Yellowstone National Park

Wyoming, Montana, Idaho

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Volume 28, Issue 1 olume 28, Issue 1

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ellowstone Sc

THE GRAZI
Yellowstone Science

Volume 28, Issue 1January 2022

Submissions to Yellowstone Science are welcomed from conducting formal research in the Greater Yellowstone Aacceptance is based on editorial board review for clarity, ctechnical and scientific soundness, and relevance to Natiopolicy. All photos are from the National Park Service unless noted The opinions expressed in Yellowstone Science are the 

not reflect either National Park Service policy or the views Center for Resources. Copyright @Yellowstone Forever 20Please visit our website for futher information on submittto the editor, viewing back issues, and to become a digita2020, Yellowstone Science is no longer printed in hardcwww.nps.gov/yellowstonescience

Guest Editor: Dr. P.J. WhiteGuest Editorial Board: Dr. Chris GeremiaStefanie WackerManaging Editor: Charissa ReidTechnical Editor:Karin BergumDesign: Charissa Reid
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Table of Contents

Conserving Yellowstone’s Northern Range ....... The Great Debate: Are Yellowstone’s Northern Grasslands Overgrazed? ..................................... History & Status of the Yellowstone Bison Population ..........................................................How Do Yellowstone’s Ungulates Make a Home on the Range? ........................................Are Northern Yellowstone Rangelands Healthy or Degraded? ....................................................Give Bison Room to Roam ...............................Sagebrush Steppe Monitoring ........................ Women in Science: Mary Agnes Chase ...........Controlling Invasive Weeds in Yellowstone ... Managing Grassland Communities in Northern Yellowstone ...................................................... Interview: Dr. Douglas A. Frank ...................... 

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Wildlife in Yellowstone: What to Preserve? .............................In Memoriam: John Maxwell GSpecies in this Issue ................Being an Effective Leader .......Literature Cited .......................Sneak Peek ..............................
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Natural resource managers in Yellowstone National Park face many challenges that will continue into the future. Visitation has doubled over the past several decades, making it more 

difficult to avoid disturbances to vegetation, waterways, and wild animals. A warming climate is affecting precipitation and snowmelt patterns, the frequencies of droughts, flooding, and fires, and plant and animal communities. Development of some areas surrounding the park continues to fragment habitats for wildlife and alter their movements. In addition, nonnative plants are spreading into the park and displacing native plants in some areas. As a result, managers need to continue working with residents, states, tribes, visitors, and the national public to consider a variety of ideas and find reasonable responses. One pressing issue is how to manage grasslands and migratory ungulates in northern Yellowstone and nearby areas of Montana. Thousands of bison and elk and hundreds of bighorn sheep, deer, and pronghorn move across this “northern range,” where they interact with bears, cougars, coyotes, and wolves. This area provides one of the best places in the world to watch wildlife. Since the 1920s, however, there have been concerns about too many ungulates removing too much vegetation, eroding soils, and reducing the variety of plants. In addition, nonnative plants have taken over portions of this range, raising concerns about their effects and continued spread. There is a need to develop realistic goals and feasible approaches for managing grasslands and grazing animals on the northern range. Since 2012, park biologists and various collaborators have increased monitoring of grassland and sage-steppe communities to gauge conditions, document plant production and grazing consumption, assess soil health, and describe the composition of native and nonnative plants. In this edition of Yellowstone Science, we describe findings from these efforts and recommend future actions. 

Conserving Yellowstone’s Northern Range

Wildlife & Aquatic Reso
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The Great Debate: Are Yellowstone’s Northern Grasslands OveP. J. White, Chris Geremia, Rick Wallen, Doug Frank, & Roy Renkin

Many people refer to the grasslands in northern Yellowstone as America’s Serengeti because they support a wide variety of abundant ungulates and their predators watched by 

millions of people each year. However, this concentration of grazing animals has been a source of controversy since the 1920s due to concerns about them removing too much vegetation, compacting soils, and reducing the diversity of plants. As a result, managers reduced numbers of bison, elk, and pronghorn during the 1930s through the 1960s by shooting or capturing and removing them from the park. Managers stopped these culls when there were about 3,170 elk, 70 bison, and 100 pronghorn in northern Yellowstone and nearby areas of Montana. Thereafter, managers allowed ungulate numbers to vary in response to forage availability, harvests outside the park, predation, and weather. Numbers increased rapidly with counts of about 18,900 elk, 940 bison, and 495 pronghorn by the late 1980s. 

As their numbers increased, more ungulalower-elevation valleys outside the park dsome people to conclude there was not efor existing numbers of animals. This led toverabundant elk were permanently damovergrazing and compacting or eroding tAppropriations Committee directed the Ncontract an independent review of this issCouncil (NRC) published their findings in Ecological Dynamics on Yellowstone’s Noconcluded grazing had not permanently dand, as a result, natural fluctuations in ungrassland and grazing conditions could cocautioned that future predictions were difclimate, wolf reintroduction from 1995 to north of the park during winter, and the cungulates outside the park. Thus, they rec
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conduct monitoring and research over the next several decades to determine the effects of these changes. Counts of northern Yellowstone elk decreased by 80% to 3,915 in 2013 (Figure 1) and, in turn, the debate about overgrazing by elk waned. However, bison counts in northern Yellowstone increased to 3,420 by 2014 and intense grazing in the Lamar Valley rekindled the debate about grazing effects. This change towards fewer elk and more bison was unprecedented in recent history and, as a result, the long-term effects of bison grazing on grassland communities were uncertain. Unlike elk and other ungulates, bison are constrained by surrounding states from moving much beyond the boundaries of the park due to concerns about disease transmission to livestock, competition with cattle for grass, human safety, and property 

damage. Thus, the substantial increase in concerns that intense grazing could damaYellowstone. Grazing EffectsThe debate about the management of grgrasslands in northern Yellowstone hingeis overgrazing. Grazing usually is not destpermanently damage plants or decrease tof energy. The growth of new plant tissue sunlight and carbon dioxide from the air aother minerals from the soil. Low to modcan increase plant production in areas witnutrients by removing some leaf tissue, wto reach the plants and reduces water losleaves (McNaughton 1985, Knapp et al. 1increase the availability of nitrogen in the in the form of feces and urine and breakihelps roots and associated fungi intake nal. 2013 and references therein). As a resin grasses is increased and, provided there there is an increase in the production of nthis process, ungulates can increase plant quality of forage (McNaughton 1985, Fratoo much grazing can decrease plant promuch leaf tissue, exposing and compactinnutrients, and decreasing the variety of preferences therein). Excessively grazed areand invasions by nonnative plants due to bare ground (Pellant et al. 2005). Given this background, we suggest overgwidespread, repeated foraging removes splant productivity and regrowth decrease 

Figure 1. Winter counts of northern Yellowstone elk (triangles) and summer counts of bison (squares) in the northern portion of Yellowstone National Park from 1998 to 2019 (Geremia et al. 2018, NYCWWG 2018).
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become unproductive and eroded (Pellant et al. 2005, Fuhlendorf et al. 2012, NRC 2013). Signs of overgrazing include changes in the variety of plants, the spread of nonnative plants, and poor body condition in ungulates. However, deciding whether an area is overgrazed is complicated and depends on a person’s experiences, training, and goals. Rangeland managers usually view grazing as a tool for livestock production with substantial human involvement to maintain desirable forage plants. Thus, they focus on indicators of grassland health such as plant composition, the amount of litter, soil erosion, and whether grazing is moderate and uniform (Fuhlendorf et al. 2012). In contrast, wildlife biologists view grazing as a process that contributes to a variety of animals, plants, and conditions across the landscape. Thus, they focus on indicators such as plant production, energy and nutrients, the diversity of animals and plants, and ungulate body condition (Fuhlendorf et al. 2012). As a result, rangeland managers and biologists often evaluate the same grazed landscape and reach different conclusions regarding its condition. Yellowstone National Park (YNP) is not a ranch with domesticated animals and human-controlled animal, nutrient, and water inputs. Rather, the park preserves a wilderness where untamed, free-roaming animals and natural processes exist in an area not dominated by humans. Since ungulate numbers vary considerably among seasons and years, quite unlike the stocking and rotation of livestock on rangelands and grazing allotments, the grasslands within the park will not look like nearby ranches. The NRC addressed this issue in their 2002 report: "For example, some people compare the northern range unfavorably with nearby ranches, but that reflects a mixing of values. Ranching seeks high production for human uses, but YNP seeks to preserve a natural environment and the species and ecological processes within it." Today, most deer, elk, and other ungulates in the Yellowstone area move from lower elevations during winter to higher elevations during summer. They eat mostly dead, low quality forage during 

winter, but select newly growing, green gareas during spring. They then move to hmelts to find more-abundant, nourishing season progresses. These movements alloregrow new tissue and store energy in theplants to withstand modest levels of grazet al. 2013). However, large aggregations graze certain areas for long periods of timare restricted, which is the case with Yellosurrounding states have little tolerance fomost bison remain within the park (Gerembison tend to create grazing lawns, similasavanna systems of the Serengeti, unlike scattered manner (McNaughton 1985). Hbison graze in the Lamar Valley through smove through this area to more distant sual. 2010, Geremia et al. 2015). Intense, suin this area would subject grasses to repeaffect plant productivity. Desired and Existing ConditionsCongress established YNP in 1872 to presnatural condition for the benefit and enjonatural condition for vegetation and wildwould be pre-settlement, before substantEuro-Americans. However, it is impossible conditions given ensuing changes such as removal of native people, development avisitation, invasions by more than 217 typspecies, and a century of a warming climaTercek et al. 2015, Hansen and Phillips 20Ungulates were widespread in the Yellowsettlement during the late 1800s (Whittlemassive slaughter of wild ungulates by m
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relocation of American Indians to reservations, thousands of livestock (cattle, horses, and sheep) were allowed to graze grasslands in northern Yellowstone from about 1875 to 1922 and nearby areas of Montana through the 1900s (Whittlesey 1994). After removing livestock from the park, grazing in northern Yellowstone primarily occurred during winter and spring by wild elk, bison, and other ungulates, with animals moving between higher elevations during summer and fall and lower elevations during winter. In recent years, however, more than one thousand bison have remained in the Lamar Valley and nearby areas throughout the summer (White et al. 2012, Geremia et al. 2015). Between 1904 and 1952, about 575 acres (233 hectares) in the Lamar Valley, 530 acres (215 hectares) in the Gardiner basin, and some areas along Slough Creek and in Yancey's Hole were cleared of native vegetation and planted with nonnative grasses (alfalfa, oats, smooth brome, clover, timothy) to grow hay for bison, elk, pronghorn, and other wildlife (Figures 2 and 3; Cahalane 1944, Whittlesey 1995). Managers eventually planted nonnative crested wheatgrass in the hayfields in the Gardiner basin. Sufficient moisture in the higher-elevation hayfields allowed smooth brome and timothy to expand substantially beyond the originally planted fields. A warming climate with high nitrogen deposition from feces and urine from ungulates allowed nonnative plants to spread in the following decades (Renkin et al. 2014). For example, annual wheatgrass, cheatgrass, and desert alyssum spread through the Gardiner basin during the 1990s and 2000s, replacing crested wheatgrass on previously farmed fields and filling in spaces between native bunchgrasses (Renkin et al. 2014). In addition, nonnative plants spread along roads where soils were disturbed, in areas burned by fires, and elsewhere from feces deposited by wildlife, packhorses, and mules. This spread has changed the composition and production of some grassland communities by displacing native plants and altering productivity, soils, and nutrients (Renkin et al. 2014). 

Nonnative plants now dominate plant comthe Gardiner basin and Lamar Valley (YCR Climate is the main factor affecting grass variations in precipitation and temperaturmoisture, which can limit production (Fravariations in weather among years contribin grass production (Knapp and Smith 20warmed and precipitation has decreased about 80 to 100 more days above freezinof the park compared to 1985 (Tercek et have resulted in less snow at lower elevatplant growth, longer and drier growing sedrought (Tercek et al. 2015, Hansen and Fewer green grasses may be available in loccurs earlier and grasses die by mid-sumungulates may be unable to obtain adequfor pregnancy and survival (Middleton et that are more frequent could make grasslvulnerable to the spread of nonnative gra2015, Hansen and Phillips 2018, YCR 201The recovery of large predators such as wcougars during recent decades contributethe numbers and distribution of grazing uand more bison, and a much greater portmoving to lower-elevation areas outside tThese changes occurred, at least in part, dof elk at higher elevations where they wedeeper snow packs (White et al. 2012). Togroups of elk use the grasslands in northeof their feeding occurs during nighttime wactive (Kohl et al. 2018). In contrast, bisoYellowstone increased from about 900 to 
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Figure 2. Map of the cultivated hayfields and other vegetation types in the Lamar Valley of Yellowstone National Park during 1932-1933
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Figure 3. Map of the cultivated hayfields near the town of Gardiner, Montana, in Yellowstone National Park during 1904. 

2017 due to high survival and calving combined with movements of bison from the central to the northern region of the park. As mentioned previously, these bison began using traditional winter range areas for elk in the Lamar Valley as summer grazing areas 

(Geremia et al. 2015). Bison are more diffielk due to their large size and use of grouthey can congregate in large groups in grpredation risk. 
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ConclusionGiven all of these changes over the past century, a more realistic desired condition for grasslands in northern Yellowstone, rather than attempting to recreate the natural conditions before EuroAmerican colonization, is to try and maintain communities with functional groups of grasses, forbs, and shrubs, healthy soils, and functioning water, energy, and nutrient cycles. Many communities will include widespread nonnative plants due to their previous spread throughout much of northern Yellowstone. In addition, variable grazing intensities will produce an assortment of vegetation conditions across the landscape ranging from lightly to intensively grazed areas. This mosaic will support a diversity of animals and plants because some need a variety of different areas, while others rely on either disturbed or undisturbed areas (Fuhlendorf et al. 2012, NRC 2013). Since 2012, wildlife biologists have monitored changes in plant production, consumption, soil health, and plant composition across the ranges used by Yellowstone bison. In addition, vegetation biologists have monitored plant composition in sagebrush-steppe communities to detect changes in the abundance of native and nonnative plants, bare soil and litter, and other indicators. The articles in this edition of Yellowstone Science summarize findings from these monitoring efforts and provide recommendations for the future. Literature CitedSee Literature Cited section of this issue on page 108.P.J. White (see page 4) is the Chief of Wildlife and Aquatic Resources at Yellowstone National Park. He has researched many of the major mammals in the Greater Yellowstone Area and worked to find solutions that help wildlife and humans coexist. White is the author of more than 100 scientific papers and many popular books, 

including Can’t Chew the Leather AnymoConservation in Yellowstone from a BrokeYellowstone’s Mountain Ungulates—A CoHistories and Challenges, Yellowstone Griand Conservation of an Icon of Wildness, 

Conserving an American Icon in Modern S

Wildlife in Transition, and The Ecology of 

Yellowstone: Sixteen Years of Integrated F
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History & Status of the Yellowstone Bison Population

P. J. White, Chris Geremia, & Rick Wallen

Protection and Recovery By 1900, there were only two dozen bison left in the Yellowstone area due to their widespread slaughter by 

Euro-American colonists during the 1870s and 1880s. To help with recovery, managers relocated 18 pregnant females from northwestern Montana and 3 males from Texas to the northern portion of Yellowstone National Park (YNP) during the early 1900s. Managers fed these bison during winter at the Buffalo Ranch in the Lamar Valley and herded them to the Mirror Plateau and upper Lamar River area during summer. The remaining native bison spent winter in the Pelican Valley in central Yellowstone, but also moved to the Mirror Plateau and upper Lamar River area during summer. As a result, some of the native Pelican bison likely mixed and bred with the introduced Lamar bison during the breeding season from midJuly to mid-August. Bison numbers increased rapidly to about 1,100 by 1930 (Figure 1). In 1936, managers relocated 71 bison from the Lamar Valley to the Hayden Valley and Firehole River area in central Yellowstone, creating the Mary Mountain herd (Meagher 1973). Managers stopped feeding and herding bison in the Lamar Valley in 1952, after which bison moved about freely. However, managers shot or captured and shipped about 3,500 bison from this herd between 1930 and 1966 to reduce numbers and take out individuals with the disease brucellosis. For similar reasons, managers removed about 860 Mary Mountain bison and 150 Pelican bison between 1954 and 1966. These removals reduced numbers to about 70 Lamar, 160 Pelican, and 188 Mary Mountain bison by winter in 1968 (Meagher 1973). Thereafter, managers stopped removing bison and allowed numbers to vary in response to forage availability, predation, and weather. Bison numbers increased rapidly to about 1,700 during the 1970s and 3,000 during the 1980s. Some Lamar bison began spending both summer and winter in the Lamar Valley, while others pioneered winter ranges westward along 

Photo: ©Clint Parkhillthe Yellowstone River towards the northe1989). Pelican bison began moving west Yellowstone Lake and along the YellowstoValley (Figure 2). Eventually, bison spendinValley stopped moving to the Mirror Plate
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Figure 1. Counts and removals of Yellowstone bison from 1901 to 2018. IBMP refers to the Interagency Bison Management Plan. area during summer and, instead, mostly remained in the Hayden Valley (Meagher 1998). Thus, there was likely considerable mixing of descendants from the native (Pelican) and introduced (Lamar/Mary Mountain) lineages. In addition, some bison began moving from the Hayden Valley to the Firehole River area and along the Gibbon and Madison rivers towards the western boundary during winter. Others began moving to northern Yellowstone, likely in response to increasing bison numbers and deep snow depths that reduced forage availability (Meagher 1993, Fuller et al. 2007). As a result, there was probably further mixing of descendants from the native and introduced lineages and distinguishing between descendants of Lamar, Pelican, and Mary Mountain bison based on their location in the park 

became impossible. Instead, biologists beto bison that spent summer in the centraYellowstone as the central and northern hInteragency Bison Management Plan When bison began moving outside YNP dmanagers began hazing, capturing, and sconcerns about the transmission of bruceBy 1994, bison numbers increased to abo3,000 bison in central Yellowstone and latowards the park’s northern and western captured and shipped more than 1,000 bsevere winter of 1997. There were a seriemoving outside the park allegedly put Mo
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at risk from brucellosis outbreaks and trade restrictions. By December 2000, managers developed a management plan that allowed a few hundred bison to move into small, adjacent areas of Montana during winter, provided they did not mix with cattle. Through the mid-2000s, bison tended to move from central Yellowstone to the western boundary of the park during winter. As a result, hazing actions to keep them within the park were more common at this boundary than in the north. There were about 3,500 bison in central Yellowstone and 1,500 bison in northern Yellowstone during the summer of 2005. Since then, there has been a large decrease in the number of bison in central Yellowstone, a rapid increase in the number of bison in northern Yellowstone, and more movements of bison from central to northern Yellowstone 

Figure 2. Winter (December-February) distribution of locations from radio-collared, adult, female bison during 2004-2012, with white areas showing increased use and arrows showing the direction of most movements (Geremia et al. 2015).

(Wallen and White 2015). These movemeto high bison numbers in central Yellowstthe western boundary, and groomed roadrapidly travel to the north during winter (there was a decrease in numbers of elk in about 19,000 in the mid-1990s to 3,915 restoration of predators such as bears, conumbers declined, the number of bison in increased from about 1,500 in 2005 to 4,contrast, the number of bison counted in decreased from about 3,500 in 2005 to aHunters and managers removed more tha2008, and 2017-2018, primarily females move to the park boundary more than mIn recent years, most bison in central Yellosummer in the Hayden Valley. Many of thalong the Firehole, Gibbon, and Madison of Montana (Hebgen Basin), while others Yellowstone. Most bison in northern Yellosummer in the Lamar Valley and adjacent downslope to the Blacktail Deer Plateau aduring the winter (Geremia et al. 2015). Sand shipments of bison to slaughter have northern boundary of the park, while haroutside the western and northern boundashoot more bison near the north boundaGenetic Diversity Yellowstone bison have high genetic dive2007, Hedrick 2009). The introduction of Valley from different genetic lineages thacontributed to this diversity and, at least idifferences between bison living in the ce
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regions of the park. Bison sampled near the western and northern boundaries of the park during winters from 1997 to 2003 had somewhat different genetic make-ups (Halbert et al. 2012). These differences were a bit surprising given the mixing of descendants from the native and introduced lineages for many decades. Bison wintering in the Pelican and Lamar valleys used the same areas during the summer beginning in the 1920s and, in the mid-1930s, managers relocated descendants from the introduced Lamar lineage in northern Yellowstone to the Hayden Valley and Firehole River area in central Yellowstone. Bison from this Mary Mountain herd began mixing and breeding with bison from the Pelican Valley with the native lineage during the 1980s (Meagher 1998). Regardless, since the mid-2000s there have been increasing movements of bison between central and northern Yellowstone that have further mixed descendants of the introduced and native lineages throughout the central and northern regions of the park. For example, two-thirds of adult females fitted with radio-collars in central Yellowstone during 2004 to 2017 moved in groups with hundreds of other female and young bison to northern Yellowstone during winter. About half of these collared females remained in northern Yellowstone at least through the breeding season the following summer. In addition, bison sampled in central and northern Yellowstone during 2011-2012 did not have distinct genetic make-ups. Rather, the native and introduced lineages were found in both areas in about equal proportions (Forgacs et al. 2016). We are continuing studies to further evaluate genetic diversity and the distributions of the historic bison lineages. Literature CitedSee Literature Cited section of this issue on page 108.

