Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2006
Forfattere
Marie Alexis Cornelia Rumpel Patrick Louchouarn Nicolas Péchot Daniel Rasse André MariottiSammendrag
Fire is the main disturbance for terrestrial ecosystems, with a strong effect on biogeochemical cycles. Especially, part of the ecosystem organic matter (OM) is chemically modified by temperature elevation. Depending on fire severity, a big variety of chemical structures is produced ranging from slightly altered OM to strongly condensated structures. The fate of these pyrogenic OM when added to soil is unclear. Highly aromatic black carbon (BC) may be the most stable part of the continuum. At molecular level, levoglucosan is the main fire product of cellulose alteration. These two compounds have been separately used as tracers of plant biomass burning in aerosols, soils and sediments. Their combined use may provide closer insight into conditions and OM transformations that occurred during the fire. We aimed at quantifying BC and levoglucosan in plant residues after fire. Their production rates were compared to improve the understanding of their relative contribution to soil OM. Litter leaves were collected after a prescribed burning. The >2mm fraction was visually separated into charred (black, shiny) and unburned (brown) particles. BC was quantified by chemical oxidation (K2Cr2O7/H2SO4) and elemental analyses. Levoglucosan was identified and quantified by GC/MS analysis of the total lipid extract. Unburned post-fire leaves contain more levoglucosan than charred leaves, showing that a chemical alteration occurred despite no visual evidence. Moreover BC and levoglucosan concentrations are negatively correlated. This is consistent with their expected production temperatures: levoglucosan may be destroyed at temperature BC is produced. Relative quantity of theses compounds may then provide information about fire severity. However while BC is expected to be stable in soil, levoglucosan may suffer from degradation processes. Consequently, for historical reconstitution their respective fates in soil degrading conditions have to be considered.
Forfattere
Ingrid Holtsmark Dimitris Mantzilas Vincent Eijsink May Bente BrurbergSammendrag
Members of the actinomycete genus Clavibacter are known to produce antimicrobial compounds, but so far none of these compounds has been purified and characterized. We have isolated an antimicrobial peptide, michiganin A, from the tomato pathogen Clavibacter michiganensis subsp. michiganensis, using ammonium sulfate precipitation followed by cation-exchange and reversed-phase chromatography steps. Upon chemical derivatization of putative dehydrated amino acids and lanthionine bridges by alkaline ethanethiol, Edman degradation yielded sequence information that proved to be sufficient for cloning of the gene by a genome-walking strategy. The mature unmodified peptide consists of 21 amino acids, SSSGWLCTLTIECGTIICACR. All of the threonine residues undergo dehydration, and three of them interact with cysteines via thioether bonds to form methyllanthionine bridges. Michiganin A resembles actagardine, a type B lantibiotic with a known three-dimensional structure, produced by Actinoplanes liguriae, which is a filamentous actinomycete. The DNA sequence of the gene showed that the michiganin A precursor contains an unusual putative signal peptide with no similarity to well-known secretion signals and only very limited similarity to the (only two) available leader peptides of other type B lantibiotics. Michiganin A inhibits the growth of Clavibacter michiganensis subsp. sepedonicus, the causal agent of ring rot of potatoes, with MICs in the low nanomolar range. Thus, michiganin A may have some potential in biological control of potato ring rot.
