Digital Commons Network^™

Complete Genome Sequences Of Evolved Arsenate-Resistant Metallosphaera Sedula Strains, Chenbing Ai, Samuel Mccarthy, Wendy Schackwitz, Joel Martin, Anna Lipzen, Paul H. Blum

School of Biological Sciences: Faculty Publications

Metallosphaera sedula is a thermoacidophilic crenarchaeote with a 2.19-Mb genome. Here, we report the genome sequences of several evolved derivatives of M. sedula generated through adaptive laboratory evolution for enhanced arsenate resistance.

Generation Of An Attenuated, Cross-Protective Pepino Mosaic Virus Variant Through Alignment-Guided Mutagenesis Of The Viral Capsid Protein, Godwill M. Chewachong, Sally A. Miller, Joshua J. Blakeslee, David M. Francis, Thomas Jack Morris, Feng Qu

School of Biological Sciences: Faculty Publications

Mild variants of many viruses are able to protect infected plants from subsequent invasion by more severe variants of the same viruses through a process known as cross-protection. In the past, the cross-protective viral variants were commonly derived from mild field isolates that were sometimes genetically heterogeneous, providing variable levels of crossprotection. Here, we report a novel approach to rapidly generate crossprotective variants of the tomato-infecting Pepino mosaic virus (PepMV) independently of the availability of mild field isolates. Our approach sought to attenuate PepMV by mutating less conserved amino acid residues of the abundantly produced capsid protein (CP). These less-conserved …

Synergistic And Independent Actions Of Multiple Terminal Nucleotidyl Transferases In The 3’ Tailing Of Small Rnas In Arabidopsis, Xiaoyan Wang, Shuxin Zhang, Yongchao Dou, Chi Zhang, Xuemei Chen, Bin Yu, Guodong Ren

School of Biological Sciences: Faculty Publications

All types of small RNAs in plants, piwi-interacting RNAs (piRNAs) in animals and a subset of siRNAs in Drosophila and C. elegans are subject to HEN1 mediated 3’ terminal 2’-Omethylation. This modification plays a pivotal role in protecting small RNAs from 3’ uridylation, trimming and degradation. In Arabidopsis, HESO1 is a major enzyme that uridylates small RNAs to trigger their degradation. However, U-tail is still present in null hen1 heso1 mutants, suggesting the existence of (an) enzymatic activities redundant with HESO1. Here, we report that UTP: RNA uridylyltransferase (URT1) is a functional paralog of HESO1. URT1 interacts with AGO1 and …

What Drives Masting? The Phenological Synchrony Hypothesis, Walter D. Koenig, Johannes M.H. Knops, William J. Carmen, Ian S. Pearse

School of Biological Sciences: Faculty Publications

Annually variable and synchronous seed production, or masting behavior, is a widespread phenomenon with dramatic effects on wildlife populations and their associated communities. Proximally, masting is often correlated with environmental factors and most likely involves differential pollination success and resource allocation, but little is known about how these factors interact or how they influence seed production. We studied masting in the valley oak (Quercus lobata Nee), a California endemic tree, and report evidence that phenological synchrony in flowering driven by microclimatic variability determines the size of the acorn crop through its effects on pollen availability and fertilization success. These …

Pollen Limitation And Flower Abortion In A Wind-Pollinated, Masting Tree, Ian S. Pearse, Walter D. Koenig, Kyle A. Funk, Mario B. Pesendorfer

School of Biological Sciences: Faculty Publications

Pollen limitation is a key assumption of theories that explain mast seeding, which is common among wind-pollinated and woody plants. In particular, the pollen coupling hypothesis and pollination Moran effect hypothesis assume pollen limitation as a factor that synchronizes seed crops across individuals. The existence of pollen limitation has not, however, been unambiguously demonstrated in wind-pollinated, masting trees. We conducted a two-year pollen supplementation experiment on a masting oak species, Quercus lobata. Supplemental pollen increased acorn set in one year but not in the other, supporting the importance of pollen coupling and pollination Moran effect models of mast seeding. …

