AN ABSTRACT OF THE THESIS OF

Brogan L. Watson for the degree of Master of Science in Rangeland Ecology and Management presented on June 4, 2020.

Title: Forb Community Response to Various Disturbances in the Pacific Northwest Bunchgrass Prairie

Abstract approved: ______Lesley R. Morris Scott B. Lukas

Observed declines in native pollinator species worldwide has generated concern and focused research into the disturbances, past and present, which may have contributed to these losses. In grasslands, for example, habitat degradation and fragmentation from historical and current crop production and livestock grazing has left only a few remnants of the native systems. The remaining remnants face further modification by altered fire regimes and invasive species. One of the most threatened and understudied of the fragmented temperate grasslands is the Pacific Northwest Bunchgrass Prairie (PNB) located in the northwest region of the United States. The overarching objective for this thesis, accomplished through two research studies, was to examine how a variety of different disturbances affect the floral resources in the PNB. In the first study, we explored the individual and interactive effects of three disturbances (prescribed fire, grazing, and invasive species) on the floral resources within the largest remaining remnant of the PNB prairie, known as the Zumwalt Prairie. Specifically, we addressed how prescribed fire, grazing, and their interactions impact forb community composition, abundance, richness, and diversity over 12 years. We also examined the response of forb cover, richness, and diversity to the increasing cover of the newest invasive species threat to the PNB, Ventenata dubia. Our results indicated that prescribed fire has more influence on forb community composition over time than moderate grazing alone or no livestock grazing and that a ten-year fire return interval does not significantly influence forb species richness or diversity in this system. The indicator species for each of the treatments illustrated that maintaining disturbances like prescribed fire and herbivory may help support certain forbs that are important

to pollinators and for culturally significant plants of the region’s indigenous peoples. We found significant negative correlations between forb cover and richness once the increase in V. dubia cover ranged between 20-37%, suggesting a threshold for impacts on the forb community that should be monitored. In the second study, we explored the legacy effect on forb communities where historical cultivation sites were abandoned and seeded with exotic pasture grasses (seeded old fields) on the PNB. Specifically, we evaluated differences in forb community, abundance, richness, and diversity between these sites (treatments), tested for indicator species within each treatment, and included comparisons over the course of two consecutive growing seasons. Native prairie sites contained more abundant, rich, and diverse floral resources than seeded old fields across growing seasons and in both sampling years. Our findings add to the evidence that the legacy of cultivation and reseeding disturbances can persist long after these land uses end, especially on forb communities. Further, our findings suggest this legacy may decrease habitat quality for pollinators in seeded old fields, especially in August. Differences in indicator species between sites and over the growing season also identified important areas for future research to maintain culturally important forb species which may help enhance floral resources for pollinators, especially in the fall. The findings in this study highlight a need for more research into how pollinators respond to these differences and how active restoration may be needed to conserve forb communities for pollinators and culturally significant forb species for indigenous people in the region. Both of these studies are the first to address questions about how these disturbances (prescribed fire, livestock grazing, invasion by V. dubia, and cultivation legacies) affect the composition, abundance, richness, and diversity of forb communities on the PNB. The results from this research can help land managers, mainly in the PNB ecosystem, and also adds to the information needed to help conserve and promote floral resources for native pollinators. More research needs to focus upon understanding the continuum of these habitats, as they are all extremely important for conservation of native pollinators and maintenance of all ecosystem services.

©Copyright by Brogan L. Watson June 4, 2020 All Rights Reserved

Forb Community Response to Various Disturbances in the Pacific Northwest Bunchgrass Prairie

by Brogan L. Watson

A THESIS

submitted to

Oregon State University

in partial fulfillment of the requirements for the degree of

Master of Science

Presented June 4, 2020 Commencement June 2020

Master of Science thesis of Brogan L. Watson presented on June 4, 2020.

APPROVED:

Co-Major Professor, representing Rangeland Ecology and Management

Co-Major Professor, representing Rangeland Ecology and Management

Head of the Department of Animal and Rangeland Sciences

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.

Brogan L. Watson, Author

ACKNOWLEDGEMENTS

I would like to thank Lesley Morris for her continuous support, advice, mentorship, encouragement, and dedication to this project. Also thank you to Scott Lukas for serving as my co-advisor, Joshua Leffler for his guidance with the data analysis, and to Pat Shaver who provided helpful suggestions, advice and edits throughout this process. Critical to the completion of this work was funding from the Foundation for Food and Agriculture (ID: 549031) with the support from the Oregon Agricultural Research Foundation. Special thanks to Sandra DeBano for organizing this project, her guidance in analysis and to the field crews for helping with data collection. I would not have been able to complete this research without the help of staff and researchers at The Nature Conservancy, specifically Heidi Schmalz. In addition, thanks to Katie Emerson, Kaylee Littlefield, Luke Ridder, McKaden Manderbach, and Molly Rygg for all their hard work in the field. Finally, I would like to thank my family and friends for their constant encouragement and endless support while pursuing this degree.

CONTRIBUTION OF AUTHORS

Scott B. Lukas, Lesley R. Morris, Sandra J. DeBano, and Heidi J. Schmalz contributed to all parts of this thesis including study design, implementation, data analysis, and writing in all chapters. A. Joshua Leffler led the data analysis for both studies and contributed to writing in both chapters. Scott R. Mitchell collected the soils data used in Chapter 3.

TABLE OF CONTENTS

Page

Chapter 1: Introduction.....………………..…..…...……………………….…………...……...….1

1.1 Introduction………………………………………………………………………..…..2

1.2 Literature Cited.…………………….………………………………………………....7

Chapter 2: Forb Community Response to Prescribed Fire, Livestock Grazing, and Invasive Species in the Pacific Northwest Bunchgrass Prairie.…………………………………………...12

2.1 Introduction………...…………………………………………………………..….…14

2.2 Methods...... ………...……………………………………………………………...…17

2.3 Results…...………………………………………………………………………...…20

2.4 Discussion...... …………………………………..………………………....22

2.5 Conclusion….....……………………………………………………..……………....26

2.6 Literature Cited.…………………………………………………….……………..…28

Chapter 2 Figures……………………………………………..……………………………...…..35

Chapter 2 Tables……………………………………………………………………..……...... 43

Chapter 3: Comparing Floral Resources between Native Prairie and Seeded Old Fields on the Pacific Northwest Bunchgrass Prairie…………………………………………………………...45

3.1 Introduction…………………………………………………………………………..47

3.2 Methods………………………………………………………………………………50

3.3 Results…………...…………………………………………………………….……..53

3.4 Discussion…………...……...... 55

3.5 Conclusion...... 61

3.6 Literature Cited…………....………………………………………………………....63

Chapter 3 Figures…………..………………………………………………………………….....70

TABLE OF CONTENTS (Continued)

Page

Chapter 3 Tables………………………………………………………………...…...... 77

Chapter 4 General Conclusions...... 80

4.1 Conclusion...... 81

4.2 Literature Cited…………..….……………………………………………………….85

General Bibliography…………...…..…………………………………………………………....87

Appendix...………………………………..……………………………………………………...99

LIST OF FIGURES

Figure Page

2.1 Map of Fire/Grazing plots with prescribed burn units....……………………….....…....……35

2.2 Plot layout for the sampling years 2010, 2016, and 2018…………...…..………………...... 36

2.3 Monthly precipitation on the Zumwalt Prairie for each sampling year and a fourteen year average………………………….………………………………………………………………..37

2.4 NMS ordination of sample units in forb species space……………..…………………….….38

2.5 Bargraph of mean forb cover for each treatment…………...…...... ……...………………….39

2.6 Linear regression of forb and V. dubia cover in 2016...... ……...………………….40

2.7 Linear regression of forb cover and V. dubia cover in 2018.……………..…………………41

2.8 Linear regression of forb species richness and V. dubia cover in 2018………………..…….42

3.1 Map of native prairie and seeded old field plots.……………….………………………..…..70

3.2 Plot design for conducting blooming stem count sampling…………...…..……….……...…71

3.3 Monthly precipitation on the Zumwalt Prairie for both sampling years, and a fourteen year average.…………………………………………………………………………………………..72

3.4 Boxplots displaying differences in bloom abundance, species richness and diversity between treatment types across the growing season………………………………………………………73

3.5 Multi-Response Permutation Procedures results displaying differences between treatments throughout the growing season for each sampling year………………………………………….74

3.6 NMS ordination of sample sites in forb species space with a joint plot of environmental variables overlaid…………………………...………………….………………………...………75

3.7 Boxplots displaying differences in bloom abundance, species richness and diversity across (a) the growing seasons and (b) between years……………………………....……………….…76

LIST OF TABLES

Table Page

2.1 Permutational multivariate analysis of variance (perMANOVA) results of year and treatment effects, individually, and as an interaction on forb species composition…...……………………43

2.2 Linear mixed-effects results of year and treatment effects on forb cover, species richness, and diversity…………………………………………………………………………………………..43

2.3 Mean forb cover (%), species richness, and diversity for each sample year and treatment...... 43

2.4 Indicator species analysis results for each treatment………………………………………...44

2.5 Results of linear regression models of forb species diversity and V. dubia cover for sampling years separately, and combined………………………….………………………………………44

3.1 Significant indicator species for each treatment, and maximum indicator values for native prairie and seeded old fields……………………………………………………………………..77

3.2 Significant indicator species for each sampling period throughout the growing season, both years combined between native prairie and seeded old fields………...... 78

3.3 Indicator species analysis for sampling periods throughout the growing season, with separate indicator values for each sample year…………………….……………………………………...79

LIST OF APPENDICES

Appendix Page

A.1 Coordinates of sample sites Chapter 2 study..………………..….………………...100

A.2 Coordinates of sample sites for Chapter 3 study…….……...... 101

A.3 Chapter 3 Forb species encountered throughout the study, with indication of when each species was blooming……………………………………………………………..102

DEDICATION

For Bud – who inspired my love for the great outdoors.

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Chapter 1: Introduction

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1.1 Introduction

Ecosystem services provided by pollinators in native and managed systems are essential for the pollination of over 75% of flowering plants, including crop species (Klein et al. 2007). There are numerous and diverse types of pollinators (Allen-Wardell et al. 1998), yet many crop systems have to rely on managed honey bee hives to ensure crop pollination when native pollinators are not present (Klein et al. 2007). However, recent declines in native pollinator populations (Potts et al. 2010) have raised concern worldwide (Potts et al. 2003; Potts et al. 2009; DeBano et al. 2016) that this vital ecosystem service may be threatened. In wildland systems, such as grasslands, nesting and floral resources are naturally available for pollinators (Corbet et al. 1992; Gathmann and Tscharntke 2002; Delaney et al. 2015) and provide pollen and nectar throughout the season (Mallinger et al. 2016) from a highly abundant and diverse community of flowering plant species (Clough et al. 2014). The inclusion of these resources in both managed and wildland systems where pollinators are active are crucial.

Land-use changes such as habitat degradation and fragmentation (Potts et al. 2010; Roof et al. 2018), agricultural development (Steffan-Dewenter et al. 2005), crop production and intensification (Potts et al. 2010; Clough et al. 2014), coupled with a changing climate affect remnants of native grasslands and the resources they provide are under threat. Unlike recent changes in land-use that continue to threaten grasslands, these ecosystems have actually evolved with two anthropogenic disturbances (Bowles et al. 2003; Potts et al. 2003; Harrison et al. 2003; Bowles and Jones 2013; Huang et al. 2015), fire and herbivory (Lovell et al. 1982; Gibson 2009). Fire and herbivory are common natural and anthropogenic disturbances in grasslands worldwide (Bowles et al. 2003; Potts et al. 2003; Harrison et al. 2003; Bowles and Jones 2013; Huang et al. 2015), and occur on one of the most threatened and understudied of the fragmented temperate grasslands, the Pacific Northwest Bunchgrass Prairie (PNB) located in the northwest region of the United States (U.S.) (Tisdale 1982).

Prescribed fire

Fire can have complicated impacts on grasslands and forb communities depending upon the timing, intensity, and severity of the burn (Lovell et al. 1982; Spasojevic et al. 2010; Collins and Calabrese 2012; Bowles and Jones 2013). For example, fire causes changes in the canopy structure which has the potential to reduce competition from overstory vegetation resulting in 3 increased seed production, germination, and more inflorescences of forbs (Wrobleski and Kauffman 2003), depending upon their reproductive needs. Prescribed fire has also been used to manage invasive species (Pollak and Kan 1998; Case and Staver 2017; Ridder 2019), stimulate forb germination (Ruthven et al. 2000; Harrison et al. 2003), extend active growth periods (Wrobleski and Kauffman 2003), and can increase blooms of annual floral resources, especially within the first year (Potts et al. 2003). Furthermore, fire opens up areas of bare ground, which increases soil moisture, nutrients, and available light allowing annual forbs to establish in open sites (Kauffman et al. 1997). Some forb species which reproduce from belowground organs are highly adapted to fire and can respond quickly and favorably to this disturbance (Pechanec et al. 1954).

Herbivory

While it is recognized that other ungulates may also contribute to herbivory, such as elk (Cervus canadensis) and deer (Odocoileus hemionus), in the context of this thesis the anthropogenic disturbance of herbivory will focus on grazing pressure from cattle (Bos taurus). The relationship between cattle grazing and forbs can be complex, as grazing can inhibit forb abundance in semi- arid systems (Masunga et al. 2012) or give them an advantage by reducing competition from graminoids (Ruthven et al. 2000). Livestock grazing can have direct effects on floral resources by the removal of apical meristems, which can prevent blooming (Fynn et al. 2009), and indirect effects by altering soils (Schmalz et al. 2013) in a way that can affect ground-nesting bee species (Öckinger and Smith 2007), or help spread exotic plant species that reduce forb abundance (Bartuszevige and Endress 2008). In contrast, at moderate utilization, grazing can increase forb species richness and flowering stem density by reducing dominant vegetation and allowing other species to flower (Kearns and Oliveras 2009). Additionally, herbivory can increase species diversity (Belsky 1992; Olff and Ritchie 1998), and large ungulates have the potential to be efficient native seed dispersers (Olff and Ritchie 1998).

The type of grazing regime is an important component for managing community structure, and if managers use strategic approaches they can positively influence floristic composition (Zimmer et al. 2010). For example, reports of different grazing regimes show higher native forb frequency and richness when a spring or summer-rest period is incorporated into the 4 plan (Zimmer et al. 2010). Fundamentally, most of these grazing effects on vegetation depend on the intensity, timing, duration, frequency, and type of grazer.

Exotic species

Exotic plant species can change composition and structure of native plant communities, reduce richness and diversity, and reduce soil stability (Traveset and Richardson 2006; Morris et al. 2011; Endress et al. 2019). Invasive plants are known to both directly and indirectly affect native plants by creating monocultures, preventing native species establishment (Nelson 1997; Morris et al. 2014; Wallace and Prather 2016), and by limiting resources for neighboring plants (Brooks et al. 2004). The introduction of exotic species into native grasslands has been documented to reduce floral resources (Kwaiser and Hendrix 2008; Delaney et al. 2015) that pollinators are dependent on throughout the growing season. One particular species of concern on the PNB is the invasive winter annual grass, Ventenata dubia, which appears to be increasing in this grassland regardless of prescribed fire or livestock grazing (Ridder 2019). The invasion of V. dubia is negatively related to the abundance of perennial native forbs (Averett et al. 2020), increased primarily in areas of abandoned agriculture (old fields), and invaded other prairie sites across the PNB (Endress et al. 2019).

