Scholarly Work - Ecology

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    Exotic grass invasion increases [forage] productivity and reduces diversity of a [high altitude] mesic grassland
    (2021-02) Weaver, T; Bao, S
    Mesic temperate rangeland, e.g. from the North American mixed grass prairie, Rocky Mountain grasslands and southern hemisphere continents is being invaded by the exotic rhizomatous grasses, Poa pratensis and Bromus inermis. To project the effects of their invasion on one grassland, we compared community properties in- and outside of clones invading a level environmentally homogeneous meadow representative of our high altitude fescue grasslands. Yields increased from native vegetation dominated by Festuca idahoenis (Feid, x= 96 gm/m2) through exotic vegetation dominated by Poa (x= 158 gm/m2) to Brome (x= 258 gm/m2) with little difference in forage quality (protein content). Some, e.g. a grazier, might therefore view the change as beneficial. Measurement of community composition in the three communities showed a considerable impoverishment of the native fescue (Feid) community by exotic invasion, an impoverishment understated by measured reduction in species richness [i.e. from Feid (16-12 species per 1.13m2) through Poa (11) to Brome (4 ); species evenness (Simpson) [i.e. from 88-84 to 81 to 42 ]; and life-form evenness (%forb) [i.e, Feid (42-34%) through Poa (23%) to Brome (5%). The impoverishment probably resulted first, from competitive exclusion of natives by lack of soil resources captured by exotics (whose entry surely demonstrated a superior capacity to acquire water and nutrients) and second, for natives associated with taller Brome, from a reduction of ground-level light, a deficiency confirmed by etiolation of the natives. Conservationists will surely decry the losses. Due to the inexorable rhizomatous spread of Poa and Brome and the resultant impossibility of controlling them, we deduce that managers should accept the foresee-able [vegetation] type-conversion and develop methods for managing/using the new vegetation- - a resigned reaction paralleling the response necessary for other anthropogenic factors: urbanization, N-supplementation, pollution and climate change. We expect parallel responses in other mesic grasslands. Sampling and statistics completed 2014- 20l5. 1 st draft reviewed 2016.
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    Roadside habitat: Boon or bane for pollinating insects?
    (Oxford University Press, 2024-01) Meinzen, Thomas C.; Burkle, Laura A.; Debinski, Diane M
    Pollinators, which provide vital services to wild ecosystems and agricultural crops, are facing global declines and habitat loss. As undeveloped land becomes increasingly scarce, much focus has been directed recently to roadsides as potential target zones for providing floral resources to pollinators. Roadsides, however, are risky places for pollinators, with threats from vehicle collisions, toxic pollutants, mowing, herbicides, and more. Although these threats have been investigated, most studies have yet to quantify the costs and benefits of roadsides to pollinators and, therefore, do not address whether the costs outweigh the benefits for pollinator populations using roadside habitats. In this article, we address how, when, and under what conditions roadside habitats may benefit or harm pollinators, reviewing existing knowledge and recommending practical questions that managers and policymakers should consider when planning pollinator-focused roadside management.
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    Wire-snare bushmeat poaching and the large African carnivore guild: Impacts, knowledge gaps, and field-based mitigation
    (Elsevier BV, 2024-01) Becker, Matthew S.; Creel, Scott; Sichande, Mwamba; Reyes de Merkle, Johnathan; Goodheart, Ben; Mweetwa, Thandiwe; Mwape, Henry; Smit, D.; Kusler, A.; Banda, Kambwiri; Musalo, Brian; Mwansa Bwalya, Lengwe
    Wire-snare poaching for bushmeat is increasingly recognized as a serious threat to the species comprising the large African carnivore guild (African lion, African wild dog, spotted hyena, cheetah and leopard), with impacts described primarily through prey depletion and snaring by-catch mortality or injury. However, the species-specific impacts of snaring on this guild and on intraguild dynamics are not well-understood. These guilds evolved through competition and predation and have a diverse array of behaviors, space use, movements, diet, morphology, and densities; thus, it is logical to expect snaring impacts through prey depletion and by-catch will also be variable, subtle, and complex, yet significant. Utilizing the scientific literature and ongoing, long-term research we: 1) Summarize and describe the known and potential impacts of snaring by-catch and prey depletion on specific species in the guild and on intraguild dynamics, 2) Identify knowledge gaps and propose areas of future research to better understand and address snaring threats, and 3) Describe a successful strategy collaboratively merging conservation science work with resource protection, that has been implemented across carnivore strongholds in Zambia to combat the immediate threats from snaring on large carnivore populations. Collectively, this work can help mitigate snaring impacts while longer-term community-based solutions to the bushmeat crisis are developed and implemented.
