author = "Ferreira, Matheus Pinheiro and F{\'e}ret, Jean-Baptiste and Grau, 
                         Eloi and Gastellu-Etchegorry, Jean-Philippe and Shimabukuro, Yosio 
                         Edemir and Souza Filho, Carlos Roberto de",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universit{\'e} Montpellier} and {Universit{\'e} Montpellier} 
                         and {Centre d'Etudes Spatiales de la BIOsph{\`e}re (CESBIO)} and 
                         {Instituto Nacional de Pesquisas Espaciais (INPE)} and 
                         {Universidade Estadual de Campinas (UNICAMP)}",
                title = "Retrieving structural and chemical properties of individual tree 
                         crowns in a highly diverse tropical forest with 3D radiative 
                         transfer modeling and imaging spectroscopy",
              journal = "Remote Sensing of Environment",
                 year = "2018",
               volume = "211",
                pages = "276--291",
                month = "June",
             keywords = "Hyperspectral remote sensing, DART, Functional traits, Model 
                         inversion, Tree species classification, Tropical forest.",
             abstract = "Spatial and temporal information on the structural and chemical 
                         properties of tropical forest canopies are key to understanding 
                         ecosystem processes. However, such information is usually limited 
                         to field studies performed at the plot level (~1\ ha). The 
                         combination of imaging spectroscopy with physically based 
                         radiative transfer (RT) models holds great promise for 
                         generalizing and extrapolating insights from plot-based studies to 
                         whole landscapes. Here, we tested the capacity of a simplified 3D 
                         RT approach to retrieve the structural and chemical traits of 
                         individual tree crowns (ITCs) from a highly diverse tropical 
                         forest. We first produced two datasets called measured and 
                         simulated. The measured dataset was composed of ITC reflectance 
                         extracted from sunlit imaging spectroscopy pixels. The simulated 
                         dataset was produced using a look-up-table approach and the 
                         discrete anisotropic radiative transfer (DART) model. We then 
                         compared the simulated and measured reflectances of ITCs in terms 
                         of shape difference by computing the spectral angle. The results 
                         showed small disagreements between the simulated and measured 
                         reflectances. Such differences impacted neither the spectral 
                         variability nor the spectral regions recognized as useful for 
                         species discrimination, showing that the spectral angle was a 
                         suitable measure of spectral similarity. Simulation robustness was 
                         assessed by comparing model parameters obtained by inversion to 
                         imaging spectroscopy vegetation indices and the proportion of 
                         non-photosynthetic vegetation (NPV), green photosynthetic 
                         vegetation (GV) and shade estimated within ITCs. DART canopy 
                         structural parameters were related to NPV 
                         (R2\ =\ 0.71), GV (R2\ =\ 0.78) and 
                         shade (R2\ =\ 0.55). DART canopy foliar parameters 
                         such as chlorophyll and carotenoids were related to the ratio of 
                         TCARI/OSAVI (R2\ =\ 0.80) indices and the simple 
                         ratio between reflectances at 515\ nm and 570\ nm 
                         (R515/R570) (R2\ =\ 0.54), respectively. 
                         Species-related differences in NPV, GV and shade were explained by 
                         variations in crown architectural characteristics. The simulation 
                         framework employed in this study can be applied to retrieve 
                         structural and chemical traits of ITCs from other areas in which 
                         high-resolution imaging spectroscopy data are available.",
                  doi = "10.1016/j.rse.2018.04.023",
                  url = "http://dx.doi.org/10.1016/j.rse.2018.04.023",
                 issn = "0034-4257",
             language = "en",
           targetfile = "ferreira_retrieving.pdf",
        urlaccessdate = "25 jul. 2021"