Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2013
Abstract
There is a need for monitoring methods for forest volume, biomass and carbon based on satellite remote sensing. In the present study we tested interferometric X-band SAR (InSAR) from the Tandem-X mission. The aim of the study was to describe how accurate volume and biomass could be estimated from InSAR height and test whether the relationships were curvilinear or not. The study area was a spruce dominated forest in southeast Norway. We selected 28 stands in which we established 192 circular sample plots of 250 m2, accurately positioned by a Differential Global Positioning System (dGPS). Plot level data on stem volume and aboveground biomass were derived from field inventory. Stem volume ranged fromzero to 596 m3/ha, and aboveground biomass up to 338 t/ha.We generated 2 Digital Surface Models (DSMs) fromInSAR processing of two co-registered, HH-polarized TanDEM-X image pairs – one ascending and one descending pair.We used a Digital TerrainModel (DTM) from airborne laser scanning (ALS) as a reference and derived a 10 m × 10 m Canopy Height Model (CHM), or InSAR height model. We assigned each plot to the nearest 10 m × 10 m InSAR height pixel. We applied a nonlinear, mixed model for the volume and biomass modeling, and from a full model we removed effects with a backward stepwise approach. InSAR heightwas proportional to volume and aboveground biomass, where a 1 m increase in InSAR height corresponded to a volume increase of 23 m3/ha and a biomass increase of 14 t/ha. Root Mean Square Error (RMSE) values were 43–44% at the plot level and 19–20% at the stand level.
Abstract
No abstract has been registered
2012
Abstract
No abstract has been registered
Authors
Jonathan Edward Colman Diress Tsegaye Alemu Christian Pedersen Ruben Eidesen Herbjørg Arntsen Øystein Holand Alex Mann Eigil Reimers Stein Ragnar MoeAbstract
Interspecific interaction among sympatric ungulates is important in management and conservation. We investigated behavioral interference between sympatric wild or semidomestic reindeer (Rangifer tarandus tarandus) and sheep (Ovis aries) in two field studies and one enclosure experiment. For free-ranging wild and semidomestic reindeer, interference between the two species increased with decreasing distances, occurring only at less than 200 m and 30 m, for wild and semidomestic reindeer, respectively, and neither species consistently dominated the other. In a controlled, duplicated experiment we tested interference and confrontations at the feeding patch level among semidomestic reindeer and sheep within 40 × 50 m enclosures. When new reindeer or sheep were introduced into enclosures already occupied by reindeer, new reindeer resulted in significantly more interference and confrontations among individuals compared to new sheep; i.e., intraspecific interference was more prevalent than interspecific interference at equal densities. For all study areas, confrontations decreased with time after “first encounter,” indicating cohabituation. A sympatric use of pastures was not visually disruptive for recorded grazing behavior for either species.
Abstract
The objective of this paper is to examine a method for estimation of land cover statistics for local environments from available area frame surveys of larger, surrounding areas. The method is a simple version of the small-area estimation methodology. The starting point is a national area frame survey of land cover. This survey is post-stratified using a coarse land cover map based on topographic maps and segmentation of satellite images. The approach is to describe the land cover composition of each stratum and subsequently use the results to calculate land cover statistics for a smaller area where the relative distribution of the strata is known. The method was applied to a mountain environment in Gausdal in Eastern Norway and the result was compared to reference data from a complete in situ land cover map of the study area. The overall correlation (Pearson’s rho) between the observed and the estimated land cover figures was r = 0.95. The method does not produce a map of the target area and the estimation error was large for a few of the land cover classes. The overall conclusion is, however, that the method is applicable when the objective is to produce land cover statistics and the interest is the general composition of land cover classes – not the precise estimate of each class. The method will be applied in outfield pasture management in Norway, where it offers a cost-efficient way to screen the management units and identify local areas with a land cover composition suitable for grazing. The limited resources available for in situ land cover mapping can then be allocated efficiently to in-depth studies of the areas with the highest grazing potential. It is also expected that the method can be used to compile land cover statistics for other purposes as well, provided that the motivation is to describe the overall land cover composition and not to provide exact estimates for the individual land cover classes.
