Abstract  Global climate change (GCC) is likely to alter the degree of human exposure to pollutants and the response of human populations to these exposures, meaning that risks of pollutants could change in the future. The present study, therefore, explores how GCC might affect the different steps in the pathway from a chemical source in the environment through to impacts on human health and evaluates the implications for existing risk-assessment and management practices. In certain parts of the world, GCC is predicted to increase the level of exposure of many environmental pollutants due to direct and indirect effects on the use patterns and transport and fate of chemicals. Changes in human behavior will also affect how humans come into contact with contaminated air, water, and food. Dietary changes, psychosocial stress, and coexposure to stressors such as high temperatures are likely to increase the vulnerability of humans to chemicals. These changes are likely to have significant implications for current practices for chemical assessment. Assumptions used in current exposure-assessment models may no longer apply, and existing monitoring methods may not be robust enough to detect adverse episodic changes in exposures. Organizations responsible for the assessment and management of health risks of chemicals therefore need to be more proactive and consider the implications of GCC for their procedures and processes. Environ. Toxicol. Chem. 2013;32:6278. (c) 2012 SETAC

Abstract  Despite rapid growth in biofuel production worldwide, it is uncertain whether decision-makers possess sufficient information to fully evaluate the impacts of the industry and avoid unintended consequences. Doing so requires rigorous peer-reviewed data and analyses across the entire range of direct and indirect effects. To assess the coverage of scientific research, we analyzed over 1600 peer-reviewed articles published between 2000 and 2009 that addressed 23 biofuels-related topics within four thematic areas: environment and human well-being, economics, technology, and geography. Greenhouse gases, fuel production, and feedstock production were well-represented in the literature, while trade, biodiversity, and human health were not. Gaps were especially striking across topics in the Southern Hemisphere, where the greatest potential socio-economic benefits, as well as environmental damages, may co-occur. There was strong asymmetry in the connectedness of research topics; greenhouse gases articles were twice as often connected to other topics as biodiversity articles. This could undermine the ability of scientific and economic analyses to adequately evaluate impacts and avoid significant unintended consequences. At the least, our review suggests caution in this developing industry and the need to pursue more interdisciplinary research to assess complex trade-offs and feedbacks inherent to an industry with wide-reaching potential impacts.

Abstract  There is considerable interest in both soy and canola as biodiesel feedstock crops because of the net reduction in CO2 emissions resulting from the use of biodiesel in place of petroleum diesel. Whether these two crops differ in net CO2 savings is unknown, in part because of our ignorance of their impact on soil C. We, therefore, monitored soil C for three years in an experiment that included both soy and canola rotations. We found that soil C concentrations were significantly lower under canola than soy, and that the difference represented as much as 64% of the C savings of soy biodiesel over petroleum diesel. We tested two hypotheses that could explain this difference in soil C. First, because canola can acidify the soil, we determined whether a reduction in inorganic C (as carbonate) in canola plots could account for the soil C difference. Carbonate concentration did not differ significantly in soy and canola plots. Second, we determined whether soil organic matter concentration could account for the soil C difference. Soil organic matter concentration was significantly lower in canola than in soy plots, accounting for the difference in soil C. We further hypothesized that because soy is mycorrhizal and canola is not, soy soils should contain higher concentrations of glomalin, a recalcitrant substance produced by mycorrhizal fungi, and that this could help to explain the difference in soil organic matter. Glomalin concentrations were significantly lower in canola plots, but this difference accounted for only a fraction of the total soil C difference. Our results suggest that a proper accounting of life cycle C savings of biodiesel when used in place of petroleum diesel must consider soil C. (C) 2012 Elsevier GmbH. All rights reserved.

