Estimation of canopy gap size and gap shape using a hemispherical photograph |
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Authors: | Lile Hu Zhiwen Gong Junsheng Li Jiaojun Zhu |
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Institution: | (1) Institute of Applied Ecology, Chinese Academy of Sciences, Wenhua Road 72, 110016 Shenyang, China;(2) Chinese Research Academy of Environmental Sciences, Beiyuan Road, Chaoyang District, 100012 Beijing, China;(3) College of Forestry, Beijing Forestry University, No. 35, Qinghua East Road, 100083 Beijing, China |
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Abstract: | Gap size and gap shape are two important properties of forest gaps that can influence microsite conditions in a forest stand
and determine the recruitment and establishment of trees. There is no universally adopted method for measuring the gap size,
although several options are available. In addition, few methods have been proposed for measuring the gap shape. This paper
proposes a photographic method of estimating canopy gap size and gap shape. The proposed method is based on a vertical hemispherical
photograph of the gap and is thus named the hemispherical photograph method (HPM). We tested the accuracy of the HPM measure
of gap size by two ground-based methods and compared the HPM with other methods. Our results indicate that the HPM measurement
of the canopy gap size is accurate, but is significantly influenced by the location of the camera. Compared with the ground-based
methods, the HPM is more objective and repeatable. Compared with other photographic methods, HPM is more accurate due to the
more actual assumptions, but is more labor-intensive because more field measurements are necessary. We conclude that the HPM
is a powerful tool for comparative and long-term studies of forest gaps. |
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