AN ABSTRACT OF THE THESIS OF Matthew Hovland for the degree of Master of Science in Rangeland Ecology and Management presented on September 13, 2017 Title: Mycological Maintenance of Rangelands and the Impacts of a Thatch Forming Invasive Annual Grass (Taeniatherum caput-medusae) Abstract approved: ______________________________________________________ Ricardo Mata-Gonzalez Arbuscular mycorrhizal fungi (AMF) may exert profound influences on ecosystem resilience and invasion resistance in western North American sagebrush steppe and other arid rangeland plant communities. Maintenance of plant community structure through ecological feedbacks such as facilitation of nutrient cycling and uptake by host plants, physical and chemical contributions to soil structural stability, and mediation of plant competition suggest AMF may act as keystone facilitators in stressful arid environments. A review of the existing scientific literature highlights the relevance to AMF in sagebrush steppe rangelands, with specific focus on impacts of land management, disturbance, and invasion on AMF communities. A mycologically- based approach to invasive plant management is proposed, based on an example root AMF analysis of the native perennial bunchgrass Pseudoroegneria spicata and the exotic invasive annual grass Taeniatherum caput-medusae along an invasion gradient in eastern Oregon. This example demonstrates AMF colonization of the foundation bunchgrass species and limited colonization of the annual grass, at least in the site studied. Taeniatherum caput-medusae may effect colonization rates of dark septate endophytes in the roots of neighboring P. spicata, although direction of influence varied between years. Hypothesis testing of possible effects of T. caput-medusae on soil structure and function was explored, finding correlations between increasing invasive plant cover, and increased soil moisture levels during periods of high soil moisture (i.e. April). During drought periods a relationship was only visible on one of three research hills, with increased invasive cover correlating with decreases in soil moisture percentage. Influences of soil texture on site invasibility is discussed, along with possible long term effects of a thatch-forming invasive annual grass with limited mycorrhizal colonization, and recommendations are made for future research. ©Copyright by Matthew Hovland September 13, 2017 All Rights Reserved Mycological Maintenance of Rangelands and the Impacts of a Thatch-Forming Invasive Annual Grass (Taeniatherum caput-medusae) by Matthew Hovland A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented September 13, 2017 Commencement June, 2018 Master of Science thesis of Matthew Hovland presented on September 13, 2017 APPROVED: Major professor, representing Rangeland Ecology and Management Head of the Department of Animal and Rangeland Science Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Matthew Hovland, Author ACKNOWLEDGEMENTS The author expresses sincere appreciation for the support of his family and friends, especially his wife Amy and son Leif who are the strongest and most beautiful. Leif’s grandparents are west coast rock hounds holding hands on the beach in vest coats. Doctor Toby Westberry is a role model surfing in a sea of phytoplankton. The great naturalist Howard Bruner paints the path with eloquence and provokes a thoughtful conversation. Advising plant physiologist Dr. Ricardo Mata-Gonzalez is a mid-range jump shot specialist. Committee members Dr. Jennifer Parke and Dr. David Myrold are like ice skating instructors who guide glidingly and inspire experimentation. Doctor Jane Smith knows the location of every hidden matsutake. If this work is of any merit it has been made possible by a community of scientific researchers willing to communicate their trials and observations, specifically those researchers interested in plant-fungi and plant-soil relationships. Sincere appreciation is extended to Dr. R. Paul Schreiner of the USDA Agricultural Research Service who provided the space and equipment necessary for observations of mycorrhizal colonization and treated the author with unrivaled kindness, generosity, truthfulness and respect. This project would not have been possible without the encouragement of Dr. Thomas J. Rodhouse and contributions from the National Park Service Upper Columbia Basin Network Cooperative Task Agreement P13AC00136. Those individuals who helped with sampling on the hills of Clarno at any time of year are in the author’s debt (i.e. the botanist Bob Hladky), as are those who were at any time unwillingly subjected to the author’s mycocentric soliloquys. CONTRIBUTION