• Authors:
    • Karki,S.
    • Elsgaard,L.
    • Larke,P. E.
  • Source: Biogeosciences
  • Volume: 12
  • Issue: 2
  • Year: 2015
  • Summary: Cultivation of bioenergy crops in rewetted peatland (paludiculture) is considered as a possible land use option to mitigate greenhouse gas (GHG) emissions. However, bioenergy crops like reed canary grass (RCG) can have a complex influence on GHG fluxes. Here we determined the effect of RCG cultivation on GHG emission from peatland rewetted to various extents. Mesocosms were manipulated to three different ground water levels (GWLs), i.e. 0, -10 and -20 cm below the soil surface in a controlled semi-field facility. Emissions of CO 2 (ecosystem respiration, ER), CH 4 and N 2O from mesocosms with RCG and bare soil were measured at weekly to fortnightly intervals with static chamber techniques for a period of 1 year. Cultivation of RCG increased both ER and CH 4 emissions, but decreased the N 2O emissions. The presence of RCG gave rise to 69, 75 and 85% of total ER at -20, -10 and 0 cm GWL, respectively. However, this difference was due to decreased soil respiration at the rising GWL as the plant-derived CO 2 flux was similar at all three GWLs. For methane, 70-95% of the total emission was due to presence of RCG, with the highest contribution at -20 cm GWL. In contrast, cultivation of RCG decreased N2O emission by 33-86% with the major reductions at -10 and -20 cm GWL. In terms of global warming potential, the increase in CH 4 emissions due to RCG cultivation was more than offset by the decrease in N 2O emissions at -10 and -20 cm GWL; at 0 cm GWL the CH 4 emissions was offset only by 23%. CO 2 emissions from ER were obviously the dominant RCG-derived GHG flux, but aboveground biomass yields, and preliminary measurements of gross photosynthetic production, showed that ER could be more than balanced due to the photosynthetic uptake of CO 2 by RCG. Our results support that RCG cultivation could be a good land use option in terms of mitigating GHG emission from rewetted peatlands, potentially turning these ecosystems into a sink of atmospheric CO 2.
  • Authors:
    • Kodros,J. K.
    • Scott,C. E.
    • Farina,S. C.
    • Lee,Y. H.
    • L'Orange,C.
    • Volckens,J.
    • Pierce,J. R.
  • Source: Atmospheric Chemistry and Physics
  • Volume: 15
  • Issue: 15
  • Year: 2015
  • Summary: Aerosol emissions from biofuel combustion impact both health and climate; however, while reducing emissions through improvements to combustion technologies will improve health, the net effect on climate is largely unconstrained. In this study, we examine sensitivities in global aerosol concentration, direct radiative climate effect, and cloud-albedo aerosol indirect climate effect to uncertainties in biofuel emission factors, optical mixing state, and model nucleation and background secondary organic aerosol (SOA). We use the Goddard Earth Observing System global chemical-transport model (GEOS-Chem) with TwO Moment Aerosol Sectional (TOMAS) microphysics. The emission factors include amount, composition, size, and hygroscopicity, as well as optical mixing-state properties. We also evaluate emissions from domestic coal use, which is not biofuel but is also frequently emitted from homes. We estimate the direct radiative effect assuming different mixing states (homogeneous, core-shell, and external) with and without absorptive organic aerosol (brown carbon). We find the global-mean direct radiative effect of biofuel emissions ranges from -0.02 to +0.06 W m-2 across all simulation/mixing-state combinations with regional effects in source regions ranging from -0.2 to +0.8 W m-2. The global-mean cloud-albedo aerosol indirect effect (AIE) ranges from +0.01 to -0.02 W m-2 with regional effects in source regions ranging from -1.0 to -0.05 W m-2. The direct radiative effect is strongly dependent on uncertainties in emissions mass, composition, emissions aerosol size distributions, and assumed optical mixing state, while the indirect effect is dependent on the emissions mass, emissions aerosol size distribution, and the choice of model nucleation and secondary organic aerosol schemes. The sign and magnitude of these effects have a strong regional dependence. We conclude that the climate effects of biofuel aerosols are largely unconstrained, and the overall sign of the aerosol effects is unclear due to uncertainties in model inputs. This uncertainty limits our ability to introduce mitigation strategies aimed at reducing biofuel black carbon emissions in order to counter warming effects from greenhouse gases. To better understand the climate impact of particle emissions from biofuel combustion, we recommend field/laboratory measurements to narrow constraints on (1) emissions mass, (2) emission size distribution, (3) mixing state, and (4) ratio of black carbon to organic aerosol. © Author(s) 2015.