Abstract  Nutrient concentrations and phytoplankton biomass were monitored with reference to several anthropogenic pressures in the Karamenderes River (Canakkale, NW Turkey) and in its catchment through a seasonal sampling program of three sites. Both spatial and temporal variations in chl a, nitrate and nitrite and temporal variation in ammonium, phosphate and silicate were significant. Despite intense application of chemical fertilizers in agricultural areas within the catchment and elevated riverine nitrate concentrations phosphate levels were low, potentially keeping chl. a levels in oligotrophic range. Considering the important role of phosphorus in freshwater eutrophication and complex dynamics of phosphorus leaching from soil, the healthy functioning of this ecosystem critically depends on management plans that consider the long term risks associated with phosphate transfer from agricultural soils into the river.

Abstract  Estimates of carbon leaching losses from different land use systems are few and their contribution to the net ecosystem carbon balance is uncertain. We investigated leaching of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and dissolved methane (CH4), at forests, grasslands, and croplands across Europe. Biogenic contributions to DIC were estimated by means of its δ13C signature. Leaching of biogenic DIC was 8.3±4.9 g m−2 yr−1 for forests, 24.1±7.2 g m−2 yr−1 for grasslands, and 14.6±4.8 g m−2 yr−1 for croplands. DOC leaching equalled 3.5±1.3 g m−2 yr−1 for forests, 5.3±2.0 g m−2 yr−1 for grasslands, and 4.1±1.3 g m−2 yr−1 for croplands. The average flux of total biogenic carbon across land use systems was 19.4±4.0 g C m−2 yr−1. Production of DOC in topsoils was positively related to their C/N ratio and DOC retention in subsoils was inversely related to the ratio of organic carbon to iron plus aluminium (hydr)oxides. Partial pressures of CO2 in soil air and soil pH determined DIC concentrations and fluxes, but soil solutions were often supersaturated with DIC relative to soil air CO2. Leaching losses of biogenic carbon (DOC plus biogenic DIC) from grasslands equalled 5–98% (median: 22%) of net ecosystem exchange (NEE) plus carbon inputs with fertilization minus carbon removal with harvest. Carbon leaching increased the net losses from cropland soils by 24–105% (median: 25%). For the majority of forest sites, leaching hardly affected actual net ecosystem carbon balances because of the small solubility of CO2 in acidic forest soil solutions and large NEE. Leaching of CH4 proved to be insignificant compared with other fluxes of carbon. Overall, our results show that leaching losses are particularly important for the carbon balance of agricultural systems.

Abstract  Increasing demand for transport fuels has driven China to attach great importance to biodiesel development. To evaluate the environmental impacts caused by producing and driving with biodiesel made from soybean, jatropha, and microalgae under China conditions, the LCA methodology is used and the assessment results are compared with fossil diesel. The solar energy and CO(2) uptake in biomass agriculture and reduction of dependency on fossil fuels lead to a better performance on abiotic depletion potential (ADP), global warming potential (GWP), and ozone depletion potential (ODP) in the life cycle of biodiesel compared to fossil diesel. Except for ADP, GWP and ODP, producing and driving with biodiesel does not offer benefits in the other environmental impact categories including eutrophication, acidification, photochemical oxidation, and toxicity. Jatropha and microalgae are more competitive biodiesel feedstock compared to soybean in terms of all impacts. By using global normalization references and weighting method based on ecotaxes, the LCA single score for the assessed 10 mid-point impact categories of soybean, jatropha, and microalgae based biodiesel is 54, 37.2 and 3.67 times of that of fossil diesel, respectively. Improvement of biomass agriculture management, development of biodiesel production technologies, bettering energy structure and promoting energy efficiency in China are the key measures to lower environmental impacts in the life cycle of biodiesel in the future. Various sensitivity analyses have also been applied, which show that, choice of allocation method, transport distance, uncertainty in jatropha and microalgae yield and oil content, and recycling rate of harvest water of microalgae have significant influence on the life cycle environmental performance of biodiesel. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  Large-scale production of feedstock crops for biofuels will lead to land use changes. We quantify the effects of realistic land use change scenarios for biofuel feedstock production on isoprene emissions and hence atmospheric composition and chemistry using the HadGEM2 model. Two feedstocks are considered: oil palm for biodiesel in the tropics and short rotation coppice (SRC) in the mid-latitudes. In total, 69 Mha of oil palm and 92 Mha of SRC are planted, each sufficient to replace just over 1% of projected global fossil fuel demand in 2020. Both planting scenarios result in increases in total global annual isoprene emissions of about 1%. In each case, changes in surface concentrations of ozone and biogenic secondary organic aerosol (bSOA) are substantial at the regional scale, with implications for air quality standards. However, the changes in tropospheric burden of ozone and the OH radical, and hence effects on global climate, are negligible. Over SE Asia, one region of oil palm planting, increases in annual mean surface ozone and bSOA concentrations reach over 3 ppbv (+11 %) and 0.4 mu g m(-3) (+10 %) respectively for parts of Borneo, with monthly mean increases of up to 6.5 ppbv (+25 %) and 0.5 mu g m(-3) (+12 %). Under the SRC scenario, Europe experiences monthly mean changes of over 0.6 ppbv (+1 %) and 0.1 mu g m(-3) (+5 %) in June and July, with peak increases of over 2 ppbv (+3 %) and 0.5 mu g m(-3) (+8 %). That appreciable regional atmospheric impacts result from low level planting scenarios demonstrates the need to include changes in emissions of reactive trace gases such as isoprene in life cycle assessments performed on potential biofuel feedstocks.

