ECONOMICS OF AGRICULTURAL SOIL CARBON SEQUESTRATION IN THE NORTHERN GREAT PLAINS

Under the Kyoto protocol of the United Nations Framework Convention on Climate Change the United States is charged with reducing emissions of greenhouse gases to seven percent below their 1990 levels by the period 2008-2012. These reductions could be met from many industries including agriculture. In this paper, an economic simulation model is linked to the CENTURY ecosystem model to quantify the economic efficiency of policies that might be used to sequester carbon (C) in agricultural soils in the Northern Great Plains region. Model outputs are combined to assess the costs of inducing changes in equilibrium levels of soil C through three types of policies. The first is a CRP-style policy that provides producers with per-acre payments for converting crop-land to permanent grass; the second is a policy that provides per-acre payments to all farmers that use continuous cropping, regardless of the land's cropping history; the third is a policy that provides per-acre payments for the use of continuous cropping only on land units that had previously been in a crop/fallow rotation. The analysis shows that a CRP-style policy is found to be an inefficient means to increase soil C resulting in costs that typically exceed $100 per MT (metric ton) of C. In contrast, payments to adopt continuous cropping were found to produce increases in soil C for between$5 to $70/MT depending on the geographic area and degree of targeting of the payments. The most efficient, lowest cost policy is achieved when payments are targeted to land that was previously in a crop/fallow rotation. In this range, soil C sequestration appears to be competitive with C sequestered from other sources.policy design, economic efficiency, soil carbon, sequestration, valuing soil carbon, Great Plains agriculture, Environmental Economics and Policy, Q2,

ECONOMICS OF AGRICULTURAL SOIL CARBON SEQUESTRATION IN THE NORTHERN PLAINS

Under the Kyoto protocol of the United Nations Framework Convention on Climate Change the United States is charged with reducing emissions of greenhouse gases to seven percent below their 1990 levels by the period 2008-2012. These reductions could be met from many industries including agriculture. In this paper, an economic simulation model is linked to an ecosystem model to quantify the economic efficiency of policies that might be used to sequester carbon (C) in agricultural soils in the Northern Plains region. Simulations with the Century ecosystem model show that long-term soil C levels associated with a crop/fallow system are less than those for grass alone, but that soil C levels for grass-clover-pasture are greater than for continuously cropped grains. The analysis shows that a CRP-style policy is found to be an inefficient means to increase soil C because the per acre payments to convert crop-land to grass-only draw land from both the crop/fallow system and the continuous cropping system, and costs typically exceed $100 per MT (metric ton) of C. In contrast, payments to adopt continuous cropping were found to produce increases in soil C for between$5 to $70 depending on area and degree of targeting of the payments. The most efficient, lowest cost policy is achieved when payments are targeted to land that was previously in a crop/fallow rotation. In this range, soil C sequestration appears to be competitive with C sequestered from other sources.policy design, economic efficiency, soil carbon, sequestration, valuing soil carbon, Great Plains agriculture, Resource /Energy Economics and Policy, Q2,

Modelling nitrous oxide emissions from mown-grass and grain-cropping systems : Testing and sensitivity analysis of DailyDayCent using high frequency measurements

The lead author, Nimai Senapati (Post doc), was funded by the European community’s Seventh Framework programme (FP2012-2015) under grant agreement no. 262060 (ExpeER). The research leading to these results has received funding principally from the ANR (ANR-11-INBS-0001), AllEnvi, CNRS-INSU. We would like to thank the National Research Infrastructure ‘Agro-écosystèmes, Cycles Biogéochimique et Biodiversité (SOERE-ACBB http://www.soere-acbb.com/fr/) for their support in field experiment. We are deeply indebted to Christophe deBerranger, Xavier Charrier for their substantial technical assistance and Patricia Laville for her valuables suggestion regarding N2O flux estimation.Peer reviewedPostprin

Mid-infrared spectroscopy and enzyme activity temperature sensitivities as experimental proxies to reduce parameter uncertainty of soil carbon models