  • Authors:
    • Liu,Xinsheng
    • Vedlitz,Arnold
    • Stoutenborough,James W.
    • Robinson,Scott
  • Source: Climatic Change
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: Among many potential causes for policymakers' contention over whether there is a largely unified scientific agreement on global warming and climate change (GWCC), one possible factor, according to the information deficit theory, is that the scientists who testified in congressional hearings might be substantially divided in their views and positions associated with GWCC. To clarify this, we perform content analysis of 1350 testimonies from congressional GWCC hearings over a period of 39 years from 1969 to 2007 and use the data derived from this content analysis to provide an overview of scientist witnesses' stances on GWCC. The key findings include: (1) among the scientists' testimonies with an expressed view on whether GWCC is real, a vast majority (86 %) indicates that it is happening; (2) among the scientists' testimonies with an identified stance on whether GWCC is anthropogenic, a great majority of them (78 %) indicates that GWCC is caused, at least to some degree, by human activity; (3) even under Republican controlled congresses, there is still a supermajority (75 %) - among the scientists' testimonies with an expressed position on GWCC existence or GWCC cause - that believes that GWCC is real and that GWCC is anthropogenic; (4) most scientists' testimonies (95 %) endorse pro-action policy to combat GWCC; and (5) the percentages of scientists' views and positions are consistent across different types of scientist testimony groups. Our findings suggest that the scientific information transmitted to Congress is not substantially different from the general agreement in the climate science community.
  • Authors:
    • Schneider, L. C.
    • Burbano, D. V.
    • Lerner, A. M.
    • McGroddy, M. E.
    • Rudel, T. K.
  • Source: Science Journal
  • Volume: 47
  • Issue: 4
  • Year: 2015
  • Summary: Agriculture, particularly pasture, is the second largest source of greenhouse gas emissions from tropical regions. Silvopastoral systems may increase carbon pools in pastures while maintaining productivity. Adding trees to pasture provides carbon sinks in woody biomass, and may improve degraded soils and increase the stability of soil carbon pools. In this study we quantified the biomass carbon stored in spontaneous silvopastoral systems in southeastern Ecuador. We compared the stem density, basal area, aboveground biomass, and organic carbon in the top 20 cm of soil in 100 pastures, ranging from 3 to 250 hectares, in four different communities. Aboveground live woody biomass, calculated using allometric equations and two different wood densities, varied from 10.99 to 66.1 Mg per hectare. Soil organic carbon pools ranged from 85.0 to 97.6 Mg per hectare. Stem density, basal area, and aboveground live biomass all positively correlated with pasture age. We found no relationship between pasture age or stem density and soil organic carbon pools. We measured live woody biomass carbon pools of 34-1070 Mg of carbon per farm in these silvopastoral systems. We found no effects on productivity of the herbaceous layer, suggesting that having a low density of trees in pastures could substantially increase the number of trees and the associated carbon sequestration without affecting cattle production.
  • Authors:
    • Moore,J. R.
    • Watt,M. S.
  • Source: Global Change Biology
  • Volume: 21
  • Issue: 8
  • Year: 2015
  • Summary: Wind is the major abiotic disturbance in New Zealand's planted forests, but little is known about how the risk of wind damage may be affected by future climate change. We linked a mechanistic wind damage model (ForestGALES) to an empirical growth model for radiata pine ( Pinus radiata D. Don) and a process-based growth model (CENW) to predict the risk of wind damage under different future emissions scenarios and assumptions about the future wind climate. The CENW model was used to estimate site productivity for constant CO 2 concentration at 1990 values and for assumed increases in CO 2 concentration from current values to those expected during 2040 and 2090 under the B1 (low), A1 B (mid-range) and A2 (high) emission scenarios. Stand development was modelled for different levels of site productivity, contrasting silvicultural regimes and sites across New Zealand. The risk of wind damage was predicted for each regime and emission scenario combination using the ForestGALES model. The sensitivity to changes in the intensity of the future wind climate was also examined. Results showed that increased tree growth rates under the different emissions scenarios had the greatest impact on the risk of wind damage. The increase in risk was greatest for stands growing at high stand density under the A2 emissions scenario with increased CO 2 concentration. The increased productivity under this scenario resulted in increased tree height, without a corresponding increase in diameter, leading to more slender trees that were predicted to be at greater risk from wind damage. The risk of wind damage was further increased by the modest increases in the extreme wind climate that are predicted to occur. These results have implications for the development of silvicultural regimes that are resilient to climate change and also indicate that future productivity gains may be offset by greater losses from disturbances.