Disturbances in the Pacific Northwest Bunchgrass Prairie

The PNB has a history much like other grasslands in North America. Euro-American settlement brought large herds of cattle (Bartuszevige et al. 2012) and suppressed natural fire in the region (Black et al. 1998; Bartuszevige et al. 2012; Morgan et al. 2020). But unlike other grasslands, very little research has examined the impacts of these two disturbances or their interaction on the forb communities of the PNB. Just as other grasslands became fragmented by agricultural practices (Fuhlendorf et al. 2002), the PNB was transformed into a patchwork of crop production with over 90% of it lost to agricultural transformation (Tisdale 1982). However, a portion known as the Zumwalt Prairie was only marginal for agricultural production, so many of the fields were abandoned and subsequently seeded with exotic pasture grasses (seeded old fields) like Kentucky bluegrass (Poa pratensis), Canada bluegrass (Poa compressa), timothy (Phleum pretense) and intermediate wheatgrass (Thinopyrum intermedium) (Bartuszevige et al. 2012; Endress et al. 2019). 5

Exotic species intentionally seeded into grasslands can have lasting and detrimental impacts on native bees, as old fields once cultivated for cereal grains do not provide adequate nesting habitat or forage species for pollinators (Corbet et al. 1992). Seeded old fields have similar patterns in low forb abundance (Johnson 2008; Morris et al. 2014), and richness. On the Zumwalt Prairie, seeded old fields contain low native plant species richness, potentially fewer native perennial forbs, and more exotic species than native prairie sites (Taylor and Schmalz 2012; Taylor et al. 2013). Ecosystems that contain low or no flowering plants may be inadequate for supporting pollinator communities (Robson 2019), therefore, it is important to examine these factors regarding floral resources in seeded old fields. However, there is less research directly addressing differences in forb community composition, cover, richness, or diversity in seeded old fields compared to native prairies, or how any of these responses vary throughout growing seasons.

Given the need for more research to assist conservation of pollinators within limited remnant grasslands as well as working landscapes, the overarching objective of this thesis was to examine how a variety of common disturbances impact the forb community and floral resources which native pollinators depend upon in the PNB. To meet this objective, two studies were completed on The Nature Conservancy’s Zumwalt Prairie Preserve (ZPP). For the first study (Chapter 2), we used monitoring data on forb cover in 2008, 2010, 2016, and 2018 from permanent plots within a prescribed fire and grazing study. The permanent monitoring plots were established in 2004 to observe long-term impacts of fall prescribed fire and livestock grazing on four blocks across the prairie with four treatment types: livestock grazing, prescribed burns, both grazing and burning, and neither grazing nor burning. We examined how the forb community responded to prescribed fire, livestock grazing, and their interaction over ten years. In addition, since there was an increase in V. dubia cover on these plots (Ridder 2019), we examined the relationship between this invasive species and forb cover, richness, and diversity since 2008.

The second study (Chapter 3), explored how floral resources between native-prairie sites and seeded old fields differ in forb composition, abundance, richness, and diversity over two growing seasons in 2018 and 2019. Disturbance effects on native bee habitat can also depend on the species of bee (Kimoto et al. 2012) but since bee richness is correlated with plant richness (Potts et al. 2003), monitoring these characteristics can provide useful information for 6 conservation. The results of these studies are intended to fill research gaps and provide useful information regarding forb communities for future management and conservation of the ZPP, the Zumwalt Prairie overall, and other grassland systems. Since most of the PNB is privately owned and operated for agriculture, management of remnant and working prairie landscapes contribute to the conservation of pollinator habitats.

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1.2 Literature Cited

Allen-Wardell, G., et al. 1998. The potential consequences of pollinator declines on the conservation of biodiversity and stability of food crop yields. Conservation Biology 12:8- 17. Averett, J.P., Morris, L.R., Naylor, B.J., Taylor, R.V., and B.A. Endress. 2020. Vegetation change over seven years in the largest Pacific Northwest Bunchgrass Prairie remnant. PLoS ONE 15(1):1-20. Bartuszevige, A.M., and B.A. Endress. 2008. Do ungulates facilitate native and exotic plant spread? Journal of Arid Environments 72(6):904-913. Bartuszevige, A.M., Kennedy, P.L., and R.V. Taylor. 2012. Sixty-seven years of landscape change in the last, large remnant of the Pacific Northwest Bunchgrass Prairie. Natural Areas Journal 32(2):166-170. Belsky, A.J. 1992. Effects of grazing, competition, disturbance and fire on species composition and diversity in grassland communities. Journal of Vegetation Science 3(2):187-200. Black, A.E., Strand, E., Wright, G.R., Scott, M.J., Morgan, P., and C. Watson. 1998. Land use history at multiple scales: implications for conservation planning. Landscape and Urban Planning 43:49-63. Bowles, M.L., Jones, M.D., and J.L. McBride. 2003. Twenty-year changes in burned and unburned sand prairie remnants in northwestern Illinois and implications for management. The American Midland Naturalist 149(1):35-45. Bowles, M.L., and M.D. Jones. 2013. Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing late successional vegetation. Ecological Applications 23(2):464-478. Brooks, M.L., D’Antonio, C.M., Richardson, D.M., Grace, J.B., Keeley, J.E., DiTomaso, J.M., Hobbs, R.J., Pellant, M., and D. Pyke. 2004. Effects of invasive alien plants on fire regimes. BioScience 54(7):667-688. Case, M.F., and A.C. Staver. 2017. Fire prevents woody encroachment only at higher than historical frequencies in a South African savanna. Journal of Applied Ecology 54(3):955- 962. Clough, Y., Ekroos, A.B., Batary, P., Bommarco, R., Gross, N., Holzchuh, A., Hopfenmuller, S., Knop, E., Kuussaari, M., Lindborg, R., Marini, L., Öckinger, E., Potts, S., Poyry, J., Roberts, S., Steffan-Dewenter, I., and H. Smith. 2014. Density of insect-pollinated grassland plants decreases with increasing surrounding land-use intensity. Ecology Letters 17:1168-1177. Collins, S.L., and L.B. Calabrese. 2012. Effects of fire, grazing and topographic variation on vegetation structure in tallgrass prairie. Journal of Vegetation Science 23(3):563-575. 8

Corbet, S.A., Williams, I.H., and J.L. Osborne. 1992. Bees and the pollination of crops and wild flowers in the European community. Apiacta 4. DeBano, S.J., Roof, S.M., Rowland, M.M., and L.A. Smith. 2016. Diet overlap of mammalian herbivores and native bees: implications for managing co-occurring grazers and pollinators. Natural Areas Journal 36(4):458-477. Delaney, J.T., K.J. Jokela, and D.M. Debinski. 2015. Seasonal succession of pollinator floral resources in four types of grasslands. Ecosphere 6(11):243. Endress, B.A., Averett, J.P., Naylor, B.J., Morris, L.R. and R.V. Taylor. 2019. Non-native species threaten the biotic integrity of the largest remnant Pacific Northwest Bunchgrass Prairie in the United States. Applied Vegetation Science 23:53-68. Fuhlendorf, S.D., Zhang, H., Tunnell, T.R., Engle, D.M., and A.F. Cross. 2002. Effects of grazing on restoration of southern mixed prairies. Restoration Ecology 10(2):401-407. Fynn, R.W.S., Morris, C.D., and T.J. Edwards. 2009. Effect of burning and mowing on grass and forb diversity in a long-term grassland experiment. Applied Vegetation Science 7(1):1- 10. Gathmann, A., and T. Tscharntke. 2002. Foraging ranges of solitary bees. Journal of Animal Ecology 71(5):757-764. Gibson, D.J. 2009. Grasses and Grassland Ecology. Oxford University Press, NY.

Harrison, S., Inouye, B.D., and H.D. Safford. 2003. Ecological heterogeneity in the effects of grazing and fire on grassland diversity. Conservation Biology 17(3):837-845. Huang, Y., Wang, K., Deng, B., Sun, X., and D-H. Zeng. 2015. Effects of fire and grazing on above-ground biomass and species diversity in recovering grasslands in northeast China. Journal of Vegetation Science 00:1-11. Johnson, R.L. 2008. Impacts of habitat alterations and predispersal seed predation on the reproductive success of Great Basin forbs. Dissertation. Brigham Young University. Kauffman, J.B., Sapsis, D.B., and K.M. Till. 1997. Ecological studies of fire in sagebrush/bunchgrass ecosystems of the John Day Fossil Beds National Park, Oregon: implications for the use of prescribed burning to maintain natural ecosystems. Washington, DC: National Park Service, Columbia Cascades System Support Office. Kearns, C.A., and D.M. Oliveras. 2009. Environmental factors affecting bee diversity in urban and remote grassland plots in Boulder, Colorado. Journal of Insect Conservation 13(1):655-665. Kimoto, C., DeBano, S.J., Thorp, R.W., Taylor, R.V., Schmalz, H.J., DelCurto, T., Johnson, T., Kennedy, P.L., and S. Rao. 2012. Short-term responses of native bees to livestock and implications for managing ecosystem services in grasslands. Ecosphere 3(10):88. 9

Klein, A.M., Vaissiere, B.E., Cane, J.H., Steffan-Dewenter, I., Cunningham, S.A., Kremen, C., and T. Tscharntke. 2007. Importance of pollinators in changing landscapes for world crops. Proceedings of the Royal Society 274:303-313. Kwaiser, K.S., and S.D. Hendrix. 2008. Diversity and abundance of bees (Hymenoptera: Apiformes) in native and ruderal grasslands of agriculturally dominated landscapes. Ecosystems and Environment 124:200-204. Lovell, D.L., Henderson, R.A. and E.A. Howell. 1982. The response of forb species to seasonal timing of prescribed burns in remnant Wisconsin prairies. In Proceedings of the Eighth North American Prairie Conference. Western Michigan University Press, Kalamazoo, 11-15. Mallinger, R.E., Gibbs, J., and C. Gratton. 2016. Diverse landscapes have a higher abundance and species richness of spring wild bees by providing complementary floral resources over bees’ foraging periods. Landscape Ecology 31(7):1523-1535. Masunga, G.S., Moe, S.R., and B. Pelekekae. 2012. Fire and grazing change herbaceous species composition and reduce beta diversity in the Kalahari sand system. Ecosystems 16:252- 268. Morgan, P., Heyerdahl, E.K., Strand, E., Bunting, S.C., Riser II, J.P., Abatzoglou, J.T., Nielsen- Pincus, M., and M. Johnson. 2020. Fire and land cover change in the Palouse Prairie- forest ecotone, Washington. Fire Ecology 16:2-19 Morris, L.R., Monaco, T.A., and R.L. Sheley. 2011. Land-use legacies and vegetation recovery 90 years after cultivation in Great Basin sagebrush ecosystems. Rangeland Ecology and Management 64(5):488-497. Morris, L.R., Monaco, T.A., and R.L. Sheley. 2014. Impact of cultivation legacies on rehabilitation seedings and native species re-establishment in Great Basin shrublands. Rangeland Ecology and Management 67(3):285-291. Nelson, J.K. 1997. Natural succession impeded by smooth brome (Bromus inermis) and intermediate wheatgrass (Agropyron intermedium) in an abandoned agricultural field. EG and G Rocky Flats, Inc., Golden, CO, US Rocky Flats Plant. Öckinger, E., and H.G. Smith. 2007. Semi-natural grasslands as population sources for pollinating insects in agricultural landscapes. Journal of Applied Ecology 44:50-59. Olff, H., and M.E. Ritchie. 1998. Effects of herbivores on grassland plant diversity. Trends in Ecology and Evolution 13(7):261-265. Pechanec, J.F., Stewart, G., and J.P. Blaisdell. 1954. Sagebrush burning: good and bad (No. 1948). US Department of Agriculture. Pollak, O., and T. Kan. 1998. The use of prescribed fire to control invasive exotic weeds at Jepson Prairie Preserve. In Ecology, Conservation, and Management of Vernal Pool 10

Ecosystems–Proceedings from a 1996 Conference. California Native Plant Society, Sacramento, CA 241-249. Potts, S.G., Vulliamy, B., Dani, A., Ne’eman, G., O’Toole, C., Roberts, S., and P. Willmer. 2003. Response of plant-pollinator communities to fire: changes in diversity, abundance and floral reward structure. Oikos 101(1):103-112. Potts, S.G., Woodcock, B.A., Roberts, S.P.M., Tscheulin, T., Pilgrim, E.S., Brown, V.K., and J.R. Tallowin. 2009. Enhancing pollinator biodiversity in intensive grasslands. Journal of Applied Ecology 46:369-379. Potts, S.G., Biesmeijer, J.C., Kremen, C., Neumann, P., Schweiger, O., and W.E. Kunin. 2010. Global pollinator declines: trends, impacts and drivers. Trends in Ecology and Evolution 25(6):345-353. Ridder, L.W. 2019. The response of Ventenata dubia to prescribed fire and ungulate grazing on the Pacific Northwest Bunchgrass Prairie. Master’s Thesis, Oregon State University. Robson, D.B. 2019. Impact of grazing history on pollinator communities in Fescue prairie. Blue Jay 77(1):10-15. Roof, S.M., DeBano, S.J., Rowland, M.M., and S. Burrows. 2018. Associations between blooming plants and their bee visitors in a riparian ecosystem in Eastern Oregon. Northwest Science 92(2):119-135. Ruthven, D.C., Gallagher, J.F., and Syantzske, D.R. 2000. Effect of fire and grazing on forbs in the western south Texas plains. The Southwestern Naturalist 45(2):89-94. Schmalz, H.J., Taylor, R.V., Johnson, T.N., Kennedy, P.L., DeBano, S.J., Newingham, B.A., and P.A. McDaniel. 2013. Soil morphologic properties and cattle stocking rate affect dynamic soil properties. Rangeland Ecology and Management 66(4):445-453. Spasojevic, M.J., Aicher, R.J., Koch, G.R., Marquardt, E.S., Mirotchnick, N., Troxler, T.G., and S.L. Collins. 2010. Fire and grazing in a mesic tallgrass prairie: impacts on plant species and functional traits. Ecology 91(6):1651-1659. Steffan-Dewenter, I., Potts, S.G., and L. Packer. 2005. Pollinator diversity and crop pollination services are at risk. Trends in Ecology and Evolution 20(12):651-652. Taylor, R.V., and H.J. Schmalz. 2012. Monitoring of upland prairie vegetation on the Zumwalt Prairie Preserve 2003-2011. The Nature Conservancy, Enterprise, OR. Taylor, R.V., Pokorny, M.L., Mangold, J., and N. Rudd. 2013. Can a combination of grazing, herbicides, and seeding facilitate succession in old fields? Ecological Restoration 31(2):141-143. Tisdale, E.W. 1982. Grasslands of western North American: The Pacific Northwest Bunchgrass. In: Nicholson A.C., McLean A., Baker T.E., Editors. Proceedings of the 1982 Grassland Ecology and Classification Symposium. 232-245. Information Services Branch, British Columbia Ministry of Forests. 11

Traveset, A., and D.M. Richardson. 2006. Biological invasions as disruptors of plant reproductive mutualisms. Trends in Ecology and Evolution 21(4):208-216. Wallace, J.M. and T.S. Prather. 2016. Herbicide control strategies for Ventenata dubia in the Intermountain Pacific Northwest. Invasive Plant Science and Management 9:128-137. Wrobleski, D.W., and J.B. Kauffman. 2003. Initial effects of prescribed fire on morphology, abundance, and phenology of forbs in big sagebrush communities in southeastern Oregon. Restoration Ecology 11(1):82-90. Zimmer, H.C., Turner, V.B., Mavromihalis, J., Dorrough, J., and C. Moxham. 2010. Forb responses to grazing and rest management in a critically endangered Australian native grassland ecosystem. The Rangeland Journal 32(2):187-195.

