Ramona Grasslands Open Space Preserve San Diego County, California
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Framework Management and Monitoring Plan Ramona Grasslands Open Space Preserve San Diego County, California Photo by Richard Herrmann\The Nature Conservancy of San Diego August 2004 Framework Management and Monitoring Plan for Ramona Grasslands Open Space Preserve San Diego County Prepared by Prepared for Scott A. Morrison, Ph.D. The Nature Conservancy San Diego, California August 2004 Revised October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve TABLE OF CONTENTS Page EXECUTIVE SUMMARY vi 1. INTRODUCTION 1 Ecological Significance 4 Conservation Goals and Targets 4 2. DESCRIPTION OF STUDY AREA 9 Geography and Climate 9 Soils 9 Fire History 14 Prehistoric and Historic Land Uses 14 Recent and Current Land Uses 16 3. ECOLOGICAL COMMUNITIES AND MANAGEMENT IMPLICATIONS 17 4. GRASSLANDS 25 Scientific Background 25 Grassland ecology 25 Stressors 27 Management approaches 28 Existing Conditions 30 Vegetation communities and stressors 30 Conservation targets 31 Restoration and Management 34 Desired conditions 34 Restoration and management actions 34 Monitoring targets 35 5. VERNAL POOLS AND SWALES 36 Scientific Background 36 Ecology of vernal wetlands 36 Stressors 37 Management approaches 37 Existing Conditions 38 Hydrology, vegetation community, and stressors 38 Conservation targets 40 Restoration and Management 41 Desired conditions 41 Restoration and management actions 41 Monitoring targets 41 ii October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve Page 6. ALKALI PLAYAS 42 Scientific Background 42 Alkali playa ecology 42 Stressors 42 Management approaches 42 Existing Conditions 43 Hydrology, vegetation community, and stressors 43 Conservation targets 43 Restoration and Management 43 Desired conditions 43 Restoration and management actions 44 Monitoring targets 44 7. STREAM AND RIPARIAN COMMUNITY 44 Scientific Background 44 Stream and riparian ecology 44 Stressors 46 Management approaches 46 Existing Conditions 47 Hydrology, vegetation community, and stressors 47 Conservation targets 49 Restoration and Management 49 Desired conditions 49 Restoration and management actions 50 Monitoring targets 50 8. PLANNING CONSIDERATIONS FOR PUBLIC ACCESS, TRAILS, AND MAINTENANCE 51 9. ADAPTIVE MANAGEMENT AND MONITORING 52 Managed Grazing 54 Management unit 1—riparian corridor 54 Management unit 2—loamy grasslands 56 Management unit 3—clayey grasslands 56 Eradication of Perennial Nonnative Plants 57 Controlled Burning 57 Habitat Restoration 58 Long-Term Monitoring Program 59 Data Management and Reporting 64 Management, Monitoring, and Maintenance Priorities for 2005-2006 64 10. REFERENCES 65 iii October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve Page APPENDIX A—CASE STUDIES IN GRASSLANDS MANAGEMENT FOR STEPHENS’ KANGAROO RAT A-1 APPENDIX B—TARGET SPECIES ACCOUNTS B-1 APPENDIX C—CULTURAL RESOURCES OVERVIEW OF THE RAMONA GRASSLANDS PRESERVE AND SANTA MARIA CREEK HABITAT RESTORATION PROJECT AREA C-1 LIST OF TABLES Page Table 1 Conservation targets, by community, for the Ramona Grasslands CAPP Area. 8 Table 2 Pertinent characteristics of soils in the core grasslands area. 12 Table 3 Conceptual model for managing conservation targets, Ramona Grasslands Preserve. 20 Table 4 Summary of proposed grazing regimes by management unit. 54 Table C-1 Recorded cultural and historic sites in Ramona Grasslands Preserve. C-8 LIST OF FIGURES Page Figure 1 Location of Ramona Grasslands CAPP Area within San Diego County. 2 Figure 2 Ramona Grasslands CAPP Area showing the Proposition 13 Santa Maria Creek Project Area and conservation status of properties in the Project Area. 3 Figure 3 MSCP planning designations for the vicinity of the Ramona Grasslands CAPP Area. 5 Figure 4 Core, buffer, and linkage areas of the Ramona Grasslands CAPP Area, with vegetation communities. 6 Figure 5 Critical Habitat designations in the Ramona Grasslands CAPP Area. 7 Figure 6 Location of Ramona Grasslands CAPP Area relative to watersheds of Santa Maria Creek and San Dieguito River. 