• Authors:
    • Heitman, J. L.
    • Sauer, T. J.
    • Kuang, X.
    • Xiao, X.
    • Horton, R.
  • Source: Journal
  • Volume: 79
  • Issue: 4
  • Year: 2015
  • Summary: Soil CO2 production rates and fluxes vary with time and depth. The shallow near-surface soil layer is important for myriad soil processes, yet knowledge of dynamic CO2 concentrations and fluxes in this complex zone is limited. We used a concentration gradient method (CGM) to determine CO2 production and effluxes with depth in shallow layers of a bare soil. The CO2 concentration was continuously measured at 13 depths in the 0- to 200-mm soil layer. For an 11-d period, 2% of the soil CO2 was produced below a depth of 175 mm, 8% was produced in the 50- to 175-mm soil layer, and 90% was produced in the 0- to 50-mm soil layer. Soil CO2 concentration showed similar diurnal patterns with temperature in deeper soil layers and out-of-phase diurnal patterns in surface soil layers. Soil CO2 flux from most of the soil layers can be described by an exponential function of soil temperature, with temperature sensitivity (Q10) ranging from 1.40 to 2.00 (1.62 ± 0.17). The temperature-normalized CO2 fluxes are related to soil water content with a positive linear relationship in surface soil layers and a negative relationship in deep soil layers. The CO2 fluxes from CGM and chamber methods had good agreement at multiple time scales, which showed that the CGM method was able to estimate near-surface soil CO2 fluxes and production. The contrasting patterns between surface and deep layers of soil CO2 concentration and fluxes suggest the necessity of intensive CO2 concentration measurements in the surface soil layer for accurate determination of soil-atmosphere CO2 flux when using the CGM. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA.
  • Authors:
    • Dale,Larry L.
    • Karali,Nihan
    • Millstein,Dev
    • Carnall,Mike
    • Vicua,Sebastian
    • Borchers,Nicolas
    • Bustos,Eduardo
    • O'Hagan,Joe
    • Purkey,David
    • Heaps,Charles
    • Sieber,Jack
    • Collins,William D.
    • Sohn,Michael D.
  • Source: Climatic Change
  • Volume: 132
  • Issue: 2
  • Year: 2015
  • Summary: This paper is among the first to report on the full integration of basin-scale models that include projections of the demand and supply of water and energy for residential, commercial, industrial, and agricultural sector users. We link two widely used regional planning models that allow one to study the impact of rising climate variability on water and electricity use in Sacramento, California. Historic data combined with the current energy and water system configuration was used to assess the implications of changes in temperature and precipitation. Climate simulations suggest that electricity imports to the region would increase during hot dry spells, when regional power production is most constrained. In particular, regional imports of electricity would increase over 35 % in hot dry years, assuming a 4 A degrees C increase in average temperature and a 25 % decrease in average precipitation.
  • Authors:
    • Evans,Jason M.
    • Calabria,Jon
    • Borisova,Tatiana
    • Boellstorf,Diane E.
    • Sochacka,Nicki
    • Smolen,Michael D.
    • Mahler,Robert L.
    • Risse,L. Mark
  • Source: Climatic Change
  • Volume: 132
  • Issue: 2
  • Year: 2015
  • Summary: A growing body of research indicates that opinions about long-term climate change and other natural resource issues can be significantly affected by current weather conditions (e.g., outside air temperature) and other highly contingent environmental cues. Although increased severity and frequency of droughts is regarded as a likely consequence of anthropogenic climate change, little previous research has attempted to relate the experience of drought with public attitudes about water supply or water-related climate change issues. For this study, a large set (n = 3,163) of public survey data collected across nine states of the southern United States was spatio-temporally linked with records of short-term (similar to 12 weeks) and long-term (similar to 5 years) drought condition at the level of each respondent's zip code. Multivariate ordinal logistic regression models that included numerous other independent variables (environmental ideology, age, gender, education, community size, residency duration, and local annual precipitation) indicated highly significant interactions with long-term drought condition, but showed no significant effect from short-term drought condition. Conversely, attitudes about water-related climate change showed highly significant interactions with short-term drought, with weaker to no effects from long-term drought. While the finding of significant effects from short-term drought condition on opinions about future drought is broadly consistent with previous public opinion research on climate change, the finding of water supply attitudes being more responsive to longer term drought condition is, to our knowledge, a novel result. This study more generally demonstrates the methodological feasibility and applied importance of accounting for local drought condition when public opinion information is used to evaluate outreach programs for water conservation and climate change.
  • Authors:
    • Kaliyan,N.
    • Morey,R. V.
    • Tiffany,D. G.
