Annual Grass Research Articles

Ecotypic differentiation of leaf silicon concentration in the grass Brachypodium hybridum along a rainfall gradient

Ecotypic differentiation, reflected in substantial trait differences across populations, has been observed in various plant species distributed across aridity gradients. Nevertheless, ecotypic differentiation in leaf silicon concentration, known to alleviate drought stress in plants, remained hardly explored. Here, we provide a systematic test for ecotypic differentiation in leaf silicon concentration along two aridity gradients in the grass Brachypodium hybridum in Israel. Seed material was sampled in 15 sites along a macroclimatic aridity gradient (89 – 926 mm mean annual rainfall) and from corresponding north (moister) and south (more arid) exposed slopes (microclimatic gradient) at similar altitudes (mean north: 381 m a.s.l., mean south: 385 m a.s.l.). Plants were subsequently grown under common conditions and their leaf silicon concentration was analysed. Leaf silicon concentration increased with increasing aridity across the macroclimatic gradient, but did not differ between north and south slopes. The higher leaf silicon concentrations under more arid conditions can enhance the ability of plants to cope with more arid conditions by two mutually not exclusive mechanisms: (i) withstanding drought by reducing water loss and increasing water uptake or (ii) escaping drought by facilitating fast growth. Our study highlights that leaf silicon concentration contributes to ecotypic differentiation in annual grasses along macroclimatic aridity gradients.

Weed management in organic dryland wheat production in the Pacific Northwest

AbstractGrowth in demand for organic small grains has increased interest in producing certified organic crops in the semiarid US Pacific Northwest. The region is well‐suited for small grain production, and there is a strong market for organic food products on the US West Coast. However, many growers encounter significant and persistent challenges with weed management, particularly management of perennial weeds such as Canada thistle [Cirsium arvense (L.) Scop.] and field bindweed (Convolvulus arvensis L.), but also common winter and spring annual grass weeds including cheatgrass (Bromus tectorum L.) and wild oat (Avena fatua L.). Coupled with the need to minimize soil disturbance, weed management can become nearly intractable and production limiting. From 2004 to 2024, several short and intermediate studies have been conducted to assess weed control tactics and crop rotation effects on weed management. Lessons learned include incorporating alfalfa (Medicago sativa L.) and spring barley (Hordeum vulgare L.) into rotations for suppression of field bindweed, or alfalfa and winter triticale (x Triticosecale Wittmack) for suppression of Canada thistle. Optimization of cultural inputs, particularly seeding rate, are critical for each crop in rotation. Animal integration and new crops such as quinoa (Chenopodium quinoa Willd.) are alternatives to conventional crops and potentially profitable. Incorporation of precision mechanical and chemical systems is feasible in narrow‐row cereals, and when combined with crop rotation, it could reduce or eliminate the need for repeated transitions back to convention production for organic growers.

Optimization of Productivity of Fodder Crops with Green Conveyor System in the Context of Climate Instability in the North Kazakhstan Region

One of the main challenges in modern animal husbandry in North Kazakhstan is ensuring an uninterrupted supply of sufficient fodder crops. This research, conducted from 2019 to 2023, aimed to develop strategies for cultivating environmentally sustainable fodder crops capable of providing a stable fodder crop base under the changing climatic conditions of the North Kazakhstan region. The studies included analysis of air temperature and precipitation data as well as monitoring of fodder grass mixtures within a green fodder conveyor system. Different sowing dates for fodder crops and mixtures were selected for the development of the conveyor system. The range of experimental variants included fodder crops and their mixtures from various botanical families. The experiment involved both perennial (alfalfa and festulolium) and annual (corn, pea, sunflower, Sudan grass, oats, and rapeseed) crops. The highest green mass yields were achieved by the following variants: fodder crops of corn + pea—74.40 c/ha; mixtures of annual legume–grass crops in the pea + oats variant of the first sowing date—43.64 c/ha; Sudan grass + pea—45.72 c/ha; mixtures of perennial grasses in the second utilization term of alfalfa + festulolium—64.9 c/ha; and rapeseed sown at the first sowing date—46.61 c/ha. In terms of crude and digestible protein content, the best among the annual grass variants was the mixture of Sudan grass and pea (crude protein—33.59 g/kg, digestible protein—24.5 g/kg), and the best among the perennials was the variant of the first utilization term (crude protein—50.42 g/kg, digestible protein—38.2 g/kg). Regarding metabolizable energy content, the annual crop variant of corn + pea had a yield of 1.92 MJ/kg, and in the perennial variant, the mixture of alfalfa and festulolium in the first utilization term had a yield of 2.68 MJ/kg. Such an approach to creating green fodder conveyors can be crucial for developing effective strategies for adapting agriculture to climate change, including the selection of promising fodder crops and optimization of their placement. The results obtained can contribute to enhancing the productivity and sustainability of agricultural production in the North Kazakhstan region.