Abstract  Current methods of estimating potential environmental impacts of metals in hazard and Life Cycle Impact Assessment (LCIA) do not consider differences in chemistry and landscape properties between geographic sites. Here, we developed and applied a model for regional aquatic impact characterization of metals using an updated method for estimating environmental fate factor (FF), bioavailability factor (BF) and aquatic ecotoxicity factor (EF). We applied the model to analyze differences in Comparative Toxicity Potentials (CTPs) of Cu, Ni and Zn for 24 Canadian ecoregions. The combined impacts of regional variability in ambient chemistry (in particular DOC, pH and hardness) and landscape properties (water residence time) can change the CTPs of these metals for freshwater by up to three orders of magnitude and change the relative ranking of metal hazard between ecoregions. Variation among Canadian freshwater chemistries and landscape characteristics influence the FFs within two orders of magnitude, BFs within two orders of magnitude for Ni and Zn and four orders of magnitude for Cu, and EFs within one order of magnitude. Sensitivity of metal FFs to environmental parameters alone spans three orders of magnitude when a constant water chemistry was used for all ecoregions. These results indicate that application of regionalised metal CTPs can have a significant influence in the analysis of ecotoxicological impacts in the life cycle assessment of products and processes.

Abstract  Ambitious targets for the use of renewable energy have recently been set in the European Union. To reach these targets, a large share of future energy generation will be based on the use of woody biomass. Therefore, there is an increasing interest in the cultivation of fast-growing tree species on agricultural land outside forests. Intensive crop production is always considered to harm the environment. The study explores the environmental burdens of the cultivation of fast-growing tree species on agricultural land and their subsequent energetic conversion in comparison to the fossil reference energy system. Life cycle assessment (LCA) methodology according to the ISO 14040 and 14044 is used. Input data were partly collected within the German joint research project AGROWOOD. Two utilization paths of short rotation poplar chips are analyzed: heat and power generation in a cogeneration plant and the production of Fischer-Tropsch (FT) diesel. Subsequently, the bioenergy systems are compared with their fossil references. The production and distribution of 1 oven dry tonne (odt) of short-rotation poplar chips require 432 MJ non-renewable energy. This equals an output-input ratio of 43:1, which includes all process steps from field preparation to road transport. Emissions of this energy use amount to a global warming potential of 38.4 kg CO(2) eq odt(-1), an acidification potential of 0.24 kg SO(2) eq odt(-1), and a eutrophication potential of 0.04 kg PO(4) eq odt(-1). The greatest reductions of environmental impacts can be achieved by substituting power from lignite with cogenerated power from short-rotation coppice (SRC). Compared with the average German power generation mix GWP and AP of power generation from short rotation poplar chips are lower by 97% and 44%, respectively, while eutrophication potential is about 26% higher. FT diesel made from short-rotation poplar chips has an 88% lower global warming potential and a 93% lower acidification potential than fossil diesel. But, the eutrophication potential of FT diesel is twice as high as of fossil diesel. It was found that even intensively produced wood from SRC can reduce environmental burdens if it is used for biofuel instead of fossil fuel. The utilization of the same amount of short-rotation poplar chips for heat and power production causes fewer environmental impacts than its use for FT diesel.

