• Authors:
    • Chang, S. X.
    • Baah-Acheamfour, M.
    • Carlyle, C. N.
    • Bork, E. W.
  • Source: Article
  • Volume: 213
  • Year: 2015
  • Summary: Agroforestry systems are common land uses across Canada and could play a substantial role in sequestering carbon (C) as part of efforts to combat climate change. We studied the impact of component land cover types (forested vs. adjacent herbland) in three agroforestry systems (hedgerow, shelterbelt and silvopasture) on organic C and nitrogen (N) distribution in three density fractions of soils at the 0-10 and 10-30 cm layers. The study evaluated 36 sites (12 hedgerows, 12 shelterbelts and 12 silvopastures) in central Alberta, Canada, distributed along a soil/climate gradient of increasing moisture availability. At the 0-10 cm layer, soil organic C (SOC) stock in the bulk soil was significantly greater in the silvopasture system (101) than in either the hedgerow (77) or shelterbelt system (67 Mg C ha -1). Soil organic C stock in both soil layers (0-10 and 10-30 cm) was also significantly greater in the forested land cover (89 and 119 Mg C ha -1, respectively) than in adjacent herblands (76 and 77 Mg C ha -1). Across all sites, 31.5, 29.1, and 35.5% of SOC was found in the light fraction (1.6 g cm -3) of soils, respectively. The largest pool of SOC in the more labile light fraction of the 0-10 cm layer was in the silvopasture system (50 Mg C ha -1), whereas the smallest labile light fraction component of SOC was in the shelterbelt system (17 Mg C ha -1). The largest pool of SOC in the more stable heavy fraction of both the 0-10 and 10-30 cm depth classes was in the shelterbelt (33 and 35 Mg C ha -1, respectively), while the least SOC was in the silvopasture system (26 and 20 Mg C ha -1, respectively). We conclude that the presence of Populus based silvopasture system can increase C storage in surface mineral soils, and that the establishment of Picea based shelterbelts in an otherwise annually cropped agricultural landscape enhances the size of the stable SOC pool.
  • Authors:
    • Soimakallio, S.
    • Holma, A.
    • Helin, T.
  • Source: International Journal of Life Cycle Assessment
  • Volume: 19
  • Issue: 4
  • Year: 2014
  • Summary: A framework for the inclusion of land use impact assessment and a set of land use impact indicators has been recently proposed for life cycle assessment (LCA) and no case studies are available for forest biomass. The proposed methodology is tested for Scandinavian managed forestry; a comparative case study is made for energy from wood, agro-biomass and peat; and sensitivity to forest management options is analysed. The functional unit of this comparative case study is 1 GJ of energy in solid fuels. The land use impact assessment framework of the United Nations Environment Programme and the Society of Environmental Toxicology and Chemistry (UNEP-SETAC) is followed and its application for wood biomass is critically analysed. Applied midpoint indicators include ecological footprint and human appropriation of net primary production, global warming potential indicator for biomass (GWP(bio)-100) and impact indicators proposed by UNEP-SETAC on ecosystem services and biodiversity. Options for forest biomass land inventory modelling are discussed. The system boundary covers only the biomass acquisition phase. Management scenarios are formulated for forest and barley biomass, and a sensitivity analysis focuses on impacts of land transformations for agro-biomass. Meaningful differences were found in between solid biofuels from distinct land use classes. The impact indicator results were sensitive to land occupation and transformation and differed significantly from inventory results. Current impact assessment method is not sensitive to land management scenarios because the published characterisation factors are still too coarse and indicate differences only between land use types. All indicators on ecosystem services and biodiversity were sensitive to the assumptions related with land transformation. The land occupation (m(2)a) approach in inventory was found challenging for Scandinavian wood, due to long rotation periods and variable intensities of harvests. Some suggestions of UNEP-SETAC were challenged for the sake of practicality and relevance for decision support. Land use impact assessment framework for LCA and life cycle impact assessment (LCIA) indicators could be applied in a comparison of solid bioenergy sources. Although forest bioenergy has higher land occupation than agro-bioenergy, LCIA indicator results are of similar magnitude or even lower for forest bioenergy. Previous literature indicates that environmental impacts of land use are significant, but it remains questionable if these are captured with satisfactory reliability with the applied LCA methodology, especially for forest biomass. Short and long time perspectives of land use impacts should be studied in LCA with characterisation factors for all relevant timeframes, not only 500 years, with a forward-looking perspective. Characterisation factors need to be modelled further for different (forest) land management intensities and for peat excavation.
  • Authors:
    • Dias, G.
    • Wagner-Riddle, C.