Effect of Crimson® NG Adjuvant on Glyphosate Efficacy in Corn

There is limited published data on the impact of the addition of Crimson® NG to glyphosate on weed control efficacy in corn under Ontario environmental conditions. Four field experiments were conducted at the University of Guelph, Ridgetown Campus, Ridgetown, Ontario during 2022 and 2023 with two water sources to evaluate weed control with glyphosate alone and in combination with Crimson® NG. Glyphosate was applied at rates of 900, 1029, or 1221 g ae ha-1, with and without Crimson® NG at 1.0 and 2.5% v/v, using water with 56 ppm (Ridgetown) and 1600 ppm (Plattsville) hardness. Results showed that glyphosate at 900 g ae ha-1 controlled velvetleaf, Powell amaranth, common ragweed, common lambsquarters, barnyardgrass, and giant foxtail 97-100%, independent of water hardness. Neither increased glyphosate rates nor the addition of Crimson® NG significantly improved weed control. No corn injury was observed with all herbicide/adjuvant treatments evaluated. These findings confirm that glyphosate at 900 g ae ha-1 is highly effective for the control of common annual grass and broadleaf weeds. Weed control efficacy with glyphosate was not influenced by water source and there was no improvement in weed control efficacy from increasing the rate of glyphosate or from the addition of Crimson® NG.

Mycology of Fodder Plants in Different Areas of Azerbaijan the Results of Studies Devoted to the Evaluation

Both cultivated and wild fodder plants are the main group of plants necessary for the development of animal husbandry. Although it is impossible to give a specific number about the number of species of fodder plants in Azerbaijan, there is no doubt that their number of species is expressed in hundreds. Thus, the number of species of annual grasses in the CIS includes up to 1000 species. As it is known, some species mentioned above as fodder plants also carry other qualities. For example, corn, sunflower, wormwood, three-leaf clover, etc. plants are also medicinal plants and are used as diuretics, pain relievers, etc. in folk medicine. It is widely used as a tool with properties. At the same time, due to these properties, these plants have become the subject of various aspects (botanical, pharmacological, mycological, etc.) studies, and this situation is still ongoing.

Estimating vegetation and litter biomass fractions in rangelands using structure-from-motion and LiDAR datasets from unmanned aerial vehicles

ContextThe invasion of annual grasses in western U.S. rangelands promotes high litter accumulation throughout the landscape that perpetuates a grass-fire cycle threatening biodiversity.ObjectivesTo provide novel evidence on the potential of fine spatial and structural resolution remote sensing data derived from Unmanned Aerial Vehicles (UAVs) to separately estimate the biomass of vegetation and litter fractions in sagebrush ecosystems.MethodsWe calculated several plot-level metrics with ecological relevance and representative of the biomass fraction distribution by strata from UAV Light Detection and Ranging (LiDAR) and Structure-from-Motion (SfM) datasets and regressed those predictors against vegetation, litter, and total biomass fractions harvested in the field. We also tested a hybrid approach in which we used digital terrain models (DTMs) computed from UAV LiDAR data to height-normalize SfM-derived point clouds (UAV SfM-LiDAR).ResultsThe metrics derived from UAV LiDAR data had the highest predictive ability in terms of total (R2 = 0.74) and litter (R2 = 0.59) biomass, while those from the UAV SfM-LiDAR provided the highest predictive performance for vegetation biomass (R2 = 0.77 versus R2 = 0.72 for UAV LiDAR). In turn, SfM and SfM-LiDAR point clouds indicated a pronounced decrease in the estimation performance of litter and total biomass.ConclusionsOur results demonstrate that high-density UAV LiDAR datasets are essential for consistently estimating all biomass fractions through more accurate characterization of (i) the vertical structure of the plant community beneath top-of-canopy surface and (ii) the terrain microtopography through thick and dense litter layers than achieved with SfM-derived products.

