Current issue: 56(2)

Under compilation: 56(3)

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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'stem curve'

Category: Article

article id 7332, category Article
M. Lappi-Seppälä. (1936). Tutkimuksia männyn ja koivun runkomuodosta. Silva Fennica vol. 44 no. 4 article id 7332.
English title: Studies on stem forms of Scots pine and Betula sp.
Original keywords: runkomuoto; runkokäyrä; Scots pine; tyvilaajenema
English keywords: taper curve; stem curve; butt swelling
Abstract | View details | Full text in PDF | Author Info

The stem form influences the value and volume of the stem. Sample trees in homogenous mixed stand of Scots pine (Pinus sylvestris L.) and Betula sp. were measured to define the stem form of the trees, and to develop research methods. The height of butt swelling and the turning point of taper curve varies greatly. In Scots pine and Betula sp. it was typically between the 2/10 and 3/10 height of the tree. Consequently, the theoretical normal curves describing stem form, where the turning point of taper curve is situated under the breast height diameter, are not entirely generally applicable. There was a correlation between the base curve and the form of actual taper curve of the stem. The form of the top of the stem depends on the structure and dimensions of the crown. The most reliable measuring point to define taper curve would be a diameter that is above butt swelling, near the turning point of the taper curve. Length of the crown can be used to deduce the form of the top of the stem. According to the study, the volume tables could be based on diameter on breast height, slenderness of the stem (D0,25h:h) and length of the crown. Age of the tree and position in the stand influence stem form, but the forest site type seemed not to have clear effect on the stem form.

The PDF includes a summary in German.

  • Lappi-Seppälä, E-mail: ml@mm.unknown (email)
article id 7685, category Article
Risto Ojansuu. (1993). Prediction of Scots pine increment using a multivariate variance component model. Silva Fennica vol. 0 no. 239 article id 7685.
Keywords: Pinus sylvestris; crown height; volume increment; bark volume; variance component models; multivariate models; stem curve models; tree form change
Abstract | View details | Full text in PDF | Author Info

Diameter and volume increment as well as change in stem form of Scots pine (Pinus sylvestris L.) were analysed to predict tree increment variables. A stem curve set model is presented, based on prediction of the diameters at fixed angles in a polar coordinate system. This model consists of three elementary stem curves: 1) with bark, 2) without bark, and 3) without bark five years earlier. The differences between the elementary stem curves are the bark curve and the increment curve. The error variances at fixed angles and covariances between the fixed angles are divided into between-stand and within-stand components. Using principal components, the between-stand and within-stand covariance matrices are condensed separately for stem curve with bark, bark curve and increment curve. The two first principal components of the bark curve describe the vertical change in Scots pine bark type and the first principal component of the increment curve describes the increment rate. The elementary stem curves, bark curve and increment curve as well as corresponding stem volumes, bark volume and volume increment can be predicted for all trees in the stand with free choice of sample tree measurements. When only a few sample trees are measured, the stem curve set model gives significantly more accurate predictions of bark volume and volume increment for tally trees than does the volume method, which is based on the differences between two independent predictions of volume. The volume increment of tally trees can be predicted as reliably with as without measurement of sample tree height increment.

The PDF includes a summary in English.

  • Ojansuu, E-mail: ro@mm.unknown (email)

Category: Research article

article id 511, category Research article
Luis Diego Pérez Cordero, Markku Kanninen. (2003). Heartwood, sapwood and bark content, and wood dry density of young and mature teak (Tectona grandis) trees grown in Costa Rica. Silva Fennica vol. 37 no. 1 article id 511.
Keywords: stand density; cross-sectional area; relative stem curves; stem analysis
Abstract | View details | Full text in PDF | Author Info
The aim of this study was to evaluate the heartwood, sapwood and bark content, and wood dry density in young and mature teak (Tectona grandis) trees. For this, 17 plantations were selected from 11 sites representing different climatic conditions and plantation densities (156 to 1600 trees ha–1, and line planting). From these plantations, a total of 87 trees with ages between 5 and 47 years were felled for stem analysis. The highest heartwood proportion of stem volume (over bark) was 61% and the lowest 0.4%. The sapwood proportion ranged between 24 and 72%, while bark represented from 14 to 37% of the total volume. Heartwood proportion was significantly different (P < 0.05) among climatic zones: ‘wet’ sites producing less heartwood than ‘dry’ sites. Stem diameter (under bark) and heartwood diameter at different stem heights differed among sample trees, even when plotted in relative values to avoid dependency with stem size. Dry density was statistically different between 8-year-old trees or younger and 47-year-old trees, and between line planting trees and 13-year-old trees or younger, but did not differ statistically between line planting trees and mature trees. No significant differences were found between climatic zones or between different stand densities. Dry density values for T. grandis plantations in Costa Rica are similar to those reported elsewhere.
  • Pérez Cordero, Centro Agronómico Tropical de Investigación y Enseñanza (CATIE), Turrialba, Costa Rica E-mail: (email)
  • Kanninen, Center for International Forestry Research (CIFOR), Bogor, Indonesia E-mail:

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