• Authors:
    • Zhao, Y-C.
    • Sun, W-X.
    • Tan, M-Z.
    • Xu, S-X.
    • Yu, D-S.
    • Shi, X-Z.
    • Wang, M-Y.
  • Source: Pedosphere
  • Volume: 23
  • Issue: 6
  • Year: 2013
  • Summary: The agricultural soil carbon pool plays an important role in mitigating greenhouse gas emission and understanding the soil organic carbon-climate-soil texture relationship is of great significance for estimating cropland soil carbon pool responses to climate change. Using data from 900 soil profiles, obtained from the Second National Soil Survey of China, we investigated the soil organic carbon (SOC) depth distribution in relation to climate and soil texture under various climate regimes of the cold northeast region (NER) and the warmer Huang-Huai-Hai region (HHHR) of China. The results demonstrated that the SOC content was higher in NER than in HHHR. For both regions, the SOC content at all soil depths had significant negative relationships with mean annual temperature (MAT), but was related to mean annual precipitation (MAP) just at the surface 0-20 cm. The climate effect on SOC content was more pronounced in NER than in HHHR. Regional differences in the effect of soil texture on SOC content were not found. However, the dominant texture factors were different. The effect of sand content on SOC was more pronounced than that of clay content in NER. Conversely, the effect of clay on SOC was more pronounced than sand in HHHR. Climate and soil texture jointly explained the greatest SOC variability of 49.0% (0-20 cm) and 33.5% (20-30 cm) in NER and HHHR, respectively. Moreover, regional differences occurred in the importance of climate vs. soil texture in explaining SOC variability. In NER, the SOC content of the shallow layers (0-30 cm) was mainly determined by climate factor, specifically MAT, but the SOC content of the deeper soil layers (30-100 cm) was more affected by texture factor, specifically sand content. In HHHR, all the SOC variability in all soil layers was predominantly best explained by clay content. Therefore, when temperature was colder, the climate effect became stronger and this trend was restricted by soil depth. The regional differences and soil depth influence underscored the importance of explicitly considering them in modeling long-term soil responses to climate change and predicting potential soil carbon sequestration.
  • Authors:
    • Chang, S. X.
    • Wang, S.
    • Jia, Z.
    • Wu, F.
    • Startsev, A.
  • Source: Biology and Fertility of Soils
  • Volume: 49
  • Issue: 5
  • Year: 2013
  • Summary: Biochar produced from plant biomass through pyrolysis has been shown to be much more resistant to biodegradation in the soil as compared with the raw biomass, such as cereal straw that is routinely shredded and discharged on to farm fields in large amounts. Biochar application to soil has also been reported to decrease greenhouse gas (GHG) emissions, although the mechanisms are not fully understood. In this study, the emissions of three main GHGs (CO2, CH4, and N2O) and enzyme activities (urease, beta-glycosidase, and dehydrogenase) were measured during a 100-day laboratory incubation of a Chernozemic soil amended with either straw or its biochar at rates of 0.67 and 1.68 % (based on the amount of C added) for the low and high rates, respectively. The biochar application dramatically reduced N2O emissions, but CO2 or CH4 emissions were not different, as compared with the un-amended soil. At the same C equivalent application rate, CO2 and N2O emission rates were greater while CH4 emission rates were lower in straw than in biochar application treatments. The activities of both the dehydrogenase and beta-glycosidase significantly declined while that of urease significantly increased with the biochar as compared with the straw treatment. We conclude that pyrolysis of cereal straw prior to land application would significantly reduce CO2 and N2O emissions, in association with changed enzyme activities, while increasing the soil C pool through the addition of stable C in the form of biochar.
  • Authors:
    • Maynard, N. G.
    • Huntington, H. P.
    • Chapin, F. S.
    • Tom, S.
    • Pungowiyi, C.
    • Huntington, O. H.
    • Cochran, P.
    • Trainor, S. F.
