MEASURE M CACTUS SCRUB RESTORATION PLAN FOR THE UNIVERSITY OF CALIFORNIA IRVINE ECOLOGICAL PRESERVE December 2, 2010 Prepared by Dr. Margot Griswold, NewFields LLC Dr. Kristine Preston, Nature Reserve of Orange County & Dr. Peter Bowler, University of California, Irvine SECTION 1. INTRODUCTION The Nature Reserve of Orange County (NROC) is responsible for coordinating and implementing monitoring and management activities in Orange County’s Central and Coastal Natural Community Conservation Plan/Habitat Conservation Plan (NCCP/HCP). The federally- threatened California gnatcatcher (Polioptila californica californica) and the state-sensitive coastal cactus wren (Campylorhnychus brunneicapillus) are two of three Target species conserved under the NCCP/HCP. The California gnatcatcher and coastal cactus wren are also included on the Measure M Freeway Projects Proposed Species List. The NCCP/HCP is a reserve system of ~37,000 acres, consisting of Coastal and Central Reserves with multiple land owners and managers. The 1993 Laguna Canyon Fire destroyed 75% of natural habitats in the 17,000 acre Coastal Reserve and the 2007 Windy Ridge and Santiago Canyon Fires destroyed 75% of natural habitats in the 20,000 acre Central Reserve. These fires, along with other factors such as drought and population isolation, have contributed to a more than 80% decline in the Cactus Wren population since 1992 (Mitrovich and Hamilton 2007, Leatherman 2009). California gnatcatchers have also been adversely affected by these large wildfires. However, shrubs in coastal sage scrub grow back more quickly than cactus, leading to more rapid recovery of gnatcatcher populations following fire. Cactus within the Coastal Reserve has recovered slowly after the 1993 Laguna Fire and wren populations are small and isolated. NROC’s top priorities are to recover cactus wren populations and to enhance California gnatcatcher populations within the reserve system. One measure to increase gnatcatcher and wren populations is to restore cactus scrub habitat, which consists of a mosaic of coastal sage scrub and cactus, and is occupied by both target species. University of California, Irvine Ecological Preserve The 62-acre University of California Irvine (UCI) Ecological Preserve is enrolled in Orange County’s Central and Coastal NCCP/HCP and is part of the Coastal Reserve System. It is managed by the UCI Office of Natural Resources for the School of Biological Science (http://www.bio.uci.edu/Reserves/UCI_Ecological_Preserve.html). UCI’s long range development plan designates this land for conservation and habitat management (UCI 2007). The Ecological Preserve supports Venturan-Diegan transitional sage scrub and grassland plant communities with 202 angiosperm species from 43 families (Bowler and Bramlet 2010). Despite a high number of invasive plant species (32.6%), the Preserve supports a diverse assemblage of invertebrate and vertebrate species. The UCI Ecological Preserve is a critical site for maintaining California gnatcatchers and coastal cactus wren populations. It provided an unburned refuge from the 1993 Laguna Canyon fire, supports stable populations of wrens and gnatcatchers, and serves as a source of dispersing individuals for other areas in the Coastal Reserve System. NROC is conducting a three year study to monitor cactus wren reproduction, dispersal and survival. One of the larger remaining clusters of cactus wrens in the Coastal Reserve is at the UCI Ecological Preserve. This population supported six territories in 2009 and 2010, with five pairs attempting to breed each year (Preston and Kamada 2009, unpublished data). Between two and four pairs were detected at the site from 2002 to 2005 (Harmsworth 2004, 2006). Over the last two years, NROC has color banded individual wrens and determined that the Preserve is a source of wrens dispersing to other areas and is important in augmenting and re-establishing wren populations in the Coastal Reserve. The UCI population is critical for recovery of cactus wrens in the NCCP/HCP. The UCI Ecological Preserve is also an important site for California Gnatcatchers and supports a stable population. In 2009 and 2010, there were at least seven pairs documented at the site (K. Preston, Personal Observation). Previous surveys found between five and ten pairs from 1993 to 2005 (Bontrager et al. 2000, Harmsworth 2004), with seven pairs documented in 2005 (Harmsworth Associates 2006). The UCI population is across SR-73 from the approximately 5 mile long California gnatcatcher corridor created by the Transportation Corridor Authority. This corridor extends from Upper Newport Bay to Coyote Canyon Landfill, linking habitat fragments along the toll road alignment to large expanses of habitat in Laguna Coast Wilderness Park and City of Irvine Open Space. The UCI Ecological Preserve supports 31 acres of cactus scrub mapped by NROC in 2006 (Figure 1). The remainder of the vegetation has not been mapped since 1992, so current acreages are estimates based upon an assessment of recent aerial photos. There appears to be approximately 10 acres of coastal sage