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Silva Fennica 1926-1997
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Acta Forestalia Fennica
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Articles by Pekka Nygren

Category: Editorial

article id 10411, category Editorial
Pekka Nygren. (2020). Improvement of reproducibility and research transparency in Silva Fennica. Silva Fennica vol. 54 no. 3 article id 10411. https://doi.org/10.14214/sf.10411
  • Nygren, Finnish Society of Forest Science, Viikinkaari 6, FI-00790 Helsinki, Finland ORCID ID:E-mail: pekka.nygren@metsatiede.org (email)

Category: Research article

article id 450, category Research article
Miaoer Lu, Pekka Nygren, Jari Perttunen, Stephen G. Pallardy, David R. Larsen. (2011). Application of the functional-structural tree model LIGNUM to growth simulation of short-rotation eastern cottonwood. Silva Fennica vol. 45 no. 3 article id 450. https://doi.org/10.14214/sf.450
The functional-structural tree growth model LIGNUM was developed as a general research tool that can be applied to several tree species. The growth simulation of short-rotation eastern cottonwood (Populus deltoides Bartr. ex Marsh.) inherits the basic LIGNUM modeling concepts including modular tree structure, L-system-based description of structural development, and carbon budget. New developments of LIGNUM model in this study were the incorporation of a biochemically-derived photosynthesis submodel; nested time steps for simulating physiological processes, structural development, and annual biomass production; incorporation of field-measured weather data for modeling the response of physiological processes to environmental variation; and application of a Monte-Carlo voxel space submodel for simulating the stochasticity of tree growth and improving computational efficiency. A specific parameter system was applied for modeling P. deltoides growth in the central Missouri, USA, environment. This adaptation of LIGNUM was applied on modeling growth of P. deltoides in a short-rotation agroforestry practice. The simulated height and biomass growth were close to field observations. Visualization of simulation results closely resembled the trees growing in an open site. The simulated response of tree growth to variations in photon flux input was reasonable. The LIGNUM model may be used as a complement to field studies on P. deltoides in short-rotation forestry and agroforestry.
  • Lu, Deparment of Forestry, University of Missouri, Columbia, MO, USA ORCID ID:E-mail:
  • Nygren, The Finnish Society of Forest Science, P.O. 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: pekka.nygren@metla.fi (email)
  • Perttunen, Finnish Forest Research Institute, Vantaa, Finland ORCID ID:E-mail:
  • Pallardy, Deparment of Forestry, University of Missouri, Columbia, MO, USA ORCID ID:E-mail:
  • Larsen, Deparment of Forestry, University of Missouri, Columbia, MO, USA ORCID ID:E-mail:
article id 252, category Research article
Tuomo Kalliokoski, Pekka Nygren, Risto Sievänen. (2008). Coarse root architecture of three boreal tree species growing in mixed stands. Silva Fennica vol. 42 no. 2 article id 252. https://doi.org/10.14214/sf.252
Root system architecture determines many of the vital functions of a tree, e.g. stability of anchorage and resource uptake. The shoot:root ratio is determined through the allocation of resources. Studies on below-ground architectural elements in boreal mixed forests are relatively scarce despite the fact that knowledge on below-ground interactions and allocation changes in relation to stand developmental stage and soil fertility is needed both in ecological and silvicultural research. In this study, sixty tree root systems of three different tree species, Betula pendula, Picea abies and Pinus sylvestris, were excavated in five mixed forest stands in order to quantify differences between the species and sites in terms of rooting behaviour. Root architecture differed greatly between the species, implying different solutions for the functions of root systems. Half of the P. sylvestris had developed a taproot as a response to anchorage needs, while P. abies correspondingly had pronounced secondary growth of proximal roots. Betula pendula had the most extensive root system, illustrating the greater demand of deciduous trees for water. Betula pendula was also the most sensitive to soil fertility: it favoured exploration on the poorest site, as illustrated by the high total root length, whereas on the most fertile site its strategy was to efficiently exploit soil resources through increased branching intensity. The results obtained in this study provide basic knowledge on the architectural characteristics of boreal tree root systems for use by forestry professionals and modellers.
  • Kalliokoski, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail: tuomo.kalliokoski@metla.fi (email)
  • Nygren, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland ORCID ID:E-mail:
  • Sievänen, The Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland ORCID ID:E-mail:

Category: Article

article id 5481, category Article
Pekka Nygren, Pertti Hari. (1992). Effect of foliar application with acid mist on the photosynthesis of potassium-deficient Scots pine seedlings. Silva Fennica vol. 26 no. 3 article id 5481. https://doi.org/10.14214/sf.a15642

The interactive effects of potassium deficit and foliar application with acid water (pH 5.5, 4.5, 4.0 and 3.0 given consecutively) on CO2 exchange rate of Pinus sylvestris L. seedlings was investigated in field conditions. No reduction of the CO2 exchange rate was observed in the seedlings supplied with sufficient potassium. Only the seedlings having the lowest needle K concentration (2.4 mgg-1) had an apparently low CO2 exchange rate before the applications with acid water. The CO2 exchange rate of most of the seedlings with low needle K concentration (3.9–6.0 mgg-1) decreased after the acid water application. The threshold acidity for the reduction varied between pH 4,0 and 3.0 depending on the needle K concentration. The reduction was more apparent at high irradiance. It was concluded that acid precipitation disturbs the CO2 exchange only in conditions of mineral nutrient deficit.

The PDF includes an abstract in Finnish.

  • Nygren, ORCID ID:E-mail:
  • Hari, ORCID ID:E-mail:

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