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Contributed Poster

Session: Conservation Ecology and Extinction

PS 22-39 - Effects of selective mowing of invasive grasses on pollinator networks in a California oak savanna environment

Tuesday, August 8, 2023
5:00 PM – 6:30 PM PDT
Location: ESA Exhibit Hall
Abstract: Invasive species are threatening ecosystems, causing native populations to be decimated. Native wildflowers are especially threatened due to invasive grasses outcompeting them, affecting populations of native pollinators that rely on these wildflowers. Mowing as an ecological restoration technique has been shown to greatly influence environments to restore and aid damaged habitats. It is known that plant-pollinator networks can be influenced by relative abundance of flowers and diversity of flowering plant species, but the effects of selective mowing on plant-pollinator interactions have not been thoroughly examined. To analyze the effects of selective mowing of invasive grasses this study compared pollinator community and network structure in paired mowed and unmowed plots in California. This study was conducted at Blue Oak Ranch Reserve in Santa Clara County. We had a total of 4 mowed and unmowed plots, each with a 50 m diameter. Vegetation sampling was conducted using a straight line transect through each plot, with quadrats placed every 5 meters. For each quadrat, we identified flowering species and measured their abundances and measured abiotic factors such as soil compaction and slope. Plant-pollinator interaction data was collected by capturing pollinator invertebrates that landed on flowers during 15-minute intervals for each flowering plant in the plot using aerial sweep netting. Passive sampling was also conducted by putting out pan trap stations made of blue, yellow, and white pans half filled with soapy water and placed in the center of each plot for 8 hours. Specimens were then pinned and identified to species level. We found significant differences in pollinator species diversity between the mowed plots of land and unmowed plots of land, and significant effects of mowing on some indices of network architecture including robustness to secondary species extinction. This study will provide critical data to land managers about the effects of common grassland restoration techniques on pollinator communities, without which restoration cannot be achieved.