Transgenic Virus Resistance In Crop-Wild Cucurbita Pepo Does Not Prevent Vertical Transmission Of Zucchini Yellow Mosaic Virus, H. E. Simmons, H. R. Prendeville, J. P. Dunham, M. J. Ferrari, J. D. Earnest, Diana Pilson, G. P. Munkvold, E. C. Holmes, A. G. Stephenson

School of Biological Sciences: Faculty Publications

Zucchini yellow mosaic virus (ZYMV) is an economically important pathogen of cucurbits that is transmitted both horizontally and vertically. Although ZYMV is seed-transmitted in Cucurbita pepo, the potential for seed transmission in virus-resistant transgenic cultivars is not known. We crossed and backcrossed a transgenic squash cultivar with wild C. pepo, and determined whether seed-to-seedling transmission of ZYMV was possible in seeds harvested from transgenic backcrossed C. pepo.We then compared these transmission rates to those of non-transgenic (backcrossed and wild) C. pepo. The overall seed-to-seedling transmission rate in ZYMV was similar to those found in previous studies …

Integral Projection Models Show Exotic Thistle Is More Limited Than Native Thistle By Ambient Competition And Herbivory, Brigitte Tenhumberg, Tomomi Suwa, Andrew J. Tyre, F. Leland Russell, Svata M. Louda

School of Biological Sciences: Faculty Publications

Both competitors and natural enemies can limit plant population growth. However, demographic comparisons of the effects of these interactions on introduced versus co-occurring, related native species are uncommon. We asked: (1) does plant competition, insect herbivory, or their combination reduce population growth rate, log λ, of the Eurasian thistle Cirsium vulgare sufficiently to explain its limited invasiveness in western tallgrass prairie; and (2) how do the effects of these interactions compare to those for C. altissimum, its co-occurring, synchronously-flowering native congener? We developed integral projection models (IPMs) to estimate log λ for both species, using parameter estimates from field …

Terrestrial Orchids In A Tropical Forest: Best Sites For Abundance Differ From Those For Reproduction, Melissa Whitman, James D. Ackerman

School of Biological Sciences: Faculty Publications

Suitable habitat for a species is often modeled by linking its distribution patterns with landscape characteristics. However, modeling the relationship between fitness and landscape characteristics is less common. In this study we take a novel approach towards species distribution modeling (SDM) by investigating factors important not only for species occurrence, but also abundance and physical size, as well as fitness measures. We used the Neotropical terrestrial orchid Prescottia stachyodes as our focal species, and compiled geospatial information on habitat and neighboring plants for use in a two-part conditional SDM that accounted for zero inflation and reduced spatial autocorrelation bias. First, …

Revisiting Operons: An Analysis Of The Landscape Of Transcriptional Units In E. Coli, Xizeng Mao, Qin Ma, Bingqiang Liu, Xin Chen, Hanyuan Zhang, Ying Xu

School of Biological Sciences: Faculty Publications

Background: Bacterial operons are considerably more complex than what were thought. At least their components are dynamically rather than statically defined as previously assumed. Here we present a computational study of the landscape of the transcriptional units (TUs) of E. coli K12, revealed by the available genomic and transcriptomic data, providing new understanding about the complexity of TUs as a whole encoded in the genome of E. coli K12.

