Scholarly Work - Land Resources & Environmental Sciences

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Cool semi-arid cropping treatments alter Avena fatua's performance and competitive intensity
(Wiley, 2024-03) Larson, Christian D.; Wong, Mei Long; Carr, Patrick M.; Seipel, Timothy
Introduction. Multiple herbicide-resistant Avena fatua L. is common in the Northern Great Plains, USA. This prevalence and the ecological impacts of tillage in this semi-arid agricultural region have created a need for integrated weed management, with a specific knowledge gap in using annual forage crops and targeted grazing for A. fatua suppression. Materials and Methods. A 2-year study in central Montana, USA, assessed A. fatua performance (aboveground biomass, stem density and seed production) in response to seven cropping treatments: (1–4) tall and short spring wheat cultivars crossed with high and low seeding rates, (5–6) annual forage mixture terminated using sheep grazing and simulated haying and (7) tilled fallow. Avena fatua's competitive intensity in wheat and the annual forage mixture was determined using a relative competition intensity index. Results. Avena fatua performance was lowest in tilled fallow, although stem density and seed production did not differ from the grazed annual forage treatment. Response variables were lower in the forage treatments compared with the wheat treatments, and there were no differences among the four fully crossed wheat treatments. Separate analysis of the wheat treatments indicated lower A. fatua biomass and stem density when wheat was sown at a higher rate with no impact of wheat height. Avena fatua competition impacted wheat and forage crops but was more intense for wheat. Conclusion. Tillage was the most effective treatment at reducing A. fatua performance, but annual forage mixtures can be used to resist A. fatua invasion (reduced A. fatua competitive intensity) and limit its performance after invasion. We conclude that crop sequences that combine higher cash crop (wheat) seeding rates and competitive annual forage mixtures may be utilized to manage A. fatua invaded systems, thereby reducing heavy reliance on tillage in the US Northern Great Plains and similar semi-arid regions.
Thermal profiles of Cicindelidia haemorrhagica (Coleoptera: Cicindelidae) activity in hot springs in Yellowstone National Park
(Entomological Society of America, 2024-07) Bowley, John L.; Heveran, Chelsea; Weaver, David K.; Adams, Braymond; Rohwer, Monica; Willemssens, Kelly; Oberg, Erik; Higley, Leon G.; Peterson, Robert K. D.
Tillage and crop sequences for organic Cirsium arvense management in the Northern Great Plains
(Wiley, 2024-06) Larson, Christian D.; Hettinger, Kara; Carr, Patrick M.; Miller, Perry R.; Volkman, McKenna; Chichinsky, Daniel; Seipel, Tim
The perennial rhizomatous weed Cirsium arvense (L.) Scop. is difficult to manage on semiarid organic farms. Our objective was to quantify the impact of eight 4-year crop sequences crossed with standard- and reduced-tillage on C. arvense occurrence (presence/absence), stem density, and aboveground biomass at two semiarid sites in Montana. The sequences represented a range of crop competition from high (multiple years of perennial forage [alfalfa, Medicago sativa L.]) to low (2 years of continuous fallow), with intermediate sequences consisting of different annual species. Final-year spring wheat (Triticum aestivum L. emend. Thell.) was planted in all sequences to determine impacts on subsequent cash crop production. Through time, alfalfa and double fallow sequences reduced C. arvense density and biomass where it was established, although its invasion into new areas increased in the double fallow. Final-year C. arvense occurrence and stem density were lower in the alfalfa sequence compared with six and four annual crop sequences, respectively (p < 0.05). Final year C. arvense biomass was higher at one site than the other, although not in the double fallow sequence. Wheat grain yields differed in response to crop sequences at the two sites: at one site, grain yield was lowest in the alfalfa sequence, especially when standard-tillage was used, while yields were highest in the alfalfa and double fallow sequences at the other site. Using perennial forages in semiarid organic systems can be effective for managing C. arvense, but subsequent cash crop yield may be depressed.
Landscape context affects patch habitat contributions to biodiversity in agroecosystems
(Wiley, 2024-06) Duff, Hannah; Debinski, Diane; Maxwell, Bruce D.
