Northern US Research Articles

Expanding wildland-urban interface alters forest structure and landscape context in the northern United States

The wildland-urban interface (WUI), where housing intermingles with wildland vegetation, is the fastest-growing land use type in the United States. Given the ecological and social benefits of forest ecosystems, there is a growing need to more fully understand how such development alters the landscape context and structure of these WUI forests. In a space-for-time analysis we utilized land cover data, forest inventory plots, and housing density data over time to examine differences in forest characteristics of the northern US across three WUI change classes: (a) forest that has been in WUI housing density levels since at least 1990 (old-WUI), (b) forest where development crossed the WUI housing density threshold after 1990 (new-WUI), and (c) forest with little to no housing development (non-WUI). Of the 184 million acres of forest in the study area, 34 million acres (19%) were in old-WUI, 12 million acres (7%) were new-WUI, and 136 million acres (74%) were non-WUI. In general, as areas transitioned from non-WUI to newer WUI to older more established WUI, the forest was associated with decreased spatial integrity, increased forest-developed edges, and lower proportions of forest in the surrounding landscape. Forest in the WUI had greater carbon storage, with greater aboveground biomass, relative stand density, and more live trees per hectare than non-WUI forest, suggesting greater capacity to sequester carbon compared to non-WUI forest. At the same time, WUI forest also had significantly reduced structural diversity compared to non-WUI forest, with fewer saplings, seedlings, and dead trees per hectare. Forest that more recently crossed the WUI housing density threshold appeared to be on a trajectory towards that of old-WUI forest. These differences in forest structure across the northern US suggest reduced capacity for forest regeneration in the WUI and the potential for changes in other ecological functions.

Early spring onset increases carbon uptake more than late fall senescence: modeling future phenological change in a US northern deciduous forest.

In deciduous forests, spring leaf development and fall leaf senescence regulate the timing and duration of photosynthesis and transpiration. Being able to model these dates is therefore critical to accurately representing ecosystem processes in biogeochemical models. Despite this, there has been relatively little effort to improve internal phenology predictions in widely used biogeochemical models. Here, we optimized the phenology algorithms in a regionally developed biogeochemical model (PnET-CN) using phenology data from eight mid-latitude PhenoCam sites in eastern North America. We then performed a sensitivity analysis to determine how the optimization affected future predictions of carbon, water, and nitrogen cycling at Bartlett Experimental Forest, New Hampshire. Compared to the original PnET-CN phenology models, our new spring and fall models resulted in shorter season lengths and more abrupt transitions that were more representative of observations. The new phenology models affected daily estimates and interannual variability of modeled carbon exchange, but they did not have a large influence on the magnitude or long-term trends of annual totals. Under future climate projections, our new phenology models predict larger shifts in season length in the fall (1.1-3.2days decade-1) compared to the spring (0.9-1.5days decade-1). However, for every day the season was longer, spring had twice the effect on annual carbon and water exchange totals compared to the fall. These findings highlight the importance of accurately modeling season length for future projections of carbon and water cycling.

Toward Models of Impact and Recovery of the US Western Grid from Earthquake Events

A Cascadia Subduction Zone (CSZ) earthquake will cause widespread damage to numerous lifelines and infrastructure along the northern US west coast. The goal of the presented research is to provide a bottom up estimate of the impact on and subsequent recovery of a Cascadia Subduction Zone earthquake on the US western grid to supplement and enhance the expert opinion estimates provided to date. The scope is limited to only consideration of shaking damage to utility substation equipment components of a power system model. The analysis utilizes probabilistic models of damage and recovery for substation power system assets, along with graph techniques for modeling connectivity, and Monte Carlo quasi steady state power flow solutions. The results show that a conservative estimate of the initial damage and loss of load is approximately 4000 MW, with a recovery estimate of 230 days.

