Weed Establishment and Persistence after Water Pipeline Installation and Reclamation in the Mixed Grass Prairie of Western North Dakota

Weeds in reclamations interfere with success by: 1) competing with desirable species seeded during revegetation; 2) preventing recolonization of reclamations by native species; and 3) reducing the integrity of landscapes by expanding from reclamations into adjacent, intact areas. In the Bakken oilfield of western North Dakota, dispersed reclamation activity and increased traffic may provide many opportunities for weeds to spread. To determine the potential for disturbance and reclamation to increase resident weed populations and introduce new weed species, we tracked twenty-one weed (non-native/ruderal/invasive) species over a four-year period after the installation of a 1.8 km livestock water pipeline and subsequent land reclamation on a historic ranch in western North Dakota. We included areas of historic (early 20th century homestead) and recent (prairie dog town) landscape disturbances and tracked weed frequency and density in the disturbed pipeline and in the directly adjacent intact prairie. Most of the weeds in the pipeline were non-persistent populations of naturalized species. Our data show that although naturalized weeds may respond positively to disturbance, they can quickly return to pre-disturbance levels. However, disturbance may have resulted in the introduction of one new noxious weed, Hyoscyamus niger (black henbane). Agropyron cristatum (crested wheatgrass), an invasive, non-native perennial grass that reduces native plant diversity and forage value, was also introduced. This study demonstrates the importance of prevention of weed dispersal during disturbance and reclamation, contamination-free seed sources, and post-reclamation follow up to control any weeds that may have been introduced as a result of pipeline development

Annual Cover Crops Do Not Inhibit Early Growth of Perennial Grasses on a Disturbed Restoration Soil in the Northern Great Plains, USA

In agricultural, rangeland, and forest system revegetation projects, cover crops are used for competitive exclusion of weeds and to stabilize soil. Within revegetation projects, annual or short-lived perennial grasses are often sown at the same time as the perennial grasses that are the desired species for long-term landscape rehabilitation. When cover crops are utilized to control weeds, the same principle of competitive exclusion may apply to sown perennial grasses. In this project, we tested if an annual grass cover crop reduces the early stage performance of sown perennial grasses. We conducted four experiments to evaluate the effects of annual cover crops on perennial grasses. The experiments included ex situ growth chamber experiments in two soil types, an agronomic soil, and soil collected from a revegetation project in a trenched water pipeline in western North Dakota. We also performed two in situ experiments where the presence of annuals was manipulated. Annual cover crops only reduced perennial grass biomass ex situ in the agronomic soil. The disturbed pipeline soil was high in sulfur and sodium. Even when this soil was fertilized, annual cover crops did not reduce sown perennial performance. In stressful environments, or when there is natural microenvironmental variability, annual cover crops do not appear to be costly for the early-stage establishment of more long-term, desirable species

Invasive Grasses Consistently Create Similar Plant-soil Feedback Types in Soils Collected from Geographically Distant Locations

Aims Plants of similar life forms and closely related species have been observed to create similar types of plant–soil feedbacks (PSFs). However, investigations of the consistency of PSFs within species have not yielded clear results. For example, it has been reported that species create different types of PSFs in their native and introduced ranges. The aim of this project is to examine if four species create similar PSF types from soils collected from widely distributed areas within their introduced range. The soil for this project was collected from three areas in western North America. With this design, we aim to determine species- and site-specific ability to create PSFs and if the type of PSF created is consistent in all soil from all three collection areas. The species examined are Agropyron cristatum, Centaurea solstitialis, Poa pratensis and Taeniatherum caput-medusae. Methods We used three-field collected soils (from northern Nevada, western Montana and eastern Montana) in a two-phase greenhouse experiment to quantify the type of PSFs created by four invasive species. The first phase was a conditioning phase wherein each invasive species created species-specific changes to the soil. The second phase of the experiment was the response phase wherein both the conditioning species and a native phytometer were grown in the conditioned soil and in unconditioned (control) soil. The final aboveground biomass was used to evaluate the effect of conditioning and to determine the type of PSF created by each invasive species. Important Findings Our results suggest that three of our four study species did show consistency in relation to PSF. Two species A. cristatum and T. caputmedusae consistently created PSF types that benefit conspecifics more than heterospecifics (and thus are ‘invasive’ PSF types) and P. pratensis consistently exhibited no, or ‘neutral’, feedbacks. The fourth species (C. solstitialis) was inconsistent: in one soil, no feedback was created; in other soil, an invasive PSF was created and in the last soil, a feedback that relatively benefited the native phytometer was created. Thus, PSFs appear to uniformly contribute to the success of two species (A. cristatum and T. caput-medusae) but not C. solstitialis nor P. pratensis

Spatial Variation in Germination of Two Annual Brome Species in the Northern Great Plains