Effective conservation schemes are needed to advance the dual objectives of biodiversity conservation and agronomic production in agricultural landscapes. Understanding how plant and arthropod taxa respond to both local habitat patch characteristics and landscape complexity is crucial for planning effective agri-environment schemes. This study investigated the relative effects of local variables (plant and insect diversity ≤100 m from patch habitat center) and landscape variables (landscape composition and configuration metrics ≤5 km from patch habitat center) on the diversity of plants and arthropods within noncrop habitat patches (1) at different spatial extents ranging from 0.1 to 5 km, while (2) quantifying differential effects of local and landscape variables on particular components of diversity (i.e., species richness and abundance), and accounting for (3) particular components of landscape extent (0.1-, 0.5-, 1-, 2-, and 5-km radii) and complexity (i.e., landscape composition and configuration). Landscape variables were significantly correlated with local plant and arthropod species richness and abundance at all spatial extents. Biodiversity responses to landscape variables were largely scale-dependent, as pairwise comparisons were significantly different between all spatial extents except between 1- and 2-km extents, and correlations were lowest at the 5-km extent. Partial R2 values for predicting local biodiversity were highest when both local and landscape variables were included as predictors of species richness and abundance, increasing from 0.163 to 0.469 when landscape variables were included, underscoring the importance of considering both local and landscape effects on local diversity. Landscape configuration variables accounted for more variation in plant and arthropod species richness than composition variables. However, models performed best when composition and configuration were considered together rather than alone, suggesting that both components of landscape complexity should be considered for identifying and managing conservation areas in crop fields. Existing conservation schemes that incentivize farmers to create or conserve seminatural patch habitat within crop fields may be more effective when combined with landscape-scale designs that enhance landscape complexity across the Northern Great Plains. Local conservation efforts should be coordinated with landscape-level efforts to ultimately enhance biodiversity and desired ecosystem service outcomes across agricultural landscapes.
On innovation and entomology: a path to renewed relevance and the future
(Oxford University Press, 2024-06) Peterson, Robert K. D.
In 2019, I was honored to be president of the Entomological Society of America (ESA). In choosing my theme for 2019 a year or so before that, I wrestled with whether to stick with what had been on my email signature line for a few years, Advocate Entomology! or change it to what I was obsessing over at the time: Innovation. I stuck with Advocate Entomology! but it quickly became apparent that advocacy and innovation were inextricably intertwined. During 2019, we devoted several initiatives to innovation, and the basis for focusing on innovation was the empowerment of all entomologists. Even more so now than 5 years ago because of advances in generative artificial intelligence, every entomologist has the ability not only to think about solutions to problems but also to create tangible products that come from their thoughts. Arguably more important, these products can be shared with billions of people in microseconds. Those people can then give feedback and share their own ideas, and the cycle can continue.
McMurdo Dry Valley lake edge ‘moats’: the ecological intersection between terrestrial and aquatic polar desert habitats
(Cambridge University Press, 2024-04) Stone, Michael S.; Devlin, Shawn P.; Hawes, Ian; Welch, Kathleen; Gooseff, Michael N.; Takacs-Vesbach, Cristina; Morgan-Kiss, Rachael; Adams, Bryon J.; Barrett, J. E.; Priscu, John C.; Doran, Peter T.
Aquatic ecosystems - lakes, ponds and streams - are hotspots of biodiversity in the cold and arid environment of Continental Antarctica. Environmental change is expected to increasingly alter Antarctic aquatic ecosystems and modify the physical characteristics and interactions within the habitats that they support. Here, we describe physical and biological features of the peripheral ‘moat’ of a closed-basin Antarctic lake. These moats mediate connectivity amongst streams, lake and soils. We highlight the cyclical moat transition from a frozen winter state to an active open-water summer system, through refreeze as winter returns. Summer melting begins at the lakebed, initially creating an ice-constrained lens of liquid water in November, which swiftly progresses upwards, creating open water in December. Conversely, freezing progresses slowly from the water surface downwards, with water at 1 m bottom depth remaining liquid until May. Moats support productive, diverse benthic communities that are taxonomically distinct from those under the adjacent permanent lake ice. We show how ion ratios suggest that summer exchange occurs amongst moats, streams, soils and sub-ice lake water, perhaps facilitated by within-moat density-driven convection. Moats occupy a small but dynamic area of lake habitat, are disproportionately affected by recent lake-level rises and may thus be particularly vulnerable to hydrological change.
