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1.
Potential Soil C Sequestration on U.S. Agricultural Soils 总被引：1，自引：0，他引：1
Soil carbon sequestration has been suggested as a means to help mitigate atmospheric CO2 increases, however there is limited knowledge aboutthe magnitude of the mitigation potential. Field studies across the U.S. provide information on soil C stock changes that result from changes in agricultural management. However, data from such studies are not readily extrapolated to changes at a national scale because soils, climate, and management regimes vary locally and regionally. We used a modified version of the Intergovernmental Panel on Climate Change (IPCC) soil organic C inventory method, together with the National Resources Inventory (NRI) and other data, to estimate agricultural soil C sequestration potential in the conterminous U.S. The IPCC method estimates soil C stock changes associated with changes in land use and/or land management practices. In the U.S., the NRI provides a detailed record of land use and management activities on agricultural land that can be used to implement the IPCC method. We analyzed potential soil C storage from increased adoption of no-till, decreased fallow operations, conversion of highly erodible land to grassland, and increased use of cover crops in annual cropping systems. The results represent potentials that do not explicitly consider the economic feasibility of proposed agricultural production changes, but provide an indication of the biophysical potential of soil C sequestration as a guide to policy makers. Our analysis suggests that U.S. cropland soils have the potential to increase sequestered soil C by an additional 60–70 Tg (1012g) C yr– 1, over present rates of 17 Tg C yr–1(estimated using the IPCC method), with widespread adoption of soil C sequestering management practices. Adoption of no-till on all currently annually cropped area (129Mha) would increase soil C sequestration by 47 Tg C yr–1. Alternatively, use of no-till on 50% of annual cropland, with reduced tillage practices on the other 50%, would sequester less – about37 Tg C yr–1. Elimination of summer fallow practices and conversionof highly erodible cropland to perennial grass cover could sequester around 20 and 28Tg C yr–1, respectively. The soil C sequestration potentialfrom including a winter cover crop on annual cropping systems was estimated at 40Tg C yr–1. All rates were estimated for a fifteen-yearprojection period, and annual rates of soil C accumulations would be expected to decrease substantially over longer time periods. The total sequestration potential we have estimated for the projection period (83 Tg C yr–1) represents about 5% of 1999total U.S. CO2 emissions or nearly double estimated CO2 emissionsfrom agricultural production (43 Tg C yr–1). For purposes ofstabilizing or reducing CO2 emissions, e.g., by 7% of 1990 levels asoriginally called for in the Kyoto Protocol, total potential soil C sequestration would represent 15% of that reduction level from projected 2008 emissions(2008 total greenhouse gas emissions less 93% of 1990 greenhouse gasemissions). Thus, our analysis suggests that agricultural soil C sequestration could play a meaningful, but not predominant, role in helping mitigate greenhouse gas increases. 相似文献
2.
Carbon sequestration in agricultural soils is frequently promoted as a practical solution for slowing down the rate of increase
of CO2 in the atmosphere. Consequently, there is a need to improve our understanding of how land management practices may affect
the net removal of greenhouse gases (GHG) from the atmosphere. In this paper we examine the role of agriculture in influencing
the GHG budget and briefly discuss the potential for carbon mitigation by agriculture. We also examine the opportunities that
exist for increasing soil C sequestration using management practices such as reduced tillage, reduced frequency of summer
fallowing, introduction of forage crops into crop rotations, conversion of cropland to grassland and nutrient addition via
fertilization. In order to provide information on the impact of such management practices on the net GHG budget we ran simulations
using CENTURY (a C model) and DNDC (a N model) for five locations across Canada, for a 30-yr time period. These simulations
provide information on the potential trade-off between C sequestration and increased N2O emissions. Our model output suggests that conversion of cropland to grassland will result in the largest reduction in net
GHG emissions, while nutrient additions via fertilizers will result in a small increase in GHG emissions. Simulations with
the CENTURY model also indicated that favorable growing conditions during the last 15 yr could account for an increase of
6% in the soil C at a site in Lethbridge, Alberta.