Forfattere
Hugh RileySammendrag
Resultater for 1998-2004 er rapportert fra fire langvarige (25-28 år) jordarbeidingsforsøk, der konvensjonell høstpløying er sammenlignet med redusert jordarbeiding, som regel grunn harving bare om våren. Results for 1998-2004 are reported from four long-term (25-28 years) tillage trials, comparing conventional autumn ploughing with reduced tillage, normally spring harrowing only. Plant residues were retained during the period studied. The weather was somewhat wetter than the 1961-1990 normal. Results with reduced tillage were mostly similar to those seen in earlier trial periods. In Trial 1, mean grain yield was 95% with spring harrowing only versus autumn ploughing, 96% when harrowing in autumn was performed as well and 97% when the soil was ploughed every third year. In Trial 2 positive crop rotation effects were found both with and without ploughing, and reduced tillage gave 5% lower grain yield in this trial also. In Trial 3, tillage system did not affect yields of cereals grown in rotation with potatoes, but reduced tillage gave 12% lower potato yield than ploughing. Little difference in response to N fertilizer was found. In Trial 4, reduced tillage on large-scale (0.7 ha) plots gave 11% lower grain yields than annual ploughing, partly due to shallow sowing depth. No long-term trend in the yield responses to tillage was discernible in any trial, and between-year variability was similar with both ploughing and reduced tillage. Percentage yields with reduced tillage relative to annual ploughing correlated positively with rainfall in May and with mean air temperature in August. It is concluded that the reduced tillage systems studied are sustainable in terms of productivity, relative to labour, machinery and energy inputs. Likely benefits of such systems include higher levels of organic matter and aggregate stability in surface soil horizons, but a disadvantage is the need for frequent herbicide use to control perennial weeds.
Forfattere
Tor Håkon SivertsenSammendrag
An interpretation of the scientific principle ( as this is used in the context of agro meteorology ) is presented and discussed, containing the concepts of classification of meteorological and biological phenomena, parameterization, testing and use of models. The ideas of pure and applied science are presented, and then the concept of scope of the scientific principle is discussed. Both the use of science for understanding nature, the use of science for implementing applications, and the use of science for understanding the consequences of the use of applications are contained in this discussion. The views and discussion are also extended towards society, and what should be the content of sustainable agricultural production. The concept of the relations of human beings to othe biological organisms and to past and future generations is a part of this discussion. References: Philip, J.R, (1991), Soils, natural science, and models, Soil science. 151:91-98 Addiscott, T.M., (1993), Simulation modelling and soil behaviour, Geoderma, 60: 15-40 Sivertsen, T.H.,(2004) Invitation to Conceptual Discussions Concerning the Scope of the Scientific Method and Classification of Meteorological Phenomena and Meteorological Parameters, P 185-190, Selected Papers of the International Conference `Fluxes and Structures in Fluids", St. Petersburg, Russia, June 23-26, 2003, Moscow, IPM RAS, 2004 Sivertsen T.H., 2005, Discussing the scientific method and a documentation systems of meteorological and biological parameters, Physics and Chemistry of the Earth Special Issue: Agrometeorology 2003, Vol 30/1-3 pp 35-43 Sivertsen, T.H., 2005, Discussing scientific methods and the quality of meteorological data, in `Use and Availability of Meteorological Information from Different Sources as Input in Agrometeorological Models", COST ACTIONS 718 `Meteorological Applications for Agriculture", Edited by G. Maracchi, A. Mestre, L. Toulios and B. Gozzini. Sivertsen, T.H, 2005, ", Reflections on the Theme of Classifying, Documenting and Exchanging Meteorological Data", Atmospheric Science Letters, Vol.6 , Issue 3, p 171-175, John Wiley & Sons
Forfattere
Christian UhligSammendrag
