influence soil development, erosion, 

 and solution of the substrate, and 

 consequently affect the physical and 

 chemical nature of other habitats 

 within the basin. The net structure 

 and function of these terrestrial 

 and freshwater habitats influence 

 the delivery rates and loadings of 

 water and chemical energy to the 

 downstream estuary. Here too, 



geology and long-term patterns of 

 hydrologic input serve as evolution- 

 ary guidelines around which species 

 can organize into habitats. 



1.4 CONCEPTUAL MODEL OF 

 REGIONAL ECOLOGICAL 

 PROCESSES 



In this section, we apply the 

 above concepts to the development of 

 a "model" of the lower Everglades, 

 Florida Bay, and Florida Keys water- 

 shed. Through this model we present 

 a simplified flow diagram of how the 

 various components of the watershed 

 (its meteorological setting, its 

 hydrologic cycle, its soils, and its 

 biological resources) interact to 

 create and maintain a living unit. 



In some respects, the concep- 

 tual model is similar to a painting 

 of a coastal marsh: if one concen- 

 trates on a blade of grass, the de- 

 tail is lost, and the blade, or what 

 appears to be the blade, becomes no 

 more than a stroke of paint. The 

 artist's intention is not to accu- 

 rately portray every blade of grass 

 but to catch the essence of the 

 marsh as a whole. This approach 

 underlies the perspective sought in 

 a conceptual model; that is, to 

 sacrifice the minutiae, in order to 

 identify the overriding controls, 

 forces, sinks, and pathways of the 

 system. It is hoped that through 

 this perspective the viewer may see 

 the forest in spite of the trees. 



Symbols used throughout this 



section in constructing the concep- 

 tual model of energy and materials 

 flow are presented in Table 1. A 

 brief explanation of the meaning and 

 general use of each of these symbols 

 is also given. 



Figure 2 presents a conceptual 

 model of energy and materials flow 

 through a selected ecological system 

 (i.e., a number of closely related 

 habitats). The Florida Keys eco- 

 system is chosen for illustration. 

 Within Figure 2, an attempt is made 

 to ground-truth each of the symbols 

 and the lines interconnecting them 

 with an explanation. Not all the 

 possible connections and lines are 

 presented since this unduly compli- 

 cates the visualization process and 

 eventually compromises the simplify- 

 ing purpose of the model. Only the 

 major forcing functions and internal 

 metabolic processes are explicitly 

 diagrammed. To the right of the 

 model, a dashed line leads off to an 

 abbreviated list of the overlapping 

 habitats which this ecosystem encom- 

 passes. 



In addition to the forcing 

 functions listed as "Incoming Ener- 

 gies", the Florida Keys ecosystem is 

 intricately linked to a series of 

 additional "ecosystems", such as 

 Florida Bay, the estuarine and salt- 

 water wetlands of the mainland, the 

 shallow coastal and continental 

 shelf of the Gulf of Mexico, and the 

 blue-water Straits of Florida. 

 These interconnections are symbol- 

 ized in the general model as double 

 directional arrows between the Keys 

 and the respective ecosystems, sig- 

 nifying that energy and matter flow 

 in both directions. 



In keeping with the initial 

 purpose of this document, it is 

 essential that we also incorporate 

 man's role in watershed metabolism. 

 As agriculture, industry, and 



