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

July 16, 2012

Deer Valley Trail Invasive Plant Project Begins

Filed under: Uncategorized — Tags: , , — justinbo @ 10:45 pm

Last summer, the Wrigley interns played an integral role in establishing the Deer Valley Trail. For the past few weeks, other than continuing our work with the Conservancy’s invasive plant management and native plant restoration projects, we have been surveying this trail and looking for ways to extend our work with the Conservancy to the trail in the form of a research project. After some research into potential projects and a quick trip to the mainland for supplies, we were finally able to begin our project today, Monday, July 16th, 2012, with the installation of 12 plots along the trail.
Our project is going to be a long-term study into the effect of invasive plants (specifically fennel) on soil health. With the hypothesis that invasive plants increase nitrogen and carbon pools as well as the pH of the soil to an extent that is detrimental to native plant growth, we predict that if fennel is entirely removed from a plot, the nutrients in the soil will return to a more stable level. Furthermore, if native plants are introduced where invasive plants once were, we expect that soil health will increase to an even greater extent.
We chose two areas that are extremely disturbed with fennel to place our plots. We have three separate treatment methods that will be utilized. One treatment of the fennel will be full manual removal, one will be mowing the fennel just above the taproot, and one will be left alone as a control. In each of the two areas that we chose, we have six plots, two for each of the three treatment methods. The plots are scattered randomly, and no two replicates of the same treatment are next to each other at each site.
These 12 plots are concentrated in two areas at each end of the trail. The square plots are four feet across and are made of PVC pipes which we anchored into the ground with stakes after drilling holes into the PVC connectors.
In the next week, we will be using several methods with the direction of our Professor, David Ginsburg, to take soil samples within these plots. After we get a baseline, we will treat each of the plots and remove fennel when needed. Then, we will continue taking samples on a semi-weekly basis for the remainder of the summer, and continue with monthly or semi-monthly samples for the remainder of the school year. We plan on personally continuing the project into the school year, but we also plan to work in conjunction with Dr. Ginsburg and his students in his undergraduate course, ENST-320a.
So what exactly do we hope will come from this project? The Conservancy primarily uses herbicides for the treatment of large patches of fennel rather than manual removal, which is very labor intensive and causes a great deal of soil disturbance. Being in the watershed of the marine protected area down in Big Fisherman’s Cove, the fennel along the trail and in the surrounding area cannot be treated by herbicide, so large monocultures of fennel scatter the watershed. Some of the fennel is hard to reach, and on steep inclines, and full manual removal is often difficult or impossible. Part of our project hopes to see that if the fennel is mowed and allowed to grow back, how many times it will take before the fennel taproot runs out of enough nutrients and life to come back. If the mowed plots eventually are cleared of fennel, the prospect of applying this treatment method to the remainder of the watershed is available.
In a separate plot along the trail, we plan to not only take soil samples and remove invasive plants, but also actively restore the area with native plants. This project will be separate from the 12 plots that were set up earlier today, but the results will provide further insight into the soil health of the watershed, and how it can change with our remediation.

Drilling PVC

Photo credit: Dawnielle Tellez

Photo credit: Judy Fong

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.

July 12, 2011

Soil Collection Day 2: Two Harbors

Filed under: Uncategorized — Tags: , , , , — Sabrina Lawrence-Gomez @ 9:23 pm

Today was our second day of soil collection, and this time Lisa left us to our own devices. Our collection area today was the Two Harbors 2011 fire burn area and along Deer Valley Trail.

We started the day by gathering all of our sampling materials (spades, Ziploc bags, and transect tapes) and adding them into the “Bucket o’ Science” as Lisa lovingly calls it. We hopped in the van and drove back over to Two Harbors. I had scouted out some sampling areas the day before on my jog and proposed some ideas to the group. We decided to sample and transect an area that had burnt to a crisp, and an area in the same habitat that had not burned.

We set off up the hillside until we found a spot that was suitable, then set up the transect.


We attempted to identify some associated species of the area but it was extremely difficult. First of all, the only thing thriving in the area was invasive yellow mustard, which we had never formally identified. Secondly, all the plants that remained from the fire were grasses and were extremely difficult to identify. Instead of trying to guess each different grass, we decided to take a picture and take a sample to one of our experts and identify it later. It was a tough transect to complete and there was definitely a lot of discussion over each plant and each point.

Unidentified plants, a source of frustration


As we were laying down the tape, we had a visitor join us. It was Wilson, Two Harbors’ resident bison! We were a bit scared as he walked toward us, but it turned out he just wanted to scratch his face against a bush nearby us. There are always so many neat animal encounters in the field, you never know what is going to pop out next!

Wilson, the bison


Our next transect proved a bit easier, after a slightly treacherous hike to the sampling site. We wanted an area to contrast our burned site, so we looked for an unburned area. We climbed further up the ridge through a drainage, sort of following the road but mostly creating our own trail. Dan led the way and we found a great spot amidst some scrub oak. We completed the second transect, and took another soil sample. I really wanted another sample from the same aspect and elevation within the burn area (to have a direct comparison between burned and non-burned) so the group humored me and we hike across the hillside to the burned area to take a soil sample.

Two Harbors burn area constrasted with non burn area


After lunch, Dan, Miller, and Alex went up to our trail in Deer Valley to complete another transect and take a soil sample.

Transect through Deer Valley Trail


Once the data collection was completed, Lisa showed us how to sift the soil in the bag using a two micron sifter. Sifting the soil is going to take a while since there are a lot of sticky clay minerals in this island’s soil. Even though it will be alot of work, I am excited to see how all of our samples turn out in the lab. Overall, it’s been a great experience working in the field.

For more photos see Soil Collection and Transects Part II