Abstract  Soil organic matter dynamics following land-use change remain difficult to predict because of the complex biological, physical, and chemical mechanisms that control C turnover. We examined twelve sites, representing four broad land-use types (cultivated agriculture, pine forest, hardwood forest, and pasture), in the South Carolina Piedmont to determine whether variation in organic matter chemistry was linked to management, soil edaphic properties, microbial communities, or labile C. Organic matter chemistry was determined before and after a 232-d incubation using pyrolysis gas chromatography/mass spectroscopy and microbial community properties were determined prior to incubation by measuring extracellular enzyme activities, fungal: bacterial ratios by quantitative polymerase chain reaction (PCR), and microbial biomass. There was considerable variation in soil organic matter chemistry among the 12 sites but this could not be attributed to broad differences in land use, per se, likely because of the variation in edaphic soil properties and specific management practices within the individual land use categories. The relative abundance of N-containing compounds was correlated with the size of the labile C pool (r = 0.65). Further, the three most abundant N-containing pyrolysis products, pyridine, pyrrole, and indole, were also positively correlated with at least two enzymes and both pyridine and pyrrole were negatively correlated with fungal: bacterial ratios. In contrast, the relative abundances of lignin derivatives were often negatively correlated with enzyme activities but positively correlated with fungal: bacterial ratios. Post-incubation, silt plus clay content was negatively correlated with lignin derivatives (r = -0.68) and positively correlated with N-containing compounds (r=0.69). Our results suggest that broad land use categories are a poor predictor of soil organic matter chemistry when edaphic soil properties and specific management practices vary. However, enzyme activities, fungal: bacterial ratios, and soil texture correlate with soil organic matter chemistry across a range of ecosystems, suggesting that interactions between microbial communities and soil organic matter chemistry are important controls on soil C dynamics across landscapes. (C) 2009 Elsevier B.V. All rights reserved.

Abstract  The use of Penman-Monteith (PM) equation in thermal remote sensing based surface energy balance modeling is not prevalent due to the unavailability of any direct method to integrate thermal data into the PM equation and due to the lack of physical models expressing the surface (or stomatal) and boundary layer conductances (g(S) and g(B)) as a function of surface temperature. Here we demonstrate a new method that physically integrates the radiometric surface temperature (T-S) into the PM equation for estimating the terrestrial surface energy balance fluxes (sensible heat, H and latent heat, lambda E). The method combines satellite T-S data with standard energy balance closure models in order to derive a hybrid closure that does not require the specification of surface to atmosphere conductance terms. We call this the Surface Temperature Initiated Closure (STIC), which is formed by the simultaneous solution of four state equations. Taking advantage of the psychrometric relationship between temperature and vapor pressure, the present method also estimates the near surface moisture availability (M) from T-S, air temperature (T-A) and relative humidity (R-H), thereby being capable of decomposing lambda E into evaporation (lambda E-E) and transpiration (lambda E-T). STIC is driven with T-S, T-A, R-H, net radiation (R-N), and ground heat flux (G). T-S measurements from both MODIS Terra (MOD11A2) and Aqua (MYD11A2) were used in conjunction with FLUXNET R-N, G, T-A, R-H, lambda E and H measurements corresponding to the MODIS equatorial crossing time. The performance of STIC has been evaluated in comparison to the eddy covariance measurements of lambda E and H at 30 sites that cover a broad range of biomes and climates. We found a RMSE of 37.79 (11%) (with MODIS Terra T-S) and 44.27 W m(-2) (15%) (with MODIS Aqua T-S) in lambda E estimates, while the RMSE was 37.74(9%) (with Terra) and 44.72 W m(-2) (8%) (with Aqua) in H. STIC could efficiently capture the lambda E dynamics during the dry down period in the semi-arid landscapes where lambda E is strongly governed by the subsurface soil moisture and where the majority of other lambda E models generally show poor results. Sensitivity analysis revealed a high sensitivity of both the fluxes to the uncertainties in T-S. A realistic response and modest relationship was also found when partitioned lambda E components (lambda E-E and lambda E-T) were compared to the observed soil moisture and rainfall. This is the first study to report the physical integration of T-S into the PM equation and finding analytical solution of the physical (g(B)) and physiological conductances (g(S)). The performance of STIC over diverse biomes and climates points to its potential to benefit future NASA and NOAA missions having thermal sensors, such as HyspIRI, GeoSTAR and GOES-R for mapping multi-scale lambda E and drought. (C) 2013 Elsevier Inc. All rights reserved.

