The Magazine of the Arnold Arboretum VOLUME 76 • NUMBER 3

The Magazine of the Arnold Arboretum VOLUME 76 • NUMBER 3 • 2019 CONTENTS

Arnoldia (ISSN 0004–2633; USPS 866–100) 2 The Hybrid Mystique is published quarterly by the Arnold Arboretum Jake J. Grossman of Harvard University. Periodicals postage paid at Boston, Massachusetts. 14 Roaming through Ranges: The Evolution Subscriptions are $20.00 per calendar year of Tree Species Distribution Maps in the domestic, $25.00 foreign, payable in advance. United States Remittances may be made in U.S. dollars, by James Ellenwood check drawn on a U.S. bank; by international money order; or by Visa, Mastercard, or American 28 Taiwan Dispatches Express. Send orders, remittances, requests to Ernest Henry Wilson purchase back issues, change-of-address notices, and all other subscription-related communica- 34 Hurried Journey: Botany by Rail tions to Circulation Manager, Arnoldia, Arnold Jonathan Damery Arboretum, 125 Arborway, Boston, MA 02130- 3500. Telephone 617.524.1718; fax 617.524.1418; 40 Sax Pine: A Hybrid Left Behind e-mail [email protected] Jared Rubinstein Arnold Arboretum members receive a subscrip- tion to Arnoldia as a membership benefit. To Front and back cover: Andrew Robeson prepared become a member or receive more information, maps for Charles Sprague Sargent’s Report on the please call Wendy Krauss at 617.384.5766 or Forests of North America (Exclusive of Mexico), email [email protected] published in 1884. This map shows “relative average density of existing forests” across the country, which Postmaster: Send address changes to was calculated in the number of cords of lumber that Arnoldia Circulation Manager could be harvested per acre. Regions marked with The Arnold Arboretum Roman numeral I were estimated to yield less than 125 Arborway one cord per acre, while those marked with VII (the Boston, MA 02130–3500 highest in the eastern United States) were estimated Jonathan Damery, Associate Editor at fifty to one hundred cords. Map from Arnold Arbo- Andy Winther, Designer retum Archives.

Editorial Committee Inside front cover: Railroads allowed Ernest Henry Wilson rapid access to collecting locations in Taiwan. Anthony S. Aiello On March 12, 1918, he photographed a man stand- Peter Del Tredici Michael S. Dosmann ing on railroad tracks with a large specimen of Vitex William (Ned) Friedman quinata (a member of Verbenaceae, then known as Jon Hetman V. heterophylla) reaching overhead. Notice the Julie Moir Messervy epiphyte-laden branches. Photo from Arnold Arboretum Archives. Copyright © 2019. The President and Inside back cover: The Sax pine (Pinus monticola × Fellows of Harvard College parvifloravar. himekomatsu) retains the blue foliage of the Japanese white pine, one of the hybrid parents. Cones were observed on accession 266-46*F. Photo by Jonathan Damery. GROSSMAN, J. J. 2019. THE HYBRID MYSTIQUE. ARNOLDIA, 76(3): 2–13

The Hybrid Mystique

Jake J. Grossman

ybrids, the results of successful breed- for the biological species concept due to their ing between two parents of different wanton tendency to hybridize (Burger, 1975)— Hspecies, occur frequently in nature, we might say that there is evidence of red oak yet are perhaps most familiar to us when they (Quercus rubra) introgression into a stand of result from human intervention. We encoun- northern pin oaks (Q. ellipsoidalis). These pin ter in our intentionally cultivated hybrids the oaks will still be pin oaks, but perhaps with utility of the mule, the stateliness of the Lon- some hidden genetic diversity and leaves or don plane tree, and the sensuous smells and bark that look, well, just a little bit different. tastes of myriad vegetables and fruits, including The ubiquity of such situations has led biolo- broccolini and the tangelo. These remarkable gists to formulate the idea of hybrid complexes examples are of our own making, but hybridiza- or zones: sets of species or populations in which tion between closely related species is perhaps rampant interbreeding has produced a messy the norm rather than the exception in nature. gradient of similar organisms, rather than dis- Though hybrid offspring are sometimes sterile crete sets. Our cultivated citruses represent one and can be visually distinct from their parents such complex, in which ten progenitor species (like mules), they are just as likely to be fer- in southeast Asia and Australia have given rise, tile and to pass unnoticed by us. These cryptic through hybridization, to dozens of domesti- hybrids, diagnosable only through genetic test- cated taxa (Wu et al., 2018). ing, breed with each other or with individuals And so, when I began my own foray into of their parent species (in a process called back- the world of hybrid aspens (Populus), I risked crossing), giving rise to new hybrid progeny. wading into a thicket of biological questions Over generations, such interbreeding consoli- that could have been difficult or impossible to dates novel hybrid traits, sometimes leading to resolve. Fortunately, I was a first-year graduate the formation of new species. Because what student, a neophyte far more optimistic than I counts as a species is, after all, merely conven- am now when it comes to tackling a new proj- tional, it could be said that we humans, the ect. What follows is a story of a journey through descendants of interbreeding between Nean- which a team of ecologists and evolutionary derthals and early Homo sapiens, are just as biologists, myself included, tried to track down much hybrids as the most luscious of tangelos. the truth about a putative hybrid. To do so, we Perhaps foremost among the natural world’s traveled throughout the Midwest and dug deep “hopeful monsters”—a term that geneticist into the natural history of the Niobrara River Richard Goldschmidt coined in 1940 for evo- Valley, a relictual ecoregion left behind by the lutionary transformations that occur through retreat of glaciers at the end of the last Ice Age. rare but large-scale mutation—hybrids often captivate and delight human observers.1 A biotic crossroads: Yet hybridization does not always precipitate The Niobrara River Valley the formation of a new species. In natural popu- Heading into the Nebraska Sandhill region lations, hybrids are frequently formed, only to along the state’s border with South Dakota, new be subsumed, through backcrossing, into their visitors might be surprised to plunge from corn- parental stock. This process—called introgres- fields and pastures stretching as far as the eye sion—results in the enrichment of the gene can see into forested canyons hugging a cool, pool of the predominant species with genetic inviting river. Originating on the eastern edge material from close relatives. So, in the case of Wyoming, the Niobrara River runs from west of oaks—described as particularly problematic to east across the northern quarter of Nebraska Smith Falls Aspen 3 NATIONAL PARK SERVICE PARK NATIONAL SERVICE PARK NATIONAL

Smith Falls aspens (Populus × smithii, right) along the Niobrara River, in northern Nebraska, are natural hybrids of two common North American aspen species. It shares habitat with northern species like paper birch (Betula papyrifera) and western species like ponderosa pine (Pinus ponderosa), both shown at left.

before being subsumed in the Missouri River in pines are among over a dozen western vascular the northeastern corner of the state. The can- plant species whose distributions extend all the yons found between the river’s banks and the way into Nebraska, following the biotic east- surrounding matrix of arid short- and mixed-grass west highway formed by the Niobrara River. A prairie constitute the Niobrara River Valley. second look confirmed that this traffic moved For an eager observer, this valley presents in both directions: bur oaks (Quercus macro- more than just a respite from Nebraska’s hot, carpa) and silver maples (Acer saccharinum) dry uplands. Rather, as Midwestern botanist made unusual appearances for species that Charles Bessey first observed in 1887, the Nio- generally cannot be found in great abundance brara River Valley is a “meeting-place for two further west than the meeting of the prairies and floras,” a unique location in North America forests in Minnesota and Iowa. It also became in which East and West comingle. Born and clear that the cooler, north-facing slopes of the raised in Arizona, I had spent about five years valley, in particular, offered suitable habitat for living in the Midwest by the time I first vis- species generally found further north, includ- ited the valley. When I arrived by car from St. ing cosmopolitan but drought-intolerant paper Paul, Minnesota, where I had just begun my birch (Betula papyrifera). The same pattern— doctoral studies as a plant ecologist, it felt a confluence of biota typical of the montane like I was seeing old friends again after a long West, the deciduous forests of the East, and the absence. Most noticeably, stands of ponderosa boreal forests of the North—holds for herba- pine (Pinus ponderosa), a decidedly western ceous plants, insects, and vertebrates as well species, greet visitors to the Niobrara. These (Kaul et al., 1988). 4 Arnoldia 76/3 • February 2019 NATIONAL PARK SERVICE PARK NATIONAL

The hills and canyons of the Niobrara River Valley have provided shared habitat for an unusual combination of eastern and western species—plants and animals, alike.

Of aspens, poplars, popples, and out west (P. fremontii), and northwestern black cottonwoods cottonwood (P. trichocarpa), the first tree spe- Any exhaustive flora of the Niobrara is bound cies to have its genome sequenced. Most spe- to mention aspens, meaning species of the cies in the genus share traits with each other genus Populus. These trees go by a plethora of and with other members of the willow family common names: aspens, poplars, popples, and (Salicaceae): they are dioecious, meaning that cottonwoods—names which do not neatly map male and female flowers are borne on separate on to the current phylogenetic characterization trees and have simple leaves and relatively short of six sections within the genus (Hamzeh and lifespans (often less than one hundred years). Dayanandan, 2004). In North America, native Many species have circumboreal distributions; species from section Populus, and some from they are generally cold tolerant, but vulnerable Tacamahaca, are referred to as “aspens,” “pop- to hot and dry conditions. lars,” or “popples.” These include the ubiqui- Aspens writ large have captured the imagi- tous quaking aspen (P. tremuloides), its close nation of botanists and the general public alike relative bigtooth aspen (P. grandidentata), and by virtue of their propensity for perpetuation cold-tolerant basalm poplar (P. balsamifera). through vegetative means. Most importantly, The species we know as “cottonwoods” are this means that a given aspen tree can, regard- restricted to Aigieros and also to Tacamahaca, less of sex, produce new, genetically identical and these include, most famously, eastern cot- clones of itself. These new stems, often called tonwood (P. deltoides, one of the largest trees “suckers,” emerge from rhizomes, under- east of the Mississippi), Fremont cottonwood ground stems that spread in parallel to the Smith Falls Aspen 5 ARNOLD ARBORETUM, US FOREST SERVICE, AND GIS COMMUNITY ARNOLD ARBORETUM, US FOREST SERVICE,

The distributions of quaking aspen (Populus tremuloides, shown in gray) and bigtooth aspen (P. grandidentata, shown in green) present a curious question: how could a hybrid between the two species occur in northern Nebraska, where one parent is excep- tionally rare and the other is completely missing?

