Submitted to: Wildland Shrub Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: June 15, 2007
Publication Date: September 1, 2008
Citation: Blank, R.R., Sforza, R., Morgan, T.A. 2008. Medusahead: available soil N and microbial communities in native and invasive soils. In: Kitchen, Stanley G.; Pendleton, Rosemary L.; Monaco, Thomas A.; Vernon, Jason, comps. Proceedings of Shrublands under fire: disturbance and recovery in a changing world, June 6–8, 2006, Cedar City, Utah. RMRS-P-52. Interpretive Summary: Invasion of western United States rangelands by medusahead (Taeniatherum caput-medusae) is causing loss of forage, loss of biodiversity, and increased risk of wildfires. We contrasted soil properties between native sites in Eurasian and invaded sites on clay-textured soil on the volcanic tablelands of northeastern CA, USA. High available soil nitrogen can be a predictor of invasion risk; however, there were no differences in levels of available nitrogen between native and invasive soils. In addition, the soil microbial community structure between a native site in southern France and an invaded site in northeastern, CA, USA were remarkably similar. In summary, there is no definitive evidence in the studies carried out to indicate why medusahead is invasive in the western United States.
Technical Abstract: To better understand why medusahead (Taeniatherum caput-medusae) is invasive, we quantified soil N availability and characterized soil microbial communities between native and invasive populations. No consistent differences in soil N mineralization potentials were noted between native medusahead sites in Spain, Turkey, France, and Greece and two invaded sites on the volcanic tablelands of northeastern, California, U.S.A. The proportional makeup of the microbial community, as quantified by phospholipid fatty acid analysis (PLFA), did not differ appreciably between a native site in southern France and one site on the tablelands of northeastern, CA sites. Microbial markers indicative of growth phase suggest soils of invasive populations have higher turnover rates than native soil. No useable DNA could be extracted from the native medusahead soil in southern France using bacterial S16 ribosomal DNA. Tablelands soil contained distinct bacterial DNA bands for bacteria that utilize methane and methanol, anaerobically reduce sulfur, catabolize aromatics, for symbiotic relationships with root nodules of legumes. In summary, there is no definitive evidence in the studies carried out to indicate why medusahead is invasive in the western United States.