  • Source: Research Article
  • Volume: 120
  • Issue: 3
  • Year: 2013
  • Summary: Despite a keen awareness of climate change, northern Indigenous Peoples have had limited participation in climate-change science due to limited access, power imbalances, and differences in worldview. A western science emphasis on facts and an indigenous emphasis on relationships to spiritual and biophysical components indicate important but distinct contributions that each knowledge system can make. Indigenous communities are experiencing widespread thawing of permafrost and coastal erosion exacerbated by loss of protective sea ice. These climate-induced changes threaten village infrastructure, water supplies, health, and safety. Climate-induced habitat changes associated with loss of sea ice and with landscape drying and extensive wildfires interact with northern development to bring both economic opportunities and environmental impacts. A multi-pronged approach to broadening indigenous participation in climate-change research should: 1) engage communities in designing climate-change solutions; 2) create an environment of mutual respect for multiple ways of knowing; 3) directly assist communities in achieving their adaptation goals; 4) promote partnerships that foster effective climate solutions from both western and indigenous perspectives; and 5) foster regional and international networking to share climate solutions.
  • Authors:
    • Kelley, J. J.
    • Tans, P. P.
    • Sweeney, C.
    • Welp, L. R.
    • Wofsy, S. C.
    • Stephens, B. B.
    • Patra, P. K.
    • Piper, S. C.
    • Keeling, R. F.
    • Graven, H. D.
    • Daube, B. C.
    • Kort, E. A.
    • Santoni, G. W.
    • Bent, J. D.
  • Source: Report
  • Volume: 341
  • Issue: 6150
  • Year: 2013
  • Summary: Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45 degrees to 90 degrees N but by less than 25% for 10 degrees to 45 degrees N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.
  • Authors:
    • Quideau, S.
    • Pswarayi, A.
    • Nelson, A. G.
    • Frick, B.
    • Spaner, D.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: To investigate intercropping as a management strategy to increase crop productivity and weed suppression in organic systems, spring wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), canola ( Brassica napus L.) and field pea ( Pisum sativum L.) monocultures were compared with two-, three-, and four-crop intercrops containing wheat at two organic and one conventional site in 2006 and 2007, central Alberta, Canada. We measured crop and weed biomass, grain yield, and crop competitiveness against weeds from a replacement design in a completely randomized block experiment. Pea and canola monocrops on organic sites yielded the least of all crop treatments. Conventional crop treatments generally yielded higher than organic treatments. Few land equivalent ratios (LERs) on organic sites were significantly >1.0. Some wheat intercrops without barley showed overyielding (LER >1.0) potential. Most of the significant LERs were from three- and four-crop intercrops. More than 50% of the intercrops on organic sites significantly suppressed weeds (based on relative weed biomass) and most of these intercrops had barley in the mixture. Barley as a sole crop and in intercrops suppressed weeds better than all other intercrops and sole crops. The wheat-canola intercrop exhibited the best weed suppression of the two-crop intercrops on organic and conventional sites. The crop densities used in this study may have contributed to the extremely low pea and canola monocrop yields as well as low LERs. Due to this, our findings should be regarded as showing trends and potential from intercrops only. We therefore recommend further studies to establish ideal densities for the intercrops used.
  • Authors:
    • Michelsen, O.
    • Henriksen, T. M.
    • Korsaeth, A.
    • Roer, A. G.
    • Stromman, A. H.
