National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Bighorn Canyon National Recreation Area Natural Resource Condition Assessment Natural Resource Report NPS/BICA/NRR—2012/554 ON THE COVER Reflections on Bighorn Lake Photograph by: Henthorne, NPS Bighorn Canyon National Recreation Area Natural Resource Condition Assessment Natural Resource Report NPS/BICA/NRR—2012/554 M. R. Komp1 A. J. Nadeau1 E. Iverson1 L. Danzinger1 S. Amberg1 K. Kilkus1 J. Sopcak1 C. Jean2 M. Myers3 B. Drazkowski1 1GeoSpatial Services Saint Mary’s University of Minnesota 700 Terrace Heights, Box #7 Winona, Minnesota 55987 2National Park Service - Greater Yellowstone Network 2327 University Way, Suite 2 Bozeman, MT 59715 3National Park Service - Intermountain Region Civil and Environmental Engineering Department Colorado State University July 2012 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 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 Report Series is used to disseminate high-priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain NPS policy considerations or address sensitive issues of management applicability. 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 from the Greater Yellowstone Inventory and Monitoring Network and the Natural Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). Please cite this publication as: Komp, M. R., A. J. Nadeau, E. Iverson, L. Danzinger, S. Amberg, K. Kilkus, J. Sopcak, C. Jean, M. Myers, and B. Drazkowski. 2012. Bighorn Canyon National Recreation Area: Natural Resource Condition Assessment. Natural Resource Report NPS/BICA/NRR—2012/554. National Park Service, Fort Collins, Colorado. NPS 617/115821, July 2012 ii Contents Page Figures............................................................................................................................................. v Tables ............................................................................................................................................ vii Executive Summary ..................................................................................................................... xix Acknowledgments....................................................................................................................... xvii Acronyms and Abbreviations ...................................................................................................... xix Chapter 1 NRCA Background Information .................................................................................... 1 Chapter 2 Introduction and Resource Setting ................................................................................. 5 2.1 Park History and Enabling Legislation .............................................................................. 5 2.2 Park Significance ............................................................................................................... 5 2.3 Geographic Setting, Climate and Biota ............................................................................. 6 2.4 Resource Stewardship ...................................................................................................... 11 2.5 Status of Supporting Science ........................................................................................... 15 Chapter 3 Study Scoping and Design ........................................................................................... 27 3.1 Preliminary scoping ......................................................................................................... 27 3.2 Study Design .................................................................................................................... 28 3.3 Literature Cited ................................................................................................................ 36 Chapter 4 Natural Resource Conditions ....................................................................................... 37 4.1 Cottonwood-dominated Woodlands ................................................................................ 38 4.2 Cushion Plant Community ............................................................................................... 45 4.3 Sagebrush Steppe Community ......................................................................................... 53 4.4 Juniper, Pine, Mountain Mahogany Community ............................................................. 61 4.5 Bighorn Sheep ................................................................................................................. 74 iii Contents (continued) Page 4.6 Wild Horses ..................................................................................................................... 90 4.7 Bats ................................................................................................................................ 105 4.8 Game Birds .................................................................................................................... 112 4.9 Land Birds ..................................................................................................................... 129 4.10 Peregrine Falcon .......................................................................................................... 146 4.11 Bighorn Lake Species .................................................................................................. 157 4.12 Tailwater Trout Fishery ............................................................................................... 163 4.13 Water Quality ............................................................................................................... 173 4.14 Viewscape .................................................................................................................... 195 4.15 Seeps and Springs ........................................................................................................ 211 4.16 Erosion ......................................................................................................................... 222 4.17 Visitor Experience as Affected by Surface Water Hydrology ..................................... 233 Chapter 5 Discussion .................................................................................................................. 243 5.1 Component Data Gaps ................................................................................................... 243 5.2 Component Condition Designations .............................................................................. 244 5.3 Park-wide Condition Observations ................................................................................ 246 Appendices .................................................................................................................................. 249 iv Figures Page Figure 1. Symbols used for individual component assessments with condition or concern designations ..................................................................................................................... 33 Figure 2. Non-native plant composition of areas mapped as gross areas ..................................... 40 Figure 3. Average percent bare ground cover from Tercek (2012) for all sample frames in BICA ............................................................................................................................. 56 Figure 4. Average percent cryptobiotic/lichen/fungi cover from Tercek (2012) for all sample frames in BICA ................................................................................................................. 57 Figure 5. Percentage of plots occupied by cheatgrass and halogeton in the Tercek (2012) study .................................................................................................................................. 64 Figure 6. BICA bighorn sheep estimated population size, 1985-2003 ......................................... 77 Figure 7. 1992-1994 monthly precipitation totals compared to mean precipitation ..................... 83 Figure 8. Pryor Mountain wild horse population, 1971-2009 .....................................................