In 2018, Rick Wallen retired from a careeService. For 17 years, he was the team leand Management Program in the YellowsHe worked to gain more space for bison tYellowstone landscape, so they could play more meaningful scale. Rick collaborated show bison could be allowed more freedoquickly transmitting brucellosis to nearby NPS staff and cooperating agencies has lehanded management practices of the pasfor quarantine and relocation of live surpthrough a partnership with the AssiniboinPeck. During his tenure at Yellowstone the bison population increased from 2,000 to 4,500 individuals. Rick initiated efforts to study the ecological influence of bison grazing on Yellowstone grasslands as the population doubled in size following the implementation of the Interagency Bison Management Plan in December 2000.
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How Do Yellowstone’s Ungulates Make a Home on the RangeLauren McGarvey & Chris Geremia

Yellowstone National Park is home to many ungulates, including bison, bighorn sheep, elk, mule deer, and pronghorn. These ungulates are herbivores (only consume 

plants) and depend on grasslands for food. They move across the landscape in search of food, but grasslands are a limited resource. Biologists have long been interested in how similar species (types) of animals coexist when food resources are limited. Species may compete with one another if they use limited resources similarly, resulting in decreased nutrition, body condition, survival, and reproduction. However, species may lessen competition and coexist by partitioning food resources, such as consuming different plants and using areas at different times. We are studying the movements and diets of different ungulates in Yellowstone to determine how they make a home on the range – do they compete with one another or partition resources to coexist? This article provides our preliminary findings.Migration and RangesMigration is the seasonal movement between two distinct, and often distant, ranges. Biologists have proposed several theories to explain why ungulates migrate, such as enhancing access to high quality forage, avoiding predation, and preventing grasslands from being overgrazed (Fryxell and Sinclair 1988). In Yellowstone, ungulates migrate along elevation gradients in response to snow accumulation or melting. In spring, ungulates follow a green wave of new, highly nutritious vegetation growing as snow melts from low-elevation winter ranges to high-elevation summer ranges. In fall, ungulates return to low-elevation winter ranges where less snow accumulates and food is more accessible.We use global positioning system (GPS) collars to document ungulate movements. Collaring ungulates requires a tranquilizer gun and immobilization drugs (Figure 1). Once we immobilize an animal, we fit it with a GPS collar and release it. The newly collared 

Figure 1. Biologists fitting a female pronghorn w
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animal continues its natural movements, and now we know its daily locations. We use these locations to create a detailed map of the animal’s migration and ranges.Bighorn sheep, elk, mule deer and pronghorn have similar migration strategies. These species tend to have distinct ranges they migrate between during spring and fall. When these species migrate, they take a direct path between ranges with a few stops along the way to “refuel.” The individual bighorn sheep, elk, mule deer, and pronghorn migrations illustrated in Figure 2 lasted between 3-21 days. Once these animals reached their seasonal range, they stayed in a relatively small geographic area for the rest of the season. Bison migrate differently than other ungulates in Yellowstone. Bison are more nomadic and stop to graze areas while they migrate. For example, the individual bison illustrated in Figure 2 migrated from Blacktail Deer Plateau to Lamar Valley, up the Lamar River drainage, returned to the Lamar Valley, and then moved to the Hayden Valley. Her migration from Blacktail Deer Plateau to Hayden Valley lasted 77 days. Instead of having distinct ranges, bison wander throughout their migration. The article titled “Give Bison Room to Roam” in this volume explains why bison migrate differently than other ungulates. During summer, most ungulates use high-elevation areas where new, highly nutritious vegetation grows. Bison and pronghorn use grasslands in Lamar Valley, while bison also use grasslands on the Mirror Plateau and in the Pelican and Hayden valleys (Figure 3). Bighorn sheep use meadows on the mountain ridges surrounding Lamar Valley and in the Gardiner basin. Elk and mule deer use meadows and forests throughout Yellowstone. The most overlap in summer range occurs between bison and pronghorn (Table 1). Bison summer range overlaps with 76% of pronghorn summer range, whereas pronghorn summer range overlaps with 26% of bison summer range. The percentage of overlap varies between bison and pronghorn because bison collectively have a very large summer range, whereas pronghorn have a very small summer range. 

FiinelYe

Figure 3. Daily locations of GPS-collared bighorn spronghorn by season. Each point represents a GPfrom July to September; winter locations are from 
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During winter, most ungulates use low-elevation areas where less snow accumulates in northern Yellowstone and north of the park (Figure 3). The most overlap in winter range occurs between pronghorn and bison (Table 2). Bison winter range overlaps with 83% of pronghorn winter range. Bison overlap with the majority of pronghorn winter range because pronghorn use a very small winter range in northern Yellowstone and the Gardiner basin. Bison winter range also overlaps with 71% of mule deer winter range and 72% of bighorn sheep winter range. As with pronghorn, these species use small winter ranges in northern Yellowstone and the Gardiner basin. In addition to northern Yellowstone, bison also use areas in the Hayden Valley and the Firehole and Madison River drainages during winter.Diet Composition and Overlap Diet composition is the proportion of different plant species consumed by ungulates. Biologists have found diet composition varies considerably among ungulates, especially those that primarily 

Species Bighorn Sheep Bison Elk Mule Deer Pronghorn

Bighorn 

Sheep (6) 1.00 0.06 0.05 0.12 0.10

Bison (7) 0.12 1.00 0.08 0.13 0.76

Elk (6) 0.08 0.06 1.00 0.10 0.00

Mule Deer 

(5) 0.13 0.07 0.08 1.00 0.04

Pronghorn 

(4) 0.08 0.26 0.00 0.03 1.00

Table 1: Proportion of summer range overlap between species. For example, pronghorn summer range overlaps with 26% of bison summer range and bison summer range overlaps with 76% of pronghorn summer range. The numbers of radio-collared animals are in parentheses.

Table 2: Proportion of winter range overlap betwedeer winter range overlaps with 6% of bison wintoverlaps with 71% of mule deer winter range. Thanimals are in parentheses.

Species Bighorn Sheep Bison Elk 

Bighorn 

Sheep (6) 1.00 0.05 0.1

Bison (8) 0.72 1.00 0.3

Elk (6) 0.23 0.06 1.0

Mule Deer 

(5) 0.09 0.06 0.0

Pronghorn 

(4) 0.30 0.07 0.0

browse and those that primarily graze (M1986). Browsers primarily consume forbs and shrubs, while grazers primarily consuare ungulates that consume both browse and grazers typically vary in body size, mophysiologies. Large-bodied ungulates typivegetation, such as grass, because it is pleenergetic demands and digests efficiently stomachs. Small-bodied ungulates typicalvegetation, such as forbs, because these smaller stomachs. We study diet composition by collecting fgroups of ungulates with at least one anithat provides spatial information. Laboratfecal samples using a technique called miplace a portion of the fecal sample on a mit under a microscope, and identify specieWe analyze diet composition seasonally b
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availability of plants. Grasses and forbs are abundant and easily accessible during the summer. These plants become dormant and covered by snow during the winter, making them scarcer and less accessible. As a result, some ungulates consume shrubs and conifers that are more accessible.During the summer, bighorn sheep, bison, and elk primarily consumed grasses (Figure 4). Bighorn sheep and bison preferred bluebunch wheatgrass, bluegrass, and Idaho fescue. Elk preferred bluegrass as well, but also consumed a high proportion of reed grass. Mule deer and pronghorn primarily consumed forbs. Both species preferred geranium, but mule deer also preferred lupin. In addition to forbs, pronghorn preferred shrubs such as big sagebrush. Bison, elk, and mule deer also consumed a considerable amount of 

sedges during the summer.During the winter, bighorn sheep, bison, (Figure 4). Elk and mule deer consumed msuch as juniper and Douglas fir. Unlike the pronghorn consumed a high proportion oduring the winter.We assess diet overlap by comparing how are among different ungulates using ordi2015). Ordination creates a simple plot frdata. Diets plotted closer together are moplotted further apart. Diet variation within closeness of individual diets. Species with together in plots (smaller ellipses) have lesspecies with individual diets spread apart There was less overlap in diet among ungsummer (Figure 5). Bison and elk, which gmost overlap in diet. However, bison are mbison (indicated by the tight clustering of have more variation in diet (indicated by tPronghorn, which primarily browse forbs overlap in diet with the other ungulate spthe most variation in their diet compared species.There was more overlap in diet during the bighorn sheep, bison, and elk, which prim(Figure 6). As in the summer, bison are mbison whereas elk have more variation in primarily grazing grasses as in the summein the winter. Mule deer and pronghorn adiet with the other ungulate species durin

Figure 4. Stacked bar plot of ungulate diets (i.e., vegetation type consumed) determined by examining fecal samples.
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What Do Yellowstone’s Ungulates Eat?

DiscussionWe observed the greatest overlap in summer range among bison and pronghorn. Many bison and pronghorn use the Lamar Valley during summer. Bison primarily graze on grasses whereas pronghorn primarily browse on forbs. Because bison and pronghorn consume different foods, there is little potential of competition between the two species even though they use similar spaces. Pronghorn may even benefit from using similar summer range as bison. Bison preferentially graze on grasses and avoid forbs, which make up a very small percentage of their diet (Knapp et al. 1999). By preferentially grazing on grasses, bison enable forbs, the primary food of pronghorn, to flourish (Knapp et al. 1999). Biologists observed a similar relationship in the Serengeti of east Africa. Over one million wildebeest, a grazer that aggregates in large groups like bison, migrate across the Serengeti Plains following rainfall. 

Wildebeest graze and remove the majoritbiomass as they migrate (McNaughton 19substantial numbers of Thomson’s gazelle(McNaughton 1976). The intense grazing promotes grass growth and creates a denthat Thomson’s gazelles feed on during th1976). Instead of competing, Thomson’s as wildebeest for their benefit. We observed the most overlap in winter rsheep, mule deer, and pronghorn with biwinter range, whereas bighorn sheep, muhave much smaller winter ranges. Bison aarea of Yellowstone during winter becausearly to avoid deep snow (Kauffman et al

Summer1. true sedges2. bluebunch wheatgrass3. Idaho fescueWinter1. bluebunch wheatgrass 2. true sedges3. Idaho fescue

Summer1. forbs2. big sagebrush3. geraniumWinter1. big sagebrush2. whitlow-grass3. bluebunch wheatgrass

Summer1. true sedges2. annual meadow grass3. reed grass or smallweedWinter1. bluebunch wheatgrass2. annual meadow grass3. Idaho fescue

Summer1. true sedges2. lupine3. cranesbill or geraniumWinter1. big sagebrush2. juniper3. Douglas fir needles

BISON

DEER ELK PRONGHORN 
Yellowstone Scien

Figure 5. Diet overlap among ungulate species during the summer. Species plotted closer together are more similar in diet than species plotted farther apart. Points are individual diets and ellipses are drawn around all the diets within a species. There were too few points to draw an ellipse around mule deer diets.

use their massive heads like shovels to access forage beneath deep snow. If snow conditions become too harsh, bison will migrate to the low-elevation areas used by other ungulates. This accounts for the large overlap of bison winter range with bighorn sheep, mule deer, and pronghorn winter ranges. Even though these species use similar winter ranges, there is little potential for competition among bison, mule deer, and pronghorn because they consume different foods. Bison primarily graze on grasses, whereas mule deer and pronghorn primarily browse on conifers, forbs, and shrubs. There may be potential for competition between bighorn sheep and bison because they consume similar foods, but we need more data before we can make this determination. Biologists suspected competition between bighorn sheep and elk when almost 20,000 elk used northern Yellowstone (Singer and Norland 1994). Now that bison numbers have increased and elk numbers have decreased, bison may be competing with bighorn sheep when range is limited during the winter. However, it is important to note that competition 

does not occur simply because there is spFor competition to occur, resources must bison, elk, and pronghorn have increased suggesting resources are not currently limabundance has remained stable, but this are competing with other ungulates becafactors limiting their abundance. For examcompeting with each other for the limited they depend on to escape predators.We observed the greatest overlap in diet both of which are large grazers, but little previous study of ungulate relationships in overlap in winter range between bison an1994). However, this study occurred befogray wolves and there were more than 20Yellowstone. Ten years after the reintrodupopulation numbered 6,500 individuals. E

SUMMER WINTER
22

Representative bison migration. This bison roamed throughout her migration instead of having a distinct route or completely separate winter (brown) and summer (purple) ranges. Representative elk migration. This elk migrated 191 km between her winter (brown) and summer (white) range over 21 days.

BISON MULE DEER

ELK PRONGHORN

Yellowstone Ungulate Migration Patterns
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In Yellowstone National Park, ungulates migrate following elevational gradients to access forage. Ungulates move from higher elevations where nutritious vegetation grows during summer to lower elevations where less snow accumulates during winter. We typically think of ungulates having distinct summer and winter ranges they migrate between each spring and fall. However, not all ungulate migrations are this simple. Bison wander throughout their migration instead of having distinct summer and winter ranges. This results in bison traveling farther and utilizing greater areas than other ungulates. The bighorn sheep, elk, mule deer, and pronghorn had geographically small summer and winter ranges they migrated between. The bison, however, utilized much larger summer and winter ranges with no distinct migration between them.

Representative bighorn sheep migration. This bighorn sheep migrated 54 km between her winter (brown) and summer (purple) range over 7 days.

BIGHORN SHEEP
24

wolves, and wolf predation has resulted in fewer elk wintering in the Lamar Valley where wolf abundance is high (White et al. 2012). Bison experience far less wolf predation because of their large size and group defense strategies (bison group up to defend themselves instead of running away) which enables them to use areas of Lamar Valley during the winter that elk no longer use (White et al. 2015). Elk now primarily use winter range north of Yellowstone in the Gardiner basin and Paradise Valley where predator abundance is lower (White et al. 2012). Bison also use winter range in the Gardiner basin, but the State of Montana does not allow them to access winter range in the Paradise Valley because of concerns about disease transmission to cattle (White et al. 2015). Consequently, bison and elk have less overlap in winter range than previously reported.Overall, our results suggest competition is not currently limiting the abundance of ungulates in Yellowstone. During the summer, ungulate species use different areas, with the exception of bison and pronghorn, which alleviates potential competition among them. Because bison increase plant biomass and diversity, pronghorn may benefit from using similar summer range as bison. During the winter, ungulates are concentrated in low-elevation areas of northern Yellowstone and beyond the northern boundary. However, variation in winter ranges, timing of migration, and diets alleviates potential competition among ungulate species. It appears that Yellowstone’s ungulate species make a home on the range by partitioning resources to coexist with each other.Literature CitedSee Literature Cited section of this issue on page 108.

Lauren McGarvey is a wildlife biologist wManagement program in Yellowstone Naan undergraduate degree in Biology from a Master of Science degree in Fish and WMontana State University.
Yellowstone Scien

Collecting fecal samples from radio-collared ungulates (up to 75 animals) takes a lot of effort. To accomplish this task, biologists from the National Park Service work collaboratively with citizen scientists through Ecology Project International, Yellowstone Conservation Corps, and Yellowstone Forever. Citizen scientists locate collared animals throughout Yellowstone to collect group demographic information on sex and age composition, and fecal samples. Our partnerships with citizen scientists enable us to implement a largescale research project and teach students about ungulate ecology and conservation in Yellowstone.

Bison fecal sample collected by citizen scientists (PInternational)

Citizen scientist using radio telemetry to locate collared bison (Photo: Ecology Project International)

Citizen scientists classifying bison by sex and age International)

Citizen Science
26

Are Northern Yellowstone Rangelands Healthy or Degraded?

Chris Geremia & Bill Hamilton

There is no shortage of opinions about the numbers of bison and elk in Yellowstone and their effects on the vegetation. There is an ongoing scientific debate about what defines 

healthy rangelands and whether there are too many bison in the park. We began a landscape-level study of grazing in northern Yellowstone in 2012 and have completed 10 years of field research. The core 

We are studying soil health and plant community productivity to evaluate concerns that bison degrade grasslands in northern Yellowsto

of our work revolves around 30 sites in nowhere there is frequent grazing. Each site square meters) in size and includes differeexclosures. We measure soil health, plant and plant community composition. We are hoping to add clarity to a long deabundant herbivores (plant eaters) have npermanently damaged the vegetation in n
Yellowstone Scien

Decades of disagreement culminated in a congressionally mandated assessment of the health of northern Yellowstone during the late 1990s. The conclusions, published in 2002, indicated northern Yellowstone was not facing imminent ecological collapse. Some riparian and lower elevation sagebrush habitat had fundamentally changed in response to high browsing by elk. However, these independent scientists recommended park managers continue the policy of minimal management of elk, bison, and pronghorn within the park. They highlighted changing climate as the greatest threat to the integrity of northern Yellowstone and recommended park managers reassess the grazing system in 10 to 15 years (NRC 2002). Grazing ecosystems are places where wild grazers and plant species have lived together for thousands of years. They are the most imperiled ecosystems on the planet. Slowly evolving, finely tuned relationships among soils, plants, and grazers make these ecosystems healthy even when they are grazed (Frank et al. 1998). By healthy, we mean these systems can sustain nutrient, energy, and water transfer (Holechek et al. 1989, Briske 2011). If the question is whether grazers, previously elk and currently bison, reduce ecosystem health, how do you determine if nutrients, energy and water are being transferred properly? The answer is to look at the soils and plants, because they create a nutrient and energy supply that can be transferred to all other organisms in the ecosystem (Pyke et al. 2002, Pellant et al. 2005). It boils down to two simple questions: are soils sustainable and are plant communities maintaining productivity.

Are there too many bison? Bison are ecosystem engineers that move and graze across the land to intentionally create hotspots, areas of high grazing, which improves their own food quality. Some areas are grazed more intensely than they would be if we intrusively controlled grazing in the park.
28

Elk dominated conversations about the health of Yellowstone for decades. During the 1930s, photographs of thYellowstone valleys, like the Lamar Valley, showed narrow swaths of willows, aspens, and cottonwoods that streIncreasing elk populations during the second half of the twentieth century coincided with the decline and eventcommunities. This abrupt change became the fodder for debates over whether elk overgrazed Yellowstone.Those claiming overgrazing pointed to the disappearance of woody vegetation. Others rebutted those claims by recovery with predator recovery, and testing if wolf recovery could alter elk abundance, movements, and feeding allowing willow, aspen, and cottonwood to regrow (Peterson et al.2020).However, we might not be looking at the right measure of overgrazing. It’s flowering plants, not woody riparian the Yellowstone grazing ecosystem. Grasslands dominate northern Yellowstone. Flowering plants, including grasshowy flowers dominate grassland plant communities. Flowering plants not only make up the overwhelming bunorthern Yellowstone, particularly compared to riparian woody vegetation, but they also make up the majority oElk primarily feed on flowering plants, which make up more than 95% of summer and 75% of winter diets. On riparian vegetation makes up less than 1% of summer and about 2% of winter diets. Bison also prefer flowering 97% of diets. Make no mistake, riparian areas are very important to ecosystems. So is the massive amount of research dedicatextent to which wolves and other predators indirectly contribute to woody plant growth. However, if the questiograzing ecosystem of northern Yellowstone is stable, grasslands and shrublands should be the focus of assessme

Overgrazing or Over-browsing?
Yellowstone Scien

If we managed Yellowstone like a ranch, the first thing we would do is figure out how many animals northern Yellowstone could support without diminishing the productivity of the plant communities. This takes estimating the amount of plant material produced within northern Yellowstone and the food requirements of each animal. Standard practice is to have enough animals to eat about 50% of the plant material. Some plant material is unavailable for grazing because it is lost to trampling, defecation, and bedding. Thus, the “take half, leave half” approach, which was long considered the preferred strategy for sustainable grazing, equates to having enough animals to eat about 25 to 50% of the total plant material produced each year. We used state-of-the-art technology to analyze satellite images and estimate the amount of plant forage produced across northern Yellowstone. In an average year, northern Yellowstone produces about 165 to 172 million pounds (74 to 78 million kilograms) of plants. The entire park produces around 426 million pounds (193 million kilograms), almost two and half times that amount. Moreover, our estimates are conservative. We could only estimate plant production in non-forested areas, because satellites cannot see through trees. Plants growing in partly forested areas were not included, which provide an unknown additional amount of forage. It is hard to believe, but an adult female bison eats between 400 and 1,000 pounds (180 to 455 kilograms) of plants each month, which equates to about 9,600 pounds (4,355 kilograms) of plants each year – 4.8 tons (4,355 kilograms) of plant material for each adult female each year. Bison of different ages and sex eat different amounts of forage. Calves, for example, eat very little forage while they are nursing. Larger males eat upwards of 5.5 tons (4,990 kilograms) of forage each year. The age and sex composition of bison in northern Yellowstone is about 35% adult males, 35% adult females, 13% juveniles, and 

17% calves. Given this age and sex structcan support at least 5,000 bison based on approach. That is just in northern Yellowssupport at least twice that number. When looking across all grazing animals ithere are about 3,500 bison, 7,500 elk, 5mule deer, and 500 bighorn sheep, equatpounds (1.3 to 1.8 million kilograms) of gtogether, all these animals still do not mabiomass to take half and leave half of the However, Yellowstone is not a ranch. The premised on the idea of uniform grazing, the right time. In Yellowstone, animals gewhen they graze. They have developed fito move and graze across the land to get need to raise young, survive harsh winterNature decides who lives and dies and the strategies are passed on among generatiowho migrate with the green wave in early their movements and letting it pass them lawns, areas of particularly intense, repetiplant growth allowing them to continue t(Geremia et al. 2019). We used radio-collars to map the intensitnorthern Yellowstone each month of the maps by the number and composition of monthly estimates of the numbers and tyarea of northern Yellowstone. From these the number of used Animal Unit Months available Animal Unit Months. When you they do not uniformly graze areas in nortthey use about 81% of the area at lower 
30

T

PLANT PRODUCTIONis the amount of plant material made each year and is estimated using satellite imagery, and collecting and weighing plant material.

An ANIMAL UNIT (AU) is a 1,000 

pound animal. Age and body size is used to determine animal unit equivilents (AU). A 2,000 adult male bison is 2 AU.

How We Determine Carrying CapacityTo estimate the number of bison that the northern range could sustain, we collected Yellowstone-specific data. To determine AU, we weighed bison across age and sex classes. To determine PLANT PRODUCTION, we used satellite imagery to estimate plant composition and ground-truthed our estimates by creating grazing plots where we collected plant growth and analyzed it’s nutritional content. We also used GPS-collared bison to track grazing activity across a grid and quantified how much time bison spent in each section of the northern range. 

