Estimation of crown cover on aerial photographs using shadow index (case study: Zagros Forests, Iran)

Document Type : Research article

Authors

1 Ph.D. student, Faculty of Natural Resources, University of Tehran

2 Professor, Faculty of Natural Resources, University of Tehran

3 Assistant Professor, Faculty of Natural Resources, University of Tehran

4 Associate Professor, Faculty of Natural Resources, University of Tehran

Abstract

     Crown cover factor is an important criterion to study changes and forest monitoring in Zagros region. Regarding to the structure of these forests that is mostly coppice with standard and can't produce industrial wood, the stand volume and basal area are not suitable factors for different studies and researches in the forests. As the forests are widespread, using aerial photographs in Zagros region is common because of its low cost and fast operation (comparing to field work). However, shadow makes it difficult to measure crown cover on aerial photographs. In this research it is aimed to offer a suitable method to determine shadow index to estimate crown cover. In Kohgiloye-BoyerahmadProvince, a 30 ha plot in Servak forests near Yasuj was chosen as the study area. The crown cover was measured on the ground using 30 circular 1000 m2 sample plots in a systematic random grid (100×100 m). The ortho-photo of the study area was obtained and classified by Minimum Distance to Mean, Maximum Likelihood, Parallelepiped and CLAPA methods into two classes of forest (crown cover with shadow) and non-forest. The crown cover of each sample plot was measured. The average of crown cover on the ground divided by crown cover with shadow on the ortho-photo is the shadow index of each classifying method. The crown cover per hectare was measured for each method by its shadow index. Comparing E%2×T in each method showed that CLAPA is the most suitable method to classify aerial photographs to determine shadow index and estimate crown cover.

Keywords

References

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Iranian Journal of Forest and Poplar Research
Volume 15, Issue 3 - Serial Number 29
October 2007
Pages 288-278

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