Oaks in the vicinity of Sheldon Creek (Section 32). 



There are stands of oak {Quercus macrocarpa) on both BLM and private land in this section, 

 and precise location of the population is not known. The small BLM tract in section 32 was 

 not visited in 1997. Habitat matching the label description on BLM land in adjoining section 

 31 was surveyed in 1997, but Linaria canadensis was not found, nor was the species found 

 elsewhere in the county. 



HABITAT: Throughout its range, Linaria canadensis commonly grows in sandy soils (Great Plains 

 Flora Association 1986, Hitchcock and Cronquist 1973), but the Alzada Oaks population is on clay 

 derived from Mowry shale. Several plant species and communities typically found in sandy habitats 

 follow this pattern, for example both ponderosa pine (Pinus ponderosa) and prairie sandreed 

 (Calamovilfa longifolia) are community dominants on both shale and sand substrates in Carter 

 County. 



The vegetation in the same section as the occurrence is woodland with a mixture of Rocky Mountain 

 juniper {Juniperus scopulorum), bur oak {Quercus macrocarpa), and ponderosa pine {Pinus 

 ponderosa). Associated forbs include the annuals Torrey's cryptantha {Cryptantha torreyana), 

 white-stemmed mentzelia {Mentzelia albicaulis), bushy mentzelia {Mentzelia dispersa) and six- 

 weeks fescue {Vulpia octojlora). Undergrowth in this oak woodland is sparse, but with a high 

 diversity of annuals: eight species were found in a 1/10 acre plot (see discussion oi Quercus 

 macrocarpa/Juniperus scopulorum in the ecology section of this report). The bentonitic substrates of 

 these woodlands are droughty and have high shrink-swell potential, thus inhibiting growth of many 

 perennial forbs. Many annuals are adapted to the low levels of competition created by severe 

 conditions, and survive these conditions by remaining dormant as seeds in unfavorable years or 

 times of the season. 



SPECIES BIOLOGY: In June of 1986 when it was collected, the population was estimated to 

 consist of 100-1,000 plants in flower and with fruit. Populations of annuals often undergo dramatic 

 fluctuations in response to climate, and may remain dormant as seedbanks in unfavorable years. Blue 

 toadflax is a winter annual (Great Plains Flora Association 1986), thus seed germination and 

 seedling development are most affected by soil moisture availability in the fall. 



OTHER COMMENTS: Occurrence oi Linaria canadensis on BLM land in Carter County has not 

 been confirmed. BLM Sensitive status of Quercus macrocarpa potentially provides some protection 

 of potential habitat for Linaria canadensis in Carter County. Conservation management of BLM oak 

 woodlands as rare native plant associations will provide more protection for native understory plant 

 species. The primary threats to these communities are livestock grazing, bentonite mining and 

 associated roads, and the weed infestations that are potentially facilitated by these activities. Native 

 annuals are often adapted to disturbance, but these events also promote introductions of exotic 

 species, which may be more competitive. Lacking information on precise location, land ownership, 

 and population viability of the Alzada oaks population, retention of current BLM Watch status of 

 Linaria canadensis is appropriate. 



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