Phenology forecasting models for detection and management of invasive annual grasses

AbstractNon‐native annual grasses can dramatically alter fire frequency and reduce forage quality and biodiversity in the ecosystems they invade. Effective management techniques are needed to reduce these undesirable invasive species and maintain ecosystem services. Well‐timed management strategies, such as grazing, that are applied when invasive grasses are active prior to native plants can control invasive species spread and reduce their impact; however, anticipating the timing of key phenological stages that are susceptible to management over vast landscapes is difficult, as the phenology of these species can vary greatly over time and space. To address this challenge, we created range‐wide phenology forecasts for two problematic invasive annual grasses: cheatgrass (Bromus tectorum), and red brome (Bromus rubens). We tested a suite of 18 mechanistic phenology models using observations from monitoring experiments, volunteer science, herbarium records, timelapse camera imagery, and downscaled gridded climate data to identify the models that best predicted the dates of flowering and senescence of the two invasive grass species. We found that the timing of flowering and senescence of cheatgrass and red brome were best predicted by photothermal time models that had been adjusted for topography using gridded continuous heat‐insolation load index values. Phenology forecasts based on these models can help managers make decisions about when to schedule management actions such as grazing to reduce undesirable invasive grasses and promote forage production, quality, and biodiversity in grasslands; to predict the timing of greatest fire risk after annual grasses dry out; and to select remote sensing imagery to accurately map invasive grasses across topographic and latitudinal gradients. These phenology models also have the potential to be operationalized for within‐season or within‐year decision support.

Invasive annual grasses destabilize plant communities in a northern mixed‐grass prairie

AbstractTemporal community stability, here defined as temporal mean divided by temporal SD, plays an important role in predicting certain ecosystem services. However, temporal stability can change with invasion, with greater abundances of invasive species potentially having greater impacts on native community stability. The exact consequences of invasion for temporal stability are unclear and, in part, depend on the particular metric of stability measured. In rangeland ecosystems, predicable forage is important for livestock production but can be threatened by invasion. Therefore, using an observational field study conducted over three years in Wyoming, we assessed which metrics of plant community stability were altered by invasion and whether those effects were mediated by two environmental variables (light and soil moisture). Bromus arvensis and Bromus tectorum are two invasive annual weeds found across US rangelands, including the northern mixed‐grass prairies of Wyoming. We established plots along natural invasion blocks of B. arvensis and B. tectorum abundance and collected plant species composition data over three growing seasons. We tested associations between seven different metrics of plant community stability and invasion by B. arvensis and B. tectorum. We found that species turnover increases with invasion by both species, while stability of forb (both brome species), C4 grass (B. arvensis only), and C3 grass (B. tectorum only) cover decreases with invasion. All metrics of stability associated with invasion supported the hypothesis of a destabilizing effect of invasion on the native plant community. Further, we found that light and soil moisture did mediate some associations between stability and invasion. Overall, our results align with previous work suggesting that invasive annual bromes can lead to decreased native plant stability, which has important implications for forage production and, thus, food security.

