Lupinus oreganus in the BLM Roseburg District: Population monitoring and restoration
EXECUTIVE SUMMARY In 2017, we monitored L. oreganus populations by assessing foliar (leaf) cover (a measure of abundance), raceme count, and fruit production at five different sites in the Roseburg
In 2017, we monitored L. oreganus populations by assessing foliar (leaf) cover (a measure of abundance), raceme count, and fruit production at five different sites in the Roseburg BLM District. Foliar cover and raceme count increased from 2016 values at all sites monitored in 2017. Seed set increased at all sites, except Loose Laces, which had the highest recorded seed set for that site in 2016.
This site responded positively to thinning treatments that occurred in the fall of 2009. Cover in 2017 remains high with more than 63m2 of lupine cover in monitored transects. 1,276 racemes were counted in 2017, the highest number since monitoring began. Brush clearing treatments are recommended to maintain suitable habitat for L. oreganus. The population of L. oreganus at China Ditch is the largest population on protected land in Douglas County.
Although a relatively small patch (~20 x 30 m), the L. oreganus at Dickerson Heights occupies nearly all suitable habitat at a junction of two logging roads. L. oreganus responded positively to thinning treatments in 2009. In 2017, fruit production and foliar cover were the highest ever recorded at this site with 7.6 fruits per raceme, and nearly 53m2 of lupine cover.
At Letitia Creek, both foliar cover and raceme count have plummeted since monitoring began in 2003. Since 2006, cover has steadily declined from more than 28 m2 of foliar cover to only 2.9 m2 in 2017. Raceme count has fluctuated since monitoring began starting at the record high of 199, to zero racemes counted in 2014 or 2015. In 2017 only 33 racemes were observed. The decrease in foliar cover, and the low reproductive effort highlight the need for active management of these populations.
Of the four sub-populations at Loose Laces, Sub-population 1 has the highest foliar cover (25.5m2) and generally comprises approximately half of the foliar cover monitored at Loose Laces. In recent years, Sub-population 1 has expanded to the east between the skid road and the main BLM road. The remaining sub-populations have remained relatively stable, with the roadside (Sub-population 3) experiencing the most fluctuation in both foliar cover and raceme count.
One of the two sub-populations at Stout’s Creek appears to have been extirpated. In 2014, only one plant was found in Sub-population 1, and in 2017 no plants were found. Of the four plots in Sub-population 2, three appear to be relatively stable, while the roadside portion has experience drastic decreases in foliar cover and raceme count from more than 15m2 to less than 4m2 in 2017. Road maintenance activities related to the 2015 Stouts’ Creek fire resulted in the removal of top soil and associated plants (including L. oreganus).
Callahan Meadows was not monitored in 2017 due to site access issues.