Biodiversity Commons^™

Water As A Trophic Currency In Dryland Food Webs, Daniel C. Allen, Kevin E. Mccluney, Stephen R. Elser, John L. Sabo

Biological Sciences Faculty Publications

Water is essential for life on Earth, yet little is known about how water acts as a trophic currency, a unit of value in determining species interactions in terrestrial food webs. We tested the relative importance of groundwater and surface water in riparian food webs by manipulating their availability in dryland floodplains. Primary consumers (crickets) increased in abundance in response to added surface water and groundwater (contained in moist leaves), and predators (spiders and lizards) increased in abundance in response to added surface water, in spite of the presence of a river, an abundant water source. Moreover, the relative magnitude …

Predicting Invasion Risk Of Non-Native Plants Using A Modified I-Rank Assessment, Justin B. Williams

School of Natural Resources: Dissertations, Theses, and Student Research

Biological invasions are a global problem responsible for native species declines worldwide. Understanding the invasion risk from non-native species is important in establishing management goals and making decisions for managing native ecosystems. Useful modeling methods for quantifying or predicting invasion risk should consider research needs, data availability, and operate at an appropriate scale. I evaluated risk assessment methods towards answering a specific research question; which plant species pose the greatest risk of becoming invasive or having the greatest negative impact in Nebraska? I selected the I-Rank assessment method, which consists of 20 questions grouped into four risk categories or Subranks: …

Evaluation Of Three Nest Searching Methods For Ring-Necked Pheasant, Jeffery W. Stackhouse, Kevin K. Sedivec, Benjamin A. Geaumont

The Prairie Naturalist

Ring-necked pheasant (Phasianus colchicus) are a highly sought after game bird and as such, much research has been conducted regarding their ecology (Warner 1981, Trautman 1982, Johnson and Knue 1989). Perhaps the most investigated aspect of pheasant ecology is the species’ reproductive season (e.g. Linder et al. 1960, Dumke and Pils 1979, Leif 1994) with many studies focusing on nesting habitat (Baskett 1947, Clark et al. 1999). Results from previous research have acknowledged the difficulty associated with locating pheasant nests in their preferred cover types (Hanson 1970, Evrard 2000). Studies of pheasant nesting ecology have been based on …

Dual Capture Of A Piñon Deer Mouse And A Silky Pocket Mouse Resulting In Consumption Of The Smaller Animal, Jon C. Pigage, Roger D. Peyton

The Prairie Naturalist

Intraspecific dual captures of rodents are uncommon, but not rare. There are several reports of brown rats (Rattus norvegicus), white-footed deer mice (Peromyscus leucopus), North American deer mice (P. maniculatus), western harvest mice (Reithrodontomys megalotis) and meadow voles (Microtus pennsylvanicus) caught simultaneously in the same trap (i.e. a door-closing live-trap; Davis 1955, Getz 1961, Blaustein and Rothstein 1978, Jenkins and Llewellyn 1981, Novak 1983). Some reports are incidental whereas others are interpreted as social associations or bonding between conspecifics. Interspecific dual captures are rarely reported in the literature. The earliest report of …

Red-Tailed Hawk Nesting In Kansas: Influence Of Landscape Characteristics, William Langley

The Prairie Naturalist

Factors that affect nest site selection in red-tailed hawks (Buteo jamaicensis) include the physical features surrounding the nest and landscape characteristics. Features surrounding nests include: tree height, tree diameter (dbh), percent canopy cover, slope, nest openness, and density of woody plants or shrubs (Titus and Mosher 1981, Bechard et al. 1990, Tietje et al. 1997, Actkinson et al. 2007). Landscape characteristics that influence nest-site selection by red-tailed hawks vary across regions. In Georgia, red-tailed hawks selected nest site in areas with greater area of agriculture and open pasture (Moorman and Chapman 1996), whereas in Oklahoma prairies, the hawks …

Associations Between Iron Concentration And Productivity In Montane Streams Of The Black Hills, South Dakota, Cari-Ann Hayer, Benjamin M. Holocmb, Steven R. Chipps

The Prairie Naturalist

Iron is an important micronutrient found in aquatic systems that can influence nutrient availability (e.g. phosphorus) and primary productivity. In streams, high iron concentrations often are associated with low pH as a result of acid mine drainage, which is known to affect fish and invertebrate communities. Streams in the Black Hills of South Dakota are generally circumneutral in pH, yet select streams exhibit high iron concentrations associated with natural iron deposits. In this study, we examined relationships among iron concentration, periphyton biomass, macroinvertebrate abundance, and fish assemblages in four Black Hills streams. The stream with the highest iron concentration (~5 …

Use Of Seeded Exotic Grasslands By Wintering Birds, Andrew D. George, Timothy J. O'Connell, Karen R. Hickman, David M. Lesliee Jr.