Roadside disturbance promotes plant communities with arbuscular mycorrhizal associations in mountain regions worldwide
(Wiley, 2024-04) Clavel, Jan et al.
We assessed the impact of road disturbances on the dominant mycorrhizal types in ecosystems at the global level and how this mechanism can potentially lead to lasting plant community changes. We used a database of coordinated plant community surveys following mountain roads from 894 plots in 11 mountain regions across the globe in combination with an existing database of mycorrhizal–plant associations in order to approximate the relative abundance of mycorrhizal types in natural and disturbed environments. Our findings show that roadside disturbance promotes the cover of plants associated with arbuscular mycorrhizal (AM) fungi. This effect is especially strong in colder mountain environments and in mountain regions where plant communities are dominated by ectomycorrhizal (EcM) or ericoid-mycorrhizal (ErM) associations. Furthermore, non-native plant species, which we confirmed to be mostly AM plants, are more successful in environments dominated by AM associations. These biogeographical patterns suggest that changes in mycorrhizal types could be a crucial factor in the worldwide impact of anthropogenic disturbances on mountain ecosystems. Indeed, roadsides foster AM-dominated systems, where AM-fungi might aid AM-associated plant species while potentially reducing the biotic resistance against invasive non-native species, often also associated with AM networks. Restoration efforts in mountain ecosystems will have to contend with changes in the fundamental make-up of EcM- and ErM plant communities induced by roadside disturbance.
Are Adult Mosquito Control Products (Adulticides) Harmful? A Review of the Potential Human Health Impacts from Exposure to Naled and Dichlorvos (DDVP)
(MDPI AG, 2023-12) Mendoza, Daniel L.; Peterson, Robert K. D.; Bonds, Jane A. S.; White, Gregory S.; Faraji, Ary
We performed a thorough systematic review of published literature to determine potential links between human health impacts and naled, a registered adult mosquito control product (adulticide), and its major degradate, dichlorvos (DDVP). A search query was performed on 8 September 2023, capturing all articles published up to that date on the Scopus and PubMed databases. Inclusion criteria were the presence of either pesticide and a measured or modeled human health outcome or risk. The search string resulted in 382 articles; however, 354 articles were excluded, resulting in only 28 articles that met the inclusion criteria. The studies that directly relate to aerosolized ultra-low volume (ULV) mosquito control applications did not report any associated deleterious human health outcomes. Results from the reviewed papers displayed no negative health effects or led to inconclusive results. No studies showed adverse health effects from aerial ULV applications for mosquito management. Our findings are congruent with the United States Environmental Protection Agency and Centers for Disease Control and Prevention recommendations that aerial applications of naled, following label parameters, do not pose an adverse risk exposure to humans, wildlife, and the environment.
Carbon and phosphorus exchange rates in arbuscular mycorrhizas depend on environmental context and differ among co-occurring plants
(Wiley, 2024-01) Lekberg, Ylva; Jansa, Jan; McLeod, Morgan; DuPre, Mary Ellyn; Holben, William E.; Johnson, David; Koide, Roger T.; Shaw, Alanna; Zabinski, Catherine; Aldrich-Wolfe, Laura
Phosphorus (P) for carbon (C) exchange is the pivotal function of arbuscular mycorrhiza (AM), but how this exchange varies with soil P availability and among co-occurring plants in complex communities is still largely unknown. We collected intact plant communities in two regions differing c. 10-fold in labile inorganic P. After a 2-month glasshouse incubation, we measured 32P transfer from AM fungi (AMF) to shoots and 13C transfer from shoots to AMF using an AMF specific fatty acid. AMF communities were assessed using molecular methods. AMF delivered a larger proportion of total shoot P in communities from high-P soils despite similar 13C allocation to AMF in roots and soil. Within communities, 13C concentration in AMF was consistently higher in grass than in blanketflower (Gaillardia aristata Pursh) roots, that is P appeared more costly for grasses. This coincided with differences in AMF taxa composition and a trend of more vesicles (storage structures) but fewer arbuscules (exchange structures) in grass roots. Additionally, 32P-for-13C exchange ratios increased with soil P for blanketflower but not grasses. Contrary to predictions, AMF transferred proportionally more P to plants in communities from high-P soils. However, the 32P for-13C exchange differed among co-occurring plants, suggesting differential regulation of the AM symbiosis.