Presented at the International Workshop on Reducing Vulnerability of Agriculture and Forestry to Climate Variability and Climate
Change, Ljubljana, Slovenia, 7–9 October 2002. 相似文献
3.
Activities to reduce net greenhouse gas emissions by biological soil or forest carbon sequestration predominantly utilize
currently known, readily implementable technologies. Many other greenhouse gas emission reduction options require future technological
development or must wait for turnover of capital stock. Carbon sequestration options in soils and forests, while ready to
go now, generally have a finite life, allowing use until other strategies are developed. This paper reports on an investigation
of the competitiveness of biological carbon sequestration from a dynamic and multiple strategy viewpoint. Key factors affecting
the competitiveness of terrestrial mitigation options are land availability and cost effectiveness relative to other options
including CO2 capture and storage, energy efficiency improvements, fuel switching, and non-CO2 greenhouse gas emission reductions. The analysis results show that, at lower CO2 prices and in the near term, soil carbon and other agricultural/forestry options can be important bridges to the future,
initially providing a substantial portion of attainable reductions in net greenhouse gas emissions, but with a limited role
in later years. At higher CO2 prices, afforestation and biofuels are more dominant among terrestrial options to offset greenhouse gas emissions. But in
the longer run, allowing for capital stock turnover, options to reduce greenhouse gas emissions from the energy system and
biofuels provide an increasing share of potential reductions in total US greenhouse gas emissions. 相似文献
4.
Previous research has demonstrated that soil carbon sequestration through adoption of conservation tillage can be economically profitable depending on the value of a carbon offset in a greenhouse gas (GHG) emissions market. However adoption of conservation tillage also influences two other potentially important factors, changes in soil N2O emissions and CO2 emissions attributed to changes in fuel use. In this article we evaluate the supply of GHG offsets associated with conservation tillage adoption for corn-soy-hay and wheat-pasture systems of the central United States, taking into account not only the amount of carbon sequestration but also the changes in soil N2O emission and CO2 emissions from fuel use in tillage operations. The changes in N2O emissions are derived from a meta-analysis of published studies, and changes in fuel use are based on USDA data. These are used to estimate changes in global warming potential (GWP) associated with adoption of no-till practices, and the changes in GWP are then used in an economic analysis of the potential supply of GHG offsets from the region. Simulation results demonstrate that taking N2O emissions into account could result in substantial underestimation of the potential for GHG mitigation in the central U.S. wheat pasture systems, and large over-estimation in the corn-soy-hay systems. Fuel use also has quantitatively important effects, although generally smaller than N2O. These findings suggest that it is important to incorporate these two effects in estimates of GHG offset potential from agricultural lands, as well as in the design of GHG offset contracts for more complete accounting of the effect that no-till adoption will have on greenhouse gas emissions. 相似文献
5.
L. D. Danny Harvey 《Climatic change》2004,63(3):259-290
Carbon sequestration is increasingly being promoted as a potential response to the risks of unrestrained emissions of CO2, either in place of or as a complement to reductions in the use of fossil fuels. However, the potential role of carbon sequestration as an (at-least partial) substitute for reductions in fossil fuel use can be properly evaluated only in the context of a long-term acceptable limit (or range of limits) to the increase in atmospheric CO2 concentration, taking into account the response of the entire carbon cycle to artificial sequestration. Under highly stringent emission-reduction scenarios for non-CO2 greenhouse gases, 450 ppmv CO2 is the equivalent, in terms of radiative forcing of climate,to a doubling of the pre-industrial concentration of CO2. It is argued in this paper that compliance with the United Nations Framework Convention on Climate Change (henceforth, the UNFCCC) implies that atmospheric CO2 concentration should be limited, or quickly returned to, a concentration somewhere below 450 ppmv. A quasi-one-dimensional coupled climate-carbon cycle model is used to assess the response of the carbon cycle to idealized carbon sequestration scenarios. The impact on atmospheric CO2 concentration of sequestering a given amount of CO2 that would otherwise be emitted to the atmosphere, either in deep geological formations or in the deep ocean, rapidly decreases over time. This