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    Potentially Adaptive Significance of Genome Size Diversity across Ecological Gradients and Seed Size in Ivesia (Rosaceae)
    (Western North American Naturalist, 2023-10) Borokini, Israel T.; Broderick, Shaun R.; Gao, Zhi; Hallas, Joshua M.; Birchler, James A.; Peacock, Mary M.
    Variation in genome size across taxa has been explained using neutral and nonadaptive theories; however, genome size variation among taxonomic groups can also be shaped by natural selection if it correlates with functional traits. This study investigated the potential adaptive significance of genome size in Ivesia, a radiating genus distributed in the western North American desert ecosystems. We estimated the genome size of 34 taxa (including 31 Ivesia taxa, 2 Potentilla taxa, and 1 Horkelia taxon) using flow cytometric methods. For each taxon, leaf samples were collected from 6 individuals in 1 location each; intraspecific genome size variation was investigated using samples collected from 11 Ivesia webberi populations. The results showed an 8.1-fold variance in genome size, ranging from 0.73 pg/2C in I. baileyi var. beneolens to 5.91 pg/2C in I. lycopodioides var. megalopetala. Only 6 taxa, with a genome size >1.5 pg/2C, significantly differed from the remaining taxa. Genome size in Ivesia is relatively small, which is typical of plants living in stressful environments. Also, genome size was significantly correlated with seed size and actual evapotranspiration both within I. webberi and among Ivesia taxa, thus supporting the predictions of the nucleotype theory and suggesting an adaptive significance of genome size in the genus. Genome size in I. webberi is mostly statistically nonsignificant; however, populations near the center of the species' known range have significantly larger genomes, which decrease in size toward the marginal populations. This intraspecific genome size gradient from range center toward range margins could be attributed to patterns of gene flow and geographic isolation.
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    The evidence for and urgency of threats to African wild dogs from prey depletion and climate change
    (Elsevier BV, 2023-09) Creel, Scott; Becker, Matthew S.; Reyes de Merkle, Johnathan; Goodheart, Ben
    Many African large carnivore populations are declining due to decline of the herbivore populations on which they depend. We recently noted that the densities of true apex carnivores like the lion and spotted hyena correlate strongly with prey density, but competitively subordinate carnivores like the African wild dog benefit from competitive release when density of apex carnivores is low, so the expected effect of a simultaneous decrease in resources and dominant competitors is not obvious. We found that when prey density drops below a tipping point, the relationship of wild dog density to prey density changes sign, and wild dog density declines. We also noted that ‘prey depletion provides a mechanistically direct explanation of patterns in wild dog dynamics that have been attributed to climate change’ (Creel et al., 2023).
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    Yellowstone Cutthroat Trout Recovery in Yellowstone Lake: Complex Interactions Among Invasive Species Suppression, Disease, and Climate Change
    (Wiley, 2023-10) Glassic, Hayley C.; Chagaris, David D.; Guy, Christopher S.; Tronstad, Lusha M.; Lujan, Dominque R.; Briggs, Michelle A.; Albertson, Lindsey K.; Brenden, Travis O.; Walsworth, Timothy E.; Koel, Todd M.
