ESTIMATING THE VALUE OF SEQUENTIAL UPDATING SOLUTIONS FOR INTRAYEAR CROP MANAGEMENT

Results of comparing updating versus nonupdating modeling assumptions call into question the use of models based on nonupdating strategies as valid representations of actual farmer actions. If farmers are sequential updaters, the results indicate that models assuming no updating are inaccurate. The degree of this inaccuracy ranges between 4% and 10% of profits for the study area. Further, the results indicate that updating appears to be important for both descriptive and prescriptive studies of farmer behavior.Crop Production/Industries,

COMBINING ECONOMIC AND BIOLOGICAL DATA TO ESTIMATE THE IMPACT OF POLLUTION ON CROP PRODUCTION

Duality methods utilizing a profit function framework are employed to estimate the output elasticity of ambient ozone levels on cash grain farms in Illinois. While duality methods have been recommended as a cure to many of the statistical problems of direct estimation of production functions, multicollinearity may still be a problem. A method for utilizing stochastic information on parameters of a seemingly unrelated system of equations, which is implied by profit function estimation, is developed and applied to measuring the impact of ozone. Such an approach may be necessary in measuring other environmental effects because of a lack of regressor variability.Crop Production/Industries, Environmental Economics and Policy,

Machinery-Sharing Contractual Issues and Impacts on Cash Flows of Agribusinesses

Contractual arrangements for joint machinery ownership between independent agribusinesses are explored. A two-farm economic simulation model of locations in Texas, Colorado, and Montana is developed to provide insight associated with sharing combines. Important variables include combine size (efficiency), yield losses resulting from untimely access to equipment, the penalty structure for untimely delivery, and cost-sharing and depreciation deductions claimed between producers. Combine sharing is risk-reducing in most cases. The gains to both parties are lowest when harvesting periods overlap. While the value of sharing is positive under many scenarios, benefits from sharing are small relative to total farm revenue.combines, machinery sharing, risk, simulation, Agribusiness, Agricultural Finance,

Geographical Diversification: An Application of Copula Based CVaR

Risk and Uncertainty,

Geographical Diversification in Agriculture: An Applied Case to Western U.S. Wheat Growers

Yield correlations between 380 different counties are calculated for non-irrigated wheat. Using this data, a function is estimated that shows the relationship between correlation and changes in geographic and climate data. In addition movement variables are included added to the specification to capture the impact of moving from one production region to another. A negative relationship was found between changes in latitude, longitude, precipitation, elevation, and temperature. Correlations and longitude and precipitation showed downward sloping concave relationship, whereas correlations and latitude showed downward sloping convex relationships. Changes in latitude and longitude are found to have greatest impact on correlation with elasticities of -1.54 and -1.Yield Correlations, Geographical Diversification, Farm Management, Agribusiness, Crop Production/Industries, Farm Management, Risk and Uncertainty,

Resultater fra eksperimenter med fosfortilsetning til Nedre Lundetjenn, Aust-Agder 2006-2007

Eksperimentell fosfortilsetning til Nedre Lundetjenn i Grimstad kommune gjennom tre påfølgende vekstsesonger (1999-2001) førte til en dramatisk tilbakegang i forekomsten av krypsiv sammenlignet med en ubehandlet referanseinnsjø like oppstrøms. Gjødslingsforsøket ble gjentatt i 2006 og 2007 for å undersøke om en kunne repetere resultatene fra forrige gang. Selv om krypsivbestandene i Nedre Lundetjenn viste en reduksjon både i mengde og vitalitet i 2006-2007, fikk vi ikke samme dramatiske reduksjon som ved første gjødslingsperiode. Også eksperimentelle gjødslingsforsøk under kontrollerte laboratorieforhold har gitt motstridende resultater. Mangelen på entydige responser av fosfortilsetning i helsjø- og laboratorieforsøk illustrerer derfor at årsakene til variasjonene i krypsivets vekst fortsatt framstår som sammensatte og kompliserte. Problemvekst av krypsiv kan derfor trolig ikke relateres til én spesiell miljøfaktor, men snarere en kombinasjon av flere, samvirkende faktorer.Krypsivprosjektet på Sørlande

Ecosystem effects of thermal manipulation of a whole lake, Lake Breisjøen, southern Norway (THERMOS project)

International audienceWe conducted a 3-year artificial deepening of the thermocline in the dimictic Lake Breisjøen, southern Norway, by means of a large submerged propeller. An adjacent lake served as untreated reference. The manipulation increased thermocline depth from 6 to 20 m, caused a significant increase in the heat content, and delayed ice-on by about 20 days. There were only minor changes in water chemistry. Concentrations of sulphate declined, perhaps due to greater reduction of sulphate at the sediment-water interface. Concentrations of particulate carbon and nitrogen decreased, perhaps due to increased sedimentation velocity. Water transparency increased. There was no significant change in concentration of phosphorus, the growth-limiting nutrient. There were few significant changes in principal biological components. Phytoplankton biomass and productivity did not change, although the chlorophyll-a concentration showed a small decrease. Phytoplankton species richness increased, and the species composition shifted. Growth of periphyton increased. There was no change in the macrophyte community. The manipulation did not affect the zooplankton biodiversity, but caused a significant shift in the relative abundance (measured as biomass) in the two major copepod species. The manipulation did not affect the individual density, but appeared to have changed the vertical distribution of zoobenthos. Fish populations were not affected. The lake is oligotrophic and clearwater and the manipulation did not change the supply of phosphorus, and thus there were only minor changes in lake chemistry and biology. Effects might be larger in eutrophic and dystrophic lakes in which internal processes are stronger