The Prairie Naturalist

Despite widespread population declines of North American grassland birds, effects of anthropogenic disturbance on wintering habitat of this guild remain poorly understood. We compared avian abundance and habitat structure in fields planted to the exotic grass Old World bluestem (Bothriochloa ischaemum; OWB) to that in native mixed-grass prairie. During winters of 2007–2008 and 2008–2009, we conducted bird and vegetation surveys in six native grass and six OWB fields in Garfield, Grant, and Alfalfa counties, Oklahoma. We recorded 24 species of wintering birds in native fields and 14 species in OWB monocultures. While vegetation structure was similar between field …

How Important Is A Quality Manuscript Review?, Christopher N. Jacques

The Prairie Naturalist

Temperatures are finally starting to cool a bit (for those of us in the northern Great Plains region) and Thanksgiving break is just around the corner.

I offer my reflections in the spirit of encouraging each of you to take a break from your professional obligations and spend time with friends and family enjoying nature and everything it has to offer this fall.

Salamander Colonization Of Chase Lake, Stutsman County, North Dakota, David M. Mushet, Kyle I. Mclean, Craig A. Stockwell

The Prairie Naturalist

Salt concentrations in lakes are dynamic. In the western United States, water diversions have caused significant declines in lake levels resulting in increased salinity, placing many aquatic species at risk (Galat and Robinson 1983, Beutel et al. 2001). Severe droughts can have similar effects on salt concentrations and aquatic communities (Swanson et al. 2003). Conversely, large inputs of water can dilute salt concentrations and contribute to community shifts (Euliss et al. 2004).

Chase Lake is a large, shallow, alkaline lake in east-central North Dakota most famously known for supporting one of the largest breeding colonies of the American white pelican …

A Simple Device For Measuring The Minimum Current Velocity To Maintain Semi-Buoyant Fish Eggs In Suspension, Julias S. Mueller, Brandon D. Cheek, Qingman Chen, Jillian Groeschel, Shannok K. Brewer, Timothy B. Grabowski

The Prairie Naturalist

Pelagic broadcast spawning cyprinids are common to Great Plains rivers and streams. This reproductive guild produces non-adhesive semi-buoyant eggs that require sufficient current velocity to remain in suspension during development. Although studies have shown that there may be a minimum velocity needed to keep the eggs in suspension, this velocity has not been estimated directly nor has the influence of physicochemical factors on egg buoyancy been determined. We developed a simple, inexpensive flow chamber that allowed for evaluation of minimum current velocity needed to keep semi-buoyant eggs in suspension at any time frame during egg development. The device described here …

A Northward Range Extension Of The Hispid Cotton Rat (Sigmodon Hispidus) In Missouri, Cody W. Thompson, Elmer J. Finck

The Prairie Naturalist

The hispid cotton rat (Sigmodon hispidus) is a widely distributed rodent with a geographic range extending from north-central Mexico to southern Nebraska and central Virginia and from southeastern Arizona east to Florida (Carleton et al. 1999, Peppers and Bradley 2000, Wilson and Reeder 2005) with isolated populations in Arizona (Bradley et al. 2012) and California (Clark 1972). Range expansions for the species have been well documented (Clark 1972, Farney 1975, Benedict et al. 2000, Wright et al. 2010, Wills et al. 2011). The majority of these range expansions have occurred across the Central Plains during the 20th century …

Whooping Cranes Consume Plains Leopard Frogs At Migratory Stopover Sites In Nebraska, Keith Geluso, Brad T. Krohn, Mary J. Harner, Michael J. Assenmacher