occurs as a result of a reduction in the rate of absorption of atmospheric CO2 by the natural carbon sinks (the terrestrial biosphere and oceans) in response to the slower buildup of atmospheric CO2 resulting from carbon sequestration. For 100 years of continuous carbon sequestration, the sequestration fraction (defined as the reduction in atmospheric CO2 divided by the cumulative sequestration) decreases to 14% 1000 years after the beginning of sequestration in geological formations with no leakage, and to 6% 1000 years after the beginning of sequestration in the deep oceans. The difference (8% of cumulative sequestration) is due to an eflux from the ocean to the atmosphere of some of the carbon injected into the deep ocean.The coupled climate-carbon cycle model is also used to assess the amount of sequestration needed to limit or return the atmospheric CO2 concentration to 350–400 ppmv after phasing out all use of fossil fuels by no later than 2100. Under such circumstances, sequestration of 1–2 Gt C/yr by the latter part of this century could limit the peak CO2 concentration to 420–460 ppmv, depending on how rapidly use of fossilfuels is terminated and the strength of positive climate-carbon cycle feedbacks. To draw down the atmospheric CO2 concentration requires creating negative emissions through sequestration of CO2 released as a byproduct of the production of gaseous fuels from biomass primary energy. Even if fossil fuel emissions fall to zero by 2100, it will be difficult to create a large enough negative emission using biomass energy to return atmospheric CO2 to 350 ppmv within 100 years of its peak. However, building up soil carbon could help in returning CO2 to 350 ppmv within 100 years of its peak. In any case, a 100-year period of climate corresponding to the equivalent of a doubled-CO2 concentration would occur before temperatures decreased. Nevertheless, returning the atmospheric CO2concentration to 350 ppmv would reduce longterm sea level rise due to thermal expansion and might be sufficient to prevent the irreversible total melting of the Greenland ice sheet, collapse of the West Antarctic ice sheet, and abrupt changes in ocean circulation that might otherwise occur given a prolonged doubled-CO2 climate. Recovery of coral reef ecosystems, if not already driven to extinction, could begin. 相似文献
6.
Mitigating the potential large negative impacts of a change in the earth's climate will require strong and definite actions in the different economic sectors, particularly within agriculture and forestry. Specifically, soils deserve a close examination due to their large carbon mitigation potential. The Kyoto protocol establishes the possibility for crediting greenhouse gas emission reductions from forestry and agriculture activities. In most circumstances, particularly those regarding developing countries, greenhouse gas mitigation activities will be carried out through projects. These projects will have to meet a series of criteria, for the carbon benefits to be measurable, transparent, verifiable and certified. These criteria include: establishing credible baselines (without-project or reference scenario), additionality, permanence, quantifying and reducing potential leakage of greenhouse gases across project borders, coping with natural or human induced risks, accurately measuring changes in carbon stocks using carbon accounting techniques, and – in the case of the Clean DevelopmentMechanism – resulting in sustainable development benefits. In this paper we describe the methods and approaches that have been developed to cope with the different criteria and discuss their implications for carbon sequestration in soils. Soil carbon represents the largest carbon pool of terrestrial ecosystems, and has been estimated to have one of the largest potentials to sequester carbon worldwide. However, getting credits from soil carbon sequestration through project activities presents several challenges: the need to monitor small incremental changes in soil carbon content relative to large carbon pools, long-time periods to accrue the full carbon benefits, high local variability of soil carbon content, and relatively costly soil carbon measurement procedures. Also, the responses of soil C stocks to forestry and agriculture activities are complex and need careful attention. Specifically, the time dynamics of soil C responses to land use changes, the diversity of soil types, soil-plant interactions, and the availability of accurate soil C inventories, should be considered to successfully implement LULUCF projects. 相似文献
7.
Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO2–Eq yr–1 in1990 to 52 Tg CO2–Eq yr–1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO2–Eq yr–1 (L), 42 TgCO2–Eq yr–1 (M) or 36 Tg CO2–Eq yr–1 (H). Among thesink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH4 and N2O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992). 相似文献
8.