    n Yellowstone Lake, Wyoming, the largest inland population of nonhybridized Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri, hereafter Cutthroat Trout, declined throughout the 2000s because of predation from invasive Lake Trout Salvelinus namaycush, drought, and whirling disease Myxobolus cerebralis. To maintain ecosystem function and conserve Cutthroat Trout, a Lake Trout gill netting suppression program was established in 1995, decreasing Lake Trout abundance and biomass. Yet, the response of Cutthroat Trout to varying Lake Trout suppression levels, collectively with the influence of disease and climate, is unknown. We developed an ecosystem model (calibrated to historical data) to forecast (2020–2050) whether Cutthroat Trout would achieve recovery benchmarks given disease, varying suppression effort, and climate change. Lake Trout suppression influenced Cutthroat Trout recovery; current suppression effort levels resulted in Cutthroat Trout recovering from historical lows in the early 2000s. However, Cutthroat Trout did not achieve conservation benchmarks when incorporating the influence of disease and climate. Therefore, the National Park Service intends to incorporate age‐specific abundance, spawner biomass, or both in conservation benchmarks to provide better indication of how management actions and environmental conditions influence Cutthroat Trout. Our results illustrate how complex interactions within an ecosystem must be simultaneously considered to establish and achieve realistic benchmarks for species of conservation concern.
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    Measuring Understory Fire Effects from Space: Canopy Change in Response to Tropical Understory Fire and What This Means for Applications of GEDI to Tropical Forest Fire
    (MDPI, 2023-01) East, Alyson; Hansen, Andrew; Armenteras, Dolors; Jantz, Patrick; Roberts, David W.
    The ability to measure the ecological effects of understory fire in the Amazon on a landscape scale remains a frontier in remote sensing. The Global Ecosystem Dynamics Investigation’s (GEDI) LiDAR data have been widely suggested as a critical new tool in this field. In this paper, we use the GEDI Simulator to quantify the nuanced effects of understory fire in the Amazon, and assess the ability of on-orbit GEDI data to do the same. While numerous ecological studies have used simulated GEDI data, on-orbit constraint may limit ecological inference. This is the first study that we are aware of that directly compares methods using simulated and on-orbit GEDI data. Simulated GEDI data showed that fire effects varied nonlinearly through the canopy and then moved upward with time since burn. Given that fire effects peaked in the mid-canopy and were often on the scale of 2 to 3 m in height difference, it is unlikely that on-orbit GEDI data will have the sensitivity to detect these same changes.
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    Effects of de-snaring on the demography and population dynamics of African lions
    (Elsevier BV, 2023-10) Banda, Kambwiri; Creel, Scott; Sichande, Mwamba; Mweetwa, Thandiwe; Mwape, Henry; Reyes de Merkle, Johnathan; Mwansa Bwalya, Lengwe; Simpamba, Twakundine; McRobb, Rachel; Becker, Matthew S.
    Lions and other African large carnivores are in decline, due in part to effects of illegal hunting with snares, which can reduce prey availability and directly kill or injure carnivores. It is difficult to effectively remove snares from large ecosystems by patrolling, but an additional approach to reduce effects on large carnivores is to monitor the population closely and de-snare individuals who are found in a snare or have broken free but still carry the wire (often with serious injury). The effectiveness of de-snaring programs to reduce impacts on large carnivores has not been directly tested. Here, we used long-term demographic data from 386 individually identified lions in the Luangwa Valley Ecosystem to test the effects on population growth (λ) and population size (N) of a program to remove snares from injured lions and treat their wounds. Stochastic Leslie matrix projections for a period of five years showed that the population grew with the benefits of de-snaring, but was expected to decline without de-snaring. Mean annual growth (λ) with de-snaring was 1.037 (with growth in 70% of years), closely matching observed changes in population size. Mean annual growth was 0.99 (with growth in 47% of years) for a model that assumed snared animals would have died if not treated, and 0.95 (with growth in 37% of years) for models that also accounted for super-additive effects via the death of dependent cubs and increased infanticide with increased male mortality. De-snaring requires intensive effort, but it can appreciably reduce the effect of snaring on lion population dynamics.
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    The geography of climate and the global patterns of species diversity
    (Springer Science and Business Media LLC, 2023-09) Coelho, Marco Túlio P.; Barreto, Marco Túlio P.; Barreto, Elisa; Rangel, Thiago F.; Diniz-Filho, José Alexandre F.; Wüest, Rafael O.; Bach, Wilhelmine; Skeels, Alexander; McFadden, Ian R.; Roberts, David W.; Pellissier, Loïc; Zimmermann, Niklaus E.; Graham, Catherine H.