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Chapter 2: Forb Community Response to Prescribed Fire, Livestock Grazing, and Invasive Species in the Pacific Northwest Bunchgrass Prairie

Brogan L. Watson, Lesley R. Morris, Scott B. Lukas, Sandra J. DeBano, Heidi J. Schmalz, and A. Joshua Leffler

Abstract There is growing concern about the observed global decline in native pollinator populations. Habitat degradation and fragmentation of grasslands due to agricultural development, changing fire regimes, and invasive species are believed to be primary contributors to these pollinator losses. These disturbances impact pollinators because they affect the forb communities. Abundance and richness of native bees, for example, have been directly linked to the abundance and richness of the floral resources available in their habitat. The complex relationships between fire and livestock grazing with forb communities have been well studied in other grassland systems but not in the Pacific Northwest Bunchgrass Prairie (PNB). The objectives of this study were to determine: 1) how prescribed fire and livestock grazing treatments (individually and together) influence forb community composition, cover, species richness, and diversity through time (2008, 2010, 2016, and 2018); 2) what the different indicator species are for each treatment; and 3) how forb cover, richness, and diversity changed over time in relation to the increasing cover of Ventenata dubia. To address these objectives, we used plant community monitoring data from a manipulative study with four treatments, prescribed fire, livestock grazing, both prescribed fire and grazing, and no fire or grazing (as a control), that were established in 2004 with fall burns implemented in 2006 and 2016. We found that forb communities changed significantly over ten years and were more influenced by prescribed fire than livestock grazing alone. Sites that had been burned or both grazed and burned were associated with more annual forb species while grazed only and control sites were associated with more perennial species. Although forb cover was lower in grazed treatments than burned or control, there were no differences in forb richness and diversity between treatments. Indicator species analysis also pointed to the importance of fire on maintaining fire-adapted forbs like aspen fleabane (Erigeron speciosus), pleated gentian (Gentiana affinis), and small camas (Camassia quamash). There was a significant negative correlation between increasing V. dubia cover and forb cover and richness 13 in 2016 and 2018 when the invasive species reached 20-37% cover, suggesting a threshold had been crossed. Our results suggest that fall prescribed burns at a ten-year return interval do not change overall forb richness or diversity but may help to promote fire tolerant species. This study provides additional insight to aid in the conservation of the forb communities for native pollinators and emphasizes the need for continued monitoring of the invasion of V. dubia in this unique remnant prairie.

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2.1 Introduction

There is growing concern about the observed decline in native pollinators, particularly bees, worldwide (Potts et al. 2003; Potts et al. 2009; DeBano et al. 2016). The decline in pollinator abundance has been linked to habitat disruption and degradation (Potts et al. 2010; Roof et al. 2018), range reduction (Moisset and Buchmann 2010), increased use of pesticides (Black et al. 2011), agricultural development (Steffan-Dewenter et al. 2005; Moisset and Buchmann 2010), crop production and intensification (Potts et al. 2010; Clough et al. 2014), urban expansion, climate change, and invasive plant species (Black et al. 2011). Grasslands are critical to the conservation of pollinators (Öckinger and Smith 2007). Connections between the causes for declining pollinators and the status of grasslands means significant research has focused on these threatened ecosystems (Klein et al. 2007; Potts et al. 2009; Woodcock et al. 2014).

Native grasslands are species-rich with abundant flowering plants that are crucial for supporting highly diverse and sustainable pollinator populations (Ebeling et al. 2008), which in turn are vital for the reproductive success of the plant community (Black et al. 2011). Larger remnants of native grasslands retain more of the native species composition compared to smaller and fragmented remnant prairie sites (Alstad et al. 2016) and can support more native bees which are dependent on floral resources (Klein et al. 2007; Öckinger and Smith 2007; Potts et al. 2009; Kimoto et al. 2012b; Woodcock et al. 2014). Disturbance effects on native bee habitat can also depend on the species of bee (Kimoto et al. 2012b) but abundance, richness, and diversity of floral resources tracks well with these characteristics in pollinators in a number of habitats (Potts et al. 2003). Therefore, developing a better understanding of changes in composition, abundance, richness, and forb communities is an important indicator for native pollinator conservation (Clough et al. 2014) in relation to disturbances that are an essential part of grassland functions around the world (Gibson 2009).

Fire and herbivory are common natural and anthropogenic disturbances in grasslands worldwide (Bowles et al. 2003; Potts et al. 2003; Harrison et al. 2003; Bowles and Jones 2013; Huang et al. 2015). Prescribed fire is widely used as an effective management tool for suppressing woody species encroachment (Case and Staver 2017) and controlling invasive species (Pollak and Kan 1998; Case and Staver 2017) that can displace native grasses and forbs (Thomas and Gamón 1995). However, fire can have complicated impacts on grasslands and forb 15 communities depending upon the timing, intensity, and severity of the burn (Lovell et al. 1982; Spasojevic et al. 2010; Collins and Calabrese 2012; Bowles and Jones 2013). While more research has focused on graminoids (Lovell et al. 1982), prescribed fire has been used to stimulate forb germination (Ruthven et al. 2000; Harrison et al. 2003), extend active growth periods (Wrobleski and Kauffman 2003), and can increase blooms of annual floral resources, especially within the first year (Potts et al. 2003), and increase forb diversity (Ruthven et al. 2000; Bowles and Jones 2013). Furthermore, fire creates more bare ground, which increases soil moisture, nutrients, and available light allowing annual forbs to establish into open sites (Kauffman et al. 1997). Some forb species that reproduce from belowground organs have the advantage of being more adapted to fire and can respond quickly and favorably post-fire (Pechanec et al. 1954). Some common grassland forbs, like those in the genus Erigeron, thrive after fire and are known as indicators of this disturbance in North American grasslands (Howe 1994; Gucker and Shaw 2019). Finally, changes in canopy structure created by fire can reduce competition from overstory vegetation resulting in increased seed production, germination, and greater numbers of inflorescences (Wrobleski and Kauffman 2003).

Grasslands provide an important economic resource for the livestock industry worldwide, and habitat for native ungulates such as bison (Bison bison) (Hartnett et al. 1996) and elk (Cervus canadensis). Like fire, the relationship between cattle grazing and forbs can be complex. Grazing can inhibit forb abundance in semi-arid systems (Masunga et al. 2012), give them an advantage by reducing competition by graminoids (Ruthven et al. 2000), and even increase forb richness (Harnett et al. 1996; Harrison et al. 2003). Unlike grasses that possess basal meristems (growth points), forbs possess apical meristems that are more vulnerable to grazing. If removed by grazing, the loss of these meristems can inhibit flowering (Fynn et al. 2004) such that grazing areas during peak bloom abundance can result in inadequate pollinator forage (Black et al. 2011). The effects of both fire and herbivory have been studied in a variety of grassland systems around the world including Africa (Masunga et al. 2012), China (Huang et al. 2015), England, tall-grass prairie (Hartnett et al. 1996), vernal pools (Kamansky 2008), and coastal grasslands in the U.S. (Hatch et al. 1999). The interactions between these two disturbances, however, are far less studied (Vinton et al. 1993; Ridder 2019), especially on the Pacific Northwest Bunchgrass Prairie (PNB) in the U.S. 16

Though often useful for invasive species control, prescribed fire and grazing reportedly h very little, if any, impact on Ventenata dubia (Ridder 2019). Ventenata dubia, a relatively new invasive annual grass introduced in 1950’s in the U.S., has rapidly invaded the Pacific Northwest (Wolff 2013). It is now well established in perennial grass systems (Averett et al. 2020), forests (Kerns et al. 2020), and shrublands (Jones et al. 2016), all with varying disturbance regimes (Wallace et al. 2015). Scant literature available on this grass species leaves many gaps in the knowledge of its invasion potential and especially its impacts on native vegetation (Averett et al. 2020; McKay et al. 2017). Jones et al. (2016) identified a correlation between high V. dubia cover and a decrease in native plant community richness and evenness. However, in areas where V. dubia was present, the most abundant native species correlated with its establishment were annual forbs (Jones et al. 2016). Ventenata dubia is now the fourth most abundant species in a remnant preserve of the PNB, and Averett et al. (2020) reported a decrease in forb cover with increasing cover of V. dubia, but did not examine the response in species richness or diversity.

The PNB is considered the most threatened and understudied temperate grassland in North America, which once stretched from the northwestern U.S. into Canada (Tisdale 1982). Recently, more research has included the history of settlement and land-use changes (Bartuszevige et al. 2012), along with impacts of livestock grazing on birds (Kennedy et al. 2009) and native bees under different stocking rates (Johnson et al. 2011), distribution of invasive species (Endress et al. 2019), changes in plant communities (Averett et al. 2020), and the interaction between prescribed fire and grazing on the spread of V. dubia (Ridder 2019). However, there is no research addressing prescribed fire and grazing, nor their interaction and impacts on the forb community in this unique grassland. In this study, we examined how the forb community responded to prescribed fires, livestock grazing, and invasive species using monitoring data starting in 2008 on a long-term study established in 2004 (Johnson et al. 2011). The overarching objective was to determine how land management treatments (prescribed fire, livestock grazing, both prescribed fire and grazing, and no prescribed fire or livestock grazing) influence the change in forb community.

Specifically, we asked the following questions: 1) how do prescribed fire and livestock grazing treatments (individually and together) influence forb community composition, cover, species richness, and diversity through time (2008, 2010, 2016, and 2018); 2) what are the 17 different indicator forb species for each treatment; and 3) how has forb cover, richness, and diversity changed over time in relation to the increasing cover of V. dubia? On the basis of prior studies, we expected forb species richness to increase as a response to livestock grazing (Harnett et al. 1996; Harrison et al. 2003) and forb diversity to positively respond to prescribed fire (Ruthven et al. 2000; Bowles and Jones 2013). We expected sites with multiple disturbances (burned and grazed) would contain lower species richness and diversity than less disturbed sites (grazing alone and control) (Huang et al. 2015). In burned sites, we expected to find more annual forb species, as they are often the first to germinate after disturbance (Potts et al. 2003) and species that are known to thrive with fire, like Erigeron spp. (Howe 1994; Gucker and Shaw 2019). Finally, we expected forb cover, richness, and diversity to decline in relation to the increasing cover of V. dubia over the last decade, since cover has been observed to decline with the exotic grass on the PNB previously (Averett et al. 2020).

2.2 Methods

Study Area

The study area was located in Wallowa County in northeastern Oregon, U.S. (45° 34’N, 116° 58’W) on the Zumwalt Prairie Preserve (ZPP), owned and managed by The Nature Conservancy (TNC). The ZPP stretches across 13,300 ha and is the largest intact remnant of the historical PNB. The PNB once spanned 8,000,000 ha throughout the northwestern U.S. and parts of Canada and is now considered one of the most understudied and threatened ecosystems in North America (Tisdale 1982). Elevation on the ZPP ranges from 1060 to 1680 m (Bartuszevige et al. 2012), with rolling hills (7% slopes on average) (Damiran et al. 2007), and deep canyons incised by tributaries of the Grande Ronde and Imnaha rivers (Bartuszevige et al. 2012; Endress et al. 2019). Average annual precipitation is 34.9 cm (Taylor 2016) and average monthly temperatures range from -3°C in January to 17°C in July (Schmalz et al. 2013). For interpretation, we collected mean monthly precipitation data for each year of sampling (2008, 2010, 2016, and 2018) from the ZPP weather station, located at the center of the preserve (Kimoto et al. 2012a), which records daily precipitation (cm), minimum, maximum, and mean temperature, along with wind speed and relative humidity (Taylor 2016). 18

Historically, the Zumwalt Prairie was grazed by horses (Equus caballus) and cattle (Bos taurus) belonging to indigenous people (Bartuszevige et al. 2012), including the Nez Perce tribe during the late 1700s (Endress et al. 2019). The arrival and settlement of Euro-Americans in the late 1800s brought changes to the prairie in the form of larger herds of cattle, sheep, and horses, and cultivation associated with homesteading (Bartuszevige et al. 2012). Large concentrations of grazing ungulates were a new disturbance to the PNB because the prairie vegetation did not evolve with intense grazing pressure like other grasslands in the U.S. (Mancuso and Mosley 1994). Settlement likely brought additional changes to prairie system functions, such as alterations in the fire regime due to suppression efforts. The large herds that accompanied settlers likely consumed herbaceous vegetation (Bartuszevige et al. 2012), which would decrease fine fuels for carrying fire and increase the fire return interval. Although the ZPP is lacking a complete fire record, these grassland communities likely burned every 10-20 years based on climate and fuel conditions (Black et al. 1998; Bartuszevige et al. 2012; Morgan et al 2020). Currently, the Zumwalt Prairie is primarily utilized for beef cattle production (Bartuszevige et al. 2012). The grazing season on the ZPP begins in late May and is completed by mid-October using a rotational grazing system (TNC unpublished data). The grazed plots in this study (graze and both) have been consistently stocked at a moderate rate (0.28 – 0.4 AUM/acre) by TNC, as is the common practice in most of the Zumwalt Prairie (Mitchell 2020).

Soils across the Zumwalt Prairie have formed on basalt bedrock with more recent deposition of loess and colluvium (Schmalz et al. 2013) and are predominately classified as Xerolls (Bartuszevige et al. 2012; Schmalz et al. 2013). Plant communities are dominated mainly by bunchgrass species including Idaho fescue (Festuca idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda) and prairie Junegrass (Koeleria macrantha) (Kennedy et al. 2009; Kimoto et al. 2012a). The forb community is also highly diverse with over 112 species present (Kimoto et al. 2012a), including dominant species of twinleaf arnica (Arnica sororia), western yarrow (Achillea millefolium), slender cinquefoil (Potentilla gracilis), prairie smoke (Geum triflorum) and several lupine species (Lupinus sp.) (Damiran et al. 2007). The ZPP supports a large population of Spalding’s catchfly (Silene spaldingii) (Taylor et al. 2012), listed and protected under the U.S. Endangered Species Act (USFWS 2007), making this important habitat for conservation (Bartuszevige et al. 2012). 19

Nomenclature for the plant species in this study follows the United States Department of Agriculture (USDA) Plants Database.

Experimental Design

The Nature Conservancy established a prescribed fire and grazing study in 2004, which used a randomized complete block design with four treatments and four sites (blocks). Treatments consisted of prescribed fire (burn), livestock grazing (graze), both prescribed fire and grazing (both), and no prescribed fire or livestock grazing (control). The control treatments have not been grazed since 2004, except by wild ungulates, mainly elk. Prescribed burns were conducted in the fall of 2006 and 2016. Burn severity was assessed after the prescribed fire in 2016 and never reached the highest intensity category, heavily burned (Movich and Schmalz 2016).

Vegetation monitoring was initiated by employees of TNC in 2008 on all sixteen plots (Figure 2.1; four treatments replicated four times) using a layout of six parallel transects that were 100 m in length, spaced 50 m apart, spanning a 300 m baseline (Taylor and Schmalz 2012). Foliar cover for all species were recorded using a line-point intercept reading every three meters (Canfield 1941). The sampling protocol was redesigned in 2010 to nine parallel 50 m transects, spaced 30 m apart along a 300 m baseline, with a 25 m buffer on both ends of the transects (Figure 2.2). Foliar cover in 2010 for all species was again recorded with the line-point intercept (Canfield 1941), but at every meter along each transect. Since foliar cover includes all species from canopy to soil surface, cover can be recorded as over 100% (Canfield 1941).

The monitoring protocol from 2010 was used to resurvey foliar cover of all species in 2016 and 2018 on all 16 plots. Plots were located with a GPS unit (See A.2 for coordinates). For this study, only data for total forb cover and V. dubia was used. Forb richness represents the number of species in a particular area (Gotelli and Colwell 2011), which does not account for the number of individuals of each species present. Therefore a species diversity index (H’) for each ′ site was calculated using Shannon -Wiener’s index (H = − ∑ (푝푖 × ln 푝푖)), where p is the relative abundance of species i (Collins and Calabrese 2012).

Statistical Analysis

To evaluate changes in forb species composition from 2008, 2010, 2016 and 2018, we used Non- metric Multidimensional Scaling (NMS) with R i368 3.6.1 statistical software’s vegan package 20 and the metaMDS function (R Core Team 2019). A permutational multivariate analysis of variance (perMANOVA) using the Bray-Curtis similarity metric was used in order to assess differences in forb community composition resulting from main effects (treatment and year) and the interaction term, using the adonis function. To account for repeated-measures, we used linear mixed-effects modeling in R’s lme4 package, to compare differences in forb cover, species richness, and species diversity over time. Treatments were used as fixed effects with blocks designated as random effects. The emmeans package and pairs function, were used to evaluate pairwise comparisons of forb cover (%) between treatment types.

Indicator Species Analysis (ISA) were completed in PC-ORD software version 7.08 (McCune and Mefford 2016) with a Monte Carlo test to determine a species’ faithfulness to a specific group (McCune and Grace 2002) based on the abundance. The ISA tests produce indicator values (IV) that represent the strength of affinities for a particular species within a predetermined group. A higher IV (0 – 100) indicates stronger association within a group and IV significance is determined by comparing results from randomizations to observed values (McCune and Mefford 2016). Simple linear regressions were run with all sampling years together and for of each year separately using R to determine changes in forb species cover, richness, and diversity in response to a continuous increase in V. dubia cover since 2008. Data of both forb cover and V. dubia cover (percent) were arcsine square root transformed to reduce skewness and enhance the normality of the data, as is common with biological data (Stohlgren 2007).

