The U.S. Geological Survey and the USDA Forest Service partnered to co-host a symposium on "Planning for Biodiversity: Bringing Research and Management Together," held February 29-March 2, 2000 at the Kellogg West Conference Center, California State Polytechnic University in Pomona, California. The goal of the 3-day conference was to identify the current status of our knowledge and gaps in our understanding of regional biodiversity and ecosystem processes, present and future threats to species and habitats, and effective monitoring strategies for southwestern and central coastal California resources. Through a program of 52 invited presentations, 18 contributed posters, and 10 focused discussion groups, the conference created an environment for formal and informal communication among the 300 attendees about the results of scientific studies and their application to resource conservation and management, as well as the information needs of managers responsible for determining and implementing management on the ground. Of the 45 technical papers presented at the conference, 14 are included in this volume. Authors were asked to synthesize the current state of knowledge regarding their topic and identify areas needing future research. Each paper was assigned to an editor for review and received one to three additional peer reviews. Expanded abstracts of nine posters also were reviewed by the editors and included. The topics addressed in the papers and poster abstracts reflect the breadth of the conference presentations and the issues facing the science and management communities, ranging from the threats of fire, air pollution, grazing, exotic species invasion, and habitat loss on native habitats and sensitive species of birds, mammals, reptiles and amphibians, to the role of mycorrhizal fungi as indicators of biological change.