Abstract  The USEtox model was developed in a scientific consensus process involving comparison of and harmonization between existing environmental multimedia fate models. USEtox quantitatively models the continuum from chemical emission to freshwater ecosystem toxicity via chemical-specific characterization factors (CFs) for Life Cycle Impact Assessment (LCIA). This work provides understanding of the key mechanisms and chemical parameters influencing fate in the environment and impact on aquatic ecosystems.

USEtox incorporates a matrix framework for multimedia modeling, allowing separation of fate, exposure, and ecotoxicity effects in the determination of an overall CF. Current best practices, such as incorporation of intermittent rain and effect factors (EF) based on substance toxicity across species, are implemented in the model. The USEtox database provides a dataset of over 3,000 organic chemicals, of which approximately 2,500 have freshwater EFs. Freshwater characterization factors for these substances, with a special focus on a subset of chemicals with characteristic properties, were analyzed to understand the contributions of fate, exposure, and effect on the overall CFs. The approach was based on theoretical interpretation of the multimedia model components as well as multidimensional graphical analysis.

For direct emission of a substance to water, the EF strongly controls freshwater ecotoxicity, with a range of up to 10 orders of magnitude. In this release scenario, chemical-specific differences in environmental fate influence the CF for freshwater emissions by less than 2 orders of magnitude. However, for an emission to air or soil, the influence of the fate is more pronounced. Chemical partitioning properties between water, air, and soil may drive intermedia transfer, which may be limited by the often uncertain, media-specific degradation half-life. Intermedia transfer may be a function of landscape parameters as well; for example, direct transfer from air to freshwater is limited by the surface area of freshwater. Overall, these altered fate factors may decrease the CF up to 8 orders of magnitude.

This work brings new clarity to the relative contributions of fate and freshwater ecotoxicity to the calculation of CFs. In concert with the USEtox database, which provides the most extensive compilation of CFs to date, these findings enable those undertaking LCIA to understand and contextualize existing and newly calculated CFs.

Abstract  A common goal of water and energy management is to maximize the supply of one while minimizing the use of the other, so it is important to understand the relationship between water use and energy production. A larger proportion of horizontal wells and an increasing number of hydraulically fractured well bores are being completed in the United States, and consequently increasing water demand by oil and gas operations. Management, planning, and regulatory decisions for water, oil, and gas are largely made at the state-level; therefore, it is necessary to aggregate water use and energy production data at the state-scale. The purpose of this paper is to quantify annual volumes of water used for completion of oil and gas wells, coproduced during oil and gas production, injected via underground injection program wells, and used in water flooding operations. Data from well completion reports, and tax commission records were synthesized to arrive at these estimates for Oklahoma. Hydraulic fracturing required a median fluid volume of 11,350 m(3) per horizontal well in Oklahoma. Median fluid volume (~15,774 m(3)) and volume per perforated interval (15.73 m(3) m(-1)) were highest for Woodford Shale horizontal wells. State-scale annual water use for oil and gas well completions was estimated to be up to 16.3 Mm(3) in 2011 or less than 1% of statewide freshwater use. Statewide annual produced water volumes ranged from 128.5 to 146.6 Mm(3), with gas wells yielding an estimated 72.4% of the total coproduced water. Volumes of water injected into underground injection control program wells ranged from 206.8 to 305.4 Mm(3), which indicates that water flooding operations may use up to 167.0 Mm(3) per year. State-scale water use estimates for Oklahoma could be improved by requiring oil and gas operators to supplement well completion reports with water use and water production data. Reporting of oil and gas production data by well using a unique identifier (i.e., API number) would also allow for refinement of produced water quantity information. Reporting of wastewater disposal and water flooding volumes could be used to further develop state-scale water accounting and best management practices.