soil surface. When a rhizome’s buds encounter to a few tiny islands, usually growing in dense moist, warm conditions, a small shoot heads clumps around wetlands. These stands are rel- upward, sprouting leaves and emerging from ics, groups of trees left behind as the global the soil as though a seed had germinated in climate warmed over the last ten thousand that exact spot. But these suckers grow faster years. At the end of the Pleistocene Ice Age, than a typical seedling ever could, drawing on aspen species, as with other cold-hardy trees, resources from their parental plant and bypass- were probably quite common across this mas- ing seedling-hood in a mad dash for growth. sive inland plain (Wright et al., 1985), but their These clonal offspring can, over time, become ranges retracted as the climate became more separated from their parents through the arid. Stands of quaking aspen in central Can- decay of the rhizome, but they remain genetic ada and in the biotic highways of the Niobrara clones, such that what often appears to be a River Valley provide the only linkages between stand of aspen trees is, in reality, a single indi- eastern and western populations for that vidual, connected, to varying extents, under- species. My PhD advisor had secured funding neath the soil. from the National Parks Service—the Niobrara is a National Scenic River—to study one such The mystery of the Smith Falls aspens stand, a rare, and therefore locally famous, col- Aspen stands are vanishingly rare, if not alto- lection of aspens centered around Smith Falls gether absent, in the Great Plains. Quaking State Park, near Valentine, Nebraska. In 2013, aspens (Populus tremuloides) are nearly the sole we headed out for the first time to see these representatives in the region but are restricted trees for ourselves. 6 Arnoldia 76/3 • February 2019 PAUL WRAY, IOWA STATE UNIVERSITY, BUGWOOD.ORG UNIVERSITY, STATE IOWA WRAY, PAUL BECCA MACDONALD, SAULT COLLEGE, BUGWOOD.ORG BECCA MACDONALD, SAULT NATIONAL PARK SERVICE PARK NATIONAL

Many morphological characteristics for the Smith Falls aspens (below) show intermediate traits between the parent species, including the shape and number of teeth on the leaf margins and the degree of leaf and bud pubescence. Quaking aspen (Populus tremuloides) is shown at top left, bigtooth aspen (P. grandidentata) at top right. Smith Falls Aspen 7

When we began, it was immediately clear that unusual, isolated stand of quaking aspen. So, the aspens at Smith Falls bear a great resem- an important first step in our research would blance to quaking aspens. They have lovely be to compare the genetics and morphology of white stems and dark green, heart-shaped, the Smith Falls aspens to that of known quak- finely toothed leaves. They grow in clumped ing and bigtooth trees. stands, indicating spread by rhizomes, with no Our research group collected leaf samples, singletons off on their own. We found these from which we could extract DNA, from all ten trees growing in a string of ten stands extending stands of Smith Falls aspens. We also dug up along the Niobrara River Valley, from Nature rhizomes to produce cloned suckers and planted Conservancy holdings in the east to private these suckers in a common garden at a research property in the west. The stands in between station in Minnesota. There, we could perform these two locations are one of the crown jewels experiments on them without harming the of Smith Falls State Park and are well known precious Niobrara trees. For the sake of com- to its many visitors, who also come to raft the parison, we also drove all over the Midwest, Niobrara River, camp out along its banks, and collecting leaf and rhizome samples from quak- see the eponymous waterfalls. The aspen stands ing aspens in the Black Hills of South Dakota are confined to the cool, north-facing banks of and the Sandhills of Nebraska, from bigtooth the river, and they’re undeniably beautiful trees. and quaking aspens along their western range But, as aspen fanatics, we agreed with what edge in Minnesota and Iowa, and from both spe- we’d already heard about them: they seemed cies within the interior of their distributions in somehow different than the quaking aspens so Minnesota and Wisconsin. familiar to us in Minnesota. Their bark, though Our assessment of the genetics and physiol- light-colored, seemed rather green, and their ogy of the aspens took place over two years at leaves were rather large, with fewer and larger the University of Minnesota campus. We used teeth, compared to a typical quaking aspen. microsatellite genotyping—the same tech- Indeed, these trees had long been held by local nology that allows for DNA fingerprinting in botanists and natural historians to be hybrids humans—to understand which trees we had between locally rare quaking aspen and bigtooth sampled were distinct individuals and which aspen—a species whose eastern range edge is were clones. This work, as well as sequencing of currently estimated to fall around 375 miles parts of our sampled trees’ chloroplast genomes, (600 kilometers) to the east, near Ames, Iowa. was possible thanks to the full genome for black We knew that quaking and bigtooth aspen cottonwood (Populus trichocarpa), which was hybridize naturally within their range— produced by an international team of dozens of renowned forest ecologist Burton “Burt” Barnes’s biologists led by Oak Ridge National Labora- seminal work documented many such stands tory’s Gerald Tuskan in 2006—the first whole in Michigan (1961)—but the thought of this genome project carried out for a tree species. hybrid having occurred naturally so far outside In our physiological experiments, we pushed the distribution of one of its putative paren- stems and leaves from our common garden trees tal species struck me, at least, as somewhat to the brink. We measured them exhaustively, scandalous. Aspen pollen is wind-distributed and we then dried them out and froze them and can travel long distances, but there is to mimic climate change-induced drought and no evidence of successful pollination events post-budbreak freezes. We also tracked their occurring when around 375 miles separate phenology—the timing of their leafing out and male and female plants. As such, I expected loss of leaves in our common garden. that the reputation of the Smith Falls aspens as hybrids was nothing more than understand- An Ice Age relic able wishful thinking. After all, bark and leaf The results of our genetics work (Deacon et traits can be plastic, and a more parsimonious al., 2017) left me picking my jaw up from the explanation of the unusual appearance of the lab bench. Our first finding struck an ominous Niobrara trees was that they were simply an tone: the Smith Falls aspens are shockingly 8 Arnoldia 76/3 • February 2019 ARNOLD ARBORETUM, NATIONAL PARK SERVICE, NEBRASKA GAME AND PARKS COMMISSION, AND GIS COMMUNITY NEBRASKA GAME AND PARKS SERVICE, PARK ARNOLD ARBORETUM, NATIONAL

Genetic analysis of the ten aspen groves at Smith Falls (marked in red) revealed that only three genetic individuals occurred at the site. In some cases, these clones spanned opposite sides of the large canyon (and namesake waterfall) that bisects the park, suggest- ing aspens were once more widespread at the site.

undiverse. We are confident that, across all ten we observed offer some support for the clas- stands at the site, any given tree belongs to one sification of these trees as F1 hybrids, meaning of three genotypes. This means that three origi- they are the first-generation offspring between nal seedlings produced through sex have given two parents of different species, like mules. rise, through rhizome suckering, to all of the Our study of leaves collected from com- extant aspens in the area. We found genetically mon garden trees supported our finding that identical individuals growing on opposite sides the Smith Falls aspens were in fact hybrids of of ravines and in stands separated by hundreds quaking and bigtooth parents (Deacon et al., of meters. It appears, then, that these particular 2017). Use of a dichotomous key to distinguish trees rely almost exclusively on asexual suck- between these species will often require inspec- ering for reproduction. More shocking still, at tion of the pubescence and margins of the leaves the nuclear level, the Smith Falls aspens shared of the specimen in question. Quaking aspens genetic information with both quaking aspen tend to be glabrous with many small teeth on and bigtooth aspen, confirming that they are a their leaf margins. Bigtooth aspens tend to be hybrid between these parents—a hybrid chris- pubescent with fewer, larger teeth. Barnes’s tened, appropriately enough, Populus × smithii. work on Populus × smithii tells the same story. Evidence from chloroplast DNA suggested that Though we documented many subtle differ- bigtooth aspen, the species now not found until ences between leaves of the two species in our the middle of Iowa, was probably the mater- systematic analysis, our findings contributed nal parent, with pollen coming from quaking to the current consensus: pubescence and tooth aspen. Furthermore, patterns of genetic mixing number are the best way to tell them apart. And Smith Falls Aspen 9

leaves from P. × smithii trees grown in Min- Specter of climate change nesota from Nebraska-collected rhizomes were Our grant from the National Parks Service perfectly intermediate between their putative enabled us to go beyond determining the parents in these two traits. genetic identity of these trees. We also used Taken together, these findings suggest the our common garden to study their disturbing rather shocking story that, at some point demographic decline. State managers and con- when both bigtooth and quaking aspen were servationists had noted that existing aspens locally abundant in the Niobrara River Valley— looked stressed and that new trees either were probably between three and six thousand years not sprouting or were quickly consumed by ago—the two species hybridized. Both par- deer before outgrowing their reach. We wanted ents went locally extinct (and bigtooth van- to understand the vulnerability of the Smith ished from the entire region), but their hybrid Falls aspens to two forms of physiological stress remained, reproducing vegetatively through likely to be concomitant with climate change. rhizomes rather than through flowers and seeds. The first is straightforward: climate change in Despite considerable environmental change— the region is likely to lead to more arid con- the climate in this region was warming and ditions, imposing drought stress on the vul- drying long before our present human-induced nerable, mesic species of the Niobrara River bout of climate change—these aspens hung on, Valley. The second is less so: because the forces perhaps shrinking in their distribution, but not that cause this warming do not necessarily pre- disappearing from one small stretch of the Nio- vent late-winter cold snaps, even if spring tem- brara River Valley. As such, these aspens are a peratures arrive earlier, plants can leaf out in true relic of a past climate and a unique genetic response to an early spring, then get hit with a treasure of the region. freeze after budbreak. Such post-budbreak freez- PHOTOS BY JAKE J. GROSSMAN

Each of the three aspen genotypes at Smith Falls is a first-generation hybrid, suggesting that the aspen trees found today at the site have descended through many generations of vegetative suckering, rather than seed reproduction, from the original hybrids. Vegetative suckering in aspens occurs via underground rhizomes, which the author showcases above. 10 Arnoldia 76/3 • February 2019 “BUFFALO” BRUCE MCINTOSH AND WESTERN NEBRASKA RESOURCES COUNCIL “BUFFALO”

Large eastern red cedars (Juniperus viginiana) have encroached on the aspen groves at Smith Falls. This photo was taken before an intensive volunteer effort removed a large number of cedars, some shown in the midground of this forest. Ponderosa pine (Pinus ponderosa) rises in the background.

ing can range from damaging to catastrophic, are likely to experience during March and April potentially killing vulnerable tissues and lead- storms. They were not substantially injured by ing to whole-plant death (Anderegg et al., 2015). this, suggesting that drought threatens aspens Our exploration of the aspens’ vulnerability in the Niobrara River Valley more than late- to climate change, currently in review, resulted winter cold snaps. Interestingly, in our mea- in some bad and some good news. Unsurpris- surements of spring phenology—the transition ingly, given aspens’ low level of drought toler- from dormancy to budbreak—we also found ance, we found quaking, bigtooth, and hybrid that the Smith Falls aspens were intermedi- aspens to be vulnerable to drought-induced ate between quaking and bigooth aspen. Our cavitation, the formation of air bubbles in stem findings echoed previous work showing that xylem. These bubbles, in quantity, disrupt quaking aspens break bud about a week faster waterflow in trees’ vascular systems, like holes than bigtooths; fittingly, we observed that their in a straw. They can, ultimately, lead to total hybrid offspring tended to leaf out in between hydraulic failure and tree death. Quaking aspen the two parental species. Yet, compared to other was slightly more vulnerable to this type of regional conspecifics, all three groups of aspens drought damage than bigtooth aspen, and their generally leaf out around the same time. hybrid was intermediate. More generally, the hybrid aspens shared some drought-tolerance An aspen in a juniper’s world traits with quaking aspen, others with bigtooth Though our determination that the Smith Falls aspen, and, in other cases, was intermediate aspens are in fact hybrids has proven fascinating between the two. But all three taxa showed a and satisfying, thornier questions remain about limited capacity to resist the challenges likely their future. Locally, the Smith Falls aspens are to occur in a warming and drying climate. being outcompeted by neighboring trees, espe- The story surrounding post-budbreak freez- cially eastern red cedars (Juniperus virginiana). ing was simpler and rosier. We froze growing Quaking and bigtooth aspens are tolerant of stems and leaves at temperatures equivalent to low-intensity fires but intolerant of shade. Fire and lower than those that aspens in Nebraska exclusion has, therefore, been catastrophic for Smith Falls Aspen 11 “BUFFALO” BRUCE MCINTOSH AND WESTERN NEBRASKA RESOURCES COUNCIL “BUFFALO”

