College of Letters & Science
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The College of Letters and Science, the largest center for learning, teaching and research at Montana State University, offers students an excellent liberal arts and sciences education in nearly 50 majors, 25 minors and over 25 graduate degrees within the four areas of the humanities, natural sciences, mathematics and social sciences.
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Item Insights into the indigenous-managed landscape in southeast Australia during the Holocene(Springer Science and Business Media LLC, 2023-04) Adesanya Adeleye, Matthew; Graeme Haberle, Simon; Hopf, Felicitas; Harris, Stephen; McWethy, David BurchUnderstanding the long-term interactions between people and the ecosystem in which they live is vital for informing present-day ecosystem management plans. The use of pollen data for palaeoecological reconstructions is often limited by the low taxonomic resolution of pollen, which often reduces the detail of reconstructions of human influence on past vegetation. This is true for Australia where Myrtaceae, particularly Eucalyptus species, dominate the landscape, but their pollen is difficult to differentiate. We present a pollen record with high taxonomic resolution of Myrtaceae pollen from the Bass Strait area of southeast Australia, focusing on the period of major human occupation there during the Late Glacial transition. These results were compared to records of hydrology, fire, sediment deposition, herbivore abundance and human occupation. We found that Indigenous burning practices promoted open, subgenus Monocalyptus Eucalyptus woodland at the expense of dense subgenus Symphomyrtus Eucalyptus forest. Previous studies have shown the need for management of the vegetation of southeast Australia guided by Indigenous people, to promote ecosystem resilience and reduce the risk of wildfires. Our results reveal that in addition to reducing wildfires, cultural burning by Indigenous people has the potential to promote the diversity of ecosystems and habitats.Item Increased whitebark pine (Pinus albicaulis) growth and defense under a warmer and regionally drier climate(Frontiers Media SA, 2023-03) Kichas, Nickolas E.; Pederson, Gregory T.; Hood, Sharon M.; Everett, Richard G.; McWethy, David B.Introduction: Tree defense characteristics play a crucial role in modulating conifer bark beetle interactions, and there is a growing body of literature investigating factors mediating tree growth and resin-based defenses in conifers. A subset of studies have looked at relationships between tree growth, resin duct morphology and climate; however, these studies are almost exclusively from lower-elevation, moisture limited systems. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood. Methods: In this study, we: (1) evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability and (2) determined if tree growth and resin duct morphology of whitebark pine, a high-elevation conifer of management concern, is constrained by climate and/or regional drought conditions. Results: We found that high-elevation whitebark pine trees growing in an energy-limited system experienced increased growth and defense under warmer and regionally drier conditions, with climate variables explaining a substantive proportion of variation (∼20–31%) in tree diameter growth and resin duct anatomy. Discussion: Our results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high-elevation environments; however, this relationship may change in the future with prolonged warming conditions.Item Assessing changes in global fire regimes(Springer Science and Business Media LLC, 2024-02) Sara Sayedi, Sayedeh et al.; McWethy, DavidBackground. The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results. Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion. The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Item PEARLS: Discovery of Point-source Features within Galaxies in the North Ecliptic Pole Time Domain Field(American Astronomical Society, 2024-10) Ortiz III, Rafael et al.; Gim, Hansung B.The first public 0.9–4.4 μm NIRCam images of the North Ecliptic Pole Time Domain Field uncovered galaxies displaying point-source features in their cores as seen in the longer-wavelength filters. We visually identified a sample of 66 galaxies (∼1 galaxy arcmin–2) with pointlike cores and have modeled their two-dimensional light profiles with GalFit, identifying 16 galactic nuclei with measurable point-source components. GalFit suggests that the visual sample is a mix of both compact stellar bulge and point-source galaxy cores. This core classification is complemented by spectral energy distribution modeling to infer the sample's active galactic nucleus (AGN) and host-galaxy parameters. For galaxies with measurable point-source components, the median fractional AGN contribution to their 0.1–30.0 μm flux is 0.44, and 14/16 are color-classified AGN. We conclude that near-infrared point-source galaxy cores are signatures of AGN. In addition, we define an automated sample-selection criterion to identify these point-source features. This criterion can be used in other extant and future NIRCam images to streamline the search for galaxies with unresolved IR-luminous AGN. The James Webb Space Telescope's superb angular resolution and sensitivity at infrared wavelengths are resurrecting the morphological identification of AGN.Item A 2000-year record of fecal biomarkers reveals past herbivore presence and impacts in a catchment in northern Yellowstone National Park, USA(Public Library of Science, 2024-10) Wendt, John A .F.; Argiriadis, Elena; Whitlock, Cathy; Bortolini, Mara; Battistel, Dario; McWethy, David B.Molecular biomarkers preserved in lake sediments are