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Wetlands

Vernal Pools

Vernal pool, Rowena Plateau, Wasco County

Vernal pool, Rowena Plateau, Wasco County
(John A. Christy, Oregon Biodiversity Information Center)

Vernal pools are one of Oregon's rarest wetland types. They form on impervious basalt bedrock or on soils cemented by a calcareous or siliceous hardpan that impedes drainage. Pools can range in size from an acre (0.4 hectares) or more to patches as small as 10-225 square feet (1-5 square meters), and may occur singly or in groups covering many acres. They usually fill with water in the fall or winter and dry up in spring or early summer, but seasonal precipitation may be highly variable and pools may fill for only brief periods or not at all. They are home to a large variety of plants and animals adapted to these harsh conditions, and some species are rare globally. Vernal pools are threatened primarily by urban or suburban development on the typically flat and easily accessible landforms in which they occur.

Vernal Pools Map

Vernal Pools



Habitat: Small to large depressions on flats or irregular surfaces, drainage 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 Alopecurus saccatus-Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Saccate foxtail-bracted popcorn flower
G2S2 KM
wetland type image Deschampsia danthonioides Herbaceous Vegetation [Provisional]
Annual hairgrass
G2S2 KM
wetland type image Deschampsia danthonioides - Plagiobothrys leptocladus Herbaceous Vegetation [Provisional]
Annual hairgrass - slender-branched popcorn flower
G2S2 CP
wetland type image Downingia elegans Herbaceous Vegetation [Provisional]
Common downingia
G2S1 WV
wetland type image Downingia yina - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Willamette downingia-bracted popcorn flower
G2S2 KM
wetland type image Gratiola ebracteata - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Bractless hedge-hyssop - bracted popcorn flower
G2S2 KM
wetland type image Isoetes nuttallii - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Nuttall's quillwort-bracted popcorn flower
G2S2 KM
wetland type image Lasthenia californica Herbaceous Vegetation [Provisional]
Goldfields
G3S2 KM
wetland type image Myosurus minimus - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Mousetail - bracted popcorn flower
G2S2 KM
wetland type image Navarretia intertexta - Polygonum kelloggii Herbaceous Vegetation [Provisional]
Needle-leaf navarretia - Kellogg knotweed
G2S2 KM
wetland type image Navarretia leucocephala - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional]
Navarretia - bracted popcorn flower
G2S2 KM
wetland type image Plagiobothrys bracteatus - Veronica peregrina Herbaceous Vegetation [Provisional]
Bracted popcorn flower - purslane speedwell
G2S2 KM
wetland type image Plagiobothrys figuratus Herbaceous Vegetation
Fragrant popcorn-flower
G1S1 WV
wetland type image Plagiobothrys leptocladus - Veronica peregrina Herbaceous Vegetation [Provisional]
Slender-branched popcorn flower - purslane speedwell
G2S2 CB
wetland type image Psilocarphus brevissimus Herbaceous Vegetation [Provisional]
Dwarf wooly-heads
G2S2 KM
wetland type image Triteleia hyacinthina -Deschampsia danthonioides Herbaceous Vegetation [Provisional]
Hyacinth brodiaea - annual hairgrass vernal pool
G2S2 KM

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