USING HYPERSPECTRAL IMAGING DATA FOR CHARACTERIZING MACROPHYTE DIVERSITY: SPECTRO-FUNCTIONAL VARIABILITY WITHIN AND ACROSS FLOATING AND EMERGENT PLANT SPECIES

For their morpho-physiological peculiarities and wide phenotypic plasticity, macrophytes occupy the extremes of the global spectrum of vegetation forms and such heterogeneity results into them displaying contrasting patterns of diversity along ecological and geographical gradients. Imaging spectroscopy is a high-throughput technique that make a feasible, efficient option for assessing plant functional diversity across spatial scales, based on spectral proxies directly related to morphological and biochemical traits, which we define as <em>spectro-functional</em> traits. In this study, we used airborne hyperspectral data for assessing inter- and intra-specific spectral diversity of floating and emergent macrophyte species in two shallow freshwater systems, located in Italy and Hungary. Our results show that spectro-functional traits in selected species develop along two main axes of variability, expressing the trade-offs in leaf economics (resource use) and photosynthetic performance (leaf size, biochemistry), as predicted from generalist models, and that intraspecific variability accounts for a large amount of the overall functional diversity observed, ranging from 35-39% in spectral proxies of pigments to 49-62% in spectral proxies of structural and physiological parameters. Spatial-wise, remotely sensed maps of macrophyte traits can capture fine-scale variability, among and within species, that could be hardly detected from punctual measurements: a powerful addition to the technical toolbox in the hands of functional ecologists focusing on aquatic plant diversity and connected ecological processes.