Results and conclusion: Our main findings include that (i) different TUs may overlap with each other by sharing common genes, giving rise to clusters of overlapped TUs (TUCs) along the genomic …

Convergent Evolution Of Hemoglobin Function In High-Altitude Andean Waterfowl Involves Limited Parallelism At The Molecular Sequence Level, Chandrasekhar Natarajan, Joana Projecto-Garcia, Hideaki Moriyama, Roy E. Weber, Violeta Muñoz-Fuentes, Andy J. Green, Cecilia Kopuchian, Pablo L. Tubaro, Luis Alza, Mariana Bulgarella, Matthew M. Smith, Robert E. Wilson, Angela Fago, Kevin G. Mccracken, Jay F. Storz

School of Biological Sciences: Faculty Publications

A fundamental question in evolutionary genetics concerns the extent to which adaptive phenotypic convergence is attributable to convergent or parallel changes at the molecular sequence level. Here we report a comparative analysis of hemoglobin (Hb) function in eight phylogenetically replicated pairs of high- and low-altitude waterfowl taxa to test for convergence in the oxygenation properties of Hb, and to assess the extent to which convergence in biochemical phenotype is attributable to repeated amino acid replacements. Functional experiments on native Hb variants and protein engineering experiments based on sitedirected mutagenesis revealed the phenotypic effects of specific amino acid replacements that were …

Gillespie Eco-Evolutionary Models (Gems) Reveal The Role Of Heritable Trait Variation In Eco-Evolutionary Dynamics, John Delong, Jean P. Gibert

School of Biological Sciences: Faculty Publications

Heritable trait variation is a central and necessary ingredient of evolution. Trait variation also directly affects ecological processes, generating a clear link between evolutionary and ecological dynamics. Despite the changes in variation that occur through selection, drift, mutation, and recombination, current ecoevolutionary models usually fail to track how variation changes through time. Moreover, eco-evolutionary models assume fitness functions for each trait and each ecological context, which often do not have empirical validation. We introduce a new type of model, Gillespie eco-evolutionary models (GEMs), that resolves these concerns by tracking distributions of traits through time as ecoevolutionary dynamics progress. This is …

Structural Insights Into The Mechanism Defining Substrate Affinity In Arabidopsis Thaliana Dutpase: The Role Of Tryptophan 93 In Ligand Orientation, Noriko Inoguchi, Kittichai Chaiseeda, Mamoru Yamanishi, Moon Ki Kim, Yunho Jang, Mamta Bajaj, Catherine P. Chia, Donald F. Becker, Hideaki Moriyama

School of Biological Sciences: Faculty Publications

Background: Deoxyuridine triphosphate nucleotidohydrolase (dUTPase) hydrolyzes dUTP to dUMP and pyrophosphate to maintain the cellular thymine-uracil ratio. dUTPase is also a target for cancer chemotherapy. However, the mechanism defining its substrate affinity remains unclear. Sequence comparisons of various dUTPases revealed that Arabidopsis thaliana dUTPase has a unique tryptophan at position 93, which potentially contributes to its degree of substrate affinity. To better understand the roles of tryptophan 93, A. thaliana dUTPase was studied.

Results: Enzyme assays showed that A. thaliana dUTPase belongs to a high-affinity group of isozymes, which also includes the enzymes from Escherichia coli and Mycobacterium tuberculosis. Enzymes …

Genetically Based Low Oxygen Affinities Of Felid Hemoglobins: Lack Of Biochemical Adaptation To High-Altitude Hypoxia In The Snow Leopard, Jan E. Janecka, Simone S. E. Nielsen, Sidsel D. Andersen, Federico G. Hoffmann, Roy E. Weber, Trevor Anderson, Jay F. Storz, Angela Fago

School of Biological Sciences: Faculty Publications

Genetically based modifications of hemoglobin (Hb) function that increase blood–O₂ affinity are hallmarks of hypoxia adaptation in vertebrates. Among mammals, felid Hbs are unusual in that they have low intrinsic O₂ affinities and reduced sensitivities to the allosteric cofactor 2,3-diphosphoglycerate (DPG). This combination of features compromises the acclimatization capacity of blood–O2 affinity and has led to the hypothesis that felids have a restricted physiological niche breadth relative to other mammals. In seeming defiance of this conjecture, the snow leopard (Panthera uncia) has an extraordinarily broad elevational distribution and occurs at elevations above 6000 m in the Himalayas. Here, …