Multiple plant-community traits improve predictions of later-stage outcomes of restoration drill seedings: Implications for metrics of success

Success of ecological restoration is often only knowable if treatments meet criteria defined by biotic thresholds, but analytical frameworks to determine metrics of success and their underlying thresholds are needed. Early indicators of longer-term recovery trajectories are particularly critical where re-treatments may be required, such as in harsh climates or where repeated disturbances or invasive pressures prevail. We developed a framework for identifying which biotic traits would provide the best initial indication of longer-term target restoration goals and applied the framework to restoration drill-seedings of deep-rooted perennial bunchgrasses (DRPBGs) used to rehabilitate and restore semiarid rangelands threatened by exotic annual grasses (EAGs, e.g. cheatgrass) and the recurrent wildfire that EAGs cause. Initial traits measured included cover, basal diameter, height, and density (#plants/area) of DRPBGs and cover of EAGs and Sandberg bluegrass (Poa secunda, POSE, a disturbance-adapted perennial). The longer-term target objective was ≥25 % DRPBG cover and ≤13 % EAG cover by the 5th year following drill-seedings. Measurements were made on 112 plots spanning 113,000 ha in sagebrush steppe on the Soda wildfire scar, in the Northern Great Basin, USA. Traits of DRPBGs tended to be uncorrelated with one another, thus each was informative in describing vegetation condition. Where DRPBG cover was initially >17 %, it tended to become >25 % by the 5th-year post-seeding. In plots that overcame an initial risk of not meeting the target objective (i.e. <17 % initial DRPBG cover), DRPBG tended be large DRPBGs (>22.8 cm height) and plots also had >7 % cover of POSE. Additional “sets” of initial vegetation traits were also predictive of longer-term restoration success or failure. Restoration drill-seeding of DRPBGs is a key but varied-outcome tool for breaking the exotic grass-fire cycle, and, contrary to a conventional tendency to rely on a limited number of mean traits such as % cover, a suite of biotic traits appears necessary to monitor to reliably know if trials are likely to yield success.

Using transcriptome sequencing (RNA-Seq) to screen genes involved in β-glucan biosynthesis and accumulation during oat seed development.

Oat (Avena sativa L.) is an annual grass that has a high nutritional value and therapeutic benefits. β-glucan is one of the most important nutrients in oats. In this study, we investigated two oat varieties with significant differences in β-glucan content (high β-glucan oat varieties BY and low β-glucan content oat variety DY) during different filling stages. We also studied the transcriptome sequencing of seeds at different filling stages. β-glucan accumulation was highest at days 6-16 in the filling stage. Differentially expressed genes (DEGs) were selected from the dataset of transcriptome sequencing. Among them, three metabolic pathways were closely related to the biosynthesis of β-glucan by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, including xyloglucan:xyloglucosyl transferase activity, starch and sucrose metabolism, and photosynthesis. By analyzing the expression patterns of DEGs, we identified one CslF2 gene and 32 transcription factors. Five modules were thought to be positively correlated with β-glucan accumulation by weighted gene co-expression network analysis (WGCNA). Moreover, the expression levels of candidate genes obtained from the transcriptome sequencing were further validated by quantitative real-time PCR (RT-qPCR) analysis. Our study provides a novel way to identify the regulatory mechanism of β-glucan synthesis and accumulation in oat seeds and offers a possible pathway for the genetic engineering of oat breeding for higher-quality seeds.

Living on the edge: identifying demographic bottlenecks in an isolated sage‐grouse population