    Climate’s effect on global biodiversity is typically viewed through the lens of temperature, humidity and resulting ecosystem productivity1,2,3,4,5,6. However, it is not known whether biodiversity depends solely on these climate conditions, or whether the size and fragmentation of these climates are also crucial. Here we shift the common perspective in global biodiversity studies, transitioning from geographic space to a climate-defined multidimensional space. Our findings suggest that larger and more isolated climate conditions tend to harbour higher diversity and species turnover among terrestrial tetrapods, encompassing more than 30,000 species. By considering both the characteristics of climate itself and its geographic attributes, we can explain almost 90% of the variation in global species richness. Half of the explanatory power (45%) may be attributed either to climate itself or to the geography of climate, suggesting a nuanced interplay between them. Our work evolves the conventional idea that larger climate regions, such as the tropics, host more species primarily because of their size7,8. Instead, we underscore the integral roles of both the geographic extent and degree of isolation of climates. This refined understanding presents a more intricate picture of biodiversity distribution, which can guide our approach to biodiversity conservation in an ever-changing world.
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    Equity, community, and accountability: Leveraging a department-level climate survey as a tool for action
    (Public Library of Science, 2023-08) Barrile, Gabriel M.; Bernard, Riley F.; Wilcox, Rebecca C.; Becker, Justine A.; Dillon, Michael E.; Thomas-Kuzilik, Rebecca R.; Bombaci, Sara P.; Merkle, Bethann Garramon
    Organizational climate is a key determinant of diverse aspects of success in work settings, including in academia. Power dynamics in higher education can result in inequitable experiences of workplace climate, potentially harming the well-being and productivity of employees. Quantifying experiences of climate across employment categories can help identify changes necessary to create a more equitable workplace for all. We developed and administered a climate survey within our academic workplace—the Department of Zoology and Physiology at the University of Wyoming—to evaluate experiences of climate across three employment categories: faculty, graduate students, and staff. Our survey included a combination of closed-response (e.g., Likert-scale) and open-ended questions. Most department members (82%) completed the survey, which was administered in fall 2021. Faculty generally reported more positive experiences than staff. Graduate students often fell between these two groups, though in some survey sections (e.g., mental health and well-being) students reported the most negative experiences of departmental climate. Three common themes emerged from the analysis of open-ended responses: equity, community, and accountability. We discuss how these themes correspond to concrete action items for improving our departmental climate, some of which have been implemented already, while others constitute future initiatives and/or require a collective push towards systemic change in academia. Finally, service work of this type often falls outside of job descriptions, requiring individuals to either work more or trade-off productivity in other areas that are formally evaluated. With the goal of minimizing this burden for others, we detail our process and provide the materials and framework necessary to streamline this process for other departments aiming to evaluate workplace climate as a key first step in building a positive work environment for all employees.
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    Individual life histories: neither slow nor fast, just diverse
    (The Royal Society, 2023-07) Van de Walle, Joanie; Fay, Rémi; Gaillard, Jean-Michel; Pelletier, Fanie; Hamel, Sandra; Gamelon, Marlène; Barbraud, Christophe; Blanchet, F. Guillaume; Blumstein, Daniel T.; Charmantier, Anne; Delord, Karine; Larue, Benjamin; Martin, Julien; Mills, James A.; Milot, Emmanuel; Mayer, Francine M.; Rotella, Jay; Saether, Bernt-Erik; Teplitsky, Céline; van de Pol, Martijn; Van Vuren, Dirk H.; Visser, Marcel E.; Wells, Caitlin P.; Yarrall, John; Jenouvrier, Stéphanie
    The slow–fast continuum is a commonly used framework to describe variation in life-history strategies across species. Individual life histories have also been assumed to follow a similar pattern, especially in the pace-of-life syndrome literature. However, whether a slow–fast continuum commonly explains life-history variation among individuals within a population remains unclear. Here, we formally tested for the presence of a slow–fast continuum of life histories both within populations and across species using detailed long-term individual-based demographic data for 17 bird and mammal species with markedly different life histories. We estimated adult lifespan, age at first reproduction, annual breeding frequency, and annual fecundity, and identified the main axes of life-history variation using principal component analyses. Across species, we retrieved the slow–fast continuum as the main axis of life-history variation. However, within populations, the patterns of individual life-history variation did not align with a slow–fast continuum in any species. Thus, a continuum ranking individuals from slow to fast living is unlikely to shape individual differences in life histories within populations. Rather, individual life-history variation is likely idiosyncratic across species, potentially because of processes such as stochasticity, density dependence, and individual differences in resource acquisition that affect species differently and generate non-generalizable patterns across species.