Females Sample More Males At High Nesting Densities, But Ultimately Obtain Less Attractive Mates, Robin M. Tinghitella, Chelsea Stehle, Janette W. Boughman

School of Biological Sciences: Faculty Publications

Background: Sexual selection is largely driven by the availability of mates. Theory predicts that male competition and female choice should be density-dependent, with males competing more intensely at relatively high density, and females becoming increasingly discriminating when there are more males from whom to choose. Evidence for flexible mating decisions is growing, but we do not understand how environmental variation is incorporated into mate sampling strategies. We mimicked threespine stickleback (Gasterosteus aculeatus) breeding conditions in pools with high and low densities of nesting males and allowed females to search for mates to determine whether 1) mate search strategies change with …

Nutritional Physiology Of Life-History Trade-Offs: How Food Protein–Carbohydrate Content Influences Life-History Traits In The Wing-Polymorphic Cricket Gryllus Firmus, Rebecca M. Clark, Anthony J. Zera, Spencer T. Behmer

School of Biological Sciences: Faculty Publications

Although life-history trade-offs result from the differential acquisition and allocation of nutritional resources to competing physiological functions, many aspects of this topic remain poorly understood. Wing-polymorphic insects, which possess alternative morphs that trade off allocation to flight capability versus early reproduction, provide a good model system for exploring this topic. In this study, we used the wing-polymorphic cricket Gryllus firmus to test how expression of the flight capability versus reproduction trade-off was modified across a heterogeneous protein–carbohydrate nutritional landscape. Newly molted adult female long- and short-winged crickets were given one of 13 diets with different concentrations and ratios of protein …

Epistasis Constrains Mutational Pathways Of Hemoglobin Adaptation In High-Altitude Pikas, Danielle M. Tufts, Chandrasekhar Natarajan, Inge G. Revsbech, Joana Projecto- Garcia, Federico G. Hoffmann, Roy E. Weber, Angela Fago, Hideaki Moriyama, Jay F. Storz

School of Biological Sciences: Faculty Publications

A fundamental question in evolutionary genetics concerns the roles of mutational pleiotropy and epistasis in shaping trajectories of protein evolution. This question can be addressed most directly by using site-directed mutagenesis to explore the mutational landscape of protein function in experimentally defined regions of sequence space. Here, we evaluate how pleiotropic trade-offs and epistatic interactions influence the accessibility of alternative mutational pathways during the adaptive evolution of hemoglobin (Hb) function in high-altitude pikas (Mammalia: Lagomorpha). By combining ancestral protein resurrection with a combinatorial protein-engineering approach, we examined the functional effects of sequential mutational steps in all possible pathways that produced …

Contribution Of A Mutational Hot Spot To Hemoglobin Adaptation In High-Altitude Andean House Wrens, Spencer C. Galen, Chandrasekhar Natarajan, Hideaki Moriyama, Roy E. Weber, Angela Fago, Phred M. Benham, Andrea N. Chavez, Zachary A. Cheviron, Jay F. Storz, Christopher C. Witt

School of Biological Sciences: Faculty Publications

A key question in evolutionary genetics is why certain mutations or certain types of mutation make disproportionate contributions to adaptive phenotypic evolution. In principle, the preferential fixation of particular mutations could stem directly from variation in the underlying rate of mutation to function-altering alleles. However, the influence of mutation bias on the genetic architecture of phenotypic evolution is difficult to evaluate because data on rates of mutation to function-altering alleles are seldom available. Here, we report the discovery that a single point mutation at a highly mutable site in the βA-globin gene has contributed to an evolutionary change in hemoglobin …

Thermosensitive Gel Containing Cellulose Acetate Phthalate-Efavirenz Combination Nanoparticles For Prevention Of Hiv-1 Infection, Abhijit A. Date, Annemarie Shibata, Emily Mcmullen, Krista La Bruzzo, Patrick Bruck, Michael Belshan, You Zhou, Christopher J. Destache