  • Source: Agricultural Systems
  • Volume: 111
  • Year: 2012
  • Summary: This study assesses the environmental impacts from production of 1 kg barley, oat and spring wheat, in central southeast Norway by means of life cycle assessment. The results were given for twelve impact categories, selected based on relevance to the system. These categories are climate change, fossil depletion, freshwater ecotoxicity, freshwater eutrophication, human toxicity, marine ecotoxicity, marine eutrophication, ozone depletion, particulate matter formation, photochemical oxidant formation, terrestrial acidification and terrestrial ecotoxicity. The assessment covers processes from cradle to farm gate, including all farm activities related to grain cultivation, as well as the production and acquisition of machinery, equipments and buildings, diesel and oil, fertilizer, lime, seeds and pesticides. In order to reveal the importance of system boundaries, factors that are included in this study and often excluded in other studies, such as machinery manufacturing, buildings, pesticide production and use, humus mineralization and NO X loss from use of mineral fertilizer were systematically individually omitted. The sensitivity of the LCA results to several selected parameters governing greenhouse gas emissions and climate change (CC) was evaluated by varying the parameters50% of the default value. The assessment gave a CC impact of 0.79, 0.77 and 0.74 kg CO 2-eq for production of 1 kg barley, oat and spring wheat, respectively. The choice of system boundaries were found to have great impact on the results, and CC impact was reduced by more than 40% when factors that are not commonly reported in literature were excluded. This clearly demonstrates the need of comprehensive documentation of system boundaries in order to perform meaningful comparisons of environmental impact caused by grain production under different conditions. The sensitivity analysis revealed that most of the impact categories were not particularly sensitive to the parameters selected. A 50% change in the emission factor for N 2O emissions from N inputs had highest effect on CC with 11-13%. The highest overall impacts were found for the fraction of mineral fertilizer volatilized as NH 3 and NO X , with 32-53% change in photochemical oxidant and particular matter formation, and terrestrial acidification impact categories.
  • Authors:
    • Kristoffersen, A.
    • Loes, A.
    • Clasen, P.
    • Torp, M.
    • Bernhoft, A.
  • Source: Food Additives and Contaminants Part A-Chemistry Analysis Control Exposure & Risk Assessment
  • Volume: 29
  • Issue: 7
  • Year: 2012
  • Summary: A total of 602 samples of organically and conventionally grown barley, oats and wheat was collected at grain harvest during 2002-2004 in Norway. Organic and conventional samples were comparable pairs regarding cereal species, growing site and harvest time, and were analysed for Fusarium mould and mycotoxins. Agronomic and climatic factors explained 10-30% of the variation in Fusarium species and mycotoxins. Significantly lower Fusarium infestation and concentrations of important mycotoxins were found in the organic cereals. The mycotoxins deoxynivalenol (DON) and HT-2 toxin (HT-2) constitute the main risk for human and animal health in Norwegian cereals. The impacts of various agronomic and climatic factors on DON and HT-2 as well as on their main producers F. graminearum and F. langsethiae and on total Fusarium were tested by multivariate statistics. Crop rotation with non-cereals was found to reduce all investigated characteristics significantly - mycotoxin concentrations as well as various Fusarium infestations. No use of mineral fertilisers and herbicides was also found to decrease F. graminearum, whereas lodged fields increased the occurrence of this species. No use of herbicides was also found to decrease F. langsethiae, but for this species the occurrence was lower in lodged fields. Total Fusarium infestation was decreased with no use of fungicides or mineral fertilisers, and with crop rotation, as well as by using herbicides and increased by lodged fields. Clay and to some extent silty soils seemed to reduce F. graminearum in comparison with sandy soils. Concerning climate factors, low temperature before grain harvest was found to increase DON; and high air humidity before harvest to increase HT-2. F. graminearum was negatively correlated with precipitation in July but correlated with air humidity before harvest. F. langsethiae was correlated with temperature in July. Total Fusarium increased with increasing precipitation in July. Organic cereal farmers have fewer cereal intense rotations than conventional farmers. Further, organic farmers do not apply mineral fertiliser or pesticides (fungicides, herbicides or insecticides), and have less problem with lodged fields. The study showed that these agronomic factors were related to the infestation of Fusarium species and the concentration of mycotoxins. Hence, it is reasonable to conclude that farming system (organic versus conventional) impacts Fusarium infestation, and that organic management tends to reduce Fusarium and mycotoxins. However, Fusarium infestation and mycotoxin concentrations may be influenced by a range of factors not studied here, such as local topography and more local climate, as well as cereal species and variety.
  • Authors:
    • Nerg, A.
    • Kivimaenpaa, M.
    • Hartikainen, K.
    • Holopainen, T.
