Lauri Korhonen, Kari T. Korhonen, Miina Rautiainen, Pauline Stenberg. (2006). Estimation of forest canopy cover: a comparison of field measurement techniques. Silva Fennica vol. 40 no. 4 article id 315. https://doi.org/10.14214/sf.315

Keywords: canopy cover; forest canopy; canopy closure; Cajanus tube; line intersect sampling; spherical densiometer; digital photographs

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Estimation of forest canopy cover has recently been included in many forest inventory programmes. In this study, after discussing how canopy cover is defined, different ground-based canopy cover estimation techniques are compared to determine which would be the most feasible for a large scale forest inventory. Canopy cover was estimated in 19 Scots pine or Norway spruce dominated plots using the Cajanus tube, line intersect sampling, modified spherical densiometer, digital photographs, and ocular estimation. The comparisons were based on the differences in values acquired with selected techniques and control values acquired with the Cajanus tube. The statistical significance of the differences between the techniques was tested with the nonparametric Kruskall-Wallis analysis of variance and multiple comparisons. The results indicate that different techniques yield considerably different canopy cover estimates. In general, labour intensive techniques (the Cajanus tube, line intersect sampling) provide unbiased and more precise estimates, whereas the estimates provided by fast techniques (digital photographs, ocular estimation) have larger variances and may also be seriously biased.

Korhonen, University of Joensuu, P.O. Box 68, FI-68101 Joensuu, Finland E-mail: lauri.korhonen@joensuu.fi
Korhonen, University of Joensuu, P.O. Box 68, FI-68101 Joensuu, Finland E-mail: ktk@nn.fi
Rautiainen, University of Joensuu, P.O. Box 68, FI-68101 Joensuu, Finland E-mail: mr@nn.fi
Stenberg, University of Joensuu, P.O. Box 68, FI-68101 Joensuu, Finland E-mail: ps@nn.fi

Category : Research note

article id 402, category Research note

Miina Rautiainen, Pauline Stenberg, Tiit Nilson. (2005). Estimating canopy cover in Scots pine stands. Silva Fennica vol. 39 no. 1 article id 402. https://doi.org/10.14214/sf.402

Keywords: Pinus sylvestris; Cajanus tube; LAI-2000 Plant Canopy Analyzer

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

The way canopy cover is defined and measured influences the obtained canopy cover percentage. Estimates of canopy cover are needed, for example, in canopy radiation modelling and remote sensing applications and as a tool for political decision-making. In this paper, we demonstrated the use of two methods, the LAI-2000 Plant Canopy Analyzer instrument and the Cajanus tube, in Scots pine stands for canopy cover estimation, and also assessed the number of measurement points required for reliable estimates. The Cajanus tube yielded slightly larger canopy closure values than the LAI-2000 instrument, but the values were nevertheless in good agreement. Both of the methods required approximately 250 measurement points for canopy closure estimates of a stand to become relatively stable. We also present the first measured effective canopy transmittance values for Scots pine stands in Finland and an example of tree pattern mapping with the Cajanus tube.

Rautiainen, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: miina.rautiainen@helsinki.fi
Stenberg, Department of Forest Ecology, P.O. Box 27, FI-00014 University of Helsinki, Finland E-mail: ps@nn.fi
Nilson, Tartu Observatory, EE-61602 Tõravere, Tartumaa, Estonia E-mail: tn@nn.ee

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