  • Source: BioEnergy Research
  • Volume: 8
  • Issue: 3
  • Year: 2015
  • Summary: Supply logistics systems for corn (Zea mays L.) stover and switchgrass (Panicum virgatum L.) with two collection methods, round bales and rectangular bales, are developed. A location in the US Midwest is assumed with corn grown on highly productive crop land and switchgrass grown on less productive land. Bales (15 % moisture wet basis) are stored at local storage sites within 3.2 km (2 mi) of the field at harvest time. Biomass is transported to an end user within a 48 km (30 mi) throughout the year. Round bales are converted to bulk product [bulk density of 240 kg m−3 (15 lb ft−3)] by tub grinding followed by roll-press compacting before truck transport. Rectangular bales are delivered by truck without processing. Total delivered cost is $97.70 Mg−1 ($88.63 ton−1) for corn stover and $137.87 Mg−1 ($125.07 ton−1) for switchgrass when delivered as a bulk compacted product. Total delivered cost is $90.25 Mg−1 ($81.87 ton−1) for corn stover and $128.67 Mg−1 ($116.73 ton−1) for switchgrass when delivered as rectangular bales. Life-cycle fossil energy consumption is higher for delivering switchgrass (9.9 to 13.8 % of energy in dry matter) than for corn stover (5.8 to 9.5 % of energy in dry matter). Excluding any potential change in soil organic carbon (SOC), life-cycle greenhouse gas (GHG) emissions are 59.2 to 99.8 kg CO2e Mg−1 for delivering corn stover and 231.8 to 279.6 kg CO2e Mg−1 for delivering switchgrass. The effect of change in SOC on the life-cycle GHG emissions for corn stover and switchgrass is discussed. © 2015, Springer Science+Business Media New York.
  • Authors:
    • Parton,W. J.
    • Gutmann,M. P.
    • Merchant,E. R.
    • Hartman,M. D.
    • Adler,P. R.
    • McNeal,F. M.
    • Lutz,S. M.
  • Source: Proceedings of the National Academy of Sciences of the United States
  • Volume: 112
  • Issue: 34
  • Year: 2015
  • Summary: The Great Plains region of the United States is an agricultural production center for the global market and, as such, an important source of greenhouse gas (GHG) emissions. This article uses historical agricultural census data and ecosystem models to estimate the magnitude of annual GHG fluxes from all agricultural sources (e.g., cropping, livestock raising, irrigation, fertilizer production, tractor use) in the Great Plains from 1870 to 2000. Here, we show that carbon (C) released during the plow-out of native grasslands was the largest source of GHG emissions before 1930, whereas livestock production, direct energy use, and soil nitrous oxide emissions are currently the largest sources. Climatic factors mediate these emissions, with cool and wet weather promoting C sequestration and hot and dry weather increasing GHG release. This analysis demonstrates the long-term ecosystem consequences of both historical and current agricultural activities, but also indicates that adoption of available alternative management practices could substantially mitigate agricultural GHG fluxes, ranging from a 34% reduction with a 25% adoption rate to as much as complete elimination with possible net sequestration of C when a greater proportion of farmers adopt new agricultural practices.
  • Authors:
    • Rosas,Francisco
    • Babcock,Bruce A.
    • Hayes,Dermot J.
  • Source: Climatic Change
  • Volume: 132
  • Issue: 2
  • Year: 2015
  • Summary: Farmers may choose to apply nitrogen fertilizer at a rate that exceeds the average ex post agronomically optimal rate when the yield response to nitrogen varies across growing seasons. Negative environmental consequences such as nitrous oxide (N2O) emissions and/or water pollution can result when all the applied nitrogen is not needed by the crop. Here we consider a nonlinear market instrument targeting farmers' nitrogen use, and by solving for the optimal nitrogen reduction using a model of expected utility of farm profits, we evaluate the induced N2O emission reductions that are consistent with the instrument introduced. The market instrument is nonlinear because of the expected nonlinear relationship between N2O and nitrogen application rates. Our simulations show that, in cases where farmers apply N at rates which exceed recommendations and the N2O response is likely to be non-linear, payments will induce participation in the program and will have a significant impact on both expected and actual N2O emissions without significantly harming expected or actual yields. Failure to consider this nonlinearity would deviate the attention away from N2O pollution because it would require large N reductions (and crop yields) to achieve equivalent N2O abatement.
  • Authors:
    • Sinistore,J. C.
    • Reinemann,D. J.
    • Izaurralde,R. C.
    • Cronin,K. R.
    • Meier,P. J.
    • Runge,T. M.
    • Zhang,X.
  • Source: BioEnergy Research
  • Volume: 8
  • Issue: 3
  • Year: 2015
  • Summary: Spatial variability in yields and greenhouse gas emissions from soils has been identified as a key source of variability in life cycle assessments (LCAs) of agricultural products such as cellulosic ethanol. This study aims to conduct an LCA of cellulosic ethanol production from switchgrass in a way that captures this spatial variability and tests results for sensitivity to using spatially averaged results. The Environment Policy Integrated Climate (EPIC) model was used to calculate switchgrass yields, greenhouse gas (GHG) emissions, and nitrogen and phosphorus emissions from crop production in southern Wisconsin and Michigan at the watershed scale. These data were combined with cellulosic ethanol production data via ammonia fiber expansion and dilute acid pretreatment methods and region-specific electricity production data into an LCA model of eight ethanol production scenarios. Standard deviations from the spatial mean yields and soil emissions were used to test the sensitivity of net energy ratio, global warming potential intensity, and eutrophication and acidification potential metrics to spatial variability. Substantial variation in the eutrophication potential was also observed when nitrogen and phosphorus emissions from soils were varied. This work illustrates the need for spatially explicit agricultural production data in the LCA of biofuels and other agricultural products. © 2015, The Author(s).
