MAPPING EELGRASS SPECIES Zostera japonica AND Z. marina, ASSOCIATEDMACROALGAE AND EMERGENT AQUATIC VEGETATION HABITATS IN PACIFICNORTHWEST ESTUARIES USING NEAR-INFRARED COLOR AERIAL PHOTOGRAPHYAND A HYBRID IMAGE CLASSIFICATION TECHNIQUE

摘要

Aerial photographic surveys of Oregon's Yaquina Bay estuary were conducted duringconsecutive summers from 1997 through 2000. Imagery was obtained during low tide exposuresof intertidal mudflats, allowing use of near-infrared color film to detect and discriminate plantcommunities. Approximately 90 percent of submerged aquatic vegetation occurs in the intertidalzone at this latitude. The photographs were digitized and orthorectified for image analysis. Ahybrid image classification algorithm was developed to allow discrimination of intertidal habitatsdominated by the eelgrasses Zostera japonica and Z. marina, the green macroalgae Ulva spp.andEnteromorpha spp., the brown alga Fucus sp., unvegetated areas and various emergent upperintertidalreeds, grasses and sedges. Application of this algorithm has promise of allowinghabitat delineation and change analysis mapping at the sub-meter level over time in Pacific NWestuaries characterized by significant tidally-exposed habitats. Such changes are of interest inthe assessment of the influence of environmental stresses such as land use management practices(as a typical anthropogenic source), episodic weather events, and long-term (decadal) weathercycles on the resiliency of these plant communities.