Authors
Gisela Lüscher Michaela Arndorfer Katalin Balázs K.G. Bernhardt M. Bogers R.G.H. Bunce J.-P. Choisis Peter Dennis Wenche E. Dramstad Sebastian Eiter Gunnar Engan Wendy Fjellstad T. Frank Jürgen Friedel Ilse Geijzendorffer P. Gillingham Felix Herzog K.-J. Hülsbergen Philippe Jeanneret G. Jerkovich Rob Jongman Maximilian Kainz M.L. Oschatz Susanne Papaja-Hülsbergen Philippe Pointereau Jean-Pierre Sarthou M.K. Schneider Norman Siebrecht Sebastian WolfrumAbstract
No abstract has been registered
Authors
Daniela Sauer Peter Finke Rolf Sørensen Ragnhild Sperstad Isabelle Schülli-Maurer Helge I. Høeg Karl StahrAbstract
The first results of modeling soil development in marine sediments in S Norway using the model SoilGen are compared to measured properties of two soil chronosequences, on the western and eastern side of Oslofjord, respectively. The aim of this work is to test how well soil development under well-defined environmental conditions can be modeled. Such testing reveals to what degree soil-forming processes are understood, allowing formulation of adequate calculations reflecting these processes. The model predicts particle size distribution reasonably well, although clay depletion in the upper parts of the soils as a result of clay migration is overestimated. The model tends to underestimate contents of organic carbon and CEC in the A horizons: below, modeled CEC matches well with measured CEC. Base saturation is overestimated in the upper 40 cm and underestimated below. Apparently, leaching of bases proceeds less rapidly in reality than is predicted by the model, due to strong soil structure of the B horizons, causing preferential flow and base leaching around the aggregates, whereas bases inside the aggregates are only slightly affected by leaching. Difficulties and possibilities for improvements are identified, some related to model input data and some to the model itself. Input data could be improved by determining the amounts of organic carbon in organic surface horizons and by quantifying effects of bioturbation. A big challenge is the implementation of soil structure formation in the model. Quantitative data on the development of soil structure with time that can be included in a model are required. Amounts, distribution and connectivity of macro pores need to be defined for each stage of soil development, and zones of low and high base leaching need to be distinguished in the model for each time step. The long-term aim of this work is to model soil development with different sets of soil-forming factors, e.g. different climatic conditions in order to reliably predict soil development under different climate scenarios and related sets of soil-forming factors. The results of the first model runs and the identified possible improvements suggest that this aim is generally achievable.
Abstract
Et overordnet samfunnsmål er å sikre en bærekraftig bruk og forvaltning av Norges arealressurser. Det krever en kontinuerlig leveranse av pålitelig og oppdatert informasjon til beslutningstakere. For å være i stand til å levere denne informasjonen, produserer Norsk institutt for skog og landskap blant annet arealressursstatistikk for alle kommuner i Norge. Statistikken produseres også på fylkesnivå og for hele landet. Arealtallene hentes ut fra en kombinasjon av ulike nasjonale datasett i ulike målestokker sammen med tolkning av satellittbilder. Gjennom en omklassifisering beregnes statistikk for visse landressursklasser som dyrka jord, beite, skog basert på produktivitet, ferskvann, snø og isbre, snaumark og bebygd område. Skog og landskap har de siste par årene brukt åpen kildekode. Hele produksjonslinje utføres ved hjelp av slik programvare. Resultatene lagres i XML-filer som legges ut på internett. Produksjonen krever behandling av flere databaser med nasjonal dekning og må håndtere geometriske operasjoner effektivt og uten feil. Den åpne kildekodeløsningen er pålitelig, stabil og rask.
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No abstract has been registered
Abstract
No abstract has been registered