“Buffalo” Bruce McIntosh of the Nebraska Wildlife Federation leads a juniper removal initiative at Smith Falls. aspens, whether at Smith Falls or more broadly encounter a greater risk of climate-induced across the West. Because cedars are fire intoler- extirpation in the Great Plains than they have ant but drought tolerant, they have capitalized faced since the end of the last Ice Age. on our modern tendency to suppress and pre- We might ask, then, what the future holds vent fires. Locally, managers have fought this for the Smith Falls aspens and for other glacial cedar encroachment by instigating prescribed relics in the region. The answer to this ques- burns, clearing cedars, and creating barriers to tion depends on management. Stands of quak- deer browsing on aspens. As a result, sucker- ing aspen, paper birch (Betula papyrifera), and ing is on the rise in some stands, producing a other drought-sensitive trees can probably be new cohort of healthy aspens (Robertson et al., protected through active steps to shield them 2018). Yet cedar removal and prescribed burns from direct climate stress and competition from are expensive and will need to be repeated peri- more drought-adapted neighbors. In addition to odically to keep aspens abundant at Smith Falls. prescribed burns, possible management prac- Globally, climate change is also likely to tices include removal of competitors, use of reshape the distribution of aspens across North exclosures to reduce grazing, targeted plant- America. Nebraska is expected to experience ing, and conservation of local groundwater. For climate warming in the decades to come, in species such as the aspens, which can be more tune with the current global commitment to easily propagated through rhizome cuttings three to four degrees of warming. And though than from seed, collection of rhizomes and rainfall in the region will likely remain stable in propagation of suckers represents one pathway absolute quantity, rain and snow will fall more toward conservation of unusual, threatened sporadically, producing longer and more fre- germplasm. At present, private individuals quent periods of drought. None of this is good and institutions may be able to assist with the news for aspens in the region. Given histori- migration of the Smith Falls aspens by purchas- cal changes in the distribution of quaking and ing commercially available nursery stock. Faller bigtooth aspen, observations colleagues and I Landscape, in York, Nebraska, presently sells have made suggest the Smith Falls aspens will clonal trees produced through suckering from 12 Arnoldia 76/3 • February 2019

their flowers are fertile. Genetic evidence certainly suggests that no new trees have been born from seeds at the site for a very long time. And the Smith Falls aspens are beset by envi- ronmental challenges rang- ing from the hyperlocal to the global. Unfortunately, the Smith Falls aspens may simply have survived by demographic good fortune, constituting an evolution- ary dead end, rather than a way forward. Yet this is a rather pes- simistic view, and, having “BUFFALO” BRUCE MCINTOSH AND WESTERN NEBRASKA RESOURCES COUNCIL “BUFFALO” grown rather fond of the aspens at Smith Falls dur- ing my time working with them, I think their conserva- The fate of the Smith Falls aspens under climate change will likely parallel the fate tion is justified. As unusual of other drought-intolerant populations in the region, including this grove of quaking aspen (Populus tremuloides), south of Smith Falls. hybrids that have persisted despite millennia of climate rhizomes collected at the site (marketed under change—whether by chance or due to some the cultivar name ‘Ice Age’).2 More broadly, particular adaptation we did not measure—they any efforts to stabilize the global climate, if our represent a potential genetic resource. As such, society is willing and able to undertake them, they may be candidates for assisted migration: will also benefit Midwestern aspens, among transplantation from their current, imperiled many other species. location to one that will be more appropriate in the coming centuries of a climate determined Hopeful monsters or dead ends? by human-induced changes. Propagation of Like other natural hybrids, the Smith Falls these trees in cooler and wetter climates well aspens have been heralded, at least locally, as within the current ranges of their parent species uniquely adapted to their surroundings. It is might allow them to flourish while also buy- tempting to assert that these trees, by virtue ing time for intentional propagation of second- of their longevity, may illustrate one strategy generation hybrids through breeding with other for persistence in a warming, drying climate. Popolus × smithii or backcrossing. Yet findings from our research do not support Regardless, we would be wise to remember this narrative. Indeed, these hybrids are unique, that the story of evolution in response to a and worthy of study insofar as they constitute warming climate has occurred many times in an evolutionarily unusual relic from a past the history of life, and it often produces messy climate. But as noted above, these trees rep- stories like that of the Smith Falls aspens. resent essentially three genetic individuals What appear to us to be non-adapted (or even that have probably been cloning themselves maladapted) trees may hold the key to surviv- for thousands of years. Though we have very ing and thriving in a future climate. After all, recently received second-hand confirmation the common ancestor of modern aspens and that the trees do flower in some years, we do willows had likely evolved during the earth’s not know the sex of each clone, or whether last period of extreme warming, some fifty-five Smith Falls Aspen 13

million years ago, when the tropics extended Bessey, C. E. 1887. A meeting-place for two floras. Bulletin up to the North Pole (Manchester et al., 2006). of the Torrey Botanical Club, 14: 189–191. Though the fate of quaking and bigtooth aspens Burger, W. C. 1975. The species concept in Quercus. and their hybrids is uncertain, the aspen lin- Taxon, 24:45–50. eage is likely to survive contemporary climate Deacon, N. J., J. J. Grossman, A. K. Schweiger, I. Armour, change. And so, whether hybrid aspens are best and J. Cavender-Bares. 2017. Genetic, thought of as hopeful monsters or evolution- morphological, and spectral characterization ary dead ends is ultimately unknowable. But of relictual Niobrara River hybrid aspens. American Journal of Botany, 104: 1878–1890. as an unlikely yet arguably successful hybrid myself, I’m inclined to give them the benefit Goldschmidt, R. 1940. The material basis of evolution. of the doubt. New Haven, CT: Yale University Press. Hamzeh, M., and S. Dayanandan. 2004. Phylogeny of Acknowledgements Populus (Salicaceae) based on nucleotide sequences of chloroplast trnT-trnF region and The original research reported in this article was conducted nuclear rDNA. American Journal of Botany, collaboratively at the University of Minnesota—Twin 91: 1398–1408. Cities with Jeannine Cavender-Bares, Nick Deacon, Anna Schweiger, and Isabella Armour. We were funded Kaul, R. B., G. E. Kantak, and S. P. Churchill. 1988. The by National Park Service grant #191779 to Jeannine Niobrara River Valley, a postglacial migration Cavender-Bares, Mark Dixon, and Molly Nepokroeff. corridor and refugium of forest plants and Jeffrey Carstens, a horticulturist and curator of woody and animals in the grasslands of central North herbaceous plants at the USDA’s North Central Regional America. The Botanical Review, 54: 44–81. Plant Introduction Station in Ames, Iowa, played an Manchester, S. R., W. S. Judd, and B. Handley. 2006. absolutely essential role in guiding our collections of Foliage and fruits of early poplars (Salicaceae: Midwestern aspens, especially along the species’ range Populus) from the Eocene of Utah, Colorado, edges in Iowa. “Buffalo” Bruce McIntosh of the Nebraska and Wyoming. International Journal of Plant Wildlife Federation and Joseph Zeleznik at North Science, 167: 897–908. Dakota State University also provided essential help with collections in Nebraska and northern Minnesota, Robertson, J. M., A. R. Cahlander-Mooers, and M. D. respectively. Three photographs in this article came from Dixon. 2018. Effects of management treatments the video “Fighting for Survival: The Ancient Aspen on regeneration of a geographically disjunct, of the Niobrara Valley,” produced by “Buffalo” Bruce relictual hybrid aspen (Populus × smithii) McIntosh, Rod Jensen, and The Great Plains Motion population in the central Great Plains, USA. Picture Company. Environmental Management, 62: 906–914. Tuskan, G. A, S. Difazio, S. Jansson, J. Bohlmann, Notes I. Grigoriev, U. Hellsten,… D. Rokhsar. 2006. 1 It should be noted that the chimaeras resulting from The genome of black cottonwood, Populus the almost unbelievable process of interspecies grafting trichocarpa (Torr. & Gray). Science, 313: (e.g. apples, pears, grapes, roses, citrus, mangos, stone 1596–604. fruit, and others, not to mention the introduction of certain porcine organs into human bodies) certainly Wright, H. E., J. C. Almendinger, and J. Grüger. 1985. give more integrated hybrids a run for their money in Pollen diagram from the Nebraska Sandhills the realm of public interest. and the age of the dunes. Quaternary Research, 2 Aspen enthusiasts can also purchase from them a 24: 115–120. very robust and aesthetically pleasing quaking aspen Wu, G. A., J. Terol, V. Ibanez, A. López-García, E. genotype, ‘NE Arb’, which was collected from a now- Pérez-Román, C. Borredá,… M. Talon. 2018. extinct stand elsewhere in Nebraska. Genomics of the origin and evolution of Citrus. Nature, 554: 311–316. References The maps in this article were created using ESRI, USGS, Anderegg, W. R. L., A. Flint, C. Y. Huang, L. Flint, J. A. Berry, F. W. Davis, J. S. Sperry, and C. B. Field. USFS, NGA, NASA, CGIAR, N Robinson, NCEAS, NLS, 2015. Tree mortality predicted from drought- OS, NMA, Geodatastyrelsen, Rijkswaterstaat, GSA, induced vascular damage. Nature Geoscience, Geoland, FEMA, Intermap and the GIS user community. 8: 367–371. Barnes, B. V. 1961. Hybrid aspens in the Lower Peninsula Jake J. Grossman is a Putnam Fellow at the of Michigan. Rhodora, 63: 311– 324. Arnold Arboretum. ELLENWOOD, J. 2019. ROAMING THROUGH RANGES: THE EVOLUTION OF TREE SPECIES DISTRIBUTION MAPS IN THE UNITED STATES. ARNOLDIA, 76(3): 14–27

Roaming through Ranges: The Evolution of Tree Species Distribution Maps in the United States

