Draft terrestrial resources biological assessment
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- 3.3.1 Relevant Habitat Unit: Vernal Pool Complexes within the Action Area
- 3.3.2 Vernal Pool Complexes and Vegetative Community Associations
- 3.3.3 Soil
- 3.3.4 Hydrology
- 3.3.5 Pollinators
3.3 Plant SpeciesBoth Cook’s lomatium and large-flowered woolly meadowfoam are listed as endangered under the federal ESA. Both species are highly dependent on vernal pool habitat and have experienced dramatic decline in Jackson County due to historic and ongoing industrial, commercial, and residential development, public utility construction and development of utility corridors, land conversion for agricultural uses, weed invasion, roadside spraying, and mowing (USFWS 2011). The historical range of Cook’s lomatium may have encompassed over 50 square miles in the Agate Desert area. The vernal pool habitat upon which this species depends has almost been completely eliminated in Jackson County, Oregon. An estimated 2,300 acres of lomatium habitat is present within the Agate Desert area. However, the 2002 OBIC database showed that the area of known occupied habitat had decreased to an estimated 69 acres within the Agate Desert area (USFWS 2002a, 2002b). Designated critical habitat for both Cook’s lomatium and large-flowered woolly meadowfoam is located within the action area and intersects the project footprint. Within the action area, DCH is located on the west side of the airport property and also is associated with the Denman Wildlife Refuge along Agate Road. DCH for large-flowered woolly meadowfoam is mapped coincidentally with the lomatium DCH near the Denman Wildlife Refuge along Agate road and surrounds West Dutton Road north of the VA hospital. Currently, 23 woolly meadowfoam occurrences are known in the Agate Desert area of Jackson County (USFWS 2011). These occurrences range from five to 200,000 plants. The largest occurrences occupy an approximately 200-acre area of contiguous intact VPC. The smallest occurrence occupies just a few square feet of poor quality wetland, formerly vernal pool habitat. Cook's lomatium is believed to occur at 13 locations in Jackson County (USFWS 2011). Of these occurrences, three are robust and include over 10,000 plants within at least 7-acre areas of intact habitat. The largest occurrence includes over 500,000 plants and the largest area includes 53 acres of suitable habitat. Five of the 13 are small to moderate size and range from 25 to 300 plants. The last five occurrences are small (less than 25 plants) or have not been located in recent years and could be extirpated. Habitat loss is the primary threat to both Cook’s lomatium and large-flowered woolly meadowfoam. Both species are highly dependent on vernal pool wetlands for propagation. As vernal pool habitat is lost due to conversion of natural habitat for commercial and agricultural uses, subsequent habitat fragmentation results in small isolated populations. These small populations become highly susceptible to extinction due to chance events, inbreeding, or additional environmental disturbance (USFWS 2002). Should an extinction event occur in a population that has been fragmented, the opportunities for recolonization are thought to be greatly reduced due to spatial isolation from other (source) populations. Although habitat loss is the primary threat to Cook's lomatium, water projects may have an adverse effect on this species as well. Diversion or blockage of watershed runoff feeding the pools can result in premature dry-down before these plants are able to produce seeds prior to going dormant. Supplemental water from outside the natural watershed into vernal pools can change the habitat into a marsh-dominated or permanent aquatic community where marsh plants may outcompete lomatium (USFWS 2011). 3.3.1 Relevant Habitat Unit: Vernal Pool Complexes within the Action AreaWithin the Agate Desert and the action area, VPCs, are considered suitable habitat for population conservation and recovery for several ESA-listed species. Therefore, they are considered high value habitats. The following sections discuss VPCs within the action area (a definition of VPCs is provided under section 4.1.2). 3.3.2 Vernal Pool Complexes and Vegetative Community AssociationsVernal pool associated species in the Agate Desert include woolly meadowfoam, dwarf meadowfoam (Limnanthes floccosa ssp. pumila), bracted popcornflower (Plagiobothrys bracteatus), and Navarretia spp. (USFWS 2002). These associations are comprised of herbaceous species that are low growing and endemic to the region. 3.3.3 SoilBoth Cook’s lomatium and large-flowered woolly meadowfoam occur only where soil types have a hard pan or clay pan layer close to the soil surface, creating seasonally wet soils and VPCs. The Agate Desert is characterized by shallow, Agate-Winlow soils, a relative lack of trees, sparse prairie vegetation, and agate on the soil surface. The Agate-Winlo soil is a complex of the individual Agate and Winlo series that occur in very close association and are not mappable at the typical scale of the NRCS soil survey. These individual soil series correspond to the patterned ground microtopography that is characteristic of the vernal pool landscape. That is, the Agate series is an upland soil that forms on the upland mounds, whereas the Winlo series corresponds to the low-lying depressions and swales within which vernal pools occur. This Winlo series is listed as hydric by the NRCS (URS 2011a). Both the Agate and Winlo series contain a silica-cemented duripan at depth and it is this duripan that is vital to the development of vernal pools. The permeability of the duripan is very low and therefore this soil horizon restricts the infiltration of rainwater. During the wet season when precipitation exceeds evapotranspiration, rainwater accumulates in soil horizons above the duripan, and is ultimately expressed as surface water in the depressions and swales. 3.3.4 HydrologyVernal pools are seasonal wetlands that form only in regions where specialized soils and climatic conditions exist. During fall and winter rains typical of modified Mediterranean climates, water collects in shallow depressions in areas where downward percolation of water is prevented by the presence of a duripan below the soil surface. Later in the spring when rains decrease and the weather warms, the water both evaporates and percolates downward. The pools generally disappear by May or June. These shallow depressions then remain relatively dry until late fall and early winter when precipitation and cooler temperatures allow water to collect. Vernal pools thus consist of unusual "flood and drought" habitat conditions to which certain plants and animals have specifically adapted. 3.3.5 PollinatorsViable populations of both species depend on flying pollinators to exchange genetic material. Groupings of plants must be within approximately 0.5 mile of each other in order to allow for pollinators to make use of the plants and assist in fertilization and genetic transfer (S. Friedman, personal communication, March 14, 2011). Directory: HWY62 -> Terrestrial BA Terrestrial BA -> Draft Terrestrial Resources Biological Assessment oregon highway 62 corridor solutions project Download 486.24 Kb. Share with your friends:
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