HABITAT VARIATION AND HEALTH ASSESSMENT OF A DOMINANTSALTMARSH PLANT, SALICORNIA VIRGINICA, USING HYPERSPECTRAL TOOLS

摘要

Elkhorn Slough is the largest open coast, tidal wetland in central California, andit has a complex history of changing land uses, agriculture and agricultural run-off,manipulations of marsh hydrology and topography, dredging, and power plantcooling intakes. Wetlands with different histories and/or exposure to differentenvironmental stresses were compared with HyMap hyperspectral imagery (126bands; 440-2500 nm; 13-17 nm bandwidths; 2.5 - 3.0 m spatial resolution) from twoseasons (Fall 1999 and Spring 2000). We concentrated on spectral shifts inpickleweed (Salicornia virginica), the dominant saltmarsh plant, and its responses tonatural and anthropogenic disturbance, looking especially for spectral correlates ofsalinity and elevation gradients. Maps of pickleweed abundance and health (e.g.Based on density, degree of tidal submergence) were prepared by sequential use of:(1) Minimum Noise Fraction transformations; (2) Isodata unsupervisedclassifications; and (3) supervised classifications (Matched Filtering). We concludethat: pickleweed habitats can be differentiated along exposure (elevation) gradients;pickleweed canopy water content (determined by 970 nm absorption) is notcorrelated with elevation; and a reduction in red-edge (680-750 nm) spectral lengthof pickleweed classes may be correlated with stress of hypersaline habitats.