James Ellenwood

s a teenager, in the 1970s, I traveled with Little’s maps are now included on the Wiki- my siblings across the United States pedia pages for most—if not all—of the tree Aand Canada on a few multi-week road species that he documented. trips, camping and visiting National Parks and In 2007, however, I began working with col- Forests. Along the way, I became fascinated by leagues at the United States Forest Service to how different trees grow in different places— project the potential for forest mortality due the tall, narrow-crowned Engelmann spruce to insects and diseases fifteen years into the (Picea engelmannii) found in the high eleva- future. This involved building thousands of tions of the northern Rocky Mountains (which models based upon remotely sensed imagery, were still snow packed in the middle of June) environmental variables, and observations from and the incense cedar (Calocedrus decurrans) field plots. After many trials and iterations, we showing off its brilliant red bark on the west- recognized a need to bound the modeled maps ern slope of the Sierras. The local tree species, by known tree distributions, but we knew that I realized, were as distinct as the terrain— Little’s maps couldn’t be used for this type of patterns that emerged over millions of acres analysis. For instance, if we were attempting and thousands of miles. The quest for adventure to understand the threat of emerald ash borer and the desire to see the natural world drove my (Agrilus planipennis) on populations of white ambitions, facilitated by recently completed ash (Fraxinus americana)—a widespread for- interstate highways and a personal automobile. est species in eastern North America—Little’s Ecological patterns that were once relatively map would suggest that white ash was equally difficult to see now emerged, much like the prevalent in New York and Illinois, given that transition from still frames to movie frames, via both states fall entirely within the range. Yet easy roadside stops to get into the wilds. New York is widely forested, while Illinois is Around this exact same time, these funda- extensively cultivated. As a result, white ash mental biological patterns were being syn- populations would be much more fragmented thesized into a comprehensive set of North in the western portion of its range, and Little’s American tree distribution maps by a bota- maps did not reveal this trend. Clearly new nist at the United States Forest Service named information was needed. Elbert Little Jr. These maps were published in a six-volume set, collectively titled the Atlas of Original Maps United States Trees, which covered around 720 The history of mapping North American tree species. Each map included shapes that repre- distributions is an ongoing narrative of collabo- sented the maximum extent of the distribution ration on a national scale, but the evolution of for a single species. Little and his collaborators these maps also reveals how cultural values (and developed these by drawing an outline around even politics) factor into seemingly straight- locations obtained from numerous published ahead descriptive botany. My team began and unpublished sources, as well as personal working on new distribution maps because of knowledge. For decades, Little’s maps have environmental concerns about the globaliza- served as the definitive source for this distribu- tion of insects and diseases, an issue that wasn’t tion information. I referenced them as a student remotely part of the scientific consciousness at the State University of New York’s College in 1880, when Charles Sprague Sargent, the of Environmental Sciences and Forestry in founding director of the Arnold Arboretum, was the early 1980s. And digital reproductions of leading an initiative to describe and inventory Species Distribution Maps 15 UNITED STATES FOREST SERVICE, FOREST HEALTH TECHNOLOGY ENTERPRISE TEAM FOREST HEALTH FOREST SERVICE, UNITED STATES

This map for white ash (Fraxinus americana), published in the National Individual Tree Species Atlas (2015), com- pares a classic distribution prepared by Elbert Little Jr. (light purple) with a new modelled distribution (dark purple). forested landscapes for the 1880 United States a team of botanists and natural history enthu- Census. Rather, at that point in time, the pri- siasts who traveled through specific regions, mary driver for this kind of distribution map- reporting on the composition of the forests. ping was related to economic interests. Most of the resulting distribution information Sargent compiled information for about 412 was text-based, but the report also included tree species, which appeared in a voluminous several types of maps: One set showed the final report, published in 1884. Some of this extent of forested landscapes for individual information came through personal field obser- states. Another set, included as a large-format vations, but Sargent also enlisted the support of portfolio, showed the distribution of genera, 16 Arnoldia 76/3 • February 2019

like pines (Pinus) or oaks (Quercus), on a conti- more detailed representation, and the maps nental scale, with monochromatic shading used also indicated “regions from which Mercantile to indicate the number of species in each loca- Pine has been removed.” Farther west, indi- tion. All the maps were prepared by Andrew vidual species were not tracked on the state Robeson, Sargent’s brother-in-law. maps, which instead showed the density of for- It is particularly interesting to look at how ests. Likewise, the supplementary map for all the census report renders a single economi- pines indicated only the density (essentially a cally important species, like the long-leaf pine heatmap) rather than showing the ranges for (Pinus palustris). Sargent called the species “a individual species. As such, if someone wanted tree of first economic value” and described a to determine the scattered range for something distribution that spanned from southeastern like the whitebark pine (P. albicaulis), which Virginia, through the Gulf states, and into east- favors subalpine regions in the western moun- ern Texas, “rarely extending beyond 150 miles tains, the text-based descriptions would have from the coast.” On maps of the correspond- been the best resource. Of course, individual ing states, long-leaf pine was singled out for species maps would have required many more ARNOLD ARBORETUM ARCHIVES

Charles Sprague Sargent’s 1884 census report included forest maps for individual states. For South Carolina, the dis- tribution of two species of long-leaf pine (both now recognized as Pinus palustris) are shown in green. Commercially harvested forests (shown in burnt orange) emanate from the coast and along transportation corridors. Species Distribution Maps 17 ARNOLD ARBORETUM ARCHIVES

The census publication included sixteen large-format maps, including one showing the density of pine species. The dark- est shading, shown only in southern California, indicates that the census recognized seven pine species in that area. field observations than were currently avail- sus project, given that more than two hundred able. A large region in the center of the Idaho pages of the final report were devoted to the census map was still labelled “unexplored,” material properties of wood derived from each which now offers an evocative reminder of this species, yet mapping the forests also revealed information scarcity. the finite dimensions of a resource that had While the census project was nearing comple- once seemed limitless, potentially setting the tion, Sargent simultaneously chaired an ini- stage for subsequent conservation and preser- tiative to preserve woodlands in New York’s vation movements. Adirondack Mountains from deforestation, which culminated in the establishment of Developing Detail Adirondack Park—the country’s first state for- While the census report provided a useful syn- est preserve—in 1885. It is clear that Sargent thesis of information known at the time, by was aware of the utilitarian value of the cen- 1898, George Bishop Sudworth, a dendrologist 18 Arnoldia 76/3 • February 2019

for the United States Department of Agricul- The explanation for Sudworth’s discontinua- ture’s Division of Forestry, articulated the need tion of the atlas project might be intuited from for a more comprehensive and up-to-date treat- the publication of subsequent bulletins that ment of distribution information. “The army of included maps of select tree species (includ- professional and amateur botanists engaged in ing additional conifers) in the Rocky Moun- botanical research are yearly bringing to light tains. Given that much of Sudworth’s field new facts, which are constantly enlarging our information arrived from the National Forests, understanding of the geographical distribution which were almost entirely located in west- of trees and other plants,” Sudworth wrote in the ern states (at the time), it makes sense that the first edition of his Check List of the Forest Trees maps would ultimately share the same regional of the United States: Their Names and Ranges, emphasis, with special attention given to spe- which was published that year. The checklist cies that were of economic importance. included short descriptions of the ranges for five In 1927, the year of Sudworth’s death, he hundred species, but he knew that much more published a revised checklist of North Ameri- collaborative work was still needed. can tree species, in which he briefly described The 1898 checklist ultimately presaged Sud- the range for every known species at the time worth’s lifelong effort to develop better spe- (adding more than three hundred taxa to his cies distribution maps. Significantly, in 1913, original checklist). Sudworth knew the infor- Sudworth published an atlas for North Amer- mation would prove useful “not only among ican pine species, which was intended to be foresters, woodsmen, and wood users, but also the first volume of a series covering all native in forest schools and other educational institu- trees. These maps represented a significant step tions.” At the time, he and an assistant were towards the familiar appearance of distribution once again working on maps—with many maps today, with each species rendered on a complete but unpublished—but the effort was single map showing the entire range. Sudworth suspended as priorities shifted (perhaps related even showed the distribution of relatively to the Great Depression). sparse species like the whitebark pine, with green marking that followed the narrow eleva- Developing Breadth tional bands along mountain ranges. Given the Edward Norfolk Munns, the chief of the Forest scale, a reader would have difficulty in seeing Service’s Division of Forest Influences, eventu- the range for whitebark pine without the use ally returned to the work that Sudworth and of visual aids such as a magnifying glass, but his assistants had started. In 1938, he published the effort suggests the amount of detailed field an atlas covering 170 of the most important observation that went into the project. tree species, which he noted was “based very Sudworth attributed the success of his maps largely” on Sudworth’s research, with many to work being conducted by the new United updated observations compiled by junior for- States Forest Service, established in 1905, which ester William W. Mitchell. Although the species provided invaluable “unpublished field notes, representation was far greater than anything unrecorded observations, and reports of For- published in Sudworth’s lifetime, critics sug- est Service officials engaged in the exploration, gested that the maps should have been shared surveying, and administration of the 163 with field botanists and foresters for additional National Forests now established.” Sudworth’s corroboration, because to many working on the assistants compiled information from these ground, errors were evident. Even so, the atlas sources, along with state floras and other was reprinted by popular demand. resources, on cards for each species, and these Beyond utility for botanists, foresters, and annotations were plotted on a map of North “the manufacturer in search of raw materials,” America. Sudworth knew that the simplicity Munns also described new ecological and engi- of maps far exceeded the usefulness of even the neering implications for the maps, no doubt most detailed text, yet his volume on pines was based on his early field experience studying the the only portion of the atlas ever published. impact of wildfires on California watersheds. Species Distribution Maps 19 BIODIVERSITY HERITAGE LIBRARY, CONTRIBUTED BY USDA NATIONAL AGRICULTURAL LIBRARY AGRICULTURAL CONTRIBUTED BY USDA NATIONAL LIBRARY, BIODIVERSITY HERITAGE

George Bishop Sudworth’s 1913 atlas included distribution maps for thirty-six species of pines. This map shows the scat- tered high-altitude distribution of whitebark pine (Pinus albicaulis) 20 Arnoldia 76/3 • February 2019 BIODIVERSITY HERITAGE LIBRARY, CONTRIBUTED BY USDA NATIONAL AGRICULTURAL LIBRARY AGRICULTURAL CONTRIBUTED BY USDA NATIONAL LIBRARY, BIODIVERSITY HERITAGE

This detailed rendering of long-leaf pine (Pinus palustris) appeared in the 1938 atlas prepared by Edward Norfolk Munns.