This information is used to calculate AUMMONTHS). An AUM is 800 pounds of plants - the amsustain a 1,000 pound bison over the cou

2 AU

A 2,000 

AU) req

each m

AUM

BIson decide where and when to graze. Tmigrations to move and graze across the food needed to raise young, survive Yelloavoid predators. Bison graze different parts of the landscalivestock, whose grazing is controlled by rpastures, bison do not graze following a “strategy. This strategy, considered ideal by about 50% of available plant production Yellowstone is NOT a ranch. Across the noabout 81% of areas lighter, 9% of areas more intensely than a take half-leave half 
Yellowstone Scien

Number of bison Percent (

1,000 2,000 3,000 4,000 5,000 

10,000 

Bison Population StatusThree thousand to 4,000 bison migrate across the northern range. The population is made up of about 35% adult males, 35% adult females, 13% juveniles, and 17% calves.Using all the data gathered and what we know from overflights about the composition of the northern herd, we reached the following conclusion: the northern Yellowstone produces enough herbaceous plant material each year to support more than 5,000 bison.intensity, and 10% at higher intensity. Our challenge is to evaluate these areas of high use and determine whether bison grazing is sustainable. We analyzed soils by studying the top 4 to 8 inches (10 to 20 centimeters) inside and outside of small exclosures set up at each grazing site. We evaluated soils every month of each growing season to account for seasonal effects on soil nutrients, water holding potential, and microorganisms.Soils in our grazing study sites contain approximately equal proportions of sand, silt, and clay. These names refer to particle size. The smallest particles are clay, larger particles are silt, and the largest are sand. Soils that have relatively equal proportions of sand, silt, and clay best support plant growth. The different sized particles leave spaces for air and water to flow and roots to penetrate, with enough sand to drain, and enough clay and silt to hold moisture and retain soil nutrients. We did not detect soil compaction based on bulk density, which is less than 1.2 grams per cubic centimeter in all sites. Soil cores taken within wallows showed differing levels of compaction. Wallows are bedding areas, devoid of plants, that animals use to dust themselves for cooling, avoiding insects, and scent marking. 

How Many Bison Can Northern Yellowstone Support?

Soil pH ranges from slightly acidic to slighpH 8 at all sites. Nutrients enter the soil in unavailable to plants. Microbes convert nplant-friendly inorganic forms. Some inorand phosphate are negatively charged anabsorbed by plants or leached away becanegatively charged and like charges repel nutrients are neutral or positively charged ammonium, respectively. Positively chargeto negatively charged soil particles, which for plants. Soils with lower than pH 8 fac(ammonia) inorganic nutrients to positiveinorganic nutrients, which then allows theSoil microbial biomass averages 72 grams meter suggestive of abundant microbial ptypes of microbes feed on different types It is important to not only have diverse mbut soil nutrients in relative concentrationpopulations that feed on different soil comcarbon and nitrogen in soil organic matteto support nitrogen and carbon consuminboth nutrients in relative abundances nec
32

Soil organic matter is a single measure of soil health that captures the physical (particle size, bulk density, water holding capacity), chemical (pH, nutrient concentration), and biological (microbial populations) properties (Briske 2011). It is the fraction of the soil made up of decaying plant and animal tissue. Soil organic matter is the sponge of the soil, soaking up and holding water, microbes, and nutrients. In agriculture, fertilizer is used to augment soil organic matter when levels fall below 2 to 3%. Soil organic matter exceeds this level in northern Yellowstone, averaging 13% across sites. 

SOIL ORGANIC MATTER (SOMcomposed of decaying plant anWhy is it important? It links the chemical properties of soils as a health. SOM supports microbescapacity, and is the entry route In agricultural, the goal is to mand use fertilizer to support lanGrazing Site Averages:• SOM averages 13% and ra• Plant production increases w• Short-term 3-year removals 

effect on SOM

• Comparisons inside and ou

exclosures show long-term 

• Bison change the source of 

matter to animal waste

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Soil organic matter provides a quantitativWind and water runoff hold the potentiahorizons, which contain the greatest propmatter. Healthy soils show long-term stabShort- and long-term exclosure experimennutrient-rich equilibrium. Short-term rest matter. We installed 3-year exclosures and in soil organic matter inside or outside exexperiment. We also analyzed soil organic exclosures set up nearly 60 years ago. It wmatter measured outside those exclosures 
Yellowstone Scien

It is a common practice in agriculture to spread manure on fields to increase soil nutrients, primarily nitrogen and phosphorous, which then improves plant productivity. Migratory animals such 

as bison and elk do the spreading on a much broader scale and seasonal variations in snowpack and rainfall influence their migratory patterns. In 2016, my students and I collaborated with students from Ecology Project International to conduct transect surveys for bison and elk dung across their migratory ranges. At each site, we established at least ten 1-meter by 100-meter transects in which dung was collected and weighed. The total sample size was more than 400 transects for bison and 50 transects for bison and elk combined. We only collected dung that was not bleached and still contained moisture. A “freshness scale” was assigned to dung and samples were taken across the scale for analysis of water content, extractable nitrogen, phosphorous, and total carbon and nitrogen. We found the only difference between samples in the freshness scale was moisture content. Carbon to nitrogen ratios in organic matter control the fate of carbon and nitrogen during decomposition. Organic matter with ratios higher than 30 to 1 are nitrogen limited and, therefore, decomposers immobilize nitrogen while breaking down carbon bonds. When carbon to nitrogen ratios are less than 25 to 1, nitrogen can be mineralized and become available in inorganic forms that primary producers can use for growth. Our sampling showed that the carbon to nitrogen ratio of bison and elk dung varied through the season and that bison and elk dung differed across all sampling points except during April and May (Figure 1). The carbon to nitrogen ratio of dung is correlated with the carbon to nitrogen ratio of the forage entering an animal. As ruminants, elk are classified as grazers and intermediate feeders because they consume grasses, forbs, and browse, and the composition of the diet varies with season. Bison are classified as grazers because most of their diet 

Bison and Elk DungBill Hamilton

Figure 1. Total carbon to nitrogen ratio in bisdung across five time periods in a calendar yFigure 2. Total extractable phosphate in bison dung across five time periods in a calendar y
34

is grasses with minimal forb and browse consumption (Vallentine 2001). Based on the carbon to nitrogen ratios of dung in elk and bison, both species generate dung during April to September that is favorable for providing nitrogen to plants for growth. Phosphorous is an important plant macronutrient and exists in soils in forms that are not readily available to plants. Analysis of water extractable phosphate, which is the oxidized inorganic form of phosphorous taken up by plants, in elk and bison dung showed there is seasonal variation in dung phosphate levels. Bison and elk dung have similar seasonal trends, but elk dung has less phosphate from mid-July to March (Figure 2). The differences are likely the result of diet selection. More than 300 transects for collecting bison dung were at seven sites across northern Yellowstone. Using the transect data, we estimated the density of bison dung patties at each site during the growing season (April-September) and found it ranged from 145 to 462 patties per hectare. From this estimate, the amount of cumulative extractable phosphate and nitrogen in dung can be estimated across the seven sites. Phosphate ranged from 1.1 to 4.8 kilograms per hectare and nitrogen ranged from 7.2 to 26.2 kilograms per hectare. Dung deposition is a major contributor to these values, but seasonal variation in dung quality (Figures 1 and 2) also contributes to the differences across sites. The Lamar Valley and slopes between Cache and Calfee creeks are sites with high productivity that have higher grazing intensities, while sites in the Gardiner basin, Blacktail Deer Plateau, Hellroaring Mountain slopes, and Crystal Bench near the base of Specimen Ridge are lower in productivity and used during migration in spring and fall (Figure 3.)This snapshot in time of bison and elk dung provides interesting results about the importance of herbivore dung as manure in 

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Yellowstone grasslands and suggests mordone. My students will be observing bison behavior to understand the frequency and In the laboratory, we will conduct soil incuinvestigate the effects of dung on decomand the microbial communities responsib
Yellowstone Scien

PHYSICAL PROPERTIES of soils can promote plant growth. Soils with large (sand), moderate (silt), and small (clay) particle sizes are LOAMY SOILS which allow water and root infiltration while holding water and nutrients for plant uptake. • Grazing Site Averages:

Loam (44%), Sandy-Clay-Loam (44%), Clay-Loam (8%), and Sandy-Loam (4%) 

• Bulk density: < 1.2 grams per 

cubic centimeter indicating soils are not compacted.

OM N

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CHEMICAL PROPERTIESSoils with less than pH 8 promote plant gcharging inorganic nutrients, which bind particles. Binding nutrients to soil particleGrazing Site Averages:• pH ranges 5.2-7.7 which is well within 

for existing native plants

• Plant available nitrogen averages 40 m

OM

BIOLOGICAL PROPERTIESDiverse and abundant microbial populatiointo inorganic nutrients. It is important to microbial populations that feed on differematter and break down different types of Grazing Site Averages: Microbial biomagrams per square meter. Soil carbon to niwithin a range of 5-18 which supports camicrobes.

Why Does Soil Matter?
36

Soil properties and weather create four habitat types for grassland and shrubland plants in the areas used by bison in northern Yellowstone. The habitat types vary by elevation and 

topographic position and we refer to them as mountain meadow, valley floor, valley slope, and low-elevation range. Plant communities are arrangements of plants that typically grow together. Plants must absorb soil nutrients, water, and sunlight to grow. Different plants have unique rooting depths, leaf area, height, life form, lifespan, growing season, and ways to reproduce. These attributes are called functional traits. Healthy plant communities contain a wide range of functional traits, which enables them to optimize productivity across the community (Funk et al. 2017).Each habitat type supports its own set of plant communities, because plants are adapted to grow best under certain conditions. Nature makes plant communities dynamic. Forces like drought, disease, grazing, and fire slightly modify conditions making them better for certain plants. Some species grow better under the new conditions and proliferate while others decline; a process called plant succession. Plants that grow better after disturbance are called early successional stage (early seral); those that grow best long after disturbance are called late seral. Changes do not tend to be dramatic or permanent. They shift the relative abundance of species.Too much disturbance can fundamentally change everything. It can push plant communities across a threshold. By doing so, the existing communities disappear and are replaced by entirely new, undesired ones. Thresholds are one-way roads. It is very difficult to return to the original plant communities once a system passes a threshold.In concept, the theory of plant community dynamics we just described (Pyke et al. 2002, Stringham et al. 2003, Briske et al. 2005) sounds very simple. In practice, it is very difficult to apply. It takes monitoring systems for a long-time, including observing systems as they cross thresholds. 

What are sustainable soils?Soils store massive amounts of nutrients. concentration of important nutrients exisFor soils, sustainability means long-term sbank. For this to happen, soils must be ahold on to them to prevent their leaching absorption and retention require certain saeration, and the correct chemistry and snutrients. What is sustainable productivity?Plants uptake soil nutrients and convert troots using water and sun energy. For plasustained plant community productivity. Nthe amount of new plant tissue made ovseason. Plant communities optimize prodsoil nutrients in different ways. Plants havtraits, which set how they extract and use maintain optimal production, plant commbroad arrangement of functional traits amthat make up the community.

These models do not exist for northern Yethe reason why there is so much debate. same habitat and speculate whether it is They can base their opinions on their own not really have any data to support it. We to create plant community models for noscientists a common lens to look at rangeTypically, one starts by measuring the samtime and tracking plant community shifts intensity. We did not have this chance, be

Habitat Types
Yellowstone Scien

plant community conditions in sites starting in 2016. That led us to substitute time for space, by comparing plant communities across sites with similar soil conditions, but with different grazing intensities. In other words, we looked at areas where we expected the same plant communities, determined they were different, and asked how grazing related to those differences.We measured plant composition by recording species abundance in sixty 20-by-50-centimeter (8-by-20-inch) plots within each grazing site. We used four traits to determine the functional grouping of 225 plant species we identified. We used life form – graminoid (grass, rush or sedge), shrub, or forb (showy flower); life span – annual or perennial; growth form – bunchgrass or rhizomatous (rootstalks); and rooting depth – shallow, moderate, or deep. Combinations of traits identified 21 different functional groups. We looked at plant communities by seeing how they were composed of these 21 functional groups (Lavorel et al. 1997).We first tested if each habitat type (mountain meadow, valley floor, valley slope, low-elevation range) had their own unique set of plant communities. It turns out they did. We also tested the similarity of plant communities within each habitat type. It turns out they were more similar to each other than they were to communities found in other habitat types. This is what you would expect in a healthy system that has not experienced thresholds and undesired changes. 

Otherwise, we would have found some ctype that were very different from the othtype.  The one exception was a single site in thhas passed a threshold. The site located nstation is the low-elevation range habitat the warm-season nonnative desert alyssuanalyses cannot identify the trigger or cauto cross a threshold. However, it confirms habitat type can transition from bunchgrawinter-annual communities. As expected, the plant communities withnaturally varied. Grazing generally increasforms and forbs, and decreased moderate bunchgrasses and shrubs. Similar to how repeated grazing by bison by removing older plant tissue and stimulshoots (Geremia et al. 2019), grazing madyounger by reducing their stage of plant scommunities changed from deeper rootemore diverse communities of shallow-roogrowth- and rooting-forms. Four of our gduring the 1980s (Frank and McNaughtosimilar successional changes. We did not detect strong differences amoof plant communities based on successionplant communities within each habitat tyintensities had higher productivity. In othemodified plant communities and those coproductive than others in the same habitagrazing sites monitored during the 1980s similar to slightly higher productivity toda
38

A. MOUNTAIN MEADOW• Soils: nitrogen-rich, clay-loam• Climate: cold and wet• Productivity: 200-300 grams per square meter, 1,700-2,600 

pounds per acre

• Plant Communities: shrubs, grasses and showy flowers• Dominant Functional Groups: shallow rooted perennial forbs; 

shallow and moderate rooted perennial bunchgrasses; perennial rhizomatous sedges; moderate rooted perennial forbs

• Example Habitat: high meadows above Lamar Valley• Dominant Plants: timothy grass, dandelion, Idaho fescue, tuftedhairgrass, cinquefoil, oatgrass, brome, creeping clover, dandelion

B. VALLEY SLOPE

• Soils: nitrogen-available, sandy• Climate: cool and dry• Productivity: 50-150 grams per square 

per acre

• Plant Communities: bunchgrasses, shr• Dominant Functional Groups: shallow 

perennial bunchgrasses; shallow, modperennial forbs; perennial rhizomatoushrubs

• Example Habitat: slopes around the La• Dominant Plants: Idaho fescue, blue-b

grass, Sandberg’s bluegrass, needle-anphlox, milkvetch, sagebrush, rabbitbru

Northern Yellowstone has four distinct habitat types used by bison. Each supports it’s own set of related plant co
Yellowstone Scien

C. VALLEY FLOOR • Soils: nitrogen-rich, loamy• Climate: cool and wet• Productivity: 200-450 grams per square meter, 1,700-4,000 

pounds per acre 

• Plant Communities: grasses and showy flowers• Dominant Functional Groups: perennial rhizomatous grasses; 

shallow and moderate rooted perennial forbs; shallow and moderate rooted perennial bunchgrasses; annual forbs 

• Example Habitat: floor of the Lamar Valley• Dominant Plants: Kentucky bluegrass, timothy grass, smooth 

brome, creeping clover, dandelion.

D. LOW ELEVATION• Soils: nitrogen-poor, loamy• Climate: warm and dry• Productivity: 50-150 grams per square 

acre 

• Plant Communities: bunchgrasses and 

annual infestations

• Dominant Functional Groups: XX• Example Habitat: previously cultivated • Dominant Plants: crested wheatgrass, 

wheatgrass, big sagebrush, XX
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Cattle thrive on landscapes not recently disturbed by grazing or fire. Rangeland management developed in response to excessive livestock grazing and farming that led to wide-scale habitat destruction during the early twentieth century. The principles of rangeland management are still applied to managing most public lands today: manipulate grazing by managing the number of animals using an area for set amounts of time, evenly distributing use, grazing the right type of animal, and grazing the plants at the right time. The goal is to protect soils by minimizing disturbance to plant communities (Holechek et al. 1989, Briske 2011). 

Aplant community consisting of a wide range of native plants that collectively has a wide range of function

Communities with nonnative plants can be just as healthy. We do not mean that weeds are good. We methat plant communities maintain species representing broad sets of functional traits rather than species of 

some nonnative plants can fulfill functional roles, others can be devastating, fundamentally changing the integrity Cool-Season Nonnative Invasions: Cool-season nonnatives replaced native plants throughout the cool, wet, nitrognorthern Yellowstone. These species include Kentucky bluegrass, timothy grass, smooth brome, creeping-clover, ahabitat type plant communities are primarily made of cool-season nonnatives. Mountain meadow habitat types cwith mixtures of native and exotic plants. Cool-season nonnatives are well adapted to live in the higher elevations northern Yellowstone. They inefficiently use water to grow, which requires them to live in wet areas. Cool-season introduced to the park to support bison restoration. They thrive when grazed, which likely contributes to their disCool-season nonnatives also tend to be more productive than displaced native plants. As a result, some grasslandare likely more productive today than they were when the park was established.Warm-Season Nonnative Invasions: Warm-season nonnatives, including desert alyssum and cheatgrass, are graduand dry low-elevation range habitat type. They hold potential to displace native plants and unbalance the functiocommunities. These plants grow in dry soils, where there is intense competition for moisture. Winter annuals can on native plants by sprouting in the fall. Already germinated winter annuals can monopolize early spring pulses onative plants. The abundance and distribution of winter annuals will likely depend on how much northern Yellowthe future. Under some climate scenarios, these plants could disrupt plant communities throughout the low- and habitat types in northern Yellowstone.

Back when bison roamed North America completely changed ecosystems. The storlikely one of disturbance driven by massivintense grazing. In the wetter, eastern Grbison populations show that animals folloareas after fire to eat nutrient-enriched pof fire and grazing changes plant commuIn the western foothills of the Great Plainset up grazing lawns so large that satellitgrazing effects on plant growth patterns 

How Do Different People Come to Different Conclusions?

Are Nonnative Plants Bad? It Depends.
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plant communities and nutrient flows between plants and animals (Geremia et al. 2019).Therein lies the cause for debate about the health of vegetation in northern Yellowstone. When grazing changes plant communities, is it success or catastrophe? For decades, many have looked at northern Yellowstone in the context of whether the right plant communities are still there. The original lens through which we looked at rangeland health were tools like the Similarity Index and Trend Analysis. They measured how far existing plant communities differed from hypothetical climax communities, which were the plants likely present in precolonial time. We determined early seral communities were unhealthy and referred to them as rangelands in poor condition. Those lenses have changed over time as we recognized that plant communities are more complicated than we originally thought. Today, the standard is to use something called Rangeland Health Assessment. However, we still compare existing conditions to some form of idealized plant community, which still tends to be late seral communities. The more we understand grazing ecosystems, the more we realize it is time to let nature decide which plant communities exist. Relationships among plants and grazers protect these systems, stabilizing nutrient supplies within soils and enabling plants to be productive in the face of grazing.National Park Service policies provide enough flexibility to manage for preserving natural processes, like nutrient cycling, plant succession, migration, competition, and predation. However, the debate over northern Yellowstone always drifts back into discussions of values. Rather than looking at the health of northern Yellowstone through the lens of whether natural processes are playing out, it turns into discussions of whether we should let them happen.People define their values by the time they are teenagers. Values affect our interpretation of the world. Values are that inner voice 
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SOILS and WEATHER determine the types of plant communities that could live in an area. FUNCTIONAL TRAITS of plants determine their growth potential.PLANT COMMUNITIES are groups of plants that grow together with each plant type having unique functional traits such as rooting depth, lifespan, growth form, and life form.Identify soil PHYSICAL, CHEMICAL, and BIOLOGICAL properties to 

classify habitat types for plants. 1. Evaluate the top 10-20 centimeters2. Identify microbial diversity, nutrient mineralization rates, bulk density, particle composition, and pHSOIL ORGANIC MATTER is the amount of decaying plant and animal materials in soils and a general indicator of nutrient and water holding capacity. 1. Maintain similar soil organic matter levels over decades. SOIL NUTRIENT POOLS are the concentration of limiting nutrients (nitrogen, carbon) in soils. 1. Stabilize soil nutrient concentrations over decades. 

PLANT COMMUNITIES

naturally shift back and forth 

due to mild disturbance. 

P

A

Too much disturbance can cause plant coTHRESHOLD. 

Track the functional integrity of PLANT C1. Evaluate plant community composition traits.2. Maintain similar plant communities in a3. Support plant communities across seraPLANT PRODUCTIVITY is the amount of each year. 1. Maintain similar productivity of plant carea, even with shifts in plant community 2. Track plant production using empirical measuring conditions throughout the grograzed areas. 