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    Connectivity between white shark populations off Central California, USA and Guadalupe Island, Mexico
    (Frontiers Media SA, 2023-07) Kanive, Paul E.; Rotella, Jay J.; Chapple, Taylor K.; Anderson, Scot D.; Hoyos-Padilla, Mauricio; Klimley, Abbott Peter; Galván-Magaña, Felipe; Andrzejaczek, Samantha; Block, Barbara A.; Jorgensen, Salvador J.
    Marine animals often move beyond national borders and exclusive economic zones resulting in a need for trans-boundary management spanning multiple national jurisdictions. Highly migratory fish vulnerable to over-exploitation require protections at international level, as exploitation practices can be disparate between adjacent countries and marine jurisdictions. In this study we collaboratively conducted an analysis of white shark connectivity between two main aggregation regions with independent population assessment and legal protection programs; one off central California, USA and one off Guadalupe Island, Mexico. We acoustically tagged 326 sub-adult and adult white sharks in central California (n=210) and in Guadalupe Island (n=116) with acoustic transmitters between 2008-2019. Of the 326 tagged white sharks, 30 (9.20%) individuals were detected at both regions during the study period. We used a Bayesian implementation of logistic regression with a binomial distribution to estimate the effect of sex, maturity, and tag location to the response variable of probability of moving from one region to the other. While nearly one in ten individuals in our sample were detected in both regions over the study period, the annual rate of trans-regional movement was low (probability of movement = 0.015 yr-1, 95% credible interval = 0.002, 0.061). Sub-adults were more likely than adults to move between regions and sharks were more likely to move from Guadalupe Island to central California, however, sex, and year were not important factors influencing movement. This first estimation of demographic-specific trans-regional movement connecting US and Mexico aggregations with high seasonal site fidelity represents an important step to future international management and assessment of the northeastern Pacific white shark population as a whole.
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    A hypothetico‐deductive theory of science and learning
    (Wiley, 2023-08) Kalinowski, Steven T.; Pelakh, Avital
    This article presents a simple, cognitive theory of science and learning. The first section of the paper develops the theory's two main propositions: (i) A wide range of scientific activities rely heavily on one type of reasoning, hypothetical thinking, and (ii) This type of reasoning is also useful to students for learning science content. The second section of the paper presents a taxonomy of multiple‐choice questions that use hypothetical thinking and the third section of the paper tests the theory using data from a college biology course. As expected by the theory, student responses to 24 scientific reasoning questions were consistent with a one‐dimensional psychometric construct. Student responses to the scientific reasoning questions explained 36% of the variance in exam grades. Several directions for additional research are identified, including studying the psychometric structure of scientific thinking in more detail, performing randomized, controlled experiments to demonstrate a causal relationship between scientific thinking and learning, and identifying the relative contribution of other factors to success in college.
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    Lead, trash, DDE, and young age of breeders linked to lower fertility in the first two decades of reintroduction for critically endangered California Condors in California
    (Oxford Academic, 2023-08) Bakker, Victoria J.; Finkelstein, Myra E.; Doak, Daniel F.; Wolstenholme, Rachel; Welch, Alacia; Burnett, Joe; Punzalan, Arianna; Brandt, Joseph; Kirkland, Steve; Seal Faith, Nadya E.
