Diversity of soil seed bank and above-ground community in Ivesia webberi A. Gray communities

Background/Question/Methods: Soil seed bank is vital to species distribution, colonization, survival, persistence, and maintenance of genetic diversity of plant species, particularly for rare species in which seed production is relatively low. In this study, we investigated the effect of soil seed bank on the regeneration of Ivesia webberi A. Gray, a federally-listed threatened forb, native to the western Great Basin Desert. We inquired if community diversity of plant communities in 10 selected Ivesia webberi population sites is correlated to their soil seed banks. We also investigated if site disturbance, elevation, distance to road, and site climatic variables have significant effect on the statistical relationship between the diversity of soil seed bank and above-ground communities in I. webberi population sites. We also tested the effect of geographical distance on species dissimilarities across sites. Soil seed bank was quantified using cold stratification germination method under controlled environment in the greenhouse.

Results/Conclusions: Four populations with U.S. Fish and Wildlife population designations 5, 6, 7 and 8 have the highest native species diversity and richness. Between the soil seed bank and aboveground community, species diversity and effective number of species were weakly, but positively correlated, species richness is negatively correlated, while species similarity and dissimilarity are positively and significantly correlated. Eighty-three species were sampled in aboveground communities, including 71 natives and 12 alien species; while 34 species were identified in soil seed bank, including 22 native plants. However, I. webberi was not observed in soil seed bank, validating field survey reports that seed regeneration is uncommon in this species. Mantel and partial mantel tests indicate that species diversity and community turnover are influenced by local ecological processes in both aboveground and soil seed bank communities. However, Euclidean distance seems to play some role in the floristic dissimilarity between aboveground and soil seed bank communities.