Carbon footprint of perennial bioenergy crop production receiving various nitrogen fertilization rates

Perennial bioenergy crops can reduce greenhouse gas emissions compared to fossil fuels, but little is known about their C footprints. We evaluated C footprint and C balance of perennial bioenergy crops receiving various N fertilization rates and visually compared them with an annual crop from 2012 to 2014 in the semiarid region of US northern Great Plains. Perennial bioenergy crops were intermediate wheatgrass (Thinopyrum intermedium [Host] Barkworth and Dewey, IW), smooth bromegrass (Bromus inermis L., SB), and switchgrass (Panicum virgatum L., SG), and N fertilization rates were 0, 28, 56, and 84 kg N ha−1. The annual crop was spring wheat (Triticum aestivum L., WH). The CO2 flux increased in the summer when air temperature and precipitation were greater. Cumulative annual CO2 flux was greater for SB and SG than IW in 2012–2013 and greater for SB than IW and SG in 2013–2014. Shoot C increased with increased N fertilization rate and was greater for SG than IW and SB at most N fertilization rates in both years. Root and rhizosphere C varied with N fertilization rates and were lower for SG than IW and SB at 0 kg N ha−1, but greater at 84 kg N ha−1. Carbon balance also varied with N fertilization rates, being lower for SG than IW and SB at 0 kg N ha−1, but greater at other N rates. Cumulative CO2 flux was higher, but shoot, root, and rhizosphere C as well as C balance were lower for WH than perennial bioenergy crops. Because of greater total C input but lower CO2 flux, SG with N fertilization can be C positive, retaining more C in plant residue and soil than other perennial bioenergy crops. Spring wheat remained C negative compared to perennial bioenergy crops, losing more C as CO2 flux than total C input.

Diverse responses of vegetation and fire after pleistocene megaherbivore extinction across the eastern US

Megaherbivores are keystone species whose removal from landscapes can cause cascading ecosystem changes, yet the consequences of Late Quaternary megaherbivore extinctions remain uncertain. This paper tests the Megaherbivory Release Hypothesis (MRH), which posits that the decline and extinction of megaherbivores (body size >1000 kg) during the last deglaciation in eastern North America contributed to the expansion of more palatable hardwood tree taxa, the development of vegetation assemblages with no modern analogue, and increased fuel load and fire activity. Coprophilous fungal spores in lake sediment records are used as proxies for megaherbivore abundance and are essential to testing the MRH through analyses of lead/lag relationships among vegetation composition, megaherbivore abundance, fire, and climate. Although some prior analyses of coprophilous fungal spores from individual sites have supported the MRH, these interpretations have been complicated by 1) discrepancies in the timing of coprophilous spore declines versus megaherbivore extinction timing based on dated vertebrate remains, 2) reliance on a single fungal taxon (Sporormiella) rather than a full suite of coprophilous fungi taxa, and 3) uncertainties in the taphonomic processes that influence fungal spore abundances. To examine the spatiotemporal relationships among megaherbivory, vegetation, and fire, we developed five new multi-taxon coprophilous fungal spore records for comparison with existing pollen, spore, and charcoal records from 14 sites across eastern North America. The MRH was well supported in the northeast and central US, with most sites showing a coprophilous spore decline by ∼14.6 ka followed by a rise of hardwood taxa (∼14.4 ka). However, changes in fire regime varied widely among northeast and central US sites and may have preceded spore declines. The MRH was not well supported in the southeastern US, where a smaller rise in hardwood taxa (∼16.1–13.1 ka) generally preceded the decline in coprophilous spores at individual sites (∼15.8–12.7 ka). These site-level and regional differences suggest spatial variations in the strength of couplings among late-Quaternary megaherbivore extinctions, vegetation composition and structure, and fire regime. Possible explanations for the differences between the northern and southeastern US include (1) differences in landscape heterogeneity of canopy openness and palatability, (2) net primary productivity and sensitivity to top-down trophic effects, (3) megaherbivore density, and (4) climate trends and seasonality at orbital to millennial timescales.

An Accounting Historian’s Response to Accounting for Slavery: Masters and Management by Caitlin Rosenthal

Caitlin Rosenthal’s monograph Accounting for Slavery examines the interface of business, accounting, and slave histories on both ante- and post-bellum plantations in both the Caribbean and the United States, providing archival examples and a comprehensive review of relevant literature from all three genres. Rosenthal also stimulates important questions that suggest pathways for extending research. While acknowledging the magnitude of the task, I question several major conclusions, especially those regarding accounting. My critique is rooted in an accounting historian’s perspective, whereas Rosenthal worked in management consulting prior to conducting her study. This distinctive background may account for many of our divergent views.The review focuses on plantation accounting practices during slavery, where Rosenthal’s monograph includes the most archival examples and speculative conclusions. It addresses four topic areas where Rosenthal and I differ substantially: first, characteristics of managerial and accounting practices on plantations; second, the comparability of these practices to those of northern US manufacturers; third, the relation of slave plantation management to scientific management; and fourth, the use/non-use of depreciation accounting on slave plantations.