Oxic methane production from methylphosphonate in a large oligotrophic lake: limitation by substrate and organic carbon supply
(American Society for Microbiology, 2023-11) Peoples, Logan M.; Dore, John E.; Bilbrey, Evan M.; Vick-Majors, Trista J.; Ranieri, John R.; Evans, Kate A.; Ross, Abigail M.; Devlin, Shawn P.; Church, Matthew J.
While methane is typically produced under anoxic conditions, methane supersaturation in the presence of oxygen has been observed in both marine and fresh waters. The biological cleavage of methylphosphonate (MPn), which releases both phosphate and methane, is one pathway that may contribute to this paradox. Here, we explore the genomic and functional potential for oxic methane production (OMP) via MPn in Flathead Lake, a large oligotrophic freshwater lake in northwest Montana. Time series and depth profile measurements show that epilimnetic methane was persistently supersaturated despite high oxygen levels, suggesting a possible in situ oxic source. Metagenomic sequencing indicated that 10% of microorganisms in the lake, many of which are related to the Burkholderiales (Betaproteobacteria) and Actinomycetota, have the genomic capacity to cleave MPn. We experimentally demonstrated that these organisms produce methane stoichiometrically with MPn consumption across multiple years. However, methane was only produced at appreciable rates in the presence of MPn when a labile organic carbon source was added, suggesting that this process may be limited by both MPn and labile carbon supply. Members of the genera Acidovorax , Rhodoferax , and Allorhizobium , organisms which make up less than 1% of Flathead Lake communities, consistently responded to MPn addition. We demonstrate that the genomic and physiological potential for MPn use exists among diverse, resident members of Flathead Lake and could contribute to OMP in freshwater lakes when substrates are available. IMPORTANCE Methane is an important greenhouse gas that is typically produced under anoxic conditions. We show that methane is supersaturated in a large oligotrophic lake despite the presence of oxygen. Metagenomic sequencing indicates that diverse, widespread microorganisms may contribute to the oxic production of methane through the cleavage of methylphosphonate. We experimentally demonstrate that these organisms, especially members of the genus Acidovorax , can produce methane through this process. However, appreciable rates of methane production only occurred when both methylphosphonate and labile sources of carbon were added, indicating that this process may be limited to specific niches and may not be completely responsible for methane concentrations in Flathead Lake. This work adds to our understanding of methane dynamics by describing the organisms and the rates at which they can produce methane through an oxic pathway in a representative oligotrophic lake.
Growth of Coal Mining Operations in the Elk River Valley (Canada) Linked to Increasing Solute Transport of Se, NO3–, and SO42– into the Transboundary Koocanusa Reservoir (USA–Canada)
(American Chemical Society, 2023-11) Storb, Meryl B.; Bussell, Ashley M.; Caldwell Eldridge, Sara L.; Hirsch, Robert M.; Schmidt, Travis S.
