Live oak dominance is ensured because its seedlings can establish and 

 maintain themselves under the thick canopy in conditions of low light inten- 

 sities and strong root competition for soil water - conditions too stressful 

 for intolerant species (Spurr, 1964). Some oak seedlings eventually become 

 components of the canopy, while tolerant seedlings of associated subdominant 

 specios form the characteristic understory. Competition for available soil 

 water is one of the most important biotic regulating factors maintaining com- 

 munity structure. The extensive root system developed by the dominant species 

 effectively blocks seedling roots from reaching a dependable water source. 

 Low light intensities produced by the dense overhead canopy increase the stress 

 on the seedling, if it is not shade tolerant, by blocking the energy source 

 necessary for producing seedling root biomass (Clements et al., 1929; Spurr, 

 1964). 



The maritime woodland has adapted to a very stressful abiotic environment. 

 Salt stress is imposed by its proximity to the sea and the steady coastal 

 winds. Sandy dune soils contain few mineral nutrients, and such nutrients as 

 are available tend to be wery mobile and readily lost from the root zone 

 through leaching (Johnson et al., 1974). Highly porous sands permit the rapid 

 percolation of rainfall through the soil strata and movement beyond the root 

 zone. The typical available moisture content of coarse sands is approximately 

 two percent (Costing, 1956). Physiological drought may be accompanied by 

 physical drought, depending upon the availability and timing of rainfall. Rain- 

 fall provides the only source of fresh water. Much of the rainfall occurs 

 during the fall and early spring, but water requirements are greatest during 

 summer. Water conservation is a prime function of the maritime woodland and 

 is accomplished through shielding, reflection, insulation, and water storage 

 (Bellis and Proffitt, 1976). 



Most of the nutrient inputs are derived from salt spray. Sodium, magne- 

 sium, and chloride ions generally are present in surplus. Nitrogen, phosphorus, 

 calcium, and potassium tend to be scarce and are generally tied up in the bio- 

 mass. The root zone acts as an ion filter by transmitting excessive ions and 

 by conserving and recycling scarce ions released by detrital decay (Spurr, 

 1964). 



Compared to the adjacent coastal marshes, the maritime woodland is less 

 productive. Low productivity probably results from total limited primary 

 production, which in turn is the result of salt stress and low mineral base. 

 However, careful studies of southern maritime forest productivity and trophic 

 structures have not been published (Johnson et al . ; 1974 Bellis and Proffitt, 

 1976). This community appears to be a producer-decomposer system capable of 

 rapidly recycling essential nutrients back into the vegetation. Nutrients not 

 tied up in biomass or bound to soil surfaces are quickly leached out of the 

 system. Both import and export of organic matter seem to be minimal (Bellis 

 and Proffitt, 1976). 



Four groups of primary producers are distinguishable in this system. They 

 differ in the roles fulfilled in community structure and the trophic input to 

 consumer groups. 