Plant Communities
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Chris Geremia (see page 52).Bill Hamilton has worked on how grasse

to herbivory since he was an undergraduaaboveground and belowground interactiobegan late in graduate school working wYellowstone grasses. Since 2004 he has bundergraduate students on a variety of Yeto restoration, soil health and grass-grazehe has been collaborating with the grazinphysical, chemical, and biological propertconducting greenhouse studies on grasse

speaking to you as you read our article reminding you “wow, of course bison grazing improves the park,” or “wow, that’s another case of bad science.”When you visit the park, ask yourself if the areas are overgrazed. Values may lead you, at the sight of bison, to think of the icon of the American west and presume they are a natural part of the ecosystem that can do no harm to the land. On the other hand, your values may make you see short plants, dirt wallows, habitat destruction, and ornery versions of cattle. Most of you are likely somewhere in between. For too long this debate has been about gotcha moments: look what we just found, clearly northern Yellowstone is (or is not) overgrazed. Science is not meant to be point and counterpoint. Science is supposed to be about presenting observations for assessment by our peers, while also providing methods to repeat those observations. Rather than figuring out the next gotcha moment, it’s time to move on from this gamesmanship.What is at stake is our national mammal, how we manage it, and its’ home. We need to stick to less of our individual values and start making assessments based on the principles of the National Park Service, which are to create a place for these natural processes to play out. If we can agree that is our goal, almost everyone that is looking at what we are looking at would come to the same conclusion. Habitat across northern Yellowstone is predominantly stable. Soils are healthy and nutrient-rich. Plant communities are productive in the face of grazing. The biggest challenge we have is a changing climate because warmer and drier weather may allow certain nonnative plant invasions that could break the balance of the grazing ecosystem.Literature CitedSee Literature Cited section of this issue on page 108.
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Give Bison Room to Roam

Chris Geremia, Bill Hamilton & P. J. White

When park visitors imagine the world-renowned grasslands of northern Yellowstone, many see the idyllic scene of a Thomas Moran painting. A river slowly wanders across 

the valley floor, lined with pockets of willows and cottonwood trees. Tall, waist-deep grasses and mountain wildflowers wave in the wind. Snowcapped mountains backdrop the valley. Small, widely scattered groups of deer, pronghorn, and elk graze where the grasslands meet the forests. The scene today does not disappoint, but it is probably different from what many visitors expect. It is a relic of North America prior to European settlement when bison dominated the continent. Make no mistake; there is nothing wrong with this scene. In fact, allowing large groups of bison to naturally migrate and graze improves the health of grasslands in northern Yellowstone.Up to four thousand bison graze across northern Yellowstone. Measured by sheer body size and numbers, there is more bison ‘mass’ than any other large grazing animal. Unlike deer, pronghorn, or elk, bison immediately include their young into their large traveling groups. As spring turns to summer, traveling groups become larger, reaching hundreds to thousands of animals. Aggregation concentrates grazing and creates a mosaic of dense mats of short-statured plants that look like golf course fairways interspersed with small islands of waist-high, yellowed, dried-up grasses. Dung piles pepper the land like pieces on a checkerboard. Wallows, bison-sized depressions devoid of plants created from them rolling on the ground, pit the dense mats of grazed plants. Most large grazers follow the “green wave” of sprouting plants and grasses during spring because young plants are highly nutritious (Merkle et al. 2016). For example, mule deer move up to 200 miles (322 kilometers) in southern parts of the Yellowstone ecosystem, tracking highly nutritious foods that are vital to their surviving winter. 

Bison migrate and graze in Lamar Valley during spof nature acting as ecosystem engineers that impnorthern Yellowstone. 
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Bison set the terms of spring in Yellowstone. Without several thousands of bison moving freely on the landscape in sync, the springtime be shorter, the land would not be as green, and the plants would not be as nutritious. Bison constantly hit reset on springtime by intenssame areas. Their intense grazing does not weaken plants but stimulates plants to regrow after being partially eaten. As bison graze on they obtain a similar diet to what other grazers, like elk and mule deer, get by migrating in sync with plants as they emerge in spring. Migrating bison begin surfing the green wave early in spring. Many bison stop and let the green wave pass them by, not reaching their final summer ranges until weeks after green-up occurred. As it turns out, bison can move out-of-sync with forage green-up because they engineer the ecosystem as they migrate and graze. Rather than just moving to find the best foods, bison create high-quality foods by how they move and graze (Geremia et al. 2019). They walk and graze, back and forth, across nearly 20 miles (32 kilometers) of the Lamar River as the green wave continues up into the mountains. Their behavior creates grazing lawns, a term popularized during the 1980s to describe intense, broad-scale grazing by millions of wildebeest in the Serengeti (McNaughton 1984). As bison let the green wave go by, they become a massive fleet of lawnmowers moving back and forth across northern Yellowstone. At a time when plants are actively growing, they form aggregations of hundreds to thousands of animals. This behavior sets bison apart from other large grazers in Yellowstone. 

The aggregations are dynamic. Bison do nsame group or location for very long. Statshow that animals cyclically move across tsame areas about every two to three weein northern Yellowstone, which numbers many of the same areas although not necmay look like the same bison are always iis not the case. Bison are always on the mTo think bison are just aimlessly eating grathat regrow after intense grazing provide newly emerging spring shoots. In other wplants are more nutritious than more matBy grazing en masse and returning to the plant growth to get the same types of higget if they surfed the green wave (Gerem
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Grazing preserves soil moisture by improving plant water-use efficiency (Frank et al. 1998, 2018). Plants face a trade-off. Plants lose water to the air when they open small pores called stomates on their leaves to suck up water from the soil and absorb carbon dioxide from the air. Plants require both water and carbon dioxide to make new plant tissue through a process called photosynthesis. Short dense plants with less leaf surface area lose less water, which prolongs moist soils. Grazing improves soil nutrient availability. Animals deposit carbonbased organic matter on the soil surface in the form of dung and urine. Organic matter is critical to soil health. It acts like a sponge absorbing water. Organic matter also provides habitat to soil microbes that are the link to plants obtaining nutrients. Plant roots cannot immediately absorb soil nutrients stored in organic form. Soil microbes must first break them down into simpler inorganic structures. Intense grazing leads to more animal-based organic matter on the soil surface, which leads to robust soil microbial populations, and creates a bountiful supply of soil nutrients in forms available to plants (Hamilton and Frank 2001). Grazing also causes older roots to die and replaces them with younger roots that are better at absorbing nutrients (Hamilton et al. 2008). Through these mechanisms, grazed plants have soil, water, and nutrients available for them to regrow. Plants do not just regrow from the bitten off grass tips. They also produce entirely new shoots off the root crown, the part of the plant immediately below the soil surface (Frank et al. 1998). This process of tillering, growing new shoots from the crown, creates the short, dense mats of vegetation that characterize grazing lawns. New, young tillers are high in nutrients and low in indigestible matter. When bison return to bite off the new tillers, they eat the equivalent of newly growing spring vegetation.

Nutrient-rich shoots lead to nutrient-rich nutrient-rich soils. Grazing accelerates the back to plants. Nitrogen and phosphorus the ecosystem as they move back and forinorganic forms. Grazing reduces tying up in decaying plant matter and litter. This mthe sources of phosphorus and nitrogen f(dung) origins (Hamilton and Frank 2001)animal-based sources of organic material sources, making phosphorus and nitrogen growing plants. One might think all this grazing reduces pbecause plants exist in low, dense mats. Timagine doing a science experiment on yolet the plants grow for the entire summertime, collect the plant clippings, and place other side, you mow the lawn every weekcollect the plant clippings and place them pile will have more plant material? The shgenerated from mowing each week weigIf grazing increases plant growth, it just mof grassland ecosystems. Plants play the cthe sun’s energy and converting it into foorganisms. Plants do this by fixing carbonthe sun’s energy in carbon-to-carbon bonof sugar. From plants, energy flows up thherbivores graze plants and predators conmore plant material means harnessing moGrazed grasslands, more productive than more energy and a greater potential to suand robust ecosystem. 
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Grazing accelerates nutrient flow and creates a healthier and more productive ecosystem. 
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Can there be too much grazing? A complete answer to the lawn mower experiment depends on how frequently you mow the lawn, how often you water, and the nutrient richness of the soils. The theory of grazing optimization predicts that the relationship between grazing intensity and plant growth is hump-shaped. That is, compared to no grazing, plants grow a little more under low and high grazing, a lot more under moderate grazing, and less under extremely high grazing (Hilbert et al. 1981). Doug Frank (see Interview, this issue) and 

his colleagues tested grazing optimization in northern Yellowstone when elk populations were high during the 1980s. They discovered that elk moderately grazed areas by migrating in sync with plant greenup. They ate about 20% of plant growth on wintering areas, 47% along migration routes, and 28% in summering areas (Frank and McNaughton 1992). Plants had time to recover after grazing because elk moved to higher elevations in pursuit of the green wave (Frank et al. 1998). As a result, grazing increased production of leaves and stems by as much as 43% and roots by 35% (Frank et al. 2002). Elk were the perfect Yellowstone grazer. The landscape looked like they bit every blade of grass. However, elk never took too much grass. Their migration led elk to graze sites near an idealized level of 30 to 40%, which maximized positive effects on plant growth (Frank and McNaughton 1992, Frank et al. 2016).

From the 1980s northern Yellowsdominated by elk bison. Elk numbebison numbers inSince 2012, we soptimization in a We needed a waWe took pictures feet (0.5 meter ba camera adjustenear-infrared banreflected by greecomputer softwaof each image. Asmall wooden frathrough the framand counted the touched plant mmaterial within toven, and weighplots, we develorelated the dried to either photo g

of pin hits. This enabled us to estimate thwithin other plots without cutting and weOnce we had a way to estimate plant mastill needed to figure out how to account and removed. We modified methods origSam McNaughton and Doug Frank (see Inscientists who spent decades studying graYellowstone and the Serengeti (McNaughMcNaughton 1992). We installed several 

Measuring plant production. A citizen scientist partnership with Yellowstone Forever and Ecology Project International called ‘Home on the Range’ supports hundreds of high school students working alongside Yellowstone biologists. 
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as snow melted. We placed a fence around half of the plots to prevent grazing. We left the other plots unfenced. We measured the amount of plant material when we set up each plot and again after 30 days. The fenced plots told us the amount of plant growth during each 30-day period. The unfenced plots told us how much grazers ate during the same time. We moved these paired plots after every 30 days, which enabled us to measure plant production and consumption for the entire summer. We also set up permanently fenced plots to measure plant production under no grazing. Bison did not diminish the productivity of grasslands in northern Yellowstone. Grazing of less than 5% of plant growth had no effect on productivity. Moderate grazing of up to 30% tended to make areas 20 to 30% more productive. For grazing intensities up 50%, most sites showed no difference between grazed and ungrazed areas. Low and moderately grazed sites occurred in the less productive areas of the northern Yellowstone. These were the drier, sagebrush-dominated hillsides and highest elevation grasslands with very short growing seasons. In a way, our findings suggest the effects of bison in these areas were very similar to those of elk. However, bison are not big elk. Bison set up their grazing lawns in the highly productive, wet habitats like areas you would see if you stood alongside the road in the Lamar Valley and looked out towards the immense flat grasslands surrounding the Lamar River. Bison mowed up to 80% of the plant material that grew there. 

Ironically, park ranative plant speccultivated grasseefforts in the earIntroductory Artiintroduced cultivKentucky bluegraThey are cool seawhen the weathcultivars stop grobecause they ineare perfectly adamid-elevations oAs a result, these plants in wet areYellowstone. Todcommunities and Junction to the LRidge and to the The cultivars are them in a greenhtolerance and dis

clipping them to 2 inches (5 centimeters) days for six months to reduce productivityplant growth, bison would need to graze plants never exceed 2 inches in height ovgrowing season. Bison eat a lot of plant mof the Lamar Valley and some of their othmats of plants around 2 inches tall. This tgrowing season after plants have stopped current numbers of bison in northern Yellto grazing plants to these levels every two summer. 

Bison increased productivity through their grazing by as much as 20 to 30% under moderate grazing. 
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Our sites in the bison lawns showed variable effects of grazing on plant production. Some areas of the Lamar Valley suggested grazing approached, but did not reach, levels that reduced productivity. Wetter areas were the most resilient to high grazing and produced more plant material even when grazed at 70 to 80%. Plants are limited by whichever runs out first, soil water or soil nutrients. On their lawns, bison increased soil nutrient availability so much that it relaxed nutrient limits on plant growth (Frank et al. 2018). Water became the primary limiting factor. While that seems like an eccentric scientific finding, it has profound implications on the health of grasslands in northern Yellowstone. Production increases in both grazed and ungrazed areas during wet years. It increases much more in grazed areas because nutrient limitation eventually takes control in ungrazed areas. That additional growth results in more root mass, which helps plants further resist the negative impacts of grazing and allows plants to grow even more during the next wet year. The ability of bison to engineer the control of plant growth from nutrients to water is likely a key mechanism underlying grazing lawns in Yellowstone.Grazing lawns beget more grazing lawns. Bison change the plant composition in the wet areas they use the most. More showy flowers develop, which thrive in nitrogen-rich soils. Not all plants must reproduce by creating and dispersing seeds. Some can also produce a root off the root crown that travels underground and pops up above ground away from the mother plant. Over time, the clone develops its own root crown and the process repeats. Clonal, otherwise known as rhizomatous plants, thrive under intense grazing, because they form the dense mats of plants that characterize grazing lawns. Bison improve their own grazing hotspots by transitioning areas into the types of plants that make their lawns. Ecosystem engineers are organisms that significantly modify their habitat. They are critical to ecosystem health because they construct 

a more diverse landscape. By manipulatinnot at all, and some in between, ecosystehabitats suitable for a much broader assoanimals that thrive in the extremes and inWhen we give bison room to roam, they change plant phenology and the timing agreen-up across the land. They manipulatincreasing nutrient recycling and change tgrowth to produce vegetation explosions also alter the composition of plant commby bison is concentrated in relatively smalthey only lightly graze most of the rest of variation is the fabric that underlies a moThe movements and grazing of bison probroader suite of animals, songbirds, small microbes, to name a few. As a result, bisoYellowstone ecosystem than the sense of they encounter bison for the first time. Through their actions, people choose the those they do not. Some of our greatest canimals we have recovered from near extgrizzly bears. With bison, we decided to pat the turn of the 20th century, but their unveiling in front of our eyes and the endBison conservation and restoration began of the 20th century. It took nearly 90 yeathe park. During 1980s and 1990s, when migration routes and attempting to move decided to keep them in the park. Managthat migrated out of the park or rounding them to slaughter. People drew lines on tbison could not roam—unlike any other w
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In Yellowstone, the last remnant of bison exist where nature decides who lives and dies, behaviors are passed on between generations, engineer a better ecosystem. Yellowstone bison have been, and will continue to be, a source of controversy because managing such a ladifficult in modern society. That controversy is worth the trouble because it helps to rebuild bison as an American icon while restoring m
52

State of Montana established laws to prohibit the transfer of live bison from the park to anywhere but slaughter because these bison potentially were exposed to the disease brucellosis. Through these actions, society constrained bison to the park. Across North America, bison occupy less than 1% of their historic range. We manage only about 20,000 bison for conservation on public lands. Only about 8,000 of those bison roam without fences, about 5,000 of which live in Yellowstone. Ranching is the standard model for the rest of the nearly 500,000 bison in North America. Fence a plot of land, figure out how much grass it produces, determine a light grazing intensity, and manage for a herd size that eats about 25% of the grass. Move them between pastures like cattle and round them up each year to keep a predetermined and unnatural age and sex structure that facilitates easier management. We continue to struggle to articulate why we need to restore bison and what successful bison conservation looks like. Too many current conservation efforts involve maintaining bison in small numbers and artificially manipulating their genetics to reduce inbreeding by moving animals on trucks. Most people do not realize the individual groups of bison they encounter while visiting Yellowstone, particularly in summer, are larger than most other conservation populations. Most bison preserves are small and could fit within the seasonal ranges used by Yellowstone bison, such as the Lamar Valley. The precolonial force of bison migration is gone because tens of millions of animals no longer roam across much of North America.Yellowstone’s bison provide a sense of hope of what is possible when we bring back large bison herds and find ways to allow them room to roam. We should strive to protect more large bison populations where they can roam across large landscapes and engineer the land. We should also strive to rethink managing grazing of smaller, spatially constrained bison herds in ways that allows them some opportunity to enhance their ecosystems. 

Literature CitedSee Literature Cited section of this issue o

Chris Geremia is the program coordinato

Yellowstone National Park. He leads a BisProgram returning Yellowstone bison to Nassists in resolving conflicts when bison mand studies the most ecologically and cultherd left on the planet. The program’s resbison conservation. He received his doctoUniversity and has studied Yellowstone bi
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Sagebrush Steppe Monitoring Stefanie D. Wacker

When I look across the vast landscapes of Yellowstone National Park, I read a story of geology, climate, and wildlife that has walked these lands through the ages. 

I can read this story using plants as the words, as they represent what can grow where, how much it rained, and who stopped for bites of grass. Plants feed us, help us to breathe, and create beauty wherever I look. I love this about plants—they have a quiet power worthy of admiration. Wonderful landscapes are covered in blankets of plants, each community so complex in the intricate details that its significance is often lost to the casual observer. Vegetation is the foundation to so much life here in the park; from our largest mammals to our smallest insects, plants play a vital role. Gaining an appreciation of this amazing resource emphasizes our duty to 

be good stewards, a role that requires us understanding of the complex relationshithis knowledge to protect and preserve thdepends upon it.The northern portion of Yellowstone Natihabitat for large herbivores such as bison such as cougars and wolves. It also suppoand insects. This breadth in wildlife speciecommunities for food and brood habitat. northern Yellowstone contribute to ecosycarbon and nitrogen cycling, water cyclinof soil microorganisms. This highly connethe plants serve as the foundation of the 
54

depicts how productivity (or energy) passes from producers through consumers in an ecosystem. Because of the importance vegetation plays in the overall quality of habitat, it is critical scientists monitor for changes in the health and function of the sagebrush steppe, which is predominant in northern Yellowstone. In the western United States, there has been an enormous loss of big sagebrush habitat due to cultivation and cattle grazing, invasions by nonnative species, mineral and gas extraction, and other development that fragments habitats. Additionally, areas of the intermountain west have seen expansive sagebrush die-offs due to drought. Other areas have seen loss of sagebrush in the form of wholesale plant community shifts due to the nonnative invasive cheatgrass, which not only displaces native species but also has significant impacts to the natural fire cycle and ecosystem function. In other areas, sagebrush has been removed by physically pulling shrubs from the ground or by herbicide to stimulate grass growth for domestic grazers. Mineral and energy extraction have reduced the land base that supports sagebrush required for food and brood habitat by sage grouse. Because so many of these shifts in land use are permanent, sagebrush habitat is considered one of the most threatened ecosystems in the west, with roughly half of lands formerly occupied by big sage now gone (Noss et al. 1995, Welch 2005).Because Yellowstone National Park has been a protected area since 1872, it has not seen significant land use conversion; however, it is not without some human disturbance. In the early years of the park, the Army needed to feed themselves and their stock, so some lands were turned into hay fields and horse and stock corrals. As more people came to see the park’s natural wonders, the need for visitor services increased developed areas, and roads and trails began to expand into areas formerly covered with sagebrush. Current-day visitation and infrastructure maintenance has had an impact on the sagebrush, as have natural disturbances such as drought, wildfires, 
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and persistent native ungulate grazing. It is unknown to what degree these historical and ongoing disturbances impacted the sagebrush steppe community. The best way to measure our impact is through a quantitative examination of these plant communities. Research is used to gain basic biological information, understand roles in ecosystem function, and inform management decisions. Scientists also use research to answer specific questions and track changes across landscapes; hypotheses testing addresses the former, long-term monitoring the latter. The value of a long-term monitoring program is that it can address many goals with the same dataset. For example, monitoring can simultaneously track increases and decreases of species or communities in peril, movements of populations across a landscape, provide species inventories, note fluctuations in composition, and detect new species or extinctions. Baseline data describes the landscape, and subsequent data tracks the status and changes. The longer the duration of monitoring, the more information scientists gather, which increases our ability to understand ecological interactions and patterns and processes. Of enormous concern in Yellowstone is the alteration of the patterns and processes of our native flora when invasive species enter the system. Invasive species are detrimental to the native plant communities because they alter plant composition and abundance, resource allocation, and usable habitat. Any life form of nonnative plant can become invasive, but in Yellowstone, they primarily are annual or perennial grasses and forbs. Perennial invasive plants tend to become established in patches, then expand either vegetatively or by seed dispersal. Invasive annual plants can have considerable spatial and temporal fluctuations, which is part of what makes them so detrimental to native plant communities. The life strategy of all annual plants is to produce as much viable seed as possible during their sole year of life. This abundance of highly viable seed creates a large population of plants, which creates large amounts of seed, and so on. This becomes problematic to native plant communities when 
56

the species are nonnative and without natural enemies, allowing the invasive population to expand at a rate much greater than the native species. This cycle is exacerbated by winter annuals. Winter annuals are plants that germinate in the fall of the year when native species are beginning to senesce. They over-winter with actively growing root systems allowing them to green-up in the spring before the native species are active. They flower and set seed early, producing viable seed by early to mid-summer. This seed then germinates in the fall and the cycle continues out of synchrony with native flora. Often times, these species use many of the water and nutrient resources; hence the common name cheatgrass—it “cheats” the other plants of the resources and flourishes while the other species struggle. Across the western United States, cheatgrass has had considerable deleterious effects on the sagebrush steppe that likely will continue under the warmer, drier conditions expected with climate warming.In Yellowstone, there are about 150,000 acres (607 square kilometers) of land where the dominant species is sagebrush, largely big sage and silver sage. These species occur in northern Yellowstone, as well as the Gallatin Range and Madison, Hayden, and Pelican valleys. Big sagebrush has representatives from three subspecies: basin, mountain, and Wyoming. Silver sage is represented by a single subspecies. Yellowstone has small populations of other sagebrushes, but the sagebrush population is largely mountain big sage.Sagebrush is a long-lived member of the Aster family. In Yellowstone, sampled plants averaged 35 years old with a range of 2 to 88 years (Wambolt and Hoffman 2001). Sagebrush occupies spaces that get most of their precipitation in the form of snow during the non-growing season. Its large, shrubby stature captures snow, which usually melts slowly, allowing water to move through the soil column. The extensive taproot can use this water, which allows it 

to be tolerant to drought. Smaller roots nplant to use surface water. Big sagebrush restricted by soils, but they can occur side the largest in stature, and can be found in drained soils. Flat-topped in form, mountrange of elevations and is found on hillsidSilver sage is also found in the valley bottother places with wetter soils. There are pwhere silver and mountain big sage occubig sage has the smallest stature and occpart of the park, the Gardiner basin. Sagesummer and seeds are mature by late fall is the only one of these sage species that following disturbance, whereas big sage by seed. Seeds are very small, and do not the parent plant. Seed production dependand competition for water and sunlight. Lseed predation by insects and rodents are recruitment (Jacobs et al. 2011). The sagebrush community type is charactforb understory, with occasional other shrnative shrubs found in the area are green greasewood, fringed sage, rose, juneberrwinterfat, Oregon grape, white coralberryEach of these species can be locally abunddominate the landscape like big sagebrusgrasses and forbs are Idaho fescue, Sandbwheatgrass, slender wheatgrass, Columbvarious upland sedges, field chickweed, sslender-leaf collomia, and western yarrowspecies are dandelion, salsify, cheatgrass, wheatgrass, spotted knapweed, houndstotoadflax, to name a few.
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Understanding that sagebrush and associated communities play an important role in the park, Yellowstone adopted the sagebrush steppe monitoring protocols developed by the Upper Columbia Basin and Greater Yellowstone Inventory and Monitoring Networks (Yeo et al. 2009). These data collection protocols and methods of analysis are conducted by a combination of Network and Park staff in eight parks in the west. Adopting these protocols allowed us to readily implement a protocol already tested and in use by other parks that have large amounts of sagebrush. These protocols addressed several aspects of the sagebrush steppe, namely the changes in frequency and occurrence of native plants, the spatial and temporal distribution of invasive plants, the community response to climate change, and the response to disturbances such as wildfire and grazing. Sagebrush steppe is sagebrush plus numerous species in the understory—often so many that information collected on all of them becomes difficult to interpret. The protocol uses an abbreviated list of species to monitor. Species were selected to provide the most information about the sagebrush communities, balanced with the ability to read a large number of plots annually. Scientists also decided to monitor species indicative of recent disturbance, susceptible to the effects of climate warming, or that increase or decrease under heavy grazing (Figure 1). Sites selected for sampling represent a range of density and abundance of sagebrush. Areas of highly degraded flora due to significant past disturbance or long-term nonnative plant infestations, such as the Lamar Valley floor, roadsides, and the Mammoth area, are avoided. Biologists collect data in specific locations categorized by slope, aspect, and elevation. The exact locations where data is collected are determined by running a computer program that generates locations in a statistically robust, spatially distributed manner. In addition to recording the occurrence of the species, biologists also record the abundance of each species, 