Carbon dioxide (CO2) sequestration has been proposed as a key component in technological portfolios for managing anthropogenic climate change, since it may provide a faster and cheaper route to significant reductions in atmospheric CO2 concentrations than abating CO2 production. However, CO2 sequestration is not a perfect substitute for CO2 abatement because CO2 may leak back into the atmosphere (thus imposing future climate change impacts) and because CO2 sequestration requires energy (thus producing more CO2 and depleting fossil fuel resources earlier). Here we use analytical and numerical models to assess the economic efficiency of CO2 sequestration and analyze the optimal timing and extent of CO2 sequestration. The economic efficiency factor of CO2 sequestration can be expressed as the ratio of the marginal net benefits of sequestering CO2 and avoiding CO2 emissions. We derive an analytical solution for this efficiency factor for a simplified case in which we account for CO2 leakage, discounting, the additional fossil fuel requirement of CO2 sequestration, and the growth rate of carbon taxes. In this analytical model, the economic efficiency of CO2 sequestration decreases as the CO2 tax growth rate, leakage rates and energy requirements for CO2 sequestration increase. Increasing discount rates increases the economic efficiency factor. In this simple model, short-term sequestration methods, such as afforestation, can even have negative economic efficiencies. We use a more realistic integrated-assessment model to additionally account for potentially important effects such as learning-by-doing and socio-economic inertia on optimal strategies. We measure the economic efficiency of CO2 sequestration by the ratio of the marginal costs of CO2 sequestration and CO2 abatement along optimal trajectories. We show that the positive impacts of investments in CO2 sequestration through the reduction of future marginal CO2 sequestration costs and the alleviation of future inertia constraints can initially exceed the marginal sequestration costs. As a result, the economic efficiencies of CO2 sequestration can exceed 100% and an optimal strategy will subsidize CO2 sequestration that is initially more expensive than CO2 abatement. The potential economic value of a feasible and acceptable CO2 sequestration technology is equivalent – in the adopted utilitarian model – to a one-time investment of several percent of present gross world product. It is optimal in the chosen economic framework to sequester substantial CO2 quantities into reservoirs with small or zero leakage, given published estimates of marginal costs and climate change impacts. The optimal CO2 trajectories in the case of sequestration from air can approach the pre-industrial level, constituting geoengineering. Our analysis is silent on important questions (e.g., the effects of model and parametric uncertainty, the potential learning about these uncertainties, or ethical dimension of such geoengineering strategies), which need to be addressed before our findings can be translated into policy-relevant recommendations. 相似文献
9.
F. Blaine Metting Jeffrey L. Smith Jeffrey S. Amthor R. Cesar Izaurralde 《Climatic change》2001,51(1):11-34
Fossil fuel use and land use change that began over 200 years ago are driving the rapid increase in atmospheric content of CO2 and other greenhouse gases that may be impacting climatic change (Houghton et al., 1996). Enhanced terrestrial uptake of CO2 over the next 50 to 100 years has been suggested as a way to reclaim the 150 or more Pg carbon (C) lost to the atmosphere from vegetation and soil since 1850 as a consequence of land use change (Batjes, 1999; Lal et al., 1998a; Houghton, 1995), thus effectively `buying time' for the development and implementation of new longer term technical solutions, such as C-free fuels. The ultimate potential for terrestrial C sequestration is not known, however, because we lack adequate understanding of (1) the biogeochemical mechanisms responsible for C fluxes and storage potential on the molecular, landscape, regional, and global scales, and (2) the complex genetic and physiological processes controlling key biological and ecological phenomena. Specifically, the structure and dynamics of the belowground component of terrestrial carbon pools, which accounts for two-thirds of global terrestrial organic C stocks, is poorly understood. Focusing primarily on forests, croplands and grasslands, the purpose of this chapter is to consider innovative technology for enhancing C sequestration in terrestrial ecosystems and address the scientific issues related to better understanding of soil C sequestration potential through appropriate and effective approaches to ecosystem management. 相似文献
10.