2.3 Results

The on-site weather station recorded a 14-year mean monthly precipitation of 3.00 cm and revealed that only one sampling year (2008; 2.49 cm) was below the mean while 2010 (3.77 cm), 2016 (3.22 cm), and 2018 (3.13 cm) were all above the mean. All years displayed a typical bimodal peak precipitation occurrence in spring and fall (Figure 2.3).

Forb Compositional Changes

Forb community composition differed among sites from 2008 to 2018 (Figure 2.4). Approximately 80% of the variation in forb community composition was explained by axis 1 (R2 = 0.53) and axis 2 (R2 = 0.30) in the 2-dimensional NMS ordination. The ordination in forb 21 species space showed differences in forb community composition among years and treatments, with species composition in 2008 being the most dissimilar and separated from 2010, 2016, and 2018. Forb community composition in 2016 and 2018 were the most similar and 2008 and 2018 were the least similar. Control and graze treatment mean ellipses overlap as do burn and both treatment ellipses. However, the two treatments (control and graze) are dissimilar from the other two treatments (both and burn). Similar to the ordination, species composition was significantly affected by year (p = 0.001) and treatment (p = 0.002), however there was not an interaction effect (p = 0.687) on forb community composition (Table 2.1).

Forb Cover, Richness, and Diversity

Forb cover was significantly different by year (p < 0.001) and treatment (p = 0.017), but no interaction effect was found (p = 0.969) (Table 2.2). Similarly, there was a significant year effect on forb species richness (p = 0.024), but no effect of treatment on richness (p = 0.836) or diversity (p = 0.163) (Table 2.2 and Table 2.3). Forb cover in the burned treatments (39% + 4.1) was significantly higher (p = 0.030) than in grazed (27% + 3.3) treatments. Forb cover in the control (39% + 3.9) treatments were also significantly higher (p = 0.039) than the grazed (27% + 3.3) treatments (Figure 2.5; Table 2.3).

Indicator Analysis for Treatments

Indicator Species Analysis revealed significant species affinities for each treatment, with control sites having more species associated than the other three treatments. Many species had indicator values for all four treatments except five forbs which only had indicator values for one treatment. The species Buglossoides arvensis was exclusive to the control treatment, Camassia quamash exclusive to both, Draba verna in graze, and Erigeron speciosus only having an indicator value in the burn treatment (Table 2.4).

Forb Response to Increasing Ventenata dubia

Lastly, there were no significant correlations between the increase in V. dubia and forb cover, species richness, or diversity with all years combined. Likewise there was no relationship between increasing V. dubia and forb cover in 2008 or 2010 (Table 2.5). However, we did find a significant decrease in forb cover in 2016 and 2018 (Figures 2.6 and 2.7). Similarly, in 2018, there was a significant decrease in forb species richness (Figure 2.8) with increasing V. dubia. 22

There were no significant relationships between forb diversity and V. dubia cover in any sampling year (Table 2.5).

2.4 Discussion

Forb Compositional Changes

Our study demonstrates that forb community composition responds differently to the effects of prescribed fire and livestock grazing, but not necessarily to their interaction over a span of ten years. In fact, our findings indicate that prescribed fire every ten years and prescribed fire with livestock grazing, more than livestock grazing alone, had more influence in structuring forb communities. Forb communities of burned and both burned and grazed plots were similar, while communities within grazed only and control plots were similar. These findings suggest that prescribed fire had a greater impact on the forb community than moderate grazing in this grassland system. Our results support previous work in grasslands reporting fire has stronger and more persistent effects on grassland composition and structure than moderate levels of grazing bison in the Konza Prairie (Spasojevic et al. 2010) and grasslands in Israel (Noy-Meir 1995).

The separation between forb communities with lesser-disturbed sites (control and graze) and higher disturbed sites (burn and both) can be interpreted by the species associated with each axis in our ordination (Figure 2.4). More annual forb species (Veronica arvensis, Draba verna, Microsteris gracilis, Phlox longifolia, and Myosotis stricta) were found on higher disturbance sites, whereas lesser disturbed sites had more perennial forbs (Geum triflorum, Geranium viscosissimum, Potentilla gracilis, Galium boreale and Rosa sp.) (Figure 2.4). These results suggest treatments involving fire (burn and both) can promote annual forbs that recover quickly like others have reported when fire and grazing are combined (Noy-Meir et al. 1989; Belsky 1992; Potts et al. 2003; Kahmen and Poschlod 2008; Spasojevic et al. 2010). Likewise, no to moderate grazing without fire may promote conditions that favor perennial forbs and woody species (Rosa sp.) (Figure 2.4) as has been reported in other grassland systems (Gibson and Hulbert 1987; Potts et al. 2003; Spasojevic et al. 2010; Mavromihalis et al. 2013).

Our results also show there were differences in forb community composition over time, especially between 2008 and the other sampling years. A factor that can influence the differences in community composition is the amount of precipitation received in the spring before sampling 23 occurred. Although we did not test any climate variables in this study, lower than mean monthly precipitation between January (1.95 cm), February (1.09 cm), March (2.20 cm), and April (2.76 cm) of 2008 could help explain why study sites in 2008 separated from sites sampled in all other years. Furthermore, a peak in precipitation during May (6.35 cm) and June (12.02 cm) of 2010 could have influenced separation between 2008 and 2010 in the ordination space (Figure 2.4). An alternative explanation could be the lack of fully identified species in 2008.

Forb Cover, Richness, Diversity

Grazed treatments in our study had significantly lower forb cover than burned and control treatments. Although ungulates prefer and primarily consume graminoid species, a portion (7.5 %) of their diet also includes forbs (Clark et al. 2009; Vinton et al. 1993). It is possible this difference is due to consumption or trampling by livestock. However, the diminutive introduced annual D. verna, an indicator of grazed treatments discussed below, could lead to lower forb cover as well. Even with lower forb cover, there may not be any negative impact on pollinators since a recent study found cattle grazing had no negative long-term effects on plant or bee communities in these plots (Mitchell 2020). Higher forb cover on burned prairie may be caused by the removal of litter. Fire consumes the majority of aboveground biomass in ungrazed areas and less so in areas where grazing occurred, opening sites for forb establishment and growth (Noy-Meir 1995).

Interestingly, we did not find any differences in forb richness or diversity in our sites. Forb species richness and diversity has been shown to increase as a response to prescribed fire (Ruthven et al. 2000; Bowles and Jones 2013). Others have found no differences in the interaction between fire and grazing on total species diversity (Noy-Meir 1995) and in the short- term following a fire (Ruthven et al. 2000). It is unclear how this result may change with the entire flora included (e.g., graminoids) and with shorter fire-return intervals. Our results can only be applied to a fall prescribed burn at a ten-year fire return interval. Results may vary if prescribed fire is applied more frequently, occurs at a higher intensity, or is applied in the spring. Therefore, if the management goal is to increase forb richness or diversity, further research would need to include different fire-return intervals and seasonal timing.

Indicator Species for Treatments 24

The indicator species analysis by treatment also revealed interesting patterns (Table 2.4). Buglossoides arvensis (previously known as Lithospermum arvense) was the only indicator species exclusive to the control treatment. This introduced species is an arable weed that followed crop production of cereal grains in the U.S. and South America (Chantre et al. 2009a). It is a winter annual forb, a characteristic reported to give it a competitive advantage to spread into non – tilled sites (Chantre et al. 2009b). It is very likely this species was also introduced to the PNB and onto the Zumwalt Prairie during the agricultural expansion of cereal grains in this region (Bartuszevige et al. 2012). Ironically, it is now considered a species of concern in Europe and is the focus of conservation efforts (Peters and Gerowitt 2014). The grazing treatment had only one significant indicator species associated with it, D. verna, a small non-native annual forb that can asexually reproduce when stressed (Jordan and Koch 2008) and whose small seed size favors persistence in the soil seed banks (Thompson 1987; Thompson et al. 1993), even with severe and prolonged disturbance (Franzese et al. 2016). Since only one species was associated to the grazing treatment, it could indicate dietary overlap occurred at peak blooming periods between pollinators and ungulates (DeBano et al. 2016), when the consumption of floral resources inhibited flower production during the growing season.

The forb species, C. quamash, was an important indicator in sites that were burned and grazed. Species like C. quamash, have the potential to regenerate after fire from underground storage organs (Spasojevic et al. 2010), that are not harmed in low intensity grassland fires. Burning grasslands can create optimal environments for the growth, production (Stevens et al. 2001; USDA 2006), and increase the abundance of C. quamash (Thomas and Gamón 1995). Additionally, this species is one of the most important root food sources for western indigenous peoples, like the Nez Perce (Stevens et al. 2001). Indicator species for prescribed fire only included E. speciosus, Frasera albicaulis and Gentiana affinis (Table 2.4). Erigeron speciosus stands out as an indicator of burned sites because other reports about this species, and others within the genus Erigeron, show it responds positively to fire (Towne and Owensby 1984) and decreases when grazed (Howe 1994; Gucker and Shaw 2019). Frasera albicaulis, another indicator of the burn treatment and possesses a long taproot which may give it a better opportunity to withstand, benefit, and recover from prescribed burns (Lamont and Downes 2011; He et al. 2016; Pausas et al. 2018). The root of F. ablicaulis is known to have medicinal properties (Card 1931). Given that G. affinis is associated with a fire-maintained treatment, it is 25 reasonable to assume it is fire-adapted, although no published research was identified regarding fire effects on G. affinis.

Forb Response to Increasing Ventenata dubia

Forb cover decreased over time in response to the increasing cover of V. dubia. This supports the findings of Averett et al. (2020) who also reported a decrease in native perennial forb cover from 2008 to 2016 on the PNB. Unlike Averett et al. (2020), our study included treatments, had more than two sampling years, and examined V. dubia cover in relation to the richness and diversity of forb species. The ten-year time frame in our study shows the negative correlation of forb cover with V. dubia does not become significant until 2016 and 2018, suggesting that a potential threshold may have been crossed in these years once V. dubia reached 20 - 37% cover. Likewise, the response of forb species richness to the increase in V. dubia cover was only significant in 2018, suggesting its impact on richness may also have met a threshold. However, there were no significant correlations between V. dubia cover and forb diversity even at 37% cover, suggesting the threshold for impacting diversity may be higher and more monitoring is needed to detect a potential relationship. Since a significant negative correlation does not appear until 2016 for forb cover and 2018 for forb richness, a threshold in V. dubia cover may have been crossed by/before 2016 and 2018, respectively. However, to greater describe the threshold value, more monitoring is necessary.

It is important to note that cover of each forb species may not necessarily be declining with increased V. dubia. For example, G. triflorum, has reportedly increased in abundance across the prairie (Averett et al. 2020). Similarly, results from our ordination analyses show G. triflorum potentially increased since sampling began in 2008. It is interesting to note that like the common invasive species, B. arvensis, V. dubia is also considered rare in its native habitat and is a focus for conservation (Alomran et al. 2019).

Study Limitations and Future Research

This is the first study of its kind to examine how prescribed fire, livestock grazing, and the newest threatening invasive species, V. dubia, individually and in concert, impact forb communities on the PNB. Both the temporal depth (multiple surveys over 10 years) and the comprehensive floristic sampling associated with the monitoring of these prescribed fire and 26 grazing study sites provide a unique amount of inference to the understanding of these disturbances. However, there are some limitations that should be noted and may be addressed in future research. As mentioned above, our results only apply to fall prescribed burns at a ten-year return interval. Prescribed fire in different seasons, with higher return intervals, or higher intensity may result in different forb communities and changes in forb richness and diversity not predicted by our study. More research could address these differences. In addition, grazing pressure has been moderate on the ZPP but it may be higher or lower at other sites within the PNB. Our study did not examine the forb community response with variable levels of stocking or utilization. Similar to our results, moderate grazing can even increase forb species richness (Hartnett et al. 1996; Harrison et al. 2003). However, intense grazing can reduce forb growth and reproduction (Hickman and Hartnett 2002) and complete elimination of grazing can result in the decline of forb species richness (Mavromihalis et al. 2013). Finally, this study design does not address the impacts of grazing and browsing by native ungulates in the system. The elk population has increased on the Zumwalt Prairie over time (Ridder 2019) and since TNC purchased the ZPP property in 2000 (Taylor and Arends 2012). More research is needed to understand how these wild ungulates impact the forb community composition, abundance, richness, and diversity.

2.5 Conclusion

This study is the first to demonstrate that prescribed fire in the PNB changes forb community composition more than grazing alone when compared to controlled areas. These results fit well with what is known about the importance of fire in grassland ecosystems (Lovell et al. 1982; Thomas and Gamón 1995; Harrison et al. 2003; Gibson 2009) and the moderate resistance of the PNB to grazing pressure. Our results suggest that fall prescribed fires on a ten-year return interval do not influence overall forb richness and diversity. However, fall prescribed fire, livestock grazing, and their interaction on a ten-year interval do create different forb communities with different indicator species within them. Our findings regarding forb communities as well as the forb species most likely to be correlated with each treatment can help inform management and research for conservation. There is an immediate need to increase our understanding of native pollinators, and future research is necessary to preserve forb species richness and diversity across this and other temperate grasslands for the sake of pollinators in 27 these systems (Potts et al. 2003; Klein et al. 2007; Potts et al. 2009; Potts et al. 2010; Kimoto et al. 2012a; Kimoto et al. 2012b; Clough et al. 2014). In addition to a litany of threats to grasslands from changing land uses, invasive species like V. dubia, may also be a threat to forb abundance and richness. Invasive species are also a primary threat to culturally significant plants, like C. quamash, in the few remaining remnants of the PNB (Davis 2019). Research into unique temperate grassland remnants, like the ZPP, can offer a window into what it will take to preserve the biodiversity of these grassland systems for pollinators and for people.

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Endress, B.A., Averett, J.P., Naylor, B.P., Morris, L.R. and R.V. Taylor. 2019. Non-native species threaten the biotic integrity of the largest remnant Pacific Northwest Bunchgrass Prairie in the United States. Applied Vegetation Science 23:53-68. Franzese, J., Ghermandi, L., and S.L. Gonzalez. 2016. Historical land use by domestic grazing revealed by the soil seed bank: a case study from a natural semi-arid grassland of NW Patagonia. Grass and Forage Science 71(2):315-327.