Figure 1. The breakdown of species of interest by referred to as “cover.” This measures the area underneath the canopy of each specmany layers of plant canopies, the total c100%. Correctly determining the exact pcovered is nearly impossible, so data is cobins) to record the percentage of area covas zero to 5%, 6 to 25%, and so on (Dauused to tell which species occur where, h
58

Determination of change is done with analyses that detect when a species demonstrates significant change over time. In addition to species data, biologists also estimate the cover of bare soil and litter. Bare soil could be populated by native or invasive species, areas that were covered but now are not (plant loss), potential erosion, or nonproductive soils. Litter is an indicator of production and potential soil organic matter. It can be a barrier to seed-soil contact, and when really deep, can impede water infiltration.There are 43 plots read on a 5-year rotation and 6 “sentinel” plots read annually. Biologists selected the plots to represent various locations in the park, densities of sagebrush, and a variety of plant communities. The project started in 2015, so we have collected five years of data on some of the sentinel sites and one visit to all other sites. Biologists used baseline data to describe each site, and they will assess trends with data collected in upcoming years. They will also use the data to create detailed site descriptions and assess the value of each study location. Both big sagebrush and silver sagebrush populations appear to be healthy at all our sampling locations. Since sagebrush die-offs have occurred in the southern part of Wyoming, it is of concern here 

in Yellowstone. While the protocol does nspecifically, a significant decrease in cover observations by staff would alert us to chrecruits at every location, with the exceptin 2016 and biologists sampled in 2017. Tthere would not be new shrubs at these lfor seeds to germinate and establish.

Basoihas barthagroeveThe of eithon one promingroalso pocgo

bring createxambison 

and erosion which leave patches of bare sLitter—The sites with the highest litter ar

lowest bare ground; they have high leaf c

The boundaries for the sampling frames are all created in Geographical Information Systems (GIS), as are all the specific sampling quadrats. On the landscape, the black line shows the area in which sagebrush is the dominant plant, and where the quadrats are concentrated. Photo by NPS/Shulstad.
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Disturbances, such as this old bison wallow, can become the point source of exotic species. Bare soil and reduced competition from other plants allows the cheatgrass to establish and produce seed. The seed is then moved from this source location across the landscape, where it establishes and produces seed, and so on. This cycle perpetuates, creating an “invasion” of exotic species into the native plant communities. Photo by NPS/Wacker.

Sampling in a frame that was burned in the 2016 sagebrushes and litter were totally consumed by fiin June of 2017, there is abundant bare ground, bgrasses, indicating how this system responds to fi

and shrubs. Some of these sites have not only a flora of native grasses and forbs, but also a high abundance and frequency of nonnative grasses, such as Kentucky bluegrass and timothy. As one would expect, there is a negative relationship between litter and bare ground: the higher the litter, the lower the bare ground. In most locations in the study, there is not an abundance of litter, indicating that there is not high vegetation production and/or that it decomposes readily.Native Plants—The most frequently occurring native plants across the study are upland sedges, rockcresses, Idaho fescue, junegrass, and pussytoes; the most abundant are Idaho fescue, mountain big sage, lupine, bluebunch wheatgrass, and upland sedges. All of these species are perennial. Species such as the rockcress are very small, 

with little leaf cover, but found at nearly emost infrequent native species are milk vericegrass, and lava aster, which largely ocsoil types of the Gardiner basin. The least grass, oval-leaf buckwheat, and scarlet glspecies are more restricted in distribution the study area. The native grasses are widwith localized variability in abundance. Almonitor in the understory of the sagebrusbunch grasses. Nonnative Plants—The most frequently species are dandelion, Kentucky bluegrasdesert alyssum; the most abundant are Ke
60

Anatomy of Grass Plants Yellowstone’s Sageb

Spike(Inflorescence)

Internode

Node

Blade

Sheath New Plant New Plant

Stolon

Rhizome Roots

Collar Region

Node

Sticky geranium is a native, perennial plant that reproduces by seed and is commonly found in the sagebrush steppe. 

STICKY GERANIUM 

PERENNIAL plants are those t

have multi-year life cycles. Thebe short-lived (3-years) or long Some perennial trees and shrulive for 80+ years!ANNUAL plants are those thaminate and complete a life cycone year. 
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Lupine are a native, perenplant that reproduces bseed. They acommonly foin the sagebsteppe. 

The most common variety of the three sage plants found here is the Mountain big sage. It is a long-lived shrub that reproduces exclusively by seed. 

Idaho Fescue is the most common grass found in the sagebrush steppe and is a cool season bunch grass.

Invasions by cool-season sod-forming grasses such as this displace native species. Kentucky bluegrass reproduces by underground rhizomes creating sod, which exclude other species creating a monoculture. 

Cheatgrass produces numerous viable seeds that germinate in the fall, then overwinter with an active root system. This grass “cheats” the other plants of needed resources by greening up in early spring before other plants green up. 

CHEATGRASS IDAHO

FESCUE

KENTUCKY BLUEGRASS LUPINE 

A COMMUNITY is a collection of plants that otion. This location can be large or small. A TRANSECT is a very specific area that a sciencollect data. A QUADRAT is a bounding shape (usually squthe data is collected. 
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timothy, desert alyssum, dandelion, and cheatgrass. Of these, only desert alyssum and cheatgrass are annual species, the others are perennial. The most infrequent and least abundant nonnative species are houndstongue, Canada thistle, spotted knapweed, and bulbous bluegrass. Houndstongue is a biennial, the others are perennial. Nonnative species can have significant impact on the community regardless of life-span. When all the species we record are aggregated, the most infrequent and least abundant are the nonnatives; simultaneously, the most frequent and abundant are also nonnatives. It is worth noting that some nonnatives are not invasive, and many occur at low frequency or abundance and pose little threat to the native flora. This monitoring program is focused on the health of the plant community which comprises the sagebrush steppe, emphasizing the 

presence of invasive species in time and sin several ways: detection of species unknthe park, detection and quantification of to be present but with an unknown spatiof species with unknown abundance, and effects of nonnative and invasive species data collected in this effort are also used abundance of sagebrush, as well as the omake up this community type. In the examination of the baseline data, oand abundance of nonnative, cool seasonrepresented by Kentucky bluegrass, timotSod-forming grasses have strong tillers anby sending up culm (stems) that will deve
Yellowstone Scien

cluster) from rhizomes (underground stems). Although bunch grasses still have an extensive root system and the ability to send up flowering stems from a root bud, population expansion by this method is much less than in sod-forming grasses. Under conditions of a warming and drying climate, and with continued high-intensity grazing, the nonnative sod-forming grasses could have a competitive advantage over the native bunch grasses. We do not currently have any study plots in areas where extensive patches of sod-forming grasses occur, but the implications to native grasses trigger a need to begin collecting data these areas. An unquantified benefit to the study is the many observations made while travelling to study sites. Observations include the increased frequency of weeds at trailheads, along trails with high levels of horse use, and on social trails. Of particular interest is the number of Douglas fir trees that have a ring of cheatgrass underneath them in places where it is unexpected. This discovery led to the development of a separate effort to try to detect early season invasives (cheatgrass and desert alyssum) using remote sensing tools such as satellite imagery and aerial photographs. Also of great value is knowing the frequency of occurrence and abundance of the nonnative invasive species that we are not currently aggressively treating. We now have data on species such as desert alyssum and cheatgrass—winter annuals that have the potential to greatly affect habitats in northern Yellowstone. Using distribution data plus our field observations, managers started to treat these species in the fall, when chemical treatment is very effective. The vegetation resource at Yellowstone is very complex and covers a majority of the park. Because this park is so large, it is logistically impossible to collect all the data we would like. Using a monitoring program stratified by topographic and climatic variables, we can collect data at a reasonable number of representative locations. If the results bring cause for concern, we can establish new plots, increase 

the frequency the plots are read, or initiatstrategies. The critical next step in the moensure its longevity. The value of this projeach additional data set, and a commitmethe importance of the vast vegetation resirreplaceable landscape.The grandeur of Yellowstone National Parto different people—some love the wildlifthe geysers—for me, the very essence of the huge, awe-inspiring, landscapes stretccan see. Part of what I love about the viewlandscape looks up close, at a middle distclose, I can see trees, sagebrush, and flowfarther, the trees look soft and velvety; thand the flowers, only a yellow hue. When stress, and focus on the present, I hike ouspectacular view to enjoy, and contemplathe entire system functions so well. The sgrow under warm sun and cooling rain shborn under the sagebrush and forage on system, so intricate and beautiful, is what special and worth protecting for this and Literature CitedSee Literature Cited section of this issue oStefanie Wacker was the park’s Vegetatof interest is terrestrial plant invasions and areas. She has undergraduate degrees froColorado Boulder in Geography and EnviMaster of Science degree in Biological SciState University. 
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Author’s note: I would like to dedicate this article to my mentor, advisor, teacher, and friend, Dr. Gary E. Larson. 

force in my love of plants and in my career; I would be a different person without his influence. His legacy is in hi

as stewards of this amazing resource all over the nation, many with public land agencies. Rest in peace, Gary, you 

Big sagebrush (Artemisia tridentata): The genus name comes from Queen Artemisia II of Caria (353-351 BCE) who was a botanist, and t

lobes at the end of the leaf (3 teeth). 
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Stefanie recently accepted a position as aNational Park Service in the Denver Servicprogram. Nancy Finley, Chief of the YellowResources notes, “Stef Wacker has been a Yellowstone in advancing science and our communities and their importance in this grateful for her thoughtful insights in impprogram and wish her the best as she loo

A one square meter quadrat is used to delineate the area in which the plants are sampled by species and the area each species covers within the quadrat. NPS Photo/Wacker.
66

Women in Science: Mary Agnes Chase

Mary Agnes Chase (1869-1963) had a lifelong fascination with the world of plants. Her passion began as a young adult when her brother-in-law encouraged her to study botany 

after the death of her husband, just one year after their marriage. After studying the plant life of her childhood home in northern Illinois, Chase became a U.S. Department of Agriculture Division of Forage Plants botanical illustrator in Washington, D.C. The bureau eventually became part of the Smithsonian Institution. Her work led her to a partnership with Albert Spear Hitchcock, a principal scientist with the Smithsonian herbarium. From 1905 to1912, Chase explored grasses throughout the United States, which led to the publication of Manual of Grasses of the United States with Hitchcock in 1934. Throughout her life, she authored over 70 publications. Her focus on grasses led her to Brazil where she documented over 500 new species there. She later conducted “two journeys across South America alone, during which she went by train, boat, donkey, and by foot, became the only woman to stand on top the highest mountain in South America, braved insects that bored into her toes, ran out of food and got hungry...” (Schultz 1949). Her work at the Smithsonian Herbarium made it a taxonomic resource for botany taxonomy and agricultural scientists whose work resulted in grasses that were higher in nutrition and disease resistant. Chase was a vocal suffragist, jailed twice for protesting in front of the White House for women’s right to vote. Chase was the eighth Honorary Fellow of the Smithsonian Institution in 1958. She received a Doctor of Science degree at age 89 from University of Illinois and continued to collect plant species throughout the world well into her 90s. She formally retired in 1939, but worked, for no pay, throughout the rest of her life. 

Her passion for plants, and grasses in parpassion. She said, “Grass is what holds thmade it possible for the human race to abherds. Civilization was based on grass, ev(Schultz 1949).

Charissa Reid
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Bouteloua megapotamica (Spreng.) Kuntze [Bouteloua megapotamica (Sprengel) 

Kuntze, Poaceae alt. Gramineae], ink on paper by Mary Agnes Chase (1869–1963), 29 × 26 cm, for David Griffiths (1867–1935), "The grama grasses: Bouteloua and related genera" in Contributions from the United States National Herbarium (1912, fig. 52), Hitchcock-Chase Collection of Grass Drawings, on indefinite loan from the Smithsonian Institution, HI Art accession no. 6010.0825.
68

What’s an Inventory & Monitoring Network?

The National Park Service Inventory and Monitoring Program conducts long-term ecological monitoring within National Park sites, collaborating with a variety of partners and 

providing valuable data to park managers and the public.Through 32 Inventory and Monitoring networks across the country, networks gather and analyze information on specific park natural resources—the plants, animals, and ecosystems that can indicate the overall biological health of parks. 

• Inventories help us understand the range of natural resources in 

and around parks.

• Monitoring helps us understand how these resources are doing 

over the long term. 

Good decisions start with good informaticollected helps parks make sound, sciencedecisions that help preserve America’s speinventories, including vegetation, species, gives us a common starting point for monconsistent long-term monitoring, we can stable or might be changing.To learn more about the Greater YellowstNetworkthat conducts this work in our regryn/index.htm

Who is Inventory & Monitoring? We're over 300 National Park Service staff from across the country and our roles are as varied and diveWe are ecologists, biological science technicians, and data managers; GIS specialists, administrators, physical scientists, and writer-editocommon love of our national parks, and by our commitment to providing the best science possible as the foundation for managing par
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Yellowstone National Park

Bighorn Canyon National 

Recreation Area

Grand Teton National Park

John D. Rockefeller, Jr. 

Memorial Parkway

Read more about the 

Yellowstone Inventor

Yellowstone Science 

The Vital Signs Issue
70

The earliest efforts in Yellowstone National Park to control an “unwanted” plant were in the 1960s with Dalmatian toadflax. This perennial forb of Mediterranean origin was 

brought into the United States in 1894 as a garden plant. Park managers found Dalmatian toadflax in 1957; a few years after concessionaires planted it for use as a table ornament in the Mammoth Hotel dining room (Whipple 2001). Plants spread rapidly from the Mammoth Hot Springs area, and resource managers used grubbing, mowing, and chemical herbicide to try to kill it. In the early 1970s, park staff released a nonnative moth to eat the plant, though these efforts were unsuccessful (Story 1985). Dalmatian toadflax eventually spread over a wide area of the sagebrush-steppe community in the upper Yellowstone River valley in and outside the park. Managers thought this weed would displace native sagebrush and grasses, thereby reducing the amount of food for grazing animals. Weed control efforts in the park continued into the early 1980s, mostly targeting 7 to 10 species considered noxious by surrounding states. Efforts increasingly focused on spotted knapweed, first documented in the park in 1973. This weed spread rapidly through the Pacific Northwest, Montana, and into Yellowstone via roads and developments (Boggs and Story 1987, Allan and Hansen 1999). As the number of nonnative weeds and infested areas in the park increased, managers adopted an Exotic Vegetation Management Plan (NPS 1986) that established four Weed Management Districts in the park. Biologists identified 85 nonnative plant species in the park, but focused control efforts on those most likely to displace native plants. The number of nonnative plant species in the park increased to more than 185 by 2001. This represents about 15% of the vascular species found in the park despite efforts to coordinate control strategies 

Controlling Invasive Weeds in YellowstoneRoy Renkin
Yellowstone Scien

across the Greater Yellowstone Area (GYA1992, Sheley et al. 1999, Whipple 2001). prevent weed introductions through early or at least containing infestations. They aand monitoring to better define the extenthe effectiveness of control efforts (Olliff eprioritized the treatment of 24 nonnative distribution, likelihood of displacing nativto control efforts, and cost-effectiveness oKreuger 1999, Skinner et al. 2000, Olliff eThey created databases to document areato control weeds. Also, they conducted acertain weeds occurred in, or could invad(Allen and Hansen 1999; Pauchard et al 2b, 2006; Pauchard and Alaback 2006; Lehstudies indicated roads, trails, developed lines created conditions favorable for weespread. They also indicated native sagebrin the Yellowstone, Lamar and Firehole/Mpotentially the more remote and largely invalleys, were vulnerable to weed invasionPark managers completed an Invasive Vegand Environmental Assessment in 2013 to restore the diversity, ecological integrity, awith native plant communities in the parkweed management efforts with other ageand establishment of new invasive plantsor eradicate existing infestations. The plan to describe weed occurrences and distribueffectiveness of control efforts and potencommunities. In addition, the plan encounative plant communities disrupted or repLessons learned and information obtained 

Spotted Knapweed
72

to adjust management actions over time in response to changing knowledge or conditions.The introduction and spread of invasive plants is the greatest threat to native plant communities in the park and throughout the GYA (Hanson 2009). There were about 217 nonnative plant species in the park by 2013, an additional 31 from the previous decade. Forty-seven species are on the park’s “watch list”, while 46 are priorities for control. Management actions are minimal to nonexistent for more than 168 invasive species. Biologists discovered and treated ventenata grass, a new aggressive invader, in two small, but separate, areas of northern Yellowstone in 2018. This plant is increasingly problematic in agricultural and rangeland areas of the intermountain west (Jones et al. 2018) and occurs in Montana counties adjacent to the park. It is likely that increased monitoring will detect other occurrences of ventenata in the park that need quick, aggressive treatment consistent with the established management plan. It is difficult to map the distribution of nonnative plants in Yellowstone due to the park’s large size and varied vegetation communities. As a result, biologists often use satellite imagery and modelling to approximate distributions and predict spread. Each summer, park weed crews, in conjunction with the Northern Rockies Exotic Plant Management Team and the Montana Conservation Corps youth crews, inventory 3,500 to 8,000 acres (1,400 to 3,200 hectares) for about 30 invasive plant species and treat up to 200 acres (80 hectares; NPS 2018). Other efforts to prevent the invasion of new nonnative plants include the annual inspection of about 16 gravel pits outside the park used to obtain materials for park construction projects. Efforts also include the inspection of earth-moving construction equipment to ensure they are free of invasive weed seeds. Managers do not allow hay for packhorses and mules in wilderness areas, and only feed weed-free hay in 

other areas. These efforts are coordinated Cooperative Weed Management Areas acvarious portions of the park, with similar for sharing of resources and personnel to et al. 1990). For example, the Hold the LLeafy Spurge out of Yellowstone National Cooperative Weed Management Areas adpark while restoring native vegetation in abeyond the southwestern boundary of thinformation from management efforts wiCoordinating Committee’s Terrestrial InvaFor decades, managers have attempted to to areas disturbed by construction activitialong road corridors (NPS 1997, 2002). Hnative vegetation to weed-infested areas Currently, about 75 acres are at varying stnative vegetation in the Gardiner Basin arfocused restoration efforts in areas with rof nonnative weeds rather than areas dograsses like smooth brome and timothy into provide food for deer, elk, and pronghaddition, park managers have used chemsome areas to reduce the density, or num1). Herbicides substantially reduced the dDalmatian toadflax, and yellow toadflax agrowing plants of spotted knapweed and treatment sometimes stimulates root sproseeds into the soil which has lessened the efforts with spotted knapweed and oxeye lived perennial plants produce many seedsoil for decades (Davis et al. 1993, Sheley requires persistence. 
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Managers in Yellowstone need to preservwhile managing the spread of existing or task is difficult given increasing visitation, and a warming climate with conditions ofinvasive plants. People can introduce or sdirt or mud on automobiles, over-snow veequipment, as well as through gravel, san2001). Areas most vulnerable to invasion soil disturbance or the removal of vegetatestablishment along roadsides, trailheadsareas, as well as along unauthorized trails wildlife viewing areas, has intensified due damage to native vegetation. Managers neffects. Most of the invasive plant species targeteare noxious weeds that tend to be biennilifespan from two to many years. Annual life cycle in one year have shown the mosof native vegetation in the park over the 

Cheatgrass

Table 1. The success of herbicide control at reducirange) of five weeds in Yellowstone National Park 

WEED SPECIES

MEAN % 

DENSITY 

REDUCTION

houndstongue -82.6 

dalmation toadflax -87.4 

yellow toadflax -97.5 

oxeye daisy -36 
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weeds traditionally have not been the focus of large-scale control efforts. Cheatgrass (which managers first documented in the park in 1930), annual wheatgrass, and the nonnative forb desert alyssum have become widespread and dominant, particularly in the lower, drier elevations of the sagebrush steppe communities in northern Yellowstone. All of these winter annuals are capable of germinating in autumn, overwintering in a dormant state, and rapidly depleting soil moisture with early spring growth while native plants are emerging from dormancy. These and other nonnative plant species have replaced native sagebrush and grass communities in portions of the Gardiner basin (Sikkink 2011).The ecologic and economic impacts and management challenges of cheatgrass in the sagebrush communities in the western United States are well-documented (Mealor et al. 2013). However, managers know little about the biology of desert alyssum or annual wheatgrass, or even their distribution beyond park boundaries. None of these species are designated noxious weeds in surrounding states, although Montana recognizes cheatgrass as a “regulated” plant. Thus, efforts to control them or restore degraded areas are minimal. Both cheatgrass and alyssum can spread over large areas and reduce native plant cover in rangelands of west-central Montana (Pearson et al. 2016). These plants are spreading throughout the park at an alarming rate that will require focused management with new approaches to curb their spread. For example, biologists found desert alyssum in scattered areas along disturbed roadsides in the Hayden Valley in 2016. Biologists initiated herbicide control to prevent the spread and lessen potential impacts to grassland and sagebrush communities.In addition to disturbance, biologists recognize climate as a key factor influencing the spread of nonnative plants and the persistence of native plants (Hellmann et al. 2008). Invasive plants like cheatgrass have tolerances for precipitation and temperature that limit their 
Yellowstone Scien

distribution. Managers expect many of these invasive species to respond to climate warming in ways that negatively affect native sagebrush-steppe communities (Bradley 2009, Prevey and Seastedt 2014, Brummer et al. 2016). Plants like desert alyssum, annual wheatgrass, and ventenata can respond quickly to changes in precipitation and temperature and rapidly spread through openings in native plant communities. Similarly, other invasive plants already broadly established in the sagebrush steppe communities could expand upward in elevation and alter alpine communities under warming climate scenarios. There may currently be climate tolerances that prevent seed germination or seedling establishment of Dalmatian toadflax in the alpine meadows of the park; however, a warming climate could alter these constraints and lead to an increase in the current elevational range of this plant (Pollnac et al. 2014 ). Managers will need to adjust strategies over time to protect areas of largely intact native vegetation and minimize human disturbances to the extent possible. In addition, they may modify control tactics to focus on the current margins of invasive weed distributions, target lower-priority “non-noxious” weeds, or invest in more native revegetation efforts. The more immediate and acute problems with invasive weeds contrast with the subtle and long-term effects of a variable and changing climate. Nonetheless, increased vigilance will be required to preserve and protect native vegetation communities in Yellowstone National Park. Literature CitedSee Literature Cited section of this issue on page 108.

