Northern US Research Articles

The safe passage study: design, methods, recruitment, and follow-up approach.

The Safe Passage Study is a large, prospective, multidisciplinary study designed to (1) investigate the association between prenatal alcohol exposure, sudden infant death syndrome (SIDS), and stillbirth, and (2) determine the biological basis of the spectrum of phenotypic outcomes from exposure, as modified by environmental and genetic factors that increase the risk of stillbirth, SIDS, and in surviving children, fetal alcohol spectrum disorders. The results provided are based on an interim assessment of 6004 women enrolled, out of the 12,000 projected, from the Northern Plains, US, and Cape Town, South Africa, areas known to be of high risk for maternal drinking during pregnancy. Research objectives, study design, and descriptive statistics, including consent, recruitment, and retention information, are provided. Overall visit compliance is 87%, and includes prenatal, delivery/newborn, and postnatal contacts through 1 year post-delivery. Pregnancy outcome ascertainment is 98% prior to medical chart review; less than 2% of women withdraw. Consent for the use of DNA and placental tissue exceed 94%, and consent to participate in the autopsy portion of the study is 71%. The Safe Passage Study is the first multi-site study of SIDS and stillbirth to integrate prospectively collected exposure information with multidisciplinary biological information in the same maternal and fetal/infant dyad using a common protocol. Essential components of the study design and its success are close ties to the community and rigorous systems and processes to ensure compliance with the study protocol and procedures.

Speciation in Western Scrub-Jays, Haldane's rule, and genetic clines in secondary contact.

BackgroundHaldane’s Rule, the tendency for the heterogametic sex to show reduced fertility in hybrid crosses, can obscure the signal of gene flow in mtDNA between species where females are heterogametic. Therefore, it is important when studying speciation and species limits in female-heterogametic species like birds to assess the signature of gene flow in the nuclear genome as well. We studied introgression of microsatellites and mtDNA across a secondary contact zone between coastal and interior lineages of Western Scrub-Jays (Aphelocoma californica) to test for a signature of Haldane’s Rule: a narrower cline of introgression in mtDNA compared to nuclear markers.ResultsOur initial phylogeographic analysis revealed that there is only one major area of contact between coastal and interior lineages and identified five genetic clusters with strong spatial structuring: Pacific Slope, Interior US, Edwards Plateau (Texas), Northern Mexico, and Southern Mexico. Consistent with predictions from Haldane’s Rule, mtDNA showed a narrower cline than nuclear markers across a transect through the hybrid zone. This result is not being driven by female-biased dispersal because neutral diffusion analysis, which included estimates of sex-specific dispersal rates, also showed less diffusion of mtDNA. Lineage-specific plumage traits were associated with nuclear genetic profiles for individuals in the hybrid zone, indicating that these differences are under genetic control.ConclusionsThis study adds to a growing list of studies that support predictions of Haldane’s Rule using cline analysis of multiple loci of differing inheritance modes, although alternate hypotheses like selection on different mtDNA types cannot be ruled out. That Haldane’s Rule appears to be operating in this system suggests a measure of reproductive isolation between the Pacific Slope and interior lineages. Based on a variety of evidence from the phenotype, ecology, and genetics, we recommend elevating three lineages to species level: A. californica (Pacific Slope); A. woodhouseii (Interior US plus Edwards Plateau plus Northern Mexico); A. sumichrasti (Southern Mexico). The distinctive Edwards Plateau population in Texas, which was monophyletic in mtDNA except for one individual, should be studied in greater detail given habitat threat.

Evaluating the influence of road salt on water quality of Ohio rivers over time

Anthropogenic inputs have largely contributed to the increasing salinization of surface waters in central Ohio, USA. Major anthropogenic contributions to surface waters are chloride (Cl−) and sodium (Na+), derived primarily from inputs such as road salt. In 2012–2013, central Ohio rivers were sampled and waters analyzed for comparison with historical data. Higher Cl− and Na+ concentrations and fluxes were observed in late winter as a result of increased road salt application during winter months. Increases in both chloride/bromide (Cl−/Br−) ratios and nitrate (N-NO3−) concentrations and fluxes were observed in March 2013 relative to June 2012, suggesting a mixture of road salt and fertilizer runoff influencing the rivers in late winter. For some rivers, increased Cl− and Na+ concentrations and fluxes were observed at downstream sites near more urban areas of influence. Concentrations of Na+ were slightly lower than respective Cl− concentrations (in equivalents). High Cl−/Br− mass ratios in the Ohio surface waters indicated the source of Cl− was likely halite, or road salt. In addition, analysis of 36Cl/Cl ratios revealed low values suggestive of a substantial dissolved halite component, implying the addition of “old” Cl− into the water system. Temporal trend analysis via the Mann–Kendall test identified increasing trends in Cl− and Na+ concentration beginning in the 1960s at river locations with more complete historical datasets. An increasing trend in Cl− flux through the 1960s was also identified in the Hocking River at Athens, Ohio. Our results were similar to other studies that examined road salt impacts in the northern US, but a lack of consistent long-term data hindered historical analysis for some rivers.

