The term "habitat", rather than 

 merely primary producers is used in 

 Figure 47 to signify that the physi- 

 cal setting created by a given habi- 

 tat is often just as important to 

 energy flow as the caloric value of 

 the vegetative tissue and detritus. 

 Each of the 350 vertebrate species 

 reported from the study area (SFRC 

 1980) is dependent not only upon the 

 food to be found there but also upon 

 other physical components of the 

 habitat such as the presence of 

 adequate nesting material, perching 

 sites, roosting sites, rotting logs, 

 solution holes, and so forth. The 

 spatial characteristics of the un- 

 derstories and canopy coverages of 

 pinelands are different from those 

 of hardwood hammocks, which are dif- 

 ferent from those of cypress domes, 

 which are different from those of 

 thickets. The variety of habitat 

 characteristics available within an 

 area is an important factor in the 

 production of a complex mixture of 

 fish and wildlife. 



A second important element of 

 this energy flow diagram is shown as 

 feedback work. When viewing the 

 entire terrestrial and freshwater 

 wetlands as an ecosystem, it is 

 essential to bear in mind that 

 the actions of any one component 

 result in physical, chemical, and 

 biological alterations which affect 

 the flow of energy and materials 

 throughout the system. 



In this regard two rather broad 

 categories of feedback can be dis- 

 cerned in natural systems: (1) 

 feedback between species and their 

 physical/chemical environment; and 

 (2) feedback between two or more 

 species. 



Examples of category one in- 

 clude: the debris produced by the 

 crashing of a red shouldered hawk 

 through tree branches in pursuit of 



a gray squirrel; the mechanical 

 mixing of detritus into the water 

 column as chub suckers gleen organic 

 matter from canal sediments; the 

 burrowing of pine borers and ter- 

 mites into fallen logs; the probing 

 actions of yellow bellied sapsuck- 

 ers, rufous-sided towhees, and 

 little blue herons; the ripping and 

 tearing of foraging birds and sloppy 

 carnivores. All of these actions 



carry a dual purpose; one the obvi- 

 ous fulfillment of the needs of the 

 organism and two, the inadvertent 

 manipulation of the physical/chemi- 

 cal environment as a byproduct of 

 the organism's actions. 



The importance of feedback work 

 between two or more species that are 

 trophically related is an offshoot 

 from the classic predator/prey model 

 of population dynamics and control. 

 Feedback between predator and prey 

 may take the form of a cropping 

 effect on the prey population, pre- 

 venting it from approaching the 

 point where available resources 

 limit its population growth. This is 

 analogous to continuous chemostat- 

 type production as opposed to batch- 

 type production. In the forward 

 direction, the successful taking of 

 prey is also feedback in the sense 

 that it stimulates growth, reproduc- 

 tion, and maintenance of the preda- 

 tor while inadequate food resources 

 result in retarded growth, reproduc- 

 tion, and maintenance. Feedback 

 between two or more trophically 

 related species may also provide 

 feedback for other species by virtue 

 of the integrated pest, predator, or 

 prey management that may result from 

 subtle interdependencies. 



Other forms of interspecies 

 feedback work that are not a func- 

 tion of direct trophic interactions 

 also influence energy flow. Beha- 

 viorial or physiological adaptations 

 that result in mutual sharing or 



129 