increasingly used to develop records of past organism occurrence. When linked with traditional paleoecological methods, analysis of molecular biomarkers can yield new insights into the roles of herbivores and other animals in long-term ecosystem dynamics. We sought to determine whether fecal steroids in lake sediments could be used to reconstruct past ungulate use and dominant taxa in a small catchment in northern Yellowstone National Park. To do so, we characterized the fecal steroid profiles of a selection of North American ungulates historically present in the Yellowstone region (bison, elk, moose, mule deer, and pronghorn) and compared them with those of sediments from a small lake in the Yellowstone Northern Range. Analysis of a set of fecal steroids from herbivore dung (Δ5-sterols, 5α-stanols, 5β-stanols, epi5β-stanols, stanones, and bile acids) differentiated moose, pronghorn, and mule deer, whereas bison and elk were partially differentiated. Our results show that bison and/or elk were the primary ungulates in the watershed over the past c. 2300 years. Fecal steroid influxes reached historically unprecedented levels during the early and middle 20th century, possibly indicating high local use by ungulates. Comparison of fecal steroid influxes with pollen and diatom data suggests that elevated ungulate presence may have contributed to decreased forage taxa (Poaceae, Artemisia, and Salix), relative to long-term averages, and possibly increased lake production. Our results reflect past change within a single watershed, and extending this approach to a network of sites could provide much-needed information on past herbivore communities, use, and environmental influences in Yellowstone National Park and elsewhere.Item Spatiotemporal analysis of wildfires and their relationship with climate and land use in the Gran Chaco and Pantanal ecoregions(Elsevier BV, 2024-12) Vidal-Riveros, Cristina; Currey, Bryce; McWethy, David B.; Ngo Bieng, Marie Ange; Souza-Alonso, PabloThe Gran Chaco and Pantanal ecoregions are the largest remaining dry forest areas in South America. Supporting diverse savanna, woodland and wetland ecosystems, these ecoregions are experiencing rapid changes in land use and fire occurrence with implications for ecosystem integrity. Our study characterizes the spatiotemporal patterns of wildfires in the Gran Chaco and Pantanal, and then examines the relationship between patterns of fire occurrence and climatic and anthropogenic drivers. We evaluated fire data of the last two decades (2001-2020) using the MODIS Collection 6.1 and the Global Fire Atlas products. Results of the fire pattern characterization were then used to model the probability of fire occurrence across each ecoregion (Random Forest, Generalized Linear Model, and Generalized Additive Model). Our results indicated that most of the total burned area belonged to the Humid Chaco, while the largest individual burned areas were mainly observed in the Pantanal. Fires primarily occurred during the dry season, with the majority of burned areas recorded during this period. Findings from the three modelling approaches consistently illustrated the spatial distribution of fire occurrence, depicting a declining probability of fire occurrence from East to West. All models underscored the importance of three variables to predict fire occurrence: temperature, livestock abundance and forest cover. Fire occurrence increased with increasing maximum temperatures and livestock presence and decreased with tree cover. This research helps to clarify the potential consequences of changes in land use, rainfall regime and temperature, and uncontrolled burning practices on the current fire activity in the Gran Chaco and Pantanal ecoregions. Understanding the spatiotemporal patterns of fire occurrence and their relationship with climatic, environmental and anthropogenic drivers can help to design more effective management strategies to mitigate fire impacts and to preserve the ecological integrity of these highly diverse regionsItem Pollinator planting establishment and bee visitation are influenced by seeding rate and post-seeding management(Wiley, 2024-05) Perkins, Jacquelyn A.; Walters, Jenna; Rowe, Logan; Gedlinske, Lauren; Anderson, Elisabeth; Wang, Sichao; Isaacs, RufusPerennial wildflower plantings are commonly used to support pollinators and other beneficial insects, but their establishment can be costly, and few studies have directly compared the effectiveness of different management strategies for wildflower establishment. To determine the relative importance of pre-seeding weed control, seed density, and post-seeding management on seed mix establishment, we developed a multifactorial field experiment in a grass-dominated weed community. Pre-seeding management treatments (mowing, herbicide, or soybean cover crops) did not affect the stem density of sown plants, or the percent of ground covered by sown plants. However, the percent of ground covered by weeds was significantly influenced by pre-seeding treatments, with infrequent mowing resulting in significantly less weedy ground cover than the herbicide or soybean pre-seeding treatments. Plots with a higher seeding rate had a significantly greater density of sown wildflower species and a higher percent cover of these species after 3 years. Plots that received no post-seeding management had higher stem density, a greater percent ground cover of sown forbs, and higher species richness compared to those that were intensively managed (mow or mow + herbicide). The total number of bee visits (honey bees, bumble bees, and other wild bees) increased with higher forb species richness, higher ground cover of sown forbs, and higher sown species richness. Doubling the density of seeds resulted in a 24.3% increase