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FIGURĘ 16.1 Continental realm: biophysicochemical factors. Diagram depicts the and temporal variability of Continental environments and the organisms that inhabit it (see aJso Figs. 16.2 and 16.3).

eolian, glacial, and volcanoclastic deposition. The subenvironments within Continental depositional Systems have varying amounts of water for varying amounts of time, manifested physically and chemi-cally in different ways. Although sediments accumu-late or are removed by water-lain (liquid and solid), wind-blown, or air-fall (volcanoclastic) processes, they inevitably spend variable amounts of time beneath the water table. The water table is the boundary between the vadose (unsaturated) and phreatic (saturated) zones of the groundwater profile (Fig. 16.2). The vadose zonę is where the porę space in sediment eon ta i ns air and water. This zonę can be subdivided into the soil water, and the upper and intermediate vadose zonę. The phreatic zonę is where porę space is saturated, and also includes the capillary fringe (Driscoll, 1986). A stand ing body of water occurs where the phreatic zonę intersects the ground surface. This water will flow if there is a gradient on the landscape. A perched water table occurs in areas that are imperfectly or poorly drained, as well as in areas associated with flowing water, like stream or river (Driscoll, 1986).

Terrestrial subenvironments are well, Imperfectly, or poorly drained depending on sediment texture

and the amount of water r• . and output (Fig. 16.1). Water input and oułpM are controlled ultimately by climate. Soil, bio t . d climate are linked through the soil-water b-^:    be in terrestrial

environments (Thornthwaite a.    Mather, 1955).

There are several components c the soil-water balance (see also Hasiotis,    this volume).

Evapotranspiration (E) is defined as actual evapo-transpiration (Ea)—the actual ratę at which water vapor is returned to the atmosphere from the ground and by plants and potential evapotranspira-tion (Ep)—the water vapor flux under ideał condi-tions of complete ground cover by plants, uniform plant height and leaf coverage, and an adequate water supply. Effective precipitation (EP) is the temporal distribution of precipitation, moisture losses from evapotranspiration, and temperaturę (Lydolph, 1985). EP is a proxy for the relationship between precipitation and temperaturę for a particular region and takes into account also the seasonality of precipitation. Water availability in terrestrial environments affects the depositiona setting, soil formation, nutrient cyc ling, and overa biodlversity (lenny, 1941; Thornthwaite and Mather, 1955; Whiltnkor, 1975; Strahler and Strahler, 198 • J