Restoring Native Perennial Grasslands Invaded by Exotic Annual Grasses
Managing California's Heavily Invaded Perennial Grasslands
Annual grasses are nearly ubiquitous in California. Each winter when the hillsides and valleys of California green -- with enough rain that is -- much of this fleeting growth is actually due to nonnative annual grasses. These species arrived with European explorers, and have since invaded and displaced a number of California's native ecosystems, including its perennial grasslands that were historically dominated by bunchgrasses such as Stipa pulchra, or purple needle grass. Even the most pristine of native grasslands that remain are often heavily invaded by nonnative species, especially annual grasses and forbs from the Mediterranean, including Bromus and Avena species. While eradication of these invasive plant species is highly unlikely, I explore methods of grassland management aimed at restoring native species and decreasing the prevalence and impacts of nonnatives. I'm currently managing two experimental grassland restoration projects at the Santa Rosa Plateau Ecological Reserve and at The University of California's Stunt Ranch Reserve.
Santa Rosa Plateau Habitat Studies and Restoration Program: Integrating research and environmental education to restore native California grasslands
The Santa Rosa Plateau is home to some of the finest examples of native perennial grasslands in California, but these are still heavily invaded by nonnative species, which threatens the diversity, function and ecosystem services of this important habitat. California also faces statewide educational challenges that could influence training of the next generation of scientists, land managers and policy makers. The Habitat Studies and Restoration Program is a collaboration between the Santa Rosa Plateau Foundation, California Fish & Wildlife, Riverside County Regional Parks and researchers from the University of California, Riverside that seeks to address both of these issues through field-based education programs for multiple age groups. We involve local elementary, middle and high school classes from Murrieta School District in long-term field experiments exploring different techniques for perennial grassland restoration, including seed bank studies, a mulching experiment and a multi-year mowing experiment. Since 2012, each spring half of the study area is mowed before annual grasses have set seed. Our goal is to reduce seed inputs over the long term to promote natives, especially Stipa pulchra. Middle school students measure abundance and cover of native and nonnative species in plots multiple times throughout the year while receiving training in botany and plant ecology. After two years, mowing significantly reduced annual grass cover and led to a slight increase in native bunchgrass cover. Students also showed remarkable understanding of the importance of their work and the relevant complex ecological concepts. While long term monitoring is necessary to evaluate potential as a more widespread management strategy, this program shows promise on multiple levels. The integration of environmental education programs with research, management and restoration priorities could be a creative solution to both educational and environmental challenges in California.
Above- and Belowground Linkages in Native Grassland Restoration Following Severe Soil Disturbance
Land clearing is a common occurrence in Southern California. Cleared hillsides need to be revegetated quickly to preserve topsoil and avoid mud slides in the rainy season. The plants chosen for revegetation and the soil microorganisms present in soils are hugely important in determining the success of plant restoration projects. At Stunt Ranch in the Santa Monica Mountains, a hill side was recently cleared. I am collaborating with fellow UCLA researchers to restore this site with native California grassland plants including Stipa pulchra (purple needle grass), the official grass of the State of California. Prior to land clearing, this site was dominated by invasive Eurasian grasses. These grasses modify soil environments and microbial communities to the detriment of native species. We are currently reintroducing native annual and perennial plant species to the site and will be monitoring recovery of both the aboveground plant community and belowground soil microbial communities using eDNA.