Species richness refers to the total number of species in the sample plot. Shannon-Wiener index (Shannon, 1948) and Simpson index (Simpson, 1949) can reflect species richness and evenness of species distribution. They are comprehensive indicators reflecting the degree of species diversity. The Shannon-Wiener index is more sensitive to the number of species, and the to the evenness of enriched species (Nagendra, 2002). The calculation formula of the Shannon-Wiener index (H) and Simpson index where n is the total number of species in the sample plot, and pi is the proportional abundance of the species.
Individual tree crown segmentation Based on the 0.1 m CHM data, we used a watershed algorithm combined with morphological crown control to separate the individual tree crowns (ITCs) (Wang et al., 2004; Chen et al., 2006; Zhao et al., 2014). Firstly, a morphological crown closing operator was used to Spain phone number list determine the crown area and obtain the binary image of the canopy. Next, a local extremum algorithm was used to detect the positions of the potential individual treetop. The actual individual treetop positions and potential crown shapes were calibrated through two watershed transformations and image reconstruction operations.
Finally, the crown shapes were determined using an adaptive optimized morphological crown opening operator. Spectral angle mapper (SAM) classification Among many supervised classification methods, the SAM classification was used for its better performance in the hyperspectral data (Park et al., 2004; Yang et al., 2008; Zhang and Li, 2014). The SAM algorithm is a physically based spectral classification that uses an n-dimensional angle to match the extracted endmember spectra (Kruse et al., 1993; Park et al., 2007; Mohajane et al., 2017). The SAM algorithm determines the spectral similarity though calculating the angle between the spectrum vectors. Smaller angles correspond to closer matches to the endmember spectrum.