  • Authors:
    • Morrison,Geoffrey M.
    • Yeh,Sonia
    • Eggert,Anthony R.
    • Yang,Christopher
    • Nelson,James H.
    • Greenblatt,Jeffery B.
    • Isaac,Raphael
    • Jacobson,Mark Z.
    • Johnston,Josiah
    • Kammen,Daniel M.
    • Mileva,Ana
    • Moore,Jack
    • Roland-Holst,David
    • Wei,Max
    • Weyant,John P.
    • Williams,James H.
    • Williams,Ray
    • Zapata,Christina B.
  • Source: Climatic Change
  • Volume: 131
  • Issue: 4
  • Year: 2015
  • Summary: Jurisdictions throughout the world are contemplating greenhouse gas (GHG) mitigation strategies that will enable meeting long-term GHG targets. Many jurisdictions are now focusing on the 2020-2050 timeframe. We conduct an inter-model comparison of nine California statewide energy models with GHG mitigation scenarios to 2050 to better understand common insights across models, ranges of intermediate GHG targets (i.e., for 2030), necessary technology deployment rates, and future modeling needs for the state. The models are diverse in their representation of the California economy: across scenarios with deep reductions in GHGs, annual statewide GHG emissions are 8-46 % lower than 1990 levels by 2030 and 59-84 % lower by 2050 (not including the Wind-Water-Solar model); the largest cumulative reductions occur in scenarios that favor early mitigation; non-hydroelectric renewables account for 30-58 % of electricity generated for the state in 2030 and 30-89 % by 2050 (not including the Wind-Water-Solar model) ; the transportation sector is decarbonized using a mix of energy efficiency gains and alternative-fueled vehicles; and bioenergy is directed almost exclusively towards the transportation sector, accounting for a maximum of 40 % of transportation energy by 2050. Models suggest that without new policies, emissions from non-energy sectors and from high-global-warming-potential gases may alone exceed California's 2050 GHG goal. Finally, future modeling efforts should focus on the: economic impacts and logistical feasibility of given scenarios, interactive effects between two or more climate policies, role of uncertainty in the state's long-term energy planning, and identification of pathways that achieve the dual goals of criteria pollutant and GHG emission reduction.
  • Authors:
    • Sainju,U. M.
    • Allen,B. A.
    • Caesar-Tonthat,T.
    • Lenssen,A. W.
  • Volume: 107
  • Issue: 5
  • Year: 2015
  • Summary: Little is known about the long-term management impact on soil C and N contents in the northern Great Plains. We evaluated the 30-yr effect of tillage and cropping sequence combination on dryland crop biomass yield and soil bulk density, soil organic carbon (SOC), soil inorganic carbon (SIC), soil total nitrogen (STN), NH 4-N, and NO 3-N contents at the 0- to 120-cm depth in a Dooley sandy loam (fine loamy, mixed, frigid Typic Argiboroll) in eastern Montana. Treatments were no-till continuous spring wheat ( Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat-barley ( Hordeum vulgare L., 1984-1999) followed by spring wheat-pea ( Pisum sativum L., 2000-2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F, traditional system). Mean annualized crop biomass returned to the soil was 23 to 30% greater in NTCW, STCW, FSTCW, and FSTW-B/P than STW-F. At 0 to 7.5 cm, bulk density was 13 to 21% greater in STW-F, but SOC, SIC, and STN were 12 to 98% greater in STCW than other treatments. Ammonium-N and NO 3-N contents were 25 to 74% greater in FSTCW than other treatments. At other depths, SOC, SIC, STN, NH 4-N and NO 3-N contents varied among treatments. Reduced tillage with increased crop residue returned to the soil increased soil C and N storage in NTCW and STCW, but increased tillage intensity increased mineral N content in FSTCW compared with STW-F. Improved management practices, such as NTCW and STCW, may be adopted to improve dryland soil C and N stocks.
