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Item 7.1 Att 4 (5) Ex A - Final_EACCS_Oct2010_Print - City of Dublin

Item 7.1 Att 4 (5) Ex A - Final_EACCS_Oct2010_Print - City of Dublin

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Appendix D<br />

Species Accounts<br />

Species Associated with Big Tarplant<br />

Grindelia camporum<br />

Holocarpha obconica<br />

Holocarpha virgata<br />

Lagophylla ramosissima<br />

Lolium multiflorum<br />

Nassella pulchra<br />

Great Valley gumplant<br />

San Joaquin tarplant<br />

virgate tarplant<br />

common hareleaf<br />

Italian ryegrass<br />

purple needlegrass<br />

Threats<br />

Big tarplant occurs in only a few highly restricted populations and is considered<br />

seriously endangered in California (CNPS List 1B.1) (CNPS 2009). The primary<br />

threat to big tarplant has been habitat loss from conversion to urban<br />

development and lack <strong>of</strong> disturbance in areas where natural processes are<br />

restricted. Ground disturbance and erosion caused by cattle grazing and<br />

competition from invasive exotics such as yellow star-thistle (Centaurea<br />

solstitialis) may also pose a threat to populations (CNDDB 2009).<br />

Modeled Habitat Distribution in Study Area<br />

Model Assumptions<br />

Model Results<br />

The big tarplant habitat model includes the following parameters: annual<br />

grassland land cover, soils consisting <strong>of</strong> clay and clay loam, elevations up to<br />

1,827 feet, and on slopes <strong>of</strong> 10-31 degrees. The model restricts habitat to those<br />

areas within the Diablo Range that are underlain by Great Valley Sequence<br />

geologic landforms.<br />

Figure D-3 in Appendix D shows the modeled potential habitat for big tarplant<br />

within the study area. Potential habitat is restricted to areas in the Diablo Range<br />

with parent material from the Great Valley Sequence (Bartosh pers. comm.).<br />

Known occurrences are generally within the vicinity <strong>of</strong> predicted habitat. The<br />

exception is the population along Midway Road near the Alameda/San Joaquin<br />

County line, which does not fall within the modeled habitat. The small number<br />

<strong>of</strong> clustered occurrence in the study area is not sufficient to provide a high level<br />

<strong>of</strong> confidence in the model results.<br />

East Alameda County Conservation Strategy D-7 October 2010<br />

ICF 00906.08

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