Aerially seeding cover crops in the northern US Corn Belt: Limitations, future research needs, and alternative practices

I ncorporating cover crops into the two-year corn ( Zea mays L.)–soybean ( Glycine max L.) rotation can reduce soil erosion, increase soil organic matter, improve soil structure (Snapp et al. 2005), and reduce nitrate (NO3) leaching (Strock et al. 2004; Fisher et al. 2011). However, it is often difficult to establish winter cover crops in the cooler climate and shorter growing season of the northern Corn Belt. Miguez and Bollero (2005) reported that grass cover crops in the north central United States would only provide marginal benefits due to low biomass production. Through growth simulations, Baker and Griffis (2009) found that the main limitations are degree days and photosynthetically active radiation. Strock et al. (2004) suggested that based on average weather patterns in southwestern Minnesota, winter rye ( Secale cereal L.) would only be a successful cover crop in one out of four years. In these studies, however, temperatures were already cool when the cover crop was planted following harvest of the preceding crop. As another option, Frye et al. (1988) suggested that broadcasting seed into a standing crop can result in earlier crop growth than drilling the seed after harvest. Through growth simulations based on field experiments, Feyereisen et al. (2006) recommended…

Nitrogen fertilizer and landscape position impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass

AbstractThis study was conducted to evaluate the impacts of N fertilizer and landscape position on carbon dioxide (CO2) and methane (CH4) fluxes from a US Northern Great Plains landscape seeded to switchgrass (Panicum virgatum L.). The experimental design included three N levels (low, 0 kg N ha−1; medium, 56 kg N ha−1; and high, 112 kg N ha−1) replicated four times. The experiment was repeated at shoulder and footslope positions. Soil CO2 and CH4 fluxes were monitored once every 2 weeks from May 2010 to October 2012. The CO2 fluxes were 40% higher at the footslope than the shoulder landscape position, and CH4 fluxes were similar in both landscape positions. Soil CO2 and CH4 fluxes averaged over the sampling dates were not impacted by N rates. Seasonal variations showed highest CO2 release and CH4 uptake in summer and fall, likely due to warmer and moist soil conditions. Higher CH4 release was observed in winter possibly due to increased anaerobic conditions. However, year to year (2010–2012) variations in soil CO2 and CH4 fluxes were more pronounced than the variations due to the impact of landscape positions and N rates. Drought conditions reported in 2012, with higher annual temperature and lower soil moisture than long‐term average, resulted in higher summer and fall CO2 fluxes (between 1.3 and 3 times) than in 2011 and 2010. These conditions also promoted a net CH4 uptake in 2012 in comparison to 2010 when there was net CH4 release. Results from this study conclude that landscape positions, air temperature, and soil moisture content strongly influenced soil CO2 fluxes, whereas soil moisture impacted the direction of CH4 fluxes (uptake or release). However, a comprehensive life cycle analysis would be appropriate to evaluate environmental impacts associated with switchgrass production under local environmental conditions.

Conservation Easements and Management by Family Forest Owners: A Propensity Score Matching Approach with Multi-Imputations of Survey Data

Increasingly, private landowners are participating in conservation easement programs, but their effects on land management remain to be addressed. Data from the USDA Forest Service National Woodland Owner Survey for the US Northern Region were used to investigate how conservation easement participation is associated with selected past and future forest management practices. Multiple data imputation was used to correct for missing data bias, and propensity score matching was applied to correct for selection bias. Results show that only the adoption of forest management plans, among 17 forest management practices, was significantly and positively correlated with easement participation. Conservation easements legally bind participants to maintain land forested, but there was no evidence of greater association between easement participation and active forest management practices, including timber harvesting. These findings suggest that adoption of conservation easements is a policy tool that can preserve forestland from changing to other uses but may not necessarily be conducive to wider implementation of land practices necessary for long-term protection of forests.