Potential of Desertification Control to Sequester Carbon and Mitigate the Greenhouse Effect 总被引：16，自引：0，他引：16
R. Lal 《Climatic change》2001,51(1):35-72
There is a strong link between desertification of the drylands and emission of CO2 from soil and vegetation to the atmosphere. Thus, there is a strong need to revisit the desertification process so that its reversal can lead to C sequestration and mitigation of the accelerated greenhouse effect. Drylands of the world occupy 6.31 billion ha (Bha) or 47% ofthe earth's land area distributed among four climates: hyper-arid (1.0 Bha), arid (1.62 Bha), semi-arid (2.37 Bha) and dry sub-humid (1.32 Bha). Principal soils of drylands are Aridisols (1.66 Bha), Entisols (1.92 Bha), Alfisols (0.38 Bha), Vertisols (0.21 Bha) and others (1.27 Bha). Drylands occur in all continents covering 2.01 Bha in Africa, 2.00 Bha in Asia, 0.68Bha in Australia, 1.32 Bha in the Americas and 0.30 Bha in Europe. Desertification, degradation of soil and vegetation in drylands resulting from climatic and anthropogenic factors, affects about 1.137 Bha of soils and an additional 2.576 Bha of rangeland vegetation. The rate of desertification is estimated at 5.8 million hectares (Mha) per year. Desertification is a biophysical process (soil, climate and vegetation) driven by socio-economic and political factors. The principal biophysical processes involved, accelerated soil erosion by water and wind and salinization, reduce soil quality and effective rooting depth, decrease vegetal cover, reduce biomass productivity, and accentuate vagaries of climateespecially low and variable rainfall. Major consequences of desertification include reduction in the total soil C pool and transfer of C from soil to the atmosphere. Total historic loss of C due to desertification may be 19 to 29 Pg. The rate of C emission from drylands due to accelerated soil erosion is estimated at 0.227 to 0.292 Pg C y–1. Therefore, desertification control and restoration of degraded soils and ecosystems would improve soil quality, increase the pool of C in soil and biomass, and induce formation of secondary carbonates leading to a reduction of C emissions to the atmosphere. Desertification control and soil restoration are affected by establishing vegetative cover with appropriate species, improving water use efficiency, using supplemental irrigation including water harvesting, developing a strategy of integrated nutrient management for soil fertility enhancement, and adopting improved farming systems. Adoption of these improved practices also have hidden carbon costs, especially those due to production and application of herbicides and nitrogen fertilizers, pumping irrigation water etc. Restoration of eroded and salt-affected soils is important to C sequestration. Total potential of C sequestration in drylands through adoption of these measures is 0.9 to 1.9Pg C y–1 for a 25- to 50-year period beyond which the rate of sequestration is often too low to be important. In addition to enhancing productivity and food security, C sequestration in soils and ecosystem has numerous ancillary benefits. Therefore, identification and implementation of policies is important to facilitate adoption of recommended practices and for commodification of carbon. 相似文献
11.
Fengxiang X. Han M. John Plodinec Yi Su David L. Monts Zhongpei Li 《Climatic change》2007,84(2):191-202
Analyses of regional carbon sources and sinks are essential to assess the economical feasibility of various carbon sequestration
technologies for mitigating atmospheric CO2 accumulation and for preventing global warming. Such an inventory is a prerequisite for regional trading of CO2 emissions. As a U.S. Department of Energy Southeast Regional Carbon Sequestration Partner, we have estimated the state-level
terrestrial carbon pools in the southeast and south-central US. This region includes: Alabama, Arkansas, Florida, Georgia,
Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Texas, and Virginia. We have also projected the potential
for terrestrial carbon sequestration in the region. Texas is the largest contributor (34%) to greenhouse gas emission in the
region. The total terrestrial carbon storage (forest biomass and soils) in the southeast and south-central US is estimated
to be 130 Tg C/year. An annual forest carbon sink (estimated as 76 Tg C/year) could compensate for 13% of the regional total
annual greenhouse gas emission (505 Tg C, 1990 estimate). Through proper policies and the best land management practices,
54 Tg C/year could be sequestered in soils. Thus, terrestrial sinks can capture 23% of the regional total greenhouse emission
and hence are one of the most cost-effective options for mitigating greenhouse emission in the region. 相似文献
12.
