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.
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 | ||||
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Scientific & Common Name | Global & State Rank | Ecoregion* | ||
Alopecurus saccatus-Plagiobothrys bracteatus Vernal Pool [Provisional] Saccate foxtail-bracted popcorn flower (Titus 1996-1998: 6) |
G2S2 | KM | ||
Camassia quamash - Triteleia hyacinthina Vernal Pool [Provisional] Common camas - hyacinth triteleia (Borgias 2004, App. 3: 10) |
G1S1 | KM | ||
Danthonia unispicata - Poa secunda Wet Meadow One-spike oatgrass - Canby's bluegrass (Björk 2011: 25; NS) |
G3S2 | BM, EC | ||
Deschampsia danthonioides Vernal Pool [Provisional] Annual hairgrass (Titus 1996-98: 5; Borgias 2004, App. 3: 10) |
G2S2 | KM | ||
Deschampsia danthonioides - Danthonia unispicata Vernal Pool [Provisional] Annual hairgrass - onespike oatgrass (Johnson & Simon 1987) |
G3S2 | BM | ||
Deschampsia danthonioides - Lasthenia californica Vernal Pool [Provisional] Partridgefoot - Tolmie saxifrage (NS) |
G1S1 | KM | ||
Deschampsia danthonioides - Plagiobothrys leptocladus Herbaceous Vegetation [Provisional] Annual hairgrass - slender-branched popcorn flower (Meinke & Magee 1986: 34) |
G2S2 | CB | ||
Downingia elegans Herbaceous Vegetation [Provisional] Common downingia |
G2S1 | WV | ||
Downingia yina Vernal Pool [Provisional] Willamette downingia (Titus 1996-1998: 5; Borgias 2004, App. 3: 10) |
G2S2 | KM | ||
Downingia yina - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional] Willamette downingia-bracted popcorn flower |
G2S2 | KM | ||
Eryngium petiolatum - Grindelia nana Vernal Pool Coyote-thistle - low gumweed (NS) |
G1S1 | KM | ||
Eryngium petiolatum - Lasthenia glaberrima Vernal Pool Coyote-thistle - smooth lasthenia (Borgias 2004, App. 3: 10; NS) |
G1S1 | KM | ||
Eryngium petiolatum - Navarretia leucocephala ssp. leucocephala Vernal Pool [Provisional] Coyote-thistle - white flowered navarretia (Borgias 2004, App. 3: 10) |
G1S1 | KM | ||
Gratiola ebracteata - Plagiobothrys bracteatus Herbaceous Vegetation [Provisional] Bractless hedge-hyssop - bracted popcorn flower |
G2S2 | KM | ||
Isoetes bolanderi Vernal Pool [Provisional] Bolander's quillwort (Titus 1996-1998: 6) |
G1S1 | KM | ||
Isoetes nuttallii Wet Meadow Nuttall's quillwort (Christy 2004: 123; NS) |
G3S3 | WV | ||
Isoetes nuttallii - Plagiobothrys bracteatus Vernal Pool [Provisional] Nuttall's quillwort-bracted popcorn flower (Titus 1996-1998: 6) |
G2S2 | KM | ||
Marsilea oligospora - Eleocharis acicularis Vernal Pool [Provisional] Pacific waterclover - needle spikerush (Björk 2011: 26) |
G2S2 | EC | ||
Navarretia intertexta - Polygonum polygaloides spp. kelloggii Vernal Pool [Provisional] Needle-leaf navarretia - Kellogg knotweed (Johnson & Simon 1987: 224) |
G2S2 | KM | ||
Navarretia leucocephala ssp. leucocephala Vernal Pool [Provisional] White flowered navarretia (Borgias 2004, App. 3: 10) |
G2S2 | KM | ||
Navarretia leucocephala ssp. minima - Polygonum polygaloides ssp. confertiflorum [Provisional] Least navarretia - closeflowered knotweed (Björk 2011: 25) |
G2S2 | EC | ||
Plagiobothrys figuratus Vernal Pool Fragrant popcorn-flower (NS) |
G1S1 | WV | ||
Plagiobothrys leptocladus - Veronica peregrina Vernal Pool [Provisional] Slender-branched popcorn flower - purslane speedwell (Meinke & Magee 1986: 34) |
G2S2 | CB | ||
Psilocarphus brevissimus Vernal Pool [Provisional] Dwarf wooly-heads (Titus 1996-1998: 5) |
G2S2 | KM |