PARENT SESSION
Oral Session #71: Remote Sensing and GIS.
Presiding: J.D. Allan
Wednesday, August 7. 1:00 PM to 4:45 PM. Palo Verde Room, Radisson.

Extracting complex data from estuarine imagery: Spartina alterniflora in Willapa Bay, WA.

CIVILLE, JANIE^*,1, SMITH, STUART², ¹ Evolution and Ecology, Davis, CA² True North GIS, Olympia, WA

ABSTRACT- Spartina alterniflora Loisel. (common cordgrass) is the primary component of Atlantic and Gulf coast estuaries. Its introduction to Pacific Northwest estuaries, however, has proven to be problematic. The rapid expansion of the clonal grass across the open habitat of intertidal mudflats is a stunning example of unimpeded colonization, and has presented challenges not only to management efforts but to attempts to record and analyze the invasion. A time series analysis of aerial photography, black and white and color infra-red, has been conducted through image analysis and classification, followed by GIS manipulation of data sets to discern population growth patterns. The original goal of the researchers was to populate growth models with actual data extracted from ArcInfo coverages, but an apparently simple task became rapidly impossible, due to database size and complexity. The problem was ultimately solved by applying a relatively novel approach to the data structure, the use of polygon regions to keep associations of Spartina clones together as they expanded and eventually merged into large meadow complexes. This approach has allowed us to track data from up to 40,000 individual clones through the course of their expansion on Willapa Bay. The lateral growth and merger data are providing important insight into abiotic factors that control the Spartina growth, and are the basis for theoretical model development and exploration.

KEY WORDS: Spartina alterniflora, remote sensing, GIS, estuary