Designing effective mitigation policies for greenhouse gas (GHG) emissions from agriculture requires understanding the mechanisms by which management practices affect emissions in different agroclimatic conditions. Agricultural GHG emissions and carbon sequestration potentials have been extensively studied in the Mediterranean biome, which is a biodiversity hot spot that is highly vulnerable to environmental changes. However, the absolute magnitude of GHG emissions and the extent to which research efforts match these emissions in each production system, are unknown. Here, we estimated GHG emissions and potential carbon sinks associated with crop and livestock production systems in the Mediterranean biome, covering 31 countries and assessing approximately 10,000 emission items. The results were then combined with a bibliometric assessment of 797 research publications to compare emissions estimates obtained with research efforts for each of the studied items. Although the magnitude of GHG emissions from crop production and the associated carbon sequestration potential (261 Tg CO2eq yr−1) were nearly half of those from livestock production (367 Tg CO2eq yr−1), mitigation research efforts were largely focused on the former. As a result, the relative research intensity, which relates the number of publications to the magnitude of emissions, is nearly one order of magnitude higher for crop production than for livestock production (2.6 and 0.4 papers Tg CO2eq−1, respectively). Moreover, this mismatch is even higher when crop and livestock types are studied separately, which indicates major research gaps associated with grassland and many strategic crop types, such as fruit tree orchards, fiber crops, roots and tubers. Most life cycle assessment studies do not consider carbon sequestration, although this single process has the highest magnitude in terms of annual CO2eq. In addition, these studies employ Tier 1 IPCC factors, which are not suited for use in Mediterranean environments. Our analytical results show that a strategic plan is required to extend on-site field GHG measurements to the Mediterranean biome. Such a plan needs to be cocreated among stakeholders and should be based on refocusing research efforts to GHG balance components that have been afforded less attention. In addition, the outcomes of Mediterranean field studies should be integrated into life cycle assessment-based carbon footprint analyses in order to avoid misleading conclusions. 相似文献
13.
Soil Carbon: Policy and Economics 总被引：4，自引：2，他引：4
Agricultural soils provide a prospective way of mitigating the increasing atmospheric concentration of CO2. A number of agricultural practices are known to stimulate the accumulation of additional soil carbon and early indications are that some might sequester carbon at relatively modest costs with generally positive environmental effects. We discuss, under 10 themes, policy and economic issues that will determine whether programs for sequestration of carbon in agricultural soils can succeed. The issues involve contexts for implementation, economics, private property rights, agricultural policy, and institutional and social structures. Ultimately, success will depend on the incentive structure developed and the way in which carbon sequestration is integrated into the total fabric of agricultural policy. 相似文献
14.
Carbon Sequestration in Arable Soils is Likely to Increase Nitrous Oxide Emissions,Offsetting Reductions in Climate Radiative Forcing 总被引：5，自引：0，他引：5
Strategies for mitigating the increasing concentration of carbon dioxide (CO2) in the atmosphere include sequestering carbon (C) in soils and vegetation of terrestrial ecosystems. Carbon and nitrogen
(N) move through terrestrial ecosystems in coupled biogeochemical cycles, and increasing C stocks in soils and vegetation
will have an impact on the N cycle. We conducted simulations with a biogeochemical model to evaluate the impact of different
cropland management strategies on the coupled cycles of C and N, with special emphasis on C-sequestration and emission of
the greenhouse gases methane (CH4) and nitrous oxide (N2O). Reduced tillage, enhanced crop residue incorporation, and farmyard manure application each increased soil C-sequestration,
increased N2O emissions, and had little effect on CH4 uptake. Over 20 years, increases in N2O emissions, which were converted into CO2-equivalent emissions with 100-year global warming potential multipliers, offset 75–310% of the carbon sequestered, depending
on the scenario. Quantification of these types of biogeochemical interactions must be incorporated into assessment frameworks
and trading mechanisms to accurately evaluate the value of agricultural systems in strategies for climate protection. 相似文献
15.
