level is near the surface and receives the percolated water. The hydrologic 

 gradient moves groundwater into the adjacent ecosystems (brackish or fresh 

 marsh) where it contributes to standing water. 



Evaporation occurs along several pathways: from the surface of standing 

 water, from micropore water, and from plant transpiration. Climatic conditions 

 regulate the evaporation rate from the storages. In addition, the rate of micro- 

 pore water evaporation is regulated by soil heat, soil structure, concentration 

 of organic materials, and vegetative cover. Soil moisture is the major contribu- 

 tion of the hydrologic cycle to vegetative growth. Many authors (Clements et 

 al., 1929; Lehmann, 1941; Costing, 1956; Marks and Harcombe, 1975; and others) 

 allude to this point when discussing the influences of tropography, elevation, 

 drainage, slope, and soil texture upon plant distribution. 



The nutrient cycle is a major, tremendously complex element of the abiotic 

 system. Return or recycle mechanisms in many cases require flows through biotic 

 components (H.T. Odum, 1971). The storage of available nutrients in this upland 

 ecosystem is of secondary importance as compared to the regulatory significance 

 of soil moisture and fire (Bourdeau, 1954; Spurr, 1964). Soil moisture is the 

 transport medium for soil nutrients (Bucknan and Brady, 1969), 



A brief summary of the complex nutrient cycle is necessary, however, to 

 indicate at least the fundamental flows as well as to mention the primary regu- 

 lating factors. To summarize this complicated cycle requires simplification 

 and generalization. 



There are three main sources of materials stored in the nutrient cycle. 

 These are inorganic nutrients found in the substrate (Spurr, 1964); plant mate- 

 rials from the ecosystem (Costing, 1956); and marine salts, either relict or 

 from wind-borne salt spray (Au, 1974). Inorganic nutrients derived from either 

 the parent material or the marine salts are made available to plants via strictly 

 physical/chemical processes. Examples are phosphorus, potassium, and magnesium. 

 Soil moisture and soil pH regulate these processes (Buckman and Brady, 1969). 

 Inorganic nutrients derived from organic sources involve more complex pathways, 

 requiring nutrient flows through the soil biota to permit inorganic nutrient 

 release. Two important elements that require biotic "recycling" are nitrogen 

 and sulphur. Regulatory factors control not only the physiochemical aspects 

 of the soil chemistry, but also determine the soil's suitability as an environ- 

 ment for the soil biota, which accomplish the biochemical conversions. Soil 

 moisture, soil heat, soil aeration, pH, and the availability of inorganic 

 nutrients are important regulating factors (Buckman and Brady, 1969). 



Fire can regulate the abiotic system directly through its effects on soil 

 properties or, more significantly, it can regulate site quality indirectly 

 through its impact on vegetation (Ahlgren and Ahlgren, 1960; Spurr, 1964; 

 Daubenmire, 1968). Fire increases the available nutrient pool and accelerates 

 the conversion of complex organic materials to simpler compounds, thus aiding 

 the soil biota. Increased inorganic (primarily calcium and magnesium) nutrients 

 raise the soil pH and improve soil fertility for about three yr (Daubenmire, 



22 