Roy Renkin retired as the park vegetatio

He began his career in 1979 in the DivisioManagement in Yellowstone National ParResearch Division from 1985-1989. He mManagment Division, which became the YResources in 1992. He spent 41 seasons iRoy now lives in Gardiner, Montana and sand enjoying his grandkids. 
76

Managing Grassland Communities in Northern Yellowstone

P. J. White, Chris Geremia, & Bill Hamilton

The articles in this edition indicate the overall health of most grassland and sage-steppe communities in the northern portion of Yellowstone National Park (YNP) as generally 

good. Some riparian and sagebrush communities changed to grasslands during the 1900s due, in large part, to intense browsing by more than 19,000 elk (Hobbs and Cooper 2013). Elk counts have decreased by about 70% since 1994, and aspen and riparian communities are recovering in several areas; though browsing by abundant bison is suppressing recruitment in some areas (Painter et al. 2012, 2015). The compositions of plants in some grassland areas have changed in recent decades, but most of these communities are resilient and productive with healthy soils and energy, nutrient, and water cycles (Geremia and Hamilton 2019). Native plants still comprise a majority of grasslands in areas not historically used for farming, and botanists are restoring native plants in portions of the Gardiner basin that were previously farmed (YCR 2018). The conservation of wildlife has been quite successful, with the continuing recovery of bald and golden eagles, bighorn sheep, bison, cutthroat trout, grizzly bears, peregrine falcons, pronghorn, and wolves. There are about four million visits to the park each year and most people are satisfied with experiencing a wild place and viewing wildlife in their natural habitats (Resource Systems Group 2017). However, some troublesome trends need further attention. Nonnative plants have infested some areas in recent decades and changed the composition and production of vegetation communities by displacing native plants and altering energy and nutrient dynamics (Renkin et al. 2014). Native bunch grasses in drier areas may not regrow sufficiently after repeated intense grazing, which makes these communities susceptible to reduced productivity and invasion by nonnative plants (Fuhlendorf et al. 2012). Continuing trends towards warmer drier summers with more frequent drought could 
Yellowstone Scien

worsen this spread and threaten some native grass communities, which in turn, could influence the numbers and feeding patterns of ungulates (Wilmers et al. 2013). Thus, managers need a long-term strategy to monitor and manage grasslands in coordination with ungulate management. Traditional Monitoring ApproachRangeland scientists have indicated the desired conditions for grassland and sage-steppe communities in northern YNP should be the stable (climax) plant communities that existed historically with low levels of grazing (Hunter et al. 2018). The Natural Resource Conservation Service (NRCS) developed descriptions of these historic vegetation communities based on climate, terrain, soil characteristics, land use, and other factors (U.S. Department of Agriculture 2003). Managers use these ecological site descriptions to evaluate rangeland health by comparing them to existing conditions using indicators such as plant composition, production, and water, nutrient, and energy flow, with differences often attributed to disturbances such as climate change, fire suppression, or overgrazing by large ungulates (NRC 2013). There are difficulties with applying this approach in YNP and other areas where managers are supposed to conserve wilderness and wild animals with minimal disturbances by people. The NRCS did not develop ecological site descriptions for northern YNP and nearby areas of Montana (Marlow et al. 2019). In addition, plant communities do not always progress towards a single long-standing condition. There are usually different conditions communities could reach depending on trends in climate and disturbances such as cultivation, fire, flooding, grazing, and invasions of nonnative plants. Comparing differences between existing conditions and a desired state has limited value because this approach does not identify the actual causes of such differences (NRC 2013). It also would be difficult to maintain a vegetation community in some agreed-upon 

long-standing condition, and such a practthe variety of animals and plants across thal. 2012). It would be impossible to recreate naturaand animal communities in YNP. Colonists animals, excluded indigenous people, and ranching, and development that degradeplant communities. In addition, the climatover the past 150 years and nonnative pla(White et al. 2013, Whittlesey et al. 2018allowing numbers of large grazing animaelk to increase unmanaged to the point wor mass starvation occur (NRC 2013). Thunumbers of ungulates through harvests akeep animals reproducing at higher rates need for removals. Defining the appropriate condition for grainfluenced by thousands of wild, minimalungulates is difficult. Grazed vegetation cthe same as ungrazed communities, but gproductive soils, clean waters, and forage et al. 2012). In addition, managers often desired levels of grazing and the sharing oungulates based on social and political va(NRC 2013, Beever et al. 2018). The quaneaten by ungulates also vary widely acrosseasons and years due to variations in preand grazing intensities (Frank et al. 2013)the amount of forage available for eating quickly limit numbers of ungulates and gr2013). 
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A New ApproachGiven similar issues, the National Research Council (2013) recommended a somewhat different approach for managing rangelands grazed by wild, free-ranging horses and burros in the western United States. This approach does not depend on vegetation communities remaining in a long-standing condition over time. It focuses more on landscape patterns and natural processes that are better suited for managing wilderness areas with an assortment of vegetation communities across vast landscapes and disturbances such as wild fires and variable levels of grazing (Fuhlendorf et al. 2012, NRC 2013). This approach provides more flexibility to respond to changing conditions, such as climate warming, and political and social uncertainty (NRC 2013, Beever et al. 2018). Under this approach, the desired condition for grass and shrub communities in northern YNP would be to maintain a variety of functional plant groups, including bunchgrasses, annual grasses, rhizomatous grasses with root-like underground stems, forbs, and shrubs, supported by healthy soils and functioning water, energy, and nutrient cycles (Geremia and Hamilton 2019). Plant communities will vary widely in their appearance and composition depending on differences in soil and weather conditions, land use and management histories, and historic and current grazing intensities. Many communities will include widespread nonnative plants due to their previous spread. Ungulates will graze some areas intensely and others lightly, thereby providing a mosaic of conditions across the landscape to support a variety of plants and animals (Fuhlendorf et al. 2012). However, each community should still maintain plant productivity, soil organic matter, and functioning energy, nutrient, and water cycles. Geremia and Hamilton (2019) conducted detailed vegetation composition surveys of grasslands in YNP during 2017-2018 and identified four ecological communities based on soil types and variations in weather. They considered factors that influence plant 

composition and growth such as temperainorganic nitrogen, soil organic matter, peelevation in defining these different commwidely within and among areas; as a resuin soil and weather conditions among the However, the categorizations are useful focould support similar sets of vegetation coThe first type of ecological community cograminoids (grasses, sedges and rushes) arhizomatous grasses, in cool wet areas wsoils. This type of community occurs in weand Pelican valleys and higher elevations Valley, including Specimen Ridge and the vegetation includes tufted hairgrass, silveCurrent grazing intensities in this commualtering plant compositions in some areaseffects on production and soil organic maThe second ecological community type coand forbs in warm, dry areas with nitrogetype of community occurs in previously cuGardiner basin. Annual grasses such as chas well as desert alyssum, comprise more some areas, which adversely reduces prodcommunity types. Climate rather than grathe development of these annual plant coThe third type of ecological community cograsses and shrubs, with some perennial dry areas with sandy-loam soils and suffictype of community occurs in dry, upslope including the Blacktail Deer Plateau, Little of the Lamar Valley. Common vegetation junegrass, needlegrass, and big sage. Cur
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in this ecological community influence plant compositions, but do not adversely affect productivity or soil organic matter. However, a continued warming and drying climate could lead to annual plants dominating more of these communities and negatively affecting productivity and water, energy, and nutrient cycles. The fourth ecological community type consists of rhizomatous grasses and numerous forbs in cool wet areas with clay-loam soils and sufficient nitrogen. This type of community occurs in wet areas across northern YNP, including the floor of the Lamar Valley where cultivation occurred during the early 1900s. Common vegetation includes Kentucky bluegrass, clover, timothy grass, smooth brome, and dandelion. Cultivated plants spread and caused other ecological community types in the valley to convert to this type. The cultivated plants thrive under intense grazing, with high productivity, healthy soils, and functioning water, energy, and nutrient cycles. Geremia and Hamilton (2019) recommended monitoring for changes in the composition of functional groups (rather than individual native and nonnative plants), productivity, and soil organic matter at several sites in the various types of ecological communities. If future monitoring detects substantial differences among sites belonging to the same type of ecological community, this evidence may indicate that some type of disturbance, such as invasive plants or overgrazing, is causing one or more sites to transition to a different state (Geremia and Hamilton 2019). Changes in ecological communities from one type to another, such as to a community dominated by annual plants, could be indicative of an undesired condition with reduced ecosystem functions. If undesired changes occur, and managers decide intervention is necessary to restore ecological functions, then they could initiate restoration actions. Managers should implement restoration projects using a flexible, adaptive approach whereby methods are adjusted based on experience and learning to progress towards desired conditions. Restoration projects should use native seeds, cuttings, and transplants when possible (NPS 2006). 
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Management ZonesBiologists need to develop realistic expectations (desired conditions) and strategies for managing vegetation communities in various areas with different historic land uses and existing conditions. Each strategy should include implementing best management practices to prevent, or at least slow down, the introduction and spread of new nonnative plants. The Gardiner basin could be designated a Cultural Management Zone due to its historic farming, ranching, and wildlife management activities. This basin has had sparse vegetation since at least the 1870s due to active mud flows, low annual precipitation, high winds, and heavy use by livestock and native ungulates during the late 1800s and 1900s (Secretary of War 1871, Whittlesey 1995). Much of this area was homesteaded, farmed, and ranched. During the 1920s and 1930s, the Game Preservation Company purchased much of this area northwest of Gardiner, Montana, and began operating the Game Ranch. Agricultural fields in the Stephens Creek area were irrigated using water from springs and creeks to grow hay to feed elk and pronghorn (Whittlesey 1995). The Game Ranch was added to YNP in 1932 “to improve and extend the winter feed facilities of the elk, antelope [pronghorn], and other game animals of Yellowstone National Park and the adjacent land, and for other purposes ...” The Stephens Creek area was subsequently used for a nursery, horse corral operations, bison capture facility, and native revegetation. Today, nonnative plants such as crested wheatgrass, mustard, Kochia, Russian thistle, cheatgrass, and Canadian thistle infest large areas of the Gardiner basin. These infestations have resulted in a decrease in functional plant groups, productivity, and soil organic matter (Renkin et al. 2014). Given this context, management could focus on continuing historic uses and using agricultural practices to remove nonnative plant infestations and reestablish functional vegetation communities with nutritious forage for wildlife. 

The Lamar Valley could be designated an Education Zone due to efforts to recover evaluate the effects of these actions on veand other wildlife. During 1902-1909, mafrom northwestern Montana and Texas to bison were herded during summer, and fewinter at the Buffalo Ranch in the Lamar A substantial portion of the valley was cleand planted with nonnative grasses to pro1904 and 1952 (Goodacre 1933). Grassehayfields continued to grow and spread tbison continue to congregate and intenseeach summer (Geremia et al. 2019). In adCanada were brought to YNP in 1995 anLamar Valley to establish the first known 1920s (Bangs and Fritts 1996). Wolves spover the next decade, which led to an incinvestigations and education about predaeffects to vegetation communities that coal. 2016). Given this context, managemenand education to convey information abowolf restoration. Recent studies indicate tplant groups, productivity, and soil organsimilar to measurements in the 1980s and Hamilton 2019). Biologists are monitoring to determine how bison grazing maintainimproving plant growth and productivity The vast landscape between the Gardiner could be designated a Natural Vegetation Zone. Most of the grassland and sage-stearea were not farmed, and livestock have the 1920s (Whittlesey 1994). As a result, infested large areas, though they are scat
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communities. This area provides movement corridors and seasonal ranges for ungulates and other wildlife. Thousands of ungulates travel along the Yellowstone River and over Mount Everts between their winter and summer ranges, including bighorn sheep, bison, elk, mule deer, and pronghorn. Protection of this area is important because disturbances by people could reduce the survival of wildlife that depends on this corridor for seasonal movements. Protection would also support a 2018 order (No. 3362) by the Secretary of the Interior to enhance and improve the quality of ungulate winter ranges 

and movement corridors in the western Ucontext, management could focus on preplant communities, preventing infestationlimiting disturbances by people to wildlife Adaptive Management The conservation of vegetation and wildlishould be undertaken using a flexible mathat incorporates monitoring and research changes that are occurring, and decide o
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actions. Using this approach biologists evaluate current conditions, identify undesired trends, implement management actions, monitor progress towards desired conditions, and adjust actions to improve progress (Williams et al. 2007). Condition assessments need to occur in numerous places because vegetation changes across the landscape and, as a result, wildlife use portions of the landscape differently (Becker et al. 2013). Assessments of vegetation condition should include plant composition (functional groups) and indicators of energy, nutrient, and water transfer such as plant production and soil organic matter. Assessments over time should evaluate if differences within or among areas are driven primarily by weather (precipitation, temperature), components of soils, the circulation of water (hydrology), or grazing intensity. Biologists should also assess the variety of wildlife (biodiversity) using each site to determine if variations in grazing intensity contribute to local differences (Geremia and Hamilton 2019). Biologists should assess changes in conditions due to grazing, climate warming, and other effects using an experimental framework that includes pairs of grazed and ungrazed plots sampled through summer and across years. In addition, biologists should use remote sensing indices to describe variations and estimate plant production across the vast landscape. We recommend biologists input this information into models of the system designed to predict trends. Models could incorporate seasonal ungulate distributions to estimate forage use and overlay this information onto forage production estimates to predict forage consumption across the landscape (Geremia and Hamilton 2019). Biologists could incorporate new information as it becomes available and revise forecasts based on the outcomes of management actions. Moving ForwardThe Yellowstone Center for Resources is conducting an exercise to develop management and monitoring goals for grassland and 

sage-steppe communities in northern YNwill identify priority resources for conservaconcerns. Biologists will assess historic lanconditions, and trends in vegetation and was necessary, develop management actiondesired conditions (NPS 2017). Thereafterwork plans, monitor their effectiveness, aactivities as necessary. Important resourceinclude preserving the existing variety of ninspiring scenery, geothermal wonders suan intact wilderness with minimal disturbits cultural heritage to enhance visitor edu(NPS 2014). Management concerns includdevelopment outside the park, invasive pfrom increasing visitation, and the spread staff are using scenario planning and othefuture situations, their implications, and presponses (U.S. Fish & Wildlife Service 20to identify and monitor key indicators of wcommunities are transitioning to an undepresented in this issue will inform these eAcknowledgmentsSpecial thanks to the Climate Change ResCarpenter, Nancy Finley, Doug Frank, Roy Ann Rodman, Stefanie Wacker, Rick Wallediscussions and ideas about climate and gLiterature CitedSee Literature Cited section of this issue oP.J. White (see page 11).
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Charissa Reid (CR): How it is that you came to Yellowstone and began your research here?Doug Frank (DF): I started work here in 1986. I became interested in Yellowstone while a field technician at Olympic National Park. The project there was how the introduced population of mountain goats was affecting sub-alpine plant populations. I was working with a woman by the name of Robin Reid, who’s now a professor at Colorado State University. Robin had been reading some papers by Sam McNaughton at Syracuse University. He was studying grazing in the Serengeti Ecosystem of east Africa. I started reading his papers and found every article shed new light on some exciting way that herbivores were affecting Serengeti grasslands.The classic view of large herbivores, both domestic and wild, was that they negatively impacted plant production, the grasses that they fed on. Sam was discovering that they were actually stimulating plant growth in the Serengeti ecosystem. And that was new! Some thought that he was a heretic at first because it was so different than how we viewed grass/large herbivore interactions. The results were very solid though, so I began wondering if those kinds of dynamics were happening elsewhere in other systems that wild herbivores grazed grasslands. And an obvious temperate system, a North American system, that you could test that notion was Yellowstone.CR: Where are you originally from? 

Dr. Douglas A. Frank is a professor of biology at Syracuse University. His research focuses on the effects of c

mammals on energy and nutrient processes in grasslands. Since 1986, Doug has pioneered work on the egrazing ecosystem. He demonstrated grazing by ungulates increased plant production, like on the Sereng

was the first temperate system where that's been shown. NOTE: This interview was conducted by Charissa Reid, science communications specialist, on July 2nd, 2019 at thResources, Mammoth Hot Springs, Yellowstone National Park.

DF: Originally from the Chicago area but college at University of Illinois I took seasoaround out west.CR: What did you study in college?DF: Biology, with a focus in ecology. Aftevolunteered with the Student Conservatiointerpreter at Mount Rainier National Parkseasonally at Mount Rainier for a few moand front country ranger while getting a of Washington studying plant succession that is when I started working at Olympic CR: How did you get from your work in Ofieldwork in Yellowstone? DF: That’s a great question. I worked for Francis was a staff biologist that had just hired me for a summer. That was the sumtime been communicating with Sam [McNhim if he was interested in taking on a grYellowstone. Sam was sometimes brief wjust said, “If you get accepted to graduatyou on as a student.” I was accepted and in the park with Francis I started my grad1986 working with Sam.