Changes in field-level cropping sequences: Indicators of shifting agricultural practices

Farmers implement an assortment of management practices to ensure the sustainability, economic viability, and resilience of their operation. Dryland farming practices dominate in the semiarid regions of the US northern Great Plains, where historical practice has been to rotate small-grain cereals with whole-year summer fallow; however, pulse crops (e.g., lentils) have become increasingly common in these regions as an alternative to fallow. The area of fallow in northeastern Montana, for example, has decreased by one-third, while the area of pulse crops has increased more than five-fold. Our objectives were: (1) to characterize the principal cropping sequences in northeast Montana during the period of regional pulse crop adoption (2001–2012); and (2) to identify changes in the relative proportions of these sequences during the same period. We identified crops at the field-level by class (cereal, pulse, fallow, or cereal–fallow strips) for 2001–2012 using multitemporal Landsat imagery in conjunction with the cropland data layer, cadastral data, ground reference data, and local producers’ records. The annual crop classifications were combined into a 12-character string for each field that represented the sequence of crop classes for 2001–2012. We then searched these strings for specific 2- and 3-year crop sequences with a string-matching algorithm. The most abundant sequences involved continuous cereal, block-managed cereal–fallow, and cereal–pulse. We also observed a steady decrease in the abundance of cereal–fallow sequences managed by strip-cropping that were coincident with increases in block-managed cereal–fallow sequences and with increases in pulse production. We conclude that, over the study's time frame, regional producers grew more cereal crops and fallowed fields less frequently, but did not appear to strongly adhere to specific sequences. Furthermore, strip-cropping as a management practice has declined substantially.

Past and future extreme climatic events in Canadian prairies: Integrating economics and climate

T occurrence of dry & wet events causes major adverse impacts in the Canadian Prairies. In the past, dry events, which are typically agricultural and/or hydrological droughts, have been common in the region. At least five major drought episodes have occurredin the Canadian Prairies during the past 120 years. These include multi-year droughts in the 1890s, 1910s, 1930s, late 1950s to early 1960s, 1980s, 1999-2005, 2009-10. The years 2001-2004 resulted in one of the largest area multi-year drought. Almost half of the agricultural prairies were in severe drought or worse during 2001. For the older droughts of the 1900 to 1950 period, the 1930s were the largest multi-year droughts, and 1961 and 1919 were the single-year severe droughts that covered the largest area. According to Bonsal et al. (2011), some of the major droughts have migrated into the Canadian Prairies from the United States Great Plains, including the 1999-2005 drought. This means that it is important to monitor the northern US droughts for expansion or migration into Canada.In the future, the frequency of both droughts and intense precipitation areexpected to increase. In fact, the review by Wheaton et al. (2013) found that (i) multi-year droughts (e.g., 5 to 10 years, or so) would occur more than twice as often forthe period to 2100; (ii) they would come with more evaporative power and be more intense as they will have much higher temperatures and much longer warm seasons; and (iii) they would cover much more area than even the across-Canada drought of 2001-2002. Droughts of such magnitudes would have devastating impacts on the Prairies, economically, environmentally, and socially, particularly on those industries where weather is a major determining factor to their survival and performance. One such industry is agriculture. It is the contention of this paper that estimation of impacts of the past droughts has been limited in scope, and may have underestimated these impacts. This under-estimation may be a result of several reasons: (i) Past studies have typically measured these impacts for only the drought period. In reality a drought would affect some of the enterprises (such as livestock production) that take several years to completely result in an economic gain to the producers. (ii) Although private costs of the people impacted by droughts are measured, the macro-level changes causing hardships to people and businesses are not measured. (iii) Droughts may impact ecological goods and services which can then affect the society at large. (iv) Loss to human capital through stress, sickness, and loss of employment as well as other changes that lead to lost productivity are typically not included. (v) Fiscal costs to the governments and their resulting impact on other programs have not been estimated. (vi) Economic hardships to smaller communities and people living therein have also not been addressed. We recommend that future investigations attempt to redress these deficiencies in the method of estimation of social, environmental and economic impacts of droughts. Impacts of the recent severe droughts in the US Plains and Canadian Prairies are reminders that current adaptation can be improved.

