ISSN:
1573-5052
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Coatline ecosystems on Oahu, Hawaii were described in terms of vegetation composition and structure, and environmental components such as climate, physiography, exposure, substratum, and ground water. Vegetation patterns were related to these environmental components. Relevés were established in 22 study areas around Oahu to study the broader patterns of vegetation and environment, and 2 m wide belt-transects were laid out in 16 areas to study structural and floristic zonation from the ocean edge to the limit of the strand flora inland. Physiographic position, substrate type, wind exposure and climate (through climate-diagrams) were determined for each site. Soil parameters determined along the transects were salt concentration, pH, organic carbon, moisture equivalent, soil moisture at 15 atmospheres pressure, and available moisture. Three levels of pattern in vegetation distribution were inferred. First, there were similarities and differences between study areas in terms of vegetation composition and structure, and environmental components. Thirteen ecosystem-classes were recognized on the bases of dominant species and landform: Hibiscus ecosystem on beach flat, Scaevola on dunes, Scaevola on talus and alluvium, Scaevola on raised coral rock, Scaevola on rocky basalt coast, Chloris-Sida on talus, Prosopis on dunes, Prosopis on talus and alluvium, Prosopis on tuffaceous headland, Chloris-Prosopis on dune and clay flat complex, Batis on mud flats, Rhizophora on tidal flats, and Scirpus-Eichornia in fresh-water pond. A second level of pattern was that of zonation into physiognomic zones, and a third that of “floristic zonation” or change in species composition with distance from sea. Only seven ecosystems, representing five ecosystem-classes (Scaevola on dunes, Scaevola on coral rock, Prosopis on dunes, Prosopis on talus and alluvium, and Prosopis on tuffaccous headland), showed distinct physiognomic zones. But all emerged ecosystems showed floristic zonation. The distribution of the ecosystems coastwise is most broadly related to rainfall and drought patterns, to exposure to wind and surf, and to salinity of soil and water. Hibiscus ecosystems occur in wet, protected beach flats of terrigenous sand, found in windward coasts; Scaevola ecosystems in areas exposed to intense wind and salt spray; Prosopis ecosystems and their variant, Chloris-Prosopis ecosystem, in droughtly areas of the leeward coast; Chloris-Sida ecosystem on rocky soils in the same droughty climate; Batis ecosystems on mud flats of high soil- and ground-water salinity; Rhizophora ecosystems in protected shorelines subject to tides; and Scirpus-Eichornia ecosystem in still fresh water. Salt concentration decreased markedly with distance inland in fine-textured soils, but showed only slight increases or decreases in coarse-textured dune soils. Organic matter showed increases, with three transects registering increases of 15% organic C at peak portions. pH was very variable; alkaline values arising largely from a high proportion of calcium carbonate parent material or high salt content and more acid values arising from greater organic matter incorporation. The range of many of the strand species has been increasingly limited by direct disturbance and indirectly by the seaward encroachment of introduced Prosopis. But they are still persisting (in larger or smaller numbers) in Scaevola ecosystems.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00452982
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