Abstract  Perennial herbaceous plants such as switchgrass (Panicum virgatum L.) are being evaluated as cellulosic bioenergy crops. Two major concerns have been the net energy efficiency and economic feasibility of switchgrass and similar crops. All previous energy analyses have been based on data from research plots (<5 m2) and estimated inputs. We managed switchgrass as a biomass energy crop in field trials of 3-9 ha (1 ha = 10,000 m2) on marginal cropland on 10 farms across a wide precipitation and temperature gradient in the midcontinental U.S. to determine net energy and economic costs based on known farm inputs and harvested yields. In this report, we summarize the agricultural energy input costs, biomass yield, estimated ethanol output, greenhouse gas emissions, and net energy results. Annual biomass yields of established fields averaged 5.2-11.1 Mg x ha(-1) with a resulting average estimated net energy yield (NEY) of 60 GJ x ha(-1) x y(-1). Switchgrass produced 540% more renewable than nonrenewable energy consumed. Switchgrass monocultures managed for high yield produced 93% more biomass yield and an equivalent estimated NEY than previous estimates from human-made prairies that received low agricultural inputs. Estimated average greenhouse gas (GHG) emissions from cellulosic ethanol derived from switchgrass were 94% lower than estimated GHG from gasoline. This is a baseline study that represents the genetic material and agronomic technology available for switchgrass production in 2000 and 2001, when the fields were planted. Improved genetics and agronomics may further enhance energy sustainability and biofuel yield of switchgrass.

Abstract  For the C4 perennial grasses, Miscanthusxgiganteus and Panicum virgatum (switchgrass) to be successful for bioenergy production they must maintain high yields over the long term. Previous studies under the less conducive climate for productivity in N.W. Europe found little or no yield decline in M.xgiganteus in the long term. This study provides the first analysis of whether yield decline occurs in M.xgiganteus under United States. Midwest conditions in side-by-side trials with P. virgatum over 8-10years at seven locations across Illinois. The effect of stand age was determined by using a linear regression model that included effects of weather. Miscanthusxgiganteus produced yields more than twice that of P. virgatum averaging 23.4 +/- 1.2Mgha(-1)yr(-1) and 10.0 +/- 0.9Mgha(-1)yr(-1), respectively, averaged over 8-10years. Relationships of yield with precipitation and growing degree days were established and used to estimate yields corrected for the stochastic effects of weather. Across all locations and in both species, yield initially increased until it reached a maximum during the fifth growing season and then declined to a stable, but lower level in the eighth. This pattern was more pronounced in M.xgiganteus. The mean yields observed over this longer term period of 8-10years were lower than the yields of the first 5years. However, this decline was proportionately greater in M.xgiganteus than in P. virgatum, suggesting a stronger effect of stand age on M.xgiganteus. Based on the average yield over the period of this study, meeting the United States Renewable Fuel Standard mandate of 60billion liters of cellulosic ethanol by 2022, would require 6.8Mha of M.xgiganteus or 15.8Mha of P. virgatum. These appear manageable numbers for the United States, given the 16.0Mha in the farmland Conservation Reserve Program in addition to another 13.0Mha abandoned from agriculture in the last decade.

Abstract  The aim of this work was to assess the environmental consequences of anaerobic mono- and co-digestion of pig manure to produce bio-energy, from a life cycle perspective. This included assessing environmental impacts and land use change emissions (LUC) required to replace used co-substrates for anaerobic digestion. Environmental impact categories considered were climate change, terrestrial acidification, marine and freshwater eutrophication, particulate matter formation, land use, and fossil fuel depletion. Six scenarios were evaluated: mono-digestion of manure, co-digestion with: maize silage, maize silage and glycerin, beet tails, wheat yeast concentrate (WYC), and roadside grass. Mono-digestion reduced most impacts, but represented a limited source for bio-energy. Co-digestion with maize silage, beet tails, and WYC (competing with animal feed), and glycerin increased bio-energy production (up to 568%), but at expense of increasing climate change (through LUC), marine eutrophication, and land use. Co-digestion with wastes or residues like roadside grass gave the best environmental performance.