Limnologiske undersøkelser i Breisjøen og Store Gryta, 1998/1999 - Bakgrunnsrapport Thermosprosjektet

Årsliste 2000Denne rapporten er en bakgrunnsrapport fra innsjøene Breisjøen og Store Gryta i Lillomarka, Oslo kommune. Rapporten inneholder informasjon om sentrale fysiske, kjemiske og biologiske forhold i innsjøene. Dette bakgrunnsmaterialet er viktig fordi termoklinen (sprangsjiktet) i den ene innsjøen (Breisjøen) skal brytes ved hjelp av en sakte-roterende propell f.o.m. våren 2001. Store Gryta, en nærliggende innsjø, vil fungere som kontrollsjø. Dette øker mulighetene for å skille naturlige variasjoner fra effekter av manipuleringen. Manipuleringen gjøres for å øke kunnskapen om de økologiske effekter av variasjoner i termoklindyp, en sentral problemstilling i lys av framtidige klimaendringer og effekter på våre innsjøer. Klima prognosene antyder høyere lufttemperaturer og sterkere vind. Dette er de viktigste faktorene for årsvariasjonene i termoklindyp i en innsjø. To år med bakgrunnsdata ligger til grunn for de fysisk, kjemiske og biologiske beskrivelsene og sammenlikningene av innsjøene. Sammendrag, både på norsk og engelsk, finnes først i rapporten, mens primærdata i stor grad finnes i rapportens vedlegg.Norsk institutt for vannforskning (NIVA) (Strategisk institutt program

Puntos de inflexión en los gradientes de composición de las comunidades de plantas acuáticas de diferentes continentes

Sección: SIBECOL-AIL Meeting in Aveiro-2022[EN] Unravelling patterns and mechanisms of biogeographical transitions is crucial if we are to understand compositional gradients at large spatial extents, but no studies have thus far examined breakpoints in community composition of freshwater plants across continents. Using a dataset of almost 500 observations of lake plant community composition from six continents, we examined, for the first time, if such breakpoints in geographical space exist for freshwater plants and how well a suite of ecological factors (including climatic and local environmental variables) can explain transitions in community composition from the subtropics to the poles. Our combination of multivariate regression tree (MRT) analysis and k-means partitioning suggests that the most abrupt breakpoint exists between temperate to boreal regions on the one hand and freshwater plant communities harbouring mainly subtropical or Mediterranean assemblages on the other. The spatially structured variation in current climatic conditions is the most likely candidate for controlling these latitudinal patterns, although one cannot rule out joint effects of eco-evolutionary constraints in the harsher high-latitude environments and post-glacial migration lags after Pleistocene Ice Ages. Overall, our study supports the foundations of global regionalisation for freshwater plants and anticipates further biogeographical research on freshwater plant communities once datasets have been harmonised for conducting large-scale spatial analyses[ES] Desentrañar los patrones y mecanismos que subyacen a las transiciones biogeográficas es un requisito fundamental a la hora de comprender los gradientes de composición de las comunidades ecológicas a grandes extensiones espaciales, si bien ningún estudio ha examinado explícitamente estos puntos de inflexión para comunidades de plantas acuáticas de diferentes continentes. Utilizando una completa base de datos que condensa un total de casi 500 observaciones individuales sobre las comunidades florísticas lacustres de seis continentes, este trabajo pretende delinear las transiciones biogeográficas en plantas acuáticas a escala global, así como valorar el papel que desempeñan diversos mecanismos ecológicos (a saber, las condiciones climáticas y las características locales del hábitat) sobre estos puntos de inflexión en el espacio geográfico comprendido entre las latitudes subtropicales y los polos. Nuestros resultados obtenidos mediante la ejecución simultánea de árboles de regresión multivariante (MRT) y algoritmos de agrupación por k-medias demuestran la existencia de un punto de inflexión entre las regiones templadas y boreales y los lagos localizados en las bandas subtropicales y en las inmediaciones del Mediterráneo. La estructura espacial que subyace a la distribución de los condicionantes climáticos en nuestro planeta parece ser el principal mecanismo de control de dichas transiciones biogeográficas, si bien estos patrones latitudinales también podrían explicarse en base a constricciones eco-evolutivas en las regiones más septentrionales y a la colonización diferencial de los territorios norteños antaño cubiertos por el hielo durante el Último Máximo Glacial. En síntesis, nuestro estudio proporciona una base teórica preliminar para futuras investigaciones encaminadas a delimitar las unidades geográficas de los principales componentes de la flora acuática contemporánea y también anticipa un creciente interés por los estudios de carácter fitogeográfico en las aguas continentales, si bien los análisis venideros deberán prestar especial atención a la armonización de datos biológicos potencialmente heterogéneos en naturaleza y con orígenes disparesSIJGG was funded by the European Union Next Generation EU/PRTR (grant no. AG325). Academy of Finland supported JH, JGG (grant no. 331957), and JA (grant no. 322652). CFL appreciates financial support from the Spanish Ministry of Science and Technology (grant no. CL2017- 84176R). BAL was supported by National Research, Development, and Innovation Office (grant no. NKFIH, OTKA FK127939) and by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences. SK was supportedby NWO Vidi (grant no. 203098). LR was funded by MESRSI (Ministry of Higher Education, Scientific Research and Innovation of Morocco) as part of the BiodivRestore Program (RESPOND Project) and by the Tour du Valat Foundation. Sampling of the Brazilian coastal lakes was financed by NWO (grant no. W84-549), the National Geographic Society (grant no. 7864-5), and CNPq (grants no. 480122, 490409, 311427