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.
2007
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Stig Morten Thorsen Lars Egil HaugenSammendrag
In the process of studying how climatic changes will influence important forage crops at high latitudes, van Oijen et al. (2005) developed a plant model for two grass species, timothy (Phleum pratense L.) and perennial ryegrass (Lolium perenne L.). In order to study winter survival of the plants, the plant model requires routines to simulate winter conditions, such as snow accumulation, soil frost, ice cover and soil temperature. This report describes the development of the SnowFrost model that simulates snow accumulation and the formation of soil frost. Routines for simulating ice encasement will be added at a later stage. The SnowFrost model implements a degree-day-temperatureindex method in the snowmelt routines, and an energy balance approach to get an algebraic expression for soil frost formation. Our main focus when developing the winter model is to adequately simulate winter conditions from the plant's point of view, rather than accurately simulate the depths of snow cover and soil frost penetration. Simulations for a site with cold and stable winter conditions show promising results, and indicate that SnowFrost is suitable as a foundation for the continuing work of developing the winter routines for the plant model.
Forfattere
Tor J. JohansenSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor J. JohansenSammendrag
Studies have focused on the progress of diapause and post-diapause development in one early- and one late-emerging population of D. floralis at various temperatures. For the early emerging biotype, diapause progressed gradually at low temperatures and terminated in late spring. For the late emerging biotype also, diapause progressed gradually for a certain period, but did not end, no matter the duration of chilling. For both populations, diapause developed faster at constant 18 ºC compared to combinations with chilling periods, implicating that chilling was not a prerequisite for diapause development. For the late emerging population, results indicated a second phase of diapause development with a threshold temperature of about 7 "C. However, the rate of this second phase development did not increase linearly with temperatures but had an optimum at about 12 "C. Post-diapause development for both populations was similar and had a lower threshold of about 2 "C. Results explain how delayed emergence in some populations are regulated.
Sammendrag
Histological properties of the graft union between a rootstock and scion may provide a mechanistic explanation why dwarfing rootstocks are able to reduce the growth of the tree. In order to investigate the relationship between growth and the amount of functional xylem tissue of potted sweet cherry trees, an experiment was conducted during 2002-2003. One year old field budded and bench grafted (from greenhouse) sweet cherry trees of the cultivars Van, Ulster and Lapins in all combinations of the three rootstocks Prunus avium seedling, Colt and Gisela 5 were grown in pots for two growing seasons. After shoot extension had terminated when trees were in full leaf the second year, the total growth of the different parts of the trees and the functional area using safranin staining were measured. The total mass production (tree dry weight, the length of two year old wood and number of leaves) was significantly larger in the budded trees. Similarly the trunk cross sectional area was significantly larger 10 cm above and in the middle of the graft union, but not 10 cm below it. The Colt trees were the most vigorous followed by the seedling and Gisela 5. Minor differences between the different cultivars were registered. Xylem staining with aqueous safranin combined with quantitative image analysis showed that the rootstock stem had a higher proportion of stained tissue than the scion stem. Sections taken in the middle of the graft tissue and 10 cm above showed that the proportion of stained tissue declined proportionally with the distance from the roots. The total area of stained stem xylem was larger for the two vigorous rootstocks compared to Gisela 5. Small differences were observed between cultivars and propagation methods.
Sammendrag
Ein studerte om bladgjødsling med kalsium påverka fruktkvaliteten hjå plommer og kor haldbare fruktene var etter hausting. Bladgjødsling med kalsium hadde ingen signifikante verknader på fruktkvaliteten. Men kalsiumtilførsel syntest å utsetja mogninga noko (4 av 5 målte faktorar). Kalsiumhandsaming reduserte rotning under lagring av plommer. Men det var ingen sikre skilnader mellom dei ulike strategiane som var nytta. I eitt forsøksår var bladgjødsling tidleg i sesongen betre enn handsaming seint med omsyn til rotning etter hausting. I alle forsøka var det ein tendens til at frukter sprøyta med soppmiddel var mindre utsette for rotning enn kalsiumsprøyta frukter. Men skilnaden var berre signifikant i eitt forsøk.