Interview: Dr. Douglas A. Frank
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CR: What was the focus of your early work here in the park?DF: The earliest work was a dissertation study focused on how Yellowstone’s large herbivores affected grassland aboveground production. As I mentioned, Sam had discovered that grazers in the Serengeti stimulated their own forage production and I was curious if the same phenomenon could happen in a temperate system like Yellowstone.CR: That was a pretty exciting time in Yellowstone history. We were ramping up for wolf reintroduction. Was your work tied to some of that?DF: I think there were nice discussions about wolf reintroduction at the time. But the big issue relevant to my work was that I started working in the park right after Austin Chase published his book [Playing God in Yellowstone] about Yellowstone. There was a pretty large uproar about how the park’s wildlife management policy was affecting the park’s grasslands. A lot of folks felt that was the park was overgrazed.. There was interest by the park in funding research. Congress actually provided some money for Yellowstone to investigate this issue. Sam and I were awarded a grant and I received some other support from other sources to conduct the study. The study was a nice convergence of a funding opportunity to pursue my own intellectual interests about how grazing affects grasslands and seeing if the ungulate-grassland dynamics in the Serengeti were also going on in a temperate system.CR: What was the study design?DF: It was a test of how herbivores influenced production, and for that we needed a non-grazed treatment. So, you’re comparing production between a non-grazed grassland within an exclosure, and a grazed grassland. We did that at various sites around the park.CR: Are they the ones that are visible from the road when you drive 

towards northeast entrance?DF: My own exclosures are down. The onreally old exclosures the park set up in 19smaller - they were about 15 meters on a grassland location.CR: What were your methods? How did DF: When you’re studying plant growth iherbivores, the plants are simultaneously grazed, so you cannot just measure the abiomass. The method we used was similadevised for measuring shoot production idea is that you sample frequently in a grahave a set of temporary exclosures that aincremental growth over a short period othat is protected from being grazed. You those exclosures up too long because if tha feedback effect on plant growth, if theygrowth or they’re increasing plant growththat effect if you keep the exclosures up. to a new location in the grazed grassland incremental growth in the exclosures at thdone repeatedly over the growing seasonshoot production, you just sum the growsampling periods.Using this method, you can determine the production of plant growth in the grazed you sample at the same frequency, but yomoveable fences inside the permanent feremoving any [plant] tissue.CR: I’ve talked to Chris (Geremia) quite a doing now with weighing and grinding th
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species analyzed. There’s probably a lot of new technology that’s changed how this work is done over the years. Back then how did you make those measurements?DF: Well, to measure plant biomass we used an indirect method, a calibrated nondestructive method. If you pass a narrow pin through the vegetation at a fixed angle, the number of contacts that the pin makes with the vegetation correlates well with the amount of biomass, standing biomass, in the plot.CR: Sounds very intricate and as though it would be extremely tedious.DF: It’s a sadistic kind of a torture for the people who are doing it because you’re standing over a plot for half an hour, an hour, just passing the pin at the right-angle, counting contacts with different plant species and recording them.CR: I wondered how the grazing model, the agricultural model, was framing the conversation. How did you try to shift that conversation with your work?DF: My motivation was an intellectual one. Scientific questions and trying to understand how the Yellowstone grassland was operating, functioning.CR: As opposed to politics?DF: Yes!CR: How did politics influence your efforts?DF: [Compared to an agricultural grazing model] I took a different view of looking at the vitality, the health, the performance of grassland. My interests are to try and understand the pathways by which animals feed back on plant growth. There’s a lot of different really interesting pathways. The framework is how they’re influencing energy and nutrient flows. And so, although we’re measuring, and do account for, species identity, we’re interested [in 

the pathways]. It’s like when I talk to studgo to the doctor, the doctor’s not interestyou have or what you look like. What theblood chemistry and your physiology/physThat’s what we’re trying to do studying YWe’re interested in the energy dynamics agrazers are affecting those dynamics. In oenergy is being acquired by the system thphotosynthesis, and how do the animals acquisition.We can measure that by determining how productivity. Then at the same time we alanimals influence resources like soil nutrineed to regrow after being grazed to gain of how herbivores affect plant productionobvious effects on soil nutrients by defecaprovide additional nutrients for plants. However, there are other mechanisms in wincrease essential nutrients that are less ograzing stimulates soil microbial populatioand other microbes like mycorrhizal fungabsorb those nutrients. There are all sorts indirect effects that the animals have on pthem and defecating and urinating. Range scientists classically look at species how much disturbance is going on in the or not that disturbance is too much. Whea grassland [in] a national park is somethiThey are taking their model for cattle grait to parks. I think this is a mistake and lealike we are raising cattle! We don’t want into cattle managed grasslands. They are something different and special about the
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CR: A very fundamental understanding that most people have these days is that if there’s a really big increase in an animal population, plants played a role in controlling the population because of available energy and food. Are you also looking at how the plants are affecting the animal populations or are you more just focused on the plants?DF: Actually, we measure the plants and we’re trying to understand how grazing and an increase in grazing intensity is affecting plant growth. That’s a plant focused study and, thus far, as you know, things have changed. A fascinating aspect about working in this system is that it’s extremely dynamic, it’s always changing. For example, about 25 years ago Richard Inouye, a colleague at Idaho State University, and I compared actual evaporation among different ecosystems around the world. Actual evapotranspiration is a climate variable that takes into account temperature and precipitation to estimate the moisture available to plants in a system. Yellowstone turned out to have one of the greatest levels of between-year variation in actual evapotranspiration among the sites we examined around the world.CR: Wow, that’s amazing.DF: Yes. With climate being a major driver of ecosystem processes, you’d expect a lot of variability in plant growth and other things. We’re really kind of plant focused. We’ve looked at the nutrition of plants and how nutritious the plants are for herbivores. We’ve been [looking] at how herbivores are increasing their own forage quantity, but they also increase their forage quality. They increase the nutrient content of their forage. Very important. Nutrient content. Nutrients themselves are elevated when we measure them in grazed grasses compared to ungrazed grasses.CR: That’s pretty cool that they’re actually improving their own habitat. How has the makeup of grassy places like Lamar Valley changed over time? Have you seen exotic [plants] affect the system?
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DF: There are exotic, or we like to say invasive plants in the park. When I started my work in the late 1980s, there were a lot of invasive plant species in the Lamar Valley. They were some of the dominants there.Chris Geremia and I have compared my species composition data from the 1980s with current species abundances that he has measured at the same grassland sites in recent years. Native species that grew at the sites that I sampled are still there, but the balance, the abundances of species have changed. It’s hard to know what the cause of that is because there is variation that you can expect to occur on an annual basis. There is a lot of temporal climatic variation. There’s also been an increase in atmospheric CO2 [carbon dioxide] concentrations, which is a substrate for photosynthesis. It’s been shown when you increase CO2 concentration, plant growth increases. That tends to especially stimulate plants that are fast growers like weeds, like invasives, compared than others. CR: What does the word mesic mean?DF: Relatively wet. The Lamar Valley or the swales where you see more productive plant growth.CR: Versus somewhere more dry, like the middle of Hayden Valley?CR: The middle of Hayden Valley is pretty mesic. However, there is a lot of spatial variation there. You can have a site that’s truly mesic, you know, like a swale in the middle of Hayden Valley the size of this room that has a totally different set of species growing than an adjacent drier slope.CR: Has your research mostly focused on those mesic communities?DF: We’ve studied all of them. Our interest has been to try to understand where the animals are feeding and how much they feed at those various sites from mesic grassland at the bottom of slopes to the mid-slope sites to hilltops.

CR: Was tracking the animals, was that a observe where they were grazing?DF: We don’t track animals. We don’t knsites, we just know that a certain amount just measure consumption. In the more recollaborating some with Rick Wallen and tracking very closely with camera traps wsites, so they have more information than grazing the sites. During the earlier studieplants were being grazed. That they were didn’t know by whom.CR: What changes have you seen in graspatterns as elk numbers have decreased aincreased?DF: When I started, it was all about elk. ungulate species. There were 20 or more counted on the northern winter range bafewer bison using the northern range. Elk it was very exciting, and the fall ruts were everywhere. There were no wolves at the hiding in the trees. In the fall, you’d walk surrounded by bugling elk. Those are very the park back then. It is interesting now, very different in the late-80s and early-90Differences in grazing patterns, you knowherbivores, prefer to graze mesic, produelevated the [grazing] intensities in some Lamar and below the Lamar Valley. Those a lot of bison through the course of the sungulates, bison or elk, stay throughout tback when I started, because both elk anelevation gradient. They left the valleys, t
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valleys, starting in late April usually, and wpart, by mid-May. They were following thThe green wave was a band of very nutritup the elevation gradient through the gromoved with this wave of nutritious forage summer months. And they didn’t return first winter storms that usually occurred bsometimes in November. After those storthem in the Lamar Valley, maybe further dThe grazing patterns of bison have been vwolves were reintroduced. Wolves were rprey was elk. As everybody knows, the elsharply. We were measuring, back in the of elk densities, grazing intensities of arousite to site, but on average, around 40-45tissue was removed. And now measuremfor mesic sites like the Lamar Valley are qare areas where bison tend to camp out agrowing season, which is very different.CR: In the 60s, we never saw bison in Yeldown to Lake or maybe Old Faithful in thweeks ago there was a calf born in front for Resources building]. So very different. that is so much fun about working here. Yand sometimes you don’t have to wait vechanges. I remember doing an interview wa ranger here in the sixties when they wesaid that every time I saw an elk, he alwaUnheard of today. You’ve obviously been What are the main factors driving grass pDF: This is a big question. There are a lot really complex to understand which of thinfluence.
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CR: Which ones do you think are most important?DF: Well they’re different and all important to a different degree. Ecologists usually think about what we call bottom-up factors that influence the resources like nutrients and water that plants need to grow. And so those include climate and its variability that is a hugely important factor influencing plant production. Climate not only affects water availability, it also affects nutrients and nutrient turnover by governing the activity of microbes that provide nutrients for plants. The major resources that control and limit plant growth in a system like Yellowstone are water and nitrogen. So those are two major factors that impact plant growth in Yellowstone- water and nitrogen, both of which are impacted by climate.. A second bottom-up factor affecting grassland production is soil condition. Anybody who has walked around the grasslands of Yellowstone has likely noticed a lot of spatial heterogeneity, a lot of patchiness, in the types of species that grow and the plant biomass that is supported in different patches. A lot of this spatial variability is due to topographic gradients in the landscape and their effects on soils. Grasslands at the base of slopes are wetter and support a lot of plant biomass. It’s going to be much more productive at the base of slopes than elsewhere where it’s drier. Those are bottom-up effects. The topographic effect is a bottom-up effect because it influences the properties of soils that can retain moisture and increase the availability of important nutrients like nitrogen for plant uptake. In addition, there’s an important effect we call in ecology a topdown effect. An effect that herbivores have on production. In some systems, you know, that effect can be negative, it can inhibit plant growth. But in Yellowstone we’ve shown that it can increase plant production, but that effect can vary spatially depending on where on the landscape you are. The largest positive effects you have are in mesic grassland that are both relatively wet and nitrogen-rich, where plants have the resources to regrow after being grazed.

CR: The affluent communities?DF: Yeah, that’s right. The 1%! There’s a climatic factors and topographic factors, aas herbivory.CR: Are you familiar with this video that’s Wolves Create Rivers? It’s a video that’s bcascades. Doug Smith and I have talked a very popular and we actually get a lot of science office here. Wolves are changing simplification of what’s happening. With that would also be the danger - I would aof simplification would be really seductive DF: Right? Yeah. It’s complex when you hfactors influencing something as importaIt’s such an important process because thenergy that is being acquired by the systebudget, your home budget. The size of yobuy food, shelter, everything. It’s the enerthat support everything else in the systemincluding elk and bison.CR: What nagging questions are still out addressed?DF: Well, there’s a couple of burning queThere’s a lot of little ones, but there’s two is to understand what the properties of a Yellowstone and those that you find in ththem. How are these systems sustainable high levels of herbivory? For decades people have studied propertito regrow after being defoliated, their phgrasses seem to be adapted to being graz
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they create more stems and they regrow very quickly for various reasons. These are plants that are adapted to grazing. However, when considering how herbivory affects plant production within the context of a grassland, it’s not just a function of the isolated physiological response of a plant to being grazed. It’s a function of how those plants are interacting with their neighbors and the different communities of soil microbes that determine the availability of nutrients for those plants. We found that grasses and soil microbes interact in ways that increase the availability of nutrients after grasses are grazed in Yellowstone. DF: Plants and soil microbes have a very intimate, close interaction that benefits them both. Soil microbes rely on plants to provide them carbon in the form of dead leaves and roots or exudates out of the tips of their roots and plants rely on their microbes growing in close association with their roots to provide them with nutrients that are a byproduct when microbes decompose the organic residues provided by plants. Grazing increases the rate that plants exude carbon compounds that can be used by soil microbes, which in turn increases the activity of those microbes and the rate at which they make nutrients, such as nitrogen, available to the grazed plant. One of the burning questions is how at an ecosystem level, and by ecosystem level I mean the plant-soil system, how are both plants and the soil microbial community partnering to allow plants to recover or grow or respond positively when they are grazed. It’s the ecosystem response, not just the plant response. How are these responses, these plant-microbe interactions choreographed after a grazing event? That’s really one of the things that I’m really fascinated about.CR: How would you study that?

DF: It so happens that several colleagues grant proposal to study it. There are two experiment during which we grow plants and outside the long-term, two-hectare eInside those exclosures, the plants haven’years. I have previously grown plants collethe exclosures in a greenhouse at Syracuslook different. They’re genetically differenrespond to clipping differently. The ones ograzing, and the ones inside, tend to not clipping with scissors. They have differentplants and ungrazed, non-grazing adapteproposed experiment we will grow plants outside the exclosures in pots with soils frexclosures with and without different comSome of the pots have no microbes -they pots have only mycorrhizae fungi, or only and fungi, or the unmanipulated full soil the control plants without soil microbes, ttheir plant physiological response to defoclipped plants in pots with only soil mycobetween plants and mycorrhizae that mato clipping. In a similar fashion clipped pfree-living bacteria and fungi or the full comay have different responses to clipping with the different communities of soil micwith. That’s how we can differentiate the relativmicrobial communities play in the plant rethen in the field, we can also examine the soil communities.CR: What’s genomic function?
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DF: The presence of genes, the abundance of genes in the soil microbial community that we would expect to benefit plants. There are genes that regulate nitrogen and phosphorus transport from the mycorrhizae fungus to the plant. Those have been identified in mycorrhizae. There’s likewise in the free-living bacteria population genes that are associated with the mineralization of nitrogen or phosphorous or hormone production, that benefit plants, that increase plant production. This is work that I can’t perform, but a colleague, Lluvia FloresRenteria at San Diego State University, will do. She will look at the abundance of these genes in soil collected inside and outside exclosures in the field. That is the baseline information for a field manipulation experiment. In grasslands outside the exclosures that have been grazed for a long time, we will put up fences to eliminate grazing and track how the microbial communities and the genes they express change when animals are excluded and plants are no longer grazed.How does gene abundance and the traits of the soil microbial communities and plants change over a few years? Do they trend towards plant and soil attributes that we see in the exclosures? And in parallel, inside the exclosures, we will clip plots and monitor the soil microbial attributes over time. Do those plant and soil traits trend towards what we see in the grazed grassland? They probably won’t get entirely there after a couple, three years of the study, but are they heading in that direction? That is how we’ve proposed to study it.CR: That was one of your burning questions, but you said you have two.DF: The second one is that one of the reasons why grazers are increasing plant production based on a number of studies we’ve conducted in the park, is that they’re increasing the availability of soil nitrogen for plant uptake. Earlier I was saying how nitrogen is 

a limiting factor, resource, for plant growtthey add nitrogen and the plants in those grow taller. They are greener because themachinery, chemistry to allow plants to pmore. So the animals reduce the extent to by nitrogen.Water is the other major limiting factor of Yellowstone grassland. If grazers are reduof two limiting factors, nitrogen, they masensitive to the other, water or the vagariThe other burning question that I have is increase the sensitivity of Yellowstone grain precipitation and do they make the systo climate change as a consequence. I woinvestigate that. I think that has importanmanagement and how predicting the deggrassland production and the capacity for large herbivore herds may shift with climacompelling conservation argument for suon. So, if you have any sources of funding CR: I have no funds! A few weeks ago, I wand they had this display set up and it wayou can buy to sweep the floors in your hgrass. I took a picture of it and I sent it to robotic bison. Still funny, but I see that it’s you know, there’s no comparison betweecutting. You have answered my questions what the animals do to the plants. Not onalso defecating and urinating as well. It is disentangle those different effects becausthat robot to be a bison it would need to What is the most significant change in Yeyou started your studies? You want to pic
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DF: Chris Geremia and Rick Wallen have recently resampled sites that I first examined in the 1980s. We found that although the species composition shifted, the same species occurred at the sites compared to what grew there before. So the system has been pretty doggone resistant, as far as the presence of native species is concerned. However, there probably has been a growing abundance of invasive species that may have changed the properties of Yellowstone grasslands and the grazing patterns of herbivores in ways that we don’t know.There’s also been an enrichment in atmospheric CO2 that affects plant growth in some species more than others. And, of course, the regional climate is shifting, becoming warmer and including more extreme drought and rainfall events. All these things are happening simultaneously - talk about complexity. Consequently, one would expect some changes in species composition. What’s causing those changes? Probably all of them, but which play a dominant role? It’s tough to know without experimentation. I think the overriding conclusion for me is resistance of Yellowstone grassland to change in the sense that productivity is more or less the same at sites today as we measured back in the late eighties. Even with all these changes in climate, atmospheric CO2, the threat of invasive species, at least among the grasslands we resampled, the dominant, uncommon, and rare native species occurring at sites several decades ago are still there today in roughly in the same abundances. That is not to say that the grasslands have not changed at all and there are real threats to their integrity. I think there probably have been some shifts in composition and function. CR: I was talking to another biologist once who was a fan of The Big Lebowski, and he was saying I think the most striking thing for him after all these years of research is that Yellowstone abides. It’s funny, but it is what you’re saying - even though there’s been all this drastic change you’re still seeing all the species.

DF: Yes. Yellowstone abides. For sure.CR: So, in answer to the question, what hsignificant change in Yellowstone’s grasslastudies, your answer might be that it hasnDF: A striking thing for me has not been resistance of the system to major changeto be the same between when I started wtoday. Also we have found that grassland even under some of the higher grazing pexerting today. So, yes, some important pgrassland seem to resist change.CR: What is the most pressing issue or cograsslands in Yellowstone?DF: Good question. Because that’s the cruthat’s occurring in Yellowstone and elsewrefuges is what are we trying to conserveI started working here it was all about the were trying to preserve these vignettes of huge amount of sense and it was a targeEven though the how to do it was difficuToday it’s more difficult. This is not my oripeople thinking about this, but we must is and what we’re trying to conserve.We have all of these factors, a global influglobal warming, invasive species expansioparks, but everywhere around the world.ago, the national parks tended to be in thlow populated areas. And now for a lot oencroaching upon their boundaries. The ioutside of Yellowstone’s boundaries is caucommunities. 
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Getting back to the question, so what do we do? The pre-European vignettes are out of reach. We cannot stop the tide of global and regional effects on parks. You know, it’s like standing with your arms up trying to stop a tsunamis. You just can’t do it. So, what we need to do, and this is my opinion, and there are people who will disagree, but we need to try and preserve the dominant, important natural processes; hopefully the major processes for which the park was set aside in the first place. In Yellowstone, in my opinion, we need to preserve those important grassland - large herbivore interactions, dynamics. CR: Yellowstone is the only place that I’m aware of where there is a considerable effort trying to understand, to measure grazer effects on these important processes like production, nutrient cycling. There’s very extensive program monitoring to make sure that we’re not passing the threshold in which these animals are degrading the system. I don’t envy park managers trying to come up with policy. It’s a difficult [question]; what processes should we be considering?DF: Where do you draw the line? Where do you decide that we’ve gone too far this direction or the other direction, we need to step in and do some manipulation of the park? Those are difficult questions. You know, I’m a person who can provide some hopefully useful ecological information about how the system is functioning. I’m not able or really should I make those policy decisions. CR: When I first started working with the Park Service, we were really trying to communicate with people about prey and predation and the importance of predation - helping them understand that like if they saw a grizzly bear take an elk calf that was an exciting, positive experience. Right? I watched the same thing happen during the fires of 1988 where there was this whole understanding developed with the public about the fact that fire was not necessarily just destructive. It was also a positive for some plant communities. 

I’ve been telling Chris Geremia that you gfirm. I don’t think people understand the relationships between grazers and plants plants to the system. We’ve worked so hatry to help people understand that we’re an individual bison but rather a bison popreally done a great job of communicating processes beyond the very specific exampDF: I agree with you. They’re really compcertain basic understanding of how grassneed to grow, the cycles of nutrients and and dispensed.CR: I like to think people are willing to listWhy did you choose to spend a large parin Yellowstone?DF: I have always really enjoyed being in wnaturally drawn to places like Yellowstonein complexity, the complexity of terrestriaand nutrient dynamics that sustain them. This isn’t answering your question. The rein-depth how the Yellowstone ecosystem influence productivity and how the system is sustainable over time. Those are the funhave driven my research. Science operates slowly and addressing aquestions takes time. So you write a granif you’re lucky, fortunate enough, and it tperform that study and write up your findhave another set of questions beyond tha
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CR: Then you write your paper and then all the young biologists that just started their career say, oh, no, no, no, that’s not right. Isn’t that how it works?DF: One should be skeptical when there are new and unusual discoveries, but hopefully your science is solid. So over time other investigators corroborate your findings. And that’s, you know, that’s what we have found here in Yellowstone. When Sam [McNaughton] and I found that animals were increasing plant production in Yellowstone, like they were in the Serengeti, it was the first temperate system where the phenomenon was reported. And people were skeptical. But we have repeatedly found it to occur in subsequent studies in Yellowstone and [Chris] Geremia is seeing the same thing in his current work. It’s been shown in other temperate systems too.CR: Well, it sounds like Yellowstone’s not going to run out of questions for you to ask any time soon.DF: No!CR: Well we’re lucky to have you in Yellowstone. I feel very fortunate to speak with you. P.J. White is very complimentary of you. He and [Chris] Geremia both said, if we’re going to talk about this subject, we have have to talk to Doug. We’re happy that you contributed. Thank you.
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Yellowstone National Park was established, in part, to “provide against the wanton destruction of the fish and game found within” for their “preservation in their natural condition 

... for the benefit and enjoyment of people” (Park Protective Act of 1894). The park protects a diversity of aquatic, microbial, and terrestrial life in about 2.2 million acres of one of the largest temperate ecosystems in the world. Superintendents are tasked with conserving “the wild life [sic] therein ... by such means as will leave them unimpaired for the enjoyment of future generations” (Organic Act of 1916). As a result, about 99% of the park is currently managed as wilderness or undeveloped land where human disturbance is minimized compared to outlying areas and animals live in a relatively undisturbed setting. However, preserving natural conditions with minimal human impacts is challenging in modern society where rapid, widespread changes to habitats are occurring due to a warming climate, proliferating invasive species, and extensive development. Likewise, preserving wild animals unaffected by human intrusion becomes more difficult as visitation to the park increases and interactions and conflicts between people and wildlife increase. Wildlife has been defined as animals living in a natural, undomesticated environment. The current management principles and wilderness ideals of the National Park Service strongly equate minimizing human intrusion with maintaining wildlife and wildness. However, it is well documented that native peoples significantly modified their environment for thousands of years through fires, harvests, and other activities. Also, the implementation of Yellowstone’s mandate about preserving wildlife has changed over time based on the prevailing attitudes, desires, and values of society at the time. Early in the park’s history, many animals were harvested for food because there were few services for visitors. Hunting was prohibited in 1894, but angling continues to this day—though a 

catch-and-release philosophy now prevailand wildlife were viewed as needing assisfrom people. As a result, favorable nonnapredators and wildfires were suppressed, some winters, hatchery-raised fish were sand black and grizzly bears could beg alodumps. This management paradigm was reversed 1980s to reduce human intervention and processes to prevail. This approach led to humans were viewed as visitors rather thawere made to “re-wild” grizzly bears and human influences such as feeding. During efforts were made to restore native specieprocesses that sustain them, including the gray wolves, grizzly bears, and peregrine of nonnative fish and the reintroduction oand Arctic grayling, and the recovery of a bison. Today, visitors to Yellowstone have a wide regarding wildlife, with some wanting to approachable, animals that don’t threaten wanting unconstrained, uninhibited behahuman influences. This contrast is reflectemanagement and messaging in the park. visitors are warned wildlife are unpredictathereafter, however, they encounter large areas and along roadsides that are used tthreatening people and, as a result, seem for viewing and photography. In these areto manage the behavior of people rather 

