The impact of small vertebrate consumers on community assembly in degraded California sage scrub

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Taylor Edwards, Biological Sciences, California State Polytechnic University, Pomona and Erin Questad, Biological Sciences, California State Polytechnic University, Pomona, Pomona, CA

Background/Question/Methods
Native consumers have been found to influence plant recruitment and community assembly, depending on what species they prefer. In California sage scrub, little is known about the preferences of small vertebrate consumers, although their feeding behavior may affect interspecific competition between native and invasive plant species. Moreover, there is an unexplored opportunity to investigate which plant functional traits are preferred by small herbivores in the sage scrub community. We established caged and uncaged native restoration plots in degraded sage scrub in order to investigate the effects of consumers on community assembly. Thirteen native species were hand-seeded into research plots dominated by invasive grasses and forbs. Three community types were created using different seed treatments (dominated by a preferred species (Stipa pulchra), dominated by a less preferred species (Salvia mellifera), and control with species included in equal abundance). Plant recruitment and growth were monitored in experimental communities while motion activated trail cameras recorded consumer activity.
Results/Conclusions
Preliminary results showed that both native and invasive species grew better in caged conditions compared to uncaged. Consumers appeared to prefer native over invasive species. For example, the recruitment of two nitrogen-fixing native annuals with the largest seeds (Lupinus hirsutissimus and Lupinus bicolor) was limited to caged plots only. Camera evidence revealed a strong presence of granivorous birds after seeding. Research plots were most frequently visited by Melozone crissalis (California towhee), Zonotrichia leucophrys (white-crowned sparrow), and Sylvilagus audubonii (desert cottontail) in the weeks following seed addition. Continued data collection through the spring season will yield results on overall community and functional composition. So far, results suggest a notable influence of small granivores and herbivores on sage scrub community assembly, which may have implications for the success of native restoration.