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Revegetation of saline–sodic soils is challenging. Over 10 million saline–sodic hectares are intertwined with highly productive soils in the Northern Great Plains, with 3.4 million ha in South Dakota. Establishing salt‐tolerant perennial plants provides soil cover and remediates barren areas. Two perennial salt‐tolerant grass mixes [Mix 1: slender wheatgrass (Elymus trachycaulus [Link] Gould ex Shinners) + beardless wildrye (Leymus triticoides [Buckley] Pilg.); Mix 2: slender wheatgrass + creeping foxtail (Alopercurus arundinaceus Poir.) + western wheatgrass (Pascopyrum smithii [Rydb.] Á. Löve) + ‘AC Saltlander’ green wheatgrass (Elymus hoffmannii K.B. Jensen & K.H. Asay)] were dormant‐planted in 2018 and 2019 along a soil catena with high [electrical conductivity (EC1:1) = 0.39 dS m–l; 72 mg kg–1 Na+], moderate (EC1:1 = 1.64 dS m–l; 343 mg kg–1 Na+), and low (EC1:1 = 3.87 dS m–l; 1,680 mg kg–1 Na+) productivity zones. Vegetative biomass was measured after seeding (2018, 2019) and during growth (2020, 2021), and compared with areas seeded to maize (Zea mays L.) and a nonplanted area. Biomass varied with year and productivity zone. Except in 2018, grasses had greater biomass in the moderate and low productivity zones than maize. The sodium content of grass biomass in 2020 and 2021 was 10× greater in the low than in the high and moderate productive zones (0.25 vs. 0.02%, respectively) but could be suitable for livestock feed. By 2021, grass biomass was similar for both mixes in all zones, and the grasses spread into nonplanted areas. Core Ideas Saline–sodic areas of the NGP are expanding and areas have poor row crop growth. Remediation with chemical amendments and drainage has often been ineffective. Phytoremediation is needed to restore vegetation, function, and help improve soil health. In terms of biomass, AC Saltlander and slender wheatgrass were the most productive species. Mixes of perennials rather than single species provided species diversity and function.

Increasing atmospheric [CO₂] and temperature are expected to affect the productivity, species composition, biogeochemistry, and therefore the quantity and quality of forage available to herbivores in rangeland ecosystems. Both elevated CO₂ (eCO₂) and warming affect plant tissue chemistry through multiple direct and indirect pathways, such that the cumulative outcomes of these effects are difficult to predict. Here, we report on a 7-yr study examining effects of CO₂ enrichment (to 600 ppm) and infrared warming (+1.5°C day/3°C night) under realistic field conditions on forage quality and quantity in a semiarid, mixedgrass prairie. For the three dominant forage grasses, warming effects on in vitro dry matter digestibility (IVDMD) and tissue [N] were detected only in certain years, varied from negative to positive, and were relatively minor. In contrast, eCO₂ substantially reduced IVDMD (two most abundant grasses) and [N] (all three dominant grass species) in most years, except the two wettest years. Furthermore, eCO₂ reduced IVDMD and [N] independent of warming effects. Reduced IVDMD with eCO₂ was related both to reduced [N] and increased acid detergent fiber (ADF) content of grass tissues. For the six most abundant forage species (representing 96% of total forage production), combined warming and eCO₂ increased forage production by 38% and reduced forage [N] by 13% relative to ambient climate. Although the absolute magnitude of the decline in IVDMD and [N] due to combined warming and eCO₂ may seem small (e.g., from 63.3 to 61.1% IVDMD and 1.25 to 1.04% [N] for Pascopyrum smithii), such shifts could have substantial consequences for the rate at which ruminants gain weight during the primary growing season in the largest remaining rangeland ecosystem in North America. With forage production increases, declining forage quality could potentially be mitigated by adaptively increasing stocking rates, and through management such as prescribed burning, fertilization at low rates, and legume interseeding to enhance forage quality

Nineteen species of agricultural plants, recommended for cultivation in arid conditions of the USA, were tested on the dumps of the Ekibastuz coal mine. The most promising was Atriplex gardneri var. aptera - a North American plant that naturally inhabits the steppe regions of the USA. The group of promising species includes Leymus racemosus, Elymus trachycaulus, and Psathirostachys jnceus. Less promising species for biological reclamation include Calamovilfa longifolia, Bouteloua gracilis, Andropogon gerardii, Leymus arenarius, Pascopyrum smithii sv. Rosana, Pascopyrum smithii sv. Rodan, Elymus lanceolatus, Elytrigia intermedia, Agropyron cristatum, Atriplex canescens, Festuca ovina, and Elimus sibiricus. Lowly promising and unpromising species include Panicum virgatum, Agropyron cristatum x A. desertorum, Schizachyrium scoparium, and Bouteloua curtipendula. These plants are either not frost-resistant or cannot tolerate drought on the dumps.

