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

Executive Summary

This report documents monitoring conducted on population characteristics and habitat of Kincaid’s lupine (Lupinus oreganus), a threatened species, 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 Oregon prairies. In 2017, the twelfth year of monitoring occurred at Oak Basin, which is managed by the Eugene District Bureau of Land Management.

• Kincaid’s lupine: In 2017, Kincaid’s lupine cover doubled from 2016 in all meadows to 152m². The total number of mature racemes increased to over 3,600 mature racemes, while the number of aborted racemes decreased from 18% in 2016 to 3%. Despite these increases, the cover and reproduction 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. Population monitoring inside and outside of management treatment areas can inform habitat management for this, and other species which share this unique upland prairie habitat.
• Habitat quality: In 2017, as in previous years, there was high cover of exotic grasses (>75% cover) including Schedonorus arundinaceus, Dactylis glomerata, and Cynosurus echinatus. These non-native species were the most prevalent while the exotic forb, Leucanthemum vulgare, encompassed over 15% cover. Cover of native forbs remained relatively stable with <20% cover, with Eriophyllum lanatum the dominant species. Species richness decreased from 2011-2015 with 105 species observed in 2011, 82 in 2015, and 66 species observed in 2017.  Meadows A has seen the largest decrease in species richness from 85 to 38 species.
• Management treatments: Management treatments conducted in 2013-2017 included mowing to control exotic perennial grasses and shrubs, flame weeding, limbing of larger trees, and removal of conifers <4” DBH to increase meadow connectivity and reduce encroachment. In 2015 and 2016, it was observed that flame-weeded areas had lower cover of invasive graminoid species, and higher native graminoid cover than adjacent untreated areas. In Meadow B, areas that had been flame-weeded had higher cover of native forb species than untreated areas. Mowing treatments in Meadow A in 2015 and 2016, did not have a clear effect on cover of native or exotic grasses or forbs. Mowing treatments in all meadows appeared to result in higher foliar cover and raceme production in all meadows. Monitoring in 2018 will inform longer term effects of flame weeding, mowing, and other management treatments.

Sisyrinchium hitchcockii: Long-term monitoring plots for S. hitchcockii were added to Meadow C in 2012, and monitoring has been conducted from 2012-2017.  Since 2012, the population declined from a total of 122 to just 42 in 2016. In 2017, numbers increased to 66 individuals. The number of reproductive stems has also decreased from 128 in 2012 to 19 in 2016. The decline in reproductive effort of both L. oreganus and S. hitchcockii, and subsequent increase in 2017 for both species,  suggest that some shared factor, such as climate factors and/or competition with exotic species 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.