  • Authors:
    • Sharma,R.
    • Chauhan,S. K.
    • Tripathi,A. M.
  • Source: Agroforestry Systems
  • Volume: 90
  • Issue: 4
  • Year: 2015
  • Summary: India is a large developing country with more than seventy per cent population earning their livelihood from diverse land use activities. Changing climate is a worry for the nation but the country cannot afford to slow down the developing/developmental activities. Landuse activities in irrigated agro-ecosystems have started shifting from traditional agriculture to smart agriculture to meet the country’s food requirements and secure livelihood security. But this shift has been achieved at the cost of natural resources and degradation of environment. Realizing the benefits of climate smart agriculture in the changing scenario, farmers are adapting slowly to it but appropriate details of climate vulnerability and package of climate smart agriculture including tree-crop interaction are very limited for adoption. It is important to assess the strengths and weaknesses of carbon sequestration (CS) projects with respect to their practical potential rather than biophysical potential for registration under clean development mechanism for additional income. There is a need to address the technical, economic, legal and social issues of the adopters because they have to lock their land for long time for CS projects, therefore confidence building measures are essentially required to make them aware/motivate for adoption of trees on their farms for mitigation of greenhouse gases (GHGs) and adaptation against changing climate. However, the potential of agroforestry (AF) systems has not been reflected in registration of CS projects due to lack of best practices in AF, procedures and methodologies for carbon accounting, etc., which requires thorough review to develop appropriate models for payments of environmental benefits. Poplar based AF has been considered here as an example to understand the process of accounting CS and its practical applicability for environmental payments. © 2015 Springer Science+Business Media Dordrecht
  • Authors:
    • Traerup,Sara
    • Stephan,Jean
  • Source: Climatic Change
  • Volume: 131
  • Issue: 3
  • Year: 2015
  • Summary: Increasing attention is being given to climate technologies on the international climate change agenda, not least in the agricultural sector and water sectors, and to technologies for adaptation. However investments in technology-based adaptation (seeds, dams, irrigation, etc.) are complicated by the fact that it remains difficult to predict future climate change impacts, especially on a local scale. In addition, evidence for the costs and benefits of implementing adaptation technologies is relatively limited. The analysis presented in this paper shows that there is a large potential for integrating adaptation technologies into the planning and implementation of on-going and future projects. Based on local-level data from a technology needs assessment project in Lebanon, this paper presents two examples of the economic feasibility of implementing adaptation technologies in the agricultural and water sectors. The results show that the technologies can be applied at low cost and with relatively little effort.
  • Authors:
    • van Dijl,E. A.
    • Grogan,K. A.
    • Borisova,T.
  • Source: Journal of Soil and Water Conservation
  • Volume: 70
  • Issue: 4
  • Year: 2015
  • Summary: In the United States, Florida ranks second among states for both value and land area of vegetable production, but this production is affected by periodic droughts. Florida has experienced at least one severe and widespread drought every decade since 1900, and climate change projections show that meteorological droughts will occur more often in the future. While drought and climate change affect the supply side, population growth is expected to affect the demand side of water availability. Given these threats to future water availability, the adoption of drought adaptation and water conservation measures is of increasing importance in Florida. Using a 2013 survey of Florida vegetable growers, this paper addresses two main components of this problem. First, we assess the current rates of adoption of drought adaptation measures. Second, we analyze which factors influence or impede the adoption of these measures to provide policy recommendations to increase adoption in the future. We find low rates of adoption of adaptations, ranging from 13% to 55%, and factors determining who adopts a given adaptation vary by adaptation. Factors can have opposite effects on the probability of adoption across different adaptations. Unlike most previous work, we find that growers with more education have lower rates of adoption of water augmentation measures, and lack of land ownership does not necessarily impede adoption of adaptations with large initial investment.