Abstract  The objective of this study was to integrate process life cycle assessment (LCA) into an activity-based microeconoinic model of production to quantify environmental impacts induced by economic incentives imposed on individual producers. The economic incentives may include price changes, technological innovations and governmental taxes/subsidies that are beyond the scope of Input-Output-based LCA. In this approach, however, traditional normative activity analysis hardly reproduces the observed input variables referred to as ""reference point"", as is often the case with linear programming model widely used for farm management. Consequently, the resultant LCA deviates from the original LCA that is evaluated at the reference point. This study made an attempt to bridge the gap between the theoretically derived LCA and the original process LCA by introducing the positive mathematical programming (PMP) approach, which was established by Howitt. The PMP-based LCA was applied to conventional and reduced tillage farming systems in Hokkaido, northern Japan, to consider its potential for analyzing an area-based farm policy and to discuss several limitations to be addressed in future research.

Abstract  Human activities have changed the composition of the atmosphere resulting in rising global temperatures and sea levels. Agriculture contributes significantly to climate change through the emission of the greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Continuation of the trends of greenhouse gas emissions will result in a further increase of global warming in the coming decades. The most recent projections indicate a global warming of 1.1-6.4 degrees C by the year 2100, but in North Western Europe warming is expected to be even higher. This will result in a sea-level rise of up to 0.8 m by the year 2100. Field vegetable production systems contribute to climate change through emission of the greenhouse gases CO2 and N2O. Since field vegetables like all other plants fix atmospheric CO2, the net emission of CO2 from vegetable production systems will be insignificant, especially when high-yielding varieties are used, crop residues are not removed from the field, inorganic fertilizers are replaced by organic manures and reduced tillage is applied. N2O emission can be reduced by increasing the efficiency of N use by the vegetables. Field vegetable production systems will have to adapt to changing weather conditions, such as dryer summers and wetter winters. This implies that crops or varieties have to be used that are more stress tolerant to drought and salinity.

Abstract  The use of ethanol as a transportation fuel in the U.S. increased significantly from 20002009, and in 2010 nearly all gasoline contained 10% ethanol. In accordance with this increased use, atmospheric measurements of volatile organic compounds in Los Angeles in 2010 were significantly enriched in ethanol compared to measurements in urban outflow in the Northeast U.S. in 2002 and 2004. Mixing ratios of acetaldehyde, an atmospheric oxidation product of ethanol, decreased between 2002 and 2010 in Los Angeles. Previous work has suggested that large-scale use of ethanol may have detrimental effects on air quality. While we see no evidence for this in the U.S., our study indicates that ethanol has become a ubiquitous compound in urban air and that better measurements are required to monitor its increase and effects.

Abstract  Essential sustainability requirements for biodiesel are that the product should be truly renewable and have a lower negative environmental impact than fossil fuels based on the latest insights. Biodiesel is not a most sustainable product in all geographical circumstances. This survey paper reviews the performance and prospects of rape biodiesel production on a global basis using some 40 life cycle assessments (LCAs). The paper identifies best (agricultural) practice and laggards. Life cycle energy balance depends on specific climatic conditions, and the agro- and processing technologies used. Alternative oilcrop cultivation practices and technologies were assessed. Opportunities to improve rape biodiesel life cycle energy efficiency and environmental impact by implementing new technologies in agriculture as well as in industrial processing have been identified for various Brassica oilcrop cultivars in relevant production areas. The consequences of large-scale renewable energy action plans have been considered. Improvements are needed for rape biodiesel to stay in business. The paper concludes with perspectives and recommendations. (C) 2012 Elsevier Ltd. All rights reserved.

