Land use decision modeling with dynamically updated soil carbon emission rates

Soil carbon can be sequestered through different land management options depending on the soil carbon status at the beginning of a management period. This initial status results from a given soil management history in a given soil climate regime. Similarly, the prediction of future carbon storage depends on the time sequence of future soil management. Unfortunately, the number of possible management trajectories reaches non-computable levels so fast that explicit representations of management trajectories are impractical for most existing land use decision models. Consequently, the impact of different management trajectories has been ignored. This article proposes a computationally feasible mathematical programming method for integration of soil status dependent sequestration rates in land use decision optimization models. The soil status is represented by an array of adjacent status classes. For each combination of soil management and initial soil status class, transition probabilities of moving into a new or staying in the same status class are computed. Subsequently, these probabilities are used in dynamic equations to update the soil status level before and after each new soil management period. To illustrate the impacts of the proposed method, a simple hypothetical land use decision model is solved for alternative specifications.Soil carbon sequestration, Sink dynamics, Mathematical programming, Land use, Optimization, Agriculture, Forestry, Greenhouse gas mitigation

The effects of hyperglycaemic hypoxia on rectification in rat dorsal root axons

1. Electrotonic responses to 150 ms current pulses were recorded from isolated rat dorsal roots incubated for at least 3 h with either normal (5 mM) or high (25 mM) D-glucose solutions, and with either normal (25 mM) or low (5 mM) bicarbonate concentrations. 2. On replacement of O2 by N2 for 50 min, all the roots depolarized, but the changes in electrotonus differed systematically. With normal glucose, the depolarization was accompanied by an increase in input conductance. In contrast, for the hyperglycaemic roots the depolarization was slower and accompanied by a fall in input conductance which was exacerbated in low bicarbonate concentrations. 3. The changes induced by hyperglycaemic hypoxia in low bicarbonate could be mimicked by exposure of the roots either to 100% CO2 or to a combination of 3 mM tetraethylammonium chloride and 3 mM 4-aminopyridine, to block both fast and slow potassium channels. 4. These results indicate that the primary mechanism of hypoxic depolarization of these sensory axons is altered by hyperglycaemia. In normoglycaemia, the changes in electrotonus are consistent with an increase in axonal potassium conductance. The block of potassium channels seen in hyperglycaemic hypoxia is attributed to intra-axonal acidification by anaerobic glycolysis and may contribute to the pathogenesis of diabetic neuropathy

The paradox between resistance to hypoxia and liability to hypoxic damage in hyperglycemic peripheral nerves. Evidence for glycolysis involvement

Isolated ventral and dorsal rat spinal roots incubated in normal (2.5 mM) or high glucose (25 mM) concentrations or in high concentrations of other hexoses were exposed transiently to hypoxia (30 min) in a solution of low buffering power. Compound nerve action potentials, extracellular direct current potentials, and interstitial pH were continuously recorded before, during, and after hypoxia. Ventral roots incubated in 25 mM D-glucose showed resistance to hypoxia. Dorsal roots, on the other hand, revealed electrophysiological damage by hyperglycemic hypoxia as indicated by a lack of posthypoxic recovery. In both types of spinal roots, interstitial acidification was most pronounced during hyperglycemic hypoxia. The changes in the sensitivity to hypoxia induced by high concentrations of D-glucose were imitated by high concentrations of D-mannose. In contrast, D-galactose, L-glucose, D-fructose, and L-fucose did not have such effects. Resistance to hypoxia, hypoxia-generated interstitial acidification, and hypoxia-induced electrophysiological damage were absent after pharmacological inhibition of nerve glycolysis with iodoacetate. These observations indicate 1) that enhanced anaerobic glycolysis produces resistance to hypoxia in hyperglycemic peripheral nerves and 2) that acidification may impair the function of peripheral axons when anaerobic glycolysis proceeds in a tissue with reduced buffering power

Greenhouse Gas Mitigation through Agriculture

Environmental Economics and Policy, Q10, Q55, Q58,

Dynamic Economic Analysis of Perennial Energy Crops - EffectS of The CAP Reform on Biomass Supply in Greece

Energy from the biomass of perennial crops can offset emissions of greenhouse gases from fossil fuel combustion and increase energy self sufficiency. This study uses a dynamic, multi-farm, mathematical programming model to analyze the impact of the Common Agricultural Policy reform in 2003 on biomass supply from the Kopais plain in central Greece. The perennial energy crops under review are Arundo donax L. (Giant Reed), Miscanthus x giganteus (Miscanthus), Panicum virgatum L. (Switchgrass) and Cynara cardunculus L. (Cardoon). Farm survey results from 40 farms are processed with the Biomass Economic Evaluation model to obtain micro-economic data for both conventional and energy crops. Policy simulations with the multi-farm model show that the 2003 policy reform with decoupled subsidies except for cotton and energy crops lowers the cost of biomass between 2 and 4 Euro per ton. Switchgrass appears to be the most attractive option, followed by Cardoon and Miscanthus. Arundo is never preferred. Relative to the previous agricultural policy setting of Agenda 2000, the biomass potential increases more for smaller farms and farms with a higher share of cotton, vegetables, or trees.Energy crops, Common Agricultural Policy, Climate mitigation Economics, Arundo, Miscanthus, Switchgrass, Cardoon, Mathematical programming, Dynamic cost minimization, Bioenergy potential, Biomass supply curve, Kopaida, Greece

Greenhouse Gas Emission Mitigation and Emission Intensities in Agriculture

Energy efficiency and greenhouse gas emissions are closely linked. This paper reviews agricultural options to reduce energy intensities and their impacts, discusses important accounting issues related to system boundaries, land scarcity, and measurement units, and compares agricultural energy intensities and improvement potentials on an international level. Agricultural development in the past decades, while increasing yields, led to lower average energy efficiencies between the sixties and mid eighties. In the last two decades, energy intensities in developed countries increased, however, with little impact on greenhouse gas emissions. Efficiency differences across countries suggest a maximum improvement potential of 500 million tons of CO2 annually.Energy intensity, Agriculture, Greenhouse gas emissions, Mitigation potential, Fertilizer efficiency

Implications of a Carbon-Based Energy Tax for U.S. Agriculture

Policies to mitigate greenhouse gas emissions are likely to increase energy prices. Higher energy prices raise farmer costs for diesel and other fuels, irrigation water, farm chemicals, and grain drying. Simultaneously, renewable energy options become more attractive to agricultural producers. We consider both of these impacts, estimating the economic and environmental consequences of higher energy prices on U.S. agriculture. To do this we employ a price-endogenous agricultural sector model and solve that model for a range of carbon-tax-based energy price changes. Our results show mostly positive impacts on net farm income in the intermediate run. Through market price adjustments, fossil fuel costs are largely passed on to consumers. Additional farm revenue arises from the production of biofuels when carbon taxes reach $30 per ton of carbon or more. Positive environmental benefits include not only greenhouse gas emission offsets but also reduced levels of nitrogen leaching.energy tax, greenhouse gas policy, U.S. agricultural sector, bioenergy, mathematical programming, Environmental Economics and Policy,