Estimation of Optical Porosity or Canopy Structure of Two Species of Tree with Hemispherical and Vertical Images

• Autor(a) principal: Velarde, Jacinto Garrido
• Data de Publicação: 2018
• Outros Autores: Blanco, Julio Hernández, Aliseda, Julián Mora
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.5/28865
• topic: Optical Porosity; Vertical forests structure; Allometric relationships; Hemispherical Photography; Vertical Photography; Quercus pyrenaica; Castanea sativa

Meaningful, reliable and fast estimates of woodland canopy are essential to the characterization of forest ecosystems. In this document, the accuracy of the technology of hemispherical digital photography and its comparison with a measuring proposal via vertically-arranged photography is evaluated for the estimation of canopy porosity in two deciduous tree species: oak and Sweet chestnut. Complementarily, estimative models are proposed of porosity capacity of the species under study, in function of allometric variables of statistical weight in tree growth: canopy diameter and DBH (diameter breast height). For the execution of this study an experimental area of rural character was chosen in the Ambroz Valley, in Cáceres Province (Spain), where Quercus pyrenaica and Castanea sativa were selected as the most representative species. The data was gathered in the season with greatest foliage development for both species: the summer. The average tree canopy porosity obtained via the two methods under evaluation is very similar when compared through regression analysis (R²=0,919 for Sweet chestnut; R²=0,952 for oak). Therefore both methods would be eligible for measuring OP of the species proposed for this study. The equivalence of measurements in vertical perspective as opposed to hemispherical makes viable the use of porosity percentages as indicators of what the average observer is able to visualize through the canopy. Starting from these preliminary conclusions, it would be feasible to develop a quantification tool for degrees of filtering with application to landscape planning and reduction of visual impact. Complementary research on other species could be recommendable in order to standardize and validate this proposal.