ARS | Publication request: Population level response of downy brome to soil growing medium

Submitted to: Western Society of Weed Science
Publication Type: Abstract Only
Publication Acceptance Date: November 9, 2011
Publication Date: March 15, 2012
Citation: Harmon, D.N., Clements, C.D. 2012. Population level response of downy brome to soil growing medium [abstract]. Western Society of Weed Science. 64:37.

Technical Abstract: Downy brome (Bromus tectorum) is the most ubiquitous exotic invasive weed in the Intermountain West. A major issue for management is the extreme generalist plastic nature of downy brome. We hypothesized that soil growing medium would effect all measured response variables representing some degree of plasticity. In a greenhouse reciprocal garden we tested two treatment variables 1) seed source population (n=5) and 2) soil type (n=5). We measured four response variables; 1) total biomass, 2) seed to total biomass ratio, 3) days to flowering, and 4) total life duration. Our results found that biomass differed by soil type and seed source. Seed to total biomass ratios responded to one soil type. Plants exhibited lower resource allocation to seed production when grown in sandy soils. Downy brome seed from salt desert/black greasewood (Sarcobatus vermiculatus) habitat displayed the highest percent of seed to total biomass. Days to flowering differed by seed source. High elevation seed source exhibited delayed flowering. Total life span differed by seed source and soil type. The most noticeable response was the long life span of some individual plants from the higher elevation seed sources (10+ months). While most of the results concur with previous findings, the population level fixed biomass response has not been reported before. High elevation downy brome seed produced larger plants. Downy brome seed from salt desert/black greasewood habitat produced plants with a smaller comparative biomass. Population level biomass differences could have important wildfire fuels management implications.