Crown typology and the identification of rain forest trees on large-scale aerial photographs

This paper assesses the potential of large-scale aerial photographs for the identification of rain forest trees. Colour slides at 1: 3000 scale were acquired in French Guiana, above the canopy of a 25 ha study site where trees had already been identified. Firstly, the stereoscopic analysis of photographic prints served to establish a typology of the crowns, based on seven main classes of criteria: crown size, crown status, crown contour, crown architecture, foliage cover, foliage texture and colour, completed where possible by information on phenology. The terminology chosen was based on those proposed in previous studies. Secondly, a smaller area of 5 ha was delimited in the field, on which 15 tree categories (vernacular names) represented by 5 crowns or more on the photographs were selected. For each category, a standard crown was described using terminology previously defined. Twelve tree categories, including first and second class commercial timbers, displayed specific characteristics allowing them to be identified on aerial photographs. Further analyses will be undertaken in the future to measure the success of this identification method. This method may be applied for the recognition of particular species of interest: commercial, rare, endemic or key-stone species. Phenological data, as well as information on crown architectural development, can also be retrieved from aerial photographs, bringing new prospects for a better knowledge of crowns biology and their functional role in the forest ecosystem.