  • Source: Botany-Botanique
  • Volume: 90
  • Issue: 2
  • Year: 2012
  • Summary: To study the possible differences in tropospheric ozone (O 3) tolerance of oat ( Avena sativa L.) and wheat ( Triticum aestivum L.), two oat and two wheat cultivars were exposed to 0, 50, or 100 nL.L -1 O 3 concentrations in growth chambers. Measurements on volatile organic counpound emission and physiological, biochemical, and leaf structural characteristics were conducted with 2- and 4-week-old seedlings. Neither of the studied species was particularly O 3 sensitive, but O 3 sensitivity should rather be defined on the basis of the characteristics of the cultivars within species. Visible leaf injuries increased with leaf age and with increasing O 3 concentration. Net photosynthesis ( Pn), stomatal conductance ( gs), and chlorophyll fluorescence ( Fv/ Fm) of 2-week-old seedlings were more detrimentally affected by O 3 compared with older seedlings. Wheat generally invested more in photosynthesis and related processes, such as gs, Fv/ Fm, concentrations of Rubisco, chlorophylls and carotenoids, and synthesis of starch compared with oat. O 3 increased Rubisco concentration in 2-week-old and carotenoid concentration in 4-week-old seedlings, especially in wheat. Lower extent of O 3-caused visible leaf injuries in the other oat cultivar can supposedly be explained by its low stomatal conductance and high monoterpene production.
  • Authors:
    • Silvan, N.
    • Minkkinen, K.
    • Saarinen, M.
    • Pearson, M.
    • Laine, J.
  • Source: Forest Ecology and Management
  • Volume: 283
  • Year: 2012
  • Summary: Soil preparation to expedite stand establishment after clearcutting is an extensively applied measure in peatland forest regeneration sites particularly in Fennoscandinavia. Thus far, the impact of preparing peat soil on greenhouse gas fluxes is a chapter unwritten in GHG research on forestry-drained peatlands. Not only is such information vital in order to accurately estimate the GHG balance nationally, it may dictate the very methods used to regenerate forests on peat soils in the future. Over a 22-month period, we studied the impacts of mounding and scalping relative to the control on soil CO2 (heterotrophic peat soil respiration, SRp), CH4, and N2O fluxes along a moisture gradient in a nutrient-poor, clearcut forestry-drained peatland. First, we measured instantaneous gas fluxes (g m(-2) h(-1)) of the microsite types (unprepared, mound, pit, scalp) within a given treatment plot (control, mounding, scalping) in order to estimate their annual rates (g m(-2) a(-1)). Then, we estimated annual flux rates for each treatment comprehensively by considering the surface area-based distribution of microsite types in the corresponding treatment plot, and finally, the overall climatic impact of GHG emissions expressed in terms of CO2 equivalents (100-year GWP) 2-3 years after clearcutting and soil preparation. Compared to the control microsites, instantaneous CO2 emissions from scalps and pits were lower while those from mounds equivalent. However, increased CO2 emissions from the unprepared microsites within prepared plots were observed in respect to those of the control. Comprehensively, the annual CO2 emission rates differed little between treatments, ranging between 929 and 1078 g m(-2) a(-1). Hence, neither mounding nor scalping accelerated annual SRp relative to the control treatment. Annual fluxes of CH4 were dependent on the position of the water table. In our wet block, the mounding treatment led to the greatest annual CH4 emissions (3.62 g m(-2) a(-1)), followed by the control (2.14 g m(-2) a(-1)) and scalping (1.05 g m(-2) a(-1)); in the dry block, however, only the scalping treatment was a net, though minimal, source of CH4 (0.80 g m(-2) a(-1)) while the other two treatments effectively consumed CH4 (mounding -0.16 g m(-2) a(-1); control -0.05 g m(-2) a(-1)). Though annual N2O emission levels were low (0.05-0.08 g m(-2) a(-1)), both soil preparation treatments increased the flux of N2O from peat soil compared to the control. When considering the fluxes of all three greenhouse gases, the cumulative impact of soil preparation (mounding or scalping) on the global warming potential of the nutrient-poor, clearcut peatland forest was negligible in respect to the control.
  • Authors:
    • Sauer, T.
    • Soolaneyakanahally, R.
    • de Gooijer, H.
    • Bentrup, G.
    • Schoeneberger, M.
    • Brendle, J.
    • Zhou, X.
    • Current, D.
  • Source: Journal of Soil and Water Conservation
  • Volume: 67
  • Issue: 5
  • Year: 2012