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The incorporation of cover crops into the maize (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation in the U.S. upper Midwest may improve sustainability. Long, cold winters in the region make identifying successful cover crop species and management practices a challenge. Two experiments were conducted in Minnesota, USA from fall 2016 through spring 2019 to examine the effect of cover crops interseeded at four- to six-leaf collar (early-interseeded) and dent to physiological maturity (late-interseeded) on biomass and grain yield of maize. Annual ryegrass (Lolium multiflorum L.) and cereal rye (Secale cereale L.) were evaluated as monocultures and in mixtures with crimson clover (Trifolium incarnatum L.) and forage radish (Raphanus sativus L.). Differences in canopy cover and biomass of late-interseeded cover crops were observed at the southernmost location in 2018. Additional accumulated growing-degree days in fall 2018 did not translate into increased cover crop canopy coverage of late-interseeded cover crops. Differences in cover crop canopy cover and biomass of early-interseeded cover crops were observed by fall frost at all locations in 2017 and at the northernmost location in 2018. Cover crop canopy cover and biomass at termination before planting maize, soil moisture at maize planting as well as maize aboveground biomass and yield were not affected by spring cereal rye regrowth of cover crops late-interseeded the previous year. Similarly, early-interseeded cover crops did not affect maize aboveground biomass or yield. We attribute these results to limited cover crop growth. This highlights the potential of a variety of cover crop strategies interseeded into maize in the U.S. upper Midwest; however, efforts to fine-tuning cover crop management and weather conditions are needed to benefit from such practice.

Predicting the potential habitat of species under both current and future climate change scenarios is crucial for monitoring invasive species and understanding a species' response to different environmental conditions. Frequently, the only data available on a species is the location of its occurrence (presence-only data). Using occurrence records only, two models were used to predict the geographical distribution of two destructive invasive termite species, Coptotermes gestroi (Wasmann) and Coptotermes formosanus Shiraki. The first model uses a Bayesian linear logistic regression approach adjusted for presence-only data while the second one is the widely used maximum entropy approach (Maxent). Results show that the predicted distributions of both C. gestroi and C. formosanus are strongly linked to urban development. The impact of future scenarios such as climate warming and population growth on the biotic distribution of both termite species was also assessed. Future climate warming seems to affect their projected probability of presence to a lesser extent than population growth. The Bayesian logistic approach outperformed Maxent consistently in all models according to evaluation criteria such as model sensitivity and ecological realism. The importance of further studies for an explicit treatment of residual spatial autocorrelation and a more comprehensive comparison between both statistical approaches is suggested.

Abstract This literature review was built upon recently published articles on Life Cycle Assessments (LCAs) of agricultural biogas plants, to: enhance understanding of the relevant literature in the field and the related question by readers worldwide. It was designed to highlight methodological issues and impact indicators, which best represent this research field; consequently, they should be considered in performing environmental assessments of agro-biogas derived energy systems. The literature review highlighted the wide variability of environmental results due to the ways the feedstock mixtures were produced, managed, and supplied; and due to the regions in which the anaerobic digesters were located and operated. Differences were found to be related to the aim and function of the study and to the methodological approach used, especially for the development of the environmental impact assessments. Other differences resulted from the ways the energy produced was utilised, whether it was used as an input to the natural gas national grid, and/or if it was used within the production system. The authors of this review concluded that, although much progress has been made, many unsolved challenges and methodological choices must be addressed to further improve the robustness of LCA in relation to AD and to related approaches.