Analysis of geological ochre: its geochemistry, use, and exchange in the US Northern Great Plains

Samples of pigments indigenous to the US Northern Great Plains were collected in association with the conservation of a buffalo hide tanned and painted by a Crow Indian(s) in the 19th century, which is now in the collection of the National Museum of American Indian. The pigments were characterised using a series of analytical techniques – some common and others uncommon to the conservation science field, including portable X-ray fluorescence (pXRF), X-ray diffraction (XRD), and instrumental neutron activation analysis (INAA). XRF is not capable of differentiating between various ochre samples due to high detection limits. XRD can detect some matrix minerals in each sample, but these data cannot characterise pigments by original source location. INAA is capable of characterizing ochres from different sources based on trace element geochemistry; however, the large sample size it requires (approximately 100 mg), makes sampling from objects challenging and therefore makes it difficult to use for technical art history studies that focus on museum objects. INAA is useful if applied to reference materials, such as historic pigments or known sources for historic artistic materials.

Mediterranean diet and cancer: epidemiological evidence and mechanism of selected aspects

BackgroundPopulations living in the area of the Mediterranean Sea suffered by decreased incidence of cancer compared with those living in the regions of northern Europe and US countries, attributed to healthier dietary habits. Nowadays, we are assisting to a moving away from the traditional Mediterranean dietary pattern, but whether this changing is influencing risk of cancers is still unclear. The aim of the study was to review recent evidence on potential relationship between the adherence to the Mediterranean diet and cancer.DiscussionThe most recent pooled analyses of epidemiological studies supported strongly the hypothesis that the Mediterranean diet may play a role in preventing several types of cancers, especially those of digestive tract, whereas contrasting results were reported for hormone-dependent cancers. Specific aspects of the Mediterranean diet such as high fruit and vegetables and low red processed meat intake may explain such protective effects. Moreover, evidence regarding olive oil and whole grains increase the beneficial effects of such dietary pattern against cancer.ConclusionsLiterature evidence actually demonstrates that the increased adherence to the Mediterranean dietary pattern is beneficial to health across populations and may translate a protective effect with certain cancers.

Crop yields and soil organic matter responses to sheep grazing in US northern Great Plains

Sheep (Ovis aries L.) grazing, a cost-effective method of controlling weeds compared to herbicide application and tillage, may influence soil C and N levels by consuming plant residue and returning feces and urine to the soil, but little is known about the practice on soil C and N storage under dryland cropping systems in the northern Great Plains, USA. Three weed control practices [sheep grazing (GRAZ), herbicide application (CHEM), and tillage (MECH)] and three cropping sequences [continuous alfalfa (Medicago sativa L.) (CA), continuous spring wheat (Triticum aestivum L.) (CSW), and spring wheat-pea (Pisum sativum L.)/barley (Hordeum vulgaris L.) hay mixture-fallow (W-P/B-F)] were evaluated on a Blackmore silt loam from 2009 to 2011 in southwestern Montana, USA. Crop yields and soil organic C (SOC), total N (STN), NH4-N, and NO3-N contents at the 0–120cm depth were quantified. Annualized spring wheat grain and biomass (stems+leaves) yields and C and N contents were greater with CSW than with W-P/B-F, but hay biomass and C content were similar between CA and W-P/B-F. While C and N in aboveground biomass after spring wheat and hay harvest were removed through haying in CHEM and MECH, sheep grazing removed about 99% of these elements in GRAZ. The SOC and STN at 5–15cm were greater with CSW or W-P/B-F than with CA in GRAZ and MECH, but SOC at 30–60cm was greater with CA than with CSW in MECH. The NH4-N content at most depths varied among treatments and years, but NO3-N content at 5–120cm was greater with CSW and W-P/B-F than with CA. Longer duration of sheep grazing during fallow periods due to increased return of C and N through feces and urine or residue incorporation to a greater depth probably increased soil C and N storage at the surface layer with CSW and W-P/B-F in GRAZ and MECH, but increased root biomass likely increased C storage at the subsurface layer with CA in MECH. Absence of N fertilization and/or greater N uptake probably reduced soil NO3-N level with CA than with other cropping sequences. Regardless of treatments, SOC and STN declined from 2009 to 2011, probably due to residue removal from haying and grazing. Moderate sheep grazing during fallow periods can be used to increase soil C and N storage, obtain farm C credit, and sustain dryland crop yields compared to herbicide application for weed control in the semiarid regions.