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Gucker, C.L., and N.L. Shaw. 2019. Aspen fleabane (Erigeron speciosus). In: Western forbs: Biology, ecology, and use in restoration. Reno, NV: Great Basin Fire Science Exchange. Harrison, S., Inouye, B.D., and H.D. Safford. 2003. Ecological heterogeneity in the effects of grazing and fire on grassland diversity. Conservation Biology 17(3):837-845. Hartnett, D.C., Hickman, K.R., and L.E. Fischer Walter. 1996. Effects of bison grazing, fire, and topography on floristic diversity in tallgrass prairie. Journal of Range Management 49(5):413-420. Hatch, D.A., Bartolome, J.W., Fehmi, J.S., and D.S. Hillyard. 1999. Effects of burning and grazing on a coastal California grassland. Restoration Ecology 7(4):376-381. He, T., Belcher, C.M., Lamont, B.B., and S.L. Lim. 2016. A 350 million year legacy of fire adaptation among conifers. Journal of Ecology 104(2):352-363. Hickman, K.R., and D.C. Hartnett. 2002. Effects of grazing intensity on growth, reproduction and abundance of three palatable forbs in Kansas Tallgrass Prairie. Plant Ecology 159(1):23-33. Howe, H.F. 1994. Response of early - and late - flowering plants to fire season in experimental prairies. Ecological Applications 4(1):121-133. Huang, Y., Wang, K., Deng, B., Sun, X., and D-H. Zeng. 2015. Effects of fire and grazing on above-ground biomass and species diversity in recovering grasslands in northeast China. Journal of Vegetation Science 00:1-11. Johnson, T.N., Kennedy, P.L., DelCurto, T., and R.V. Taylor. 2011. Bird community responses to cattle stocking rates in a Pacific Northwest Bunchgrass Prairie. Agriculture, Ecosystems and Environment 144(1):338-346. Jones, L.C., Norton, N., and T.S. Prather. 2016. Indicators of Ventenata (Ventenata dubia) invasion in sagebrush steppe rangelands. Invasive Plant Science and Management 11:1-9. Jordon-Thaden, I., and M. Koch. 2008. Species richness and polyploid patterns in the genus Draba (Brassicaceae): a first global perspective. Plant Ecology and Diversity 1(2):255- 263. Kahmen, S., and P. Poschlod. 2008. Effects of grassland management on plant functional trait composition. Agriculture, Ecosystems and Environment 128(3):137-145. 31

Kamansky, B. 2008. Fire and grazing effects on vernal pool grasslands. ProQuest Dissertations Publishing. Kennedy, P.L., DeBano, S.J., Bartuszevige, A.M., and A.S. Lueders. 2009. Effects of native and non-native grassland plant communities on breeding passerine birds: implications for restoration of northwest bunchgrass prairie. Restoration Ecology 17(4):515-525. Kerns, B.K., Tortorelli, C., Day, M.A., Nietupski, T., Barros, A.M.G., Kim, J.K., and M. Krawchuk. 2020. Invasive grasses: a new perfect storm for forested ecosystems? Plant Science. In Press. Kimoto, C., DeBano, S.J., Thorp, R.W., Rao, S., and W.P. Stephen. 2012a. Investigating temporal patterns of a native bee community in a remnant North American bunchgrass prairie using blue vane traps. Journal of Insect Science 12(1):108. Kimoto, C. DeBano, S.J., Thorp, R.W., Taylor, R.V., Schmalz, H., DelCurto, T., Johnson, T., Kennedy, P.L., and S. Rao. 2012b. Short-term responses of native bees to livestock and implications for managing ecosystem services in grasslands. Ecoshpere 3(10):88. Klein, A.M., Vaissiere, B.E., Cane, J.H., Steffan-Dewenter, I., Cunningham, S.A., Kremen, C., and T. Tscharntke. 2007. Importance of pollinators in changing landscapes for world crops. Proceedings of the Royal Society 274:303-313.

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Chapter 2: Figures

Figure 2.1 Map of 16 permanent plots on the Zumwalt Prairie Preserve that are part of the long- term prescribe fire and grazing study. Four treatments include burn only (BURN), grazed only (GRAZ), both burned and grazed (BOTH) and no burning or grazing since 2004 (CNTL). Numbers represent the block numbers. Hashed polygons represent areas of prescribed burn in 2006 and 2016. Map courtesy of The Nature Conservancy. 36

Figure 2.2 Plot layout for vegetation sampling in 2010, 2016, and 2018. 37

Figure 2.3 Precipitation data showing the variation in total monthly precipitation for each sampling year (2008, 2010, 2016 and 2018). Solid grey line represents mean monthly precipitation for the period of record at the weather station (2006 to 2019) located on the Zumwalt Prairie Preserve.

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Figure 2.4 Non-metric Multidimensional Scaling (NMS) results showing 2-dimensial ordination of sample units (N = 64) in forb species space for the four sampling years (2008, 2010, 2016, and 2018). The ellipses are centered around sampling year and treatment means. Four treatments include burn only (BURN), grazed only (GRAZ), both burned and grazed (BOTH) and no burning or grazing since 2004 (CNTL). Sites closer together are more similar than sites further away.

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Figure 2.5 Mean forb cover (%) +/- s.e. for each treatment. Differing letters indicate significant differences (p < 0.05).

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Figure 2.6 Relationship between foliar forb cover and V. dubia cover in 2016 (p = 0.054).

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Figure 2.7 Relationship between forb foliar cover and V. dubia cover in 2018 (p = 0.0003).

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Figure 2.8 Relationship between forb species richness and V. dubia cover in 2018 (p = 0.007).

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Chapter 2: Tables Table 2.1 Results for perMANOVA tests for year and treatment effects individually, and as an interaction, on forb species composition. Significance (p < 0.05) indicated in bold.

F P-value Treatment 2.178 0.002 Year 12.506 0.001 Treatment:Year 0.848 0.687

Table 2.2 Results for linear mixed-effects model analysis for year and treatment effects on forb species cover, richness, and diversity. Significance (p < 0.05) indicated in bold. Diversity Cover Richness (H')

DF F P-value F P-value F P-value

Treatment 3 3.699 0.017 0.284 0.836 1.775 0.163

Year 1 31.655 < 0.001 5.329 0.024 0.008 0.930

Treatment:Year 3 0.082 0.969 0.214 0.885 0.303 0.822

Table 2.3 Mean values (+ s.e.) for forb cover, species richness, and diversity by sampling year and treatment. Four treatments include: burn only (BURN), grazed only (GRAZ), both burned and grazed (BOTH) and no burning or grazing since 2004 (CNTL).

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Table 2.4 Indicator species analysis results for significant forb associations, maximum indicator values (IV) are given for each treatment. Four treatments include burn only (BURN), grazed only (GRAZ), both burned and grazed (BOTH) and no burning or grazing since 2004 (CNTL). Species listed in bold are non-native. Forb Species BOTH BURN CNTL GRAZ Max IV Group P-value Achillea millefolium 16 28 38 18 CNTL 0.026 Agoseris glauca 0 1 37 9 CNTL 0.007 Astragalus sheldonii 1 1 41 27 CNTL 0.003 Balsamorhiza incana 7 2 36 35 CNTL 0.024 Buglossoides arvensis 0 0 19 0 CNTL 0.056 Symphyotrichum campestre 0 1 19 1 CNTL 0.037 Taraxacum officinale 6 0 32 5 CNTL 0.005 Draba verna 6 13 6 34 GRAZ 0.026 Eriogonum heracleoides 23 1 0 2 BOTH 0.043 Camassia quamash 19 0 0 0 BOTH 0.052 Microsteris gracilis 23 0 2 1 BOTH 0.040 Erigeron speciosus 0 19 0 0 BURN 0.058 Frasera albicaulis 0 20 2 0 BURN 0.034 Gentiana affinis 0 28 0 1 BURN 0.007

Table 2.5 Relationships between V. dubia and forb cover (%), species richness, and diversity for + sampling years separately, and combined. For all years F(1,62), and for each sampling year F(1,14). Significance (p < 0.05) indicated in bold.

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Chapter 3: Comparing Floral Resources between Native Prairie and Seeded Old Fields on the Pacific Northwest Bunchgrass Prairie

Brogan L. Watson, Lesley R. Morris, Scott B. Lukas, Sandra J. DeBano, Heidi J. Schmalz, A. Joshua Leffler, and Scott R. Mitchell

Abstract Agricultural development, both past and present, has resulted in fragmented grasslands worldwide with gradations of native habitat ranging from active crop production, old fields, semi-natural grasslands, and seeded pastures to native remnants. This degradation and fragmentation of grasslands is linked to the global decline in native pollinators by the variation in floral resources associated with this continuum of habitat quality. Pollinators depend on floral resources for survival and require species-rich habitat with blooms present throughout the growing season. Forb communities are known to be limited in old fields but there is very little known about how the common practice of reseeding these old fields with introduced forage grasses impacts floral resources, especially on the threatened Pacific Northwest Bunchgrass Prairie (PNB). Therefore, in this study we asked the following questions: 1) how does forb abundance, richness, diversity, and community composition differ between native prairie and seeded old fields across the growing season; 2) are there indicator species between the two treatment types, growing season, and sampling years; and 3) how do floral resources differ over two growing seasons and between sampling years? We found floral resource abundance, richness, and diversity were significantly lower in seeded old fields than in native PNB sites. This legacy was seen throughout the growing seasons of two sampling years. Floral resources progressively decreased into August, when abundance, richness and diversity were lowest in seeded old fields. Differences in indicator forb species for native prairie and seeded old fields could be linked to their reproductive modes and seed dispersal. Our study underscores the differences in floral resources found around the world between native grasslands and the gradations of habitat patches that remain. Specifically, it highlights that rhizomatous forage grasses continue to dominate areas where they were previously introduced and support lower floral resource abundance, richness, and diversity than native prairie sites. Active restoration may be necessary to improve pollinator habitat on these seeded old fields and our findings 46 suggest that increasing forb richness in August might better support a more species rich population of pollinators as well. However, more research is needed to address how pollinators are actually using these floral resources and what might be lacking for specialist as well as generalist pollinators to help guide restoration questions. Additional research should focus on understanding the continuum of these grassland habitats, as they are all extremely important for the conservation of native pollinators and maintenance of ecosystem functions.

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3.1 Introduction The global decline in native bee populations has created concern (Potts et al. 2003; National Research Council 2006; Potts et al. 2009; DeBano et al. 2016), as they are important for about 87% of wildflower reproduction (Ollerton et al. 2011) along with numerous crop species. In addition to high grass biomass, grasslands systems also contain high forb diversity (Mulhouse et al. 2017) and provide native pollinators necessary floral resources and nesting sites (Corbet et al. 1992; Gathmann and Tscharntke 2002; Delaney et al. 2015). The forb community in grasslands have a longer flowering period than grasses and provide essential nutrients, proteins, and energy sources in the form of pollen and nectar for pollinators throughout the growing season (Holzschuh et al. 2007; Potts et al. 2009; Mallinger et al. 2016). Consequently bee species richness and abundance are correlated with the diversity and abundance of floral resources (Clough et al. 2014) in areas within flight distance from their nesting sites (Öckinger and Smith 2007). Populations of bees cannot persist on short-flowering periods (Holzschuh et al. 2007) provided by monocultures (Carson et al. 2016) or sown forage plants (Corbet et al. 1992; Steffan-Dewenter and Tscharntke, 2001). Most grassland ecosystems worldwide have been converted to agricultural production (Stephens et al. 2008) and loss of habitat is cited as the main reason for native bee decline (O’Toole and Gauld 1993).

Understanding the impacts of land-use changes on floral resources and pollinators is an important and an increasingly studied topic (Klein et al. 2007; Franzén and Nilsson 2008; Potts et al. 2009; Woodcock et al. 2014). Many of the agricultural landscapes around the world include gradations from production agriculture, semi-natural grasslands, semi-arid pastures, set-asides, attempted restoration, hay-meadows, and abandoned old fields seeded as pastures (Steffan- Dewenter and Tscharntke 2001; Franzén and Nilsson 2008; Weiner et al. 2011; Bhandari et al. 2018). The status of these grasslands are determined by different national programs like the semi-natural grassland system of set-aside farmland in the European Union (Corbet et al. 1992; Steffan-Dewenter and Tscharntke 2001; Franzén and Nilsson 2008), the Entry Level Stewardship in England and Wales (Potts et al. 2009), the Grain to Green policy in China (Huang et al. 2015), and the Conservation Reserve Program (CRP) in the U.S. (USDA 2019). Cropland can be taken out of active cultivation by voluntarily enrolling environmentally sensitive, agriculturally productive, land in the CRP. Farmers receive a yearly payment for enrolling their land into the program, which is reseeded with species mixtures aimed to improve environmental health and 48 quality (USDA 2019). Even before the CRP program was initiated in 1985, many abandoned cultivated lands (old fields) in the U.S. were reseeded with introduced perennial grasses to increase forage value for grazing (Morris et al. 2011; Bartuszevige et al. 2012; Morris and Rowe 2014; Morris et al. 2014; Williams et al. 2017).

When crop production ends, cultivation legacies in abandoned old fields result in long- term impacts on plant species composition and structure (Kulmatiski 2006; Morris et al. 2011; Endress et al. 2019). While large patches of remnant native grasslands retain more of the historical species composition (Alstad et al. 2016), old fields may require decades to over half a century (depending on condition of the landscape) for native species to reestablish (Nelson 1997; Kulmatiski 2006; Morris et al. 2011; Endress et al. 2019). Old fields generally contain low forb cover (Rickard and Sauer 1982; Dormaar and Smoliak 1985; Simmons and Rickard 2002; Morris et al. 2011). A recent study found species richness of flowering plants were highest at sites located within prairie remnants and differed significantly from species richness in old field sites (Delaney et al. 2015). Similar results show old fields contain lower floral abundance, diversity and richness compared to pieces of remnant Tallgrass Prairie (Kwaiser and Hendrix 2008). Exotic species that invade old fields can often establish in near monoculture stands (Kulmatiski 2006). Further, if old fields become dominated by exotic plant species, their presence throughout the landscape can persist for decades (Kulmatiski 2006; Morris et al. 2014). Reestablishment of native plant species, especially recovery of the forb community, can be hindered when non- native species are sown into old fields (Nelson 1997; Morris et al. 2011; Morris and Rowe 2014; Morris et al. 2014; Bernards and Morris 2017; Williams et al. 2017).

There is little known about how reseeding old fields with introduced forage grasses impact native bee populations. However, limited research does suggest that seeding reduces habitat stability for bees (Corbet et al. 1992) and lowers abundance and richness of bee species within crested wheatgrass (Agropyron cristatum and/or Agropyron desertorum) seedings compared to annual grass invaded and natural areas (Johnson 2008). Even if forb species are present within seeded old fields, they may not provide sufficient resources throughout the growing season to support pollinators as the larger forb community in native grasslands. Few studies have documented the availability of floral resources in different habitat types throughout bees’ foraging periods (Mallinger et al. 2016) even though this information will benefit 49 conservation efforts (Delaney et al. 2015). Studies examining floral resources across a growing season within different land uses have reported dissimilarity in forb community composition across seasons but similarity in forb richness (Delaney et al. 2015) and a lack of floral resources in the mid to late season due to lower species richness in farmlands (Persson and Smith 2013).

The Pacific Northwest Bunchgrass Prairie (PNB) of North America has a similar history described above of agricultural development, abandonment of cropland, and gradations such as remnant, actively restored, CRP seeded and set asides with native and introduced species, and natural succession to native species. It is estimated today that over 90% of this unique grassland has been converted to agriculture (Tisdale 1982; Kimoto et al. 2012) and with less than 10% of the PNB remaining, it is considered the most threatened and understudied temperate grassland in North America (Tisdale 1982). The Zumwalt Prairie (65,000 ha) represents the last largest remnant of the once extensive PNB that historically covered around 8,000,000 ha in Canada and the northwestern U.S. (Tisdale 1982).

Many old fields on the Zumwalt Prairie were cultivated in the late nineteenth century, but due to a short growing season, unsuitable soils, and extreme winters, a rapid decrease in cultivation occurred between 1938 and 1976 (Bartuszevige et al. 2012). Introduced perennial forage grass species such as Kentucky bluegrass (Poa pratensis), intermediate wheatgrass (Thinopyrum intermedium), timothy (Phleum pratense) and Canada bluegrass (Poa compressa) that were initially seeded still dominate today (Taylor et al. 2012; Endress et al. 2019; Averett et al. 2020). These seeded old fields have low species richness and contain less biodiversity than native prairie communities (Taylor and Schmalz 2012). Even though the Zumwalt Prairie hosts a wide diversity of important and even threatened bee and plant species (Kimoto et al. 2012; Tubbesing et al. 2014), there is still little research documenting the disturbance-mediated effects on them, especially cultivation legacies. One recent study reported very few forb species associated with seeded old fields and only one (Geum triflorum) increasing in cover in the short- term, but emphasized the need to evaluate longer-term changes in forb abundance and species responses (Averett et al. 2020). Two studies have examined temporal differences over a growing season in the Zumwalt Prairie, revealing seasonality of floral resources were important for the bee fauna and that both show strong seasonal variation (Kimoto et al. 2012; Mitchell 2020). 50

However, there is no research addressing the floral resources across the many seeded old fields in this grassland or how they vary seasonally.

Therefore, the objective of this study was to examine floral resources on native prairie and seeded old fields in the Zumwalt Prairie. Within this context, the key questions that we addressed were: 1) how does forb abundance, richness, diversity, and community composition differ between native prairie and seeded old fields across the growing season; 2) are there indicator species between the two treatment types, growing season, and sampling years; and 3) how do floral resources differ over two growing seasons and between sampling years? Given the documented differences in plant communities associated with cultivation legacies in a variety of ecosystem types (Ginsberg 1983; Steffan-Dewenter and Tscharntke, 2001; Öckinger and Smith 2007; Delaney et al. 2015) as well as those found in the Zumwalt Prairie, we hypothesized that native prairie sites would host a greater abundance, species richness, and diversity of floral resources than seeded old fields. We expected fewer indicator species in seeded old-field sites compared to the native prairie (Averett et al. 2020). However, given the prevalence of exotic perennial forb species found even in reseeded old fields (Morris et al. 2011), we expected that non-native species would likely be indicators of this legacy. Finally, as shown in other systems (Ginsberg 1983), we expected floral resources would be more rich, diverse, and abundant early in the growing season (Kimoto et al. 2012; Mitchell 2020) and respectively less so later in the season.

