 g cm–3 in this material. The mean modulus of elasticity was 9.88±1.43 GPa, modulus of rupture 67.51±11.50 MPa and weight density of the test samples (ρ12) 414±44 kg m–3 in mature wood. The parameters studied showed clearly that the environment had a large effect while the three clones differed from each other similarly in the different sites, e.g. the fastest growing clone was fastest on all sites.
  • Raiskila, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Saranpää, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: pekka.saranpaa@metla.fi (email)
  • Fagerstedt, Department of Biological and Environmental Sciences, Plant Biology, P.O. Box 65, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Laakso, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:
  • Löija, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Mahlberg, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Paajanen, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:
  • Ritschkoff, VTT Building and Transport, P.O. Box 1806, FI-02044 VTT, Finland ORCID ID:E-mail:

Category: Article

article id 5228, category Article
Pekka Saranpää. (1985). Kontortamännyn runkopuun trakeidien pituuden, halkaisijan ja soluseinän paksuuden vaihtelu. Silva Fennica vol. 19 no. 1 article id 5228. https://doi.org/10.14214/sf.a15407
English title: Length, diameter and cell wall thickness of tracheids in mature lodgepole pine bole wood.

Variation in tracheid morphology were examined for the bole wood of lodgepole pine (Pinus contorta Douglas ex Loudon) grown in Southern and Central Finland. Tracheid lengths were examined in a fast-grown and in slow-grown trees from three stands. Tracheid length increased with increasing height to 4–8 metres and decreased after that, and increased also with increasing age from the pith. The variation between stems was high. The shortest tracheids were about 1.11 mm near the piths and the longest about 4.10 mm near the bark.

Tracheid diameter and cell wall thickness were measured for the total number of 16 stems from Southern and Central Finland. Tracheid diameter increased with increasing distance from pith and the largest tracheids were at a height of 4–8 metres. Cell wall thickness varied independently of height in the stem. Summerwood cell wall thickness was twice that of springwood. There was a difference of 0.6 μm in springwood and 1.0 μm in summerwood double cell wall thickness between the two stands. Cell wall percentage was 29±4.7 in springwood and 69±7.3 in summerwood.

The PDF includes a summary in English.

  • Saranpää, ORCID ID:E-mail:
article id 5199, category Article
Pekka Saranpää. (1983). Puuaineen tiheyden ja vuosiluston leveyden vaikutus kuusen iskutaivutuslujuuteen Etelä- ja Pohjois-Suomessa. Silva Fennica vol. 17 no. 4 article id 5199. https://doi.org/10.14214/sf.a15182
English title: The influence of basic density and growth ring width on the impact strength of Norway spruce wood from Southern and Northern Finland.

Basic density and absorbed energy in impact bending were measured for 500 Norway spruce (Picea abies (L.) H. Karst.) samples from Northern and Southern Finland. Statistical analysis showed that the relationship between impact strength and basic density was significant and regression analysis showed that it was linear.

Furthermore, with constant density, the impact strength was higher in Northern than in Southern Finland. This was due to growth ring width: i.e. when density was kept constant the impact strength increased with decreasing growth ring width. In addition, when the growth ring width was kept constant, the basic density of wood was higher in Southern Finland than in Northern Finland.

The PDF includes a summary in English.

  • Saranpää, ORCID ID:E-mail:

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