Downy brome or cheat grass (Bromus tectorum L.) and field brome (B. arvensis L.; Synonym = Bromus japonicus Thunb. ex Murr.; Japanese brome) are two annual exotic species that have increased the intensity and frequency of fire cycles in the Intermountain West of the United States, with millions of dollars in associated costs (DiTomaso 2000). These invasive brome species have a different impact in the Northern Great Plains of North America where they commonly co-occur in disturbed sites (White and Currie 1983, Haferkamp et al. 1993). In these mixed-grass prairie rangelands, annual bromes compete against other forage species (Haferkamp et al. 1997) and reduce litter decomposition rates (Ogle et al. 2003), which negatively impacts ecosystem services of biomass production and soil nutrient availability. In central plains croplands, downy brome invades alfalfa fields (Kapusta and Strieker 1975), wheat fields (Wicks 1984, Ostlie and Howatt 2013), and perennial grass pastures and seed production areas (Wicks 1984). Downy brome is a regulated plant in Montana (Montana Noxious Weed List, December 2013) and has been found in all counties of Montana since 1950 (Menalled et al. 2008). Field brome is found in all North American states and provinces (USDA Plants Database http://plants.usda.gov). It is used as a winter cover crop in vegetable plots and orchards in the Northeastern United States (NRCS 2006). Field brome has no formal designation in the state of Montana, although downy brome and field brome are commonly grouped together and are referred to colloquially as “cheatgrass” in the state

Seed Source May Determine Field-Specific Germination and Emergence: The Source by Planting Environment Interaction

Farm environmental conditions and management practices can result in within-cultivar differences in seed quality and lead to transgenerational plasticity (farm-specific effects on offspring, or TGP) that affect germination and emergence in transplant fields. We used three perennial bunchgrasses, [green needlegrass (Nassella viridula) ‘Lodorm’, slender wheatgrass (Elymus trachycaulus) ‘Pryor’, and bluebunch wheatgrass (Pseudoregneria spicata) prevariety registered germplasm P-7] to determine if seeds exhibited TGP. We also determined if TGP was affected by the interaction between production farms and planting environments (farm × environment interaction, or context-dependent TGP), using four laboratory temperature regimes to test germination response and four field environments to test emergence response in 2013. We stored seeds in four different environments for 10 mo before repeating the experiment to test if recent seed storage conditions mitigated TGP. Contextdependent TGP affected emergence for Pryor and Lodorm both years, however, only Pryor exhibited context-dependent TGP for germination in 2013. Sources with low germination and emergence in the field were less likely to exhibit context-dependent TGP. Some transplant fields did not show differences among sources, but in other transplant fields, emergence increased as much as 24% depending on farm source. The effect of recent seed storage conditions, significant only for Pryor, was opposite for germination and emergence, with room-temperature stored seeds exhibiting the highest emergence and lowest germination. Context-dependent TGP in emergence could not be predicted by our coarse information regarding seed production environments and storage conditions or by germination in the lab. Nonetheless, context-dependent TGP significantly determined emergence in two of the three study species. Mechanisms underlying this phenomenon need further study to understand potential benefits and pitfalls for producers and seed buyers

Underutilized resources for studying the evolution of invasive species during their introduction, establishment, and lag phases

The early phases of biological invasions are poorly understood. In particular, during the introduction, establishment, and possible lag phases, it is unclear to what extent evolution must take place for an introduced species to transition from established to expanding. In this study, we highlight three disparate data sources that can provide insights into evolutionary processes associated with invasion success: biological control organisms, horticultural introductions, and natural history collections. All three data sources potentially provide introduction dates, information about source populations, and genetic and morphological samples at different time points along the invasion trajectory that can be used to investigate preadaptation and evolution during the invasion process, including immediately after introduction and before invasive expansion. For all three data sources, we explore where the data are held, their quality, and their accessibility. We argue that these sources could find widespread use with a few additional pieces of data, such as voucher specimens collected at certain critical time points during biocontrol agent quarantine, rearing, and release and also for horticultural imports, neither of which are currently done consistently. In addition, public access to collected information must become available on centralized databases to increase its utility in ecological and evolutionary research

Ethnic Comparison of Weight Loss in Trial of Nonpharmacologic Interventions in the Elderly

https://onlinelibrary.wiley.com/doi/epdf/10.1038/oby.2002.1

What causes increasing and unnecessary use of radiological investigations? a survey of radiologists' perceptions

<p>Abstract</p> <p>Background</p> <p>Growth in use and overuse of diagnostic imaging significantly impacts the quality and costs of health care services. What are the modifiable factors for increasing and unnecessary use of radiological services? Various factors have been indentified, but little is known about their relative impact. Radiologists hold key positions for providing such knowledge. Therefore the purpose of this study was to obtain radiologists' perspective on the causes of increasing and unnecessary use of radiological investigations.</p> <p>Methods</p> <p>In a mailed questionnaire radiologist members of the Norwegian Medical Association were asked to rate potential causes of increased investigation volume (fifteen items) and unnecessary investigations (six items), using five-point-scales. Responses were analysed by using summary statistics and Factor Analysis. Associations between variables were determined using Students' t-test, Spearman rank correlation and Chi-Square tests.</p> <p>Results</p> <p>The response rate was 70% (374/537). The highest rated causes of increasing use of radiological investigations were: a) new radiological technology, b) peoples' demands, c) clinicians' intolerance for uncertainty, d) expanded clinical indications, and e) availability. 'Over-investigation' and 'insufficient referral information' were reported the most frequent causes of unnecessary investigations. Correlations between causes of increasing and unnecessary radiology use were identified.</p> <p>Conclusion</p> <p>In order to manage the growth in radiological imaging and curtail inappropriate investigations, the study findings point to measures that influence the supply and demand of services, specifically to support the decision-making process of physicians.</p