Models that simulate the dynamics of soil organic carbon (SOC) are crucial to understand the global carbon cycle, but current generation models are subject to major uncertainties due to two model shortcomings. Firstly, their different carbon pools are not connected to measurable SOC fractions. Secondly, there is uncertainty about the response of the different carbon pools to an increasing temperature. The aim of this thesis was thus to link the SOC model pools of the Daisy model to measurable proxies for SOC quality and pool specific temperature sensitivity. In the first study, the drying temperature for soil samples assessed by diffuse reflectance mid infrared Fourier transform spectroscopy (DRIFTS) was optimized to assure optimal representativeness of aliphatic and aromatic-carboxylate absorption bands as proxies for fast- and slow-cycling SOC pools. Their ratio was termed the DRIFTS stability index (DSI). In the second study, the DSI was used to distinguish fast- and slow-cycling SOC model pools at model initialization. In the third study, model initialization using DSI was performed to infer pool specific temperature sensitivities for the different Daisy carbon pools. Furthermore, it was tested whether the measured temperature sensitivities of different extracellular soil enzymes could be used as proxies for pool specific temperature sensitivity. Using a global collection of soil samples revealed that the absorption of all studied DRIFTS absorption bands increased significantly (p < 0.0001) with increasing drying temperature from 32°C to 105°C. This effect was disproportionally strong for the aliphatic absorption band. Due to the strong interference of the residual soil sample moisture content with the aliphatic absorption band, drying at 105°C and storage in a desiccator prior to measurement would be necessary for representative spectra for model pool initialization. In the following, a combination of medium to long-term bare fallow experiments was used, to test the utility of the DSI for SOC pool initialization. Pool partitioning by the DSI was superior to using a fixed pool partitioning under the assumption that SOC was at steady state. The DSI contained robust information on SOC quality across sites. Therefore, in the majority of cases, the application of the DSI led to significantly lower model errors than the steady state assumption. Furthermore, the application of the DSI in Bayesian calibration led to a reduced parameter uncertainty for the turnover of the slow-cycling SOC pool and the humification efficiency. The 95% credibility interval of the slow-cycling SOM pools half-life between 278 and 1095 years suggested faster SOC turnover than earlier studies. The DSI used for SOC model pool initialization was then combined with the lignin-to-nitrogen ratio for litter pool initialization to infer pool specific temperature sensitivities. The simulations of five field studies and laboratory incubations with fallow soil and crop-litter inputs were combined. Based on a clear pool definition, pool specific temperature sensitivities could be inferred by Bayesian calibration. However, differences in temperature sensitivities of the same pools between experiments suggested that carbon stability was not the main driver of temperature sensitivities. Instead, the main difference was found between the laboratory incubations (higher Q10 values up to 3) and the field (lower Q10 values centered around 2). In a second approach, the measured Q10 value of phenoloxidase (1.35) was used as Q10 value of the temperature function of both SOM pools and the slow crop-litter pool while ß glucosidase (1.82) was used for the fast crop litter pool. This improved field simulations by 3 to 10% compared to assuming a standard Q10 of 2 for all pools. Thus, site specific Q10 of different soil enzymes showed potential as proxy for site and pool specific temperature sensitivities. Important state variables that explain the observed Q10 value differences between experiments were identified as physical protection of SOC, substrate availability and environmental stress for microorganisms due to fluctuating state variables in the field. In conclusion, the usefulness of the DSI as an indicator of SOC stability and proxy for pool initialization was demonstrated for several soils in central Europe. In addition, it was shown that pool partitioning proxies can help to infer pool specific temperature sensitivity by Bayesian calibration. However, temperature sensitivity was not mainly a function of carbon stability.Modelle, welche die Flüsse des organischen Bodenkohlenstoffes (OBK) simulieren, sind zum Verständnis des globalen Kohlenstoffkreislaufs entscheidend. Modelle der heutigen Generation haben wegen zwei Hauptschwächen