Substitutable habitats? The biophysical and anthropogenic drivers of an exotic bird’s distribution

Abstract The spread and distribution of exotic species depends on a number of factors, both anthropogenic and biophysical. The importance of each factor may vary geographically, making it difficult to predict where a species will spread. In this paper, we examine the factors that influence the distribution of monk parakeets (Myiopsitta monachus), a parrot native to South America that has become established in the United States. We use monk parakeet observations gathered from citizen-science datasets to inform a series of random forest models that examine the relative importance of biophysical and anthropogenic variables in different regions of the United States. We find that while the distribution of monk parakeets in the southern US is best explained by biophysical variables such as January dew point temperature and forest cover, the distribution of monk parakeets in the northern US appears to be limited to urban environments. Our results suggest that monk parakeets are unlikely to spread outside of urban environments in the northern United States, as they are not adapted to the climatic conditions in that region. We extend the notion of “substitutable habitats,” previously applied to different habitats in the same landscape, to exotic species in novel landscapes (e.g., cities). These novel landscapes provide resources and environmental conditions that, although very different from the species’ native habitat, still enable them to become established. Our results highlight the importance of understanding the regionally-specific factors that allow an exotic species to become established, which is key to predicting their expansion beyond areas of introduction.

Future humidity trends over the western United States in the CMIP5 global climate models and variable infiltration capacity hydrological modeling system

Abstract. Global climate models predict relative humidity (RH) in the western US will decrease at a rate of about 0.1–0.6 percentage points per decade, albeit with seasonal differences (most drying in spring and summer), geographical variability (greater declines in the interior), stronger reductions for greater anthropogenic radiative forcing, and notable spread among the models. Although atmospheric moisture content increases, this is more than compensated for by higher air temperatures, leading to declining RH. Fine-scale hydrological simulations driven by the global model results should reproduce these trends. It is shown that the MT-CLIM meteorological algorithms used by the Variable Infiltration Capacity (VIC) hydrological model, when driven by daily Tmin, Tmax, and precipitation (a configuration used in numerous published studies), do not preserve the original global model's humidity trends. Trends are biased positive in the interior western US, so that strong RH decreases are changed to weak decreases, and weak decreases are changed to increases. This happens because the MT-CLIM algorithms VIC incorporates infer an overly large positive trend in atmospheric moisture content in this region, likely due to an underestimate of the effect of increasing aridity on RH. The result could downplay the effects of decreasing RH on plants and wildfire. RH trends along the coast have a weak negative bias due to neglect of the ocean's moderating influence. A numerical experiment where the values of Tdew are altered to compensate for the RH error suggests that eliminating the atmospheric moisture bias could, in and of itself, decrease runoff up to 14% in high-altitude regions east of the Sierra Nevada and Cascades, and reduce estimated Colorado River runoff at Lees Ferry up to 4% by the end of the century. It could also increase the probability of large fires in the northern and central US Rocky Mountains by 13 to 60%.

Post-anthesis development of oil content and composition with respect to seed moisture in two high-oleic sunflower hybrids in the northern US

Desiccating sunflower (Helianthus annuus L.) at physiological maturity (PM) or earlier can be used to hasten harvest and thus, reduce yield losses associated with severe weather, plant degradation, and bird predation. Previous work showed that two modern oilseed hybrids studied reached PM at seed moisture content of about 40% and could be desiccated earlier than current recommendations for sunflower production in the northern U.S. However, the effects of early desiccation on oil content and quality are not well understood. Therefore, the objective of the present study was to determine the relationship between seed oil and moisture content of seed from the peripheral and intermediate zones of the capitulum in two high-oleic sunflower hybrids and evaluate fatty acid composition with respect to seed moisture. A 2-year field study was conducted at Prosper, ND, and Morris, MN, and seeds were collected from capitula at 4- to 7-d intervals between stages R6 and R9. Maximum oil content of both peripheral and intermediate zone seeds occurred at moisture contents ranging from about 43 to 49% depending on the hybrid. The fully developed proportion of stearic, oleic, and linoleic acids in the seed oil was established at as high or higher seed moisture than total oil content regardless of hybrid or seed position. Results indicate that maximum oil content and fatty acid composition for the two oil hybrids were reached about 2–6d earlier than PM. Therefore, oil quantity and quality will not be compromised if desiccation of the crop is based on seed moisture content at PM.