OF AUTHORS Ricardo Mata-Gonzalez served as adviser, discussing research weekly, and providing comments on all drafts of the two manuscripts composing this thesis. Thomas J. Rodhouse was involved in the initial conception of the study including site selection, design, and preliminary data collection, as well as providing feedback on multiple drafts. R. Paul Schreiner provided guidance, feedback, comments, intellectual discussions, laboratory space, equipment, and assistance in analysis of mycorrhizal colonization. David Eduardo Prado-Tarango assisted in field sampling and data collection, soil lab analysis, and provided comments and intellectual discussions concerning soil characteristics. TABLE OF CONTENTS Page Thesis Introduction ..............................................................................................….... 1 Chapter 1: Mycorrhizal Maintenance of Rangelands: Conceptualizing the Relationship between Mycorrhizal Fungi and Ecosystem Resilience and Resistance to Invasion in Sagebrush Steppe ……………..………….....................………………………………………… 3 Abstract ………………………………………………………..…………...... 4 Introduction ….…………………………...……………….………………..…6 AMF Mediated Ecosystem Resilience …….………….………….……….....11 Stress amelioration….............…………….…………………...……..12 Soil functional and structural stability ……………..……….……….13 AMF mediated plant competition ...……...……………………….…14 AMF Disturbance Ecology …….......................…………………………..…16 Plant-AMF Associations in Sagebrush Steppe Plant Species …………….....18 AMF obligate keystone shrub – Artemisia tridentata …...….............18 Facultative keystone bunchgrass – Pseudoroegneria spicata ……....20 Facultative invasive annual grass – Bromus tectorum ……………....22 Invasive annual grass with limited colonization – Taeniatherum caput- medusae ……………………………………..........................................23 AMF obligate invasive forb – Centaurea maculosa ……...............…25 Non-mycorrhizal invasive forbs – Sisymbrium species ……..............26 Non-mycorrhizal invasive forb – Salsola kali ….…………………...27 Case Study: Mycorrhizal Colonization along a Medusahead Invasion Gradient ……………………………………………………………………...28 TABLE OF CONTENTS (Continued) Page Implications for Research and Management: Advancing the Understanding and Utilization of AMF Ecology in Sagebrush Steppe Restoration and Management ……………………………………………………..……….….30 Suggested Methods ………………………………………..……...…31 Mycorrhizal Status and Growth Benefits ……………………31 AMF Community Structure ………………....………………33 Restoration ………………………………………………..…35 Conclusion……………………………………………………………..…….36 References …………………………………………………………………...38 Figures …………………………………………………………………….....61 Chapter 2: Investigating Soil Conditioning Effects of a Thatch-Forming Invasive Annual Grass along an Invasion Gradient in a Protected Area Oregon, USA …………………………………………………………………………..…..…68 Summary …………………………………………………………………….69 Introduction ……………………………………………………………….....71 Materials and Methods ………………………………………………………75 Site Description …………………………………………………...…75 Soil Moisture ……………………………………………………...…77 Soil Analysis ………………………………………………………...77 Root Analysis ………………………………………………………..78 Statistical Analysis …………………………………………………..79 Results ……………………………………………………………………….79 Soil Moisture ………………………………………………………...79 Texture …......….…………………………………………………….80 TABLE OF CONTENTS (Continued) Page Respiration……………... …………………………………………...81 pH ...………………………………………………………………….81 Percent root length colonization ……………………………….……81 Discussion ……..…………………………………………………………….82 Wet season soil moisture and vegetation cover ………………..……83 Drought season effects and clay percentage thresholds …………..…84 Mycorrhizal colonization …………………………………………....86 Further research ……………………………………………………..87 Conclusion …………………………………………………………..88 Acknowledgements ………………………………………………………….89 References ……………….…………………………………………………..90 Figures ……………………………………………………………………….96 Thesis Conclusion ………………………………………………………………….102 Comprehensive Bibliography …………………………………………………...…104 LIST OF FIGURES Figure Page 1. Mycorrhizal feedbacks contributing to resilience/resistance……………………...61 2. Impacts of disturbance and mycorrhizal status of plant invaders...………………62 3. Mycologically based invasive plant management framework...………………….63 4. Dimorphism expressed in bluebunch wheatgrass roots……………………….….64 5. Paris-type colonization of bluebunch wheatgrass roots.....……………………….65 6. Simultaneous colonization of bluebunch wheatgrass roots by arbuscular mycorrhizal and dark septate fungi ….………………………………………………66 8. Medusahead root morphology…..………………………………………………..66 9. Medusahead colonization by AMF and DSE in June and July …….………….…67