The Prairie Naturalist

Whooping cranes (Grus americana) currently consist of a single, wild population that migrates annually from breeding grounds at Wood Buffalo National Park, Canada, to wintering grounds on and around the Aransas National Wildlife Refuge along the Texas coast, USA (NRC 2005). This population reached a low of less than 20 individuals in 1941 (Allen 1952) but has rebounded to over 250 individuals (Chavez-Ramirez and Wehtje 2012, Gil-Weir et al. 2012). Whooping cranes migrate approximately 4,000 km each spring and autumn, traversing much of the North American Great Plains (Lewis 1995) and periodically landing along rivers, wetlands, and other …

Relationships Among Walleye Mercury, Selenium, Stable Isotopes, Size And Age, Mark J. Fincel, Robert P. Hanten, Shannon Minerich

The Prairie Naturalist

Bioaccumulation of mercury is well-documented in aquatic ecosystems and occurs as mercury is accumulated and passed up food chains (Kidd et al. 1995, Atwell et al. 1998, Downs et al. 1998). Trophic level correlations have been widely reported for mercury (Snodgrass et al. 2000) and other metals (Barron 1995). Generally, within a system, carnivores have the highest mercury loadings, omnivores intermediate and herbivores the lowest (Phillips et al. 1980). However, little research has focused on the differences in mercury bioaccumulation for a single species that ranges across multiple trophic levels (Burger et al. 2001).

Stable isotope analysis has expanded the …

Landscape Genetics Of The Marbled Salamander (Ambystoma Opacum) At Mammoth Cave National Park, James Kyle Martin

Masters Theses & Specialist Projects

Habitat connectivity is important to maintain in order to prevent loss of genetic diversity, reduce inbreeding depression, and decrease extinction risk in threatened or endangered species. Here I present a landscape genetics study on marbled salamanders (Ambystoma opacum) in highly connected forested habitat at Mammoth Cave National Park. This investigation of gene flow among ponds within a mostly continuous landscape provides data that can be compared with patterns observed in more fragmented landscapes. These comparisons can provide a means of investigating the separate effects of structural and functional habitat connectivity on amphibian genetic population structure. Structural connectivity refers to the …

La Diversidad De Los Análisis De Diversidad La Diversidad De Los Analisis De Diversidad [The Diversity Of Diversity Analyses], Victor D. Carmona-Galindo, Tizziana V. Carmona

Biology Faculty Works

There is a lack of consistency with respect to the use of the terms like species richness, diversity and biodiversity, which extends to the analysis of diversity indices and the merit of using diversity indices in the evaluation (comparison and contrast) of biological communities. The purpose of this article is to provide working definitions for these terms and cite examples from the primary literature that demonstrate the utility of estimating richness, evaluating proportional abundance patterns, as well as comparing indices of diversity and similarity to study patterns of biological organization at different ecological scales. Additionally, we provide a manual in …

First State Record And Interdiction For The Wood Slave, Hemidactylus Mabouia (Moreau De Jonnès 1818) (Gekkonidae), In Maryland, Usa., Louis A. Somma, William L. Grogan Jr.

Papers in Herpetology

The Wood Slave, Hemidactylus mabouia (Moreau de Jonnès 1818; Fig. 1), is indigenous to Africa south of the Sahara, with nonindigenous populations established in Cape Verde, Mexico, much of Central and South America, numerous localities in the Caribbean, perhaps Madagascar, and at least 21 counties in Florida, USA (Carranza and Arnold 2006; Kraus 2009; Krysko et al. 2011a, 2011b; Meshaka 2011; Powell and Henderson 2012). Recently, H. mabouia has successfully invaded temperate regions of southern Africa and northern peninsular Florida (Alexander and Marais 2007, Krysko and Somma 2007).

On 20 December 2012, Brian R. Grogan and Shane Forsythe collected and …

Conservation In The Context Of Climate Change: Practical Guidelines For Land Protection At Local Scales, Kevin Ruddock, Peter V. August, Christopher Damon, Charles Labash, Pamela Rubinoff, Donald Robadue Jr.