    In the first comprehensive assessment of the reproductive rates of critically endangered California Condors (Gymnogyps californianus) recovering from complete extirpation in the wild, we analyzed 20 years (1999–2018) of data from condor flocks in southern and central California. We found that several anthropogenic threats affected reproductive rates: (1) coastal space use by female condors was associated with lower hatch probability, presumably due to foraging on marine mammals and associated DDE exposure; (2) trash ingestion by chicks decreased fledging probability prior to implementation of trash management in 2007; and (3) all parent deaths during rearing resulted in chick or early fledgling deaths, and most parental deaths were due to lead poisoning. We also detected several effects on reproductive rates from the complex individual-based management of condors, which involves ongoing releases of captive-bred individuals and health interventions including treatment of lead poisoning. Recruitment rates were lower for new release sites, which we attribute to a lack of individual- and flock-level experience. In addition, the number of free-flying days in the wild in the year before first breeding and in the 8 weeks before subsequent breeding was positively associated with female and male recruitment and with female rebreeding probabilities, respectively, indicating that removing individuals from the wild may reduce their breeding success. Finally, probabilities of recruitment, rebreeding, and fledging all increased with age, and given the age distribution skew of the recovering flocks toward younger individuals, overall reproductive success was lower than would be expected at the stable age distribution. Thus, reproductive rates should increase over time as the mean age of California Condors increases if current and emerging threats to reproduction, including the loss of breeders due to lead poisoning, can be addressed.
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    Insect and Pathogen Influences on Tree-Ring Stable Isotopes
    (Springer Nature, 2022-06) Ulrich, Danielle E.M.; Voelker, Steve; Brooks, J. Renée; Meinzer, Frederick C.
    Understanding long-term insect and pathogen effects on host tree physiology can help forest managers respond to insect and pathogen outbreaks, and understand when insect and pathogen effects on tree physiology will be exacerbated by climate change. Leaf-level physiological processes modify the carbon (C) and oxygen (O) stable isotopic composition of elements taken up from the environment, and these modifications are recorded in tree-rings (see Chaps. 9, 10, 16 and 17). Therefore, tree-ring stable isotopes are affected by both the tree’s environment and the tree’s physiological responses to the environment, including insects and pathogens. Tree-ring stable isotopes provide unique insights into the long-term effects of insects and pathogens on host tree physiology. However, insect and pathogen impacts on tree-ring stable isotopes are often overlooked, yet can substantially alter interpretations of tree-ring stable isotopes for reconstructions of climate and physiology. In this chapter, we discuss (1) the effects of insects (defoliators, wood-boring, leaf-feeding), pests (parasitic plants), and pathogens (root and foliar fungi) on host physiology (growth, hormonal regulation, gas exchange, water relations, and carbon and nutrient use) as they relate to signals possibly recorded by C and O stable isotopes in tree-rings, (2) how tree-ring stable isotopes reveal insect and pathogen impacts and the interacting effects of pathogens and climate on host physiology, and (3) the importance of considering insect and pathogen impacts for interpreting tree-ring stable isotopes to reconstruct past climate or physiology.