Contamination, from the explosives, hexahydro-1, 3, 5-trinitro-1, 3, 5-triazine (RDX), and 2, 4, 6-trinitrotoluene (TNT), especially on live-fire training ranges, threatens environmental and human health. Phytoremediation is an approach that could be used to clean-up explosive pollution, but it is hindered by inherently low in planta RDX degradation rates, and the high phytotoxicity of TNT. The bacterial genes, xplA and xplB, confer the ability to degrade RDX in plants, and a bacterial nitroreductase gene nfsI enhances the capacity of plants to withstand and detoxify TNT. While the previous studies have used model plant species to demonstrate the efficacy of this technology, trials using plant species able to thrive in the challenging environments found on military training ranges are now urgently needed. Perennial western wheatgrass (Pascopyrum smithii) is a United States native species that is broadly distributed across North America, well-suited for phytoremediation, and used by the US military to re-vegetate military ranges. Here, we present the first report of the genetic transformation of western wheatgrass. Plant lines transformed with xplA, xplB, and nfsI removed significantly more RDX from hydroponic solutions and retained much lower, or undetectable, levels of RDX in their leaf tissues when compared to wild-type plants. Furthermore, these plants were also more resistant to TNT toxicity, and detoxified more TNT than wild-type plants. This is the first study to engineer a field-applicable grass species capable of both RDX degradation and TNT detoxification. Together, these findings present a promising biotechnological approach to sustainably contain, remove RDX and TNT from training range soil and prevent groundwater contamination.

1. Temporal changes in semi-arid ecosystems can include transitions between alternative stable states, involving thresholds and multiple domains of attraction, but can also include relatively continuous, symmetric and reversible shifts within a single stable state. Conceptual state-and-transition models (STMs) describe both types of ecosystem dynamics by including state transitions (plant community changes difficult-to-reverse without substantial input or effort) and phase shifts (easily reversible community changes) as consequences of management practices and environmental variability. Grazing management is purported to be the primary driver of state transitions in current STMs for North American grasslands, but there is limited empirical evidence from these grasslands showing that grazing can cause difficult-toreverse transitions between alternate stable states. 2. In a northern mixed-grass prairie in Wyoming, USA, we examined plant community responses to (i) long-term (33-year) grazing intensity treatments (none, light, moderate and heavy stocking rates) and (ii) 8 years of light or no grazing in pastures that were grazed heavily for the previous 25 years. 3. Long-term grazing treatments were associated with distinct, but not stable, plant communities. From year 22 to 33, heavier stocking rates decreased cover of dominant C₃ grasses and increased cover of the dominant C₄ grass Bouteloua gracilis. 4. Reversing stocking rates from heavy to light or no grazing resulted in reversal of changes induced by prior heavy stocking for dominant C₃ grasses, but not for B. gracilis. For both groups, rates of change following grazing treatment reversals were consistent with rates of change during the initial years of the experiment (1982-1990). 5. Synthesis and applications. In a semi-arid rangeland with a long evolutionary history of grazing, different long-term grazing intensity treatments caused slow, continuous and directional changes with important management implications, but did not appear to induce alternative stable states. For this and similar ecosystems, quantifying the time-scales and compositional gradients associated with key phase shifts may be more important than identifying thresholds between alternative stable states.

Water repellency of agricultural crop residues may affect the hydrologic balance and increase runoff loss of pesticides by greater wash off from hydrophobic residue. We conducted a laboratory study to measure water repellency and hydrophobicity of 30 major agricultural crops (grass, legume, cereal, oilseed, pulse, and specialty crops). Crop samples were collected in southern Alberta, Canada in 2017 and 2018. Water repellency (WR) of oven‐dried (60°C) and ground (<2 mm) crop residues was measured using the water drop penetration time (WDPT) and molarity of ethanol (MED) tests. Hydrophobicity was evaluated using the ratio of hydrophobic CH– to hydrophilic CO–functional groups using Fourier Transform Infrared (FTIR) spectroscopy. The WDPTs of the 30 agricultural crops ranged from 8.3 to 2438 s, suggesting that crop species influenced WR of the dried and undecomposed residues. Needle‐and‐thread grass (Stipa comata Trin. and Rupr.), blue grama (Bouteloua gracilis [Kunth] Lag. ex Griffiths), and western wheatgrass (Agropyron smithii Rydb.) were the most WR crops based on WDPT. Fababean (Vicia faba), mustard (Sinapis alba L.), and sweet clover (Melilotus officinalis) were the least WR crops. Mean WDPTs were significantly (P ≤ 0.05) greater for grass than the other four crop types by 23 to 44 times. Significant differences in WDPT occurred among crop species within each of the six crop types. A significant positive correlation occurred between WDPT and hydrophobicity (r = 0.54), but not between WDPT and organic carbon. Overall, crop type and species may influence WR of crop residues and could affect the hydrologic balance. Core Ideas Agricultural crop species residue influenced water repellency and hydrophobicity Grass was the most water repellent and hydrophobic crop type A positive correlation occurred between water repellency and hydrophobicity The physical morphology of leaves may contribute to water repellency Water repellency differences also occurred for species within the six crop types