Natural Resources Science Faculty Publications

Climate change will affect the composition of plant and animal communities in many habitats and geographic settings. This presents a dilemma for conservation programs – will the portfolio of protected lands we now have achieve a goal of conserving biodiversity in the future when the ecological communities occurring within them change? Climate change will significantly alter many plant communities, but the geophysical underpinnings of these landscapes, such as landform, elevation, soil, and geological properties, will largely remain the same. Studies show that extant landscapes with a diversity of geophysical characteristics support diverse plant and animal communities. Therefore, geophysically diverse landscapes …

Food Sovereignty: An Alternative Paradigm For Poverty Reduction And Biodiversity Conservation In Latin America, M. Jahi Chappell, Hannah Wittman, Christopher M. Bacon, Bruce G. Ferguson, Luis Garcia Barrios, Raúl Garcia Barrios, Daniel Jaffee, Jefferson Lima, V. Ernesto Méndez, Helda Morales, Lorena Soto-Pinto, John Vandermeer, Ivette Perfecto

Sociology Faculty Publications and Presentations

Strong feedback between global biodiversity loss and persistent, extreme rural poverty are major challenges in the face of concurrent food, energy, and environmental crises. This paper examines the role of industrial agricultural intensification and market integration as exogenous socio-ecological drivers of biodiversity loss and poverty traps in Latin America. We then analyze the potential of a food sovereignty framework, based on protecting the viability of a diverse agroecological matrix while supporting rural livelihoods and global food production. We review several successful examples of this approach, including ecological land reform in Brazil, agroforestry, milpa, and the uses of wild varieties in …

Western Burrowing Owl (Athene Cunicularia Hypugaea): Species Conservation Assessment, Melissa J. Panella

Nebraska Game and Parks Commission: Publications

The primary goal in the development of at-risk species conservation assessments is to compile biological and ecological information that may assist conservation practitioners in making decisions regarding the conservation of species of interest. The Nebraska Natural Legacy Project recognizes the western subspecies of Burrowing Owl (Athene cunicularia hypugaea) as a Tier I at-risk species. Provided are some general management recommendations regarding Western Burrowing Owls (hereafter Burrowing Owls). Conservation practitioners will need to use professional judgment for specific management decisions based on objectives, location, and site-specific conditions. Based on a considerable body of literature, this particular species conservation assessment provides an …

Wallace And Incipient Structures: A World Of "More Recondite" Influences, Charles H. Smith

DLPS Faculty Publications

Alfred Russel Wallace is well-known for his co-discovery of the principle of natural selection. Natural selection is usually considered a process, but it is not clear that Wallace regarded it in exactly these terms. In fact he more likely thought of the relationships involved as representing what we would now term a “state space,” a negative feedback loop wherein populations are maintained at healthy levels through elimination of the unfit. Both before and after the advent of natural selection Wallace clung to the idea that “more recondite forces” were shaping the nature and direction of evolution; this is especially evident …

Project Safe Flight: Making New York Safe For Migratory Birds, Kaitlyn L. Parkins, Susan B. Elbin Ph.D., Adriana Palmer, Darren Klein, Elle Barnes

Publications and Research

More than 100 species of migratory birds pass through New York City during spring and fall migrations. Located at the nexus of several migratory routes, New York City’s tall buildings and reflective glass pose a serious threat to over 100 species of migratory birds. Since 1997, NYC Audubon has led Project Safe Flight (PSF), a volunteer-based citizen-science project, with the goal of monitoring and mitigating bird collisions. We examined 16 years of PSF data, during which volunteers collected over 6,000 birds of 126 different species. The top two species, White-throated Sparrow and Common Yellowthroat, make up 23% of all collisions. …

Bailey’S Eastern Woodrat (Neotoma Floridana Baileyi): Species Conservation Assessment, Melissa J. Panella

Nebraska Game and Parks Commission: Publications

The primary goal in development of at-risk species conservation assessments is to compile biological and ecological information that may assist conservation practitioners in making decisions regarding the conservation of species of interest. The Nebraska Natural Legacy Project recognizes the Bailey’s eastern woodrat (Neotama floridana baileyi) as a Tier I at-risk species. Provided are some general management recommendations regarding Bailey’s eastern woodrats. Conservation practitioners will need to use professional judgment for specific management decisions based on objectives, location, and site-specific conditions. This resource was designed to provide an overview of our current knowledge of Bailey’s eastern woodrats and may aid in …

Evaluating The Efficacy Of Land Snail Survey Techniques In Hawaii: Implications For Conservation Throughout The Pacific, Torsten Durkan, Norine Yeung, Wallace Meyer, Kenneth Hayes, Robert Cowie