Phenology and Monitoring of the Lesser Chestnut Weevil (Curculio sayi).

Simple SummaryThe lesser chestnut weevil (Curcilio sayi) is an emergent pest of chestnuts in the United States. Knowledge of this weevils phenology and the ability to monitor its populations will help us understand how this pest is emerging with expanding chestnut production and provide the means to begin to mitigate its effects on chestnut production. We explored the seasonal emergence of C. sayi in upstate New York through the use of traps and soil microcosms to understand when weevils begin to emerge and when the population peaks. We found that pyramid traps are most effective for monitoring and that populations have one generation that tends to peak late in the season. We also found that generational cohorts may stagger their emergence and delay leaving the soil for more than one year.With the introduction in recent years of high-yield blight-resistant chestnut varieties, the commercial chestnut industry in the United States is expanding. Accompanying this expansion is a resurgence in a primary pest of chestnut: C. sayi, the lesser chestnut weevil. This weevil damages the nut crop and infestations can surge from 0 to close to 100% in as little as two years. Understanding the dynamics of this pest has been challenging. Most work was conducted in the 1900s and only recently has this weevil garnered renewed interest. Recent work on C. sayi phenology has been completed in Missouri but conflicted with anecdotal reports from northern growers. From 2019 to 2020, we used a combination of trapping and microcosm studies to understand both C. sayi phenology and the means of monitoring this pest. C. sayi populations were univoltine and peaked in mid-October. Pyramid traps were the most effective at capturing adult C. sayi. C. sayi larvae, pupae, eclosed adults, and emerging adults were recovered from microcosm experiments. These results suggest that C. sayi emerges later in the northern US with the potential for a single generation to emerge over multiple subsequent years. Understanding C. sayi phenology along with the means of monitoring forms the basis for effective management and control in commercial chestnut orchards.

Weighting of Celestial and Terrestrial Cues in the Monarch Butterfly Central Complex.

Monarch butterflies rely on external cues for orientation during their annual long-distance migration from Northern US and Canada to Central Mexico. These external cues can be celestial cues, such as the sun or polarized light, which are processed in a brain region termed the central complex (CX). Previous research typically focused on how individual simulated celestial cues are encoded in the butterfly's CX. However, in nature, the butterflies perceive several celestial cues at the same time and need to integrate them to effectively use the compound of all cues for orientation. In addition, a recent behavioral study revealed that monarch butterflies can rely on terrestrial cues, such as the panoramic skyline, for orientation and use them in combination with the sun to maintain a directed flight course. How the CX encodes a combination of celestial and terrestrial cues and how they are weighted in the butterfly's CX is still unknown. Here, we examined how input neurons of the CX, termed TL neurons, combine celestial and terrestrial information. While recording intracellularly from the neurons, we presented a sun stimulus and polarized light to the butterflies as well as a simulated sun and a panoramic scene simultaneously. Our results show that celestial cues are integrated linearly in these cells, while the combination of the sun and a panoramic skyline did not always follow a linear integration of action potential rates. Interestingly, while the sun and polarized light were invariantly weighted between individual neurons, the sun stimulus and panoramic skyline were dynamically weighted when both stimuli were simultaneously presented. Taken together, this dynamic weighting between celestial and terrestrial cues may allow the butterflies to flexibly set their cue preference during navigation.

Unfreedom: Enslaving in New Jersey Through Gradual Abolition and Emancipation

ABSTRACT In 1804, New Jersey (NJ) legislators enacted a ‘Law for Gradual Abolition.’ However, this act did not free a single person nor did the 1846 ‘Act to Abolish Slavery,’ when all those still enslaved became ‘apprentices for life.’ Contributing to the growing literature addressing enslaving in the Northern US, and various gradations of freedom and unfreedom within and across wage labour and enslaving within shifting and developing capitalist economies, this article uses Census records and registers of children born to enslaved women to reveal enduring patterns of bondage holding Black people, particularly children, in conditions of unfreedom through and possibly after the Civil War, with far more enslaved people existing than is currently recognized. This data suggests the necessity of reconceptualising the lived experiences of ‘free’ Black people there as closer to enslaved, or ‘unfree,’ similar to that which has been documented elsewhere in the US and globally. These findings have significant implications for the longevity and potential contemporary legacies of legal mechanisms enabling this labour exploitation and divesting Black people of their freedom, earnings, and legal personhood in Northern states post-emancipation.