3.2 Methods

Study Area

This study was conducted in 2018 and 2019 at The Nature Conservancy’s (TNC) Zumwalt Prairie Preserve (ZPP; 45°34’ N, 116°58’ W). The ZPP consists of approximately 13,300 ha and is part of the larger Zumwalt Prairie ecosystem. Climate is considered semi-arid with an average annual precipitation of 34.9 cm (Taylor 2016), summers are warm and dry with mean daily temperatures of 24.7 °C (June – September), and winter mean daily temperatures of -2.7 °C (December – March) (Hansen et al. 2011). Meteorological data were obtained from a weather station located in the center of the ZPP, which records daily temperature, relative humidity, wind speed, and precipitation. Elevation of the study sites ranged from 1375 to 1504 m and topography was relatively flat with rolling hills (5.6% slopes on average). Soils are characterized 51 as Xerolls, consisting of colluvium and loess (Schmalz et al. 2013) that are situated over a basalt tableland (Endress et al. 2019). Plant communities of the ZPP are dominated by native grass species including Idaho fescue (Festuca idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg’s bluegrass (Poa secunda), and prairie Junegrass (Koeleria macrantha) (Kennedy et al. 2009). Plant species diversity, typical of temperate grasslands, is promoted by the many forbs found on the ZPP. Over 112 documented forb species are found on the ZPP (Kimoto et al. 2012), with western yarrow (Achillea millefolium), twin arnica (Arnica sororia), slender cinquefoil (Potentilla gracilis), lupine species (Lupinis sp.) and old man’s whiskers (Geum triflorum) being the most common forb species (Damiran et al. 2007). Nomenclature for all plant species follows the USDA Plants Database. The plots in this study have been consistently stocked at a moderate rate (0.28 – 0.4 AUM/acre) by TNC, as is the common practice in most of the Zumwalt Prairie (Mitchell 2020).

Field Sampling

Floral resources data were collected at 16 study sites selected to represent native prairie vegetation (eight sites) and seeded old fields (eight sites), distributed across the preserve (Figure 3.1; See A.1 for coordinates). Plots for this study were selected from areas mapped as seeded old fields. Native prairie sites were located in the nearest patch to the seeded old field, with similar topographic characteristics such as slope, aspect and aboveground biomass.

Three sampling bouts were conducted throughout the growing season for each sample year, with one in June, July, and August. Sampling in 2018 occurred between mid-June and early-August (June 9th - 16th; July 5th - 11th; July 31st - August 13th). The bouts in 2019 were sampled between late-June and mid-August (June 17th - 20th; July 8th - 11th; and August 13th & 14th). Due to accessibility and time constraints, data from native prairie sites 1 and 2 and seeded old-field sites 1 and 2 could not be collected in 2018. At each site, plants were sampled along five parallel, 20 m by 0.3 m belt transects (Figure 3.2). Transect arrays were centered at each site, separated by 15 m and oriented east to west. Blooming stems encountered in each belt transect were visually identified, and tallied by species. Total abundance of blooming stem counts were summed at the plot level. All blooming plants, except two genera, Crepis and Lupinus, were identified to species. To reduce bias, the same individual preformed the observation during each sampling period for both years. 52

Environmental variables including: elevation (m), aspect (°), slope (%) and soil samples were collected at each site. Elevation was obtained from TNC (See A.2), slopes were determined by visually locating the line of greatest slope through the site and then measured with a clinometer, and aspect was measured with a compass. Soils were sampled from 15 composited soil subsamples per site using a 2.5 cm diameter soil probe to a depth of 20 cm and sent to an analytical laboratory (KUO Testing Labs, Othello WA). Samples were processed using standard protocols for soil carbon (inorganic, organic, and total %), bulk density (g/cm3), the texture (sand, silt, and clay), and the classification of texture. All data were compiled across sampling bouts and years for this analysis.

Statistical Analysis

To examine forb community composition between native prairie and seeded old-field sites, data were compiled into matrices and analyzed using PC-ORD Version 7.08 (McCune and Mefford 2016). The forb species matrix (92 site/bouts x 74 forb species) contained floral resources abundance, or values of bloom counts, for each species in a plot during each sampling period. The 92 site/bouts in the matrix represents the 16 sites sampled 3 times during the growing season, for two years (without the 4 missing sites in 2018). Rare species (N ≤ 1) were removed and a logarithmic transformation (log (x+1)) was preformed, leaving 64 species with log- transformed abundances. Additional data recorded in the field and from spatial databases were used to construct an environmental matrix (92 site/bouts x 22 environmental variables). The environmental matrix included binary variables for treatment (native prairie vs. seeded old field), categorical variables (sum of blooming abundance, richness, diversity, day of year, and year), sampling bout (June, July, or August), and quantitative data of site characteristics including elevation, slope, aspect, species richness, species diversity, inorganic, organic and total carbon, bulk density, percent sand, silt or clay within the soil, and classification of soil texture (loam, sandy loam or silt loam).

Forb community composition between treatments was summarized graphically with a Non-metric Multidimensional Scaling (NMS) ordination with the “slow and thorough” autopilot setting, and no penalty for ties and Sorensen distances. Linear relationships were identified between forb community compositions with environmental variables using a joint plot overlay. Data were analyzed with an analysis of variance (ANOVA) to test for differences in forb 53 abundance, species richness, and diversity between treatment types. Data did not meet the assumptions of normality and therefore Multi-response Permutation Procedures (MRPP) were used to determine whether forb community composition varied significantly over the two growing seasons and between treatment types (native prairie and seeded old fields). The mean within group distances were calculated, then compared with expected distance through permutation (McCune and Mefford 2016). A p-value is generated by the MRPP test, representing the probability of observing a value for the test statistic as extreme or more extreme than the observed distance due to chance. A measure of effect size, the chance-corrected within-group agreement (A-statistic), indicates group differences compared to chance (McCune and Grace 2002). Where there is no heterogeneity within a group, A=1, while A=0 means the homogeneity within a group equals random expectation (McCune and Mefford 2016).

Indicator species analysis (ISA) was performed to evaluate affinities for individual species between native prairie and seeded old-field sites and between sampling periods. ISA combines information on a particular species’ abundance in each pre-defined group, its “faithfulness” to each group, and its “exclusivity” to that same group. An indicator value (IV) based on abundance and relative frequency is produced for each species, for each group (McCune and Grace 2002). Higher IV’s represent stronger affiliation with a certain group. Maximum IV’s are then tested for statistical significance using a Monte Carlo test.

3.3 Results

The climate station for the ZPP recorded mean monthly precipitation of 3.13 cm and 3.23 cm in the sampling years of 2018 and 2019, respectively (TNC unpublished data). The monthly precipitation (Figure 3.3) was consistent with the 14-year average (2006 – 2019) with a typical spring and fall peak.

Differences between Native Prairie and Seeded Old Fields

Floral resource abundance differed (p < 0.001), as did species richness (p < 0.0001), and species diversity (p < 0.01), between native prairie and seeded old-field sites (Figure 3.4). Forb species composition also differed between the two treatment types (A = 0.023, p < 0.001), and sample months (A = 0.251, p < 0.0001), with differences in June (A = 0.058, p < 0.0001), dipping in July (A = 0.066, p < 0.0001), and increasing into August (A = 0.085, p < 0.0001) (Figure 3.5). 54

Forb species composition was more similar between sites at the beginning of the growing season, but became more dissimilar as the season continued. Overall, throughout each sampling period native prairie sites supported higher richness, diversity and abundance of blooming forb species than seeded old fields (Figure 3.4).

Roughly 80% of the variation in forb community composition is explained with axis 1 (R2 = 0.59) and axis 2 (R2 = 0.19) in the 2-dimensional NMS ordination (Figure 3.6). Based on the joint plot overlay, NMS axis 1 was most correlated with a division between day of year, species richness, species diversity, and bloom abundance, suggesting these forb community attributes decline over the season. These results indicated that species composition among sample units from both treatment types were relatively similar at the beginning of the growing season, but diverged in composition at the end of the growing season (Figure 3.6). Early season species included: Potentilla gracilis, Arnica sororia, Geum triflorum, Lupinus sp. and Frasera albicaulis. While species like Perideridia gairdneri, Grindelia nana, Solidago missouriensis, Erigeron pumilus, and Cirsium brevifolium were correlated with later in the growing season.

The single and strongest environmental gradient correlated with NMS axis 2 was slope, and no effect due to soil carbon, bulk density, or texture was found (Figure 3.6). Forb species that were more associated with steeper slopes and native prairie sites included Erigeron pumilus, Orthocarpus tenufolius, Packera cana, Castilleja lutescens, and Clarkia parviflora. While species that are correlated with more gradual slopes, included forbs such as Grindelia nana, Chrysothamnus viscidiflorus, Trifolium hybridium, Dianthus ameria, and Calochortus eurycarpus.

Indicator Species

The ISA revealed that 95% of the significant indicator species had higher IV’s for native prairie sites than seeded old fields (Table 3.1). Achillea millefolium, A. sororia, and G. triflorum had moderately high IV’s for seeded old fields, while Grindelia nana was the only significant forb species with a stronger affinity to the seeded old-field group (Table 3.1). The species, G. nana, was ranked in the top 15 most abundant species for seeded old fields but ranked 45th in native prairies (data not shown). The ISA conducted for each sample period (June, July, and August) showed the majority of significant forb species had higher IV’s for the native prairie group throughout the course of the growing season (Table 3.2). However, forb species Antennaria 55 luzuloides and G. nana were the only species with higher affiliation to the seeded old-field group (Table 3.2). The ISA conducted for each sampling period separated by year showed differences in species significance and maximum IV for each sampling period (Table 3.3).

Temporal Differences between Growing Season and Year

There were large seasonal differences in the abundance, richness and diversity of floral resources between growing seasons and sample years. Floral resources differed strongly between the sample periods (A = 0.204, p < 0.0001). Main temporal differences were forb abundance, species richness, and species diversity. Study sites sampled from both treatments in June had the highest abundance, species richness, and diversity compared to sites sampled in August which had the lowest bloom abundance, species richness and diversity over the growing season (Figure 3.7a). Over the course of the two growing seasons, 47 forb species bloomed during the June sampling period, 43 in July, while August only had 23 forb species in bloom (data not shown). The majority of the ten-most dominant species bloomed throughout the first two sampling periods and were not typically present later in the season. For example, five species (Arnica sororia, Crepis sp., Geum triflorum, Lupinus sp., and Potentilla gracilis) tended to bloom across the first two sample periods (June and July), while five different forb species (Dianthus armeria, Epilobium brachycarpum, Erigeron pumilus, Madia glomerata, and Silene spaldingii) bloomed throughout the last two sample periods (July and August; See A.3).

Floral resources differed in June and August between sample years and treatment types, but not in July (June A = 0.058, p = 0.00002; July A = 0.010, p = 0.119; August A = 0.021, p = 0.049) (Figure 3.5). Forb species present in June, July and August of 2018 were 36, 38, and 22, respectively. While there were 41 species present in June, there were 38 in July and 13 in August of 2019. Overall, forb abundance, species richness and diversity was highest in June for both years, began to decline during the July sampling bout, and continued declining into August when the lowest abundance, species richness and diversity was observed (Figure 3.7b). Species diversity followed the same trend as abundance and richness, with a peak in June and declining in July and August between the two sample years. However, a total of 48,258 blooms were recorded from 87 forb species in 2018, and 28,723 from 77 species in 2019. In total ten more forb species were observed in 2018 than in 2019.

3.4 Discussion 56

Differences between Native Prairie and Seeded Old Fields

Our results support previous findings that historical land uses, like cultivation and seeding old fields, leave a lasting legacy on forb communities (Kwaiser and Hendrix 2008; Persson and Smith 2013; Delaney et al. 2015; Mallinger et al. 2016). Floral resource abundance, richness, and diversity were significantly lower in seeded old fields than in native PNB sites, which previously were not characterized. Cultivation legacies also affect graminoids (Nelson 1997) and many have a longer lasting influence over the forb communities in numerous ecosystems including grasslands (Allen et al. 2005; Holzschuh et al. 2007; Öckinger and Smith 2007; Weiner et al. 2011; Delaney et al. 2015) and shrublands (Morris et al. 2011), and especially in seeded areas (Johnson 2008; Morris et al. 2014; Williams et al. 2017). Sometimes as few as two forb species are found in areas seeded with introduced forage species (Johnson 2008). While I did not examine mechanisms for this difference, others have suggested that fewer forbs in seeded areas is related to the competitive nature of the introduced forage species (Grygiel et al. 2009) as well as self-facilitating changes (conditioning soils that benefit their own growth and inhibit other species) in the soils (Jordan et al. 2008; Perkins and Nowak 2012). Our results of lower forb abundance in seeded old fields may be attributed to the density of rhizomatous grasses limiting the amount of bare ground and available space for forbs to establish (Endress et al. 2019).

The lasting effect on the forb community could also be seen through the growing season between seeded old fields and native prairie. As others have reported on the ZPP (Kimoto et al. 2012; Mitchell 2020), all sampling sites begin the growing season in June with more abundant floral resources, higher species diversity, and higher richness. However, our study also showed that seeded old fields start off lower than the native prairie in June and became even less abundant, diverse, and rich in comparison to the native prairie as the season continued. The abundance, richness and diversity of floral resources were especially lower in seeded old fields by August than in other sample months. Forb species composition between native prairie and seeded old fields differed the least in July of both years and the most in August (Figure 3.5). These results are consistent with others who report much lower floral resources within old fields (Kwaiser and Hendrix 2008; Delaney et al. 2015) and in seeded pastures and reconstructed prairie sites (Delaney et al. 2015) in comparison with native prairies. 57

It was surprising that slope, ranging from 1 to 15°, was the only environmental variable that appeared to influence forb community composition. This result suggested that sample sites located in native prairie remnants were found on steeper slopes, which corresponds with cultivation tending to occur on lesser slopes due to equipment limitations, especially in the early 20th century (Csorba 2010).

Indicator Species

Our indicator species results support the findings by Averett et al. (2020), who reported more forb indicator species in native prairie sites than in seeded old fields. However, unlike what has been reported about forbs in old fields (Kulmatiski 2006; Morris et al. 2011; Fenesi et al. 2015) and seeded old fields (Morris et al. 2014), exotic forbs were not indicative of seeded old fields on the PNB. In fact, none of the indicator species for either treatment were exotic forbs, a distinction that can sometimes best explain differences between these types of sites (Kulmatiski 2006). Two native genera that are commonly found in disturbed areas like old fields (Anderson 1980; Elmore et al. 2006; Morris et al. 2011), G. nana and Chrysothamnus viscidiflorus, along with A. luzuloides, were common indicators in our seeded old fields (Table 3.2). All three of these species are members of the Asteraceae family and reproduce via achenes that are spread by the wind (Torrey and Gray 1843), a trait that can assist in reestablishment into disturbed sites (Hobbs and Yates 2003; Standish et al. 2007; Morris et al. 2011; Morris et al. 2014). These Asteraceae species may help support pollinators in the PNB given the results of a similar study conducted in Germany where intensively managed meadows with more Apiaceae and Asteraceae supported generalist pollinators (Weiner et al. 2011). It is not surprising that A. millefolium, Geum triflorum, A. sororia, and Lupinus sp. were indicator species for more than one sampling period, between treatments, and across years since they are common forbs on the PNB (Damiran et al. 2007).

