USC Dana and David Dornsife College of Letters, Arts & Sciences > Blog

July 9, 2012

Invasive Plants

Filed under: Uncategorized — Tags: , , , — sholle @ 10:29 pm

Environmental problems are complex entities which take a broad set of skills and understanding to properly address and mitigate. On Catalina Island three interns and I from USC are getting experience working with various conservation organizations seeing firsthand what it takes to properly preserve valuable and productive ecosystems. Last week we worked with Peter Dixon who is in charge of the native plant nursery on Catalina Island. From the early morning until the late afternoon we spent our time touring various ecosystems around Catalina Island looking for California Locoweed (Astragalus trichopodus var. lonchus), Vernal Barley (Hordeum intercedens), Fragrant Pitcher Sage (Lepechinia fragrans) and Black Sage (Salvia melifera). When we found the flora species of interest our group harvested 10% of the seed from each plant and counted maternal lines in order to keep track of the genetic diversity. All this work goes toward maintaining a viable seed bank, which is necessary for restoration and the retention of native and endemic species on Catalina. One of the species, Hordeum intercedens is a relatively rare grass on the island and proved to be especially difficult to locate given the abundance of similar invasive grasses.

Above: USC students survey a watershed on the east side of Santa Catalina Island. Photo Credit: Stephen Holle

Seed collection is especially important because grasses like H. intercedens face an immense amount of competition from invasive grasses, which often times have more dense and broad distributions. Invasive grasses are one of many environmental problems on Catalina Island because their biomass contributes large amounts of nitrogen to the soil, which further promotes the spread of invasive plants such as fennel. A possible explanation for the persistence of invasive species on Catalina Island could be due to the increased influxes of nitrogen from invasive grasses and other plant species. As Peter Dixon explains, “native and endemic grasses on Catalina are typically found in dispersed distributions while invasive grasses have higher and broader population densities.” As a result long term “plant invasions increase soil nitrogen pools and total ecosystem nitrogen stocks” (Rout 2009) and contributes to invasive plant success and rapid colonization around the island. Given these ideas about nitrogen influxes and the spread of invasive plants my fellow interns and I are developing a short term project in order to understand the spread of invasive plants using applied conservation. Although our time is limited on Catalina Island, we look forward to establishing baseline studies for future continuation.

Works Cited:

Rout, Marnie. “An Invasive Plant Paradox.” Science 324. (2009). 734. Online.

Editor’s note: The ENST Catalina Island Internship at USC Dornsife is offered as part of a summer internship program offered to undergraduate students in the USC Dana and David Dornsife College of Letters, Arts and Sciences. This course takes place on location at the USC Wrigley Marine Science Center on Catalina Island. Students investigate important environmental issues such as ecological restoration, protected-area planning and assessment, and invasive species management. During the course of the internship, students will work closely with USC faculty and staff scientists from the Catalina Island Conservancy to support ongoing conservation and management programs being implemented on the island. Instructors for the course include David Ginsburg, Assistant Professor of Environmental Studies, Lisa Collins, Lecturer in Environmental Studies, and Tony Summers, Invasive Plant Program Supervisor from the Catalina Island Conservancy.