Carbon benefits from protected areas in the conterminous United States.

BackgroundConversion of forests to other land cover or land use releases the carbon stored in the forests and reduces carbon sequestration potential of the land. The rate of forest conversion could be reduced by establishing protected areas for biological diversity and other conservation goals. The purpose of this study is to quantify the efficiency and potential of forest land protection for mitigating GHG emissions.ResultsThe analysis of related national-level datasets shows that during the period of 1992–2001 net forest losses in protected areas were small as compared to those in unprotected areas: -0.74% and −4.07%, respectively. If forest loss rates in protected and unprotected area had been similar, then forest losses in the protected forestlands would be larger by 870 km2/yr forests, that corresponds to release of 7 Tg C/yr (1 Tg=1012 g). Conversely, and continuing to assume no leakage effects or interactions of prices and harvest levels, about 1,200 km2/yr forests could have remained forest during the period of 1992–2001 if net area loss rate in the forestland outside protected areas was reduced by 20%. Not counting carbon in harvested wood products, this is equivalent to reducing fossil-fuel based carbon emissions by 10 Tg C/yr during this period. The South and West had much higher potentials to mitigate GHG emission from reducing loss rates in unprotected forests than that of North region. Spatially, rates of forest loss were higher across the coastal states in the southeastern US than would be expected from their population change, while interior states in the northern US experienced less forest area loss than would have been expected given their demographic characteristics.ConclusionsThe estimated carbon benefit from the reduced forest loss based on current protected areas is 7 Tg C/yr, equivalent to the average carbon benefit per year for a previously proposed ten-year $110 million per year tree planting program scenario in the US. If there had been a program that could have reduced forest area loss by 20% in unprotected forestlands during 1992–2001, collectively the benefits from reduced forest loss would be equal to 9.4% of current net forest ecosystem carbon sequestration in the conterminous US.

Promising results in central Alberta with rough fescue (Festuca hallii) seeding following disturbance

Plains rough fescue (<i>Festuca hallii</i> (Vasey) Piper [Poaceae]), once dominant in rough fescue grasslands of central Canada and the northern US, recovers poorly if disturbed by cattle grazing or oil and gas production soil handling techniques. This long-lived bunchgrass requires 3 to 5 y to become established, during which time it may be exposed to competition from faster-growing species. Our first research objective was to assess the recovery of <i>F. hallii</i> by comparing a monoculture seeding to a mixed seeding of native grass (Poaceae) species including <i>F. hallii</i>, <i>Koeleria macrantha</i> (Ledeb.) Schult., <i>Elymus trachycaulus</i> (Link) Gould ex Shinners ssp. <i>subsecundus</i> (Link) Á. Löve &amp; D. Löve, <i>Pascopyrum smithii</i> (Rydb.) Á. Löve, <i>Nassella viridula</i> (Trin.) Barkworth, <i>Hesperostipa comata</i> (Trin. &amp; Rupr.) Barkworth, and <i>Bouteloua gracilis</i> (Willd. ex Kunth) Lag. ex Griffiths. Our second objective was to evaluate plant community development of both seeding mixes. We established seeding experiments on 3 field sites in central Alberta, Canada. When seeded as a monoculture, the <i>F. hallii</i> plant community that resulted included native species re-established from the seedbank or seed rain, such as <i>Helictotrichon hookeri</i> (Scribn.) Henr. (Poaceae). In the native species seed mix, wheatgrasses (<i>E. trachycaulus</i> ssp. <i>subsecundus</i> and <i>P. smithii</i>) dominated in the first 3 y with low <i>F. hallii</i> cover. We recommend seeding <i>F. hallii</i> with few or no aggressive species, such as wheatgrasses, in the seed mix.

Crop and Soil Responses to Using Corn Stover as a Bioenergy Feedstock: Observations from the Northern US Corn Belt

