Erkki Laitakari. (1929). The capability of trees to protect themselves against storms. Acta Forestalia Fennica vol. 34 no. 34 article id 7247. https://doi.org/10.14214/aff.7247

Keywords: literature review; windfall; windbreak; adjustment

Abstract | View details | Full text in PDF | Author Info

The article discusses the adaptation mechanisms of the trees against storms or stormy winds. Two main aspects are revealed: the adjustments of stem and crone and the adjustments of the root system.

The shorter the stem the lower the danger of windfall or windbreak. The wind load of a tree depends on where it is situated; on the open field the wind is much stronger than in closed stand. The tree adjusts its height on the situation: where the wind load is high the trees remain smaller. A tree adjusts its crone also depending on the wind. The branches of spruce are relatively thin and very flexible. An alone standing trees have a flat or umbrella-like crone. Trees with a deep-going main root (tap root) are best protected against windfalls. When there is no tap root, the horizontal roots need to strengthen to offer the needed support.

The protection from windfalls is an important question in the practical forestry. Knowing the factors affecting the wind tolerance of a tree the forest management can be planned to support them.

The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.

Laitakari, E-mail: el@mm.unknown

Category : Research article

article id 283, category Research article

Ilkka Korpela, Tuukka Tuomola, Esko Välimäki. (2007). Mapping forest plots: an efficient method combining photogrammetry and field triangulation. Silva Fennica vol. 41 no. 3 article id 283. https://doi.org/10.14214/sf.283

Keywords: remote sensing; least squares adjustment; intertree positioning; spatial resection; trilateration

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Intra stand spatial information is often collected in ecological investigations, when functioning or interactions in the ecosystem are studied. Local relative accuracy is often given priority in such cases. Forest maps with accurate absolute positions in a global coordinate system are needed in remote-sensing applications for validation and calibration purposes. Establishing the absolute position is particularly difficult under a canopy as is creating undistorted coordinate systems for large plots in the forest. We present a method that can be used for the absolute mapping of point features under a canopy that is efficient for large forest plots. In this method, an undistorted network of control points is established in the forest using photogrammetric observations of treetops. These points are used for the positioning of other points, using redundant observations of interpoint distances and azimuths and a least squares adjustment. The method provides decimetre-level accuracy and only one person is required to conduct the work. An estimate of the positioning accuracy of each point is readily available in the field. We present the method, a simulation study that explores the potential of the method and results from an experiment in a mixed boreal stand in southern Finland.

Korpela, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ilkka.korpela@helsinki.fi
Tuomola, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: tt@nn.fi
Välimäki, University of Helsinki, Department of Forest Resource Management, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ev@nn.fi

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