scrub or disturbed coastal sage scrub with less than 20% cactus cover. Highly disturbed areas and non-native grassland comprise the remainder of the site and typically include some native plant species, such as perennial grasses, native forbs, and isolated shrubs and cactus. It is important to note that the fuel modification zones in the UCI Ecological Preserve are outside the NCCP Reserve boundaries and comprise a portion of the disturbed habitat at the 62 acre site. Disturbed areas at the Preserve were previously heavily grazed and as recently as 1980 supported little native shrub cover and a high abundance of invasive plant species. These invasive species included artichoke thistle (Cynara cardunculus), black mustard (Brassica nigra), and European annual grasses such as Avena and Bromus species. Since 1994, NROC has conducted an annual weed control program targeting artichoke thistle and it has been reduced to less than 2% cover over most of the UCI Ecological Preserve. While shrubs have re-established in many areas of the Preserve, other areas where artichoke thistle was eradicated have been invaded by exotic grasses and mustard. These areas of disturbed habitat are not passively recovering and will require active restoration to re-establish native cactus scrub 1.1 GOALS AND OBJECTIVES OF THE CACTUS SCRUB RESTORATION PROJECT NROC’s overall goal is to restore approximately 12.5 acres of disturbed and non-native grassland habitats to cactus scrub at the UCI Ecological Preserve in order to enhance breeding habitat for the coastal cactus wren and California gnatcatcher. NROC, the Transportation Corridor Authority (TCA), and UCI are collaborating on a project to link wren populations in the northern half of the Coastal Reserve and have received $282,000 in funding from the California State Department of Transportation’s Environmental Enhancement Mitigation Program (EEMP). The EEMP grant is being used to restore approximately 4.1 acres of cactus scrub at the UCI Ecological Preserve (Figure 2) and to plant cactus within the California gnatcatcher mitigation corridor adjacent to the Highway 73 Toll Road. NROC and UCI would use Measure M funding to restore the remaining disturbed and non-native grassland habitat at the UCI Ecological Preserve. Restoring high quality cactus scrub and enhancing native grasslands will result in increased nesting and foraging habitat for California gnatcatchers and cactus wrens. We estimate that two to three additional cactus wren territories and three to four California gnatcatcher territories could be supported at the site after full restoration. We plan to restore the site to an average of 75% cover of native plants, a standard that fulfills wildlife agency mitigation requirements for direct impacts to occupied habitat for these two species. The specific goals and objectives for the Measure M project are as follows: Goal: Increase breeding habitat for coastal cactus wrens and California gnatcatchers at the UCI Ecological Preserve by restoring and enhancing approximately 8.5 acres of cactus scrub in a mosaic of native grassland. Objective 1. Reduce average invasive plant cover to less than 10% in approximately 8.5 acres of currently disturbed and non-native grassland habitats. Objective 2. Plant up to 300 large salvaged prickly pear (Opuntia littoralis) cactus clumps and a minimum of 1,200 cactus pad in groups of 30 over 8.5 acres of currently disturbed and non- native grassland habitats. The exact number and location of large cactus clumps and cactus pads will depend on the results of final site mapping. Coastal cholla (Cylindropuntia prolifera) segments that have been shed from mature plants will be searched for onsite, and if available will be integrated into the cactus groupings. Cactus will be irrigated for the first two years after planting, with up to six irrigation events (three per year) timed in response to rainfall patterns. Objective 3. Collect native shrub, perennial grass and forb seeds from onsite and plant seeds around the cactus groupings. Mexican elderberry (Sambucus mexicana) individuals will be planted at least 15’ from cactus groupings and from each other, with approximately 15 plants per acre. Planted elderberries will be irrigated in conjunction with cactus irrigation events. Each restoration patch will vary in density and cover with an average target over the 8.5 acres of 40% cactus and shrubs with 35% cover of native grass and herbaceous species. UCI cactus wren habitat is somewhat open compared to other cactus scrub locations (T. Smith, personal observation). 1.2 PROJECT OVERVIEW Approximately 8.5 acres of highly disturbed and non-native grassland vegetation will be restored to cactus scrub consisting of prickly pear cactus and potentially coastal cholla in a mosaic of coastal sage scrub shrubs interspersed with patches of enhanced native grasses and forbs. The composition of native shrubs, grasses and forbs in the restoration and enhancement patches will reflect the local diversity and abundance of plant species onsite and will also depend on fine- scale soil and topographic characteristics.