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  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  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  Agricultural nonpoint source water pollution has long been recognized as an important contributor to U.S. water quality problems and the subject of an array of local, state, and federal initiatives to reduce the problem. A "pay-the-polluter" approach to getting farmers to adopt best management practices has not succeeded in improving water quality in many impaired watersheds. With the prospects of reduced funding for the types of financial and technical assistance programs that have been the mainstay of agricultural water quality policy, alternative approaches need to be considered. Some changes to the way current conservation programs are implemented could increase their efficiency, but there are limits to how effective a purely voluntary approach can be. An alternative paradigm is the "polluter pays" approach, which has been successfully employed to reduce point source pollution. A wholesale implementation of the polluter-pays approach to agriculture is likely infeasible, but elements of the polluter-pays approach could be incorporated into agricultural water quality policy.

Abstract  The purpose of this study is to relate soil properties affected by the deposit of materials by the wind to the percentage of vegetation surface that facilitates their accumulation. To do this, we applied artificial wind and compared its effects to natural conditions by making use of the fertility islands' generated by some species of bushes under their canopies in semiarid environments and, which according to many publications, modify soil characteristics substantially. Two very common species in our flat semiarid study area, Hammada articulata and Artemisia barrelieri, were chosen for comparison. Soil was sampled in gaps between shrubs and under canopies. Some shrubs were subjected to extra wind, whereas others were kept under natural conditions. At the end of this first stage, the islands under the canopies were sampled again, and any differences found in the data were studied. Increased retention of material affects the fertility of soils. Thus, we observed, for example, an increase in biomass carbon showing greater biological activity. Finally, we performed a statistical analysis, which resolved our hypothesis on the influence of the percentage of plant surface on the soil parameters. Copyright (c) 2012 John Wiley & Sons, Ltd.

Abstract  Air pollution emissions regulation can affect the location, size, and technology choice of potential biofuel production facilities. Difficulty in obtaining air pollutant emission permits and the cost of air pollution control devices have been cited by some fuel producers as barriers to development. This paper expands on the Geospatial Bioenergy Systems Model (GBSM) to evaluate the effect of air pollution control costs on the availability, cost, and distribution of U.S. biofuel production by subjecting potential facility locations within U.S. Clean Air Act nonattainment areas, which exceed thresholds for healthy air quality, to additional costs. This paper compares three scenarios: one with air quality costs included, one without air quality costs, and one in which conversion facilities were prohibited in Clean Air Act nonattainment areas. While air quality regulation may substantially affect local decisions regarding siting or technology choices, their effect on the system as a whole is small. Most biofuel facilities are expected to be sited near to feedstock supplies, which are seldom in nonattainment areas. The average cost per unit of produced energy is less than 1% higher in the scenarios with air quality compliance costs than in scenarios without such costs. When facility construction is prohibited in nonattainment areas, the costs increase by slightly over 1%, due to increases in the distance feedstock is transported to facilities in attainment areas.

Abstract  The environmental impacts of remediation of a chloroethene-contaminated site were evaluated using life cycle assessment (LCA). The compared remediation options are (i) in situ bioremediation by enhanced reductive dechlorination (ERD), (ii) in situ thermal desorption (ISTD), and (iii) excavation of the contaminated soil followed by off-site treatment and disposal. The results showed that choosing the ERD option will reduce the life-cycle impacts of remediation remarkably compared to choosing either ISTD or excavation, which are more energy-demanding. In addition to the secondary impacts of remediation, this study includes assessment of local toxic impacts (the primary impact) related to the on-site contaminant leaching to groundwater and subsequent human exposure via drinking water. The primary human toxic impacts were high for ERD due to the formation and leaching of chlorinated degradation products, especially vinyl chloride during remediation. However, the secondary human toxic impacts of ISTD and excavation are likely to be even higher, particularly due to upstream impacts from steel production. The newly launched model, USEtox, was applied for characterization of primary and secondary toxic impacts and combined with a site-dependent fate model of the leaching of chlorinated ethenes from the fractured clay till site.