The two forb species, P. gairdneri and Zigadenus venenosus, stand out as indicators of native prairie sites. Perideridia gairdneri has tuberous roots and is an important food plant for Native Americans (Davis 2019). Zigadenus venenosus can reproduce by seed but commonly reproduces vegetatively by sprouting from mature bulbs or through bulb splitting (Miller 2000). Another native prairie indicator species was Castilleja lutescens, which are autotrophic hemiparasites, along with many in their genus (Reed 2012), but are also known to grow 58 autonomously. These root morphologies, modes of reproduction, and growing strategies are often slow to recover in areas that have been plowed (Jenkins and Parker 2000; Dyer 2010; Morris et al. 2011). Though S. missouriensis is a very common species and can be found thriving on both plowed and unplowed sites (Olson 1975; Platt 1975), it was only an indicator of native prairie in our study sites (Table 3.3). It can reproduce by plentiful wind-dispersed seeds but also through rhizomes (Johnson and Nichols 1982), which may give it an advantage in the unplowed native prairie sites on the ZPP. Blooming in late fall, S. missouriensis may be an important floral resource on the native prairie sites for pollinators when abundance is low (Bare 1979; Roof et al. 2018).

Indicator species varied between years. For example, A. sororia had higher IV’s to both treatment groups in June of 2019 than in 2018 but was only significant in 2019 (Table 3.3). Another common species, P. gracilis, was an indicator species in the June sample period, but was only a significant species in 2018. Agoseris glauca had an IV affiliated to native prairie sites in both 2018 and 2019, yet was significant only in July of 2019. Indicator species, A. millefolium and E. pumilus, had higher IV’s for the native prairie group but were only significant in 2018 (Table 3.3). The forb species A. millefolium, A. glauca, E. pumilus and A. sororia are all perennials that belong to the Asteraceae plant family, providing resources for generalist pollinator species (Weiner et al. 2011). Potentilla gracilis is also a species that supports generalist pollinators but it is a member of the Rosaceae family. Interestingly A. glauca was the only forb species that had IV’s of zero for the seeded old-field sites for both years. Although it is wind-dispersed, distance to the nearest seeding population and competition with exotic grasses can interact in a way that could also limit the recovery of this native forb into the seeded old fields (Morris 2012). In other words, if there are no species near old fields, the wind may not be able to carry the lightweight seeds far enough and conditions may inhibit their establishment in the seeded old fields naturally.

Temporal Differences between Growing Season and Year

When examined for differences over two growing seasons between two sampling years (2018 and 2019), this study showed similarity in both years in their seasonal pattern with highest abundance, richness, and diversity of inflorescences in the early-season and lowest in the late- season. We also found a peak bloom occurring in June on the PNB, which is consistent with 59 other such blooming peaks reported in June (Ginsberg 1983; Mitchell 2020). In fact, Kimoto et al. (2012) and the only other study examining seasonal changes on the Zumwalt Prairie (Mitchell 2020), also found higher stem and species blooms occurring in June, less during the month of July, and almost no blooming forb species in August.

Though the patterns are similar between years, the 2018 growing season provided more abundant, rich, and diverse floral resources than the 2019 season. We identified three possible explanations for this pattern. One is the difference in precipitation patterns between the two years since floral resources are often linked to rainfall (Jones et al. 2016). Although climate variables were not factors of the analyses, the lower than average fall and winter precipitation in 2018 may have created conditions for lower bloom abundance the following spring through to August of 2019 (Figure 3.3). Different precipitation patterns can influence changes in forb cover and species richness in other systems like the Tallgrass prairie (Jones et al. 2016). A second explanation could be that more annuals were encountered in 2018 than in 2019, which may explain the large difference in total blooms. There are several small annual species such as Collomia linearis, Clarkia pulchella, Collinsia parviflora, Draba verna, and Microsteris gracilis making up the majority of diversity during this time frame. Another explanation for the observed difference in bloom abundance is time of sampling. Sampling in 2018 began eight days earlier than in 2019, which may have influenced the amount of total blooms. This suggests the possibility of peak bloom occurring earlier in June, which might have been missed during the 2019 June sample period.

Study Limitations and Future Research

The findings reported in this study are an important step toward understanding the stark differences in habitat quality available for pollinators, like native bees, on the PNB. However, more research is needed to translate these findings into habitat needs of specific pollinators and that includes a measure of scale or distance in availability of floral resources. Habitat quality for native bees, for example, can vary by body size (Steffan-Dewenter and Tscharntke 2001), and capability to fly to necessary floral resources from their nesting sites (Zurbuchen et al. 2010). An area for future research would be to address the issues of scale related to these land-use types as has been done in other studies (Zurbuchen et al. 2010; Rhoades et al. 2016). If pollinators nest in 60 close proximity to seeded old fields, there may not be adequate floral resources present that are necessary to support the community.

It is also possible that the lack of exotic forb indicator species in seeded old fields or even native prairie sites could be due to the management efforts by TNC to eliminate two introduced forbs in the ZPP including sulfur cinquefoil (Potentilla recta) and western hawkweed (Hieracium caespitosum) with herbicide applications (TNC personal communication). Therefore, other PNB sites that do not manage these species may have more exotic forbs that can also serve as floral resources. For example, P. recta can bloom from June to October (Ginsberg 1983), which may be able to support pollinator species later in the season when other floral resources are less available. Nectar and pollen from exotic species are considered valuable supplement for native pollinators (Bjerknes et al. 2007) but the degree to which exotic plants may benefit pollinators is uncertain (Palladini and Maron 2014). Future research should include sites where exotic species are more prevalent to test.

Another important next step would be to evaluate how pollinator communities differ between these two grassland sites in response to differences in floral resources and how restoration may assist in conservation. Our findings are important for future research and management efforts because they point to ways in which pollinators might benefit from integrating prairie plantings within abandoned agricultural landscapes. Forb species richness can be a good predictor of bee species richness, while forb cover can be used to predict bee abundance (Steffan-Dewenter and Tscharntke 2001), therefore it is beneficial to evaluate flowering plants on the landscape in order to estimate pollinator populations. A recent study on the ZPP found that bee abundance peaked in August but was made up of two generalist bee species (Mitchell 2020). Perhaps a more species rich bee population would be better supported by greater forb diversity in August.

Finally, our findings highlight a need for more active restoration research in this remnant grassland. Incorporating forb species into restorative plantings could benefit ecosystem stability and, although it may be an added cost, not doing so may result in inadequate floral resources (Robson et al. 2017). Without restoration efforts, native species recovery in previously cultivated lands may also require decades to over half a century to reestablish, because once areas become established by a dominance of exotic plants, their presence on the landscape can persist for 61 decades (Morris et al. 2011). In the only study that examined restoration on seeded old fields in the ZPP, Taylor et al. (2012), found seeded native forbs rebounded and increased two years after herbicide treatment reduced the introduced forage grasses. Averett et al. (2020) found no change in native perennial forbs over a period of seven years in seeded old fields. Likewise, our results suggest very little natural successional re-establishment of forbs over time. And, as others have found, seeded old fields still possess lower abundance, richness, and diversity of forbs even as time since abandonment continues (Steffan-Dewenter and Tscharntke 2001; Fenesi et al. 2015). However, more research is needed to address how pollinators are actually using these floral resources and what might be lacking for specialist as well as generalist pollinators to help guide restoration questions. If restoration or increasing the floral resources in degraded grassland areas is the goal, it may be beneficial to add more specialized plant species to a prairie restoration seed mix (Robson et al. 2017). Creating new foraging habitats throughout current or past agricultural landscapes can assist in supplying native pollinators the resources they need throughout the growing season.

3.5 Conclusion

This research underscores the differences in floral resources between native prairie and the gradations of native grasslands existing around the world (Corbet et al. 1992; Steffan-Dewenter and Tscharntke 2001; Franzén and Nilsson 2008; Weiner et al. 2011; Bhandari et al. 2018). However, this is the first time the overall differences in forb community as well as lack of blooming forb abundance, richness, and diversity have been documented as potentially low quality habitat for pollinator species in the PNB. Our findings also support previous research indicating that plantings of non-native forage grasses leave a lasting legacy of altered stable plant communities (Kulmatiski 2006; Johnson 2008; Morris et al. 2011; Morris and Rowe 2014; Morris et al. 2014; Williams et al. 2017). Introduced forage grasses are still used today, but come with the assumption that a stable monoculture of grasses should be a higher priority than biodiversity when they are used at a site (Robins et al. 2013). Finally, our results have implications for the suitability of pollinator habitat across the widespread program of seeding old fields to retire these lands from cultivation in the U.S. CRP program as well as similar programs employed around the world (Steffan-Dewenter and Tscharntke 2001). 62

Since temperate grasslands and their biodiversity are threatened (Hoekstra et al. 2005; Stephens et al. 2008) and their pollinators are on the decline (Kearns et al. 1998; Steffan- Dewenter et al. 2005), there is significant research focus on this aspect of conservation. Of course, forbs are not just an important part of pollinator habitat but are important for other wildlife species. Moreover, these native forb communities make up an important part of traditional plant collection for Native Americans in the region (Davis 2019). For example, the Perideridia gairdneri is a culturally significant plant that is now found at a frequency of less than 2% across other portions of the Pacific Northwest Bunchgrass Prairie (Davis 2019). Any examination for restoration of forb species across threatened and fragmented grasslands should include consideration of increasing these valued traditional species as well. Grassland habitats exist as native remnants and in a spectrum with varying degrees of the native forb communities. More research is needed to increase our understandings in the continuum of these habitats, as they are all extremely important for the conservation of native pollinators and maintenance of ecosystem functions.

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Kwaiser, K.S., and S.D. Hendrix. 2008. Diversity and abundance of bees (Hymenoptera: Apiformes) in native and ruderal grasslands of agriculturally dominated landscapes. Ecosystems and Environment 124:200-204. Mallinger, R.E., Gibbs, J., and C. Gratton. 2016. Diverse landscapes have a higher abundance and species richness of spring wild bees by providing complementary floral resources over bees’ foraging periods. Landscape Ecology 31(7):1523-1535. McCune, B. and J.B. Grace. 2002. Analysis of ecological communities. Gleneden Beach, OR: MJM Software Design. McCune, B. and M.J. Mefford. 2016. PC-ORD. Multivariate Analysis of Ecological Data. Gleneden Beach, OR: MJM Software Design. Miller, M. 2000. Fire autecology. In: Brown, James K.; Smith, Jane Kapler, eds. Wildland fire in ecosystems: effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: US Department of Agriculture, Forest Service, Rocky Mountain Research Station 9-34. Mitchell, S.R. 2020. Impacts of range management decisions on native pollinators: innovative grazing practices and riparian restoration. Thesis, Oregon State University. Morris, L.R., Monaco, T.A., and R.L. Sheley. 2011. Land-use legacies and vegetation recovery 90 years after cultivation in Great Basin sagebrush ecosystems. Rangeland Ecology and Management 64(5):488-497. Morris, L.R. 2012. Land-use legacy efforts of cultivation on ecological processes. In: Invasive Plant Ecology and Management: linking processes to practice. 36-56. Morris, L.R., Monaco, T.A., and L.R. Sheley. 2014. Impact of cultivation legacies on rehabilitation seedings and native species re-establishment in Great Basin shrublands. Rangeland Ecology and Management 67(3):285-291. Morris, L.R., and R.J. Rowe. 2014. Historical land use and altered habitats in the Great Basin. Journal of Mammalogy 95(6):1144-1156. Mulhouse, J.M., Hallett, L.M., and S.L. Collins. 2017. The influence of seasonal precipitation and grass competition on 20 years of forb dynamics in northern Chihuahuan Desert grassland. Journal of Vegetation Science 28(2):250-259. National Research Council. 2006. Status of pollinators in North America. National Academic Press, Washington D.C. Nelson, J. K. 1997. Natural succession impeded by smooth brome (Bromus inermis) and intermediate wheatgrass (Agropyron intermedium) in an abandoned agricultural field (No. RFP-5137; CONF-971165-). EG and G Rocky Flats, Inc., Golden, CO, US. Rocky Flats Plant. Öckinger, E., and H.G. Smith. 2007. Semi-natural grasslands as population sources for pollinating insects in agricultural landscapes. Journal of Applied Ecology 44:50-59. 67

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Chapter 3: Figures

Figure 3.1 Locations of eight native prairie (NP) and eight seeded old-field plots (OF). Sixteen plots were sampled three times throughout the growing season in 2018 and 2019, across the two treatment types. The site NP6 only appears to be in a seeded old field due to the scale of the map.

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Figure 3.2 Site sampling design: Five parallel 20 x 0.3 m belt transects, spaced 15 m apart. Blooming stems were recorded along each transect.

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Figure 3.3 Total monthly precipitation received at Zumwalt Prairie Preserve weather station throughout two sampling years. Average monthly total precipitation based on 14-year average (2006 - 2019).

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Figure 3.4 Boxplots showing the differences in species abundance, richness, and diversity throughout sampling months between two years in native prairie and seeded old-field sites. The central boxes contain 50% of the data, the line in the middle of the box is the median, whiskers extend from the box indicate 1.5 times the interquartile range, and hollow circles represent potential outliers. 74

Figure 3.5 Multi-Response Permutation Procedures (MRPP) A-statistics describing compositional differences between native prairie and seeded old fields for 2018 and 2019. Larger A-statistics indicate stronger differences between groups.

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Figure 3.6 Non-metric Multidimensional Scaling (NMS) ordination of sample units in forb species space. Joint plot vectors show direction and magnitude of linear correlations between bloom abundance and the ordination space. Scientific names adjacent to axes represent the highest correlated forb species along that particular axis.

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Figure 3.7 Boxplots showing a) Temporal differences in forb abundance, species richness, and diversity (Shannon-Wiener) over the course of the growing season for both sampling years; b) Temporal differences in forb abundance, species richness, and diversity (Shannon-Wiener) throughout the course of the two growing seasons (2018 and 2019).

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Chapter 3: Tables

Table 3.1 Significant indicator species between treatment types showing maximum indicator values (IV), for each treatment (NP = native prairie, SOF = seeded old field), for both years (2018 and 2019). All species are native.

Forb Species NP SOF P-value Achillea millefolium 52 32 0.0234 Agoseris glauca 20 0 0.0016 Arenaria congesta 13 1 0.0480 Arnica sororia 41 19 0.0354 Castilleja cusickii 20 2 0.0338 Castilleja lutescens 30 0 0.0006 Clarkia pulchella 28 0 0.0004 Collomia linearis 18 1 0.0206 Eriogonum heracleoides 20 0 0.0024 Galium boreal 13 0 0.0270 Geum triflorum 39 16 0.0380 Hieracium cynoglossoides 22 3 0.0288 Lupinus sp. 49 8 0.0004 Orthocarpus tenuifolius 28 0 0.0004 Perideridia gairdneri 25 1 0.0024 Sidalcea oregana 17 0 0.0058 Solidago missouriensis 16 0 0.0214 Zigadenus venenosus 23 2 0.0116 Grindelia nana 1 25 0.0036

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Table 3.2 Significant indicator species showing maximum indicator values (IV), comparing species composition from sampling periods between treatment types (NP = native prairie, SOF = seeded old field), for both years (2018 and 2019).

Forb Species NP SOF P-value June

Antennaria luzuloides 12 57 0.0290 Arnica sororia 59 35 0.0026 Castilleja lutescens 41 0 0.0262 Collomia linearis 48 4 0.0224 Frasera albicaulis 60 23 0.0238

Geum triflorum 57 40 0.0370 Lupinus sp. 77 11 0.0002 Zigadenus venenosus 77 6 0.0002 July Achillea millefolium 58 39 0.0044

Agoseris glauca 50 0 0.0028 Arnica sororia 68 22 0.0020 Castilleja lutescens 44 0 0.0070 Clarkia pulchella 42 0 0.1040 Eriogonum heracleoides 38 0 0.0166 Geum triflorum 70 9 0.0006 Lupinus sp. 74 13 0.0002 Orthocarpus tenuifolius 44 0 0.0066 Sidalcea oregana 44 0 0.0070 August Erigeron pumilus 60 12 0.0070 Grindelia nana 4 50 0.0078 Hieracium cynoglossoides 39 1 0.0232 Perideridia gairdneri 73 2 0.0002 Solidago missouriensis 46 1 0.0054

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Table 3.3 Maximum indicator values (IV) of indicator species for each sampling bout and treatment (native prairie = NP; seeded old field = SOF) associations for 2018 and 2019. Significance (p < 0.05) indicated in bold.