Koocanusa Reservoir (KOC) is a waterbody that spans the United States (U.S.) and Canadian border. Increasing concentrations of total selenium (Se), nitrate + nitrite (NO3–, nitrite is insignificant or not present), and sulfate (SO42–) in KOC and downstream in the Kootenai River (Kootenay River in Canada) are tied to expanding coal mining operations in the Elk River Watershed, Canada. Using a paired watershed approach, trends in flow-normalized concentrations and loads were evaluated for Se, NO3–, and SO42– for the two largest tributaries, the Kootenay and Elk Rivers, Canada. Increases in concentration (SO42– 120%, Se 581%, NO3– 784%) and load (SO42– 129%, Se 443%, NO3– 697%) in the Elk River (1979–2022 for NO3–, 1984–2022 for Se and SO42–) are among the largest documented increases in the primary literature, while only a small magnitude increase in SO42– (7.7% concentration) and decreases in Se (−10%) and NO3– (−8.5%) were observed in the Kootenay River. Between 2009 and 2019, the Elk River contributed, on average, 29% of the combined flow, 95% of the Se, 76% of the NO3–, and 38% of the SO42– entering the reservoir from these two major tributaries. The largest increase in solute concentrations occurred during baseflows, indicating a change in solute transport and delivery dynamics in the Elk River Watershed, which may be attributable to altered landscapes from coal mining operations including altered groundwater flow paths and increased chemical weathering in waste rock dumps. More recently there is evidence of surface water treatment operations providing some reduction in concentrations during low flow times of year; however, these appear to have a limited effect on annual loads entering KOC. These findings imply that current mine water treatment, which is focused on surface waters, may not sufficiently reduce the influence of mine-waste-derived solutes in the Elk River to allow constituent concentrations in KOC to meet U.S. water-quality standards.
Chelostoma Latreille, 1809 (Hymenoptera: Megachilidae) of Montana, including first records of the introduced bees Chelostoma campanularum (Kirby, 1802) and Chelostoma rapunculi (Lepeletier, 1841)
(Pacific Coast Entomological Society, 2023-05) Delphia, Caey M.
The megachilid bees of the genus Chelostoma Latreille, 1809 in Montana, U.S.A., are reviewed. Two Palearctic species, Chelostoma (Foveosmia) campanularum (Kirby, 1802) and Chelostoma (Gyrodromella) rapunculi (Lepeletier, 1841), are reported for the first time from Montana. The Montana specimens represent a range expansion from southeastern Michigan for C. campanularum and from northeastern Illinois for C. rapunculi. These collections appear to represent an established local population for C. campanularum with specimens from multiple dates, years, and locations in Bozeman, Montana; specimens of C. rapunculi have only been found in one location and year. The habitat, distribution, and potential ecological impacts of establishment of these two non-native species in Montana are discussed. An identification key to the Chelostoma of Montana is provided.
Nitrogen fixation among pea and lentil varieties in the Northern Great Plains
(Wiley, 2023-08) Baber, Kaleb; Jones, Clain; McPhee, Kevin; Miller, Perry R.; Lamb, Peggy
Pulse crops, including lentil (Lens culinaris Medik.) and pea (Pisum sativum L.), can improve the sustainability of Northern Great Plains cropping systems, largely through biological N fixation. Greater N fixation amounts can help producers to increase yield while decreasing N fertilizer inputs for the following crop. There may be potential to breed greater N-fixing pulse varieties, yet little is known about varietal differences in N fixation. Nitrogen fixation of pea and lentil varieties was quantified at two sites in Montana from 2019 to 2021 using an N difference approach and the 15N natural abundance method. Riveland and CDC Richlea were frequently high N-fixing lentil varieties, both fixing ca. 130 kg N ha−1 in the site-year with the most favorable growing conditions. No pea variety had consistently greater N fixation than others, despite N fixation ranging from 88 to 135 kg N ha−1 in one site-year among varieties. Nitrogen fixation by lentil had an inverse relationship with days to flowering but was not correlated with days to maturity. Nitrogen fixation by pea was positively correlated with days to maturity but was not correlated with days to flowering. Breeding lentil and pea for high N fixation by selecting high N-fixing varieties is likely difficult, as varieties performed differently under variable environmental conditions. Breeding efforts based on traits, such as days to flowering, could be more successful. There were more positive correlations between N fixation parameters and seed yield for pea than for lentil, suggesting that breeding for greater yields could increase N fixation for pea but not lentil.