“[Forest distribution] is an essential element began with small generalized ranges for 165 in erosion and flood control operations, and forest species of economic interest, published in land-use planning,” he wrote in the intro- in 1949. He later explained that the small size duction. “Indeed, present trends toward better of the maps was due to practical and logistical planning and integration of land use are direct- reasons, given that it is easier to approximate ing increased attention to forest cover, the an accurate range at a smaller scale. “Botanists, species represented in it, and the possibilities foresters, and other authors bold enough to of enlarging the contribution of forest land to summarize plant distribution records graphi- community welfare.” This, of course, may have cally may expect criticism instead of reward for been a suggestion that worked better on paper their efforts,” he wrote in a follow-up article in than in practice, but the statement represented Rhodora. “It is far easier to detect a minor flaw an important expansion of what distribution along a boundary line than to prepare a better maps could enable. map.” I learned this lesson very quickly in my Ultimately, in 1942, a forest ecologist name own endeavors, to say the least. Elbert Little Jr. was appointed as dendrologist Over the next two decades, Little and his for the Forest Service. Like both Sudworth and assistants worked rigorously to expand the dis- Munns (and myself), Little had spent a consid- tribution data, sifting through more than three erable amount of time at Forest Service field hundred sources, including unpublished card stations in the West, before taking his appoint- files in state herbaria and doctoral dissertations. ment at the national office in Washington. Like Sudworth’s maps, the reference points were Little’s continuation of the mapping project then plotted onto a map of the United States or Species Distribution Maps 21

North America. The first volume appeared in transparencies, the originals could be used with 1971, and the next five volumes appeared over two of the other volumes. If Munns, therefore, the next ten years, ultimately covering more alluded to the possibility of using the distribu- than seven hundred species of trees and major tion maps for something beyond a guide to nat- shrubs. When Little published on the distribu- ural resources, Little’s transparencies indicated tion of trees in Alaska, he retained the indi- a genuine commitment to expanding the types vidual reference points within the distribution of questions that could be raised with the maps. outlines, but otherwise, the maps generally fol- “They provide the basis for correlation stud- lowed the classic form, with a simple outline ies of distribution of a species and the environ- drawn around all contiguous populations. This ment,” Little wrote of the overlays (in the fourth work still represents the standard reference for volume). Moreover, as someone who began his tree species ranges in North America today. career as a forest ecologist, Little saw a greatly The first volume of the atlas also included expanding set of research questions that would nine semi-transparent overlays, nested within benefit from the maps, including “such studies a cover pocket, which could be superimposed as classification, evolution, paleobotany, and over the range maps. The overlays included fea- genetics, and for the distribution of associated tures like “precipitation and rainfall,” “plant animals and plants, especially insects and para- hardiness zones,” and “maximum extent of gla- sitic fungi.” Although the transparencies may ciation in the Wisconsin Glacial Stage.” While seem simple compared to modern approaches, the subsequent volumes did not include these the effort to enable comparisons between tree BIODIVERSITY HERITAGE LIBRARY, CONTRIBUTED BY USDA NATIONAL AGRICULTURAL LIBRARY AGRICULTURAL CONTRIBUTED BY USDA NATIONAL LIBRARY, BIODIVERSITY HERITAGE

For many water-loving species, like the black willow (Salix nigra), Munns rendered the distribution according to rivers and streams. 22 Arnoldia 76/3 • February 2019

species and environmental conditions repre- a distribution outline around scattered dots, sents a milestone development. and the resulting shapes also failed to convey Once published, Little worked vigorously the density of forests. Moreover, the maps no in trying to maintain an authoritative record longer represented the best information about for each individual species, even after retire- the current distributions. Limitations like this ment. A colleague of his related a story of vis- are inherent to the mapmaking process. Even iting an area in Wisconsin in the 1980s where Sudworth, writing in 1913, noted the forests there was a rumor for the occurrence of a spe- were changing faster than the maps could show. cies that wasn’t depicted in the atlas. Little “Extensive and continued lumbering operations brought his field maps, confirmed the sighting, with attending forest fires have so changed, and promptly penciled in the location. Eventu- and in some cases exterminated, parts of the ally, the field maps were brought back to the original stand of most of our pines,” he wrote. office for inclusion in the authoritative maps. “These maps, therefore, indicate only the gen- Little stressed the importance of continual eral occurrence of species with the prescribed maintenance. His coauthor on the second vol- areal limits, and have no reference to the den- ume, Leslie Viereck, continued to maintain sity or continuity of growth.” Munns made the records for Alaska and produced a second edi- same point twenty-five years later, and Little tion, which included range adjustments, some echoed these concerns. species reclassifications, and an expansion to These limitations ultimately fueled my work include significant shrub species. It was unfor- with the Forest Service’s Forest Health Tech- tunate that Viereck passed away in August of nology Enterprise Team, where we needed to 2008, about a year before we started on the finer develop models to predict the risks associated scaled species distributions. with forest pests. We obtained current observa- tions of 346 species that occur at Forest Inven- Modelling the Present tory and Analysis field plots, as well as from After Little retired from the Forest Service in other permanent plots managed by the National 1975, the position of dendrologist was unfor- Forest System and the Bureau of Land Manage- tunately abolished. In the ensuing decades, ment. This amounted to more than 330,000 ecosystem classifications became the mapping plots (and more than 1.2 million subplots). We priority. Communities of trees were identified linked this information to predictive layers as the dominant factors necessary for analyz- pertaining to environmental variables like cli- ing impacts of forest management, and distri- mate, terrain, soils, and satellite imagery. This bution maps for individual tree species were dataset was then used to model individual spe- no longer emphasized. With shifting priorities, cies presence, as well as stand density, which staff changes, and a relocation of the National was necessary for pest risk mapping. In the end, Headquarters, the whereabouts of Little’s we successfully modelled the distribution of authoritative maps was lost through the ages. 264 trees sampled on these Forest Service plots, Although I have encountered people whose ten- and as a by-product of that work, we published ures overlapped with Little’s, it is likely that the National Individual Tree Species Atlas in the data have been forgotten, left in an attic, or 2015. Of course, this printed document will moved to a storage facility at the Department of ultimately become a historical artifact, much Agriculture’s Greenbelt center or to a National like Little’s volumes, given that the forests in Archives and Records Administration facility. If the country will continue to change and trans- these data are recovered in the future, it would form in response to disease and insect pressure, be important to appropriately curate them for climate change, habitat destruction, distur- further refinement and research. bance recovery, and any number of other threats In some disciplines, however, the need for (or boons), many still unforeseen. better species maps became critical. Given The difference between the distributions practical considerations, Little was required shown on Little’s maps and our models is often to take inherent liberties when connecting quite noteworthy, so our published atlas also Species Distribution Maps 23 ARNOLD ARBORETUM ARCHIVES

The first volume of Elbert Little Jr.’s Atlas of United States Trees (1971) included nine overlays that allowed for environmental analysis. In this case, a topographical overlay has been superimposed over the range of whitebark pine (Pinus albicaulis). Also note that the atlas included county borders. 24 Arnoldia 76/3 • February 2019 UNITED STATES FOREST SERVICE, FOREST HEALTH TECHNOLOGY ENTERPRISE TEAM FOREST HEALTH FOREST SERVICE, UNITED STATES

This map of long-leaf pine (Pinus palustris), published in the National Individual Tree Species Atlas, shows a smaller modeled distribution (dark purple) compared to the distribution outlines prepared by Elbert Little Jr. (light purple).

includes Little’s outlines for comparison. It was distribution records. The United States Depart- my hope that this format would draw aware- ment of Agriculture’s Natural Resources Con- ness to the ongoing need for studying these servation Service maintains the PLANTS ranges—work that might require the oversight Database, which has some degree of authority, of a twenty-first-century Little (an authorita- although species distributions are only tracked tive steward of tree species distribution data)— at the county level, at best, which is adequate however, even now, no specific authority is for general applications but not for applications responsible for maintaining comprehensive in need of a finer scale. Species Distribution Maps 25

For many species, like the long-leaf pine, com- data. Other species classification changes were parison between the models and Little’s maps not so easy. The Mexican pinyon pine (P. cem- suggests range contraction. The same is true for broides) was divided into two additional spe- the whitebark pine. Both species are recognized cies, border pinyon (P. discolor) and papershell as endangered, according to the International pinyon (P. remota), but the distributions were Union for Conservation of Nature, although much more difficult to separate due the coinci- for different reasons. The long-leaf pine was dence of the three species. eventually disfavored by the forest industry As the inventory is maintained, newer mod- due to its lengthy sapling (“grass”) stage, and eling techniques can improve the distribu- as a result, commercially managed forests were tion maps for only the species measured on preferentially replanted with loblolly and slash an inventory plot. Other naturally occurring pines (Pinus taeda and P. elliottii, respectively). species—often those with more restricted The species is still threatened with continued ranges in the first place—will need different habitat loss, although substantial restoration data sources and greater effort to be developed. efforts are underway. Whitebark pine is cur- rently most threatened by recent outbreaks of Beyond Borders mountain pine beetle (Dendroctonus pondero- While developing our models, we had the privi- sae), a native insect that has caused widespread lege of working with colleagues in Mexico to mortality among western pine forests. In both develop pest risk maps for Douglas fir Pseu( - cases, the models are critically important for dotsuga menziesii) and several key pines. monitoring current populations, as well as for Though we limited our investigation to eight projecting the future of these populations. species that had coarse climate and soils data, Other species, like the Osage orange (Maclura the permanent inventory for Mexico is designed pomifera), however, show a dramatic range much like the United States, and the poten- expansion. The range shown on Little’s map tial exists to develop a complete set of species is an upright column running through eastern distribution maps for Mexico. (It should be Texas, barely extending into southern Okla- noted that while 387 species were encountered homa and Arkansas. Little wanted to show within inventory plots in the United States, the original range for the species, before it had the Mexico inventory counted over 3,000 tree been widely planted as a living fence between species.) Meanwhile, the resolution of our agricultural fields in the Midwest. Because the information does not carry into Canada, given species readily naturalized, our models, based limited access to the same amount of field on information about actual occurrence at field data. Canada produced distribution maps for plots, shows a much wider range, with popula- approximately ninety-three species, although tions as far afield as western Pennsylvania. Our they are of limited precision compared to the atlas also includes ranges for three nonnative maps in the United States. At present, how- species—tree of heaven (Ailanthus altissima), ever, our own models don’t extend north of the Chinese tallow tree (Triadica sebifera), and border either. In this sense, political relation- empress-tree (Paulownia tomentosa)—which ships are often implicit in distribution maps, have naturalized widely. Since these ranges much as economic and ecological imperatives weren’t recorded in Little’s atlas, this will pro- have manifest themselves throughout this vide invaluable baseline information for future ongoing history. management and research efforts. Given the nature of remote sensing, how- Changes to species classification can also ever, there is increasing potential to combine result in significant changes to the distribu- forest inventories to map complete species dis- tion maps. The bristlecone pine, for instance, tributions, regardless of political boundaries. was separated into two species—Rocky Moun- The North American Forest Commission is tain bristlecone pine (Pinus aristata) and Great currently developing a combined database for Basin bristlecone pine (P. longaeva)—which Mexico, Canada, and the United States, and the were easily separated based upon geographic success of a shared system like this was recently 26 Arnoldia 76/3 • February 2019

demonstrated in Europe. The European Union consistent methods and metrics), the resulting published the first systematic atlas of trees at atlas is testament to the achievements possible the continental scale in 2016, which grew out of with international collaboration. Moreover, an effort to harmonize data within a continent- the Food and Agriculture Organization of the wide forest information system, established United Nations asks all countries to assemble in 2013. Although the authors stressed the a National Forest Inventory every five years, need for even more data (collected using more and although the distribution data are relatively UNITED STATES FOREST SERVICE, FOREST HEALTH TECHNOLOGY ENTERPRISE TEAM FOREST HEALTH FOREST SERVICE, UNITED STATES

This map of Osage orange (Maclura pomifera), published in the National Individual Tree Species Atlas, shows an expanded modeled distribution (dark purple) compared to Little’s distribution outlines (light purple). Species Distribution Maps 27

coarse, efforts like this suggest the potential for could never carry his search and study into all a much more comprehensive set of tree species of nature’s hiding places for even trees alone.” maps, especially in temperate regions where Since the completion of the National Indi- species diversity is less complex. vidual Tree Species Atlas, many changes have Taken together, these aspirations suggest the occurred that would enhance future modeling longevity of Sudworth’s observations in 1898. efforts. Modeled maps now have the poten- “The geographical range of any of our trees tial to be dynamic and adaptive, but they still must necessarily be an expression of the united require the collaborative vision of botanists, efforts of all working botanists,” he wrote, “for foresters, and plant ecologists in the field, now the unaided diligence of one man’s lifetime and for generations to come.