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    Effects of Soil Microbes on Functional Traits of Loblolly Pine (Pinus taeda) Seedling Families From Contrasting Climates
    (Frontiers Media SA, 2020-01) Ulrich, Danielle E. M.; Sevanto, Sanna; Peterson, Samantha; Ryan, Max; Dunbar, John
    Examining factors that influence seedling establishment is essential for predicting the impacts of climate change on tree species’ distributions. Seedlings originating from contrasting climates differentially express functional traits related to water and nutrient uptake and drought resistance that reflect their climate of origin and influence their responses to drought. Soil microbes may improve seedling establishment because they can enhance water and nutrient uptake and drought resistance. However, the relative influence of soil microbes on the expression of these functional traits between seedling families or populations from contrasting climates is unknown. To determine if soil microbes may differentially alter functional traits to enhance water and nutrient uptake and drought resistance between dry and wet families, seeds of loblolly pine families from the driest and wettest ends of its geographic range (dry, wet) were planted in sterilized sand (controls) or in sterilized sand inoculated with a soil microbial community (inoculated). Functional traits related to seedling establishment (germination), water and nutrient uptake and C allocation (root:shoot biomass ratio, root exudate concentration, leaf C:N, leaf N isotope composition (δ15N)), and drought resistance (turgor loss point, leaf carbon isotope composition (δ13C)) were measured. Then, plants were exposed to a drought treatment and possible shifts in photosynthetic performance were monitored using chlorophyll fluorescence. Inoculated plants exhibited significantly greater germination than controls regardless of family. The inoculation treatment significantly increased root:shoot biomass ratio in the wet family but not in the dry family, suggesting soil microbes alter functional traits that improve water and nutrient uptake more so in a family originating from a wetter climate than in a family originating from a drier climate. Microbial effects on photosynthetic performance during drought also differed between families, as photosynthetic performance of the dry inoculated group declined fastest. Regardless of treatment, the dry family exhibited a greater root:shoot biomass ratio, root exudate concentration, and leaf δ15N than the wet family. This indicates that the dry family allocated more resources belowground than the wet and the two family may have used different sources of plant available N, which may be related to their contrasting climates of origin and influence their drought resistance. Examination of variation in impacts of soil microbes on seedling physiology improves efforts to enhance seedling establishment and beneficial plant-microbe interactions under climate change.
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    Investigating old‐growth ponderosa pine physiology using tree‐rings, δ13C, δ18O, and a process‐based model
    (Wiley, 2019-06) Ulrich, Danielle E. M.; Still, Christopher; Brooks, J. Renée; Kim, Youngil; Meinzer, Frederick C.
    In dealing with predicted changes in environmental conditions outside those experienced today, forest managers and researchers rely on process‐based models to inform physiological processes and predict future forest growth responses. The carbon and oxygen isotope ratios of tree‐ring cellulose (δ13Ccell, δ18Ocell) reveal long‐term, integrated physiological responses to environmental conditions. We incorporated a submodel of δ18Ocell into the widely used Physiological Principles in Predicting Growth (3‐PG) model for the first time, to complement a recently added δ13Ccell submodel. We parameterized the model using previously reported stand characteristics and long‐term trajectories of tree‐ring growth, δ13Ccell, and δ18Ocell collected from the Metolius AmeriFlux site in central Oregon (upland trees). We then applied the parameterized model to a nearby set of riparian trees to investigate the physiological drivers of differences in observed basal area increment (BAI) and δ13Ccell trajectories between upland and riparian trees. The model showed that greater available soil water and maximum canopy conductance likely explain the greater observed BAI and lower δ13Ccell of riparian trees. Unexpectedly, both observed and simulated δ18Ocell trajectories did not differ between the upland and riparian trees, likely due to similar δ18O of source water isotope composition. The δ18Ocell submodel with a Peclet effect improved model estimates of δ18Ocell because its calculation utilizes 3‐PG growth and allocation processes. Because simulated stand‐level transpiration (E) is used in the δ18O submodel, aspects of leaf‐level anatomy such as the effective path length for transport of water from the xylem to the sites of evaporation could be estimated.
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    Faster drought recovery in anisohydric beech compared with isohydric spruce
    (Oxford University Press, 2023-01) Ulrich, Danielle E M; Grossiord, Charlotte
    With drought and heat events increasing in frequency and intensity worldwide, global drought-induced tree decline (Allen et al. 2010, Hammond et al. 2022) has resulted in widespread interest in understanding the physiological mechanisms that underlie tree death. Unprecedented mortality rates threaten forest function and ecosystem services, including carbon (C) sequestration, clean air and water, and recreational and emotional value. Researchers have aimed to understand the mechanisms of tree mortality to better predict which trees will die or survive, inform future forest dynamics and improve forest management practices (McDowell et al. 2008, 2011, Raffa et al. 2008, Sevanto et al. 2014, Gaylord et al. 2015, Adams et al. 2017).