Considering the influence of sequestration duration and carbon saturation on estimates of soil carbon capacity 总被引：10，自引：0，他引：10
Rates of soil C sequestration have previously been estimated for a number of different land management activities, and these
estimates continue to improve as more data become available. The time over which active sequestration occurs may be referred
to as the sequestration duration. Integrating soil C sequestration rates with durations provides estimates of potential change
in soil C capacity and more accurate estimates of the potential to sequester C. In agronomic systems, changing from conventional
plow tillage to no-till can increase soil C by an estimated 16±3%, whereas increasing rotation intensity can increase soil
C by an estimated 6±3%. The increase in soil C following a change in rotation intensity, however, may occur over a slightly
longer period (26 yr) than that for tillage cessation (21 yr). Sequestration strategies for grasslands have, on average, longer
sequestration durations (33 yr) than for croplands. Estimates for sequestration rates and durations are mean values and can
differ greatly between individual sites and management practices. As the annual sequestration rate declines over the sequestration
duration period, soil C approaches a new steady state. Sequestration duration is synonymous with the time to which soil C
steady state is reached. However, soils could potentially sequester additional C following additional changes in management
until the maximum soil C capacity, or soil C saturation, is achieved. Carbon saturation of the soil mineral fraction is not
well understood, nor is it readily evident. We provide evidence of soil C saturation and we discuss how the steady state C
level and the level of soil C saturation together influence the rate and duration of C sequestration associated with changes
in land management. 相似文献
16.
Carbon Sequestration and the Restoration of Land Health 总被引：1，自引：0，他引：1
Andres Arnalds 《Climatic change》2004,65(3):333-346
Carbon sequestration, the conversion of greenhouse gas CO2 toorganic matter, offers a powerful tool with which to combat climate change. The enlargement of carbon sinks stored in soil and biota is an essential tool in buying time while mankind seeks means to reduce emissions of greenhouse gases and to reduce the elevated levels of atmospheric CO2. Carbon sequestration within the context of the Kyoto Protocol of the United Nations Framework Convention on Climate Change (UNFCCC) also has great potential as an incentive for combating land degradation and desertification and restoring fertility to degraded land.Decisions regarding carbon sinks during finalization of the operational details of the Kyoto Protocol in 2001 fit well the needs of countries facing land degradation and desertification. However, incentives for such mitigation through the Clean Development Mechanism of the protocol are limited to forestry issues. Iceland provides a good example of the multiple role of carbon sequestration in meeting national commitments to UNFCCC, conserving and restoring biological diversity, combating soil erosion, revegetation of eroded land and reforestation. Linking carbon sequestration with such goals has resulted in increased funds for soil conservation and restoration of degraded land in Iceland. 相似文献
17.
Arctic ecosystems could provide a substantial positive feedback to global climate change if warming stimulates below-ground CO2 release by enhancing decomposition of bulk soil organic matter reserves.Ecosystem respiration during winter is important in this context because CO2 release from snow-covered tundra soils is a substantial component of annual net carbon (C) balance, and because global climate models predict that the most rapid rises in regional air temperature will occur in the Arctic during winter. In this manipulative field study, the relative contributions of plant and bulk soil organic matter C pools to ecosystem CO2 production in mid-winter were investigated. We measured CO2 efflux rates in Swedish sub-arctic heath tundra from control plots and from plots that had been clipped in the previous growing season to disrupt plant activity. Respiration derived from recently-fixed plant C (i.e., plant respiration, and respiration associated with rhizosphere exudates and decomposition of fresh litter) was the principal source of CO2 efflux, while respiration associated with decomposition of bulk soil organic matter was low, and appeared relatively insensitive to temperature. These results suggest that warmer mid-winter temperatures in the Arctic may have a much greater impact on the cycling of recently-fixed, plant-associated C pools than on the depletion of tundra bulk soil C reserves, and consequently that there is a low potential for significant initial feedbacks from arctic ecosystems to climate change during mid-winter. 相似文献
18.
