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United States Department of Agriculture

Agricultural Research Service

Title: Plant-Soil Relationships of the Invasive Annual Grass Taeniatherum caput-meduseae: A reciprocal transplant experiment

Authors
item Blank, Robert
item Sforza, Rene - USDA ARS FRANCE

Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 22, 2007
Publication Date: June 19, 2007
Citation: Blank, R.R., Sforza, R. 2007. Plant-soil relationships of the invasive annual grass Taeniatherum caput-meduseae: A reciprocal transplant experiment. Plant and Soil. 298:7-19.

Interpretive Summary: The annual grass Taeniatherum caput-medusae (medusahead) is highly invasive on rangelands of the western United States. To obtain greater understanding why medusahead is invasive, we conducted a reciprocal transplant experiment using soil and seed from an invasive population in northeastern, California and from a native population in southern France. Seeds were sown in containers (six replicates) for each soil and treatment combination of the reciprocal planting matrix and allowed to grow for 60 days, harvested, and weight recorded. Aboveground tissue was analyzed for nutrient concentrations and various soil nutrient pools were quantified. Aboveground mass of T. caput-medusae was greater when grown in soil from the United States than soil from France and availability of soil Fe, Mn, and ortho-P were significant predictors of plant growth. Our data also suggests that US seed may have evolved a greater ability to uptake Mn from soil than French seed. The invasiveness of T. caput-medusae in our western United States study area may be partially due to elevated nutrient availability.

Technical Abstract: The annual grass Taeniatherum caput-medusae (medusahead) is highly invasive on rangelands of the western United States. It originates from the Mediterranean basin and was introduced accidentally into North America in the late 1800s. To increase our knowledge of the soil factors that may contribute to its invasiveness, we conducted a reciprocal transplant experiment. Seed sources 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 T. caput-medusae; two from southern France, with T. caput-medusae occupied (FR+) and a similar soil presently unoccupied (FR-) by T. caput-medusae. Treatments were control and autoclaved. Seeds were sown in containers (six replicates) for each soil and treatment combination of the reciprocal planting matrix and allowed to grow for 60 days. Following harvest, aboveground and belowground tissue was dried and weight recorded separately. Aboveground tissue was analyzed for nutrient concentrations and various soil nutrient pools were quantified. Aboveground mass of T. caput-medusae was greatest in the USN soil and least in the FR- soil. Growth was affected by significant seed source by soil and treatment by soil 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 than 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 invasiveness of T. caput-medusae. Moreover, the positive effect on growth of T. caput-medusae, due to autoclaving of USI soil, may be a consequence of elevated nutrient availability, rather than the death of inhibitory biological factor(s). Our data also suggests that US seed may have evolved a greater ability to uptake Mn from soil than French seed. The invasiveness of T. caput-medusae in our western United States study area may be partially due to elevated nutrient availability.

Last Modified: 12/20/2014
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