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Date of Award


Document Type

Thesis - Pacific Access Restricted

Degree Name

Master of Science (M.S.)


Biological Sciences

First Advisor

Charles G. Anderson

First Committee Member

Joan Lin-Cereghino

Second Committee Member

Stacy Luthy


The Calaveras River is a unique riparian habitat in San Joaquin County, influenced by both tidal water from the San Francisco Bay and impounded rainwater from the New Hogan Dam. The Calaveras River is one of the few river systems in California that does not benefit from snowpack melt. This dynamic system has changed dramatically in both its species composition and hydrodynamic regime due to years of human influences. What was once a thriving population of native plant species has become an environment dominated almost completely by aggressive exotic invasive species. The goal of this project was to remove the nonnative plant habitat by the most cost effective and least labor intensive means. The study area was along a section of river that bisects the University of Pacific campus in Stockton, California. From years of invasive species presence a deep seedbank has developed within the soil which acts to reduce the effectiveness of native plant reintroductions. A technique known as "solarization" was used to eliminate the seedbank and to facilitate the survival of native plants. Tarps were used to eradicate existing plants followed by disturbance of the soil and watering to induce germination of subsoil weed seeds. As the new plant seedlings emerge, tarps are reapplied to eliminate that generation of seedbank plants. After four time series of tarping and watering, a significant difference was found between control plots and treatments utilizing the solarization technique. Treatment 2, which consisted of tarping without weight, was determined to best target the seedbank after four repetitions and resulted in reducing invasive species in the seed bank.



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