Abstract  Meeting future biofuel targets set by the 2007 Energy Independence and Security Act (EISA) will require a substantial increase in production of corn. The Midwest, which has the highest overall crop production capacity, is likely to bear the brunt of the biofuel-driven changes. In this paper, we set forth a method for developing a possible future landscape and evaluate changes in practices and production between base year (BY) 2001 and biofuel target (BT) 2020. In our BT 2020 Midwest landscape, a total of 25 million acres (1 acre = 0.40 ha) of farmland was converted from rotational cropping to continuous corn. Several states across the Midwest had watersheds where continuous corn planting increased by more than 50%. The output from the Center for Agriculture and Rural Development (CARD) econometric model predicted that corn grain production would double. In our study we were able to get within 2% of this expected corn production. The greatest increases in corn production were in the Corn Belt as a result of conversion to continuous corn planting. In addition to changes to cropping practices as a result of biofuel initiatives we also found that urban growth would result in a loss of over 7 million acres of productive farmland by 2020. We demonstrate a method which successfully combines economic model output with gridded land cover data to create a spatially explicit detailed classification of the landscape across the Midwest. Understanding where changes are likely to take place on the landscape will enable the evaluation of trade-offs between economic benefits and ecosystem services allowing proactive conservation and sustainable production for human well-being into the future.

Abstract  As the environmental and economic consequences of fossil-fuel use become clear, land is increasingly targeted as a source of bioenergy. We explore the potential for generating electricity from biomass vulnerable to fires as an ecologic and socioeconomic opportunity that can reduce the risk of greenhouse gas generation from wildfires and help to create incentives to preserve natural and seminatural vegetation and prevent its conversion to agriculture, including biofuel crops. On the basis of a global analysis of the energy generation and spatial distribution of fires, we show that between 2003 and 2010, global fires consumed similar to 8300 +/- 592PJyr(-1) of energy, equivalent to similar to 3644% of the global electricity consumption in 2008 and >100% national consumption in 57 countries. Forests/woodlands, cultivated areas, shrublands, and grasslands contributed 53%, 19%, 16%, and 3.5% of the global energy released by fires. Although many agroecological, socioeconomic, and engineering challenges need to be overcome before diverting the energy lost in fires into more useable forms, done cautiously it could reconcile habitat preservation with economic yields in natural systems.

Abstract  Little information exists on resource selection by foraging Indiana bats (Myotis sodalis) during the maternity season. Existing studies are based on modest sample sizes because of the rarity of this endangered species and the difficulty of radio-tracking bats. Our objectives were to determine resource selection by foraging Indiana bats during the maternity season and to compare resource use between pregnant and lactating individuals. We used an information theoretic approach with discrete choice modeling based on telemetry data to evaluate our hypotheses that land cover, percent canopy cover, distance to water, and prescribed fire affected the relative probability a point was used by a foraging Indiana bat. We fit models for individual bats and a population-level model based on all individuals with a random factor to account for differences in sample size among individuals. We radio-tracked 29 individuals and found variation in resource selection among individuals. However, among individuals with the same supported covariates, the magnitude and direction of the covariates were similar. Eighteen bats selected areas with greater canopy closure and 5 of 6 bats that had areas burned by low-intensity prescribed fire in their home range selected burned areas. Resource selection was related to land cover for 13 individuals; they selected forest and shrubland over agricultural land, which composed >50% of the landscape within 10km. We found no support for our hypothesis that resource selection was related to individual reproductive condition or Julian date in our population-level model indicating habitat selection was not determined by reproductive status or date within the maternity season. Land use or forest management that greatly reduces canopy cover may have a negative impact on Indiana bat use. Maintaining forest cover in agricultural landscapes is likely critical to persistence of maternity colonies in these landscapes. Sites managed with low severity prescribed fire may be selected by some individuals because of reduced understory vegetation.