Lentil nitrogen fixation response to fertilizer and inoculant in the northern Great Plains
(Wiley, 2023-08) Baber, Kaleb; Jones, Clain; Miller, Perry; Lamb, Peggy; Atencio, Sydney
Lentil (Lens culinaris Medikus) production in the semiarid northern Great Plains of the United States has increased dramatically over the past two decades. Lentil in rotation provides agroecosystem benefits of more efficient water use, pest cycle disruption, and biological nitrogen (N) fixation. Increasing N fixation could alleviate soil acidification and groundwater impairment, decrease N fertilizer costs, and increase lentil seed yield. Despite widespread farmer adoption of lentil in the region, little is known about the benefits of fertilizer or inoculant type on N fixation. The aim of this study was to determine how nutrients (potassium (K), sulfur (S), and foliar-applied micronutrients) and rhizobial inoculant types (seed-coat powder and granular) influence N fixation of lentil. The study was conducted at two field sites in Montana from 2019 to 2021. Fixed N amounts were calculated using both an N difference approach and 15N natural abundance method. N fixation was highly responsive to climatic conditions and soil characteristics. The amount of N fixed did not respond to K fertilization, likely because soil test K levels were sufficient. In a moderately dry year at a site with low soil sulfate-S, fertilizer application of 5.6 kg S ha−1 increased N fixed by 40%. Inoculated lentil fixed more N than uninoculated lentil in two site-years, but there were no differences in N fixed between inoculant types. Inoculation response was not related to field cropping histories with legumes. The study shows that S fertilization and rhizobial inoculation have potential to increase lentil N fixation amounts in the northern Great Plains.
Retrospective use of integrative taxonomy in classical biological control: The unintentional introduction of the weevil Rhinusa dieckmanni to North America
(Elsevier BV, 2023-08) Toševski, Ivo; Sing, Sharlene E.; Caldara, Roberto; Weaver, David K.; Jović, Jelena; Krstić, Oliver; Hinz, Hariet L.
A seed-feeding weevil introduced to North America (NA) as a biological control agent of the invasive toadflax Linaria dalmatica (L.) Mill., identified then as Gymnetron antirrhini “Dalmatian host race” and subsequently confirmed as established, was revealed through our study to be a separate species, i.e., Rhinusa dieckmanni (Behne) (Coleoptera: Curculionidae). This weevil species was presumed to be endemic in its native range, with a distribution restricted to Mount Rila in southwestern Bulgaria. We conducted a comprehensive study of seed-feeding weevils associated with L. dalmatica, L. dalmatica ssp. macedonica (Griseb.) D.A. Sutton, L. genistifolia (L.) Mill., and L. grandiflora Desf. across a broad geographic area of their native range. Those results revealed that all four host plants were used by R. dieckmanni and thus the native geographic range of the species is wider than expected, encompassing the Balkans and the Anatolian Plateau. Our observations suggest that phenotypes of this weevil are highly variable and dependent on the seed capsule size of the Linaria host population. The haplotype network based on mitochondrial COII, 16S genes, and nuclear EF 1-α gene genealogy confirmed the conspecific nature of geographically distant weevil populations, that is, R. dieckmanni phenotypes utilizing L. genistifolia, L. dalmatica, and L. grandiflora for larval development. Specimens collected from L. dalmatica in the northwestern USA shared the same haplotypes as samples from L. dalmatica ssp. macedonica in southwestern North Macedonia, supporting the known introduction history of the North American population. Females from these populations have relatively short rostrums, which may limit their reproductive success on North American invasive L. dalmatica with larger seed capsules.