in the number of wild bees observed. When establishing wildflower habitat for pollinators, investment in ground preparation and seeding density has the greatest impact on sown species establishment.Item Seasonal Variability of Water Quality for Human Consumption in the Tilacancha Conduction System, Amazonas, Peru(Technoscience Publications, 2024-06) Veneros, Jaris; Cuchca Ramos, Llandercita; Goñas, Malluri; Morales, Eli; Auquiñivín-Silva, Erick; Oliva, Manuel; García, LigiaThis study evaluated the seasonal variability of water quality in the Tilacancha River, the water source that supplies Chachapoyas, and the rural communities of Levanto and San Isidro del Maino of Perú. Eighteen physical, chemical, and microbiological water parameters were evaluated at five sampling points in two seasons (rainy and dry). To determine water quality, the results obtained for the parameters evaluated were compared with the Maximum Permissible Limits (MPL) established in the Regulation on Water Quality for Human Consumption (DS Nº 031-2010-SA), approved by the Environmental Health Directorate of the Ministry of Health. In addition, a Pearson correlation was performed to estimate the correlation between the variables evaluated. The results showed that microbiological parameters exceeded the MPLs in both periods evaluated, such as the case of total coliforms (44 MPN.100 mL-1), fecal coliforms (25 MPN.100 mL-1), and E. coli (5.45 MPN.100 mL-1), these microbiological parameters reported a positive correlation with turbidity, temperature, total dissolved solids, and flow rate. In addition, aluminum (Al) and manganese (Mn) exceeded the MPL in the rainy (0.26 mg Al.L-1) and dry (1.41 mg.Mn-1.L-1) seasons, respectively. The results indicated that the water of the Tilacancha River is not suitable for human consumption. Therefore, it must be treated in drinking water treatment plants to be used as drinking water.Item Environmental warming increases the importance of high‐turnover energy channels in stream food webs(Wiley, 2024-05) Junker, James R.; Cross, Wyatt F.; Hood, James M.; Benstead, Jonathan P.; Huryn, Alexander D.; Nelson, Daniel; Ólafsson, Jón S.; Gíslason, Gísli MárWarming temperatures are altering communities and trophic networks across Earth's ecosystems. While the overall influence of warming on food webs is often context-dependent, increasing temperatures are predicted to change communities in two fundamental ways: (1) by reducing average body size and (2) by increasing individual metabolic rates. These warming-induced changes have the potential to influence the distribution of food web fluxes, food web stability, and the relative importance of deterministic and stochastic ecological processes shaping community assembly. Here, we quantified patterns and the relative distribution of organic matter fluxes through stream food webs spanning a broad natural temperature gradient (5–27°C). We then related these patterns to species and community trait distributions of mean body size and population biomass turnover (P:B) within and across streams. We predicted that (1) communities in warmer streams would exhibit smaller body size and higher P:B and (2) organic matter fluxes within warmer communities would increasingly skew toward smaller, higher P:B populations. Across the temperature gradient, warmer communities were characterized by smaller body size (~9% per °C) and higher P:B (~7% faster turnover per °C) populations on average. Additionally, organic matter fluxes within warmer streams were increasingly skewed toward higher P:B populations, demonstrating that warming can restructure organic matter fluxes in both an absolute and relative sense. With warming, the relative distribution of organic matter fluxes was decreasingly likely to arise through the random sorting of species, suggesting stronger selection for traits driving high turnover with increasing temperature. Our study suggests that a warming world will favor energy fluxes through “smaller and faster” populations, and that these changes may be more predictable than previously thought.Item Metabolomic Profiles and Pathways in Osteoarthritic Human Cartilage: A Comparative Analysis with Healthy Cartilage(MDPI AG, 2024-03) Wellhaven, Hope D.; Welfley, Avery H.; Brahmachary, Priyanka; Bergstrom, Annika R.; Houske, Eden; Glimm, Matthew; Bothner, Brian; Hahn, Alyssa K.; June, Ronald K.Osteoarthritis (OA) is a chronic joint disease with heterogenous metabolic pathology. To gain insight into OA-related metabolism, metabolite extracts from healthy (n = 11) and end-stage osteoarthritic cartilage (n = 35) were analyzed using liquid chromatography–mass spectrometry metabolomic profiling. Specific metabolites and metabolic pathways, including lipid and amino acid pathways, were differentially regulated in osteoarthritis-derived and healthy cartilage. The detected alterations in amino acids and lipids highlighted key differences in bioenergetic resources, matrix homeostasis, and mitochondrial alterations in OA-derived cartilage compared to healthy cartilage. Moreover, the metabolomic profiles of osteoarthritic cartilage separated into four distinct endotypes, highlighting the heterogenous nature of OA metabolism and the diverse landscape within the joint in patients. The results of this study demonstrate that human cartilage has distinct metabolomic profiles in healthy and end-stage OA patients. By taking a comprehensive approach to assess metabolic differences between healthy and osteoarthritic cartilage and within osteoarthritic cartilage alone, several metabolic pathways with distinct regulation patterns were detected. Additional investigation may lead to the identification of metabolites that may serve as valuable indicators of disease status or potential therapeutic targets.