References: Beaudoin, A., Bernier, P. Y., Villemaire, P., Guindon, L., and Guo, X. J. 2017. Species composition, forest properties and land cover types across Canada’s forests at 250m resolution for 2001 and 2011. Quebec: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre. Ellenwood, J. R., Krist F. J., and Romero, S. A. 2015. National individual tree species atlas. Washington, DC: United States Forest Service, Forest Health Technology Enterprise Team. Little, E. L. 1949. Important forest trees of the United States. In Trees: The yearbook of agriculture. Washington, DC: United States Department of Agriculture. Little, E. L. 1951. Mapping ranges of the trees of the United States. Rhodora, 53: 195–203. Little, E. L. 1971. Atlas of United States trees: Conifers and important hardwoods (Vol. 1). Washington, DC: United States Department of Agriculture Forest Service. Little, E. L. 1976. Atlas of United States trees: Minor western hardwoods (Vol. 3). Washington, DC: United States Department of Agriculture Forest Service. Little, E. L. 1977. Atlas of United States trees: Minor eastern hardwoods (Vol. 4). Washington, DC: United States Department of Agriculture Forest Service. Little, E. L. 1978. Atlas of United States trees: Florida (Vol. 5). Washington, DC: United States Department of Agriculture Forest Service. Little, E. L. 1981. Atlas of United States trees: Supplement (Vol. 6). Washington, DC: United States Department of Agriculture Forest Service. Munns, E. N. 1938. The distribution of important forest trees of the United States. Washington, DC: United States Department of Agriculture Forest Service. De Rigo, D., Caudullo, G., Houston Durrant, T., and San-Miguel-Ayanz, J. 2016. The European atlas of forest tree Species: Modeling, data and information on forest tree species. In: San-Miguel-Ayanz, J., De Rigo, D., Caudullo, G., Houston Durrant, T., and Mauri, A. (Eds.), European atlas of forest tree species. Luxembourg: Publishing Office of the European Union. Sargent, C. S. 1884. Report on the forests of North America (exclusive of Mexico). Washington, DC: Department of the Interior Census Office. Sudworth, G. B. 1898. Check list of the forest trees of the United States: Their names and ranges. Bulletin of the United States Department of Agriculture, Division of Forestry, 17: 1–144. Sudworth, G. B. 1913. Forest atlas: Geographic distribution of North American trees. Part 1: Pines. Washington, DC: United States Department of Agriculture Forest Service. Sudworth, G. B. 1927. Check list of the forest trees of the United States: Their names and ranges. United States Department of Agriculture Miscellaneous Circular, 92: 1–297. Viereck, L. A., and Little, E. L. 1975. Atlas of United States trees: Alaska (Vol. 2). Washington, DC: United States Department of Agriculture Forest Service. Viereck, L. A., and Little, E. L. 2007. Alaska trees and shrubs (2nd ed.). Fairbanks, AK: University of Alaska Press.

James Ellenwood is the National Program Lead for Monitoring, Remote Sensing, and Geospatial Analysis Research at the United States Forest Service. WILSON, E. H. 2019. TAIWAN DISPATCHES. ARNOLDIA, 76(3): 28–33

Taiwan Dispatches

Ernest Henry Wilson

In March of 1919—one hundred years ago—Ernest Henry Wilson returned from his sixth and final plant collecting expedition to eastern Asia. The trip had begun in Yokohama, Japan, in January of 1917, and he traveled widely, tracing his way from Okinawa to Korea, even touching briefly into China. In early 1918, he sailed for Taiwan, where he was enamored with the subtropical conifers. According to his own tally, he collected more than seven thousand herbarium specimens, and he would return for seed in the fall. Taiwan, then known as Formosa, had been occupied by Japanese troops for more than two decades. Wilson’s travels were conducted with a Japanese botanist named Ryozo Kanehira, and initial collecting locations were recommended by Bunzo Hayata, a botanist at the Imperial University of Tokyo. The following excerpts come from Wilson’s handwritten letters to Charles Sprague Sargent, the director of the Arnold Arboretum. Italics have been added.

JANUARY 17, 1918 | YOKOHAMA, JAPAN of more material of Formosan conifers. I intend My arrangements are all completed for the now to make up for lost time & our Herbarium trip to Formosa & I leave here in the morning. shall possess its compliment of Formosan coni- I plan to stay in Formosa for about ten weeks fers ere I am through. if the money in hand be enough to enable me FEBRUARY 16, 1918 | TAIPEH, FORMOSA to do so. I am back from the trip to Arisan & have but JANUARY 25, 1918 | TAIPEH, FORMOSA one regret which is that you too were not pres- Just a note to let you know that I have reached ent to enjoy the forests & the giant trees. I had Formosa & that everything is favorable to a expected much but what I saw far exceeded my successful visit. I arrived here on the 22nd expectations: the forests are easily the finest & leave tomorrow (26th) for Arisan where & the trees the largest I have ever seen.… The the giant trees are.… The officials, one & all, country is very steep & savage & travelling over promise every assistance & there is no doubt it is hard work. Thanks to a light railway & but that they mean it. A Mr. Kanehira, who courtesies extended by the government things speaks English & is one of the heads of the were made as easy for me as they possibly could forestry department, has been detailed to be made. The weather on the whole was good accompany me to Arisan & will probably go though two consecutive days of rain & sleet elsewhere with me also. He is a very nice fel- & many foggy afternoons were a hinderance. I low & I fancy will make a genial companion.… collected over twelve hundred specimens, rep- It is now eleven years since I begged some resenting about two hundred species, & took scraps of Taiwania [a monotypic member of six and one-half-dozen photographs … The the cypress family (Cupressaceae)] from Hayata Chamaecyparis formosensis [an endemic false & got promises, which were never fulfilled, cypress] is the largest tree being sometimes Wilson’s Letters 29 ALL IMAGES FROM ARNOLD ARBORETUM ARCHIVES

Wilson was awed by the enormous conifers near Mount Arisan. On February 1, 1918, he photographed Taiwania cryptomerioides (at right), towering beside Taiwan cypress (Chamaecyparis formosensis, at left). 30 Arnoldia 76/3 • February 2019

The botanist Ryozo Kanehira accompanied Wilson in Taiwan. On January 31, 1918, Wilson photographed Kanehira near Mount Arisan, standing beside the trunk of Taiwania cryptomerioides, which soared to a height of 150 feet (46 meters). Wilson’s Letters 31

Clockwise from upper left: Lithocarpus amygdalifolius on February 1, 1918; Taiwan Douglas-fir Pseudotsuga( sinensis var. wilsoniana) on April 6; Taiwan cypress (Chamaecyparis formosensis) with a trunk diameter of 20 feet (6 meters), photographed on the return trip, October 31; and Calocedrus formosana on April 1. 32 Arnoldia 76/3 • February 2019

Wilson photographed pure stands of Taiwan fir Abies( kawakamii) on Mount Kiraishu, Nantou County, on March 6, 1918.

nearly 200 ft. tall & 65 ft. in girth of trunk.… sugar, rice, & other crops. However, I made a I was informed that the oldest tree which had fair collection of plants & took a dozen pho- been felled showed about two thousand seven tographs so we shall have a record of what the hundred annual rings, & a larger one standing flora is like. is estimated at three thousand years. The trunks are mostly hollow but the wood, which is MARCH 16, 1918 | TAIPEH, FORMOSA reddish, fragrant, & has a beautiful satiny lus- The trip to the central range of Formosa has ter, is much esteemed by Japanese for interior proved a complete success. The weather was work in houses. fine throughout & the journey fairly easy. From the railway we travelled for two days on push FEBRUARY 28, 1918 | TAIPEH, FORMOSA trolley & then climbed for three days, sleep- I returned from the trip to the south on the ing in police huts at night.… The peak we night of February 26th. The flora of the coastal ascended is named Mt. Kiraishu, is 11,002 ft. region did not prove at all interesting, indeed, high, well-forested on the upper-middle slopes. most of it had been destroyed to make way for The climate is drier & the flora different from Wilson’s Letters 33

that of the Arisan region. Abies kawakamii [an of the fourth day we found our tree but all our endemic fir] was the particular quest of the trip efforts to find more failed. Dense fog came on & we found it in great plenty above 9,500 ft. & photography was out of question. The tree After collecting from the ground scales & spikes was a large one, fully 90 ft. tall & 12 ft. in girth of disintegrated cones, I was fortunate enough of trunk which divided into three stems.… to find four or five perfect cones & so complete We then descended some five miles to our the specimens. With this acquisition our her- lodgings—a police hut—hoping that the next barium possesses ample & complete material morning would be clear so that we might return of every known species of Abies found in the & photograph the tree. It rained during the night Far East.… Altogether the trip yielded about but morning broke gloriously fine & we got two hundred species bringing the total to date back to the tree by 9 a.m. It stood badly for pho- collected in Formosa to about four hundred & tography & we were nearly three hours cutting seventy species. It was difficult country to pho- (or rather hacking for our tools were poor) away tograph in but I secured two & one half dozen, surrounding trees before a satisfactory picture which will give a fair idea of the vegetation. could be taken. However, fortune favored us but scarcely had we finished when down came APRIL 11, 1918 | TAIPEH, FORMOSA the mists blotting out everything. The task I am writing this at the completion of the allot- accomplished we packed up & returned by the ted task in Formosa. One objective I had in way we came. mind on visiting the island was to see if pos- APRIL 14, 1918 | TAIPEH, FORMOSA sible every conifer known to grow there. Dr. Hayata in Tokyo assured me this was impos- Formosa is a land wherein it is quite impossible sible but the local authorities took a more to travel off the beaten track without official favorable view & thanks to their good services sanction & assistance. To us everything has complete success has crowned our efforts. I been open & every wish, expressed or implied, have seen, photographed, & collected ample viewed favorably. The director of the forestry material of every species & variety of conifer experimental station, Mr. R. Kanehira, is a known from Formosa. But it must be con- very exceptional man full of energy, enthusi- fessed that some of these Formosan conifers asm & good will, & associated with him are have exacted severe toll in time, money & at least two very competent collectors. Kane- energy & at the moment of writing I am leg hira arranged all our trips & accompanied us weary & tired.… When last I wrote I mentioned on most of them. We got to know (he speaks that my next trip had for its principal object English perfectly) one another pretty well & I Cunninghamia konishii [another member of hope to our mutual advantage. In fact, whilst the cypress family]. Bad weather hampered the tangible results of our trip are considerable things but I got him & photographs also. I no less important in my opinion is the rela- then switched off to another district & got tionship I have established between the Arnold the Libocedrus [an endemic incense cedar, now Arboretum & Kanehira & his associates.… recognized as Calocedrus formosana] which Formosa is certainly a rich & beautiful island & now is found only on steep ridges & cliffs its forest wealth is very great. To have visited almost inaccessible. So difficult is the country the island is a privilege I greatly appreciate & I that it was not possible to obtain photographs shall carry away with me none but the pleasan- of the whole tree but only sections.… test of recollections. I was back here on April 4th & left the With cordial regards & best wishes, next morning to collect the last remaining I am, dear Professor Sargent, species—the Formosan Pseudotsuga [an Faithfully & sincerely yours, endemic Douglas fir, now recognized as P. sinensis var. wilsoniana].… On the morning E. H. Wilson DAMERY, J. 2019. HURRIED JOURNEY: BOTANY BY RAIL. ARNOLDIA, 76(3): 34–39