Beitende pattedyr kan ha stor innvirkning på jordsmonnets fertilitet gjennom tilføring av avføring og tråkk. For arktiske herbivorer som reinsdyr har det hittil vært antatt at de øker beitenes fertilitet. Resultater fra nyere undersøkelse viser derimot at dette ikke er tilfelle for beitene på Finnmarksvidda, hvor det ble påvist at reinbeite kan føre til jordforringelse. Hovedmålet med denne presentasjonen er å finne en forklaring på de åpenbart motsigende påstandene ved å sammenstille resultatene om herbivorenes innflytelse på beitenes fertilitet. Resultatene viser at herbivorer kan påvirke beitenes kvalitet på alle tenkbare måter: positiv, negativ og ikke målbart. Generelt viser det seg at økosystemets respons på beiting er avhengig av dets evne til å nyttiggjøre seg avføringens næringsstoffer, og dermed dens betydning på systemets primær- produksjon og næringssyklus. På steder hvor beiting øker den langsiktige næringssyklusen vil dette føre til økt fertilitet og dermed økt beitekvalitet. Det motsatte kan derimot forventes på steder hvor beiting minker næringssyklusen. Ved å overføre dette konseptet til de lavdominerte vinterbeitene på Finnmarksvidda ble følgende funnet. De lett bio-tilgjengelige næringsstoffene fra reinens avføring ble tilført systemet i en periode med forholdsvis lav biologisk aktivitet som dermed har liten evne til å fiksere dem. I tillegg havner reinens urin og møkk ofte i snøen eller på frossen mark, og blir dermed ikke umiddelbart tilført jordmonnets næringspool. Den sesongbestemte utsatte tidsforskjell mellom reinens tilgjengeliggjøring av essensielle næringsstoffer om vinteren og deres biologiske assimilasjon øker risikoen for tap av disse, spesielt under snøsmeltings perioder om våren. Samtidig bestemmes økosystemets fysiske evne til å holde på næringsstoffene av dets kationbyttekapasitet (KAK). På de lavdominerte beitene på Finnmarksvidda er det humus og reinlav som utgjør det meste av systemets KAK, og begge blir negativ påvirket av reinbeite. Jordforringelsen på Finnmarksvidda kan dermed, i hvert fall delvis, forklares gjennom en ukomplett næringssyklus som resultat av både beitetidspunkt og en i utgangspunktet lav jordfertilitet. Reinbeite, spesielt om vinteren, øker dermed ikke nødvendigvis beitenes kvalitet.
Forfattere
Tor Gunnar VågenSammendrag
Madagascar is often portrayed as a global environmental hotspot with widespread deforestation and environmental degradation. Quantitative and spatially explicit data on ecological change are, however, scarce and current estimates are often based on simplistic representations of deforestation and land use change. Significant uncertainties in current estimates therefore remain. The present study was conducted to assess deforestation and other important complex land use change trajectories in the eastern highlands of Madagascar. A timeseries of satellite imagery dating from 1972 to 2001 was used to analyse overall change and rates of change between different land use types in the study area. Forest cover in the study area was approximately 8060 ha in 1972 and 4278 ha in 2001. Rates of deforestation were not, however, constant throughout this period, but varied from 52 ha yr1 (1972"1992) and 341 ha yr1 (1992"1999). The increased rates in the 1990s were attributed to turbulent political conditions on the island during the latter period and shows the complex relationships between social, political and ecological processes governing deforestation and land use change processes. Accessibility (distance to villages and roads) and elevation were shown to be the most important predictors of deforestation risk in the study area. Intensive cultivation of slopes (tanety) increased by about 3400 ha ( 65%) during the study period, a significant part of which came from cultivation of grassland savanna (net increase 1700 ha). These trends were found to be indicative of increasing pressure on available land resources in the region, leading to extensive cultivation of marginal grasslands and ultimately significant soil fertility decline.
Forfattere
Tor Gunnar Vågen Keith D. Shepherd Markus G. WalshSammendrag
Sensing landscape level change in soil fertility following deforestation and conversion in the highlands of Madagascar using Vis-NIR spectroscopy. Research data on soil quality are scarce in Madagascar, despite the island"s widely recognized problems of soil and environmental degradation. One of the major constraints to properly assessing current status, trends and processes of soil degradation is the high level of costs involved when using conventional soil analytical methods. Previous studies have demonstrated that visible-near-infrared (Vis-NIR) reflectance spectroscopy may permit rapid and cost effective analysis of tropical soils that could provide new opportunities for farmers, land managers, local authorities and researchers in assessing and managing soil quality. This study tested the potential of Vis-NIR soil spectral libraries for predicting and mapping soil properties in the eastern highlands of Madagascar. Stable calibration models were developed for several key soil properties. Cross-validated r2 values were soil organic carbon (SOC), 0.94; total nitrogen (TN), 0.96; and cation exchange capacity (CEC), 0.80. A spectral soil fertility index (SFI) was developed based on ten commonly used agronomic indicators of soil fertility. SFI varied significantly with current and historic land use. The index was successfully calibrated to both soil reflectance measured in the laboratory ( p =0.003) and Landsat TM reflectance ( p =0.003), which permitted mapping of the index.
