Native Pollinators: the Effects of Livestock Grazing on Montana

Native Pollinators: the Effects of Livestock Grazing on Montana

NATIVE POLLINATORS: THE EFFECTS OF LIVESTOCK GRAZING ON MONTANA RANGELANDS by Gabrielle Elizabeth Blanchette A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Entomology MONTANA STATE UNIVERSITY Bozeman, Montana November 2019 ©COPYRIGHT by Gabrielle Elizabeth Blanchette 2019 All Rights Reserved ii ACKNOWLEDGEMENTS This project would not have been possible without the help of many hard-working individuals. I would like to first and foremost thank my advisor Hayes Goosey in his assistance in, mentorship, and guidance throughout the two years of this project. Hayes was essential in much of the work I have completed and always encouraged me to ask questions and dive into these topics further. Additionally, I would like to thank my committee members Mike Ivie and Craig Carr for their wonderful commitment to making sure I had the tools necessary to identify insects, plants, and understand rangeland ecology. I would like to also thank Casey Delphia for her wonderful mentorship in the identification of native bees. Without her guidance, identification would have been difficult. I would also like to thank Skylar Vold, Megan Milligan, and the Wildlife Ecology Lab of Dr. Lance McNew for providing Sidney, MT cattle stocking rates, pastures sizes, and a GIS map outlining the sampled pastures. Funding for this project was provided by MT FWP Pitman-Robertson, USDA NRCS CEAP, and Tom Helm and Alieda Stone. iii TABLE OF CONTENTS 1. INTRODUCTION AND LITERATURE REVIEW .......................................................1 Background of Rangeland Grazing in the Western United States and Montana...……. 1 The Importance of Rangelands ................................................................................6 Rural Economy ............................................................................................6 Environment .................................................................................................8 Pollinators as A Critical Component in Montana Ecosystems ..............................12 Pollinators as Critical Components to Rangelands ................................................14 Hymenoptera ..............................................................................................14 Lepidoptera ................................................................................................16 Diptera........................................................................................................18 Modern Role in Pollination ........................................................................20 2. EFFECTS OF LIVESTOCK GRAZING ON POLLINATORS- SIDNEY ..................22 Introduction ....................................................................................................................22 Study Area .....................................................................................................................23 Methods .........................................................................................................................24 Pollinator Surveys ..................................................................................................24 Weather and Degree Days .....................................................................................25 Setting Traps ..........................................................................................................25 Collecting ...............................................................................................................28 Processing Samples ................................................................................................29 Vegetation Cover ...................................................................................................30 Statistical Analysis .................................................................................................31 Results ...........................................................................................................................32 Activity-Density .....................................................................................................32 Genera....................................................................................................................38 Vegetation Cover ...................................................................................................43 Discussion .....................................................................................................................46 3. EFFECTS OF LIVESTOCK GRAZING ON POLLINATORS- ROUNDUP ..............54 Introduction ....................................................................................................................54 Study Area .....................................................................................................................55 Methods .........................................................................................................................56 Pollinator Surveys ..................................................................................................56 Weather and Degree Days .....................................................................................57 Setting Traps ..........................................................................................................57 Collecting ...............................................................................................................58 Processing Samples ................................................................................................58 Vegetation Cover ...................................................................................................60 iv TABLE OF CONTENTS CONTINUED Statistical Analysis .................................................................................................60 Results ...........................................................................................................................61 Activity-Density .....................................................................................................61 Genera....................................................................................................................67 Vegetation Cover ...................................................................................................71 Discussion .....................................................................................................................73 4. IMPLICATIONS ...........................................................................................................81 REFERENCES CITED ......................................................................................................84 APPENDICES ...................................................................................................................95 APPENDIX A: Supplemental Pollinator Data ......................................................96 APPENDIX B: Environmental Parameters .........................................................105 v LIST OF TABLES Table Page 1. Sidney, MT grazing system ............................................................................28 2. Daubenmire cover class range of coverage percentages ..................................31 3. Least squared means of weekly activity-density for All pollinators, Hymenoptera pollinators, and secondary pollinators activity-density during the 2016, 2017, and 2018 field seasons east of Sidney, MT .....................................................................36 4. Averaged least squared means from two-years 2016 and 2018 of study of weekly total, Hymenoptera, and secondary pollinator activity-density east of Sidney, MT ................................................37 5. Total primary pollinator Hymenoptera Genus (subgenus), and secondary pollinator Diptera family Syrphidae and order Lepidoptera from sampling seasons 2016, 2017, and 2018 east of Sidney, MT ...........................................................................................41 6. Weekly least squared mean comparisons of vegetation metrics for sampling seasons 2016, 2017, and 2018 east of Sidney, MT ...........................................................................................44 7. Averaged weekly least squared means across all three sampling years 2016, 2017, and 2018 east of Sidney, MT ..............................46 8. Daubenmire cover class range of coverage percentages ..................................60 9. Least squared means of weekly total, Hymenoptera, and secondary pollinator activity-density from sampling years 2016, 2017, and 2018 north of Lavina, MT .....................................................64 10. Least squared means of combined 2016, 2017, and 2018 weekly total, Hymenoptera, and secondary pollinator activity-density north of Lavina, MT ...............................................................66 11. Total seasonal primary pollinator Hymenoptera Genus (subgenus), and secondary pollinators Diptera family Syrphidae and order Lepidoptera from 2016, 2017, and 2018 north of Lavina, MT ..............69 vi LIST OF TABLES CONT. Table Page 12. Weekly least squared mean comparisons of vegetation metrics for sampling seasons 2016, 2017, and 2018 north of Lavina, MT ..................................................................................................72 13. Averaged weekly least squared mean comparisons of vegetation metrics across two study years 2017 and 2018 north of Lavina, MT .........................................................................................73

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