Influence of Scale on the Management of Wildlife in California Oak Woodlands

Distributions, abundances, and patterns of resource use of amphibians, reptiles, birds, and small mammals varied spatially and temporally in California oak woodlands. Spatial variations occurred within stands, between stands of a similar type (e.g., canyon live oak [Quercus chrysolepis], blue oak [Q. douglasii], or valley oak [Q. lobata]), between stand types, and between geographic areas. Temporal variations occurred between seasons and years. Management of wildlife in oak woodlands should be based on research that details seasonal and temporal variations in habitat and resource use. Species that exhibit pronounced geographic variations in habitat use will require different management strategies, depending on location. Providing favorable conditions for breeding will not ensure that requirements for species occurring during nonbreeding periods will be met as well. California oak woodlands extend from the northern to the southern boundaries of the state and encompass over 2.5 million hectares. Within this area exists a number of vegetation types distinguished by differences in the composition and structure of the woody vegetation (Allen 1990). This vegetative diversity provides a wide spectrum of conditions suitable for occupancy by many species of wildlife (Block and Morrison 1990, Block and others 1990). Actual occupancy of suitable habitat is further influenced by historic distributional patterns and modified by various biotic (e.g., food abundance and availability, density of the species, competition, predation) and abiotic (e.g., weather, fire, anthropogenic) processes. Occupancy and specific resource-use patterns of wildlife are not static through time and space (Block 1989, Block and others 1988). With birds, for example, some species occur in a location throughout the year, whereas other species may be present only during breeding, winter, or migration. Resourceuse patterns of many amphibians, reptiles, birds, and mammals shift within and between seasons (Block and Morrison 1990, Block and others 1988). These shifts may be responses to changing needs during different phases of species' life histories or responses to shifts in the quantity and quality of the resource base. Presented at the Symposium on Oak Woodlands and Hardwood Rangeland Management, October 31-November 2 1990, Davis, California. Research Wildlife Biologist, Rocky Mountain Forest and Range Experiment Station, Forest Service, U. S. Department of Agriculture, Tempe, Ariz.; and Associate Professor, Department of Forestry and Resource Management, University of California, Berkeley. Previous address of WMB: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture, Fresno, CA. Knowledge of spatial and temporal variations in habitat use is needed to elucidate variations in populations, habitat associations, and community structure and to provide a basis for predicting effects of environmental perturbations on individual species and entire assemblages of species. This paper examines spatial and temporal relationships of wildlife in oak woodlands. We draw upon three years of field data collected on population numbers and macrohabitat associations of amphibians, reptiles, birds, and small mammals from four study areas, three primary and one ancillary, representing a diversity of oak-woodland ecosystems. Our objectives are to categorize species according to general macrohabitat associations and to determine the spatial patterns in species distributions.