Wildlife in Yellowstone: What Are We Trying to Preserve?P. J. White (adapted from White 2016)
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separation and safety. However, animals are at times hazed from areas to alleviate traffic congestion and unsafe congregations of people venturing too close. For the relatively small portion of visitors that hike away from developed areas and roads, there are signs at trail heads to reinforce warnings about the unpredictable nature of wildlife and recommend safety measures. Also, there are required training videos in backcountry permit offices for visitors that venture overnight into wilderness areas. Wildlife are less accustomed to encountering people in these areas and, as a result, are generally less approachable and may react aggressively if surprised during unexpected close encounters. This wide range of historic and current perceptions and management approaches makes it difficult to discern precisely what managers in Yellowstone are trying to preserve with regards to wildlife. Clarity regarding what constitutes wildlife preserved unharmed in relatively natural conditions is important for evaluating whether the park’s preservation mandate is being achieved, and for deciding what intensity and types of management actions are appropriate in the park. Not too long ago, some colleagues and I proposed “a wild bison population can be defined as one that roams freely within a defined conservation area that is large and heterogeneous enough to sustain ecological processes such as migration and dispersal, has sufficient animals to mitigate the loss of existing genetic variation, and is subject to the forces of natural selection” (White et al. 2015). In hindsight, this technical description of an ecologically and genetically viable population did not highlight a key component we are trying to maintain in animals—wildness, or untamed behavior. While thinking about this oversight, I recalled some of the unrestrained behaviors and unspoiled conditions that evoked awe, fear, and wonder during my journeys in the park. I remember the warning “humph” of a grizzly bear after I had walked unaware to within 25 yards of him lying on a patch of snow in a narrow strip 

of trees on a high-elevation ridge—and bafter he got up and walked away instead watching a very pregnant pronghorn doe for more than one-half of a mile to proteyet to be born. I remember a peregrine faand chasing an aerobatic teal turn-for-turcrashed into rocks along the riverbank. I ralmost effortlessly flipping a massive bisopush, and a group of bison inexplicably ba wounded elk from a pack of wolves for finding an old female elk lying at the base having died in her sleep after living for ab
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producing many calves in an environment filled with predators and other dangers until her worn teeth failed her. These are a few of the memories that, to me, are the real expressions of wildness in Yellowstone. Attempting to coalesce the essence of these recollections into a definition of “wildlife” is frustrating, however, and led me to recall conversations about Supreme Court Justice Potter Stewart who, in 1964, when asked to define obscenity indicated he couldn’t define it, but he knew it when he saw it. So, how do we combine the technical and the intuitive to define a realistic benchmark of what we are trying to preserve in Yellowstone with regards to wildlife? I propose the following: wildlife are untamed, free-roaming animals that live in an environment not dominated by humans and whose behaviors, movements, survival, and reproductive success are predominantly affected by their own daily decisions and natural selection. Mechanisms that contribute to natural selection include how wild animals compete for food, mates, and space; how they protect themselves and respond to encounters with predators; who they choose to associate and mate with; and how they move about the landscape and endure variable environmental conditions. Animals with traits that make them better adapted to the environment will tend to survive, reproduce, and transmit their genetic characteristics to succeeding generations more than other animals. Through this process, natural selection shapes wild behaviors and characteristics. The word “untamed” in the definition incorporates the concept of wildness and uninhibited behavior but is somewhat problematic because its meaning is subjective based on the perceptions of the observer and, as a result, could be difficult for managers to evaluate. Some people contend untamed animals should be wary of humans and avoid interactions with them, while others perceive untamed animals as free-roaming and unconfined, with their avoidance or indifference towards humans having little bearing on whether they 

are wild. I favor the latter classification befear of humans with being wild. All animato humans based on experience. If these threatening, the animal learns there is no experiences are threatening or unpleasanlearn to flee and avoid areas frequented bthat conducts research in Antarctica pointcontinent aren’t afraid of people and oftecuriosity, yet they are about as wild an anUnder my proposed definition for wildlifeor husbandry that shield animals from forattempt to mimic natural conditions in a zbe avoided. Likewise, sustained or intensisuch as repeated captures, handling, and if possible, because they could alter naturand unintended ways. While perhaps not habituated to human presence would stilmaintained their independence from suppprovided by humans—despite close and fAt a time when wilderness appears to be increasingly urban society, we should not Yellowstone and the ease of access to its and iconic wildlife for even the most urbaMany visitors fondly remember their expethe rest of their lives; even if some of the were habituated to humans and the condto their inspiration may not have been prshould continue to promote an environmuncontrolled, and visitors can be impresseuninhibited behaviors. As park historian Pthe greatest value of Yellowstone may be wildness—the opportunity for us to be awmaking its own decisions.” 
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Former National Park Service superintendent and longtime Jackson resident John M. Good died Dec. 5, 2019 at home in Meridian, Idaho. He was 95.

Born March 15, 1924, in St. Louis, Good began his National Park Service career in 1951 as a cave guide at Carlsbad Caverns National Park in New Mexico and retired as superintendent of Everglades National Park in Florida in 1981.Born and raised in St. Louis, Good learned his lifelong love of the outdoors spending summers at his aunt and uncle’s farm in the Ozark Mountains of southern Missouri. After serving in the Navy during World War II he attended Washington University in St. Louis for both his bachelor’s and master’s degrees in geology. While on vacation he visited several parks and became interested in working for the National Park Service. He joined the agency in 1951, dedicating his working life to national parks and their mission of preserving natural and cultural resources for public use and enjoyment. He worked at seven parks during his career, including serving as chief naturalist of Yellowstone National Park (1960-68), superintendent of Acadia National Park in Maine (1968-71), deputy superintendent of Yosemite National Park in California (1971-76) and superintendent of Everglades National Park, Florida (1976-81).Highlights of his NPS career include a series of land exchanges in Acadia that solidified park boundaries and serving on the initial board of trustees during the establishment of the College of the Atlantic in Bar Harbor, Maine; working with Yosemite Superintendent Lynn Thompson and Chief Ranger Jack Morehead as the National Park Service faced challenges of a rapidly changing society and visitor demographics in the wake of the Yosemite riot; and protecting Florida Bay by eliminating commercial fishing and initiating the legal efforts that required the state of Florida to acknowledge perpetual water rights for Everglades National Park.

In Memoriam: John Maxwell Good
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After retirement Good finished his field w“Interpreting the Landscape: Recent and Teton and Yellowstone National Parks” wGeological Survey geologist Dr. Ken Piercefor years for the Yellowstone wolf reintroMcIntyre. The success of the reintroductiobecause he knew the key role they play in country.John continued to spend as much time as fishing, cross-country skiing, hiking, campwatching for as long as he could in many around the world.Good is survived by his wife of 45 years, ECarroll; daughter Katherine Good-Smith; grandson John Beck.The family asks that, in his memory, everyour public lands and public access to them 

The Florida Bay work earned him an “attaboy” from Boston Red Sox slugger and avid Florida fly fisherman Ted Williams, who had told him he didn’t think ending commercial fishing could be done.When asked what perspective he could offer wildlife managers of today, John Good, offered these words of advice: “We were so sure. Remember that wonderful line of Charlie Brown’s, ‘Now how can we lose this ball game when we’re so darned sincere?’.. . If you could have gone back and sat in on a ranger conference in 1961, you would have found the same attitude that remains today. That we know what we’re doing. Most people—most reasonable people—will accept that we do. We said that in 1961, we’re saying it now in 1999. I don’t know whether what we’re doing is exactly right. All I remember is that to the Greeks, the ancient Greeks, a cardinal sin was hubris. And hubris was pride. And certainty. And so, I wave my finger from the ancient past and say, beware hubris, beware certainty.”
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Common Name Scientific Name Family

Bacteria Brucellosis Brucella abortus Brucellaceae

Birds Bald eagle Haliaeetus 

leucocephalus

Accipitridae

Golden eagle Aquila chrysaetos AccipitridaePeregrine falcon Falco peregrinus Falconidae

Fish Cutthroat trout Oncorhynchus clarkii Salmonidae

Lake trout Salvelinus namaycush Salmonidae

Insects Toadflax brocade 

moth

 Calophasia lunula Noctuidae

Mammals Bison (buffalo) Bison bison Bovidae

Black bear Ursus americanus UrsidaeCattle (domestic) Bos taurus BovidaeCougar (mountain lion)

 Puma concolor Felidae

Coyote Canis latrans CanidaeDeer " Odocoileus hemionus 

(mule deer) and  O. virginianus (whitetailed deer)"

Cervidae

Elk Cervus canadensis CervidaeGrizzly bear Ursus arctos CarnivoraHorse (domestic) Equus caballus EquidaeMoose Alces alces Cervidae

Common Name Scient

Mountain lion (cougar)

 Puma conc

Mule deer Odocoileus Pronghorn AntilocaprSheep (domestic) Ovis aries Thomson's gazelle

 Eudorcas t

White-tailed deer Odocoileus Wildebeest ConnochaWolf (gray) Canis lupu

Animals

Species in this Issue

Compiled by Karin Bergum

Scientific Name Family

cella abortus Brucellaceae

Common Name Scient

Mountain lion (cougar)

Puma conc

e
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Common Name Scientific Name Family Growth Habit Life Cycle 

Alfalfa Medicago sativa Fabaceae Forb Perennial Introd

Annual wheatgrass

 Eremopyrum triticeum Poaceae Graminoid Annual Introd

Aspen Populus tremuloides Salicaceae Tree Perennial Native

Basin big sage Artemisia tridentata ssp. tridentata Asteraceae Shrub Perennial Native

Big sagebrush Artemisia tridentata Asteraceae Shrub Perennial Native

Bluebunch wheatgrass

 Pseudoroegneria spicata Poaceae Graminoid Perennial Native 

Bluegrass Poa spp. Poaceae Graminoid Perennial -

Bluejoint reedgrass

 Calamagrostis canadensis Poaceae Graminoid Perennial Native 

Bulbous bluegrass Poa bulbosa Poaceae Graminoid Perennial Introd

Canada thistle Cirsium arvense Asteraceae Forb Perennial Introd

Noxiou

Cheatgrass Bromus tectorum Poaceae Graminoid Winter 

Annual

IntrodInvasiv

Clover Trifolium spp. Fabaceae Forb Perennial Introd

Columbia needle grass

 Achnatherum nelsonii Poaceae Graminoid Perennial Native 

Crested wheatgrass

 Agropyron cristatum Poaceae Graminoid Perennial Introd

Dalmation toadflax

 Linaria dalmatica Plantaginaceae Forb Perennial Introd

Noxiou

Dandelion Taraxacum spp. Asteraceae Forb Perennial Introd

Desert alyssum Alyssum desertorum Brassicaceae Forb Annual Introd

Douglas-fir Pseudotsuga menziesii Pinaceae Tree Perennial Native

Draba Draba spp. Brassicaceae Forb Annual Native

Field chickweed Cerastium arvense Caryophyllaceae Forb Perennial Native

Fringed sage Artemisia frigida Asteraceae Shrub Perennial Native

Geranium Geranium spp. Geraniaceae Forb Perennial Native

Greasewood Sarcobatus vermiculatus Sarcobataceae Shrub Perennial Native

Plants
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Common Name Scientific Name Family Growth Habit Life Cycle 

Green rabbitbrush Chrysothamnus viscidiflorus Asteraceae Shrub Perennial Native

Houndstongue Cynoglossum officinale Boraginaceae Forb Biennial Introdu

Noxiou

Idaho fescue Festuca idahoensis Poaceae Graminoid Perennial Native 

Juneberry (Serviceberry)

 Amelanchier ainifolia Rosaceae Shrub Perennial Native

Junegrass Koeleria macrantha Poaceae Graminoid Perennial Native Juniper Juniperus spp. Cupressaceae Conifer Perennial NativeKentucky bluegrass Poa pratensis Poaceae Graminoid Perennial IntroduKochia Bassia scoparia Amaranthaceae Forb Annual IntroduLava aster Ionactis alpina Asteraceae Forb Perennial NativeLodgepole pine Pinus contorta Pinaceae Conifer Perennial NativeLupine Lupinus spp. Fabaceae Forb Perennial NativeMilkvetch Astragalus spp. Fabaceae Forb Perennial NativeMountain big sage Artemisia tridentata ssp. vaseyana Asteraceae Shrub Perennial NativeMountain mahogany

 Cercocarpus Kunth Rosaceae Tree Perennial Native

Needle-and-thread Hesperostipa comata Poaceae Graminoid Perennial Native Oatgrass Danthonia spp. Poaceae Graminoid Perennial Native Oats Avena sativa Poaceae Graminoid Annual IntroduOregon grape Mahonia repens Berberidaceae Shrub Perennial NativeOval-leaf buckwheat (Cushion buckwheat)

 Eriogonum ovalifolium Polygonaceae Forb Perennial Native

Oxeye daisy Leucanthemum vulgare Asteraceae Forb Perennial Introdu

Noxiou

Phlox Phlox spp. Polemoniaceae Forb Perennial NativePussytoes Antennaria spp. Asteraceae Forb Perennial NativeReed grass Calamagrostis spp. Poaceae Graminoid Perennial Native 

Rice grass Achnatherum spp. Poaceae Graminoid Perennial Native 

Rockcress Arabis spp. Brassicaceae Forb Perennial Native

Wild rose (Woods' rose)

 Rosa woodsii Rosaceae Shrub Perennial Native

Rubber rabbitbrush Ericameria nauseosa Asteraceae Shrub Perennial Native

Russian thistle Salsola spp. Chenopodiaceae Forb Annual Introdu
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Common Name Scientific Name Family Growth Habit Life Cycle 

Sagebrush Artemisia spp. Asteraceae Shrub Perennial NativeSalsify Tragopogon dubius Asteraceae Forb Biennial Introdu

Sandberg's bluegrass

 Poa secunda Poaceae Graminoid Perennial Native 

Scarlet globemallow Sphaeralcea coccinea Malvaceae Forb Perennial NativeSedge Carex spp. Cyperaceae Graminoid Perennial Native

Shrubby cinquefoil Dasiphora fruiticosa Rosaceae Shrub Perennial Native

Silver sage Artemisia cana Asteraceae Shrub Perennial Native

Slender-leaf collomia

 Collomia linearis Polemoniaceae Forb Annual Native

Slender wheatgrass Elymus trachycaulus Poaceae Graminoid Perennial Native Smooth brome Bromus inermis Poaceae Graminoid Perennial IntroduSpotted knapweed Centaurea stoebe Asteraceae Forb Biennial Introdu

Noxiou

Sticky geranium Geranium viscosissimum Geraniaceae Forb Perennial Native

Timothy Phleum pratense Poaceae Graminoid Perennial IntroduTufted hairgrass Deschampsia cespitosa Poaceae Graminoid Perennial Native Ventenata grass Ventenata dubia Poaceae Graminoid Winter 

Annual

IntroduNoxiou

Western yarrow Achillea millefolium Asteraceae Forb Perennial Native

Whitebark pine Pinus albicaulis Pinaceae Conifer Perennial NativeWhite coralberry (Snowberry)

 Symphoricarpos spp. Caprifoliaceae Shrub Perennial Native

Willow Salix spp. Salicaceae Shrub Perennial Native

Winterfat Krascheninnikovia lanata Amaranthaceae Forb Perennial Native

Wyoming big sage Artemisia tridentata ssp. wyomingensis Asteraceae Shrub Perennial NativeYellow toadflax Linaria vulgaris Plantaginaceae Forb Perennial Introdu

Noxiou

Karin Bergum is a contract technical editor for Yellowstone Science. Her interest in genetics and plants led her to pursue an undergraduate degree in Agronomy and Seed Science from Iowa State University, and later a Master of Science in Rangeland Ecology from the University of Wyoming. She and her husband Dan spend any free moment outdoors on adventures with their sons Colter and Teddy.
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Being an Effective LeaderP.J. White (adapted from White, 2016)

Iwas probably one of the worst second lieutenants in the history of the United States Marine Corps. Though painful to admit, it was sadly true; as many senior officers pointed out at the time. To 

this day, I marvel at some of the stupid decisions I made. Fortunately, I was a quick study and improved substantially, eventually grasping the lesson that successful leadership is essentially about two things which are equally important: accomplishing the mission and taking care of your people. I have maintained this philosophy through many years in wildlife biology and it has served me well. If you work hard to consistently fulfill these two tenets, you will eventually earn the respect and trust of your co-workers; regardless of what position you occupy in the chain-of-command. To accomplish the mission, the leader of a particular group or project needs to define the problem or task for their coworkers, answer questions and consider ideas, refine a plan based on this input, and then supervise the successful completion of the project. Everyone at every level should work at becoming a better leader by participating in the planning of their daily activities, being prepared to accomplish their assigned tasks, focusing and paying attention to detail during these activities and, as necessary, being creative to solve problems. In addition, everyone needs to take responsibility for their actions. We all make mistakes—acknowledge them and learn from them. Furthermore, try to live your life with honor (do what’s right), courage (do what’s right even when it’s hard), and integrity (be true to yourself and others). It’s not easy and I’ve failed to live up to these ideals many a time, but it’s important to strive to attain them. Successful leadership comes through ideas, planning, supervision, and hard work. The rarest commodity in wildlife biology is an original idea. Wildlife management is often about solving problems and ideas to reach solutions come from being curious and thoughtful about the world around you. Planning involves setting realistic objectives and timeframes and preparing for the inevitable contingencies. 

Detailed planning is essential because, as to Alice in Wonderland, any road will get know where you’re going. In other wordobjectives and a precise process to attain toward the desired outcome. Supervision people, training them, providing guidance letting them use their abilities and ingenuthe while monitoring their progress to enTo take care of their people, leaders need coworkers have the proper training and ewell as a strong commitment to safety. Wactivities, everyone needs to focus on thesurroundings and changing conditions, anEveryone needs to be prepared to implemthings do not go as planned. If anyone obeither rectify it or distance yourself and yothen bring it to the attention of your supefeel right, back away and assess why. Trusare exhibiting unsafe behavior, let them kDon’t remain quiet and watch someone gSome accidents will happen despite every to keep them minor and rare. If someone receive treatment and are taken care of. Iknow as soon as possible. No one should for reporting an injury, no matter how miYou should encourage the reporting of clhighlight a safety concern that needs to bwith others to prevent future injuries. Safa culture in your group; people must beliesuccessful. For example, the United States leave anyone behind, that is not always pessential nevertheless because everyone beverything in their power to live up to it. T
Yellowstone 

commitment; it is absolute and, therefore, reassuring. Obviously, the day-to-day risks taken by wildlife biologists should be far less than our brothers and sisters facing combat in defense of our country and ideals. However, a similar creed is still applicable—everyone should come home safe to their families and friends each day. Last but not least, I appropriated the following bits of advice and ideas regarding leadership from a wide variety of wise people, ranging from my father, Bert White, to the author of the book Don Quixote, Miguel de Cervantes, to the former Chief of the Yellowstone Center for Resources, John Varley, to famous football coach, Vince Lombardi, to the extremely successful businessman, Bill Gates, to the legendary Marine, Chesty Puller. These teachings have been very helpful to me throughout my career, and I hope they will be helpful to you during your journey. Remember, no one will help you if you don’t first help yourself by putting forth maximum effort. 

Know and Be Yourself (strengths, weaknesses, and tendencies) Establish Your Team’s Identity (mission, objectives, and values) Establish a Chain of Command (effective flow of information) Set High Standards with Clear Expectations (motivate and exBe Bold and Decisive (be confident and take calculated risks) Be Prepared (acquire and use the best available information) Plan Ahead and Get Feedback (encourage candor/different viewStrive for Success, Not Perfection (develop simple, flexible planCommunicate and Delegate (empower ingenuity and decision mSupervise (instruct, provide guidance, monitor progress, and debrieAccept Responsibility (don’t make excuses, make corrections) Educate and Train (focus on inexperienced leaders; cross train) Praise in Public, Punish in Private (reward excellence and initiatDevelop a Culture of Safety (believe in it and live it) Don’t Waste Time (focus on the things you can change)

Be Respectful and Listen (consider alternatives before deciding) 

Be Careful with Fraternization (treat everyone fairly; don’t discrBecome Adept at Negotiation (change behaviors to attain resulJust Do It (debate ends when the boss makes a final decision) Take Things in Stride (life’s not fair; deal with unexpected problem
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Allen, K., and K. Hansen. 1999. Geography and exotic plants adjacent 

to campgrounds, Yellowstone National Park, USA. Great Basin Naturalist 59:315-322.

Bangs, E.E., and S.H. Fritts. 1996. Reintroducing the gray wolf to 

central Idaho and Yellowstone National Park. Wildlife Society Bulletin 24:402-413. 

Becker, M.S., R.A. Garrott, and P.J. White. 2013. Scale and perception 

in resource management: integrating scientific knowledge. 

Pages 29-44 in P.J. White, R.A. Garrott, and G.E. Plumb, editors. 

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Sneak Peek

Yellowstone is a land of large mammals and geology. Geology was first - geysers – and this is why Yellowstone was made into a national park. The animals came later, and they came 

with a flourish: bears, bison, elk, and later wolves to name the most famous ones. Of course, sweeping mountain vistas and world class scenery wasn’t bad either. Fish got their share of attention, especially after lake trout infested Yellowstone Lake and precious cutthroat were threatened. Other fish stocks were cherished and nurtured. But what about the birds? They’ve been around too.This is what the next issue of Yellowstone Science is all about - this late discovery of bird riches. Although riches may overstate the situation a little, there is a vast array of birds in the world’s first national park. Songbirds thrive in the grasslands and streamside vegetation, but do struggle in the vast lodgepole forests stretching across the park’s interior. Raptors are another story – 19 species of hawks, falcons, owls, and eagles nest in Yellowstone. More pass through on annual migrations. Water birds are resplendent: common loons, trumpeter swans, American white pelicans, and doublecrested cormorants are somewhat unique and all occupy the park. The anchor for loons and swans in the entire region is the park.All discovered late and competing for attention with the bubbling springs and megafauna in the world’s most famous park. Read what we have learned. An entire issue!

Douglas W. Smith
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