Interseeding annual warm‐season grasses into pastures often increases forage accumulation. Yet, impacts on nutritive value and yields remain unreported. We analyzed forage collected from five Nebraska and Kansas experiments in 2015–2016 (eight environments) for crude protein (CP), neutral detergent fiber (NDF), and in vitro organic matter digestibility (IVOMD) concentrations and yields. Each experiment subjected perennial cool‐season grasses to two harvest frequencies (once at 90 d and twice at 45 and 90 d after interseeding) and four interseeded annual warm‐season grass types–pearl millet [Pennisetum glaucum (L.) R. Br.], sudangrass [Sorghum bicolor (L.) Moench ssp. drummondii (Nees ex Steud) de Wet & Harlan], a sorghum–sudangrass hybrid (S. bicolor × S. bicolor var. sudanense), and an unseeded control. Across environments, 90‐d CP and IVOMD concentrations increased while CP and IVOMD yields decreased in interseeded pastures when harvested twice, indicating presence of nutritive value‐yield tradeoffs. Pastures interseeded with sorghum–sudangrass had greater 90‐d IVOMD concentrations and CP and IVOMD yields when harvested once but only greater 90‐d IVOMD concentrations when harvested twice compared to unseeded pastures. Interseeding sorghum–sudangrass provided an effective strategy to increase CP and IVOMD yields in late summer in humid environments with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.] and in mid‐ and late summer in humid environments with smooth bromegrass (Bromus inermis Leyss.) and semiarid environments with western wheatgrass [Pascopyrum smithii (Rydb.) Á. Löve]. Interseeding annual warm‐season grasses did not consistently increase CP and IVOMD yields in semiarid environments with smooth bromegrass and crested wheatgrass [Agropyrum cristatum (L.)  Gaertn.]. Core Ideas Interseeding annual warm‐season grasses increases forage accumulation in pastures. Increased forage accumulation often comes with nutritive value tradeoffs. Harvesting interseeded pastures once increases late summer forage accumulation. Harvesting twice vs. once tends to increase nutritive value of interseeded pastures.

Climate change and disturbance can alter invasion success of clonal plants by differentially affecting the clonal traits influencing their establishment as young plants. Clonal traits related to the vegetative reproduction of native Pascopyrum smithii and non-native Bromus inermis grass seedlings were evaluated under altered precipitation frequencies and a single grazing event. Pascopyrum smithii maintained similar vegetative reproduction under three simulated precipitation frequencies whereas B. inermis vegetative reproduction declined as precipitation became more intermittent. Vegetative reproduction of the non-native B. inermis was greater than the native P. smithii under all simulated precipitation frequencies except the most intermittent scenario. A single grazing event did not affect either species’ response to intra-annual precipitation variability but did slightly reduce their clonal growth and increase their bud dormancy. In young plants, clonal traits of the invasive grass favored its superior expansion and population growth compared to the native grass except under the most severe climate change scenario. Grassland restoration using native P. smithii seeds would be successful in most years due to its resilient clonal growth in a changing climate. Clonal infrastructure development in young plants is critical to clonal plant establishment and persistence in a changing climate and under disturbed conditions.

Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-native species often possess traits favored by a warmer, drier world. In our study, we assessed plant traits potentially linked to invasion success under elevated temperature and drought, including biomass production, reproductive allocation, arbuscular mycorrhizal (AM) fungal root colonization, and germination of native grasses and non-native invasive grasses. We selected two caespitose warm-season grasses [native (Schizachyrium scoparium) and non-native (Bothriochloa ischaemum)] and two cool-season grasses [native (Pascopyrum smithii) and non-native (Bromus inermis)]. Plant biomass, reproductive effort, and AM fungal colonization were assessed at two temperatures (ambient or elevated) and four levels of soil water-availability; germination was assessed at two temperatures and three levels of soil wateravailability. Non-native warm- and cool-season grasses produced greater vegetative biomass, initiated seed production more frequently, and displayed greater germination when grown under elevated temperature and drought, compared to their paired native counterparts. Percent AM fungal root colonization of the non-native grasses was generally greater than native grasses regardless of soil moisture or elevated temperature. Our results suggest that under warmer and drier conditions non-native grasses will continue to outperform native species, due to greater biomass production, germination capabilities, and colonization by AM fungi.

Aims We examined how restoration affects the structure and function of grasslands belowground by relating changes in the morphology and architecture of root systems of dominant plants to the structure of soil food webs. Methods We measured changes in root traits of dominant plants ( Bouteloua gracilis and Pascopyrum smithii ) and related them to the diversity and feeding structure of soil nematodes across a restoration chronosequence in a mixed-grass prairie in Grasslands National Park, Saskatchewan, Canada. Results Root architecture and morphology of dominant grasses changed with restoration, and soil food webs in recently restored prairies centred around resources provided by roots. In contrast, food webs in a native prairie centred around the decomposition of soil organic matter and plant litter. Conclusions Our study demonstrates that changes in root traits following restoration can cascade through soil foodwebs, altering the function of restored prairies. Our study also highlights that the diversity and structure of soil nematodes can reflect changes in root traits of dominant plants. However, traits that generalize the whole root system may be insufficient to explain the causal relationship between root feeding nematodes and their resources.