Pinus contorta Alters Microenvironmental Conditions and Reduces Plant Diversity in Patagonian Ecosystems
(MDPI AG, 2023-02) García, Rafael A.; Fuentes-Lillo, Eduardo; Cavieres, Lohengrin; Cóbar-Carranza, Ana J.; Davis, Kimberley T.; Naour, Matías; Núñez, Martín A.; Maxwell, Bruce D.; Lembrechts, Jonas J.; Pauchard, Aníbal
Pinus contorta is considered one of the most invasive tree species worldwide, generating significant impacts on biodiversity and ecosystems. In several Patagonian ecosystems in southern Chile, it has escaped from plantations established mainly in the 1970s, and is now invading both forests and treeless environments. In this study, we evaluated the impact of the invasion of P. contorta on microenvironmental conditions in Araucaria araucana forest and Patagonian steppe ecosystems, and assessed how these changes related to the richness and abundance of native and non-native plant species. In each ecosystem, 24 plots of 100 m2 were established along a gradient of P. contorta biomass, where 18 environmental variables and the composition of native and non-native vegetation were measured at a local scale. Our results indicated that increased pine biomass was associated with differences in microclimatic conditions (soil and air temperature, photosynthetically active radiation (PAR), and soil moisture) and soil properties (potassium, nitrate, pH, and litter accumulation). These changes were ecosystem dependent, however, as well as associated with the level of invasion. Finally, the reduction in the richness and abundance of native plants was associated with the changes in soil properties (accumulation of leaf litter, pH, and organic matter) as well as in the microclimate (minimum air temperature, PAR) generated by the invasion of P. contorta. Overall, our results confirm that the invasion of P. contorta impacts microenvironmental conditions (i.e., canopy cover, litter accumulation, minimum air temperature, and maximum soil temperature) and reduces native plant diversity. For future restoration plans, more emphasis should be given to how environmental changes can influence the recovery of invaded ecosystems even after the removal of the living pine biomass (i.e., legacy of the invasion).
Impact of Puccinia punctiformis on Cirsium arvense performance in a simulated crop sequence
(Frontiers Media SA, 2023-05) Chichinsky, Daniel; Larson, Christian; Menalled, Fabian D.; Seipe, Tim; Eberly, Jed
Cirsium arvense (Canada thistle) is a perennial weed that causes significant economic losses in agriculture. An extensive rhizomatous root system makes C. arvense difficult to manage, particularly in agricultural systems that use tillage as a primary management tool. There is a need for the development of integrated weed management toolsets that include C. arvense biological controls. Puccinia punctiformis (thistle rust) is an autoecious fungal pathogen that systemically infects C. arvense, with the potential to reduce host vigor over time. The goal of this study was to integrate the P. punctiformis biocontrol with a simulated annual cropping sequence in a greenhouse environment and evaluate C. arvense’s above-and belowground biomass production, and its competitive ability. Repeated P. punctiformis inoculations produced systemically infected C. arvense stems in greenhouse pots over time. Cirsium arvense that was inoculated with P. punctiformis had 1.6 grams/pot (p = 0.0019) less aboveground biomass and 5.6 grams/pot (p< 0.001) less belowground biomass, compared to the non-inoculated (control). Puccinia punctiformis and crop competition interacted additively to lower aboveground (p<0.001) and belowground (p<0.001) C. arvense biomass more than individual use of either the biocontrol or competition alone. The aboveground competition intensity of C. arvense in a mixed crop sequence, relative to non-inoculated C. arvense grown in a monoculture, was moderately impacted by the P. punctiformis biocontrol (p = 0.0987). These results indicate that systemic infection can reduce biomass production and the competitive ability of C. arvense. Overall, P. punctiformis can be integrated into competitive annual cropping sequences with the potential to reduce C. arvense vigor over time.
Long‐term cover crop effects on biomass, soil nitrate, soil water, and wheat
(Wiley, 2023-05) Miller, Perry R.; Jones, Clain A.; Zabinski, Catherine A.; Tallman, Susan M.; Housman, Megan L.; D'Agati, Kristen M.; Holmes, Jeffrey A.
Cover crops during summer fallow have been rarely researched in the semiarid northern Great Plains. This study was conducted during 2012–2019 at four Montana locations and included four functional groups (Brassica family, fibrous-rooted crops, legumes, and tap-rooted crops). Eleven treatments included sole functional groups, a Full Mix, the Full Mix minus each functional group, pea, and chemical fallow. Wheat (Triticum aestivum L.) was grown after each cover crop year with three nitrogen (N) fertilizer rates. Cover crops were terminated with herbicide at first flower stage of pea (Pisum sativum L.) 57 to 66 days after planting. Shoot biomass averaged 2.0 Mg ha−1 over eight site-years representative of dryland farming in Montana. Using equal overall plant densities, treatments with six species averaged 13% greater biomass than two species. Measured at termination to a 0.9-m depth, Fallow held greater soil water than cover crop treatments, with Fallow averaging 57 mm greater than the Full Mix. Soil nitrate averaged 49 kg N ha−1 greater after Fallow than the Full Mix; the Legume treatment averaged 26 kg N ha−1 greater than the Minus Legume treatment. Wheat yield on Fallow averaged 0.85 Mg ha−1 greater than the Full Mix in 5 of 10 site-years, mainly at the driest site-years. The Legume treatment elevated wheat protein over the Minus Legume treatment by an average of 15 g kg−1. Cover crops grown during summer fallow reduced soil nitrate-N, soil water, and wheat yields compared with chemical fallow, especially in the major wheat growing region of north central Montana.