The greater sage‐grouse (Centrocercus urophasianus: hereafter sage‐grouse) population in Modoc County California is geographically isolated and contains a single lek (from 56 leks in the 1940s), despite significant efforts to increase the population through translocations and habitat improvement. Repeated wildfire within the landscape has led to an increase in invasive annual grasses and a decrease in sagebrush (Artemisia sp.) cover in important nesting and brood‐rearing habitat. We estimated survival for adult females, nests, and chicks and assessed biotic characteristics that may influence these survival estimates to identify factors that may be limiting population growth. We monitored 37 female sage‐grouse marked with GPS PTTS, 39 nests, and 8 broods for 3 years (2019–2021). We measured vegetation characteristics for nests at the microsite and landscape scale to evaluate effects on daily nest survival (DNS). We used survival rates from all life stages to parameterize matrix models and estimate population growth rate. Mean nest success over 3 years was 29% (95% CI: 17.1–44.8) across a 29‐day incubation period and DNS declined as the proportion of both medusahead Taeniatherum caput‐medusae and Japanese brome Bromus japonicus around the nest increased. Across all three years, mean chick survival across a 54‐day period was 44% (95% CI: 0.9–72.3) and mean annual survival for adult females was 29% (95% CI: 17.8–43.7). Our estimated vital rates were 45–55% lower than distribution‐wide estimates and the projected population growth rate was strongly declining (0.411, 95% CI: 0.30–0.52). Our results suggested recent cover changes associated with wildfire on the study area may have had a detrimental effect on this population across all life stages, and if attention is not given to preventing the transition from sagebrush communities into invasive grasslands, this population and others in degraded landscapes may not persist.

Genome-Wide Identification and Characterization of MYB Transcription Factors in Sudan Grass under Drought Stress.

Sudan grass (Sorghum sudanense S.) is a warm-season annual grass with high yield, rich nutritional value, good regeneration, and tolerance to biotic and abiotic stresses. However, prolonged drought affects the yield and quality of Sudan grass. As one of the largest families of multifunctional transcription factors in plants, MYB is widely involved in regulating plant growth and development, hormonal signaling, and stress responses at the gene transcription level. However, the regulatory role of MYB genes has not been well characterized in Sudan grass under abiotic stress. In this study, 113 MYB genes were identified in the Sudan grass genome and categorized into three groups by phylogenetic analysis. The promoter regions of SsMYB genes contain different cis-regulatory elements, which are involved in developmental, hormonal, and stress responses, and may be closely related to their diverse regulatory functions. In addition, collinearity analysis showed that the expansion of the SsMYB gene family occurred mainly through segmental duplications. Under drought conditions, SsMYB genes showed diverse expression patterns, which varied at different time points. Interaction networks of 74 SsMYB genes were predicted based on motif binding sites, expression correlations, and protein interactions. Heterologous expression showed that SsMYB8, SsMYB15, and SsMYB64 all significantly enhanced the drought tolerance of yeast cells. Meanwhile, the subcellular localization of all three genes is in the nucleus. Overall, this study provides new insights into the evolution and function of MYB genes and provides valuable candidate genes for breeding efforts in Sudan grass.

Modeling cheatgrass distribution, abundance, and response to climate change as a function of soil microclimate.

Exotic annual grass invasions in water-limited systems cause degradation of native plant and animal communities and increased fire risk. The life history of invasive annual grasses allows for high sensitivity to interannual variability in weather. Current distribution and abundance models derived from remote sensing, however, provide only a coarse understanding of how species respond to weather, making it difficult to anticipate how climate change will affect vulnerability to invasion. Here, we derived germination covariates (rate sums) from mechanistic germination and soil microclimate models to quantify the favorability of soil microclimate for cheatgrass (Bromus tectorum L.) establishment and growth across 30 years at 2662 sites across the sagebrush steppe system in the western United States. Our approach, using four bioclimatic covariates alone, predicted cheatgrass distribution with accuracy comparable to previous models fit using many years of remotely-sensed imagery. Accuracy metrics from our out-of-sample testing dataset indicate that our model predicted distribution well (72% overall accuracy) but explained patterns of abundance poorly (R2 = 0.22). Climatic suitability for cheatgrass presence depended on both spatial (mean) and temporal (annual anomaly) variation of fall and spring rate sums. Sites that on average have warm and wet fall soils and warm and wet spring soils (high rate sums during these periods) were predicted to have a high abundance of cheatgrass. Interannual variation in fall soil conditions had a greater impact on cheatgrass presence and abundance than spring conditions. Our model predicts that climate change has already affected cheatgrass distribution with suitable microclimatic conditions expanding 10%-17% from 1989 to 2019 across all aspects at low- to mid-elevation sites, while high- elevation sites (>2100 m) remain unfavorable for cheatgrass due to cold spring and fall soils.