Department of Biology Faculty Publications

Terrestrial micromolluscs (snails with an adult maximum shell dimension <5 mm) constitute a considerable proportion of the land snail fauna of the Pacific. However, micromolluscs are often underestimated in biological surveys because of size bias. It has been argued that visual searches are preferable on Pacific islands because: (1) size biases are limited based on the understanding that most native Pacific island land snails are very small, and (2) amount of labor is less than other methods such as soil surveys and adequate for inventory purposes (though not for abundance assessments). To test whether visual surveys and soil surveys were accurately recording all taxa, land snail inventories were completed in three forest reserves (5 sampling sites in each) on the island of Oahu, Hawaii. Visual surveys involved 30-min visual search in a 10 m2 site; soil surveys involved sieving leaf litter and topsoil from four 0.3 m2 quadrats and extracting snails with the aid of a microscope. The data indicate a size and microhabitat bias associated with both techniques. Visual surveys consistently collected large arboreal and litter-dwelling species but missed a significant portion of micromolluscs, while soil surveys collected micromolluscs but missed larger snails. Because of such biases, employing both methods is critical for collecting all taxa at a survey location. As such, we recommend that future land snail surveys on Pacific Islands incorporate both survey techniques. Obtaining a complete inventory is critical if we are to understand species distributions and patterns of diversity and make well-informed conservation recommendations.

Variable Δ15n Diet-Tissue Discrimination Factors Among Sharks: Implications For Trophic Position, Diet And Food Web Models, Jill A. Olin, Nigel E. Hussey, Alice Grgicak-Mannion, Mark W. Fritts, Sabine T. Wintner, Aaron T. Fisk

Great Lakes Institute for Environmental Research Publications

The application of stable isotopes to characterize the complexities of a species foraging behavior and trophic relationships is dependent on assumptions of δ15N diet-tissue discrimination factors (∆15N). As ∆15N values have been experimentally shown to vary amongst consumers, tissues and diet composition, resolving appropriate speciesspecific ∆15N values can be complex. Given the logistical and ethical challenges of controlled feeding experiments for determining ∆ 15N values for large and/or endangered species, our objective was to conduct an assessment of a range of reported ∆ 15N values that can hypothetically serve as surrogates for describing the predator-prey relationships of four shark species …

Breeding Bird Communities Associated With Tallgrass Prairies In Southeast Nebraska, Stephen L. Winter, Samuel D. Fuhlendorf, Britt L. Smith

Transactions of the Nebraska Academy of Sciences and Affiliated Societies

We collected data on bird communities associated with tallgrass prairies in two areas of southeast Nebraska that have been identified for focused conservation action: the Sandstone Prairies Biologically Unique Landscape (BUL) and the Southeast Prairies BUL. Our research was conducted in June and July of 2010 and 2011 at 14 privately–owned and state–owned properties located in Gage, Jefferson, Johnson, and Pawnee Counties (Nebraska). We detected a total of 1,108 individuals representing 41 species during 10–minute point counts with 400–m radii. The most commonly encountered species, in descending order of relative abundance (individuals detected per point count) were brown–headed cowbird, dickcissel, …

Pritchardia Boliviensis N. Gen., N. Sp. (Anoplocephalidae: Linstowinae), A Tapeworm From Opossums (Didelphidae) In The Yungas And Lowlands Of Bolivia And Atlantic Forest Of Paraguay, Scott Lyell Gardner, F. Agustín Jiménez Ruiz, Mariel L. Campbell

Harold W. Manter Laboratory of Parasitology: Faculty and Staff Publications

Pritchardia boliviensis n. gen. n. sp. (Anoplocephalidae: Linstowiinae) is described from marsupials (Marmosops noctivagus, Metachirus nudicaudatus, Gracilinanus sp.) collected in Bolivia and Paraguay. These cestodes have a very small strobila with only three segments, regularly alternating genital pores, genital ducts crossing excretory canals ventrally, ovoid to pyriform cirrus sac, three to five testes, external seminal vesicle present and separated from cirrus sac by long seminal duct surrounded by glandular material, uterus ephemeral, eggs forming rapidly in gravid segments, and seminal receptacle present. Pritchardia boliviensis n. sp. includes a single species that occurs in small marsupials in the family …

Sylvatic Species Of Echinococcus From Rodent Intermediate Hosts In Asia And South America, Scott Lyell Gardner, Altangerel T. Dursahinhan, Gábor R. Rácz, Nyamsuren Batsaikhan, Sumiya Ganzorig, David S. Tinnin, Darmaa Damdinbazar, Charles Wood, A. Townsend Peterson, Erika Alandia, José Luís Mollericona, Jorge Salazar-Bravo