Nebraska Center for Biotechnology: Faculty and Staff Publications

The objective of this investigation was to develop and evaluate a nano-microbicide containing a combination of cellulose acetate phthalate (HIV-1 entry inhibitor) and efavirenz (anti-HIV agent) for HIV prophylaxis. Cellulose acetate phthalate-efavirenz combination nanoparticles (CAP-EFV-NPs) were fabricated by the nanoprecipitation method and were characterized for particle size, zeta potential and encapsulation efficiency of efavirenz. CAP-EFV-NPs were incorporated into a thermosensitive gel (CAP-EFV-NP-Gel). CAP-EFV-NPs, CAP-EFV-NP-Gel and efavirenz solution were evaluated for cytotoxicity to HeLa cells and for in vitro short-term (1-day) and long-term (3-day) prophylaxis against HIV-1 infection in TZM-bl cells. CAP-EFV-NPs had size < 100 nm, negative surface charge and encapsulation efficiency of efavirenz was > 98%. CAP-EFV-NPs and CAP-EFV-NP-Gel were significantly less …

Globally, Functional Traits Are Weak Predictors Of Juvenile Tree Growth, And We Do Not Know Why, C. E. Timothy Paine, Lucy Amissah, Harald Auge, Christopher Baraloto, Martin Baruffol, Nils Bourland, Helge Bruelheide, Kasso Dainou, Roland C. De Gouvenain, Jean-Louis Doucet, Susan Doust, Paul V. A. Fine, Claire Fortunel, Josephine Haase, Karen D. Holl, Herve Jactel, Xuefei Li, Kaoru Kitajima, Julia Koricheva, Cristina Martinez-Garza, Christian Messier, Alain Paquette, Christopher Philipson, Daniel Piotto, Lourens Poorter, Juan M. Posada, Catherine Potvin, Kalle Rainio, Sabrina E. Russo, Mariacarmen Ruiz-Jaen, Michael Scherer-Lorenzen, Campbell O. Webb, S. Joseph Wright, Rakan A. Zahawi, Andy Hector

School of Biological Sciences: Faculty Publications

1. Plant functional traits, in particular specific leaf area (SLA), wood density and seed mass, are often good predictors of individual tree growth rates within communities. Individuals and species with high SLA, low wood density and small seeds tend to have faster growth rates. 2. If community-level relationships between traits and growth have general predictive value, then similar relationships should also be observed in analyses that integrate across taxa, biogeographic regions and environments. Such global consistency would imply that traits could serve as valuable proxies for the complex suite of factors that determine growth rate, and, therefore, could underpin a …

Evaluation Of Stem Rot In 339 Bornean Tree Species: Implications Of Size, Taxonomy, And Soil-Related Variation For Aboveground Biomass Estimates, K. D. Heineman, S. E. Russo, I. C. Baillie, J. D. Mamit, P. P.-K. Chai, L. Chai, E. W. Hindley, B.-T. Lau, S. Tan, P. S. Ashton

School of Biological Sciences: Faculty Publications

Fungal decay of heart wood creates hollows and areas of reduced wood density within the stems of living trees known as stem rot. Although stem rot is acknowledged as a source of error in forest aboveground biomass (AGB) estimates, there are few data sets available to evaluate the controls over stem rot infection and severity in tropical forests. Using legacy and recent data from 3180 drilled, felled, and cored stems in mixed dipterocarp forests in Sarawak, Malaysian Borneo, we quantified the frequency and severity of stem rot in a total of 339 tree species, and related variation in stem rot …

Genome-Wide Gene Expression In Relation To Age In Large Laboratory Cohorts Of Drosophila Melanogaster, Kimberly A. Carlson, Kylee Gardner, Anjeza Pashaj, Darby J. Carlson, Fang Yu, James D. Eudy, Chi Zhang, Lawrence G. Harshman

