Plant spectral diversity from high-resolution multispectral imagery detects functional diversity patterns in coastal dune communities

Remote sensing is a fundamental tool to monitor biodiversity and spectral diversity may represent a proxy for different biodiversity facets such as taxonomic (TD) and functional diversity (FD). We used fine-resolution multispectral imagery to explore SD patterns across spatial scales (i.e., plot, transect, area), and assess SD relationships with TD and FD along an environmental gradient. We measured TD as species richness, while SD and FD were computed using probability densities functions based on pixel and species position in multivariate spaces. We compared SD and FD patterns in space occupation, and we tested whether patterns are coordinated along the environmental gradient. We assessed univariate relationships between SD and biodiversity facets, and we tested how these facets partitioned across scales. We found a strong correspondence between functional and spectral patterns in space occupation and along the environmental gradient, with a lack of significance when considering TD. By measuring FD and SD with a common methodological framework, we demonstrate that SD approximates functional patterns in plant communities. Moreover, we show that SD retrieved using high-resolution images can capture different aspects of FD, so that the occupation of the spectral space is analogous to the occupation of the functional space.