Abstract  Removal of corn (Zea mays L.) stover as a biofuel feedstock is being considered. It is important to understand the implications of this practice when establishing removal guidelines to ensure the long-term sustainability of both the biofuel industry and soil health. Aboveground and belowground plant residues are the soil's main sources of organic materials that bind soil particles together into aggregates and increase soil carbon (C) storage. Serving to stabilize soil particles, soil organic matter (SOM) assists in supplying plant available nutrients, increases water holding capacity, and helps reduce soil erosion. Data obtained from three Corn Stover Regional Partnership sites (Brookings, SD; Morris, MN; and Ithaca, NE) were utilized to evaluate the impact of removing corn stover on soil physical properties, including dry aggregate size distribution (DASD), erodible fraction (EF), and SOM components. Each site consisted of a combination of three residue removal rates (low-removal of grain only, intermediate-approximately 50 % residue removal, and high-maximum amount of residue removal). Results showed that the distribution of soil aggregates was less favorable for all three locations when residue was removed without the addition of other sources of organic matter such as cover crops. Additionally, we found that when residue was removed and the soil surface was less protected, there was an increase in the EF at all three research sites. There was a reduction in the EF for both the Brookings, SD, and Ithaca, NE sites when cover crops were incorporated or additional nitrogen (N) was added to the system. Amounts of SOM, fine particulate organic matter (fPOM), and total particulate organic matter (tPOM) consistently decreased as greater amounts of residue were removed from the soil surface. Across these three locations, the removal of crop residue from the soil surface had a negative impact on measured soil physical properties. The addition of a cover crop or additional N helped reduce this impact as measured through aggregate size distribution and EF and SOM components.

Abstract  Sugarcane bagasse is one of the main agro-industrial residues which can be used to produce wood-based panels. However, more investigations related to its environmental performance assessment are needed, focusing on questions such as: Does it provide environmental benefits? What are its main environmental impacts? Could it substitute wood as raw material? Accordingly, this paper presents a life cycle assessment (LCA) study of particle board manufactured with sugarcane bagasse residues.

The cradle-to-gate assessment of 1 m(3) of particle board made with sugarcane bagasse (PSB) considered three main subsystems: bagasse generation, bagasse distribution, and PSB production. For the inventory of PSB, dataset from two previous LCA studies related to the conventional particle board production and the ethanol life cycle for the Brazilian context were used. The allocation criterion for the bagasse generation subsystem was 9.08 % (economic base). The potential environmental impact phase was assessed by applying the CML and USEtox methods. PSB was compared with the conventional particle board manufactured in Brazil by the categories of the CML and USETox, and including land use indicators. Finally, two scenarios were analyzed to evaluate the influence of the allocation criteria and the consumption of sugarcane bagasse.

All hotspots identified by CML and USETox methods are mainly related to the PSB production subsystem (24-100 % of impacts) due to heavy fuel oil, electricity, and urea-formaldehyde resin supply chain. The bagasse generation subsystem was more relevant to the eutrophication category (75 % of impacts). The bagasse distribution subsystem was not relevant because the impacts on all categories were lower than 1 %. PSB can substitute the conventional particle board mainly because of its lower contribution to abiotic depletion and ecotoxicity. Regarding land use impacts, PSB showed lower values according to all indicators (38-40 % of all impacts), which is explained by the lower demand for land occupation in comparison to that of the traditional particle board.

PSB can replace the traditional particle board due to its better environmental performance. The analysis of the economic allocation criterion was relevant only for the EP category, being important to reduce diesel and N-based fertilizers use during sugarcane cultivation. Regarding the influence of the sugarcane bagasse consumption, it is suggested that the sugarcane bagasse be mixed up to 75 % during particle board manufacturing so that good quality properties and environmental performance of panels can be provided.

Abstract  Development and implementation of local and regional plans to control nonpoint sources of pollution from agricultural land are major mandates of section 208 of Public Law 92-500. Many planners tend to equate erosion control as measured by the universal soil loss equation with improvements in water quality. Others implement channel management practices which degrade rather than improve water quality and thereby decrease the effectiveness of other efforts to control nonpoint sources. Planners rarely recognize the importance of the land-water interface in regulating water quality in agricultural watersheds. More effective planning can result from the development of "best management systems" which incorporate theory from all relevant disciplines.