Hurried Journey: Botany by Rail

Jonathan Damery

f a pin were dropped in the center of a topo- To Sargent, railroad transportation would graphic map of Nevada, it would land amidst have seemed ordinary. After all, his father, a Ia series of low mountain ranges, running banking president named Ignatius Sargent, had roughly north and south. The ranges ripple been on the board of directors for several New towards the eastern border of the state, form- England railroad companies since 1849, and in ing an arrangement that looks like a furrowed 1880, Charles would assume his father’s mem- brow. In 1878, Charles Sprague Sargent, the first bership on one of these boards—the Boston and director of the Arnold Arboretum, embarked Albany Railroad—and would continue in that for these arid mountains in what would be the capacity through 1900. Railroads were in the first non-local plant collecting expedition by family. Yet when Sargent headed for Nevada, an Arboretum staff member. Sargent found for- the Pacific Railroad was less than a decade old, ests within this area that appeared “scanty and and the railroad was just beginning to redefine stunted.” He counted only seven tree species, of botanical possibilities in the western United which the single-leaf pinyon (Pinus monophyla) States. Sargent, himself, described his expedi- and Utah juniper (Juniperus osteosperma, then tion as a “hurried journey,” suggesting how considered J. californica var. utahensis) were remote landscapes had been rendered newly the most abundant. Despite the limited diver- accessible. Unlike botanical explorations that sity, Sargent was impressed with the trees for occurred in Nevada before the ceremonial their resilience and age. Some, he estimated, golden spike was driven on May 10, 1869—the were eight hundred years old, if not older. date when transcontinental rail passage was Sargent began this botanical reconnaissance inaugurated—Sargent’s field research could be near the town of Eureka, a silver-mining com- conducted in the matter of two weeks (rather munity located roughly in the center of the than months or years), with the subsequent state. In 1869, the town consisted of one or two research publication written in the comfort of cabins, but by the time Sargent arrived, nine Boston and Brookline. years later, it had grown into the second largest town in the state, with a population, according By Horse and by Foot to boosters, that neared seven thousand. The In 1955, Susan Delano McKelvey, an Arbore- town boasted a new brick hotel, an opera house tum botanist, published an eleven-hundred- that could seat five hundred, two banks, four page tome on early botany of the western churches, three newspapers, and, most impor- United States, titled Botanical Exploration tantly, sixteen furnaces for smelting silver ore. of the Trans-Mississippi West: 1790–1850. All of this—along with Sargent’s arrival—was According to McKelvey, an Englishman named facilitated with a narrow-gauge railroad, com- Joseph Burke was one of the first scientifically pleted in 1875, which connected Eureka with trained botanist to make observations in central the town of Palisade, about eighty-five miles Nevada. Burke spent thirty-eight months in the to the north. Those tracks, in turn, were made western United States, beginning in the spring practical by the Pacific Railroad, completed in of 1844, and he crossed Nevada in the sum- 1869, which carved its way through Palisade. mer of 1846. His account of the Nevada land- The Pacific Railroad—composed of the Central scape provides scant details, however, because Pacific to the west and the Union Pacific to the when that portion of the expedition ended at east—was the first railroad to span the Rocky Fort Walla Walla, in southern Washington, Mountains and the Great Plains, connecting he received two overdue letters from William San Francisco with Omaha and cities beyond. Jackson Hooker, the director of the Royal Botany by Rail 35 ARNOLD ARBORETUM ARCHIVES

A map from Susan Delano McKelvey’s Botanical Exploration of the Trans-Mississippi West: 1790–1850 shows the basin-and-range topography of central Nevada. The botanist Joseph Burke (Bu) passed through Nevada in 1846, partially sharing a route used by John Charles Frémont (F3) in 1845.

Botanic Gardens, Kew, who was the primary realistic, and without the guarantee of money sponsor for the trip. The second letter informed and supplies in the meantime, his explorations Burke that his funding had been halted due to could not continue. He returned home. Hooker’s dissatisfaction with the amount of McKelvey, for her part, felt that Hooker was collections Burke had provided. Burke defended unfair to Burke, noting the physical rigor asso- his record in a long response letter, noting sev- ciated with backcountry botanical expeditions, eral shipments of seed—the most recent of where botanists were responsible for travelling which had been sent “across the mountains with packages of seeds and herbarium speci- by the express” and herbarium specimens that mens—not to mention food and supplies—for had been sent for a ship in Vancouver. Burke weeks if not months on end. “To work one’s then resigned from the expedition. “I think, Sir way thus encumbered through a pathless wil- William, it is a very hard case if a collector is derness of swamps, undergrowth or fallen tim- sent from the Royal Botanic Gardens to a coun- ber, up and down ravines, across creeks and try where he cannot send his collections by any rivers, in fair weather or in, veritably, foul or to means by the time mentioned in your letters,” traverse for days on end waterless deserts in hor- he wrote. “I trust, Sir William, you will forgive rible heat and permeating dust, was exhausting my retiring from the service without waiting work, and the collector was not chosen because an answer, as it would be two years or upwards he was qualified as a Paul Bunyan,” McKelvey before I could receive one.” It would, in fact, writes. She goes on to narrate the evening take fourteen months for his letter to arrive routine botanists were generally obligated to on Hooker’s desk. So, Burke’s estimate was undertake: stopping for camp, building a fire to 36 Arnoldia 76/3 • February 2019

prepare food and stay warm (even in the desert), lead botanist on two of six field seasons by a and then arranging the daily collections of plant geological team surveying the fortieth paral- clippings between layers of paper and pressing lel between California and the Great Plains. them tight. Often, too, given that the papers Watson’s first season focused primarily on used for herbarium specimens were prone to central Nevada, the second on Utah—almost become damp or wet throughout the course entirely within the self-contained watershed of of a trip, the botanist would need to regularly the Great Basin. The region was of interest for redo older specimens, transferring them to drier the survey (which had begun in 1867) because papers, in order to prevent mildew. Plant collect- no accurate maps existed and because the fed- ing was (and still is) physically demanding. eral government was intent on cataloguing the These routines would have certainly applied natural resources along the projected path of to Burke, although it is unclear how many the Pacific Railroad. botanical collections Burke made in Nevada. Watson began at Carson City, Nevada, in He travelled across the state with a group of set- April 1868, moving east on an indirect path. tlers that were following a newly blazed trail for The purpose of the survey was thoroughness Oregon’s Willamette Valley. The team consisted rather than speed, and the team spent a full six of twenty-four individuals and several wagons, weeks working from a basecamp at Fort Ruby, and it took nearly seven weeks for them to pass about seventy miles northeast of the prospect- between Fort Hall, on the Oregon Trail, and the ing encampment at Eureka (of which Watson Willamette. Burke wrote little about Nevada, makes no mention). From Fort Ruby, explora- but he noted that when the team passed through tions were made in the surrounding mountain the northwestern corner of the state, a land- ranges and valleys. Watson observed several scape now known as the Black Rock Desert, it locations where relatively sizeable conifers was the “most miserable volcanic region, with could be found, including limber pine (Pinus many boiling springs.” He recorded nothing flexilis), growing in the East Humboldt Moun- of botanical interest until spotting an expanse tains, with individuals sometimes (though of California poppy (Eschscholzia californica), rarely) reaching fifty feet high. which decorated a recently burned river valley Although Watson documented his find- with papery orange flowers, in southwestern ings in incredible detail, he wrote little about Oregon. The poppy was “a very shy fruiter,” he the comforts or difficulties of travelling with wrote, as was the golden chinquapin (Castanop- the survey team, and he said nothing sis chrysophylla) that he encountered several about the logistics of offloading herbarium days later. When they arrived at the Willamette specimens for shipment. Nevertheless, had his farmstead where the leader of the wagon train months in Nevada occurred even one year later, lived, the whole team heaved with exhaustion, the realities of the railroad would have begun horses and humans alike. Burke rested three to reshape these considerations. By 1868, rail- days and then continued to Oregon City—south road workers had already begun to lay tracks of Portland. His horses “nearly drowned” while across Nevada, and in 1869, these tracks were swimming a creek on the way (presumably operational. Therefore, Watson’s study marked soaking any herbarium specimens that he had an important moment: not only had it resulted collected), and it would take him another two in the most detailed account of the flora of weeks to reach Fort Walla Walla, where his res- central Nevada published to date but it also ignation letter was ultimately penned. represented the final botanical study in the Over the three decades that separated Burke region before the landscape was bound into the from Sargent, other botanists passed through national infrastructure of steel tracks and steam northern and central Nevada, and the most locomotion. Geologists on the survey would detailed observations were rendered by Sereno subsequently comment about strata and fossils Watson, who would later become the curator observed at railroad cuts, indicating how the of the Gray Herbarium and Library at Harvard. presence of the railroad became ingrained in Watson embarked, in 1868 and 1869, as the the researchers’ world. Botany by Rail 37

Botanical Space travelling from the Atlantic Coast to the Pacific Given that Watson and Sargent would become Coast of the United States and back was a radi- Harvard colleagues, the men must have con- cal convenience. Instead of sending an explorer ferred about the flora and landscape of central with youthful enthusiasm and resilience— Nevada while Sargent was making travel prepa- someone like Burke—Hooker himself could go, ration in 1878. Yet Sargent also saw his trip even as a sixty-year-old and even as the director as a follow-up to an expedition the previous of a major botanical institution. summer by Asa Gray—the preeminent Har- For Gray, this was a second trip on the Pacific vard botanist—and Joseph Dalton Hooker, the Railroad; the first was in 1872. Gray’s wife, Jane English botanist who had assumed his father’s Loring Gray, accompanied him on both trips, role as director of the Royal Botanic Gardens, and she would later recall him racing into the Kew. When Sargent returned from his trip, he landscape at short station stops, collecting sent Hooker a letter recounting his findings in whatever he could find. This caused consider- detail, noting that he expected Hooker would able intrigue for fellow passengers, who then remember the Palisade station on the railroad. gathered around to watch Gray prepare his her- Sargent continued south to Eureka, whereas barium specimens. Eventually others began to Hooker and Gray continued riding the Pacific collect plants as well, bringing them to Gray for Railroad to Carson City. Yet the implications of identification and causing exasperation for the Hooker’s presence in this region is significant, conductor. It took them a day to cross Nevada, given that thirty-one years before, Joseph Burke where Gray noted the snaking green vegetation was passing through this exact same stretch— along the Humboldt River. In a letter to his then remote and without a defined wagon friend Richard William Church, Gray described route—under the direction of Hooker’s father. the whole experience with exceptional enthu- The son, acting in the same official capacity as siasm. “There were fatigues and small discom- director of Kew, was making a passage that his forts, of course, but these are all forgotten long father had commissioned another to make. ago, and the whole transit dwells in memory McKelvey stresses the power dynamics that as one continual and delightful piece of pleas- were often at play between collectors and the ant, novel, ever-varied, and instructive sight- individuals who sponsored their trips. She seeing,” he wrote. “Of course, the identifying notes that few of the botanists considered in at sight, as we flew by, of flowers new to me her book—individuals working in the western in the living state, and the snatching at halts, United States before 1850—were engaging in and the physical features of districts which I their own independent research. “By far the had always been interested in, and knew much greater number went at the behest of profes- about but had never seen, all gave me occupa- sional botanists living in proximity to the essen- tion and continual pleasure.” tials of herbaria and libraries, and in distinction In this way, the Pacific Railroad was begin- to their emissaries, amid safe and comfortable ning to reshape botanical space in the west- surroundings,” McKelvey writes. “The backers ern United States. By the time the Grays made of the scheme—often called ‘closet botanists’ their rail passage in 1872, five hundred miles for the reason that, working in offices, they may through the Great Basin no longer meant the never have seen the living plants which they same thing that it had with Watson’s expedi- described—were engaged for the most part in tion a mere four years before, let alone more descriptive botany, writing botanical papers or than two decades before with Burke. While compiling floras of small or large scope.” While botanical explorations in the region could still Joseph Hooker began his early career with an be physical and immersive, the work was con- expedition to Antarctica (and the surrounding ducted with two steel lifelines to urban centers. islands) and then another to India, those two Herbarium specimens no longer needed to be expeditions collectively required more than transported for weeks or months before reach- seven years abroad. The fact, therefore, that ing a shipping location. While Sargent and other Hooker could now spend scarcely three months leading botanists would continue to enlist field 38 Arnoldia 76/3 • February 2019