    • Jayasundara, S.
    • Kariyapperuma, K.
  • Source: Canadian Journal of Soil Science
  • Volume: 94
  • Issue: 1
  • Year: 2014
  • Summary: Analysis of the environmental impact of corn (Zea mays L.) uses, such as biofuels and bioproducts, requires cradle to farm-gate life-cycle analysis of energy use and net greenhouse gas (GHG) emissions associated with corn production. Previous analyses have been based on case studies. Here we present an analysis based on census data for Ontario at the county level that was performed for three scenarios: (1) corn cultivated only for grain; (2) corn cultivated for grain and 30% stover harvest; and (3) corn cultivated for grain and cob harvest. Energy intensity of corn grain at the county level varied from 1.75 to 2.17 GJ Mg-1 grain, with the largest proportions of energy being consumed for grain drying (33%), production and supply of nitrogen (N) fertilizer (30%) and diesel use for field work (17%). Overall GHG emission intensity of grain corn varied from 243 to 353 kg CO(2)eq Mg-1 grain, of which 72% were associated with N inputs [34% soil nitrous oxide (N2O) from synthetic fertilizer N (SFN), 13% from SFN production and 10% from applied manure N]. Energy intensity of corn stover and cobs was 0.96 and 0.36 GJ Mg-1 dry matter, respectively, with the largest proportion of energy associated with production and supply of replacement nutrients. Intensity of GHG emission was 79 and 31 kg CO2 eq Mg-1 dry matter for stover and for cobs, respectively. Counties with higher corn yields at lower N application rates and reduced tillage tended to produce corn with lower energy and GHG intensity per Mg grain.
  • Authors:
    • Andren, O.
    • Zhao, X.
    • Luo, Y.
  • Source: Acta Agriculturae Scandinavica Section B-Soil and Plant Science
  • Volume: 64
  • Issue: 3
  • Year: 2014
  • Summary: Soil organic carbon (SOC) is a major source/sink in atmospheric carbon balances. Farmland usually has a high potential for carbon dioxide (CO2) uptake from the atmosphere, but also for emission. Data from different areas are valuable for global SOC calculations and model development, and a survey of 108 agricultural fields in Lanzhou, China was performed. The fields were grouped by: cropping intensity (3 levels), cropping methodology (3), and crop species (10). Intensive cropping (two or more crops per year, typically vegetables), moderate (annuals in monoculture: wheat, maize, potato, melons), and extensive (orchards, lily [Lilium brownii] fields, fallow) were the intensity classes; and open field, greenhouse field, and sand-covered field (10-20 cm added on top of the topsoil) were the three methodologies. SOC concentration, pH, electrical conductivity, and soil bulk density were measured, and SOC mass (gm(-2) 0-20 cm depth) was calculated. SOC concentration was high in cauliflower, wheat, leaf vegetables, and fruit vegetables; moderate in potato, fallow (3-5 years), tree orchards, and melons; while low in lily and maize fields, and differences in SOC mass followed the same pattern. SOC concentration and mass were lowest in the extensive fields while moderate and intensive fields showed higher values. Soil bulk density in open fields was significantly lower than those in greenhouse and sand-covered fields. The climate-induced soil activity factor r(e_clim) was calculated, compared with European conditions, and was fairly similar to those in central Sweden. Other factors behind the measured results, such as the influence of initial SOC content, manure addition, crops, etc., are discussed.
  • Authors:
    • Dyer, J. A.
    • Worth, D. E.
    • McConkey, B. G.
    • Desjardins, R. L.
    • Shrestha, B. M.
    • Cerkowniak, D. D.
  • Source: Renewable Energy
  • Volume: 63
  • Issue: March
  • Year: 2014
  • Summary: Accounting for greenhouse gas (GHG) emissions at the production stage of a bioenergy crop is essential for evaluating its eco-efficiency. The objective of this study was to calculate the change in GHG emissions for canola (Brassica napus L.) production on the Canadian Prairies from 1986 to 2006. Net GHG emissions in the sub-humid and semi-arid climatic zones were estimated for fallow-seeded and stubble-seeded canola in intensive-, reduced- and no-tillage systems, with consideration given to emissions associated with synthetic nitrogen (N) fertilizer input, mineralized N from crop residues, N leaching and volatilization, farm operations, the manufacturing and transportation of fertilizer, agrochemicals and farm machinery, and emission and removal of CO2 associated with changes in land use (LUC) and land management (LMC). The GHG emissions on an area basis were higher in stubble-seeded canola than in fallow-seeded canola but, the opposite was true on a grain dry matter (DM) basis. Nitrous oxide emissions associated with canola production, CO2 emissions associated with farm energy use and the manufacturing of synthetic N fertilizer and its transportation contributed 49% of the GHG emissions in 1986 which increased to 66% in 2006. Average CO2 emissions due to LUC decreased from 27% of total GHG emissions in 1986 to 8% in 2006 and soil C sequestration due to LMC increased from 8% to 37%, respectively. These changes caused a reduction in net GHG emission intensities of 40% on an area basis and of 65% on a grain DM basis. Despite the reduction in GHG emission intensities, GHG emissions associated with canola in the Prairies increased from 3.4 Tg CO2 equiv in 1986 to 3.8 Tg CO2 equiv in 2006 because of the more than doubling of canola production. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Kludze, H.