485 Impact of annual and perennial forage systems on forage biomass and quality, steer performance, and enteric methane emissions

Abstract Beef producers require forage options that provide adequate yield and high nutritive value, optimizing the production and sustainability of grazing operations. Few multiple year studies within Canada compare novel perennial and annual grass legume blends under grazing. This study evaluated the effects of perennial and annual forage systems on forage biomass and quality, grazing animal performance, and enteric emissions. Forage treatments included 1) AC Success hybrid bromegrass (Bromus riparius Rehm. × Bromus inermis Leyss.) + PS3006 alfalfa (Medicago sativa L.; HBG-ALF), 2) AC Armada meadow bromegrass (Bromus riparius Rehm.) + AAC Mountainview sainfoin (Onobrychis viciifolia Scop.; MBG-SF), 3) AC Hazlet fall rye (Secale cereale L.) + Frosty berseem clover (Trifolium alexandrinum L.; FR-CLOV), and 4) Winfred forage brassica (Brassica oleracea L.× Brassica rapa L.) + Gorilla forage brassica (Brassica napus L.) + 4010 pea (Pisum sativum L.) + CDC Austenson barley (Hordeum vulgare L.; BR-PE-BRAS). Yearling beef steers [n = 120, body weight (BW) = 397 ± 10 kg] were randomly allocated to 1 of 4 replicated (n = 3) forage systems for an average of 65 d grazing period amongst the 12 paddocks. Dry matter yield (DMY) was similar (P = 0.33) between BR-PE-BRAS (2,170 kg/ha) and HBG-ALF (1938 kg/ha), which were greater (P &amp;lt; 0.0001) than both MBG-SF (1030 kg/ha) and FR-CLOV (700 kg/ha) systems. Total digestible nutrient content (TDN) of FR-CLOV (63.6%) and BR-PEA-BRASS (62.0%) was greater (P &amp;lt; 0.0001) than both MBG-SF (51.7%) and HBG-ALF (49.3%) forages. Crude protein (CP) was greatest in FR-CLOV (15.2% P = 0.0012) intermediate in BR-PEA-BRASS (10.0%) and HBG-ALF (8.5%), and least in MBG-SF (6.6%). Steer performance was greatest when grazing HBG-ALF (87 kg/ha) paddocks, which was similar (P = 0.31) to FR-CLOV (62 kg/ha) and similar (P = 0.10) MBG-SF (51 kg/ha), but greater (P = 0.01) than BAR-PEA-BRASS (26 kg/ha). Enteric methane concentration from steers was the least when grazing BR-PE-BRAS (19.7g/kg DMI), followed by FR-CLOV (22.4g/kg DMI), MBG-SF (23.4g/kg DMI) and finally HBG-ALF (28.1g/kg DMI). In summary, BR-PE-BRAS and HBG-ALF forage systems provided the greatest DMY, while steer average daily gain (ADG) grazing HBG-ALF forage outperformed steers on BR-PE-BRAS paddocks. Forage energy and protein was greater in annual forage systems FR-CLOV and BR-PE-BRAS, compared with perennial forage systems. Enteric methane levels were the lowest in the steers grazing BR-PE-BRAS forage.

Propagation and growth of Paspalum carajasense: a threatened Amazonian canga grass

Paspalum carajasense, an endemic and endangered annual grass found in the canga ecosystems of Serra dos Carajás, Brazil, lacks adequate propagation and conservation data. We assessed its germination and growth in various substrates to support conservation and mineland rehabilitation purposes. Seed germination tests involved soaking in water for 24 h and two KNO3 concentrations (2.5% and 5.0%). Seedlings were grown for 100 days on canga topsoil, mining waste substrate, and a commercial organic substrate. Mining substrates received 0%, 50%, and 100% of Carajás revegetation nutrients due to low fertility. Paspalum carajasense can be sexually propagated and pregermination treatments did not increase germination rates (14%). Seedlings were able to grow in all substrates and showed zero mortality. Plants in fertilized substrates showed similar growth to that on canga topsoil, with significant changes in root and leaf traits. In organic substrates, plants accumulated a larger amount of biomass and produced substantial amounts of seeds with higher germination rates, supporting the feasibility of ex situ cultivation. Therefore, our study provides essential information for the propagation and ex situ cultivation of a rare species of canga ecosystems and highlights the possibility of reconciling the conservation of P. carajasense with mineland rehabilitation.