School of Biological Sciences: Faculty Publications

Aging is a complex process characterized by a steady decline in an organism’s ability to perform life-sustaining tasks. In the present study, two cages of approximately 12,000 mated Drosophila melanogaster females were used as a source of RNA from individuals sampled frequently as a function of age. A linear model for micro array data method was used for the micro array analysis to adjust for the box effect; it identified 1,581 candidate aging genes.Cluster analyses using a self-organizing map algorithm on the 1,581 significant genes identified gene expression patterns across different ages. Genes involved in immune system function and regulation, …

Transcriptional ‘Memory’ Of A Stress: Transient Chromatin And Memory (Epigenetic) Marks At Stress-Response Genes, Zoya Avramova

School of Biological Sciences: Faculty Publications

Drought, salinity, extreme temperature variations, pathogen and herbivory attacks are recurring environmental stresses experienced by plants throughout their life. To survive repeated stresses, plants provide responses that may be different from their response during the first encounter with the stress. A different response to a similar stress represents the concept of ‘stress memory’. A coordinated reaction at the organismal, cellular and gene/genome levels is thought to increase survival chances by improving the plant’s tolerance/ avoidance abilities. Ultimately, stress memory may provide a mechanism for acclimation and adaptation. At the molecular level, the concept of stress memory indicates that the mechanisms …

Parasitology In An Archaeological Context: Analysis Of Medieval Burials In Nivelles, Belgium, S. E. Rácz, Elisa Pucu De Araujo, E. Jensen, C. Mostek, Johnica J. Morrow, M. L. Van Hove, R. Bianucci, D. Willems, F. Heller, Adauto Araujo, Karl Reinhard

Karl Reinhard Publications

Coprolites were recovered from three burials near the Grand Place of Nivelles, Belgium. These remains yielded evidence of geohelminth parasitism. The evidence contributes to studies of differential parasite egg preservation related to the taphonomic conditions within the three burials. Using coprolite analysis techniques, parasite egg concentrations were quantified for each burial. Coprolites from the individual in Burial 122 were abnormally large and abundant, indicating an intestinal blockage. Additionally, this individual hosted an extremely high number of parasites evinced by the calculated parasite egg concentrations (Trichuris trichiura = 1,577,679 total eggs; Ascaris lumbricoides = 202,350 total eggs). Statistical analyses revealed …

Paleoparasitology – Human Parasites In Ancient Material, Adauto Araújo, Karl Reinhard, Luiz Fernando Ferreira

Karl Reinhard Publications

Parasite finds in ancient material launched a new field of science: paleoparasitology. Ever since the pioneering studies, parasites were identified in archaeological and paleontological remains, some preserved for millions of years by fossilization. However, the paleoparasitological record consists mainly of parasites found specifically in human archaeological material, preserved in ancient occupation sites, from prehistory until closer to 2015. The results include some helminth intestinal parasites still commonly found in 2015, such as Ascaris lumbricoides, Trichuris trichiura and hookworms, besides others such as Amoebidae and Giardia intestinalis, as well as viruses, bacteria, fungi and arthropods. These parasites as a …

Forensic Palynological Analysis Of Intestinal Contents Of A Korean Mummy, Paulette Arguelles, Karl Reinhard, Dong Hoon Shin

Karl Reinhard Publications

Experimental studies show that pollen resides in the intestinal tract for a minimum of seven days to at least 21 days. Because of this long residence time, pollen analysis is an important avenue of forensic research. Pollen provides evidence of the environment of the decedent as well as foods and medicine. We analyzed a coprolite recovered from a Korean mummy. The decedent was a high-ranking general who lived during the 16th or 17th centuries. Twenty pollen types were recovered. These ranged from 100s to 10,000s of pollen grains per gram of coprolite. Importantly, comparison of the coprolite pollen spectrum to …

Prehistoric Earth Oven Facilities And The Pathoecology Of Chagas Disease In The Lower Pecos Canyonlands, Karl Reinhard, Adauto Araujo