Sammendrag
Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing concllusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability.
Forfattere
Kinga Adam Anne Kristine Søvik Tore KrogstadSammendrag
Sorption of P to the filter material Filtralite-PTM was examined at a small, medium and large scale. In the small and meso-scale laboratory models, the sorbed amount of total phosphorus (P) was heterogeneously distributed with more P sorbed in the inlet zone and the bottom layers. The full scale system had, on the other hand, the highest sorbed concentration in the outlet region. The overall P sorption capacity of the material was 8030, 4990 and 521 mg P kg-1 Filtralite-PTM for Box 1, Box 2 and meso scale respectively. This equals 4.42, 2.75 and 0.29 kg P m-3 material, respectively. However the maximum sorption capacities found were 2500, 3887 and 4500 mg P kg-1 Filtralite-PTM for the two small scale box systems the meso scale container, respectively. In the full scale system the overall P sorption capacity of the material was 52 mg P kg-1 Filtralite-PTM (0.029 kg P m-3 Filtralite-PTM) with a maximum sorbed amount of P of 249 mg P kg-1. Results from both the small and meso scale system show that when a CW is saturated, i.e. when the outlet concentration has reached its maximum allowed concentration of 1.0 mg P l-1, only parts of the filter material will have reached the sorption capacity. Sequential extractions of Filtralite-PTM showed that the loosely bound P, Ca-P and Al-P were the primary P sorption pools both in the small scale models and in the full scale constructed wetland (CW). However, the proportion of these 3 fractions varied with time and change in pH. A white product precipitated in the outlet zone of both the small scale box models as well as the onsite CW. The surface of these precipitation particles was identified by X-ray diffraction and SEM method as CaCO3 and precipitated Ca- and Mg-phosphates.
Sammendrag
The strategy to mitigate phosphorus (P) losses in areas of arable cropping in Norway has focused on measures to reduce erosion. Risk assessment of erosion has formed the basis for implementation of measures. The soil P content has increased during the last decades motivating an evaluation of its effect on P transfer in the landscape. The present study describes the spatial variability of runoff P concentrations from an agricultural dominated catchment (4.5 km2) representative for agriculture in south-eastern Norway. The concentrations of suspended sediments (SS), total P (TP) and dissolved reactive P (DRP) in runoff from 22 subcatchments (0.3 "263 ha) during one year (monthly and during runoff-events) were evaluated. Contributions from point sources were 38 kg TP yr-1 compared to a total P loss of 685 kg yr-1 from the whole catchment. During low flow, mean diffuse TP concentration in runoff from subcatchments varied from 28 to 382 µg L-1. The mean low flow TP concentration was 39 µg L-1 from the housing area (only diffuse runoff) and 33 µg L-1 from the forested area. During high flow the highest diffuse TP concentration was measured in an area with high erosion risk and high soil P status. At the subcatchment level the transfer of SS varied from 25 to 175% of the whole catchment SS transfer. Correspondingly for TP, the transfer varied from 50 to 260% of the whole catchment TP transfer. For each of five agricultural subcatchments the slope of the relationship between TP and SS concentrations reflected the mean soil P status of the subcatchment. Erosion risk estimates were closely related to the SS concentration (R2 = 0.83). The study illustrates that soil P status in addition to soil erosion are important factors for P transfer.