  • Authors:
    • Stegelin,F. E.
  • Source: Acta Horticulturae
  • Volume: 1090
  • Year: 2015
  • Summary: Agribusinesses with the purpose of growing and supplying horticultural crops to the end-user often realize there is power in numbers; in other words, using some form of organizational structure to provide economic gains (acquiring inputs cheaper, increasing distribution efficiencies, combining selling activities). Accomplishing these growth or survival strategies often involves collaborative purchasing and marketing with supply chain partners. The horticultural industry, among others, is abuzz with sustainability, emphasizing it as the original green industry. Sustainability encompasses three components: societal or community well-being, economics and profitability, and environmental quality. Hence, adopting a strategic alliance among industry partners should enhance the horticulture supply chain sustainability and profitability; but does it? The formation of horticultural crops producer strategic alliances, evaluating the supply chain participation within each of the alliances, and conducting a life cycle assessment to determine the carbon neutrality and sustainability of the supply chain was the impetus of this study. Net results of five transportation alliances established among small- to mid-sized greenhouse (floriculture) and container nurseries (annuals and perennials) in Georgia indicated a 12% average annual total cost savings to participating firms in each alliance, a 23% average annual total miles driven reduction and savings, an 18% average annual vehicle ownership expense savings to the alliance partners, a 31% average annual savings in driver labor and hours of drive time, and a 19% overall (system-wide) reduction in total carbon dioxide equivalent (CO 2e) emissions-reducing the carbon footprint, but not reaching carbon neutrality.
  • Authors:
    • Thomazini,A.
    • Spokas,K.
    • Hall,K.
    • Ippolito,J.
    • Lentz,R.
    • Novak,J.
  • Source: Agriculture, Ecosystems and Environment
  • Volume: 207
  • Year: 2015
  • Summary: One potential strategy to abate increasing atmospheric carbon dioxide (CO 2) levels is to sequester CO 2 as biochar, a structural form of carbon created through the pyrolysis of various biomass materials. Biochar may be applied to soils, but has resulted in variable impacts on net soil greenhouse gas (GHG) emissions, with results spanning from suppression to stimulation. This laboratory incubation study examined the impacts of the same hardwood biochar (fast pyrolysis at 550°C) to elucidate driving variables affecting previously observed carbon dioxide (CO 2) fluctuations as well as nitrous oxide (N 2O), and methane (CH 4) production impacts across ten different US soils with and without biochar (10% w/w). Biochar application significantly impacted CO 2 ( P=0.04) and N 2O ( P=0.03) production following amendment across all soils, but there were no differences observed in CH 4 production/oxidation rates ( P=0.90). Interestingly, the induced biochar GHG alterations were significantly correlated to the original GHG production activity in the control soil, suggesting a more universal response across various soils to the same biochar than has been previously hypothesized. After correcting for the amount of CO 2 released from the biochar itself [24 g C g BC-1 d -1], there was no statistically significant alteration in the actual soil CO 2 mineralization rate for any soil. This suggests that the observed increase in CO 2 production was solely attributed to the abiotic CO 2 releases from the biochar. On the other hand, there was an average suppression of 63% in the N 2O production across all soils following biochar addition, which was again correlated to initial N 2O production activity. For this particular biochar, there are predictable impacts on the GHG production potential across various soils despite differences in soil chemistry, texture, and microbial communities.
  • Authors:
    • Jones, L. E.
    • Maddison, A. L.
    • Castle, M.
    • Barraclough, T. J. P.
    • Purdy, S. J.
    • Cunniff, J.
    • Shield, I. F.
    • Gregory, A. S.
    • Karp, A.
  • Source: Science Article
  • Volume: 80
  • Year: 2015
  • Summary: Willows ( Salix spp.) grown as short rotation coppice (SRC) are viewed as a sustainable source of biomass with a positive greenhouse gas (GHG) balance due to their potential to fix and accumulate carbon (C) below ground. However, exploiting this potential has been limited by the paucity of data available on below ground biomass allocation and the extent to which it varies between genotypes. Furthermore, it is likely that allocation can be altered considerably by environment. To investigate the role of genotype and environment on allocation, four willow genotypes were grown at two replicated field sites in southeast England and west Wales, UK. Above and below ground biomass was intensively measured over two two-year rotations. Significant genotypic differences in biomass allocation were identified, with below ground allocation differing by up to 10% between genotypes. Importantly, the genotype with the highest below ground biomass also had the highest above ground yield. Furthermore, leaf area was found to be a good predictor of below ground biomass. Growth environment significantly impacted allocation; the willow genotypes grown in west Wales had up to 94% more biomass below ground by the end of the second rotation. A single investigation into fine roots showed the same pattern with double the volume of fine roots present. This greater below ground allocation may be attributed primarily to higher wind speeds, plus differences in humidity and soil characteristics. These results demonstrate that the capacity exists to breed plants with both high yields and high potential for C accumulation.