Use of carbon addition in upland prairie restoration at Fern Ridge Natural Area
Fern Ridge Research Natural Area (RNA) is a cluster of remnant prairie sites within the southern Willamette Valley, managed by the Bureau of Land Management Eugene District. The Fern Ridge master plan
Fern Ridge Research Natural Area (RNA) is a cluster of remnant prairie sites within the southern Willamette Valley, managed by the Bureau of Land Management Eugene District. The Fern Ridge master plan provides these sites with wildlife habitat or environmentally sensitive land use designations. The current rare species management plan and Biological Opinion place primary emphasis on activities to benefit listed species; all sites except one are designated critical habitat for Fender’s blue butterfly, L. oreganus, or both.
One potential tool for decreasing invasion by exotic species is carbon addition. Carbon addition limits the amount of soil nutrients available for plant growth (particularly nitrogen and phosphorus) by stimulating microbial activity. Several studies have indicated that native species are more capable of tolerating low nutrient conditions than exotic species. In this experiment we tested if carbon addition, in the form of sucrose, would benefit native plant diversity in upland prairies at Fern Ridge Natural Area. Plots were established at the Big Spires and West Shore sites in spring of 2012. Treatments occurred in spring 2012, fall 2012, and in spring 2013.
We found that across all sites carbon addition tended to decrease plant cover. However our results were very site-specific and are dependent on community composition prior to carbon addition.
- At West Shore, which initially had higher native forb cover than Big Spires, carbon addition tended to have a slightly greater effect on native plants than exotic plants. Fewer carbon treatment are recommended to decrease exotic plant cover, while limiting the negative impact to native species.
- At Big Spires, however, carbon addition tended to increase cover of native species while simultaneously decreasing exotic plant cover. Therefore, if the site is primarily exotic dominated, multiple carbon additions could be ideal as they were found to promote native species.
- Carbon addition tended to increase bare ground at both sites, suggesting that targeting carbon treatments with seed addition might help promote native species abundance.
Future studies would enable us to tease apart how affects might differ depending on the initial plant community and present recommendations for land managers in the Willamette Valley.