PPoorrttllaanndd SSttaattee UUnniivveerrssiittyy PPDDXXSScchhoollaarr Dissertations and Theses Dissertations and Theses Fall 12-14-2012 SSttrreeaamm--AAssssoocciiaatteedd AAmmpphhiibbiiaann HHaabbiittaatt AAsssseessssmmeenntt iinn tthhee PPoorrttllaanndd--VVaannccoouuvveerr MMeettrrooppoolliittaann RReeggiioonn Andrew Evans Dietrich Portland State University Follow this and additional works at: https://pdxscholar.library.pdx.edu/open_access_etds Part of the Environmental Sciences Commons, Fresh Water Studies Commons, and the Terrestrial and Aquatic Ecology Commons Let us know how access to this document benefits you. RReeccoommmmeennddeedd CCiittaattiioonn Dietrich, Andrew Evans, "Stream-Associated Amphibian Habitat Assessment in the Portland-Vancouver Metropolitan Region" (2012). Dissertations and Theses. Paper 604. https://doi.org/10.15760/etd.604 This Thesis is brought to you for free and open access. It has been accepted for inclusion in Dissertations and Theses by an authorized administrator of PDXScholar. Please contact us if we can make this document more accessible: [email protected]. Stream-Associated Amphibian Habitat Assessment in the Portland- Vancouver Metropolitan Region by Andrew Evans Dietrich A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Science and Management Thesis Committee: J. Alan Yeakley, Chair Catherine deRivera Martin Lafrenz Portland State University 2012 ii © 2012 Andrew Evans Dietrich i ABSTRACT This study assessed the influence of landscape development on stream- associated amphibians in forested riparian areas within the Portland-Vancouver metropolitan region. Human alteration of landscapes may dramatically affect the ecology of neighboring aquatic systems. It was hypothesized that lotic amphibians would be negatively associated with greater amounts of landscape development and positively associated with forested area within the surrounding watershed. Thirty- seven 1st-3rd order streams were sampled between June 21st and September 21st in 2011. Streams potentially providing adequate habitat for stream-obligate amphibians were randomly selected. Amphibians were surveyed along 30-meter stream transects using an active-cover search (ACS). Environmental variables associated with development in surrounding landscapes were measured in situ. GIS delineation was conducted to define landscape-scale variables at stratified distances from riparian networks up-stream of each site via the utilization of the 2006 NLCD dataset and a finer-scale, regional dataset compiled by the Institute for Natural Resources (INR). Amphibians were detected at seventeen of the thirty-seven sampled streams. The most commonly detected species were Dicamptadon tenebrosus, Plethadon vehiculum and Plethadon dunni. Streams where amphibians were observed had lower average water temperature and conductivity, coarser stream substrate, and were located on public property more often than streams where no amphibians were detected. Landscape variables within 100 and 200 meters of the upstream stream network influenced amphibians most significantly. ii Occupancy of a site by facultative species was best explained by the proportion of mixed forest in the surrounding watershed (R2=0.34, p<0.001). Occupancy of a stream by obligate species was best predicted by measurements of water quality and in-stream cover (Water Temperature: R2=0.28, p<0.001; Water Conductivity: R2=0.25, p<0.001; Cover: R2=0.32, p<0.001). Occupancy of stream refugia by all observed amphibians was positively influenced by higher percentages of forest cover and by lower percentages of urban development and herbaceous vegetation in the surrounding watershed. Results of this study indicate that urban amphibian refugia must contain adequate riparian forest area, coarse stream substrate and clean, cool water to sustain stream-amphibian communities. This study demonstrates that protection of remnant forested headwater stream networks is essential to the conservation of lotic amphibians in urbanized regions. iii Dedication I dedicate this thesis to Sara, Onyx, my family and friends and everyone else who helped keep me sane through my graduate school experience. iv Acknowledgments I would like to thank my advisor, Alan Yeakley, for his support, guidance and wisdom throughout my time at Portland State. It has been a pleasure to be your advisee. I would like to thank my other committee members, Cat deRivera and Martin Lafrenz, for their helpful feedback, flexibility and support. Thank you also to Yangdong Pan for your invaluable critique during my thesis proposal process. I would also like to thank the rest of the faculty and staff in the Environmental Science and Management Department for providing interesting courses, endless help and a sense of community. In particular, a big thank you to Teri and Sherie for always being available to solve any problem. In addition, I could not have completed this thesis without the invaluable aid of Christa von Behren and our field technicians (Ben Burton, Jose Herrera, Stephanie Zhao, Megan Mao, and William Kerney) and volunteers (Gunnar Johnson, Jennifer Thompson). I am also grateful for the advice and support of all my Yeakley Lab colleagues (Sarah Holman, Denisse Fisher, Christa and Gunnar). Lastly, I would like to thank all of those who made this research possible, including the home-owners who generously allowed us to access their properties and the public works agencies who graciously allowed us to sample within their parks and green-spaces. v Table of Contents Abstract ..................................................................................................................... i Dedication ............................................................................................................... iii Acknowledgments ................................................................................................... iv List of Tables ........................................................................................................ viii List of Figures ......................................................................................................... ix Introduction ............................................................................................................. 1 Background .............................................................................................................. 3 Amphibian Communities ....................................................................................... 3 Amphibian Declines ....................................................................................... 3 Stream-Associated Amphibians ...................................................................... 4 Riparian Systems ................................................................................................... 6 Riparian System Functions ............................................................................. 6 Riparian System Threats and Conservation .................................................... 6 Characterization of Riparian Systems in the Pacific Northwest ....................... 7 Urbanization .......................................................................................................... 8 General Impacts of Urbanization on Riparian Areas ....................................... 