Abstract  Global climate change, driven by the buildup of greenhouse gas (GHG) emissions in the atmosphere, is challenging the dairy industries in the United States and throughout the world to develop sustainable initiatives to reduce their environmental impact. The U.S. dairy industry has committed to lowering the GHG emissions, primarily CH(4), N(2)O, and CO(2), in each sector of the fluid milk supply chain which extends from the farm, to the processing plant, and to distribution of the packaged product, where it is refrigerated by the retailer and then the consumer. This chapter provides an overview of the life cycle analysis (LCA) technique and its use in identifying the GHG emissions in each sector of the fluid milk supply chain, from cradle to grave, and the best practices and research that is currently being conducted to reduce or mitigate GHG emissions in each sector. We also discuss the use of on-farm and off-farm process simulation as tools for evaluating on-farm mitigation techniques, off-farm alternative processing scenarios, and use of alternative energy management practices.

Abstract  We have evaluated the global warming impact of palm oil production in a model that simulates the operations of a typical palm oil mill that processes fruit from a nucleus estate and outgrowers. It estimates carbon sequestration in the crop and in mill products and by-products, and balances this against the major sources of greenhouse gases (GHGs), all converted to carbon dioxide equivalents (CO(2)-e) over the 25-year lifespan of the crop. The model shows that most carbon sequestration occurs in the standing crop, with smaller amounts in mill products and by-products. Land-use conversion plays a dominant role in the GHG budget, with planting of oil palm after logged forest or rubber leading to a net loss of carbon, and to a net gain following grassland. In the default oil-palm-to-oil-palm case the carbon lost from cleared palms is balanced by sequestration in the current crop. Methane from mill effluent and nitrous oxide from N fertilizers are the next most important emission sources. The default replant case gives net emissions of 0.86t CO(2)-e per t crude palm oil, but these can be reduced to very low values, mainly through conversion of methane and surplus fuel in the mill to energy.

Abstract  Nitrogen (N)-fixing tree and crop intercropping systems can be a sustainable agricultural practice in sub-Saharan Africa and can also contribute to resolving climate change through enhancing soil carbon (C) sequestration. A study conducted by Makumba et al. (Agric Ecosyst Environ 118:237-243, 2007) on the N-fixing tree gliricidia and maize intercropping system in southern Malawi provides a rare dataset of both sequestered soil C and C loss as soil carbon dioxide (CO2) emissions. However, no soil C gain and loss estimates were made so the study failed to show the net gain of soil C. Also absent from this study was potential benefit or negative impact related to the other greenhouse gas, nitrous oxide (N2O) and methane (CH4) emissions from the intercropping system. Using the data provided in Makumba et al. (Agric Ecosyst Environ 118:237-243, 2007) a C loss as soil CO2 emissions (51.2 +/- A 0.4 Mg C ha(-1)) was estimated, amounting to 67.4% of the sequestered soil C (76 +/- A 8.6 Mg C ha(-1) in 0-2 m soil depth) for the first 7 years in the intercropping system. An annual net gain of soil C of 3.5 Mg C ha(-1) year(-1) was estimated from soil C sequestered and lost. Inclusion of the potential for N2O mitigation [0.12-1.97 kg N2O-N ha(-1) year(-1), 0.036-0.59 Mg CO2 equivalents (eq.) ha(-1) year(-1)] within this intercropping system mitigation as CO2 eq. basis was estimated to be 3.5-4.1 Mg CO2 eq. ha(-1) year(-1). These results suggest that reducing N2O emission can significantly increase the overall mitigation benefit from the intercropping system. However, significant uncertainties are associated with estimating the effect of intercropping on soil N2O and CH4 emissions. These results stress the importance of including consideration of quantifying soil CO2, N2O and CH4 emissions when quantifying the C sequestration potential in intercropping system.