Harold W. Manter Laboratory of Parasitology: Faculty and Staff Publications

During a global survey of the diversity of vertebrates and their parasites including the Gobi and desert/steppe biomes ranging from south central to western Mongolia, we found metacestodes (larvae) of Echinococcus multilocularis (Leuckart 1863) in the liver of an individual vole (Microtus limnophilus Büchner 1889) collected in grassland habitat at Har Us Lake, southeast of Hovd, Mongolia. Positive identification of E. multilocularis from near Hovd was made via comparative cyst morphology, study of hooks from the rostellum derived from protoscolexes, and DNA sequencing of the COX1 mitochondrial gene extracted from tissue of the cysts frozen in the field. This …

Fringed Myotis (Myotis Thysanodes Pahasapensis): Species Conservation Assessment, Melissa J. Panella

Nebraska Game and Parks Commission: Publications

The primary goal in development of at-risk species conservation assessments is to compile biological and ecological information that may assist conservation practitioners in making decisions regarding the conservation of species of interest. The Nebraska Natural Legacy Project recognizes the fringed myotis (Myotis thysanodes pahasapensis) as a Tier I at-risk species. Provided are some general management recommendations regarding the fringed myotis. Conservation practitioners will need to use professional judgment to make specific management decisions based on objectives, location, and a multitude of variables. This resource was designed to share available knowledge of the fringed myotis that will aid in the decision-making …

The Tiger Genome And Comparative Analysis With Lion And Snow Leopard Genomes, Yun Sung Cho, Li Hu, Haolong Hou, Hang Lee, Jiaohui Xu, Soowhan Kwon, Sukhun Oh, Hak-Min Kim, Sungwoong Jho, Sangsoo Kim, Young-Ah Shin, Byung Chul Kim, Hyunmin Kim, Chang-Uk Kim, Shu-Jin Luo, Warren E. Johnson, Klaus-Peter Koepfli, A. Schmidt-Kunzel, Jason A. Turner, L. Marker, Cindy K. Harper, Susan M. Miller, Wilhelm Jacobs, Laura D. Bertola, Tae Hyung Kim, Sunghoon Lee, Qian Zhou, Hyun-Ju Jung, Xiao Xu, Priyvrat Gadhvi, Pengwei Xu, Yingqi Xiong, Yadan Luo, Shengkai Pan, Caiyun Gou, Xiuhui Chu, Jilin Zhang, Sanyang Liu, Jing He, Ying Chen, Linfeng Yang, Yulan Yang, Jiaju He, Sha Liu, Junyi Wang, Chul Hong Kim, Hwanjong Kwak, Jong-Soo Kim, Seungwoo Hwang, Junsu Ko, Chang-Bae Kim, Sangtae Kim, Damdin Bayarlkhagva, Woon Kee Paek, Seong-Jin Kim, Stephen J. O'Brien, Jun Wang, Jong Bhak

Biology Faculty Articles

Tigers and their close relatives (Panthera) are some of the world’s most endangered species. Here we report the de novo assembly of an Amur tiger whole-genome sequence as well as the genomic sequences of a white Bengal tiger, African lion, white African lion and snow leopard. Through comparative genetic analyses of these genomes, we find genetic signatures that may reflect molecular adaptations consistent with the big cats’ hypercarnivorous diet and muscle strength. We report a snow leopard-specific genetic determinant in EGLN1 (Met39>Lys39), which is likely to be associated with adaptation to high altitude. We also detect a …

Four Decades Of Andean Timberline Migration And Implications For Biodiversity Loss With Climate Change, David A. Lutz, Rebecca L. Powell, Miles R. Silman

Dartmouth Scholarship

Rapid 21st-century climate change may lead to large population decreases and extinction in tropical montane cloud forest species in the Andes. While prior research has focused on species migrations per se, ecotones may respond to different environmental factors than species. Even if species can migrate in response to climate change, if ecotones do not they can function as hard barriers to species migrations, making ecotone migrations central to understanding species persistence under scenarios of climate change. We examined a 42-year span of aerial photographs and high resolution satellite imagery to calculate migration rates of timberline–the grassland-forest ecotone–inside and outside of …