Young forests and fire: Using lidar–imagery fusion to explore fuels and burn severity in a subalpine forest reburn

AbstractAnticipating fire behavior as climate change and fire activity accelerate is an increasingly pressing management challenge in fire‐prone landscapes. In subalpine forests adapted to infrequent, stand‐replacing fire, self‐limitation of burn severity in short‐interval fire is incompletely understood. Spatially explicit fuels data can support assessments of landscape‐scale fire risk and fuel feedbacks on burn severity. For a ~1450‐km2 largely forested landscape in the US Northern Rocky Mountains, we used airborne lidar and imagery to predict and map canopy and surface fuels. In a fire that burned mature (>125‐year‐old) and also reburned young (~30‐year‐old) subalpine forest, we then asked: (1) How do prefire fuels and burn severity compare between young and mature forests that burned under similar fire weather conditions? (2) How well do prefire fuels and forest structure predict burn severity under extreme versus moderate fire weather? Lidar–imagery fusion predicted fuel characteristics with high accuracy across forest and shrubland vegetation. Young postfire forests had abundant, densely packed canopy fuels, and both young and mature forests had similar canopy fuel loads and coarse wood biomass. Under similar weather conditions, young and mature forests burned at similar severity. Overall, fuels were weak predictors of burn severity and, surprisingly, better predicted severity under extreme rather than moderate fire weather. Our findings are relevant for subalpine landscapes increasingly dominated by young lodgepole pine (Pinus contorta var. latifolia) forests vulnerable to short‐interval fire and provide a benchmark to assess how fuels influence burn severity in future fires. Fire managers should continually reassess fuels and update expectations about fire behavior as landscapes change. Although recovering postfire forests can limit fire spread and severity for a period of time, our results suggest that young subalpine forests in the Northern Rocky Mountains have sufficient fuel loads to burn at high severity and should not be considered effective fire breaks.

Durum wheat yield and protein influenced by nitrogen management and cropping rotation

Nitrogen (N) is the major input for cereal grain production. N management in durum wheat (Triticum turgidum subsp. durum) is critical for optimizing grain yield, protein concentration, and utilization efficiency of nitrogen fertilizer. A two-year study was conducted in the semi-arid region of the US Northern Great Plains (NGP) to investigate nitrogen input levels and application methods under fallow-durum and pea-durum systems. A durum wheat (cv. Joppa) was planted in the field following fallow or field pea with N input levels of 65 and 135 kg ha−1 and four application methods for each N input level. Results showed that water was the major limiting factor determining grain yield and protein concentration. Grain yield was greater but with similar protein concentration following fallow (1958 kg ha−1, 16.7%) than following field pea (1754 kg ha−1, 16.4%). Increasing N input from 65 kg ha−1 to 135 kg ha−1decreased grain yield from 1933 to 1779 kg ha−1 but improved protein concentration from 16.3 to 16.8%, which resulted in a negative nitrogen use efficiency (NUE). Application method of N did not significantly affect yield and protein, but there was a trend of yield increase via split application of N at the lower rate in a wetter year. The drought in 2017 resulted in lower test weight and harvest index (HI). The HI was lower in the135 kg ha−1 N rate than in the 65 kg ha−1 N rate, especially in the dryer year. Excessive N inputs in a water-limited environment may result in ‘haying-off’.

Observational-based assessment of contributions to maximum ozone concentrations in the western United States