Forfattere
Kristine Marie Olsen Unni Synnøve Lea Rune Slimestad Michel Verheul Cathrine LilloSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor Håkon Sivertsen Janis GailisSammendrag
The history of a web-based system for administrating data from a network of agrometeorological stations is shortly presented, and the module of this system containing the documentation of the instruments in this network is discussed in detail. The quality concept of meteorological data is the starting point in this discussion. The way of coupling the instruments and parameters on each meteorological station is shown, as well as use of this information by controlling and correcting meteorological data. Ideas of actor-network theory are discussed connected to future challenges of data integration and use of data from different sources in applications.
Forfattere
Tor Håkon SivertsenSammendrag
The topography of the earth influences the movements of parcels of air in the atmosphere. Wind systems blowing across mountain ridges sometimes excite stationary gravity wave systems behind and above ridges witrh a breath of about 10 km. The conceptual discussion in this paper is connected to the transport of wave energy in stationary gravity waves and stationary gravity inertia waves , where there are discontinuities in the parameters describing the vertical stratified atmosphere. The discussion is closely connected to two theorems by Eliassen and Palm (1961) showing that the vertical flux of wave energy is conserved throughout the atmosphere for a great class of systems. But the boundary conditions used by Eliassen and Palm (1961) in the gravity wave systems connecting the vertical layers in situations with discontinuities do not cover all possible physical situations of interest.
Forfattere
Tor Håkon SivertsenSammendrag
The concept of "advection" is a concept connected to horizontal transport of energy and mass by parcels of air in convective flow systems. It is a concept mainly used in the field of `meteorology", and the concept is given a definition in `International meteorological vocabulary" published by WMO -No.182 " in 1992. Thiis concept is also used in other fields of science, especially by biologists studying evaporation of water in fields and forests , leaf wetness duration in orchards, frost situations in crop canopies etc. Because `environmental fluid mechanics" should contain contributions from several different fields of science, meteorology, agronomy, fluid dynamics, soil sciences, hydrology agro meteorology etc., it is of importance that the specialists from the different branches of scientific research of environmental phenomena understand each other. The main intention of this presentation Is making this concept of `advection"more clear for different groups of scientists, and this is also a way of advertizing the need for general conceptual discussions in the field of `environmental fluid mechanics". The definition of `advection" given by `WMO" is presented, and then the concepts of divergence and convergence of flow systems of air are presented. The concept of turbulent flow systems are then briefly connected to this concept; and the concepts of `oasis effect" and `clothline effect" are discussed. Equations containing energy balance in the close vicinity of the ground is presented, and the advective components in these equations are discussed. Then the physical cntent of the Penman-equation and the Penman-Monteith-equation of potential and actual evaporation is shortly presented and discussed.( Advection is not contained in these equations.) The content of an empirical statistical formula, derived by determining `potential evaporation" using measurements from pan evaporimeters, is presented and discussed. In this case an `advection term" appears, and this `advection term" is connected to the `oasis-effect" of the evaporometer, and elements of the advective weather situation are contained in the monthly variation of the statistical coefficients. The difference in scope when describing weather by `empirical statistical equtions" or by equations derived by fluid dynamical concepts is also discussed- The possibilities of including advection terms in operational use in weather systems of agro meteorology of local spatial and temporal scale is discussed. Finally ideas for modifying the definition given by WMO on `advective flow systems" is presented. References: Johannson, W., 1969, Meteorologiska elements inflytande på avdunstningen från Anderssons evaporimeter, Grunförbätring, 22, 82-105 ( in Swedish).(`The influence of the meteorological elements on the evaporation from Anderssons evaporimeter") Rosenbewrg, N.J., Blad, B.D., and Verma, S.B., 1983, Microclimate The Biological Environment, John Wile & Sons, New york, Chichester, Brisbane, Toronto, Singapore, 405 pp. International Meteorological Vocabulary,1992, WMO/ CMM/ BMO - No. 182 Thom, A.S., 1975, Momentum, Mass and Heat Exchange of Plant Communities, in `Vegetation and the Atmosphere" edeited by J. L. Montei9th, Academic Press, 278 pp