Status of introduced bureau sensitive, threatened, and endangered species at Greenhill: assessment of mowing damage

In 1999 and 2000, Erigeron decumbens (Willamette daisy, Asteraceae, Federal endangered species), Horkelia congesta (Shaggy horkelia, Rosaceae Federal Species of Concern), Lomatium bradshawii (Bradshaw’s desert parsley, Federal endangered species), and Sericocarpus rigidus (Aster curtus nom., Columbian white topped aster, Federal Species of Concern) individuals were planted and seeded into multiple plots at North Greenhill (managed by the Eugene District Bureau of Land Management). On June 16, 2009, unauthorized mowing by the Oregon Department of Transportation occurred at Greenhill on a large portion of the reintroduction area. The effects of this mowing included damaging foliar cover, cutting mature inflorescences, covering plants with thick clumps of thatch, and scalping the ground. In 2010, we monitored all plots and compared the number of individuals, size, and reproduction of each species in the mowed versus unmowed portions of the site to the most recently available data (2004 and 2009). Mowing appears to have had a negative effect on Sericocarpus; there was a 10% loss of this species from 2009 to 2010 in the unmowed portion of the plot, compared to a 56% loss in the mowed portion of the plot. We did not observe negative effects of mowing on Erigeron, Horkelia, nor Lomatium. We recommend continued monitoring of the site to track ongoing changes in these populations.