Meghan Skaer writes:
With the support of the Research Exchange Grant, I spent four weeks working with Dr. Maarten Eppinga at Utrecht University in The Netherlands. During this time, we developed a model to help explain competitive interactions in US Western grassland invasive species – focusing on the ‘first wave’ invaders (winter-annual Mediterranean grasses, present ~200 years) and the more recent invaders (spring-annual European grasses, present ~75 years). The newer invaders (New Kids on the Block!) are particularly noxious for cattle ranchers due to high silica content and long awns (protruding ‘spikes’, like those seen on wheat or barley). In fact, one of these new species is called ‘barbed goatgrass’ because of the microscopic, reverse-facing, silica-laden barbs on its awns that can burrow into hooves, fur, and eyes (and these work just as well on humans).
The modified Tilman resource competition model we developed considers water and light as the two primary resources that drive dynamics in this water-limited system. We incorporated a litter feedback that interacts with water availability and seed germination, as well as rain-dependent seed mortality dynamics to more closely model the distributions seen in natural areas. We are currently working on a manuscript that will explain the overall model fit (stable and unstable/founder-control regions) as well as some simulations that will be useful for management of infestations in natural areas.
The two images here show (1) barbed goatgrass (Aegilops triuncialis) with a leaf disease, and (2) the thatch build up from a medusahead grass (Taeniatherum caput-medusae) infestation.