ABSTRACT Archived Ozone Design Values (ODVs) provide smoothed temporal records of maximum ozone concentrations impacting monitoring sites throughout the US. Utilizing time series of ODVs recorded at sites along the US West Coast, we separately estimate ODV contributions from US background ozone and from production driven by US anthropogenic precursor emissions. Sondes launched from Trinidad Head in northern California measure the vertical distribution of baseline ozone transported ashore from the Pacific; this profile is reflected in the increase of the US background ODV contribution with monitoring site elevation in both rural and urban areas. The ODVs that would result from US background ozone alone are small at coastal, sea level locations (average ~45 ppb), but increase with altitude; above 1 km US background ODVs can exceed 60 ppb. US background ozone contributions now constitute the majority of the maximum ODVs throughout the US west coast region, including the Los Angeles urban area, which records the country’s highest ODVs. US anthropogenic emissions presently cause enhancements of 35 to 55 ppb to the maximum ODVs in the Los Angeles area; thus, local emission controls can further reduce ozone even though the background contribution is larger. In other US west coast urban areas ODV enhancements from US anthropogenic emissions are much smaller than the US background ODV contribution. The past decrease in US anthropogenic ODV enhancements from emission controls is larger than generally realized – a factor of more than 6 from 1980 to 2020, while US background ODV contributions varied to only a small extent over those four decades. Wildfire impacts on ODVs are significant in urban areas of the Pacific Northwest, but not over the vast northern US rural region. There is an indication that agricultural emissions of nitrogen oxides in California’s Salinas Valley increase downwind maximum ODVs by 5–10 ppb. Implications: In 2020 the ozone design values (ODVs) resulting from transported background ozone alone are now larger than the ODV enhancements from US anthropogenic precursor emissions, even in the Los Angeles urban area, where the nation’s highest ODVs are recorded. The US anthropogenic ODV enhancements have been reduced by more than a factor of 6 from 1980 to 2020. The maximum US background ODV contributions have varied somewhat, but in each of the US west coast urban areas it was 60 ppb or larger in 2000. These contributions are so large that reducing maximum urban ODVs to the 70 ppb required by the 2015 ozone NAAQS is very difficult. There remains relatively little room for further reducing ODVs through domestic emission controls alone. From this perspective, degraded US ozone air quality in the western US is primarily due to the US background ozone contribution, with the US anthropogenic enhancement making a significant, but smaller contribution. Notably, the US background ODV has slowly decreased (~1 ppb decade−1; Parrish, Derwent, and Faloona 2021) since the mid-2000s; cooperative, international emission control efforts aimed at continuing or even accelerating this background ozone decrease may be an effective approach to further ODV reductions, since the US background ODV is largely due to a hemisphere-wide, transported reservoir of ozone with contributions from all northern midlatitude continents. Given the major contribution of background ozone to observed ODVs, future reviews of the ozone NAAQS will be better informed if observational-based estimates of background ODV contributions are considered, in addition to model-derived estimates upon which past reviews have solely relied.

The glue that keeps everybody together: Peer support in mothers of young children with special health care needs.

BackgroundThe first years following diagnosis may be particularly challenging for parents and peer support from other parents of children with special health care needs may buffer their stress.MethodsThis qualitative interview study sought to explore the impact of early access to parental peer support and whether it leads to positive adaptation and improved family well‐being.ResultsFive mothers of young children with special health care needs from peer support organizations in two northern US states participated in interviews by telephone or Zoom. Themes of interest included professional scrutiny, going through the motions, someone who understands, learning and sharing, and one size does not fit all. Although most participants attributed positive changes in their emotional well‐being to the support they received, they were wary of extending the impact of peer support to their child and family.ConclusionsImplications for practice include embedding peer support programmes in neonatal care units and children's hospitals, as well as the addition of mindfulness practices to facilitate parental adaptation to disability and promote family well‐being.

Regional Variation and Syntactic Derivation of Low-frequencyneed-passives on Twitter

This paper examines constructions formed by the verb need taking a passivized complement. While previous dialectological, sociolinguistic, and micro-syntactic analyses have focused primarily on the past-participle complement (need+ED) as a regional syntactic variable, this study expands the purview of need-passives to examine gerund-participle (need+ING) and infinitival (need+TO) complements. It also looks beyond purported need+ED regions to examine need-passive variation in Englishes spoken around the world. Data from Twitter confirm previous findings that need+ED is a productive feature of the US Midland, Scotland, Northern Ireland, and Tyneside, England. However, tweets also show that need+ING is produced disproportionately frequently in England and Wales. These results reveal a more complex pattern of need-passive variation in global Englishes than has previously been reported. Additionally, a transitive construction formed with need as a matrix verb is examined and found to co-vary regionally with need+ING. Syntactic analyses of tweets reveal similarities in the ways that need+ED and need+ING vary with need+TO. These findings lead to a proposed syntactic analysis that need+ED and need+ING share the same derivational structure. More generally, the work argues for greater attention in linguistic research to low-frequency features.

