Abstract

The restriction of tidal flow by roads, rail beds, dikes, and tide gates can significantly alter the integrity, spatial configuration, and ultimately the biodiversity of salt marshes. In our study we evaluated the effects of tide restriction on marsh habitat heterogeneity using hyperspectral remote sensing. Field-collected reflectance spectra of marsh surfaces and advanced image-classification techniques were applied to derive a thematic map of marsh surface types in the New Jersey Meadowlands from hyperspectral images captured by an airborne imaging spectroradiometer (AISA). Forty sampling sites were randomly selected in tide-restricted and tide-open areas and used to identify several landscape metrics for spatial pattern analysis. The results of this analysis showed significant differences in landscape metrics between tide-restricted and tide-open sites; open sites had a greater number, and a more even distribution, of landscape patch types. We found that the number of patches and the total edge were the best metrics for differentiating between tide-restricted and tide-open areas, and these may be used as surrogates for salt marsh biodiversity. The study indicated that hyperspectral images might be used on their own to detect marsh features that are ecologically significant.

Key words: hyperspectral remote sensing; landscape metrics; marsh; New Jersey Meadowlands; reflectance spectra; urban wetlands