humans or beavers); Diked; Partly Drained (where 

 the water level has been artificially lowered, but soil 

 moisture is sufficient to support hydrophytes). 



4.1.3 Hydrological Regimen 



Water table activity varies considerably 

 among cedar forests, and from year to year Golet 

 and Lowry's (1987; Lowry 1984) 7-year study of the 

 hydrological regimen of six Rhode Island cedar 

 swamps is the first long-term research to be publish- 

 ed on this subject (Figure 21). They found the mean 

 annual water level varied between 1 3 cm above to 1 1 

 cm below the ground surface (ave. 0.7 cm above). 

 The forest surface was flooded from 1 8% to 76% of 

 the growing season. Mean annual water table fluc- 

 tuation ranged from 1 7 cm to 75 cm, with great varia- 

 tion between swamps. Precipitation variations 

 accounted for 85%-92% of water level variation 

 during the growing season. However, the effect of 

 ground water inflow statistically outweighed that of 

 precipitation in two sites. Cedar-dominated swamps 

 have generally higher water levels than nearby red 

 maple swamps (Reynolds et al. 1982; Lowry 1984) 

 and are flooded for longer periods (Lowry 1984). 



During the wettest year of Golet and Lowry's 

 study, when total precipitation was 157.4 cm, water 

 levels in four of six sites studied were above the sur- 

 face all year (Figure 21). In the driest years (97.0 and 

 1 02.8 cm precipitation/year) water levels were as low 



as 100 cm below the surface at some sites. Depth of 

 the water tables was related not only to precipitation, 

 but also presumably to ground water flow, and per- 

 cent and type of cover (and thus, to total transpira- 

 tion), as well as to soil properties, microtopography, 

 and other watershed characteristics. Cedar growth 

 rates are influenced by the water regime at individual 

 sites, but no general relationship between them is 

 discernible (Golet and Lowry 1987). 



4.2 WATER CHEMISTRY 



The water of Atlantic white cedar wetlands 

 that are ombrotrophic (dependent on precipitation 

 for water and minerals, as in many glacial kettles) is 

 generally deficient in ions, has low specific conduc- 

 tance, and is low in pH (Laderman 1980; Golet and 

 Lowry 1987) (Table 3); cedar stands that grow in 

 stream-side or stream-fed swamps (as in the 

 Pinelands [Schneider and Ehrenfeld 1987]; Florida 

 [Clewell and Ward 1987]; and Mississippi [Eleuterius 

 and Jones 1 972]) or are subject to significant lateral 

 flow (as in the Great Dismal [Bandle and Day 1985; 

 USFWS 1986b]), are more minerotrophic (i.e., their 

 water is enriched by mineral soils through which it 

 passes) and often have a more neutral pH (Table 4). 

 The chemical composition and pH of minerotrophic 

 wetland water is closely tied to the chemistry of the 

 rock strata and the nature of the vegetation in the 

 region through which the source water flows (Gor- 

 ham1987). 



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Figure 21. Water levels in six Rhode Island Cedar swamps over a seven year period. Monthly precipitation 

 is plotted for the period of sampling; annual precipitation values are shown in parentheses (from Golet and 

 Lowry 1987). 



31 



