National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Forest Structure in Muir Woods National Monument Survey of the Redwood Canyon Old-Growth Forest Natural Resource Technical Report NPS/SFAN/NRTR—2014/878 ON THE COVER The Main Trail through Redwood Canyon in Muir Woods National Monument. Photograph by: Jessica Weinberg, NPS Forest Structure in Muir Woods National Monument Survey of the Redwood Canyon Old-Growth Forest Natural Resource Technical Report NPS/SFAN/NRTR—2014/878 Robert Steers1,2, Heather Spaulding1,3, and Eric Wrubel1 1National Park Service San Francisco Bay Area Inventory and Monitoring Program Bldg 1063, Ft Cronkhite Sausalito, CA 94965 2University of California Department of Botany and Plant Sciences 2150 Batchelor Hall Riverside, CA 92521 3Univeristy of California Department of Land, Air, and Water Resources One Shields Avenue Davis, CA 95616 May 2014 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado, publishes a range of reports that address natural resource topics. These reports are of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Technical Report Series is used to disseminate results of scientific studies in the physical, biological, and social sciences for both the advancement of science and the achievement of the National Park Service mission. The series provides contributors with a forum for displaying comprehensive data that are often deleted from journals because of page limitations. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. This report received formal peer review by subject-matter experts who were not directly involved in the collection, analysis, or reporting of the data, and whose background and expertise put them on par technically and scientifically with the authors of the information. Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect views and policies of the National Park Service, U.S. Department of the Interior. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Government. This report is available in digital format from the San Francisco Area Network Inventory and Monitoring website (http://science.nature.nps.gov/im/units/sfan) and the Natural Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). To receive this report in a format optimized for screen readers, please email [email protected]. Please cite this publication as: Steers, R. J., H. L. Spaulding, and E. C. Wrubel. 2014. Forest structure in Muir Woods National Monument: Survey of the redwood canyon old-growth forest. Natural Resource Technical Report NPS/SFAN/NRTR—2014/878. National Park Service, Fort Collins, Colorado. NPS 112/124788, May 2014 ii Contents Page Figures.................................................................................................................................................... v Tables ..................................................................................................................................................... v Appendices ........................................................................................................................................... vii Abstract ................................................................................................................................................. ix Acknowledgments .................................................................................................................................. x Introduction ............................................................................................................................................ 1 Methods .................................................................................................................................................. 1 Study Area ...................................................................................................................................... 3 Vegetation Sampling ...................................................................................................................... 4 Statistical Analyses ......................................................................................................................... 5 Results .................................................................................................................................................... 7 Tree Composition ........................................................................................................................... 7 Tree Structure ................................................................................................................................. 7 Diameter at Breast Height and Basal Area ................................................................................ 7 Canopy Closure ......................................................................................................................... 8 Density ....................................................................................................................................... 8 Comparisons in Forest Structure between the Macroplot and Subplot ........................................ 12 Density per Hectare ................................................................................................................. 12 Basal Area ............................................................................................................................... 13 Discussion ............................................................................................................................................ 15 Tree Composition ......................................................................................................................... 15 Tree Structure ............................................................................................................................... 15 Comparisons between Macro- and Sub-plot Structural Measures ............................................... 16 Literature Cited .................................................................................................................................... 17 iii Figures Page Figure 1. Map of Muir Woods showing the location of sample sites used in this study. ..................... 3 Figure 2. Sampling plot showing all of the components used to measure forest structure and composition in this study. ............................................................................................................... 5 Figure 3. Graph of all trees measured and their diameter at breast height (DBH). ............................... 7 Figure 4. Basal area per hectare by sample site. ................................................................................... 8 Figure 5. Mean density of woody plant life forms per hectare based on data from 3 x3 m quadrats. ................................................................................................................................................. 9 Figure 6. Live tree density per hectare by species by sampling site. .................................................. 10 Figure 7. Dead tree density per hectare by species and by sampling site. .......................................... 10 Figure 8. Sapling density of live trees per hectare by sample site. ..................................................... 11 Figure 9. Sapling density of dead trees per hectare by sample site. .................................................... 11 Figure 10. Seedling density per hectare by species by sample site. .................................................... 11 Figure 11. Comparison of mean live tree density per hectare between all trees using a 17.95 m radius plot (macroplot) versus all trees using a 7.32 m radius plot (subplot) for various size classes. ............................................................................................................................. 13 Tables Page Table 1. Mean diameter at breast height (DBH) per tree by species, and mean basal area per hectare by species. ........................................................................................................................... 8 Table 2. Mean tree and sapling density per hectare by species. ............................................................ 9 Table 3. Comparison of mean live tree density per hectare for different size classes of trees between all stems found in the entire macroplot (17.95 m radius) versus all trees found just within the subplot (7.32 m radius). ..................................................................................... 12 v Appendices Page Appendix A. Geographic Coordinates of the Sample Sites ................................................................. 19 Appendix B. Density and Diameter at Breast Height Data of Trees and Saplings .............................. 21 Appendix C. Density Data Derived