Discrimination of tropical forest types, dominant species, and mapping of functional guilds by hyperspectral and simulated multispectral Sentinel-2 data

摘要

To answer new scientific and ecological questions and monitor multiple forest changes, a fine scale characterizationof these ecosystems is needed, and could imply the mapping of specific species, of detailed forest types, andof functional composition. This characterization can be now provided by the novel Earth Observation tools. Thisstudy aims to contribute to understanding the innovation in forest and ecological research that can be brought inby advanced remote sensing instruments, and proposes the guild mapping approach as a tool to efficiently monitor the varied tropical forest resources. We evaluated, in tropical Ghanaian forests, the ability of airbornehyperspectral and simulated multispectral Sentinel-2 data, and derived vegetation indices and textures, to: distinguishbetween two different forest types; to discriminate among selected dominant species; and to separatetrees species grouped according to their functional guilds: Pioneer, Non Pioneer Light Demanding, and Shade Bearer. We then produced guild classification maps for each area using hyperspectral data. Our results showedthat with both hyperspectral and simulated Sentinel-2 data these discrimination tasks can be successfully accomplished.Results also stressed the importance of texture features, especially if using the lower spectral and spatial Sentinel-2 resolution data, and highlighted the important role of the new Sentinel-2 data for ecological monitoring.Classification results showed a statistically significant improvement in overall accuracy using Support Vector Machine, over Maximum Likelihood approach. We proposed the functional guilds mapping as an innovativeapproach to: (i) monitor compositional changes, especially with respect to the effects of global climate changeon forests, and particularly in the tropical biome where the occurrence of hundreds of species prevents mapping activities at species level; (ii) support large-scale forest inventories. The imminent Sentinel-2 data could serve to open the road for the development of new concepts and methods in forestry and ecological research.