Abstract  Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was summarized to assess the influence of various factors regulating emissions from mineral soils. The data indicate that there is a strong increase of both N2O and NO emissions accompanying N application rates, and soils with high organic-C content show higher emissions than less fertile soils. A fine soil texture, restricted drainage, and neutral to slightly acidic conditions favor N2O emission, while (though not significant) a good soil drainage, coarse texture, and neutral soil reaction favor NO emission. Fertilizer type and crop type are important factors for N2O but not for NO, while the fertilizer application mode has a significant influence on NO only. Regarding the measurements, longer measurement periods yield more of the fertilization effect on N2O and NO emissions, and intensive measurements (greater than or equal to1 per day) yield lower emissions than less intensive measurements (2-3 per week). The available data can be used to develop simple models based on the major regulating factors which describe the spatial variability of emissions of N2O and NO with less uncertainty than emission factor approaches based on country N inputs, as currently used in national emission inventories.

Abstract  Historically, the central Midwestern US has undergone drastic anthropogenic land use change, having been transformed, in part through government policy, from a natural grassland system to an artificially drained agricultural system devoted to row cropping corn and soybeans. Current federal policies are again influencing land use in this region with increased corn acreage and new biomass crops proposed as part of an energy initiative emphasizing biofuels. To better address these present and future challenges it is helpful to understand whether and how the legacies of past changes have shaped the current response of the system. To this end, a comparative analysis of the hydrologic signatures in both spatial and time series data from two central Illinois watersheds was undertaken. The past history of these catchments is reflected in their current hydrologic responses, which are highly heterogeneous due to differences in geologic history, artificial drainage patterns, and reservoir operation, and manifest temporally, from annual to daily timescales, and spatially, both within and between the watersheds. These differences are also apparent from analysis of the summer low flows, where the more tile-drained watershed shows greater variability overall than does the more naturally drained one. In addition, precipitation in this region is also spatially heterogeneous even at small scales, and this, interacting with and filtering through the historical modifications to the system, increases the complexity of the problem of predicting the catchment response to future changes.

Abstract  The fate of organic carbon (C) lost by erosion is not well understood in agricultural settings. Recent models suggest that wetlands and other small water bodies may serve as important long-term sinks of eroded C, receiving similar to 30% of all eroded material in the US. To better understand the role of seasonally-saturated wetlands in sequestering eroded C, we examined the spatial and temporal dynamics of C and sediment accumulation in a 13-year-old constructed wetland used to treat agricultural runoff. The fate of C sequestered within deposited sediment was modeled using point-sampling, remote sensing, and geostatistics. Using a spatially-explicit sampling design, annual net rates of sedimentation and above-ground biomass were measured during two contrasting years (vegetated (2004) vs. non-vegetated (2005)), followed by collection of sediment cores to the antecedent soil layer, representing 13 years of sediment and C accumulation. We documented high annual variation in the relative contribution of endogenous and exogenous C sources, as well as absolute rates of sediment and C deposition. This annual variation, however, was muted in the long-term (13 yr) sediment record, which showed consistent vertical patterns of uniform C distribution (similar to 14 g kg(-1)) and delta C-13 signatures in high depositional environments. This was in contrast to low depositional environments which had high levels of surface C enrichment (20-35 g kg(-1)) underlain by C depleted (5-10 g kg(-1)) sediments and an increasing delta C-13 signature with depth indicating increased decomposition. These results highlight the importance of sedimentation in physically protecting soil organic carbon and its role in controlling the long-term C concentration of seasonally-saturated wetland soils. While significant enrichment of surface sediments with endogenous C occurred in newly deposited sediment (i.e., 125 kgm(2) in 2004), fluctuating cycles of flooding and drying maintained the long-term C concentration at the same level as inflowing sediment (i.e., 14 g kg(-1)), indicating no additional long-term storage of endogenous C. These results demonstrate that constructed flow-through wetlands can serve as important sinks for eroded C and sediment in agricultural landscapes, however, additional C sequestration via enrichment from endogenous sources may be limited in seasonally-saturated wetlands due to rapid decomposition during drying cycles.