%0 Research article
%T Estimation of forest canopy cover: a comparison of field measurement techniques
%A Korhonen, Lauri
%A Korhonen, Kari T.
%A Rautiainen, Miina
%A Stenberg, Pauline
%D 2006
%J Silva Fennica
%V 40
%N 4
%R doi:10.14214/sf.315
%U https://silvafennica.fi/article/315
%X 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.