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Wet Prairies and Wet Rock Outcrops

Wet Prairie, Willamette Floodplain RNA, Benton County

Wet Prairie
(John A. Christy, Oregon Biodiversity Information Center)

Wet prairies are one of Oregon's rarest wetland types. Most occur at lower elevations on bedrock or clay loam soils that have a seasonally perched water table. These sites usually dry out by late spring but depressions may retain water well into the summer. Shallow soils over bedrock, and rock outcrops are included as part of this habitat because they are often intermixed with clay soil sites and the same vegetation may occur on both substrates (e.g., Isoetes nuttallii, Triteleia hyacinthina). There is also some overlap with vernal pool vegetation. Wet prairie in the Willamette and Umpqua valleys are habitat to several rare species of plants. Although best known for tufted hairgrass (Deschampsia caespitosa), wet prairies contain many other species of grasses, sedges and herbs. Before flood control, wet prairies on the Columbia River bottoms were flooded for one or two months every year during the annual "spring freshet" fueled by snowmelt in the Columbia Basin. Most wet prairies have been drained, farmed, grazed, or overrun by exotic species.

Wet Prairie Map

Wet Prairie Map





 

Habitat: Flats, irregular surfaces, and depressions constrained by bedrock or hardpan
Water regime: Intermittently to seasonally flooded
Water chemistry: Fresh

Ecoregion*: BM = Blue Mountains, BR = Northern Basin and Range, CB = Columbia Basin, CR = Coast Range, EC = East Cascades, KM = Klamath Mountains, WC = West Cascades, WV = Willamette Valley  
  Scientific & Common Name Global & State Rank Ecoregion*
wetland type image Camassia quamash Lowland Wet Prairie
Common camas (Christy 2004: 78; NS)
G3S3 KM, WV
wetland type image Carex aperta Lowland Wet Meadow
Columbia sedge (Murray 2000: 14; Christy 2004: 81; NS)
G1S1 WC, WV
wetland type image Carex densa - Deschampsia caespitosa Wet Prairie
Dense sedge - tufted hairgrass (Christy 2004: 87, corrected; NVC)
G2S2 KM, WV
wetland type image Carex feta Wet Prairie [Provisional]
Green-sheath sedge (Christy 2004: 89)
G3S2 WV
wetland type image Carex pachystachya Wet Prairie [Provisional]
Thick-headed sedge (Christy 2004: 97)
G3S2 WV
wetland type image Carex unilateralis - Hordeum brachyantherum Wet Prairie
One-sided sedge - meadow barley prairie (NS)
G2S2 KM, WV
wetland type image Deschampsia caespitosa - Artemisia lindleyana Wet Prairie
Tufted hairgrass - Columbia River wormwood (Christy 2004: 107; NS)
G1S1 WC
wetland type image Deschampsia caespitosa - Danthonia californica Marsh
Tufted Hairgrass - California Oatgrass (Titus 1996-1998: 2; Christy 2004: 108; NS)
G2S2 WV, KM
wetland type image Eleocharis palustris - Carex unilateralis Wet Meadow
Creeping spikerush - one-sided sedge (NS)
G2S2 WV
wetland type image Isoetes nuttallii Wet Meadow
Nuttall quillwort (Christy 2004: 123; NS)
G3S3 WV
wetland type image Micranthes ferruginea - Camassia quamash Wet Outcrop [Provisional]
Rusty saxifrage - Common camas (Glavich 2016: 44)
G4S3 CR, WC
wetland type image Rosa nutkana / Deschampsia caespitosa Wet Shrubland [Provisional]
Nootka rose / tufted hairgrass (Pendergrass 1989)
G2S2 WV
wetland type image Rosa nutkana / Oenanthe sarmentosa Shrubland
Nootka rose / water parsley shrub swamp (NS)
G2S2 WV
wetland type image Triteleia hyacinthina Wet Outcrop [Provisional]
Hyacinth brodiaea (Christy 2004: 148)
G2S2 KM, WV

Authored by John A. Christy, Wetlands Ecologist, (ORBIC) Oregon Biodiversity Information Center (2012 rev. 2017)

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