Serpentine Vegetation Management Project 2005 REPORT Stuart B. Weiss, Ph.D. and David H. Wright, Ph.D. Creekside Center for Earth Observation 27 Bishop Lane, Menlo Park, CA 94025 tel: 650-854-9732, fax: 650-644-3355 e-mail: [email protected] http://www.creeksidescience.com FWS Grant Agreement No. 814205G240 Weiss and Wright 2005 Serpentine Vegetation Management Report Cover photo: David Wright trimming a 2-inch early trim, grazing exclusion plot on March 15, 2005. The PVC quadrat shows the size of the sample area; an additional 2 dm on all sides of the plot are trimmed to minimize edge effects. The wood blocks are temporarily placed to standardize the height of cut. The wooden stake at upper left marks and identifies the plot. The fence in the background excludes cattle grazing. CONTENTS: Page a. Abstract iii b. Introduction 1 c. Description of study area 3 d. Methods and materials 3 e. Results and Discussion 5 f. Summary and conclusions 14 g. Literature cited 15 h. Summary of expenditures 15 h. Data appendices CD included ii Weiss and Wright 2005 Serpentine Vegetation Management Report ABSTRACT We have begun a 3-year project to evaluate vegetation management methods and grazing impacts on serpentine habitat in Santa Clara County. In the first year of our project, funded by Habitat Restoration Program grant 814205G240, we established an experimental vegetation management trial, collecting initial vegetation data from that trial, conducted observations on serpentine vegetation characteristics across different grazing and other vegetation management regimes (fenceline and burn study), investigated herbivore damage to Dudleya setchellii, and recorded the spatial distribution and other observations on Streptanthus albidus peramoenus and S. a. albidus. Developing vegetation management information and applying it in adaptive land management are priority tasks for recovery of the bay checkerspot butterfly, Santa Clara Valley dudleya, Metcalf Canyon jewelflower, and other species. Vegetation management trial: Cattle exclusion fence and seven vegetation-management treatments have been successfully established and maintained. Initial percent cover data for all plant species present have been collected and archived. Visible differences among treatments are emerging. Plantago erecta densities were very low in spring 2005, but we expect future increases. This trial will continue for two additional years. Grazing and burn comparisons: We found that ungrazed areas supported little suitable habitat for Bay checkerspot butterflies, as they were dominated by annual grasses and provided little host plant and nectar resources. Annual grass cover was lower in the Winter-Spring than in the Summer–Fall regime, but both supported similar densities of Plantago and had adequate nectar sources to support dense Bay checkerspot populations. A 2004 late-spring wildfire on Tulare Hill allowed for higher Plantago cover and lower annual grass cover. The major difference between burned areas that had been grazed and those that had not was reduced annual grass cover in the grazed areas. Dudleya setchellii and Streptanthus albidus: Herbivory on dudleya appears strongly dependent on location, i.e. on local populations and activity of herbivores, including the timing of their activity. Animals that damage Santa Clara Valley dudleya appear to include cattle and rodents (ground squirrels, gophers) or rabbits. In some locations damage by cattle may be significant; in other areas it appears not to be. Some of our observations suggest a benefit to some dudleya populations from limited grazing, possibly through reduction of competition for light, space or other resources, or through reduced cover for small herbivores. The subspecies S. a. peramoenus, and probably the endangered subspecies albidus as well, appears to be somewhat flexible in the face of moderate damage simulating herbivory. On the other hand, naturally occurring severe damage was seen in the field. More work is planned quantifying response of the most- beautiful jewelflower to rather severe damage. We found its reproductive effort to be strongly related to plant size, setting the stage for such a response. Bombus melanopygus was documented to readily visit S. a. peramoenus. There is a transition zone between the two subspecies near the Field Sports Park, with mixed populations of pink (ssp. peramoenus), white (ssp. albidus), and intermediate flower colors across a 2 km transect. iii Weiss and Wright 2005 Serpentine Vegetation Management Report INTRODUCTION We have begun a project to evaluate vegetation management methods and grazing impacts on serpentine habitat in Santa Clara County – funded in the first year by the Habitat Restoration Program. Developing this information and applying