Landscape position and habitat polygons in a dynamic coastal environment

Authors


  • Corresponding Editor: D. P. C. Peters.

Abstract

In contrast to stable inland systems, coastal landscape positions are dynamic, changing as shorelines migrate and storms alter topography. We define landscape position by distance to ocean shoreline and elevation above sea level, two metrics that integrate a suite of environmental and biotic factors. As shoreline and elevation change, suitability of a geo-referenced position for a given plant species may also change. The objectives of our study were to use two methods for measuring landscape position (GPS and hyperspectral/light detection and ranging or LIDAR) to develop habitat polygons, compare habitat polygons for five species representing several adaptive strategies, and illustrate change in landscape position due to migrating shoreline for a Virginia, USA barrier island. Habitat polygons for each species were distinct, represented several growth forms or functional groups, and were indicative of tolerances to biotic and abiotic stresses. The habitat polygon for Cakile edentula (annual forb) was relatively small, indicating narrow habitat requirements for the strand environment. Cirsium horridulum (biennial forb), with succulent shoots and roots, occurred on dunes where water is most limiting. For the dune-building grass, Ammophila breviligulata, as distance from shoreline increased, minimum elevation also increased. Two woody species occurred across the entire island; however, Morella cerifera (N-fixing shrub), was limited to mesic swales whereas Juniperus virginiana (evergreen tree), with the largest habitat polygon, occurred on both dunes and swales. For a geo-referenced point on the north end of Hog Island, distance to shoreline increased from the shoreline to 1100 m inland over 139 years. In contrast, the geo-referenced point on the eroding portion of the island decreased from 1700 m to 120 m from the ocean shoreline over the same time period. Where sea level rise and storms are expected to alter shorelines and island topography, generation of habitat polygons from hyperspectral and LIDAR imagery provide rapid assessment of potential effects on species distribution patterns at local and regional scales. Habitat polygons have broad applicability beyond coastal systems and may contribute to a rapid assessment or identification of vulnerability for species as climate patterns shift through time.

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