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ARS Home » Pacific West Area » Reno, Nevada » Great Basin Rangelands Research » Research » Publications at this Location » Publication #342311

Title: Why is Taeniatherum caput-medusae (medusahead) Invasive in North America and not in its Native Eurasia?

item Morgan, Tye
item O'NEIL, MATTHEW - University Of California
item Blank, Robert - Bob
item ALLEN, EDITH - University Of California
item ALLEN, MICHAEL - University Of California

Submitted to: Soil Ecology Society Conference
Publication Type: Abstract Only
Publication Acceptance Date: 4/2/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: None

Technical Abstract: Taeniatherum caput-medusae (medusahead grass) is an exotic annual grass introduced to North America (NA) that has invaded ~ 4 million ha of western rangelands. In contrast, in native ranges of Eurasia (EA), medusahead is not considered to be invasive. Why is medusahead invasive in NA, but not in its native lands in EA? We considered two prominent hypotheses: enemy release and soil resource availability. We hypothesized: 1)Medusahead-invaded soils of NA are more fertile than native soils in EA and thus support invasion; 2)Invaded soils of NA have a lower rate of infection of pathogenic organisms, which in native environments reduce the growth and invasiveness of medusahead. We designed a project to test the effects of soil, seed source, inoculum treatments on biomass, arbuscular mycorrhizae, and pathogen root counts of medusahead. In general, NA soils had higher levels of nutrients than the EA soils. The NA populations, regardless of soil origin, generally had higher biomass responsiveness to both filtrate and whole soil inoculum. EA populations tended to have higher or equal biomass in sterile soils than inoculated or filtrate soils. For both NA and EA populations, biomass in sterile soils was related to soil nutrients rather than continent of origin. Microscopic observations showed higher pathogen counts in EA populations. Microbial communities from filtrate and whole soil treatments in NA soils enhanced plant growth, while microbial communities in EA soils had reduced or neutral growth. Results conclude that both resource availability and enemy release hypotheses support medusahead invasions in NA.