July 16, 2012
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.