California State University, Northridge The Use of Terrestrial Arthropods to Evaluate Coastal Sage Scrub Restoration Projects in the Santa Monica Mountains National Recreation Area A thesis submitted in partial fulfillment of the requirements For the degree of Master of Science in Biology By Wendy Dunbarr May, 2016 Copyright by Wendy Dunbarr 2016 ii The thesis of Wendy Dunbarr is approved: _____________________________________________ __________________ Dr. Tim Karels Date _____________________________________________ __________________ Dr. James. N. Hogue Date _____________________________________________ __________________ Dr. Irina Irvine Date _____________________________________________ __________________ Dr. Paula Schiffman, Chair Date California State University, Northridge iii Acknowledgements I want to extend tremendous thanks to Dr. James N. Hogue for the countless hours of support you provided in arthropod identification, brainstorming, canonical correspondence analysis interpretation, and moral support. You are a true mentor and a real mensch. iv Dedications To my husband, Jon, for all of your support and patience. You were a wonderful field assistant, and a much-appreciated bug picker. You talked me down when I was on high anxiety, and you talked me up when I was at my low points. Your encouragement and sound-boarding made all the difference. Thank you for all you did to make this degree happen. To the Wendy of 2009 ˗ you really did this. As Richard Bach wrote, “What the caterpillar calls the end, the Master calls a butterfly.” Even though it looked like the end, you pressed on and things have turned out beautifully. You figured out what you wanted and took all the leaps of faith and baby steps that were required to get here. Congratulations. v Table of Contents Copyright Page ii Signature Page iii Acknowledgement iv Dedication v List of Tables vii List of Figures viii Abstract ix Section 1: Introduction 1 Section 2: Methods 7 Study Sites 7 Vegetation Sampling 9 Arthropod Sampling and Identification 10 Data Analysis 11 Section 3: Results 14 Vegetation 14 Arthropods 15 Section 4: Discussion 19 Vegetation 19 Arthropods 21 Conclusions 26 Literature Cited 46 Appendix A: Terrestrial arthropod list 54 vi List of Tables Table 1. Vegetation cover data for each plot in three types of sites 33 at Cheeseboro Canyon. Table 2. Vegetation cover data for each plot in three types of sites 34 at Zuma Canyon. Table 3. Canonical coefficients for the five environmental variables 36 for both canyons. Table 4. Arthropod taxa with the 10 highest loadings for both canonical 38 correspondence analysis axes from Cheeseboro Canyon and the environmental variables they were associated with Table 5. Arthropod taxa with the 10 highest loadings for both canonical 40 correspondence analysis axes from Zuma Canyon and the environmental variables they were associated with vii List of Figures Figure 1. Location of sample locations within the Santa Monica 29 Mountains National Recreation Area Figure 2. Mean plant species richness across all plots for the three 30 site types in Cheeseboro Canyon. Figure 3. Mean plant species richness across all plots for the three 30 site types in Zuma Canyon. Figure 4. Percentages of mean vegetation cover, mean native species 31 cover, and mean Salvia leucophylla cover at three site types in Cheeseboro Canyon. Figure 5. Percentages of mean vegetation cover, mean native species 32 cover, and mean Salvia mellifera cover at three site types in Zuma Canyon. Figure 6. Species accumulation curve for Cheeseboro Canyon. 35 Figure 7. Species accumulation curve for Zuma Canyon. 35 Figure 8. Canonical correspondence analysis ordination diagram for 37 Cheeseboro Canyon. Figure 9. Canonical correspondence analysis ordination diagram for 39 Zuma Canyon. Figure 10. Mean terrestrial arthropod richness and abundance per plot 41 at three site types from Cheeseboro Canyon. Figure 11. Mean terrestrial arthropod richness and abundance per plot 42 at three site types from Zuma Canyon. Figure 12. Shannon index and Pielou’s evenness values for terrestrial 43 arthropods at three site types from Cheeseboro Canyon. Figure 13. Shannon index and Pielou’s evenness values for terrestrial 44 arthropods at three site types from Zuma Canyon. Figure14. Mean percentages of non-native terrestrial arthropod taxa 45 at Cheeseboro Canyon. Figure 15. Mean percentages of non-native terrestrial arthropod taxa 45 at Zuma Canyon. viii Abstract The Use of Terrestrial Arthropods to Evaluate Coastal Sage Scrub Restoration Projects in the Santa Monica Mountains National Recreation Area By Wendy Dunbarr Master of Science in Biology Non-native invasive plants threaten native plants in ecosystems through competition for resources, alteration to ecosystem