2018 2019 Forb Species NP SOF P-value NP SOF P-value June Arnica sororia 14 3 0.0582 64 27 0.0038 Lupinus sp. 76 12 0.0076 79 10 0.0006 Potentilla gracilis 45 55 0.0156 48 46 0.9656 Zigadenus venenosus 76 12 0.0170 78 3 0.0050 July Achillea millefolium 60 35 0.0372 57 43 0.0394 Agoseris glauca 38 0 0.2036 63 0 0.0238 Arnica sororia 66 30 0.0010 76 12 0.0066 Geum triflorum 71 10 0.0158 70 10 0.0142 Lupinus sp. 75 13 0.0030 73 13 0.0088 August Achillea millefolium 67 24 0.0138 40 27 0.7061 Erigeron pumilus 63 10 0.0478 57 13 0.1008 Grindelia nana 5 49 0.0546 2 50 0.1028 Perideridia gairdneri 78 3 0.0046 68 2 0.0166 Solidago missouriensis 38 0 0.2054 54 3 0.0518

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Chapter 4: General Conclusions

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4.1 Conclusion

The observed declines in native pollinators worldwide has increased concern and research into the disturbances, past and present, which contribute to these losses. Floral resources that pollinator populations depend on have also be affected by changes in land-use, which can further impact the pollination of agricultural and native plant species. In grasslands, for example, habitat degradation and fragmentation from historical and current agricultural development, as well as livestock grazing has left only a few remnants of these native systems. Grassland remnants face further transformation by altered fire regimes and invasive species (Roof et al. 2018; Black et al. 2011; Steffan-Dewenter et al. 2005; Potts et al. 2010; Clough et al. 2014). With the few natural systems that remain scattered across the globe, additional understanding of how different disturbances can impact available floral resources for pollinator populations is necessary to evaluate whether grasslands contain sufficient resources throughout the growing season (Steffan- Dewenter et al. 2005; Moisset and Buchmann 2010; Potts et al. 2010; Black et al. 2011; Clough et al. 2014; Roof et al. 2018). One of the most threatened and understudied of the fragmented temperate grasslands is the Pacific Northwest Bunchgrass Prairie (PNB) located in the northwest region of the U.S. (Tisdale 1982).

In Chapter 2, we explored the effects of three disturbances (prescribed fire, grazing, and invasive species) on the floral resources within the largest remaining remnant of the PNB, known as the Zumwalt Prairie. Specifically, we addressed how prescribed fire, grazing, and their interactions impact forb community composition, cover, richness, and diversity over 10 years. To address these questions, we used permanent long-term monitoring plots established in 2004 on the Zumwalt Prairie Preserve (ZPP), owned and managed by The Nature Conservancy (Taylor and Schmalz 2012). The prescribed fires were applied in the fall of 2006 and 2016, and vegetative cover data were recorded in 2008, 2010, 2016 (preburn) and 2018. Using this cover data, we examined the response of forb cover, richness, and diversity to the newest invasive threat to the PNB, Ventenata dubia. Although there was less forb cover in our grazed plots, our results indicated that prescribed fire has a greater effect on the forb community composition than moderate grazing or no livestock grazing. Furthermore, our results suggest that a ten-year fire return interval does not significantly influence forb species richness or diversity on the ZPP. 82

There were, however, different indicator species for each of the treatments that illustrate the importance of maintaining disturbances like prescribed fire and herbivory on this unique prairie remnant. For example, Camassia quamash, is culturally important to Native American tribes such as the Nez Perce (Davis 2019) and our findings support others who report fire stimulates its regeneration. Even though disturbances may affect individual species in different ways, impacts to species of concern like C. quamash and Silene spaldingii (USFWS 2007; Taylor et al. 2012) need to be studied for conservation, cultural significance, and importance to native pollinators. Finally, the invasive annual grass, V. dubia, has been rapidly and consistently increasing in cover in our study area (Averett et al. 2020). We found significant negative correlations between forb cover and richness when V. dubia cover was between 20 - 37%. These findings indicate a threshold may exist at this level of invasion, above which forb cover may be negatively impacted by V. dubia. Therefore, the expansion of V. dubia should be monitored continually.

In Chapter 3, we explored the legacy disturbance of agricultural development on the PNB. The Zumwalt Prairie, like so many other temperate grasslands, was cultivated for cereal grains through the 1930s. However, since this grassland was only marginal for crop production, cultivation was abandoned and the old fields were seeded with exotic pasture grasses. These seeded old fields are still dominated by near monocultures of introduced forage grasses that may have negative repercussions for the floral resources upon which native pollinators depend. Therefore, we examined how floral resources differed between seeded old fields and native prairie sites. Specifically, we looked at differences in forb community, abundance, richness, and diversity between these sites (treatments), tested for indicator species within each treatment, and included comparisons over the course of two consecutive growing seasons. Although both sites had a similar trend in floral resources over the growing season, native prairie sites consisted of more abundant, rich, and diverse floral resources than seeded old fields.

Our findings add to the evidence that the legacy of cultivation and reseeding disturbances can persist long after these land uses end, especially on forb communities (Kulmatiski 2006; Johnson 2008; Kwaiser and Hendrix 2008; Morris et al. 2011; Morris et al. 2014; Delaney et al. 2015; Endress et al. 2019). More floral resources were present at the beginning of both growing seasons with a peak bloom period in early June in both treatment types. As for yearly variation, 83

2018 had more blooms than 2019 but both years had the same trend in abundance, richness, and diversity throughout the season, a finding we believe is related to higher precipitation in that year. However, forb abundance, richness, and diversity were all lower in seeded old fields across the growing season in comparison to native-prairie sites, suggesting this legacy may leave lower quality habitat for pollinators in seeded old fields. Finally, we also found differences in indicator species between the sites and over the growing season that point to important areas of future research. The findings in this study highlight a need for more research into how pollinators respond to these differences, and how active restoration may be needed to conserve forb communities for pollinators as well as culturally significant forb species for indigenous people in the region.

These studies are the first to address questions about how disturbances (prescribed fire, livestock grazing, invasion by V. dubia, and cultivation legacies) affect the composition, abundance, richness, and diversity of forb communities on the PNB. The results from this research can help land managers, mainly in the PNB ecosystem, conserve and promote floral resources for native pollinators. Prescribed fire stands out as a vital disturbance for promoting specific forb species that support native pollinators and indigenous populations. More work is needed to explore how fire timing and intensity relate to conservation. Additional research is also needed to evaluate pollinator use of these sites directly and to expand both the spatial and temporal scale of sampling and inference. For example, there may be adequate floral resources available for some pollinators and not others, depending upon their body size and forb preferences. If restoration is a management goal, practitioners may consider planting specific forbs that could extend spatial and seasonal availability of floral resources throughout the season.

Additional studies should be conducted to assess temporal variability, and possibly consider sampling for a longer period throughout the growing season. This would allow an evaluation of how many floral resources are available to pollinators before the peak bloom occurs in early June, and later in the season (beyond August) when floral resources become less abundant, rich, and diverse. It is important to determine ways to increase floral resources in areas that have been previously cultivated and seeded with forage grasses if it would positively benefit pollinators. For example, it is possible that increasing late blooming species abundance in seeded old fields could reduce distances to floral resources and pollinator energy expenditure would 84 decrease late in the season. Such research could include monitoring pollinator activity and presence over the duration of when floral resources are in bloom. Given there is little research specifically on forb communities in grassland systems, additional research is needed to take a closer look at the temporal variation in grassland communities (Robson 2019). Globally, temperate grassland habitats now exist as patches of native remnants and a continuum of altered habitats. More research needs to focus upon understanding the continuum of these habitats, as they are all extremely important for the conservation of native pollinators and maintenance of all ecosystem services.

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4.2 Literature Cited Averett, J.P., Morris, L.R., Naylor, B.J., Taylor, R.V., and B.A. Endress. 2020. Vegetation change over seven years in the largest Pacific Northwest Bunchgrass Prairie remnant. PLoS ONE 15(1):1-20. Black, S.H., Shepherd, M., and M. Vaughan. 2011. Rangeland management for pollinators. Society for Range Management 9-13. Clough, Y., Ekroos, A.B., Batary, P., Bommarco, R., Gross, N., Holzchuh, A., Hopfenmuller, S., Knop, E., Kuussaari, M., Lindborg, R., Marini, L., Öckinger, E., Potts, S., Poyry, J., Roberts, S., Steffan-Dewenter, I., and H. Smith. 2014. Density of insect-pollinated grassland plants decreases with increasing surrounding land-use intensity. Ecology Letters 17:1168-1177. Davis, C. 2019. The Palouse Prairie, a vanishing Indigenous Peoples garden. Journal of Native Sciences 1(1):1-17. Delaney, J.T., K.J. Jokela, and D.M. Debinski. 2015. Seasonal succession of pollinator floral resources in four types of grasslands. Ecosphere 6(11):243. Endress, B.A., J.P. Averett, B.J. Naylor, L.R. Morris, and R.V. Taylor. 2019. Non-native species threaten the biotic integrity of the largest remnant Pacific Northwest Bunchgrass Prairie in the United States. Applied Vegetation Science 23:53-68. Johnson, R.L. 2008. Impacts of habitat alterations and predispersal seed predation on the reproductive success of Great Basin forbs. Dissertation. Brigham Young University. Kulmatiski, A. 2006. Exotic plants establish persistent communities. Plant Ecology 187(2):261- 275. Kwaiser, K.S., and S.D. Hendrix. 2008. Diversity and abundance of bees (Hymenoptera: Apiformes) in native and ruderal grasslands of agriculturally dominated landscapes. Ecosystems and Environment 124:200-204. Moissett, B., and S. Buchanan. 2010. Bee basics: an introduction to our native bees. USDA, Forest Service. Morris, L.R., Monaco, T.A., and R.L. Sheley. 2011. Land-use legacies and vegetation recovery 90 years after cultivation in Great Basin sagebrush ecosystems. Rangeland Ecology and Management 64(5):488-497. Morris, L.R., Monaco, T.A., and R.L. Sheley. 2014. Impact of cultivation legacies on rehabilitation seedings and native species re-establishment in Great Basin shrublands. Rangeland Ecology and Management 67(3):285-291. Potts, S.G., Biesmeijer, J.C., Kremen, C., Neumann, P., Schweiger, O., and W.E. Kunin. 2010. Global pollinator declines: trends, impacts and drivers. Trends in Ecology and Evolution 25(6):345-353. 86

Robson, D.B. 2019. Impact of grazing history on pollinator communities in Fescue Prairie. Blue Jay 77(1):10-15. Roof, S.M., DeBano, S.J., Rowland, M.M., and S. Burrows. 2018. Associations between blooming plants and their bee visitors in a Riparian Ecosystem in Eastern Oregon. Northwest Science 92(2):119-135. Steffan-Dewenter, I., Potts, S.G., and L. Packer. 2005. Pollinator diversity and crop pollination services are at risk. Trends in Ecology and Evolution 20(12):651-652. Taylor, R.V., and H.J. Schmalz. 2012. Monitoring of upland prairie vegetation on the Zumwalt Prairie Preserve 2003-2011. The Nature Conservancy, Enterprise, OR. Taylor, R.V., Ball, D.A., and J. Fields. 2012. Zumwalt old field rehabilitation: Status, effectiveness of treatments, and future plans. The Nature Conservancy, Enterprise, OR. Tisdale, E.W. 1982. Grasslands of western North America: the Pacific Northwest Bunchgrass. British Columbia Ministry of Forests, Kamloops, Canada. 232-245. US Fish and Wildlife Service. 2007. Recover plan for Silene spaldingii (Spalding’s catchfly). Washington, DC: US Fish and Wildlife Service.

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APPENDIX

100

A.1 Coordinates of 16 permanent plots on the Zumwalt Prairie Preserve that are part of the long- term prescribe fire and grazing study (Chapter 2).

Site Treatment Latitude Longitude Elevation (m) 1BOTH Both 45° 32.306' N 116° 57.664' W 1432 2BOTH Both 45° 32.536' N 116° 57.354' W 1442 3BOTH Both 45° 33.599' N 116° 58.908' W 1390 4BOTH Both 45° 35.658' N 116° 56.529' W 1410 1BURN Burn 45° 32.148' N 116° 57.632' W 1463 2BURN Burn 45° 32.697' N 116° 57.486' W 1414 3BURN Burn 45° 33.433' N 116° 59.008' W 1397 4BURN Burn 45° 35.745' N 116° 56.512' W 1416 1CNTL Control 45° 32.693' N 116° 56.290' W 1504 2CNTL Control 45° 33.076' N 116° 56.803' W 1463 3CNTL Control 45° 33.732' N 116° 57.116' W 1442 4CNTL Control 45° 34.571' N 116° 56.386' W 1415 1GRAZ Graze 45° 32.414' N 116° 56.715' W 1494 2GRAZ Graze 45° 33.445' N 116° 56.741' W 1446 3GRAZ Graze 45° 34.133' N 116° 57.028' W 1429 4GRAZ Graze 45° 34.959' N 116° 56.636' W 1393

101

A.2 Coordinates of the 16 plots on the Zumwalt Prairie Preserve that are part of the native prairie (NP) and seeded old-field (SOF) study (Chapter 3).

Site Treatment Latitude Longitude Elevation (m) NP1 Native Prairie 45° 33.256' N 116° 58.555' W 1397 NP2 Native Prairie 45° 32.560' N 116° 58.759' W 1427 NP3 Native Prairie 45° 35.889' N 116° 58.679' W 1396 NP4 Native Prairie 45° 35.787' N 116° 57.768' W 1375 NP5 Native Prairie 45° 34.979' N 116° 57.179' W 1376 NP6 Native Prairie 45° 34.465' N 116° 57.459' W 1401 NP7 Native Prairie 45° 34.571' N 116° 56.386' W 1415 NP8 Native Prairie 45° 34.959' N 116° 56.636' W 1393 SOF1 Seeded Old-Field 45° 32.940' N 116° 58.652' W 1404 SOF2 Seeded Old-Field 45° 32.726' N 116° 58.859' W 1419 SOF3 Seeded Old-Field 45° 35.660' N 116° 58.576' W 1394 SOF4 Seeded Old-Field 45° 35.763' N 116° 58.000' W 1377 SOF5 Seeded Old-Field 45° 35.152' N 116° 57.456' W 1376 SOF6 Seeded Old-Field 45° 34.687' N 116° 57.439' W 1381 SOF7 Seeded Old-Field 45° 34.649' N 116° 56.975' W 1382 SOF8 Seeded Old-Field 45° 34.724' N 116° 57.202' W 1376

102

A.3 Forb species encountered along transects in Chapter 3 study, check marks indicate which sample month each species was in bloom.

Forb Species June July August Lithophragma glabrum   Collinsia parviflorum   Draba verna   Montia linearis   Myosotis stricta   Triteleia grandiflora   Phlox viscida   Zigadenus venenosus   Balsamorhiza incana   Frasera albicaulis   Collomia linearis   Microsteris gracilis   Senecio integerrimus   Microseris nutans   Lomatium triternatum   Delphinium nuttallianum   Astragalus sheldonii   Castilleja tenuis   Antennaria luzuloides   Erigeron chrysopsis   Castilleja cusickii   Potentilla glandulosa   Antennaria rosea   Erigeron speciosus   Crepis sp.    Geum triflorum    Potentilla gracilis    Arnica sororia    Lupinus sp.    Trifolium hybridum   Hieracium cynoglossoides   Pyrrocoma carthamoides   Sedum stenopetalum   Packera cana   Veronica arvensis   Rosa woodsii   103

Galium boreale   Orthocarpus tenuifolius   Eriogonum heracleoides   Clarkia pulchella   Potentilla recta   Achillea millefolium   Descurainia incana   Madia gracilis   Calochortus eurycarpus   Arenaria congesta   Agoseris glauca   Sidalcea oregana   Agoseris heterophylla   Geranium viscosissimum   Castilleja lutescens   Dianthus armeria   Madia glomerata   Epilobium brachycarpum   Erigeron pumilus   Silene spaldingii   Chrysothamnus viscidiflorus  Grindelia nana  Cirsium brevifolium  Cirsium vulgare  Perideridia gairdneri  Solidago missouriensis  Lactuca serriola  Vicia villosa 