Abstract  States are working to comply with the ozone National Ambient Air Quality Standards (NAAQS). Often, regulations restricting vehicle emissions are promulgated in order to attain compliance with the NAAQS. Currently, more stringent vehicle emission regulations are being considered by government agencies. This paper compares emissions from passenger cars and light duty trucks under the current California Low Emission Vehicle (LEV II) standards to a control scenario which was anticipated in 2008 to become LEV Ill (referred to as "more stringent control" in this paper) and determines if the scenario would result in additional improvements to air quality in California's South Coast Air Basin. The air quality modeling was performed using the Community Multi-scale Air Quality Model (CMAQ) for years 2005, 2014 and 2020.

The more stringent control sensitivity study simulated a scenario in which all new passenger cars and light duty trucks in the California South Coast Air Basin in year 2016 achieve Super Ultra-Low Emission Vehicle (SULEV) tail pipe emissions, zero evaporative emissions and more stringent aggressive driving requirements.

The total on-road vehicles emissions difference when averaged across the South Coast Air Basin showed the more stringent scenario compared to LEV II to have reductions of 1% for oxides of nitrogen (NOx), 1% for as reactive organic gases (ROG) and 5% for carbon monoxide (CO) in 2030.

LEV II modeled ozone levels in the western areas of the basin increased in 2014 and 2020 as compared to 2005, because these areas are VOC-sensitive and the reductions in NOx emissions in these regions are larger than the VOC reductions. In other areas of the South Coast Basin, ozone is reduced by 1.5% or less. The more stringent control scenario modeled levels of ozone have a maximum decrease from LEV II levels by 1% or less in 2014 and 1.5% or less in 2020. (C) 2011 Elsevier Ltd. All rights reserved.

Abstract  The environmental health impacts of transportation depend in part on where and when emissions occur during fuel production and combustion. Here we describe spatially and temporally explicit life cycle inventories (LCI) of air pollutants from gasoline, ethanol derived from corn grain, and ethanol from corn stover. Previous modeling for the U.S. by Argonne National Laboratory (GREET: Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation) suggested that life cycle emissions are generally higher for ethanol from corn grain or corn stover than for gasoline. Our results show that for ethanol, emissions are concentrated in the Midwestern "Corn Belt". We find that life cycle emissions from ethanol exhibit different temporal patterns than from gasoline, reflecting seasonal aspects of farming activities. Enhanced chemical speciation beyond current GREET model capabilities is also described. Life cycle fine particulate matter emissions are higher for ethanol from corn grain than for ethanol from corn stover; for black carbon, the reverse holds. Overall, our results add to existing state-of-the-science transportation fuel LCI by providing spatial and temporal disaggregation and enhanced chemical speciation, thereby offering greater understanding of the impacts of transportation fuels on human health and opening the door to advanced air dispersion modeling of fuel life cycles.

Abstract  Agricultural soils are a significant anthropogenic source of nitrous oxide (N2O) to the atmosphere. Despite likely having large emissions of N2O, there are no continuous multi-year studies of emissions from poorly drained floodplain soil. In the present study, the micrometeorological flux of N2O (E-N) was measured over three years (2006-2008) in a maize (Zea mays L.)/faba (Vicia faba minor L.)/spring-wheat (Triticum aestivum L) rotation in the Red River Valley, Manitoba, Canada on a gleyed humic verticol soil. Comparison of newly established reduced and intensive tillage treatments showed no difference in F-N within the constraints of the high variability between duplicate plots. The annual gap-filled Sigma F-N across tillage treatments was 5.5, 1.4, and 4.3 kg N ha(-1) in the maize, faba, and spring-wheat crop years, respectively. Emissions from fertilizer N addition and soil thaw the following spring was responsible for the greater Sigma F-N in the maize and spring-wheat years. Using four approaches to approximate background Sigma F-N resulted in estimates of 3.5-3.8% and 1.4-1.8% of applied fertilizer N emitted as N2O for the maize and spring-wheat crops, respectively. The CO2 global warming potential equivalent of Sigma F-N over the three study years was an emission of 5.4 Mg CO2-equiv. ha(-1) which adds to the previously determined C balance emission of 11.6 Mg CO2-equiv. ha(-1). (c) 2012 Elsevier B.V. All rights reserved.

