Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-2008 Granivores and Restoration: Implications of Invasion and Considerations of Context-dependent Seed Removal Steven M. Ostoja Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Biology Commons, Ecology and Evolutionary Biology Commons, and the Other Forestry and Forest Sciences Commons Recommended Citation Ostoja, Steven M., "Granivores and Restoration: Implications of Invasion and Considerations of Context- dependent Seed Removal" (2008). All Graduate Theses and Dissertations. 130. https://digitalcommons.usu.edu/etd/130 This Dissertation is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. GRANIVORES AND RESTORATION: IMPLICATIONS OF INVASION AND CONSIDERATIONS OF CONTEXT-DEPENDENT SEED REMOVAL By Steven M. Ostoja A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Ecology Specialization: Conservation Biology Approved: ____________________ ____________________ Eugene W. Schupp James A. MacMahon Major Professor Committee Member ____________________ ____________________ Karen H. Beard Thomas A. Monaco Committee Member Committee Member ____________________ ____________________ Christopher A. Call Byron R. Burnham Committee Member Dean of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2008 ii ABSTRACT Granivores and Restoration: Implications of Invasion and Considerations of Context-Dependent Seed Removal by Steven M. Ostoja, Doctor of Philosophy Utah State University, 2008 Major Professor: Eugene W. Schupp Department: Wildland Resources Granivores are important components of sagebrush communities in western North America. These same regions are being altered by the invasion of the exotic annual Bromus tectorum (cheatgrass) that alters physical and biological dynamics in ways that appear to promote its persistence. This research directly relates to the restoration of B. tectorum-dominated systems in two inter-related ways. First, because these landscapes have large quantities of seeds applied during restoration, it is important to determine the major granivore communities in intact sagebrush communities and in nearby cheatgrass- dominated communities. Second, it is important to develop an understanding of patterns of seed harvest by granivores. In addition to the data chapters there are two review chapters; Chapter 1 highlights factors contributing to seed removal and Chapter 7 provides ecologically based techniques that could minimize the negative consequences of granivores during ecological restoration. Common groups of ants showed increased abundances; uncommon species and functional groups were generally negatively impacted by cheatgrass (Chapter 2). Conversely, rodents were negatively impacted by iii conversion to cheatgrass (Chapter 4). Ant seed removal was highly context-dependent (Chapter 3), depending on the background vegetation (large-scale among-patch effects), foraging distance from the nest mound (small-scale among-patch effects), and the presence of other seed species in mixture (within-patch effects). In addition, cheatgrass provided associational resistance to native seeds in mixture, meaning the presence of cheatgrass increased native seed survival. In Chapter 5 a novel statistical technique in the ecological sciences showed that rodents have marked preferences for some seeds over others and that more seeds were removed in sagebrush compared to cheatgrass- dominated sites, although associational effects among seed mixtures were not detected. In Chapter 6 we show that the amount of seed harvested depended on both intraspecific and interspecific seed density. B. tectorum seeds had associational susceptibility (increased harvest) in the presence of native seeds. Although the reciprocal effect may occur, we did not find statistical support for it. These sets of studies are not only of basic ecological interests, but are also important for developing management strategies for restoration of these degraded lands. (216 pages) iv ACKNOWLEDGMENTS The decision to pursue a doctoral degree was not difficult, nor was the choice of major or focus of research. However, I knew all too well the importance of a suitable match between the student and the advisor. After meeting my advisor, Eugene W. Schupp, I knew within hours that he would be an ideal match for me. I was correct. Yet during the past five years as his student I have come to realize and fully appreciate what an excellent mentor, advisor, professional, and ecologist Dr. Schupp is. He had always maintained the perfect balance of fairness while being quite firm, negotiating constructive criticism with