Spectral characteristics of plant communities from salt marshes:A case study from Chongming Dongtan,Yangtzeestuary,China |
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Authors: | Liquan Zhang Zhanguo Gao Richard Armitage Martin Kent |
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Affiliation: | (1) State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200062, China;(2) Environment Monitoring Center of Ningbo, Ningbo, 315012, China;(3) Research Institute for the Built and Human Environment, School of Environment and Life Science, University of Salford, Salford, M5 4WT, UK;(4) School of Geography, University of Plymouth, Plymouth, PL4 8AA, UK |
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Abstract: | The spectral reflectance of recently formed salt marshes at the mouth of the Yangtze River, which are undergoing invasion by Spartina alterniflora, were assessed to determine the potential utility of remotely sensed data in assessing future invasion and changes in species composition. Following a review of published research on remote sensing of salt marshes, 53 locations along three transects were sampled for paired data on plant species composition and spectral reflectance using a FieldSpec™ Pro JR Field Portable Spectroradiometer. Spectral data were processed concerning reflectance, and the averaged reflectance values for each sample were reanalysed to correspond to a 12-waveband bandset of the Compact Airborne Spectral Imager. The spectral data were summarised using principal components analysis (PCA) and the relationships between the vegetation composition, and the PCA axes of spectral data were examined. The first PCA axis of the reflectance data showed a strong correlation with variability in near infrared reflectance and ‘brightness’, while the second axis was correlated with visible reflectance and ‘greenness’. Total vegetation cover, vegetation height, and mudflat cover were all significantly related to the first axis. The implications of this in terms of the ability of remote sensing to distinguish the various salt marsh species and in particular the invasive species S. alterniflora were discussed. Major differences in species with various physiognomies could be recognised but problems occurred in separating early colonising S. alterniflora from other species at that stage. Further work using multi-seasonal hyperspectral data might assist in solving these problems. |
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Keywords: | Chongming Dongtan of China salt marsh vegetation spectroradiometer compact airborne spectral imager (CASI) canopy reflectance indirect ordination |
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