Nonwetland - Any area that has sufficiently dry conditions that hydrophytic vegetation, hydric soils, and/ 

 or wetland hydrology are lacking; it includes upland as well as former wetlands that are effectively 

 drained. 



Normal circumstances - Refers to the soil and hydrology conditions that are normally present, without re- 

 gard to whether the vegetation has been removed. 



Obligate wetland species - A plant species that is nearly always found in wedands; its frequency of occur- 

 rence in wetlands is 99% or more. 



Offsite determination method - A technique for making a wetiand determination in the office. 



Onsite determination method - A technique for making a wetiand determination in the field. 



Organic soil - See Histosols. 



Overbank flooding - Any situation in which inundation occurs as a result of the water level ©f a river or 

 stream rising above bank level. 



Oxidation-reduction process - A complex of biochemical reactions in soil that influences the valence state 

 of elements and their ions found in the soil; long periods of soil saturation during the growing season tend 

 to elicit anaerobic conditions that shift the overall process to a reducing condition. 



Oxidized rhizospheres - Oxidized channels and soil surrounding living roots and rhizomes of hydrophytic 

 plants. 



Parent material - The unconsolidated and more or less weathered mineral or organic matter from which the 

 soil profile is developed. 



Pedogenic - Related to soil-building processes occurring within the soil. 



Peraquic moisture regime - A soil condition in which reducing conditions always occur due to the presence 

 of ground water at or near the soil surface. 



Perennial (plant) - Living for many years. 



Periodically - Used herein, to define detectable regular or irregular saturated soil conditions or inundation, 

 resulting from ponding of ground water, precipitation, overland flow, stream flooding, or tidal influences 

 that occur(s) with hours, days, weeks, months, or even years between events. 



Permanentiy flooded - A water regime condition where standing water covers the land surface throughout 

 the year (but may be absent during extreme droughts). 



Permeability - The quality of the soil that enables water to move downward tiirough the profile, measured 

 as the number of inches per hour that water moves downward tiirough the saturated soil. 



Phase, soil - A subdivision of a series based on features such as slope, surface texture, stoniness, and 

 thickness. 



Physiological adaptation - A peculiarity of the basic physical and chemical activities that occur in cells and 

 tissues of a species, which results in it being better fitted to its environment (e.g., ability to absorb nutri- 

 ents under low oxygen tensions). 



Plant community - The plant populations existing in a shared habitat or environment 



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