Spectral detection of stress-related pigments in salt-lake succulent halophytic shrubs |
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| Institution: | 1. IPMA - Portuguese Institute for the Sea and Atmosphere, R. Alfredo Magalhães Ramalho, 6, 1495-006 Lisbon, Portugal;2. CIIMAR, Interdisciplinary Centre of Marine and Environmental Research, Terminal de Cruzeiros do Porto de Leixões, Av. General Norton de Matos s/n, 4450-208 Matosinhos, Portugal;1. Johns Hopkins Applied Physics Laboratory, 11100 Johns Hopkins Road, Laurel, Maryland 20723, United States;2. USGS Astrogeology Science Center, 2255 N. Gemini Drive, Flagstaff, Arizona, United States;3. Mount Holyoke College, Department of Astronomy, 50 College Street South Hadley, Massachusetts 01075, United States |
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| Abstract: | The spectral detection of vegetation pigment concentrations has a high potential value, but it is still underdeveloped, especially for pigments other than chlorophylls. In this study, the seasonal pigment dynamics of two Tecticornia species (samphires; halophytic shrubs) from north-western Australia were correlated with spectral indices that best document the pigment changes over time. Pigment dynamics were assessed by analysing betacyanin, chlorophyll and carotenoid concentrations at plant level and by measuring reflectance at contrasting seasonal dates. Plant reflectance was used to define a new reflectance index that was most sensitive to the seasonal shifts in Tecticornia pigment concentrations. The two Tecticornia species turned from green to red-pinkish for the period March–August 2012 when betacyanins increased almost nine times in both species. Chlorophyll levels showed the opposite pattern to that of betacyanins, whereas carotenoid levels were relatively stable. Normalised difference indices correlated well with betacyanin (r = 0.805, using bands at 600 and 620 nm) and chlorophyll (r = 0.809, using bands at 737 and 726 nm). Using knowledge of chlorophyll concentrations slightly improved the ability of the spectral index to predict betacyanin concentration (r = 0.822 at bands 606 and 620 nm, in the case of chemically determined chlorophyll, r = 0.809 when using remotely sensed chlorophyll). Our results suggest that this new spectral index can reliably detect changes in betacyanin concentrations in vegetation, with potential applications in ecological studies and environmental impact monitoring. |
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| Keywords: | Inland marshes Betacyanin Chlorophyll Halophytes Spectral indices Plant reflectance Samphire |
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