Corn (Zea mays L.) stover is a potential bioenergy feedstock, but little is known about the impacts of reducing stover return on yield and soil quality in the Northern US Corn Belt. Our study objectives were to measure the impact of three stover return rates (Full (~7.8 Mg ha−1 yr−1), Moderate (~3.8 Mg ha−1 yr−1) or Low (~1.5 Mg ha yr−1) Return) on corn and soybean (Glycine max. L [Merr.]) yields and on soil dynamic properties on a chisel-tilled (Chisel) field, and well- (NT1995) or newly- (NT2005) established no-till managed fields. Stover return rate did not affect corn and soybean yields except under NT1995 where Low Return (2.88 Mg ha−1) reduced yields compared with Full and Moderate Return (3.13 Mg ha−1). In NT1995 at 0–5 cm depth, particulate organic matter in Full Return and Moderate Return (14.3 g kg−1) exceeded Low Return (11.3 g kg−1). In NT2005, acid phosphatase activity was reduced about 20% in Low Return compared to Full Return. Also the Low Return had an increase in erodible-sized dry aggregates at the soil surface compared to Full Return. Three or fewer cycles of stover treatments revealed little evidence for short-term impacts on crop yield, but detected subtle soil changes that indicate repeated harvests may have negative consequences if stover removed.

Global genetic analysis reveals the putative native source of the invasive termite, Reticulitermes flavipes, in France

Biological invasions are recognized as a major threat to both natural and managed ecosystems. Phylogeographic and population genetic analyses can provide information about the geographical origins and patterns of introduction and explain the causes and mechanisms by which introduced species have become successful invaders. Reticulitermes flavipes is a North American subterranean termite that has been introduced into several areas, including France where introduced populations have become invasive. To identify likely source populations in the USA and to compare the genetic diversity of both native and introduced populations, an extensive molecular genetic study was undertaken using the COII region of mtDNA and 15 microsatellite loci. Our results showed that native northern US populations appeared well differentiated from those of the southern part of the US range. Phylogenetic analysis of both mitochondrial and nuclear markers showed that French populations probably originated from southeastern US populations, and more specifically from Louisiana. All of the mtDNA haplotypes shared between the United States and France were found in Louisiana. Compared to native populations in Louisiana, French populations show lower genetic diversity at both mtDNA and microsatellite markers. These findings are discussed along with the invasion routes of R. flavipes as well as the possible mechanisms by which French populations have evolved after their introduction.

Climate-change and mass mortality events in overwintering monarch butterflies

Monarch butterflies (Danaus plexippus) have a unique yearly life cycle, in which successive generations breed and move northward from the southern USA in spring to the northern US and southern Canada by late summer; they overwinter in extremely restricted areas in central Mexico and along the California coast. Mexican overwintering populations have experienced significant mortality events recently, which have been hypothesized as increasing in frequency owing to climate change. Here, we test the hypothesis of climate-change causation of these mortality events, at least in part, finding significant local weather trends toward conditions lethal for monarch survival. We use ecological niche estimates and future climate projections to estimate future overwintering distributions; results anticipate dramatic reductions in suitability of present overwintering areas, and serious implications for local human economies.

Spatial scaling of wildland fuels for six forest and rangeland ecosystems of the northern Rocky Mountains, USA

Wildland fuels are important to fire managers because they can be manipulated to achieve management goals, such as restoring ecosystems, decreasing fire intensity, minimizing plant mortality, and reducing erosion. However, it is difficult to accurately measure, describe, and map wildland fuels because of the great variability of wildland fuelbed properties over space and time. Few have quantified the scale of this variability across space to understand its effect on fire spread, burning intensity, and ecological effects. This study investigated the spatial variability of loading (biomass) across major surface and canopy fuel components in low elevation northern Rocky Mountain forest and rangeland ecosystems to determine the inherent scale of surface fuel and canopy fuel distributions. Biomass loadings (kg m−2) were measured for seven surface fuel components—four downed dead woody fuel size classes (0–6 mm, 6–25 mm, 25–75 mm, and 75 + mm), duff plus litter, shrub, and herb—using a spatially nested plot sampling design within a 1 km2 square sampling grid installed at six sites in the northern US Rocky Mountains. Bulk density, biomass, and cover of the forest canopy were also measured for each plot in the grid. Surface fuel loadings were estimated using a combination of photoload and destructive collection methods at many distances within the grid. We quantified spatial variability of fuel component loading using spatial variograms, and found that each fuel component had its own inherent scale with fine fuels varying at scales of 1–5 m, coarse fuels at 10–150 m, and canopy fuels from 100 to 500 m. Using regression analyses, we computed a scaling factor of 4.6 m for fuel particle diameter (4.6 m increase in scale with each cm increase in particle diameter). Findings from this study can be used to design fuel sampling projects, classify fuelbeds, and map fuel characteristics, such as loading, to account for the inherent scale of fuel distributions to get more accurate fuel loading estimations.