Aerobic methane synthesis and dynamics in a river water environment
(Wiley, 2023-06) Alowaifeer, Abdullah M.; Wang, Qian; Bothner, Brian; Sibert, Ryan J.; Joye, Samantha B.; McDermott, Timothy R.
Reports of aerobic biogenic methane (CH4) have generated new views about CH4 sources in nature. We examine this phenomenon in the free-flowing Yellowstone river wherein CH4 concentrations were tracked as a function of environmental conditions, phototrophic microorganisms (using chlorophyll a, Chl a, as proxy), as well as targeted methylated amines known to be associated with this process. CH4 was positively correlated with temperature and Chl a, although diurnal measurements showed CH4 concentrations were greatest during the night and lowest during maximal solar irradiation. CH4 efflux from the river surface was greater in quiescent edge waters (71–94 μmol m−2 d) than from open flowing current (~ 57 μmol m−2 d). Attempts to increase flux by disturbing the benthic environment in the quiescent water directly below (~ 1.0 m deep) or at varying distances (0–5 m) upstream of the flux chamber failed to increase surface flux. Glycine betaine (GB), dimethylamine and methylamine (MMA) were observed throughout the summer-long study, increasing during a period coinciding with a marked decline in Chl a, suggesting a lytic event led to their release; however, this did not correspond to increased CH4 concentrations. Spiking river water with GB or MMA yielded significantly greater CH4 than nonspiked controls, illustrating the metabolic potential of the river microbiome. In summary, this study provides evidence that: (1) phototrophic microorganisms are involved in CH4 synthesis in a river environment; (2) the river microbiome possesses the metabolic potential to convert methylated amines to CH4; and (3) river CH4 concentrations are dynamic diurnally as well as during the summer active months.
Cowpea extrafloral nectar has potential to provide ecosystem services lost in agricultural intensification and support native parasitoids that suppress the wheat stem sawfly
(Oxford Academic, 2023-05) Cavallini, Laissa; Peterson, Robert K. D.; Weaver, David K.
The native parasitoids Bracon cephi (Gahan) and B. lissogaster Muesebeck (Hymenoptera: Braconidae) reduce populations of Cephus cinctus Norton (Hymenoptera: Cephidae), a native grassland species, and major wheat pest on the Northern Great Plains of North America. Non-host feeding adults of these braconids increase longevity, egg load, and egg volume when provisioned carbohydrate-rich diets. Nutrition from nectar can enhance the success of natural enemies in pest management programs. Cowpea, Vigna unguiculata (L.) Walpers, is a potential cover-crop that could add resilient features to the landscape and has extrafloral nectaries (EFN), easy-access nectar sources for beneficial insects. If more cowpea was grown on the Northern Great Plains, would B. cephi and B. lissogaster benefit from foraging on putatively beneficial EFN? We investigated cowpea inflorescence stalk extrafloral nectars (IS-EFN) and leaf stipel extrafloral nectars (LS-EFN) as potential food sources for these parasitoids. Females were caged on EFN sources on living cowpea plants to assess longevity. Egg load and volume were measured at 2, 5, and 10 days after placement. Bracon cephi survived 10 days on water, 38 days on IS-EFN; B. lissogaster 6 days on water, 28 days on IS-EFN. Bracon lissogaster maintained a constant egg load and volume across treatments while B. cephi produced 2.1-fold more eggs that were 1.6-fold larger on IS-EFN. Y-tube olfactometry indicated adult females were attracted to airstreams containing cowpea volatiles. These results demonstrate that non-native, warm-season cowpea benefits these native parasitoids and may improve conservation biocontrol of C. cinctus.

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