    • McDonald,I.
    • Dadfar, H.
    • MacLean, H. L.
    • Dias, G.
    • Deen, B.
    • Sanscartier, D.
  • Source: GCB Bioenergy
  • Volume: 6
  • Issue: 4
  • Year: 2014
  • Summary: Replacement of fossil fuels with sustainably produced biomass crops for energy purposes has the potential to make progress in addressing climate change concerns, nonrenewable resource use, and energy security. The perennial grass Miscanthus is a dedicated energy crop candidate being field tested in Ontario, Canada, and elsewhere. Miscanthus could potentially be grown in areas of the province that differ substantially in terms of agricultural land class, environmental factors and current land use. These differences could significantly affect Miscanthus yields, input requirements, production practices, and the types of crops being displaced by Miscanthus establishment. This study assesses implications on life cycle greenhouse gas (GHG) emissions of these differences through evaluating five Miscanthus production scenarios within the Ontario context. Emissions associated with electricity generation with Miscanthus pellets in a hypothetically retrofitted coal generating station are examined. Indirect land use change impacts are not quantified but are discussed. The net life cycle emissions for Miscanthus production varied greatly among scenarios (-90-170 kg CO(2)eq per oven dry tonne of Miscanthus bales at the farm gate). In some cases, the carbon stock dynamics of the agricultural system offset the combined emissions of all other life cycle stages (i.e., production, harvest, transport, and processing of biomass). Yield and soil C of the displaced agricultural systems are key parameters affecting emissions. The systems with the highest potential to provide reductions in GHG emissions are those with high yields, or systems established on land with low soil carbon. All scenarios have substantially lower life cycle emissions (-20-190 g CO(2)eq kWh(-1)) compared with coal-generated electricity (1130 g CO(2)eq kWh(-1)). Policy development should consider the implication of land class, environmental factors, and current land use on Miscanthus production.
  • Authors:
    • Greve, M. B.
    • Kheir, R. B.
    • Minasny, B.
    • Hartemink, A. E.
    • Adhikari, K.
    • Greve, M. H.
  • Source: PLOS ONE
  • Volume: 9
  • Issue: 8
  • Year: 2014
  • Summary: Estimation of carbon contents and stocks are important for carbon sequestration, greenhouse gas emissions and national carbon balance inventories. For Denmark, we modeled the vertical distribution of soil organic carbon (SOC) and bulk density, and mapped its spatial distribution at five standard soil depth intervals (0-5, 5-15, 15-30, 30-60 and 60-100 cm) using 18 environmental variables as predictors. SOC distribution was influenced by precipitation, land use, soil type, wetland, elevation, wetness index, and multi-resolution index of valley bottom flatness. The highest average SOC content of 20 g kg(-1) was reported for 0-5 cm soil, whereas there was on average 2.2 g SOC kg(-1) at 60-100 cm depth. For SOC and bulk density prediction precision decreased with soil depth, and a standard error of 2.8 g kg(-1) was found at 60-100 cm soil depth. Average SOC stock for 0-30 cm was 72 t ha(-1) and in the top 1 m there was 120 t SOC ha(-1). In total, the soils stored approximately 570 Tg C within the top 1 m. The soils under agriculture had the highest amount of carbon (444 Tg) followed by forest and semi-natural vegetation that contributed 11% of the total SOC stock. More than 60% of the total SOC stock was present in Podzols and Luvisols. Compared to previous estimates, our approach is more reliable as we adopted a robust quantification technique and mapped the spatial distribution of SOC stock and prediction uncertainty. The estimation was validated using common statistical indices and the data and high-resolution maps could be used for future soil carbon assessment and inventories.
  • Authors:
    • Gundersen, P.
    • Stefansdottir, H. M.
    • Vesterdal, L.
    • Kiar, L. P.
    • Barcena, T. G.
