December 9, 2014

Population and habitat monitoring for Kincaid’s lupine and Hitchcock’s blue-eyed grass at Oak Basin

Denise Giles-Johnson, Erin C. Gray, and Tara Callaway | 2014

This report documents research conducted on population dynamics and habitat for of Kincaid’s lupine (Lupinus oreganus), a threatened species in the legume family, and Hitchcock’s blue-eyed grass (Sisyrinchium hitchcockii), a

This report documents research conducted on population dynamics and habitat for of Kincaid’s lupine (Lupinus oreganus), a threatened species in the legume family, and Hitchcock’s blue-eyed grass (Sisyrinchium hitchcockii), a federal species of concern, at Oak Basin. Kincaid’s lupine serves as the primary larval host plant for the endangered Fender’s blue butterfly (Icaricia icarioides fenderi). Both species are endemic to western prairies. In 2014, the ninth year of monitoring occurred at Oak Basin, which is managed by the Eugene District Bureau of Land Management.

  • Kincaid’s lupine: After the alarming decline observed in 2013, lupine cover and mature inflorescences recovered to pre-crash levels in 2014. Lupine cover improved considerably to 150m² (in 2014) from 74m² (in 2013); coinciding with elevated cover, total mature inflorescences increased greatly from 195 (in 2013) to 2,046 (in 2014). Mature racemes per m² increased in all meadows, while aborted inflorescences plummeted to only 3% in 2014. The population dynamics of Kincaid’s lupine at Oak Basin have varied substantially from year to year and should be continually monitored to decipher the factors impacting the fluctuations which could include climate differences, competition from invasive species and/or habitat degradation.
  • Habitat quality: In 2014, the Oak Basin habitat once again had high proportions of exotic species cover with 79% exotic and only 21% native cover. While the percent cover of native and exotic species has not fluctuated greatly over the years, functional group cover has varied from 2011-2014. Dominance by exotic species was most evident in the grass functional group comprising 59% of the total cover, followed by 19% exotic forb cover, in comparison to 12% native forb and 7% native grass cover in 2014. Exotic grasses including Dactylis glomerata, Festuca arundinacea, and Cynosurus echinatus, were the most prevalent species in lupine and non-lupine habitat, while the exotic forb, Leucanthemum vulgare, encompassed over 20% cover in both habitats. Species richness increased 21% across all three meadows, with 80 species present as compared to only 72 and 65 species in 2012 and 2013, respectively. Meadow C contained the highest species richness with 65 total species, and Meadow A and B had slightly lower total species with 60 and 54, respectively.
  • Sisyrinchium hitchcockii: Long-term monitoring plots for hitchcockii were added to Meadow C in 2012; monitoring was conducted in 2012, 2013, and 2014 and will continue annually. In 2014, a total of 225 inflorescences and 26 vegetative plants were recorded. Overall, reproductive effort was much greater in 2014 than in 2013, while vegetative plants decreased 45% from 2013 to 2014. A favorable year for the reproductive effort of both L. oreganus and S. hitchcockii suggest that some shared factor, such as climate could be impacting the success of these populations. Continued monitoring will be essential to document annual population variability to inform future management activities and the perpetuation of these rare species.
  • Management treatments: Management treatments conducted in 2013 and 2014 included mowing to control exotic perennial grasses and shrubs, limbing up of larger trees, and removal of smaller trees to increase meadow connectivity and reduce encroachment. Flame weeding was utilized to control both annual and perennial exotic species, followed by plug planting and direct seeding in treated areas. Hand removal of weedy species including grubbing of blackberries also occurred. Personal observations from the 2014 crew witnessed lupine proliferation occurring under recently opened up meadows via limbing and mowing. In future years, a community monitoring scheme targeted at areas of management will be essential to track plant community response from such actions.