Abstract  Using forests to mitigate climate change has gained much interest in science and policy discussions. We examine the evidence for carbon benefits, environmental and monetary costs, risks and trade-offs for a variety of activities in three general strategies: (1) land use change to increase forest area (afforestation) and avoid deforestation; (2) carbon management in existing forests; and (3) the use of wood as biomass energy, in place of other building materials, or in wood products for carbon storage. We found that many strategies can increase forest sector carbon mitigation above the current 162-256 Tg C/yr, and that many strategies have co-benefits such as biodiversity, water, and economic opportunities. Each strategy also has trade-offs, risks, and uncertainties including possible leakage, permanence, disturbances, and climate change effects. Because approximately 60% of the carbon lost through deforestation and harvesting from 1700 to 1935 has not yet been recovered and because some strategies store carbon in forest products or use biomass energy, the biological potential for forest sector carbon mitigation is large. Several studies suggest that using these strategies could offset as much as 10-20% of current U.S. fossil fuel emissions. To obtain such large offsets in the United States would require a combination of afforesting up to one-third of cropland or pastureland, using the equivalent of about one-half of the gross annual forest growth for biomass energy, or implementing more intensive management to increase forest growth on one-third of forestland. Such large offsets would require substantial trade-offs, such as lower agricultural production and non-carbon ecosystem services from forests. The effectiveness of activities could be diluted by negative leakage effects and increasing disturbance regimes. Because forest carbon loss contributes to increasing climate risk and because climate change may impede regeneration following disturbance, avoiding deforestation and promoting regeneration after disturbance should receive high priority as policy considerations. Policies to encourage programs or projects that influence forest carbon sequestration and offset fossil fuel emissions should also consider major items such as leakage, the cyclical nature of forest growth and regrowth, and the extensive demand for and movement of forest products globally, and other greenhouse gas effects, such as methane and nitrous oxide emissions, and recognize other environmental benefits of forests, such as biodiversity, nutrient management, and watershed protection. Activities that contribute to helping forests adapt to the effects of climate change, and which also complement forest carbon storage strategies, would be prudent.

Abstract  Agricultural ecosystems have been viewed with the potential to sequester atmospheric carbon dioxide (CO(2)) by increasing soil organic carbon (SOC) through reduced tillage and cover cropping practices. There remains considerable uncertainty, however, regarding the carbon (C) sink/source potential of these systems and few studies have examined C dynamics in conjunction with other important greenhouse gases. The objective of this study was to evaluate the impact of an alternative management scenario (reduced tillage and cover cropping) on ecosystem respiration (RE) and nitrous oxide (N(2)O) and methane (CH(4)) fluxes in a maize (Zea mays L.)/soybean (Glycine max L) rotation ecosystem in east-central Minnesota, United States. The control treatment was managed using fall tillage with a chisel plow in combination with a tandem disk, and the experimental treatment was managed using strip tillage and a winter rye (Secal cereale) cover crop. Over the two-year study period (2004-2005), cumulative RE was 222.7 g C m(-2) higher in the alternatively managed treatment as a result of increased decomposition of the cover crop residue. N(2)O fluxes were similar in both treatments during the 2004 growing season and were 100.1 mg N m(-2) higher in the conventional treatment during the 2005 growing season after nitrogen (N) fertilization. N fertilization and fertilizer type were the dominant factors controlling N(2)O fluxes in both treatments. CH(4) fluxes were negligible in both treatments and often below the detection limit. Cumulative growing season N(2)O losses in the control and experimental treatments, which totalled 38.9 +/- 3.1 and 26.1 +/- 1.7 g C m(-2) when converted to CO(2) equivalents, were comparable to the annual estimates of net ecosystem CO(2) exchange in both treatments. This study further supports that N(2)O losses are an important component of the total greenhouse gas budget of agroecosystems. It also suggests that spring cover cropping, without residue removal, has limited C sequestration potential. The results from this study, however, may not necessarily represent equilibrium conditions in the experimental treatment. Rather, they are a measure of the transient response of the system after tillage conversion and cover crop addition. It is expected that the soil microbes will continue to adjust to the reduction in tillage and increased C inputs. Therefore, continued, long-term monitoring is needed to confirm whether the results are representative of equilibrium conditions. (C) 2009 Elsevier B.V. All rights reserved.