Impact of Different Herbicidal Treatments on Hybrid Maize: A Review

Maize (Zea mays L.) is an important cereal crop grown in the world. The living factors (insects, pests, weeds) and non-living factors (drought, salinity, heat stress) affects the yield of maize; among which weeds are considered as most destructive in decreasing the maize crop yield. Weeds negatively affect the grain yield of maize and increase the production cost of farmers. Various herbicides are used to control weeds in maize including atrazine, tembotrione etc. Atrazine is a pre-emergence herbicide used to control weeds. It is a selective herbicide used to control broad-leaved weeds and annual grasses. Tembotrione is a PoE (Post-emergence) broad spectrum herbicide used to control broad-leaved and grassy weeds in maize. This herbicide effectively reduces the density and dry weight of most of the weeds present in maize crop. Tembotrione gives lower weed index and higher weed control efficiency, when applied at 150 g ha−1 + surfactant and 125 g ha−1 + surfactant at 20 DAS. These herbicide shows no phytotoxicity effect on the crops. They are totally safe for weed control and enhance the productivity and profatibilty of the crop.

Triazine herbicide prometryn alters epoxide hydrolase activity and increases cytochrome P450 metabolites in murine livers via lipidomic profiling

Oxylipins are a group of bioactive fatty acid metabolites generated via enzymatic oxygenation. They are notably involved in inflammation, pain, vascular tone, hemostasis, thrombosis, immunity, and coagulation. Oxylipins have become the focus of therapeutic intervention since they are implicated in many conditions, such as nonalcoholic fatty liver disease, cardiovascular disease, and aging. The liver plays a crucial role in lipid metabolism and distribution throughout the organism. Long-term exposure to pesticides is suspected to contribute to hepatic carcinogenesis via notable disruption of lipid metabolism. Prometryn is a methylthio-s-triazine herbicide used to control the growth of annual broadleaf and grass weeds in many cultivated plants. The amounts of prometryn documented in the environment, mainly waters, soil and plants used for human and domestic consumption are significantly high. Previous research revealed that prometryn decreased liver development during zebrafish embryogenesis. To understand the mechanisms by which prometryn could induce hepatotoxicity, the effect of prometryn (185 mg/kg every 48 h for seven days) was investigated on hepatic and plasma oxylipin levels in mice. Using an unbiased LC–MS/MS-based lipidomics approach, prometryn was found to alter oxylipins metabolites that are mainly derived from cytochrome P450 (CYP) and lipoxygenase (LOX) in both mice liver and plasma. Lipidomic analysis revealed that the hepatotoxic effects of prometryn are associated with increased epoxide hydrolase (EH) products, increased sEH and mEH enzymatic activities, and induction of oxidative stress. Furthermore, 9-HODE and 13-HODE levels were significantly increased in prometryn treated mice liver, suggesting increased levels of oxidation products. Together, these results support that sEH may be an important component of pesticide-induced liver toxicity.

Long-term legacy of phytoremediation on plant succession and soil microbial communities in petroleum-contaminated sub-Arctic soils

