ARS | Publication request: THE INVASIVE ANNUAL GRASS TAENIATHERUM CAPUT-MEDUSAE: A RECIPROCAL TRANSPLANT EXPERIMENT

Submitted to: Western Society of Weed Science
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2005
Publication Date: March 1, 2006
Citation: Blank, R.R., Sforza, R. 2006. The invasive annual grass taeniatherum caput-medusae: a reciprocal transplant experiment [abstract]. Annual Meeting of the Western Society of Weed Science. March 14-17, 2006, Reno, Nevada.

Technical Abstract: The annual grass T. caput-medusae (medusahead) is highly invasive on rangelands of the western United States. To increase our knowledge of the soil factors that may contribute to its invasiveness, we conducted a reciprocal planting experiment. Seeds used were from an invasive population in northeastern California, USA and from a native population in southern France. Four soils were used: two from northeastern, California, invaded (USI) and non-invaded (USN) by medusahead; two from southern France, with medusahead occupied (FR+) and a similar soil presently unoccupied (FR-) by medusahead. Treatments were control and autoclaved. Six replicate seeds were sown in each soil of the reciprocal planting matrix and allowed to grow for 60 days. Following harvest, aboveground tissue was dried, weight recorded, and analyzed for nutrient concentrations and various soil nutrient pools were quantified. Aboveground mass of medusahead was greatest in the USN soil and least in the FR- soil. Growth was affected by significant seed source by soil type and treatment by soil type interactions. For the USN soil, French seed produced larger plants than did US seed. For the USI soil, plant growth was significantly greater in the autoclaved soil relative the control and US seed performed superior to the French seed in that treatment. Availability of soil Fe, Mn, and ortho-P were significant predictors of plant growth as shown by stepwise regression and suggests that their greater availability in US soils may contribute to the invasivness of medusahead. Moreover, that autoclaving of USI soil had such a positive effect on the growth of medusahead, may not be due to death of inhibitory biological factors, but rather increased nutrient availability. Our data also suggests that US seed may have evolved a greater ability to uptake Mn from soil than French seed.