Featured paper: See Editorial p553

ABSTRACT Playa wetlands in the Great Plains, USA support a wide variety of plant species not found elsewhere in this agriculturally-dominated region due to the ephemeral presence of standing water and hydric soils within playas. If longer dry periods occur due to climate change or if changes in surrounding land use alter sediment accumulation rates and water storage capacity in playas, plant communities could experience decreased diversity, with lasting effects on ecosystem services provided by playas in the Great Plains and at a continental-level in North America. We quantified potential changes in playa wetland plant community composition associated with predicted changes in precipitation and land use in the Great Plains through the end of the 21st century. We conducted two six-month greenhouse experiments mimicking field conditions using intact mesocosms collected from playas in Nebraska and Texas. In the precipitation experiment, treatments derived from historical precipitation observations and three future moderate emissions (CMIP5 RCP4.5) downscaled climate projections were applied to mesocosms. For the land use experiment, treatments were simulated by nitrogen (N) applications to soil ranging from 0 to 100 mg-N L-1 with each precipitation event under historical rainfall patterns, representing increasing and decreasing area in agricultural use in playa watersheds. Plant communities tended to shift toward more native species under projected future climate conditions, but as N runoff increased, native species richness decreased. Agricultural land-use surrounding playas may have a greater effect on wetland plant communities than future alterations to hydrology based on climate change in the Great Plains; thus, efforts to reduce nutrient runoff into playas would likely mitigate loss in ecosystem function in the coming decades.

The natural hydrology of streams and rivers is being extensively modified by human activities. Water diversion, dam construction, and climate change have the potential to increase the frequency and intensity of low-flow events. Flow is a dominant force structuring stream aquatic insect communities, but the impacts of water diversion are poorly understood. Here we report results of an experimental stream flow diversion designed to test how aquatic insect communities respond to a low-flow disturbance. We diverted 40% to 80% of the water in three replicate streams for three summers, leading to summer flow exceedance probabilities of up to 99.9%. Shifts in habitat availability appeared to be a major driver of aquatic insect community responses. Responses also varied by habitat type: total insect density decreased in riffle habitats, but there was no change in pool habitats. Overall, the total biomass of aquatic insects decreased sharply with lowered flow. Collector-filterers, collector-gatherers, and scrapers were especially susceptible, while predatory insects were more resistant. Despite extremely low flow levels, there was no shift in aquatic insect family richness. The experimental water withdrawal did not increase water temperature or decrease water quality, and some wetted habitat was always maintained, which likely prevented more severe impacts on aquatic insect communities.

Mountain regions are experiencing some of the highest air temperature increases and ice cover decreases. However, few studies have examined the effects of climate warming and earlier snowmelt on mountain lake thermal characteristics and energetic implications for fish. We assessed potential climate-induced thermal changes and energetic consequences for cutthroat trout (Oncorhynchus clarkii spp.) and brook trout (Salvelinus fontinalis) in the Southern Rocky Mountains, United States. We found that summer growing degree days increased by an average 21 percent with 2°C air warming and 43 percent with 5°C air warming. But earlier snowmelt increased growing degree days by an average 48 percent. The average maintenance ration with 2°C and 5°C warming increased respectively by 13.8 and 21.9 percent for cutthroat trout and 23.8 and 37.4 percent for brook trout. The average increase in food required with earlier snowmelt was 43.4 percent for cutthroat trout and 52.3 percent for brook trout. Thus, earlier snowmelt can have a greater effect on fish energy requirements than a 5°C rise in air temperatures. Snowmelt recession together with a 5°C air temperature rise could more than double food requirements for fish to maintain constant body weight. If lake productivity increases with these climatic changes, then trout growth could improve; otherwise, energetic demands may result in lower fish growth.

Abstract Survival, height and diameter for the first four year rotation were measured on two intensively cultured Populus hybrid plantations in central Pennsylvania. Treatments of control, irrigation, fertilization and fertilization/irrigation were installed on two sites and in two establishment years. Overall treatment survival was not affected by site but values were lower for 1980 planted trees (83%) than 1981 planted trees (90%). Survival values among the treatments were similar until the later ages of the first rotation. Treatments with fertilizers had lower four-year-old survival (78%) than the treatments without fertilizers (86%). The four-year-old control trees averaged 5.3 and 6.8 m in height, and 3.4 and 4.2 cm in diameter for the 1980 and 1981 establishment years, respectively. Fertilization, with or without irrigation, consistently increased annual height and diameter over the control. Fertilization/irrigation did not result in tree size values that were greater than fertilization. In general, there were inconsistent increases in annual height and diameter from irrigation.