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Title: USING MULTISPECTRAL VIDEOGRAPHY TO DISTINGUISH THE PATTERN OF ZONATION AND PLANT SPECIES COMPOSITION IN BRACKISH WATER MARSHES OF THE RIO GRANDE DELTA

Author
item JUDD, FRANK - DEPT.BIOL.PAN-AM-UT,EDINB
item LONARD, ROBERT - DEPT.BIOL.PAN-AM,EDINBURG
item Everitt, James
item Escobar, David
item Davis, Michael

Submitted to: Proceedings of the International Airborne Remote Sensing Conference
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/18/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Remote sensing techniques have long been useful tools to distinguish and map natural vegetation types. Within the past few years, video cameras have become important remote sensing tools because of the immediate imagery they provide. Multispectral videography was evaluated to determine its potential for distinguishing species composition and pattern of zonation in na brackish water marsh in Cameron County, Texas. Results showed that four vegetation zones (California bulrush, maritime saltwort, Gulf cordgrass, and shoregrass) had distinct signatures in the multispectral videography and could be readily differentiated. These findings indicate that videography may be useful for mapping plant communities and should be of interest to natural resource managers.

Technical Abstract: Cyclical flooding of the Rio Grande constitutes significant freshwater input into the marshes of the Rio Grande Delta, but dams and flood control projects have eliminated this source of freshwater. The marshes are now dependent upon rainfall alone for freshwater input and they may be experiencing significant change in species of vegetation, abundance and patterns of distribution. Unfortunately, little is known of the ecology of these marshes. We used multispectral videography to investigate distinguishing the species composition and pattern of zonation in a brackish water marsh in Cameron County, Texas. The line intercept method of vegetation analysis was used to provide ground truth. We found that the vegetation of a typical brackish water marsh is organized into three zones along an elevation gradient. At the lowest elevations there is a distinct zone dominated by maritime saltwort. At the lowest elevations in this zone where rainwater remains the longest, stands of California bulrush occur. A intermediate zone supports shoregrass as the dominant species. A third (highest) zone is dominated by Gulf cordgrass. The upper margin of this zone grades gradually into a shrub-grassland community that occurs on clay dunes. Each of the zones is distinguished by a distinctive signature in the multispectral videography. The saltwort community has a bright pink to red image response. Shoregrass has a dark brown color and Gulf cordgrass has a light gray to pinkish-tan color. Brackish water marshes may be distinguished from saltwater marshes by the relative positions of the shoregrass and cordgrass communities, but additional data are needed before this possibility is confirmed.