kindness, and knowing when to let up and when to hold steady on the reins of my sometimes over zealous ecological curiosity. Many of his lessons I did not understand at the time, but trusted his intentions and direction only to learn later the value of his teaching. I am very grateful to Geno for all that he has shared and taught and hope someday I can share a fraction of his lessons with others keen to pursue this scientific ambition. In addition to the edification from my advisor, I am very grateful to my committee, Karen Beard, Chris Call, James MacMahon, and Tom Monaco. Their patience, conversations, and encouragements were invaluable assets in the production of the research contained herein. In that group I also include Dr. Bill Longland, who was very helpful with numerous questions and discussions and who has been a wonderful collaborator in side projects with Geno and me. I thank many professors in both the College of Natural Resources and/or the Ecology Center for helpful and encouraging conversations and advice, including Helga Van Miegroet, James Long, Mike Wolf, John Malechek, and Johan Du Toit among many others. I also wish to thank David Pyke (USGS-OSU), Paul Doescher (OSU), Bob v Nowak (UNR), Jeanne Chambers (USFS-UNR), and Stephen Vander Wall (UNR) for helpful conversations and/or logistical help with my research. This work could not have been completed without the assistance of the staff of the Ecology Center, including Susan Durham, Marv Bennett, and Stephanie White, and Lana Barr and Gaye Griffith from the Department of Wildland Resources. I am also grateful to the past and current members of the Schupp lab: Tarek Milleron, Jeff Burnham, Kelly Sivy, Dan Christensen, Melissa Harvey-LaMalfa, Ryan Barker, and Tyler Logan especially. I am also grateful to Greg Larson, Lisa Ellsworth, Jacob Landmessor, Rob Klinger, Bill Fox, Amanda Murray, and Vijay Satyal for all their help and/or encouragement. In the pursuance of this doctoral degree the encouragement and assistance of my family and friends were critical. I am grateful to my sister, Susan Halsted, my grandparents Eva and Frank Ostoja, and my mother Joey Halsted, who are kind, caring, and encouraging people. Akin to the many wonderful qualities of my mom, Emily Bradley is not only the most loving and understanding partner I could ever hope to know, she was very understanding when my main focus was realizing the completion of this work. Not to mention, Emily has an uncanny hand with kangaroo rats. Steven Muir Ostoja vi CONTENTS ABSTRACT……………………………………………………………….…………….. ii ACKNOWLEDGMENTS………………………………………………..……………... iv LIST OF TABLES……………………………………………………...………………. vii LIST OF FIGURES..………………………………………………...…………………. iix CHAPTER 1. IMPORTANCE OF SEED CHOICE AND REMOVAL: SEED CHARACTERISTICS AND ENVIRONMENTAL INFLUENCES…………………………………...……… 1 2. ANT ASSEMBLAGES IN INTACT SAGEBRUSH AND CONVERTED CHEATGRASS-DOMINATED HABITATS IN RUSH37 VALLEY, TOOELE COUNTY, UTAH, USA……………………………………………….…………….. 37 3. ASSOCIATIONAL RESISTANCE AND THE IMPORTANCE OF AMONG- AND WITHIN-PATCH CHARACTERISTICS ON SEED SELECTIVITY ……………... 59 4. RODENT ASSEMBLAGES IN GREAT BASIN SAGEBRUSH COMMUNITIES AND CONVERTED BROMUS TECTROUM HABITAT TYPES……………..….103 5. ASSOCIATIONAL1 INTERACTIONS WITHIN SEED MIXTURES: BETA- DISTRIBUTED REGRESSION AS AN ALTERNATIVE TO TRADITIONAL STATISTICAL TECHNIQUES…………………………………………………..... 122 6. INTER-1 AND INTRA-SPECIFIC SEED DENSITIES AFFECT SEED PREFERENCES BY GRANIVOROUS RODENTS…………………………….… 155 7. GRANIVORY IN THE CONTEXT OF RESTORATION: ECOLOGICAL FOUNDATIONS AND MANAGEMENT APPLICATIONS………………...…… 181 APPENDICES………………………………………………………………………… 217 CURRICULUM VITAE………………………………………………………………. 221 vii LIST OF TABLES Table 2.1. Total numbers of ants of identified species from pitfall trap samples by vegetation type. ...................................................................................................................... 53 2.2. Means for Simpson’s, Shannon’s, and McIntosh diversity indices and Shannon’s and McIntosh evenness indices by vegetation type ............................................. 54 2.3. Results of paired t-tests comparing cheatgrass-dominated and sagebrush plots for total ant abundance and for species richness, diversity indices, and evenness indices . ................................................................................................................. 55 3.1. Three-way factorial analysis of variance (ANOVA) of seed harvest in A) monospecific treatments, B) non-B. tectorum seed harvest in mixture treatments, and C) B. tectorum seed harvest