School of Natural Resources: Faculty Publications

Understanding the endemic region of a disease is part of developing a concept of the disease’s natural history and its threat to human health in both ancient and modern times. Chagas disease is caused by the parasite Trypanosoma cruzi and has recently been identified as an emergent disease in North America. Ancient endemicity and reemergence has been demonstrated by an examination of a mummy found on the border between Coahuila, Mexico and Texas, USA. This mummified man, who died over 1000 years ago, exhibits the gross pathology of megacolon, which is consistent with Chagas disease. We are now exploring the …

Electrostatic Charge On Flying Hummingbirds And Its Potential Role In Pollination, Marc Badger, Victor Manuel Ortega-Jimenez, Lisa Von Ribenau, Ashley Smiley, Robert Dudley, Alexei Gruverman , Editor

Alexei Gruverman Publications

Electrostatic phenomena are known to enhance both wind- and insect-mediated pollination, but have not yet been described for nectar-feeding vertebrates. Here we demonstrate that wild Anna's Hummingbirds (Calypte anna) can carry positive charges up to 800 pC while in flight (mean ± s.d.: 66 ± 129 pC). Triboelectric charging obtained by rubbing an isolated hummingbird wing against various plant structures generated charges up to 700 pC. A metal hummingbird model charged to 400 pC induced bending of floral stamens in four plants (Nicotiana, Hemerocallis, Penstemon, and Aloe spp.), and also attracted falling Lycopodium spores at distances of < 2 mm. Electrostatic forces may therefore influence pollen transfer onto nectar-feeding birds.

Monthly Land Cover-Specific Evapotranspiration Models Derived From Global Eddy Flux Measurements And Remote Sensing Data, Yuan Fang, Ge Sun, Peter Caldwell, Steven G. Mcnulty, Asko Noormets, Jean-Christophe Domec, John King, Zhiqiang Zhang, Xudong Zhang, Guanghui Lin, Guangsheng Zhou, Jingfeng Xiao, Jiquan Chen

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

Evapotranspiration (ET) is arguably the most uncertain ecohydrologic variable for quantifying watershed water budgets. Although numerous ET and hydrological models exist, accurately predicting the effects of global change on water use and availability remains challenging because of model deficiency and/or a lack of input parameters. The objective of this study was to create a new set of monthly ET models that can better quantify landscape-level ET with readily available meteorological and biophysical information. We integrated eddy covariance flux measurements from over 200 sites, multiple year remote sensing products from the Moderate Resolution Imaging Spectroradiometer (MODIS), and statistical modelling. Through examining …

Scarification And Gap Size Have Interacting Effects On Northern Temperate Seedling Establishment, John L. Willis, Michael B. Walters, Kurt W. Gottschallk

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

After decades focused on promoting economically valuable species, management of northern temperate forests has increasingly become focused on promoting tree species diversity. Unfortunately, many formerly common species that could contribute to diversity including yellow birch (Betula alleghaniensis Britton.), paper birch (Betula papyrifera Marsh), eastern hemlock (Tsuga canadensis L.), and eastern white pine (Pinus strobus L.) are now uncommon in the seedling layer, raising concerns about our ability to use these species to increase diversity. In this study, two related seed addition experiments conducted in 45 variably-sized harvest gaps (unharvested to 6500 m^2) in adjacent mesic northern hardwood stands, Emmet County, …

Wildland Fire Deficit And Surplus In The Western United States, 1984–2012, Sean A. Parks, Carol Miller, Marc-André Parisien, Lisa M. Holsinger, Solomon Z. Dobrowski, John Abatzoglou

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

Wildland fire is an important disturbance agent in the western US and globally. However, the natural role of fire has been disrupted in many regions due to the influence of human activities, which have the potential to either exclude or promote fire, resulting in a ‘‘fire deficit’’ or ‘‘fire surplus’’, respectively. In this study, we developed a model of expected area burned for the western US as a function of climate from 1984 to 2012.We then quantified departures from expected area burned to identify geographic regions with fire deficit or surplus. We developed our model of area burned as a …