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Waterfowl Production on the Woodworth Station
in South-central North Dakota, 1965-1981

Wetlands


Wetlands on the study area were classified almost annually during July-September according to Stewart and Kantrud (1971). Five natural and nine disturbed classes of wetlands occurred on the study area. Natural wetlands included Class I ephemeral potholes; Class II, temporary potholes; Class III, seasonal potholes; Class IV, semipermanent potholes; and Class V, permanent potholes.

Classes of disturbed wetlands included those tillaged and human-made. Classes of wetlands altered by tillage and usually located in cropland fields or fields seeded, to tame grasses and legumes included Class It, tilled ephemeral; Class IIt, tilled temporary; and Class IIIt, tilled seasonal. The superscript t identifies that the natural classes of these ponds can be recognized, but that 50% or more of the central zone of the wetland basin was occupied by emergent plant associations characteristic of tilled conditions. Other artificial classes in tilled wetlands included T-4 summer fallow (bare soil), T-3 mulched stubble, and T-2 standing stubble. For these ponds, a capitol letter T was substituted for the class number because the natural class could no longer be recognized. The names such an mulched stubble describe the vegetation.

Human-made water areas included dugouts, stock water dams, and recreational impoundments. The dugouts were deep excavations, 15 x 30 m or less, located in drainages or seepages. Stock water dams were dirt dams constructed across natural drainage ditches. Neither dugouts nor stock water dams inundated natural wetland basins. Recreational impoundments included natural wetlands with human-made dirt dams constructed on the natural overflow drainages from wetland basins. During years of high runoff, these dams caused higher water levels in the existing natural wetland basins; during dry years, the wetlands were, in a sense, natural.

All wetlands on the study area were Subclass A (fresh) to B (slightly brackish) ponds (Stewart and Kantrud 1971). These were combined because plant species characteristic of relatively fresh water predominated. Average salinity differences for fresh to slightly brackish surface waters are classified by Stewart and Kantrud (1971) according to normal and extreme ranges of specific conductance (micromhos per cubic centimeter). Indicators of differences in average salinity are: fresh, normal (<40-500) and extreme (<40-700); slightly brackish, normal (500-2,000) and extreme (300-2,200). The lowest and highest specific conductance readings in wetlands on the study area were 470 and 1,650 µmhos/cm³, respectively.


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