collectors to work in the western United States, that would be benefit from this reconfigura- the power and money associated with collect- tion of space along the railroads. The power to ing along these railroad axes had been forever study these landscapes came with the simul- transformed. taneous power to exploit the resources found therein. Both processes could be conducted at Botanical Limits an unprecedented rate. Certainly, the Pacific Railroad did not uniformly In 1878, after Sargent arrived in Eureka, he influence botanical space in the western United obtained a wagon and continued southwest for States, and in summer of 1883, Sargent would about seventy-five miles, exploring the Monitor participate in a geological survey associated Range, which reaches points well over ten thou- with the installation of the Northern Pacific sand feet above sea level. He then continued Railroad that connected Tacoma, Washington, to Carson City, from which he proceeded into with St. Paul, Minnesota. Although he was California. During his two weeks in Nevada, he gone less than two months, that expedition was collected a considerable amount of seed, which rife with peril, including two instances where he planned to introduce into garden cultivation. pack animals slipped and fell precipitously. Meanwhile, he became increasingly attuned to (In the second case, the horse fell fifteen hun- the risks facing these unassuming and hard- dred feet, carrying Sargent’s plant collections scrabble forests. Wood of the Utah juniper and the team’s guns.) Yet Sargent, like others, (Juniperus osteosperma) was widely harvested quickly understood that it wasn’t just botanists for cheap fuel, given that it was the only tree COURTESY OF THE ARCHIVES OF THE GRAY HERBARIUM OF THE ARCHIVES GRAY COURTESY

Harvard botanist Asa Gray rests at La Veta Pass, Colorado, holding an herbarium press (foreground), with Kew’s Joseph Hooker at his side (seated at left). Jane Loring Gray wears a light-colored coat at the table behind. This 1877 expedition continued to California using the Pacific Railroad. Botany by Rail 39

found abundantly at lower elevations. (Its wood proposed that the federal government should even powered the steam locomotive on the step in to preserve the remaining woodlands, Eureka and Palisade Railroad.) Other tree spe- warning that “terrible destruction” would cies were harvested for lumber, charcoal, and occur otherwise. (About three decades later, the even bearings for machinery. Humbolt-Toiyabe National Forest was estab- Most striking, however, were his observa- lished, protecting vast swaths of these non- tions of the Great Basin bristlecone pine (Pinus contiguous mountain forests.) In this sense, longaeva, then considered P. balfouriana). He Sargent’s railroad-powered expedition allowed found several specimens, growing between him to articulate the finite limits of botanical fifteen and thirty feet tall, on a mountain near space. Forests that were once remote and prac- Eureka. “Formerly the whole summit of this tically inaccessible for a Bostonian like Sargent mountain was very generally covered with this were now mere days away, and their future, as species,” he wrote, “but with few exceptions a result, seemed ever more precarious. the trees have all been cut to supply the mines with timbering, for which purpose the strong References and very close-grained, tough wood of this spe- Ambrose, S. E. 2001. Nothing like it in the world: The cies is preferred to that of any other Nevada men who built the transcontinental railroad, tree.” Sargent didn’t estimate the age of these 1863–1869. New York: Touchstone. trees or count the tightly packed growth rings, Burke, J. 1846. Burke to W. J. Hooker, 17 October 1878. but in California, this species is now known to Director’s correspondence, Library and Archives reach more than five thousand years old. On at Royal Botanic Garden, Kew. the same mountain, Sargent observed a curl-leaf Gray, J. L. (Ed.). 1894. Letters of Asa Gray (Vol 2.). Boston mountain mahogany (Cercocarpus ledifolius)— and New York: Houghton, Mifflin, and Co. a small tree in the rose family (Rosaceae)—and Lambert Molinelli and Co. 1879. Eureka and its resources: he suggested that plant was least 890 years old, A complete history of Eureka County, Nevada. if not much older. “It is perhaps permissible to San Francisco: H. Keller and Co. suppose that the seed which produced this little McKelvey, S. D. 1955. Botanical Exploration of the Trans- tree had already germinated when the oldest Mississippi West: 1790–1850. Jamaica Plain, MA: Arnold Arboretum of Harvard University. living Sequoia on the continent was still a vig- orous sapling with its bi-centennial anniversary Sargent, C. S. 1877. Sargent to J. Hooker, 21 October still before it,” Sargent wrote. 1878. Director’s correspondence, Library and Archives at Royal Botanic Garden, Kew. Sargent suspected that someone travelling across the Great Basin on the Pacific Railroad Sargent, C. S. 1879. The forests of central Nevada, with some remarks on those of the adjacent regions. would perceive a landscape that was essen- The American Journal of Science and Arts, 3: tially “destitute of trees,” much like the prai- 417–426. ries to the east. Yet he came to recognize the Sutton, S. B. 1870. Charles Sprague Sargent and the “immense value” of the forests, no matter how Arnold Arboretum. Cambridge, MA: Harvard diminutive. “It will have been seen that the University Press. forests of Nevada, consisting of a few species Watson, S. 1871. Botany. In C. King (Ed.) Report of adapted to struggle with adverse conditions of the geological exploration of the fortieth soil and climate, are of immense age, and that parallel (Vol. 5). Washington, DC: Government the dwarfed and scattered individuals which Printing Office. compose them reach maturity only after cen- White, R. 2011. Railroaded: The transcontinentals and turies of exceedingly slow growth,” he wrote. the making of modern America. New York: “On this account, and because, if once W. W. Norton and Co. destroyed, the want of moisture will forever Williams, R. L. 2003. A region of astonishing beauty: The prevent their restoration, either naturally or botanical exploration of the Rocky Mountains. by the hand of man, public attention should be Lanham, MD: Robert Rinehart Publishers. turned to the importance of preserving, before it is too late, some portions of these forests.” He Jonathan Damery is the associate editor of Arnoldia. RUBINSTEIN, J. 2019. SAX PINE: A HYBRID LEFT BEHIND. ARNOLDIA, 76(3): 40

Sax Pine: A Hybrid Left Behind

Jared Rubinstein

ast fall, gray fog streamed down the hill- himekomatsu, the southern variety of the Japa- side by the Hunnewell Building, envel- nese white pine. The combination shows just Loping the magnolias and eastern white how well hybridization can capture traits from pines (Pinus strobus) that dominate the area. each parent. The needles, in fascicles of five, The display emanated from an art installation, maintain the long, soft appearance of P. mon- Fog x FLO, by Fujiko Nakaya, and when view- ticola but gain a glaucous, blueish-gray color ing the fog from atop the hill, as signs encour- from P. parviflora. The hybrids seem to get their aged visitors to do, a few pines stuck out from height from P. monticola, especially accession the others. With bluish needles and scaly bark, 266-46*B, which soars to almost 75 feet (23 these trees didn’t look quite like their neigh- meters), already much higher than even the old- bors, nor did they look quite like any other est Japanese white pines at the Arboretum. And species of pine. the bark, normally thin and smooth on P. parvi- That’s because these trees (accession 266-46) floraand rough and flaky on P. monticola, forms are hybrids. Although the Arnold Arboretum is elegant plates that are divided into scales—a best known for its wild-collected plants, most sort of middle ground between the two parents. identified to a single species, we also have a When evaluating hybrids, one usually looks significant collection of hybrid plants, includ- for hybrid vigor, or traits that give a hybrid an ing many that were bred and developed here. advantage over its parents, like a better form or a Karl Sax, a professor of botany at the Bussey higher tolerance to adverse environmental con- Institute and later director of the Arboretum, ditions. While these particular hybrids do appear created some of the Arboretum’s best-known to be vigorous growers and have an unusual mix hybrids, including Forsythia ‘Meadowlark’ and of features, they never managed to achieve the Magnolia × loebneri ‘Merrill’, which both can be fame found by some of Sax’s other hybrids, like found growing in the Arboretum and around the Prunus ‘Hally Jolivette’ or Malus ‘Mary Potter’. world. But Sax didn’t only work with flowering The beauty of these hybrid pines is perhaps a trees or shrubs—he also dabbled with conifers. more subtle one, and they just weren’t flashy In the early 1940s, Karl Sax went on a bit of enough to make it big in the horticultural indus- a pine hybridization kick. Crossing different try of the 1940s. Unlike other pine hybrids Sax plant species can be tedious: Pines are wind tried out, such as Pinus × hunnewellii or Pinus pollinated, so Sax covered the female cones of × schwerinii, these hybrids were never given one pine species with a bag to prevent natural a nothospecies designation—that is, a Latin pollination from pollen blowing around in the name specific to that hybrid. What’s more, these wind. When the time was right, he removed the hybrids do not appear in horticultural catalogs bags and introduced pollen collected from male or seem common in other arboreta. cones of a different pine species to the female Far from diminishing their value, however, cones. Once the hybrid seeds had developed this lack of fame makes these hybrids all the within the cone, Sax removed and planted the more special to the Arboretum. It’s possible seeds in the nursery at the Bussey Institute. that the five plants growing here are the sole Sax mixed and matched pines from all over the representatives of this hybrid in cultivation. world—New England pines with Himalayan More than anything, these hybrids highlight the pines, European pines with Japanese pines, importance of experimentation and of following West Coast pines with East Coast pines—all curiosity to wherever it may lead. Their longev- with an eye towards producing something new ity and beauty remind us that even hybrids that with a high economic or ornamental value. don’t “make it” deserve another look. The hybrid pines behind the Hunnewell Building are crosses between Pinus monticola, Jared Rubinstein is the living collections fellow at the the western white pine, and P. parvifloravar. Arnold Arboretum.