METABOLIC SYNDROME & ITS DIETARY MANAGEMENT; A REVIEW

Metabolic Syndrome or MetS is a multifactorial disease consisting of obesity, hypertension, dyslipidemia, and hyperglycemia. It’s common in 25% of the general population in the Northern US and Western Europe. In Pakistan, the statistics of MetS are unknown, however, it is expected to be twice that of the US. The middle age group and the geriatrics population have the highest number of MetS cases with risk factors such as obesity, sedentary lifestyle, alcohol, inadequate, inadequate sleep, and a non-vegetarian diet. The complications of MetS include obesity, diabetes, and cardiovascular events. A Meditteranean diet rich in fruits and vegetables, whole grains, and olive oil as the source of fat is considered to be the only effective dietary management in MetS. Moreover, a high lean protein, low and complex carbohydrate and moderate unsaturated fats have also shown positive progress in MetS, especially with long-term weight reduction. Micronutrients requirements also increase in MetS. Fulfilling these increased requirements has been shown to regulate and improve the metabolism of fats and carbohydrates. Vitamin C and E, flavonoids, vitamin D, conjugated linoleic acid, omega-3 fatty acids, minerals such as magnesium and chromium, α-lipoic acid, phytoestrogens, and dietary fiber all have been studied to support the treatment of MetS along with aloe vera and other herbal products, yoga and aerobic exercises.

Do post‐harvest crop residues in no‐till systems provide for nitrogen needs of following crops?

AbstractIncreased adoption of no‐till systems in the Northern Plains has led to an increased volume of post‐harvest crop residue. A cool climate coupled with short growing seasons benefits from a conservation tillage approach by increasing water storage in semi‐arid areas where weather conditions are variable each year. The short frost‐free period presents challenges for residue decomposition and the subsequent nutrient uptake period is reduced in heavy accumulated crop fields. A combination of soil management practices can be used to optimize nutrient utilization, particularly for nitrogen (N), including the use of cover crops, crop rotation and diversification, and variances in fertilizer form, method, and timing. Despite many management practices being effective in conserving N in the soil, they still may not meet nutrient demands for succeeding crops in short season and water‐ and N‐limited environments. Decomposition of crop residue is dependent on soil moisture, soil temperature, and the carbon/nitrogen (C/N) ratio of crop residue. Generally, post‐harvest crop residues have a wider C/N ratio than aged residue that accumulates on the soil surface over time. Adding fertilizer N may reduce the immobilization of nutrients near the soil surface of a post‐harvest residue in heavily accumulated crop fields, making it more available for utilization by plants. Recommendations for fertilizer N rates are inconsistent throughout the northern US for long‐term no‐till systems. This review highlights several decades of known research yet points to the continued gaps needed for producers to fully support fertilizer N recommendations for no‐till systems in temperate climates.

Volcanic climate forcing, extreme cold and the Neolithic Transition in the northern US Southwest

The impacts on global climate of the AD 536 and 541 volcanic eruptions are well attested in palaeoclimatic datasets and in Eurasian historical records. Their effects on farmers in the arid uplands of western North America, however, remain poorly understood. The authors investigate whether extreme cold caused by these eruptions influenced the scale, scope and timing of the Neolithic Transition in the northern US Southwest. Archaeological tree-ring and radiocarbon dates, along with settlement survey data, suggest that extreme cooling generated the physical and social space that enabled early farmers to transition from kin-focused socio-economic strategies to increasingly complex and widely shared forms of social organisation that served as foundational elements of burgeoning Ancestral Pueblo societies.

Predicted climate conditions and cover crop composition modify weed communities in semiarid agroecosystems

AbstractThe US Northern Great Plains is one of the largest expanses of small grain agriculture, but excessive reliance on off‐farms inputs and predicted warmer and drier conditions hinder its agricultural sustainability. In this region, the use of cover crops represents a promising approach to increase biodiversity and reduce external inputs; however little information exists about how cover crop mixture composition, predicted climate and management systems could impact the performance of cover crops and weed communities. In the 4th cycle of a cover crop‐wheat rotation, we experimentally increased temperature and reduced moisture as expected to occur with climate change, and assessed impacts on the presence and composition of cover crop mixtures and termination methods on weed communities. Under ambient climate conditions, mean total cover crop biomass was 43%–53% greater in a five species early‐season cover crop mixture compared with a seven species mid‐season mixture, and differences were less pronounced in warmer and drier conditions (19%–24%). We observed a total of 18 weed species; 13 occurring in the early‐season mixture, 13 in the mid‐season mixtures and 14 in the fallow treatments. Weed species richness and diversity was lower in warmer and drier treatments, and we observed a shift in weed communities due to the presence and composition of cover crop mixtures as well as climate manipulations. Overall, results suggest that adoption of cover crop mixtures in semiarid agroecosystems requires jointly addressing weed management and soil moisture retention goals, a challenge further complicated by predicted climate conditions.