Abstract. Phytoremediation can be a cost-effective method of restoring contaminated soils using plants and associated microorganisms. Most studies follow the impacts of phytoremediation solely across the treatment period and have not explored long-term ecological effects. In 1995, a phytoremediation study was initiated near Fairbanks, Alaska, to determine how the introduction of annual grasses and/or fertilizer would influence degradation of petroleum hydrocarbons (PHCs). After 1 year, grass and/or fertilizer-treated soils showed greater decreases in PHC concentrations compared to untreated plots. The site was then left for 15 years with no active site management. In 2011, we re-examined the site to explore the legacy of phytoremediation on contaminant disappearance, as well as on plant and soil microbial ecology. We found that the recruited vegetation and the current bulk soil microbial community structure and functioning were all heavily influenced by initial phytoremediation treatment. The number of diesel-degrading microorganisms (DDMs) was positively correlated with the percentage cover of vegetation at the site, which was influenced by initial treatment. Even 15 years later, the initial use of fertilizer had significant effects on microbial biomass, community structure, and activity. We conclude that phytoremediation treatment has long-term, legacy effects on the plant community, which, in turn, impact microbial community structure and functioning. It is therefore important to consider phytoremediation strategies that not only influence site remediation rates in the short-term but also prime the site for the restoration of vegetation over the long-term.

The LTAR Grazing Land Common Experiment at the Great Basin.

The Long-Term Agroecosystem Research Network (LTAR), through its Common Experiment (CE) framework, contrasts prevailing and alternative agricultural practices for efficacy and sustainability within the indicator domains of environment, productivity, economics, and society. Invasive species, wildfire, and climate change are principal threats to Great Basin agroecosystems. Prescribed grazing may be an effective tool for restoring lands degraded by these disturbances. At the Great Basin (GB) LTAR site headquartered in Boise, ID, our contribution to the CE contrasts a prevailing (PRV), cattle grazing practice of fixed moderate stocking and duration with an alternative (ALT), prescribed grazing practice called high-intensity low-frequency (HILF) grazing where stocking and duration are tailored to suppress invasive annual grass competition with native or desirable plant species and thus promote recovery of rangelands degraded by annual grass invasion and recurrent wildfire. Preliminary results indicate cheatgrass density and fuel height have been reduced in ALT-treated paddocks compared to PRV paddocks. Since its inception in 2014, our GB CE has been a research co-production effort among ranchers, public land managers, and researchers. Future directions for this research will center on expanding the experiment to multiple study areas to better address the scope of the annual grass/wildfire problem. We expect this research will lead to effective and sustainable grazing practices for restoring >41 million hectares of degraded rangelands in the Great Basin and other areas of the western United States.

Disentangling drivers of annual grass invasion: Abiotic susceptibility vs. fire-induced conversion to cheatgrass dominance in the sagebrush biome

Invasive annual grasses are often facilitated by fire, yet they can become ecologically dominant in susceptible locations even in the absence of fire. We used an extensive vegetation plot database to model susceptibility to the invasive annual grass cheatgrass (Bromus tectorum L.) in the sagebrush biome as a function of climate and soil water availability variables. We built random forest models predicting cheatgrass presence or dominance (>15 % relative cover) under unburned (37,219 plots) and burned conditions (6340 plots). We mapped predicted probability of cheatgrass presence and dominance, conditional on burning. We combined predicted susceptibility with burn probability to quantify the 10-year total risk of cheatgrass dominance. Finally, we identified portions of the landscape (1) at risk of fire-induced conversion to cheatgrass dominance, (2) consistently susceptible to cheatgrass dominance, or (3) consistently resistant to cheatgrass dominance. At the scale of the sagebrush biome, we found that abiotic susceptibility to cheatgrass dominance drives total risk, regardless of fire. At local scales (i.e., individual 30 m pixels), burning increased the probability of cheatgrass dominance by a median of 14 %. Threshold-based analyses indicate that 10–31 % of the sagebrush biome was at risk of fire-induced dominance, with 55 % exhibiting abiotic resistance and 5 % exhibiting abiotic susceptibility to dominance regardless of fire. Burn probability was higher in areas predicted to be susceptible to dominance, illustrating how cheatgrass invasion can cause ecosystem conversions that are then sustained by grass-fire cycles. Disentangling the influence of abiotic conditions and fire contributes to our understanding of the mechanisms driving invasion dynamics, and modeling the probability of dominance can help anticipate where ecological transformations are at risk of occurring. Our approach can facilitate the prioritization of management actions in the sagebrush biome and be used as a framework for modeling invasion risk in other disturbance-prone ecosystems.