große Unsicherheiten. Zum einen sind die unterschiedlichen Kohlenstoffpools nicht mit messbaren OBK Fraktionen verknüpft. Zum anderen besteht Unsicherheit darüber, wie die verschiedenen Kohlenstoffpools auf steigende Temperaturen reagieren. Das Ziel dieser Arbeit war es deshalb, die OBK Pools des Daisy Modelles mit messbaren Proxies für Kohlenstoffqualität und poolspezifischen Temperatursensitivitäten zu verknüpfen. In der ersten Studie wurde die Vorbehandlung von Bodenproben zur Messung mit diffuser Reflexions-Fourier-Transformations-Infrarotspektroskopie (DRIFTS) optimiert. Die Trocknungstemperatur der Vorbehandlung wurde angepasst, um die Repräsentativität von aliphatischen sowie aromatisch-carboxylischen Absorptionsbändern zu verbessern. Diese Bänder wurden respektive als Proxies für sich schnell und langsam umsetzende OBK Pools, verwendet. Ihr Verhältnis wurde als DRIFTS Stabilitätsindex (DSI) bezeichnet. In der zweiten Studie wurde der DSI genutzt, um sich schnell und langsam umsetzende OBK Modellpools bei der Modellinitialisierung zu unterteilen. In der dritten Studie wurde die entwickelte Modellinitialisierung mittels des DSI eingesetzt, um poolspezifische Temperatursensitivitäten für unterschiedliche Daisy Kohlenstoffpools abzuleiten. Zusätzlich wurden gemessene Temperatursensitivitäten unterschiedlicher extrazellulärer Bodenenzyme als Proxies für poolspezifische Temperatursensitivitäten getestet. Unter Verwendung einer globalen Sammlung von Bodenproben wurde festgestellt, dass die Absorption der untersuchten DRIFTS Absorptionsbänder mit der Trocknungstemperatur zwischen 32°C und 105°C signifikant zunahm (p < 0.0001). Wegen starker Interferenz der Restfeuchte von Bodenproben mit dem aliphatischen Absorptionsband ist daher die Trocknung bei 105°C und die Aufbewahrung im Exsikkator notwendig, um repräsentative Spektren für die Modellinitialisierung zu messen. Im Folgenden wurde eine Kombination aus Mittel- bis Langzeitversuchen mit Bodenbrache verwendet, um den DSI für die OBK Poolinitialisierung zu testen. Der DSI war einer fixen Poolaufteilung, unter der Annahme eines Gleichgewichtszustandes des OBK, überlegen. Der DSI enthielt über mehrere Standorte hinweg belastbare Informationen zur OBK Qualität und seine Anwendung führte in der Mehrzahl der Fälle zu einem signifikant niedrigeren Modellfehler als die Annahme eines Gleichgewichtszustandes der OBK. In der Bayesschen Kalibrierung führte der DSI zu einer reduzierten Parameterunsicherheit für die Umsatzrate des sich langsam umsetzenden OBK Pools sowie der Humifizierungseffizienz. Das 95% Glaubwürdigkeitsintervall der Halbwertszeit des sich langsam umsetzenden OBK Pools betrug 278 bis 1095 Jahre. Im Anschluss daran wurde die Verwendung des DSI für OBK Poolinitialisierung mit der Verwendung des Lignin-zu-Stickstoff Verhältnisses für die Poolinitialisierung der Pflanzenstreu-Pools kombiniert, um nachfolgend Pool spezifische Temperatursensitivitäten abzuleiten. Es wurden fünf Versuche, bestehend aus Feldstudien und Laborinkubationen mit Brachflächen sowie Streueinarbeitung, kombiniert. Dabei konnten poolspezifische Temperatursensitivitäten durch Bayessche Kalibrierung abgeleitet werden. Wegen unterschiedlicher Temperatursensitivitäten derselben Pools in verschiedenen Experimenten war die Kohlenstoffstabilität jedoch nicht die Hauptursache der beobachteten Temperatursensitivitäten. Der Hauptunterschied bestand zwischen Laborinkubationen (höhere Q10 Werte bis zu 3) und Feldversuchen (niedrigere Q10 Werte um 2). In einem zweiten Ansatz wurden gemessene Q10 Werte der Phenoloxidase (1.35) als Q10 Wert der der beiden OBK-Pools und des langsamen Pflanzenstreu-Pools, und ß-Glucosidase (1.82) für den schnellen Pflanzenstreu-Pool verwendet. Dies verbesserte die Simulationen der Feldversuche um 3 bis 10% im Vergleich zum Standard-Q10 von 2 für alle Pools. Standortspezifische Q10 Werte verschiedener Bodenenzyme bewiesen somit Potenzial als Proxies für standort- und poolspezifische Temperatursensitivitäten. Als wichtige Zustandsvariablen zur Erklärung der beobachteten Q10 Wert-Unterschiede zwischen Experimenten wurden physikalischer Schutz von OBK, Substratverfügbarkeit und Umweltstress für Mikroorganismen infolge sich ständig ändernder Zustandsvariablen im Feld identifiziert. Zusammenfassend konnte in dieser Arbeit der Mehrwert des DSI als Indikator der OBK Stabilität und als Proxy für die Poolinitialisierung für eine Reihe von Böden in Mitteleuropa demonstriert werden. Darüber hinaus konnte gezeigt werden, dass Poolpartitionierungs-Proxies helfen können, die poolspezifische Temperatursensitivität durch Bayessche Kalibrierung abzuleiten. Die Temperatursensitivität konnte jedoch nicht primär durch die Kohlenstoffstabilität erklärt werden

