The purpose of this study was to assess the impact of the removal of ungulates on the soil seed bank of the endemic Santa Rosa Island manzanita (Arctostaphylos confertiflora). A. confertiflora was trampled and browsed by non-native ungulates between the years 1850 and 2011 which reduced its ability to produce seeds.This species is an obligate seeder, meaning that sprouting from seeds in the soil is its only method of reproduction. Due in part to the lack of its soil seed bank, this species was federally listed as endangered by the US Fish and Wildlife Service in 1997. In order to assess the trend in its seed bank density, researchers compared its density in 2004 to its density in 2018. There are three stands of of A. confertiflora on the island, and this study collected data on the seed banks in each location. The overall methodology for surveying the seed bank was by selecting sixteen random plants in each stand and collecting 12 soil samples under the canopy of each one, which were sieved to count the number of seeds. The number of seeds was extrapolated to determine the number of seeds per square meter (seeds/m2) of soil surface sampled. The data set examined for this poster focuses on only one of the three stands; data on the other two stands have yet to be examined. This pilot data set found a 213% increase in number of seeds/m2 in the stand from 2004 to 2018, although results were not statistically significant at the 95% confidence level (Mann-Whitney U=. A Mann-Whitney U test found that the 2018 seed bank at Telephone Road did not have a significantly higher number of seeds than the 2004 seed bank (U=88.5, p=0.13). These data can be used by agency scientists to evaluate status and plan further management for A. confertiflora conservation and recovery.


Biodiversity | Ecology and Evolutionary Biology | Life Sciences


Kathryn McEachern

Lab site

California State University, Channel Islands (CSUCI)

Funding Acknowledgement

The 2018 STEM Teacher and Researcher Program and this project have been made possible through support from Chevron (www.chevron.com), the National Marine Sanctuary Foundation (www.marinesanctuary.org), the National Science Foundation through the Robert Noyce Program under Grant #1836335 and 1340110, the California State University Office of the Chancellor, and California Polytechnic State University in partnership with California State University Channel Islands Research Station, United States Geological Survey, and the National Park Service. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funders. Thank you to Dulce Lopez, Yvette Lopez, Marisol Villareal, Patrick Costa, and Stephen Bednar for help with data collection.



URL: https://digitalcommons.calpoly.edu/star/535


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