10 Figure 7 Soil series within the Ramona Grasslands CAPP Area. 11 Figure 8 Ecological communities, core grasslands area. 18 Figure 9 Locations of selected native plant species and invasive nonnative species, core grasslands area. 32 iv October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve Page Figure 10 Soils likely to support Stephens’ kangaroo rats in the Ramona Grasslands CAPP Area. 33 Figure 11 Soils associated with vernal wetlands and alkali playas, core grasslands area. 39 Figure 12 General location of existing and proposed fencing and proposed management units for the core grasslands area. 55 Photo A-1 Ungrazed versus grazed grasslands at the boundary between Ramona Airport and former Cagney Ranch. A-3 Photo A-2 Ungrazed versus grazed versus recently burned/ungrazed at the Ramona Airport/former Cagney Ranch boundary. A-3 Figure A-1 Stephens’ kangaroo rat burrow density versus percent bare ground on 10 monitoring grids at the Ramona Airport, 2001 and 2002. A-4 Figure A-2 Stephens’ kangaroo rat burrow density versus forb/grass ratio on 10 monitoring grids at the Ramona Airport, 2001 and 2002. A-5 v October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve EXECUTIVE SUMMARY This framework management and monitoring plan provides guidance to maintain and enhance the conservation values of the Ramona Grasslands Open Space Preserve. The Preserve supports many unique biological resources, provides a suite of important environmental services for the region, and preserves a rich cultural and historic heritage. Ecological Significance The Ramona Grasslands host a unique assemblage of resources: • The southernmost population of the endangered Stephens’ kangaroo rat; • Unique vernal wetlands that support endangered San Diego fairy shrimp and several rare plant species; • Santa Maria Creek and associated habitats are important for neotropical migrant songbirds and the endangered arroyo toad; and • A diverse raptor community, including the largest population of wintering ferruginous hawks in San Diego. Oak savannah, riparian woodlands, alkali playas, native perennial grasslands, and rock outcrops contribute to the diversity and ecosystem functions within the grasslands. These resources are imminently threatened by the indirect impacts of urbanization and thus require science-informed monitoring and management to ensure their persistence. The Ramona Grasslands comprise a significant portion of the Santa Maria Creek subbasin of the San Dieguito River watershed. The Santa Maria Creek, which drains the urbanizing community of Ramona, flows westward through the grasslands, then through Bandy Canyon to its confluence with Santa Ysabel Creek. Below the confluence, the San Dieguito River flows through San Pasqual Valley into Lake Hodges, a City of San Diego drinking water reservoir. The creek corridor serves as both a hydrological and habitat linkage for numerous species. It also provides essential ecosystem processes, such as natural filtration of anthropogenic contaminants that may impair downstream water quality. The Ramona Grasslands Preserve functions as a core habitat area within a regional network of existing and anticipated conservation lands. The coastal sage scrub, chaparral, and oak woodlands of the surrounding landscape, together with the grasslands, riparian habitat, and vernal wetlands of the core area, constitute an exceptional concentration of regionally and globally significant resources. That significance is reflected by the near complete overlap of the Preserve area by federal Critical Habitat designations (San Diego fairy shrimp, arroyo toad, and California gnatcatcher). vi October 2004 Framework Management and Monitoring Plan, Ramona Grasslands Preserve Conservation Targets and Goals The overarching management goals for the Ramona Grasslands ecosystem are: • Maintain healthy biotic communities and constituent species populations. • Maintain functional landscape connections between the grasslands and adjacent undeveloped habitats. • Improve water quality in Santa Maria Creek and ephemeral aquatic and wetland habitats (i.e., vernal pools, swales, and alkali playas). The management approach focuses on conservation targets, i.e., communities, species or species assemblages, and processes of conservation concern. The grasslands are subdivided into the following ecological communities, using soil characteristics and hydrological features, which affect their ecological condition and dictate their responses to various management interventions: • Loamy grasslands/forblands and clayey grasslands/forblands • Vernal pools and swales • Alkali playas • Stream and riparian community Collectively, target-specific management prescriptions are intended to create a habitat mosaic that sustains the full complement of species native to this area. We apply The Nature Conservancy’s Ecological Integrity Assessment approach to guide the management and monitoring planning for each of these unique, but interdependent, communities. This approach involves assessing ecological integrity for various conservation targets (e.g., water quality or an endangered species) by identifying key ecological factors (conditions or processes) that sustain the targets. Identifying the key ecological factors requires understanding how various physical or ecological conditions and processes affect the conservation targets. The relationships between the ecological factors and the conservation targets are expressed