    • Sigurdsson, B. D.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 8
  • Year: 2014
  • Summary: Northern Europe supports large soil organic carbon (SOC) pools and has been subjected to high frequency of land-use changes during the past decades. However, this region has not been well represented in previous large-scale syntheses of land-use change effects on SOC, especially regarding effects of afforestation. Therefore, we conducted a meta-analysis of SOC stock change following afforestation in Northern Europe. Response ratios were calculated for forest floors and mineral soils (0-10 cm and 0-20/30 cm layers) based on paired control (former land use) and afforested plots. We analyzed the influence of forest age, former land-use, forest type, and soil textural class. Three major improvements were incorporated in the meta-analysis: analysis of major interaction groups, evaluation of the influence of nonindependence between samples according to study design, and mass correction. Former land use was a major factor contributing to changes in SOC after afforestation. In former croplands, SOC change differed between soil layers and was significantly positive (20%) in the 0-10 cm layer. Afforestation of former grasslands had a small negative (nonsignificant) effect indicating limited SOC change following this land-use change within the region. Forest floors enhanced the positive effects of afforestation on SOC, especially with conifers. Meta-estimates calculated for the periods 30 years since afforestation revealed a shift from initial loss to later gain of SOC. The interaction group analysis indicated that meta-estimates in former land-use, forest type, and soil textural class alone were either offset or enhanced when confounding effects among variable classes were considered. Furthermore, effect sizes were slightly overestimated if sample dependence was not accounted for and if no mass correction was performed. We conclude that significant SOC sequestration in Northern Europe occurs after afforestation of croplands and not grasslands, and changes are small within a 30-year perspective.
  • Authors:
    • Boettcher, J.
    • Kage, H.
    • Ratjen, A.
    • Heumann, S.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 99
  • Issue: 1-3
  • Year: 2014
  • Summary: Eliminating uncertainty in soil N supply could reduce fertilizer input, but the amount of N mineralized during plant growth is usually still unknown. We aimed to test the relatively simple two-pool net N mineralization model NET N that uses site-specific temperature and soil water functions as well as pedotransfer functions for deriving the pool sizes and was developed for NW Germany. The objectives were to (1) evaluate, if field net N mineralization under unfertilized winter wheat could be satisfactorily simulated, and to (2) examine the variation in time patterns of net N mineralization within years and sites and from two functional N pools: a rather small, fast mineralizable N pool (N-fast) and a much greater, slowly mineralizable N pool (N-slow). NET N simulations for 36 site-year-combinations and up to five dates within the growing season were evaluated with detailed N balance approaches (calculated from: soil mineral N contents, plant N uptake using estimates of green area index, simulated N leaching). Simulated net N mineralization was highly significantly correlated (r(2) = 0.58; root mean square error = 24.2 kg N ha(-1)) to estimations from the most detailed balance approach, with total simulated net N mineralization until mid August ranging from 62.1 to 196.5 kg N ha(-1). It also became evident that N mineralization from pool N-slow-in contrast to pool N-fast-was considerably higher for loess soils than for sandy or loamy soils. The results suggest that NET N was adequate for simulations in unfertilized winter wheat. However, further field studies are necessary for proving its applicability under fertilized conditions.
  • Authors:
    • Lopes de Gerenyu, V.
    • Kurganova, I.
    • Six, J.
    • Kuzyakov, Y.
  • Source: Global Change Biology
  • Volume: 20
  • Issue: 3
  • Year: 2014
  • Summary: The collapse of collective farming in Russia after 1990 and the subsequent economic crisis led to the abandonment of more than 45 million ha of arable lands (23% of the agricultural area). This was the most widespread and abrupt land use change in the 20th century in the northern hemisphere. The withdrawal of land area from cultivation led to several benefits including carbon (C) sequestration. Here, we provide a geographically complete and spatially detailed analysis of C sequestered in these abandoned lands. The average C accumulation rate in the upper 20 cm of mineral soil was 0.960.08 Mg C ha -1 yr -1 for the first 20 years after abandonment and 0.190.10 Mg C ha -1 yr -1 during the next 30 years of postagrogenic evolution and natural vegetation establishment. The amount of C sequestered over the period 1990-2009 accounts to 42.63.8 Tg C per year. This C sequestration rate is equivalent to ca. 10% of the annual C sink in all Russian forests. Furthermore, it compensates all fire and postfire CO 2 emissions in Russia and covers about 4% of the global CO 2 release due to deforestation and other land use changes. Our assessment shows a significant mitigation of increasing atmospheric CO 2 by prolonged C accumulation in Russian soils caused by collective farming collapse.