functions and disturbance regimes, and changes to food webs and mutualistic relationships. Decades of intense disturbance and fragmentation of coastal sage scrub in Southern California have led to type conversion from mixed native shrub cover to non-native annual grassland in many places. Restoration efforts have been carried out by various government and private land managers in an effort to preserve existing coastal sage scrub and create additional habitat. Ecological restoration typically focuses on vegetation for both restoration activities and assessments of project outcomes. Additional measures of ecosystem function should be considered when evaluating the progress of restoration projects. Terrestrial arthropods occupy a wide breadth of niches and provide valuable ecosystem services (seed dispersal, ix decomposition, food sources for higher trophic levels). They are also sensitive to subtle, small-scale changes in the environment, which makes them more likely to be restored before larger animals. This study compared terrestrial arthropod assemblages along with vegetation characteristics among three types of sites (invaded, restored, native) to evaluate the success of two coastal sage scrub restoration projects within the Santa Monica Mountains National Recreation Area. Terrestrial arthropod assemblage compositions were successfully restored at both canyons. These results agreed with vegetation results at Cheeseboro Canyon, but contradicted vegetation results at Zuma Canyon. The results of this study indicate that restoration projects at both canyons were successful. The successful restoration of arthropod assemblage compositions despite spatial isolation and vegetative differences of the restored areas supported the Field of Dreams hypothesis that “if you build it, they will come”. The addition of terrestrial arthropod data to the standard practice of vegetation monitoring provided a more thorough evaluation of the status of these restoration projects, and should be used by land managers in the future. x Section 1: Introduction Invasive non-native plants threaten native plants and animals in ecosystems through competition for resources, alterations to ecosystem functions, changes to food webs and mutualistic relationships (Vitousek et al. 1997, Wilcove et al. 1998, Kourtev et al. 2002, Gurevitch and Padilla 2004, Pringle et al. 2009, Vil et al. 2011), and increases in frequency and intensity of disturbances (O’Leary 1989, Mack and D’Antonio 1998, Bossard and Randall 2007). Additionally, they can change native plant community assemblages, structure, and function (Jackson 1985, Rosenzweig 2001, Gurevitch and Padilla 2004, Stinson et al. 2006), and in some cases displace the native plant community entirely (Davis 2003, Brown and Gurevitch 2004, Gooden and French 2014). Twenty percent of California’s flora consists of non-native species (Randall et al. 1998), the majority of which originated in regions with Mediterranean-type climates (Randall et al. 1998, Bossard and Randall 2007). Among these species, annual grasses and forbs are the most likely to cause drastic changes in the communities they occupy (Gurevitch and Padilla 2004). Introduced around the time of European settlement, they dominate California grasslands (Jackson 1985, Stromberg et al. 2001) and are abundant in coastal sage scrub stands (Minnich and Dezzani 1998, Rundel 2007). Decades of intense disturbance and fragmentation of coastal sage scrub in Southern California have led to type conversion from mixed native shrub cover to non-native annual grassland (Rundel 2007) in many places. California coastal sage scrub is a plant community dominated by shrubs and subshrubs, including Salvia species, Artemisia californica, and Baccharis pilularis (Rundel 2007, Fleming et al. 2009). Many coastal sage scrub plants are drought 1 deciduous, losing all or most of their leaves in the dry, hot summer months, and growing new leaves when the rainy season begins, usually in late fall (Rundel 2007). This community occurs at elevations below 300 m along the coast and in the semi-arid interior of California, ranging from the San Francisco Bay area to El Rosario in Baja California (Westman 1981b, Rubinoff 2001, Rundel 2007). Küchler (1977) estimated that coastal sage scrub once covered 2.5% of the area of California. It currently occupies just 10-15% of its historic range (Westman 1981b). Recent evaluations of a coastal sage scrub survey performed in the 1930’s found only 40% of the original survey area still remaining relatively intact (Minnich and Dezzani 1998, Talluto and Suding 2008). This reduction in range is the result of urban and agricultural development, increased fire frequency, and invasion by non-native grasses and forbs (Minnich and Dezzani 1998, Talluto