THE KYOTO PROTOCOL: ECONOMIC EFFECTS OF ENERGY PRICES ON NORTHERN PLAINS DRYLAND GRAIN PRODUCTION

This study examined possible economic impacts on Northern Plains grain producers of policies that could be undertaken by the United States to comply with the Kyoto Protocol. The paper begins with a discussion of the potential effects of the Kyoto Protocol on prices of energy and inputs used in agricultural production. The next section describes the data and econometric models that were used to develop a field-scale, stochastic simulation model of the crop production system typical of the Northern Plains. This model is based on econometric production models estimated with a spatially referenced, statistically representative sample of farmers in Montana. The simulation analysis shows that the impacts of higher energy prices would tend to discourage the use of fallow, raise variable costs of production by 3 to 13%, and reduce net returns above variable cost by 6 to 18% in the case of spring wheat grown on fallow, Under the higher cost scenarios assumed in an analysis conducted by the Farm Bureau, production costs for spring wheat on fallow would increase by 15 to 27% and net returns would decline by 15 to 24%.Resource /Energy Economics and Policy,

Dynamics of carbon dioxide, methane and nitrous oxide fluxes in planted shelterbelts and adjacent cropped fields

For more than a century, over 600 million shelterbelt trees have been distributed to land owners in the Canadian Prairies mainly to protect farms from soil erosion and extreme wind events. In Saskatchewan, there exists over 60,000 km of planted shelterbelts; however, there is a lack of data quantifying the role of shelterbelts in mitigating greenhouse gas (GHG) emissions in agricultural landscapes. These limited estimates of carbon (C) sequestration and GHG mitigation potential for shelterbelts are needed for regional C budgets and GHG inventories. The objective of this research was to quantify the role of shelterbelts on the mitigation of CO2, CH4 and N2O in cultivated fields. Chamber-based GHG monitoring and modeling approaches were employed. Nitrous oxide emissions were lower in shelterbelts (0.65 kg N2O-N ha-1 yr-1) than in cultivated soils (2.5 kg N2O-N ha-1 yr-1), attributed to the capability of deep rooting trees to remove excess available N and soil water. Both shelterbelt and cultivated soils were small sinks for CH4, though the sink potential was 3.5-times greater for the shelterbelt soils. Soil-derived CO2 emissions were greater in the shelterbelts (4.1 Mg CO2-C ha-1 yr-1) than in the adjacent fields (2.1 Mg CO2-C ha-1 yr-1). Nevertheless, cumulative emissions of non-CO2 GHGs was reduced by 0.55 Mg CO2e ha-1 yr-1 in the shelterbelts and soil C storage (0–30 cm soil depth) was 27% greater, representing an increase of 28 Mg ha-1 in the shelterbelts than in the cropped fields, attributed to long-term inputs from tree litter. Holos model simulations of GHG fluxes in a cereal-pulse rotation indicated that a shelterbelt planting occupying 5% of the farmland resulted in total farm emissions being reduced by 8.2 – 23% during a 60-year period, depending on selected tree species. Between 90 – 95% of GHG mitigation by shelterbelts was through C sequestration in tree biomass and in stable SOC pools, while the reduction in N2O emissions and increased oxidation of soil CH4 totalled 5.1 – 9.8% of the overall GHG mitigation by shelterbelts. Faster growing trees (e.g. hybrid poplar) were more effective in accumulating C in tree biomass and soil and in mitigating soil GHG emissions. This study provides evidence that farm shelterbelts function as net biological sinks of CO2 and can play a role in mitigating soil-derived GHG emissions in agricultural landscapes

ECONOMETRIC-PROCESS MODELS FOR INTEGRATED ASSESSMENT OF AGRICULTURAL PRODUCTION SYSTEMS

This paper develops the conceptual and empirical basis for a class of empirical economic production models that can be linked to site-specific bio-physical models for use in integrated assessment research. Site-specific data are used to estimate econometric production models, and these data and models are then incorporated into a simulation model that represents the decision making process of the farmer as a sequence of discrete or continuous land use and input use decisions. This discrete/continuous structure of the econometric process model is able to simulate decision making both within and outside the range of observed data in a way that is consistent with economic theory and with site-specific bio-physical constraints and processes. An econometric-process model of the dryland grain production system of the Northern Plains demonstrates the capabilities of this type of model.bio-physical models, integrated assessment, production models, dryland grain production, econometric-process models, Production Economics, C5, Q1, Q2,

Land-use type and slope position effects on soil respiration in black locust plantations in Artvin, Turkey

In this study, influences of aspect, land-use type, and sampling time on soil respiration were investigated in black locust plantation and adjacent grassland sites in Murgul-Artvin, Turkey. Both sites were heavily affected from acid rain produced by a nearby copper smelter. Soil respiration was measured approximately monthly in three sampling plots in each sites from January 2005 to November 2005 using the soda-lime technique. Mean daily soil respiration ranged from 0.22 to 2.37 g C m-2 d-1. Mean soil respiration in black locust plantations and grassland sites were 0.74 and 1.03 g C m-2 d-1, respectively. Soil respiration was significantly higher in grassland sites than in black locust plantation sites. Seasonal changes in soil respiration were related to soil moisture and temperature changes. Mean annual soil respiration rate correlated positively with surface soil (0-15 cm) sand (P < 0.05) and organic matter content (P < 0.1), and correlated negatively with mean surface soil clay and silt contents (P < 0.1). Overall, our results indicate that grassland sites have higher soil biological activity compared to black locust plantation sites