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    Functional traits underlie specialist-generalist strategies in whitebark pine and limber pine
    (Elsevier BV, 2023-08) Ulrich, Danielle E.M.; Wasteneys, Chloe; Hoy-Skubik, Sean; Alongi, Franklin
    Plant species life history strategies are described by functional variation spanning an acquisitive and conservative resource use continuum. Specialist species can exhibit traits promoting one end of the continuum, while generalist species can display traits promoting both acquisitive and conservative resource use. Whitebark pine (Pinus albicaulis, PIAL) and limber pine (Pinus flexilis, PIFL) are two high-elevation pines that have similar growth and morphology, yet contrasting elevational distributions with PIAL viewed as a specialist inhabiting a narrower elevation range, and PIFL as a generalist inhabiting a broader elevation range. We compared the physiological and morphological traits of greenhouse-grown 5-year-old PIAL and PIFL. Our results suggest that PIFL’s acquisitive and conservative resource use traits contribute to its generalist strategy and ability to inhabit a greater range of elevations than PIAL. PIFL had greater acquisitive resource use traits including: high-light tolerance (greater Qsat, greater fascicle density), increased biomass allocation to photosynthetic tissue (higher needle biomass, aboveground:belowground biomass, needle:branch + stem biomass), and higher C and water uptake (greater stomatal density and size, higher C assimilation rate), as well as greater conservative resource use traits including: greater physical stress resistance (shorter height, higher stem and branch diameters, greater branch and stem diameter:length), drought tolerance (higher SWC, leaf starch proportion), and drought avoidance (earlier budburst phenology, smaller hydroscape area) than PIAL. Our results suggest that PIFL may make more efficient use of high-light loads and maximize C and water uptake when moisture is abundant during spring snowmelt before the onset of dry summer conditions. Other conservative resource use traits describing cold tolerance, heat tolerance, and drought tolerance did not differ between species, suggesting that both species exhibit traits that promote similar conservative resource use enabling their overlapping persistence at higher elevations. Comparing the physiology of PIAL and PIFL within the same environment enables us to identify physiological mechanisms that underlie species establishment and survival, and how juvenile physiology contributes to their contrasting distributions and their generalist-specialist strategies.
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    Facilitation strength across environmental and beneficiary trait gradients in stream communities
    (Wiley, 2023-08) Tumolo, Benjamin B.; Albertson, Lindsey K.; Daniels, Melinda D.; Cross, Wyatt F.; Sklar, Leonard L.
    Ecosystem engineers modify habitats in ways that facilitate other community members by ameliorating harsh conditions. The strength of such facilitation is predicted to be influenced by both beneficiary traits and abiotic context. One key trait of animals that could control the strength of facilitation is beneficiary body size because it should determine how beneficiaries fit within and exploit stress ameliorating habitat modifications. However, few studies have measured how beneficiary body size relates to facilitation strength along environmental gradients. We examined how the strength of facilitation by net‐spinning caddisflies on invertebrate communities in streams varied along an elevation gradient and based on traits of the invertebrate beneficiaries. We measured whether use of silk retreats as habitat concentrated invertebrate density and biomass compared to surrounding rock surface habitat and whether the use of retreat habitat varied across body sizes of community members along the gradient. We found that retreats substantially concentrated the densities of a diversity of taxa including eight different Orders, and this effect was greatest at high elevations. Caddisfly retreats also concentrated invertebrate biomass more as elevation increased. Body size of invertebrates inhabiting retreats was lower than that of surrounding rock habitats at low elevation sites, however, body size between retreats and rocks converged at higher elevation sites. Additionally, the body size of invertebrates found in retreats varied within and across taxa. Specifically, caddisfly retreats functioned as a potential nursery for taxa with large maximal body sizes. However, the patterns of this taxon‐specific nursery effect were not influenced by elevation unlike the patterns observed based on community‐level body size. Collectively, our results indicate that invertebrates use retreats in earlier life stages or when they are smaller in body size independent of life stage. Furthermore, our analysis suggests that facilitation strength intensifies as elevation increases within stream invertebrate communities. Further consideration of how trait variation and environmental gradients interact to determine the strength and direction of biotic interactions will be important as species ranges and environmental conditions continue to shift.
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