ARS | Publication request: Downy Brome: evidence for soil engineering

Submitted to: Western Society of Weed Science
Publication Type: Abstract Only
Publication Acceptance Date: February 17, 2012
Publication Date: July 3, 2012
Citation: Blank, R.R., Morgan, T.A. 2012. Downy Brome: evidence for soil engineering [abstract]. Western Society of Weed Science. 65:15.

Technical Abstract: Bromus tectorum L. (downy brome, cheatgrass) is an invasive Eurasian grass largely responsible for landscape level conversion of sagebrush/bunchgrass communities to annual grass dominance. We tested the hypothesis that B. tectorum alters or “engineers” the soil to favor its growth. The hypothesis was tested in a greenhouse using rhizotrons filled with either soil invaded by B. tectorum for 6 years or a similar soil not yet invaded. Seeds of B. tectorum (6 replicates) were sown in either invaded or non-invaded soil and allowed to grow for 70 days. Response variables were above-ground mass, root mass at selected depths, and several soil attributes. The experiment was conducted over two growth cycles. After the 1st growth cycle, B. tectorum above-ground mass was 189% greater when grown in invaded soil relative to the non-invaded soil. The soil variable, which explained 54% of B. tectorum growth, was the molar proportion of nitrite in the nitrate + nitrate extractable pool. These data, in addition to results of field experiments, suggest long-term occupation of a soil by B. tectorum facilitates greater N mineralization and reduces the kinetics of microbial nitrite to nitrate transformation. We conjecture that B. tectorum may have efficient nitrite root transport system(s). Overall, our data support the hypothesis that occupation of a soil by B. tectorum, overtime, facilitates an increase in its growth potential.