USING MULTISPECTRAL VIDEOGRAPHY TO COMPARE THE PATTERN OF ZONATION BETWEEN BRACKISH WATER MARSHES AND SALT WATER MARSHES OF THE RIO GRANDE DELTA

Authors: JUDD, FRANK - UT-PANAM.UNIV,EDINBURG,TX; LONARD, ROBERT - UT-PANAM.UNIV,EDINBURG,TX; Everitt, James; Escobar, David; Davis, Michael

Submitted to: Biannual Workshop in Color Photography and Videography in Resource
Publication Type: Proceedings
Publication Acceptance Date: 7/3/1997
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. Airborne multispectral videography was used to compare the species composition and pattern of occurrence of dominant plant species between a brackish water marsh and a salt water marsh near the Gulf of Mexico in extreme southern Texas. Results showed that vegetation at both sites was organized into three zones along an elevation gradient. Maritime saltwort was the dominant species at the lowest elevation at both sites. At the brackish water marsh, shoregrass dominated intermediate elevations and Gulf cordgrass was the major species at the highest elevations. In the salt water marsh, positions of shoregrass and Gulf cordgrass were reversed. These zones could be readily distinguished in the multispectral videography. These results should be of interest to natural resource managers.

Technical Abstract: Much of the native vegetation and the topography (including drainage patterns) of the Rio Grande Delta have been destroyed or greatly altered by man for agricultural, municipal, and industrial uses. The largest remaining tract of relatively undisturbed native habitats is Laguna Atascosa National Wildlife Refuge (LANWR) which occupies 19,680 ha of the delta adjacent to the Laguna Madre. This southernmost waterfowl refuge in the Central Flyway includes about 9,720 ha of wetlands. We used multispectral videography to compare the species composition and pattern of occurrence of dominant species between a brackish water marsh and a salt water marsh at LANWR. We used the line intercept method of vegetation analysis to provide ground truth and to quantify the distribution and abundance of species. We found that the vegetation of the brackish water and salt water marshes was organized into three zones along an elevation gradient. At the lowest elevations in both marshes, maritime saltwort, Batis martima, is the dominant species. In the brackish water marsh, intermediate elevations are dominated by shoregrass, Monanthochloe littoralis, and the highest elevations support a zone of Gulf cordgrass, Spartina spartinae. In the salt water marsh, the positions of the M. littoralis zone and S. spartinae zone are reversed. Each of the zones is distinguished by a distinctive signature in the multispectral videography. This methodology should prove useful in distinguishing salt and brackish water marshes in the Rio Grande Delta.