ate Holistic and faunistic cliaracters. Thus each 

 ecosystem is introduced by a combinatorial model 

 merging classic Odum energese symbolism with 

 graphic (pictorial) presentations. This combination 

 should give the wide range of user groups a maxi- 

 mimi understanding of each ecosystem by stressing 

 the identification of primary ecosystem compo- 

 nents and the relationships between these compo- 

 nents. 



AREA DELINEATION 



The coastal zone in western Louisiana and 

 eastern Texas is a large integrated system which de- 

 veloped during 7,000 years of deposition of river- 

 ine sediments, mostly from the Mississippi River, 

 coupled with the continual erosion, sorting, re- 

 working, and longshore transport of these sedi- 

 ments by marine forces. The entire system can be 

 functionally divided into two broad zones, the 

 eastern deltaic plain and the western Chenier Plain. 

 The geological formation of the Chenier Plain was 

 studied during the characterization of this area so 

 it coidd be demonstrated that the entire region is a 

 system, the parts of which are functionally connec- 

 ted by dynamic long-temn physical processes. 



During the characterization of the Chenier 

 Plain ecosystem, it was appropriate to delineate the 

 area into functional subsystems. A hierarchy of 

 resolution was used; at the top is the entire Chenier 

 Plain, which consists of a group of individual drain- 

 age basins, each of which is further subdivided into 

 distinct regions (habitats) with characteristic organ- 

 ismal communities and physical components, and 

 habitats that are further subdivided into individual 

 species units (Table 3). Each higher level of resolu- 

 tion obviously includes more detail (complexity), 

 although increasing the detail in a system model 

 does not necessarily confer more understanding of 

 the entire system. 



As the level of resolution is increased to a small 

 system, the time frame becomes shorter. For ex- 

 ample, the entire Chenier Plain system evolved and 

 is changing on a time scale of thousands of years, 

 keyed to such geological processes as the periodic 

 switching of the Mississippi River and eustatic (sea 

 level) changes. Individual habitats, on the other 

 hand, have been affected by annual cycles of solar 

 energy flux, animal migrations, etc., and even were 

 radically altered by such short-term events as storm 

 surges and local "eat outs" by geese or muskrats. 



Table 3. Units within the Chenier Plain Ecosystem Hierarchy- 



Basins 



Habitats 



Populations 

 and/or species 



Vermilion Wetlands 



Mermentau Impounded areas 



Chenier Salt marsh 



Calcasieu Brackish marsh 



Sabine Intermediate marsh 



East Bay Fresh marsh 

 Swamp forest 



Aquatic 



Nearshore gulf 

 Inland open water 



Ridges 

 Beach 

 Cheniers, natural 



levees, Pleistocene 



islands 



Upland and manmade 

 spoil areas 



Agriculture 



Rice and other crops 

 Pasture 



Urban 



Shrimp 

 Menhaden 

 Finfish 

 Oyster 

 Blue crab 

 Crawfish 

 Clam 



F'urbearers and 

 other mammals 



Alligator and 

 other reptOes 



Bullfrog 



Waterfowl and 

 other birds 



Each level of the hierarchy was set in a natural 

 ecological context in the characterization in keep- 

 ing with the following rationale: 



L The whole Chenier Plain region is unified 

 by a common geological and climatic his- 

 tory that explains its origins. 



2. The drainage basin is the wetland analog of 

 the watershed, and it is tiie mc^st nearly 

 self-contained or autonomous ecosystem of 

 the Chenier Plain. It is composed of a set of 

 habitats or communities integrated by the 

 flow of water through the basin. 



3. "Habitats" or communities are not as 

 sharply defined. A habitat refers to an or- 

 ganized unit that has characteristics in addi- 

 tion to its individual and population com- 

 ponents and it functions as a unit through 

 coupled metabolic transformations. 



4. Populations of individual species are intui- 

 tively unique. The organisms have a com- 

 mon gene pool, and harvest statistics are 

 usually reported by species. Individual 

 species often occur in a number of differ- 

 ent habitats. 



This method for delineating study area is being 

 used in some of the other characterization studies 

 and provides the framework for understanding the 

 functional relationships within an ecosystem. 

 However, other methods are also being explored. 



13 



