Submitted to: Wildland Shrub Symposium Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: January 1, 2006
Publication Date: June 1, 2006
Citation: Blank, R.R., Sforza, R., Morgan, T.A. 2006. Medusahead: soil nitrogen and microbial community dynamics in native and invasive populations [abstract]. Proceedings 14th Wildland Shrub Symposium - Shrublands Under Fire, June 6-8, 2006, Cedar City, Utah. Technical Abstract: Invasion by the annual grass medusahead (Taeniatherum caput-medusae) on western North America rangelands has, through direct competition and increased risk of wildfire, contributed to the loss of low sagebrush communities. We investigated differences in soil N availability and soil microbial communities between native and invasive medusahead populations to understand why medusahead is invasive and find potential means to reduce its invasiveness. There were no consistent trends in either soil N availability or N mineralization potentials between native medusahead sites in Spain, Turkey, France, and Greece and two invaded sites on the volcanic tablelands of northeastern, CA. This fact suggests invasion cannot be solely explained by differences in N availability between native and invaded sites. Next we compared soil microbial community structure between a native site in France and one site on the tablelands of northeastern, CA using phospholipid fatty acid biomarkers. Although the French site had far greater microbial biomass (it is a moister and less harsh environment), the proportional makeup of the microbial community did not differ between the sites. This finding is surprising given the great differences in biometeorology between the sites. We also extracted bacterial S16 ribosomal DNA from both populations. Unfortunately, no useful DNA could be extracted from the French soil. The tablelands soil contained six distinct bacterial DNA bands: methane and methanol utilizers, anaerobic sulfur reducers, strong catabolic potential for aromatics and root nodule legumes. Some of these bacteria seem out of place for this arid environment. In summary, there is no definitive evidence in the studies carried out to indicate why medusahead is invasive in western North America.