8 Landscape Development: Impacts to Aquatic Systems & Amphibians ........... 9 Amphibian Conservation and Riparian Buffer Requirements ........................ 10 Urbanization of the Portland, OR and Clark County, WA Regions ............... 11 Riparian Refugia and Amphibian Communities in the Portland-Vancouver Region ............................................................................................................................ 12 Portland Streams & Riparian Areas .............................................................. 12 Amphibians in the Portland, OR Region ....................................................... 14 Potential Habitat for Lotic Amphibians in the Portland-Vancouver Region .. 16 Objectives & Hypotheses ....................................................................................... 18 Methods .................................................................................................................. 20 Research Approach .............................................................................................. 20 Site Selection ....................................................................................................... 20 Preliminary Habitat Requirements for Site Selection .................................... 21 vi Site Selection through ArcGIS Analysis ....................................................... 22 Site Ownership and Access Determination ................................................... 24 Transect Establishment and In-situ Field Sampling .............................................. 27 Transect Establishment ................................................................................ 28 Vegetation Sampling .................................................................................... 29 Stream Sampling .......................................................................................... 29 Amphibian Sampling ................................................................................... 31 Biogeographic Parameter Sampling Via Spatial Analysis ..................................... 33 Determination of Site Location .................................................................... 33 Stream-Reach Variable Collection ............................................................... 34 Surrounding Land-use ...................................................................... 34 Proximity to Road Crossing .............................................................. 36 Forested Patch Size Delineation ....................................................... 36 Sub-watershed Variable Collection .............................................................. 38 Sub-watershed Delineation ............................................................... 38 Surrounding Land-use within the Sub-watershed .............................. 42 Impervious Surface Calculation ................................................................... 43 Statistical Analyses .............................................................................................. 44 Non-Metric Dimensional Scaling ................................................................. 44 Logistic Regressions .................................................................................... 45 Contingency Tables for Categorical Variables .............................................. 46 Occupancy Modeling with the PRESENCE Program ................................... 47 Results .................................................................................................................... 50 Sites Sampled....................................................................................................... 50 Amphibian Detections .................................................................................. 50 In-situ Environmental Measurements ................................................................... 54 Water Quality .............................................................................................. 54 Stream Substrate .......................................................................................... 56 Mesohabitat ................................................................................................. 59 vii Vegetation/Canopy Cover ............................................................................ 60 Presence/Absence of Predators ..................................................................... 61 Biogeographic Environmental Measurements ....................................................... 61 Distance to Nearest Road ............................................................................. 61 Patch-size Delineation .................................................................................. 64 Sub-watershed Delineation ........................................................................... 67 Land-use Measurements ............................................................................... 67 Statistical Analyses: Environmental Variables Significant to Amphibian Occupancy ............................................................................................................................ 72 Non-Metric Dimensional Scaling ................................................................. 72 Logistic Regression of Significant Variables ................................................ 76 Contingency Tables for Categorical Variables .............................................. 82 Occupancy Modeling ................................................................................... 83 Discussion ............................................................................................................... 87 Overall Conclusions from Statistical Analysis ...................................................... 87 Relating Results to the Hypotheses............................................................... 88 Amphibian Habitat Requirements......................................................................... 89 In-Situ Variables .......................................................................................... 89 Biogeographic Variables .............................................................................. 89 Presence/Absence Modeling Trends and Anomalies ............................................ 92 Amphibian Conservation and Future Studies ........................................................ 96 Conclusion............................................................................................................ 101 References ............................................................................................................ 104 Appendices ........................................................................................................... 112 Appendix A – Potential Environmental Parameters Affecting Stream Amphibians .......................................................................................................................... 112 Appendix B – Amphibians Endemic to the Portland-Vancouver Region ............. 113 Appendix C – Mailing Postcard Example ........................................................... 114 Appendix D – Transect Location Adjustment Justifications ................................ 115 Appendix E – Amphibian Detection Raw Data ................................................... 116