S. Monni M. Peltoniemi T. Palosuo A. Lehtonen R. Mäkipää I. Savolainen 《Climatic change》2007,81(3-4):391-413
Uncertainty analysis facilitates identification of the most important categories affecting greenhouse gas (GHG) inventory uncertainty and helps in prioritisation of the efforts needed for development of the inventory. This paper presents an uncertainty analysis of GHG emissions of all Kyoto sectors and gases for Finland consolidated with estimates of emissions/removals from LULUCF categories. In Finland, net GHG emissions in 2003 were around 69 Tg (±15 Tg) CO2 equivalents. The uncertainties in forest carbon sink estimates in 2003 were larger than in most other emission categories, but of the same order of magnitude as in carbon stock change estimates in other land use, land-use change and forestry (LULUCF) categories, and in N2O emissions from agricultural soils. Uncertainties in sink estimates of 1990 were lower, due to better availability of data. Results of this study indicate that inclusion of the forest carbon sink to GHG inventories reported to the UNFCCC increases uncertainties in net emissions notably. However, the decrease in precision is accompanied by an increase in the accuracy of the overall net GHG emissions due to improved completeness of the inventory. The results of this study can be utilised when planning future GHG mitigation protocols and emission trading schemes and when analysing environmental benefits of climate conventions. 相似文献
19.
Greenhouse gas (GHG) offsets are a central feature of most regional and national cap-and-trade systems. A greenhouse offset credit represents a tonne of carbon dioxide equivalent (CO2e) reduced, avoided or sequestered by a project implemented specifically to compensate for emissions occurring elsewhere. Several existing modelling studies estimate the technically and economically achievable supply of GHG offsets from uncapped sources in the US. This analysis is among the few that consider how the design of offset protocols – and the corresponding rules for eligibility, measuring, verifying and awarding offsets – might impact actual offset crediting and the realization of GHG mitigation potential. The presented analysis demonstrates how rules for each of these factors could impact the supply of offset credits, as well as the emissions-reduction benefits of an offset programme. Findings indicate that although lenient offset rules and protocols may bring several times more credits to market than a conservative approach, these gains in offset supply would come at a significant cost to the effectiveness of the cap-and-trade system in achieving its central purpose: reducing overall GHG emissions. In particular, lenient rules and protocols could conceivably lead US emissions to exceed legislative targets by as much as 500 million tonnes CO2e in 2020. 相似文献
20.
Melisa Pollak Sarah Johnson Phillips Shalini Vajjhala 《Global Environmental Change》2011,21(2):313-323
Carbon capture and storage (CCS) is considered by some to be a promising technology to reduce greenhouse gas emissions, and advocates are seeking policies to facilitate its deployment. Unlike many countries, which approach the development of policies for geologic storage (GS) of carbon dioxide (CO2) with nearly a blank slate, the U.S. already has a mature policy regime devoted to the injection of CO2 into deep geologic formations. However, the existing governance of CO2 injection is designed to manage enhanced oil recovery (EOR), and policy changes would be needed to manage the risks and benefits of CO2 injection for the purpose of avoiding GHG emissions. We review GS policy developments at both the U.S. federal and state levels, including original research on state GS policy development. By applying advocacy coalition framework theory, we identify two competing coalitions defined by their beliefs about the primary purpose of CO2 injection: energy supply or greenhouse gas (GHG) emission reductions. The established energy coalition is the beneficiary of the current policy regime. Their vision of GS policy is protective: to minimize harm to fossil energy industries if climate policy were to be enacted. In contrast, the newly formed climate coalition seeks to change existing GS policy to support their proactive vision: to maximize GHG reductions using CCS when climate policy is enacted. We explore where and at what scale legislation emerges and examine which institutions gain prominence as drivers of policy change. Through a detailed textual analysis of the content of state GS legislation, we find that the energy coalition has had greater success than the climate coalition in shaping state laws to align with its policy preferences. It has enshrined its view of the purpose of CO2 injection in state legislation, delegated authority for GS to state agencies aligned with the existing policy regime, and protected the EOR status quo, while creating new opportunities for EOR operators to profit from the storage of CO2 The climate coalition's objective of proactively putting GS policy in place has been furthered, and important progress has been made on commonly held concerns, such as the resolution of property rights issues, but the net result is policy change that does not significantly revise the existing policy regime. 相似文献