Abstract  Greenhouse gas emissions (GHG) were simulated from commonly used crop rotations in eastern Poland for conventional and conservation tillage systems. We used denitrification-decomposition (DNDC) model baseline climate conditions and two future climate scenarios (2030 and 2050). Analyzed cropping systems included corn, rapeseed, and spring and winter wheat. It has been shown that an increase of temperature and decrease of precipitation can reduce net global warming potential (GWP) by 2% in the 2030 climate scenario and by 5% in the 2050 scenario in conventional tillage with reference to the baseline scenario. In the case of conservation tillage, a reduction of GWP by 5% and by 10% was estimated. The use of conservation tillage results decrease the GWP by 17-19% in the baseline scenario, in the 2030 scenario by 16- 18%, and in the 2050 scenario by 15-17%. It also has been shown that change in climate conditions has declined biomass production of winter wheat and corn, which may suggest that a larger area would be needed for these crops to maintain production at the same level.

Abstract  The relationships between soil microbial properties and nitrous oxide emission were examined in upland soil under different tillage systems [no tillage (NT), rotary and plow tillage] and cover crop systems (fallow, cereal rye, and hairy vetch) in 2004 and 2005. Microbiological analyses included the determination of soil ergosterol as an indicator of fungal biomass, bacterial plate counting, and MPN estimations of ammonia oxidizers and denitrifiers. The combined practice of NT with rye-cover crop treatment increased fungal biomass but not bacterial populations in 0-10 cm deep soils. Such increase in fungal biomass was not found in 10-20 cm and 20-30 cm deep cover-cropped NT soil. The combined practice of NT with rye-cover cropping resulted in higher in situ N(2)O emission rates compared with rotary- and plow-till treatments. N(2)O flux was positively correlated with soil ergosterol content but not with denitrifier MPN and other soil chemical properties. These results suggested a significant contribution of fungi to N(2)O emission in cover-cropped NT soils.

Abstract  We critically review recent literature on carbon storage and fluxes within natural and constructed freshwater wetlands, and specifically address concerns of readers working in applied science and engineering. Our purpose is to review and assess the distribution and conversion of carbon in the water environment, particularly within wetland systems. A key aim is to assess if wetlands are carbon sinks or sources. Carbon sequestration and fluxes in natural and constructed wetlands located around the world has been assessed. All facets of carbon (solid and gaseous forms) have been covered. We draw conclusions based on these studies. Findings indicate that wetlands can be both sources and sinks of carbon, depending on their age, operation, and the environmental boundary conditions such as location and climate. Suggestions for further research needs in the area of carbon storage in wetland sediments are outlined to facilitate the understanding of the processes of carbon storage and removal and also the factors that influence them.

Abstract  Tadpoles of the barking tree frog, Hyla gratiosa, are abundant in spring and summer in some ponds and Carolina bays on the Savannah River Plant near Aiken, South Carolina. To determine how these tadpoles survive in the presence of predaceous salamander larvae, Ambystoma talpoideum, and larvae of an aeshnid dragonfly, Anax junius, we determined fields densities and sizes of the predators and the prey and conducted predation experiments in the laboratory. Tadpoles rapidly grow to a size not captured by Ambystoma, although Anax larvae can capture slightly larger tadpoles. Differing habitat preferences among the tadpoles and the two predator species probably aid in reducing predation pressure. Preliminary work indicates that the tadpoles may have an immobility response to an attack by a predator. In addition, the smallest, most vulnerable tadpoles have a distinctive color pattern which may function to disrupt the body outline and make them indiscernable to predators.