Natural Resources/Environmental Management

54-12 - Effects of Non-Native Mosquitofish on a California Pond Ecosystem

Project Leader

Johnson/Preston

Affiliation

University of Colorado Ecology and Evolutionary Biology

Objective

Invasive species represent major drivers of ecosystem change, especially in freshwaters. However, it is challenging to understand the ecosystem-level consequences of invasions because field data are often confounded by other types of environmental change and because large-scale experiments are challenging to perform. Here, we propose examining the impacts of a widespread aquatic invasive species, the western mosquitofish (Gambusia affinis) on a native California pond community. We will introduce mosquitofish to one side of a pond that is artificially divided by a barrier, and will use a Before-After-Control-Impact (BACI) design that employs quantitative survey approaches to document mosquitofish effects on native zooplankton, invertebrates and amphibians. By quantifying the biomass of emergent insects and amphibians from both sides of the pond, we will also address how mosquitofish alter the energetic linkages between aquatic and terrestrial habitats. We hypothesize that mosquitofish will decrease pond diversity and may eliminate certain preferred prey species. The abundances of native species that are not susceptible to predation will potentially increase, due to the indirect release from competition and/or predation by other natives. We also predict that mosquitofish will be highly productive, but will limit the net export of biomass from the pond into the adjacent terrestrial habitat. Importantly, because the study pond dries every year, the fish will not be able to survive more than one season. Our results have implications for understanding how mosquitofish restructure food webs, while also having direct relevance to managing pond ecosystems in California, which support a diversity of threatened species.

77-97 - Influence of plant species on nutrient dynamics

Project Leader

Firestone/Eviner

Affiliation

UC Berkeley Dept. of ESPM

Objective

Plant species can differ in their effects on almost every aspect of ecosystem structure and function. For the past 9 years, we have been studying how eight of the dominant plant species at Hopland differ in their impacts on multiple aspects of ecosystem structure and function, including: soil aggregation, soil carbon and nutrient capital, nutrient recycling, soil moisture, the soil microbial community, and the activity of voles and gophers. Our research has shown that plant species effects on these different ecosystem properties and processes changes seasonally, and changes with time since plants are established at a site. Furthermore, when plant species are replaced by other plants, their impacts on soil properties and processes persist for at least 5 years. These ""legacy effects'"" do not mirror the ecosystem effects of the plants when they were present at the site. All of these patterns of plant species effects could be predicted using multiple plant traits, including litter chemistry, root:shoot biomass, plant labile C inputs, and plant species effects on soil temperature and moisture. Shifts in the relative importance of these traits was primarily responsible for changes in plant species effects on nutrient cycling with season, with time since establishment, and with time after the species have been replaced by other species. In addition, in collaboration with Chuck Vaughn, we found that nutrient recycling is not only mediated by decomposition of litter senesced at the end of the growing season, but that self-thinning of seedlings can contribute at least as much to seasonal N turnover and plant available N.

78-93 - Monitoring wetland habitats

Project Leader

Giusti

Affiliation

UC Cooperative Extension Mendocino County

Objective

Riparian management is one of the most controversial issues facing landowners in California today. Though a great deal of information exists for coniferous situations in California relatively few, long-term monitoring studies exist for oak woodland riparian systems. The project is intended to demonstrate 1) the importance of riparian zones to non-fish vertebrates, and 2) the importance of managing specific riparian habitat elements for the benefit of terrestrial obligate species. Because birds are so readily visible and recognizable by most members of the public, they were selected as the taxa for monitoring to better convince landowners of the benefits of riparian vegetation management.

80-11 - The community ecology of viral pathogens: Causes and consequences of coinfection in hosts

Project Leader

Briggs/Mitchell

Affiliation

UC Santa Barbara Dept of Life Sciences

Objective

Many individual host organisms are simultaneously coinfected by multiple pathogen species. The diversity (number and identity) of coinfecting pathogens can modulate both pathogen transmission among hosts and pathogen impacts on hosts. Nonetheless, little is known about the processes that govern pathogen diversity. Our research team will use field experiments to investigate the causes and consequences of pathogen diversity. We will study a model system of five viral pathogens of grasses (the cereal and barley yellow dwarf viruses). At the plot level in three related experiments, we will experimentally manipulate richness of the virus species pool, aphid abundance and species composition, seasonal water availability, plant community species composition, and spatial mixing of annual and perennial host species. This approach will allow us to compare the roles of the pathogen species themselves, the insect vectors that transmit them, their plant hosts, climate conditions, and spatial processes in controlling the dynamics of systems that include multiple pathogen species. Further, we will use greenhouse experiments (at Cornell, Minnesota, and North Carolina) to elucidate the mechanisms by which pathogens interact. Finally, we will use mathematical models to evaluate the longer-term dynamical consequences of viral coinfections.

92-06 - Cultural markings on the landscape: the PCN pecked curvilinear nucleated tradition in the coastal ranges (Hopland) of California

Project Leader

Gillette

Affiliation

UC Berkeley Anthropology Dept.

Objective

The PCN (Pecked Curvilinear Nucleated) rock art tradition is believed to represent one of the earliest rock art 'styles' in California and is identified as a pecked oval or circle that produces a raised or nucleated center, nearly always occurring on a greenstone boulder with a high talc content. The geographical distribution of the nearly 100 known PCN sites spans several hundred miles of the Coastal Ranges. Three of these sites are located within the boundaries of Hopland Field Station. This project will contextualize this early rock art tradition, by exploring the relationship of the boulders to regional settlement patterns, associated archaeological materials, and how the phenomenon may "interact" with nearby landscape features. This is dissertation study that will include a thorough archive research of pertinent literature, including all regional site reports on file at the Northwest Information Center at Rohnert Park; California, a review of previous archaeological work performed at Hopland Field Station; a systematic pedestrian surface survey and shovel testing, where indicated and with permission; 3-D Laser scanning of the PCN boulders; and, if warrented and permitted, excavation of test pits adjoining the identified boulders. The sub-surface portion of the study will strive to identify artifactual material that may be linked with the PCN tradition or provide insight into understanding the prehistoric cultural practices and peoples responsible for leaving the images on the rocks, and to seek landscape features that might have played a role in selection of the site locations by prehistoric peoples.