First report of stem rust, caused by Puccinia graminis, and crown rust, caused by Puccinia coronata var. avenae f. sp. avenae, on tall fescue (Festuca arundinacea) in Georgia, USA.

Stem rust, caused by Puccinia graminis, and crown rust, caused by P. coronata, are common rust diseases on cool-season grasses (Karakkat et al. 2018), for which long-distance spore dispersal was recorded in northern US (Harder and Haber 1992). During the summers of 2019 and 2020, severe infection of stem rust and crown rust was observed on > 60% of tall fescue (Festuca arundinacea) germplasm plants in a breeding nursery located at the University of Georgia, Griffin GA. Rust-infected leaves first presented uredinia pustules, then black telia towards the end of the season. The uredinia pustules of stem rust and crown rust were brick-red and, yellow and arranged along the host veins, respectively. The urediniospores were one-celled, round to ovoid and measured from 20.75±2.44 μm (crown rust) to 27±3.60 μm long (stem rust). The teliospores were two-celled and measured from 45.75±10.14 μm (stem rust) to 51.60±4.0 μm long (crown rust) (Leonard et al. 2005; Cummins 1971). Urediniospores of both rusts were collected from infected plants in the field in April of 2020 using a Piston vacuum pump (Welch by Gardner Denver Ltd.) and stored at -80 °C in 1.5 ml Eppendorf tubes. Genomic DNA was extracted by grinding the urediniospores in liquid nitrogen using mortar and pestle, followed by the cetyltrimethylammonium bromide method (Doyle and Doyle 1987). The internal transcribed spacer (ITS) region of the ribosomal DNA was amplified using the ITS5-ITS4 primers (White et al. 1990). BLASTn and phylogenetic analyses revealed that the sequence of stem rust (GenBank acc. no. MW430963) and crown rust (GenBank acc. no. MW431324) pathogens had >99% similarity with P. graminis (GenBank acc. no. HQ317538) and P. coronata var. avenae f. sp. avenae (clade V; Liu and Hambleton 2013) (GenBank acc. no. EU014044), respectively. Pathogenicity tests were conducted on the tall fescue cultivar 'Bandit'. For each rust, 12 pots (10 cm × 10 cm) were planted, each containing 13 seeds in a Sungro professional growing mix soil (Sun Gro Horticulture Distribution Inc.). The plant materials were kept in the greenhouse at 20°C/ 25°C (night/day),15-hrs of light, and watered twice a week for 4-weeks. Urediniospores were recovered from -80°C and allowed to acclimate at room temperature for 1 h. For each rust, 20 ml of suspension containing 1×105 urediniospores ml-1 and 5 μl of Tween-twenty (Agdia Inc. Elkhart, IN) were used to inoculate 6 pots; while 6 control pots were sprayed with sterile water. After inoculation, plants were allowed to dry for 1 h and then transferred to a dark chamber at 20°C and 90% of humidity for 12-15 h. At 10-days post inoculation, all inoculated plants developed rust symptoms identical to those observed in the field, whereas control plants had no symptoms. Stem and crown rust pathogens were re-isolated from the artificially inoculated tall fescue plants. Based on form, size, color and numbers of cells forming the spores, a 1947 Festuca elatior specimen from Georgia mentioning Puccinia coronata (Hanlin 1966), held at the Julian H. Miller Mycological Herbarium (Catalog No. GAM00013162), was discarded as an earlier record of P. coronata var. avenae and could have been misdiagnosed. Due to the fragile integrity of the original infected plant sample as well as the incipient infection, DNA identification was unsuccessful. To our knowledge, this is the first morphological, genetic and taxonomic report of P. graminis and P. coronata var. avenae f. sp. avenae on tall fescue in Georgia, USA.

Private landowners and the facilitation of an invasive species

• We explored private landowner perceptions about the invasive Kentucky bluegrass in the US northern Great Plains. • Landowner responses to a mail survey indicated little to no preventative action. • We also employed a scenario approach to assess landowner perceptions based on changes to ecosystem services. • Scenario results indicated that the early stage of invasion was considered slightly acceptable. At the late stage, when negative impacts are most severe for landowner livelihoods, bluegrass was rated as slightly unacceptable. • Cascading impacts will become more evident and incentivizing early action to prevent further invasion is key to maintaining these working landscapes.