it in adaptive land management are priority tasks for recovery of the bay checkerspot butterfly, Santa Clara Valley dudleya, Metcalf Canyon jewelflower, and other species. Work is in progress atop Coyote Ridge, in a conservation area in the Kirby recovery unit for bay checkerspot butterfly, and at other significant serpentine preserves in the county. We applied to the CVPCP/HRP and were approved for funding to continue this project for two additional years (2006-2007). Serpentine grasslands in Santa Clara County support multiple listed and rare species, including the bay checkerspot butterfly (Euphydryas editha bayensis), Santa Clara Valley dudleya (Dudleya setchellii), Metcalf Canyon jewelflower (Streptanthus albidus albidus), and Opler’s longhorn moth (Adela oplerella). Table 1 provides a list of species of interest that may benefit from this project. Many are endemic to serpentine sites, and the federally listed species are endemic to Santa Clara County or nearly so. A critical need in order to recover species and restore habitat on serpentine soils in Santa Clara County is to build adaptive vegetation management strategies. This need is identified in the USFWS 1998 final Recovery Plan for Serpentine Soil Species of the San Francisco Bay Area as Priority 1 tasks, number 5.16 and 5.24 (p. IV-27 to 28, 33, 35), and the results of strategy development are needed for habitat management of preserved serpentine sites, Priority 1 task 3.1 (p. IV-16) (USFWS 1998). Serpentine soil habitats supporting endemic species in Santa Clara County consistently have been identified by the CVPCP and HRP as a high priority for attention and funding in recent years. Our ultimate objective is to provide land managers with information they need on serpentine vegetation response to management alternatives, so that they can more effectively implement their own vegetation management programs for conserving rare species. In the first year of our project we established an experimental vegetation management trial, collecting initial vegetation data from that trial, conducted observations on serpentine vegetation characteristics across different grazing and other vegetation management regimes (fenceline and burn study), investigated herbivore damage to Dudleya setchellii, and recorded the spatial distribution and other observations on Streptanthus albidus peramoenus and S. a. albidus. 1 Weiss and Wright 2005 Serpentine Vegetation Management Report Table 1. Special Status Species and Species of Interest in the Area of the Project Common Name Scientific Name Status1 Comments bay checkerspot Euphydryas editha FT largest core population, butterfly bayensis critical habitat Opler=s longhorn Adela oplerella FSC moth Santa Clara Valley Dudleya setchellii FE, CNPS rocky serpentine areas dudleya 1B Metcalf Canyon Streptanthus albidus FE, CNPS white flowers jewelflower albidus 1B Amost beautiful@ Streptanthus albidus FSC, pink-purple flowers jewelflower peramoenus CNPS 1B smooth lessingia Lessingia micradenia FSC, var. glabrata CNPS 1B serpentine linanthus Linanthus ambiguus CNPS 4 dwarf plantain Plantago erecta food plant of bay checkerspot purple owl=s clover Castilleja densiflora food plant of bay checkerspot exserted paintbrush Castilleja exserta food plant of bay checkerspot California cream cups Platystemon food plant of Opler’s californicus longhorn moth tidy-tips Layia platyglossa nectar plant, bay checkerspot California goldfields Lasthenia californica nectar plant, bay checkerspot desert-parsley Lomatium spp. nectar plant, bay checkerspot scytheleaf onion Allium falcifolium nectar plant, bay checkerspot sea muilla Muilla maritima nectar plant, bay checkerspot false babystars Linanthus androsaceus nectar plant, bay checkerspot intermediate Amsinckia intermedia nectar plant, bay checkerspot fiddleneck 1FE=federally endangered, FT=federally threatened, FSC=federal species of concern. CNPS codes refer to California Native Plant Society lists. 2 Weiss and Wright 2005 Serpentine Vegetation Management Report DESCRIPTION OF STUDY AREA All work was conducted in serpentine grassland habitats in Santa Clara County, California, USA. The vegetation is essentially treeless, dominated by grasses and forbs, with unusually high levels of native and endemic species relative to non-serpentine California grasslands. The soils of our study areas typically are mapped as Montara series, a distinctive serpentine series in Santa Clara County. A general description of this type of habitat can be found in the introduction of the Recovery Plan for Serpentine Soil Species of the San Francisco Bay Area (USFWS 1998). We established our vegetation management trial on Coyote Ridge, in the Kirby Conservation Area north of the Kirby Canyon Landfill. The location of the