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
Sammendrag
In this study, we present a new method for single tree segmentation and characterization from a canopy surface model (CSM), and its corresponding point cloud, based on airborne laser scanning. The method comprises new algorithms for controlling the shape of crown segments, and for residual adjustment of the canopy surface model (CSM). We present a new criterion that measures the success of locating trees, and demonstrate how this criterion can be used for optimizing the degree of CSM smoothing. From the adjusted CSM segments, we derived tree height and crown diameter, and based on all first laser pulse measurements within the segments we derived crown-base height. The method was applied and validated in a Norway spruce dominated forest reserve having a heterogeneous structure. The number of trees automatically detected varied with social status of the trees, from 93 percent of the dominant trees to 19 percent of the suppressed trees. The RMSE values for tree height, crown diameter, and crown-base height were around 1.2 m, 1.1 m, and 3.5 m, respectively. The method overestimated crown diameter (0.8 m) and crown base height (3.0 m).
Sammendrag
Det er ikke registrert sammendrag
2005
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Overvåkingsprogrammet for skogskader (OPS) har siden starten registrert skader på de undersøkte trærne. Målet med skaderegistreringene har vært og vil fortsatt være å forklare variasjoner i trærnes kronetetthet og kronefarge. Men fra og med 2005 ønsker ICP Forests en standardisert rapportering av skader på trær fra alle land som deltar i det europeiske overvåkingsprogrammet. En slik harmonisering av registreringer vil over tid kunne gi et bilde av utbredelse, forekomst og skadelige virkninger av insekter, sopp, værforhold eller andre årsaker som påvirker skogen i Europa. Uten denne informasjonen vil det være svært vanskelig å tolke kronetetthets- og kronefargeresultatene. Data fra skogskaderegistreringene vil også kunne bli brukt i andre internasjonale skogpolitiske sammenhenger, som blant annet spørsmålet om bærekraftig skogbruk. For å imøtekomme kravene i den nye internasjonale instruksen har Skogforsk og NIJOS i samarbeid plukket ut viktige sopper, insekter, vilt/beitedyr, værforhold og andre årsaker som kan påvirke trærne i norsk skog. De viktigste er presentert i dette heftet. Tekstene og bildene skal være en hjelp til gjenkjenning av skadene som kan observeres i trekronene.
Forfattere
Svein SolbergSammendrag
Forest damage will result in two general effects: defoliation and/or discolouration. The two available techniques in remote sensing of forests today, LiDAR and spectroscopy, are promising tools for monitoring these two, respectively. Merging data on foliar mass, estimated by LiDAR, with data on chlorophyll concentrations, estimated by spectroscopy, can provide data on chlorophyll mass pr area unit. Monitoring the temporal changes of this is likely to be a very good measure for variations in forest health.In order to check out the possibilities for this, we are now working on building relationships between foliar mass data and LiDAR data for single spruce trees. In total we have measurements of position and stem diameter on about 2000 trees distributed on 16 plots, where 64 trees are intensively sampled for estimating foliar mass, as well as crown size.We need to parameterize a relationship between the LiDAR data for each of these trees and their foliar mass (or leaf area). If we succeed to build this relationship, we will scale it up to provide foliar mass (or leaf area) estimates for every 10x10 m pixels in two SPOT images of the area.Together with a similar up-scaling of chlorophyll concentrations, based on spectroscopy, we will test the possibility of estimating chlorophyll mass per area from SPOT or other satellites. In addition, we have visually assessed data on crown density for all the trees, being a rough, but valuable data-set for validating the relationship.The work, being in progress now, includes several tasks:a) finding an appropriate canopy surface modelb) segmentation of treesc) estimating crown volume, and evt d) handling of smaller trees standing below (this is a heterogenous canopy layer forest) and e) handling of the relative influence of stem and branches.Additionally, we see some other benefits from using LiDAR together with airborne hyperspectral data and satellite data in general. Firstly, the combination of high resolution LiDAR and hyper-spectral data, is a good basis for separating the signals from ground vegetation and from the tree canopy. Secondly, LiDAR provides both a DTM and a canopy surface model, and they are two alternative surface models for the geo-referencing of other data, and for appropriate handling of effects of shadowing and obstacles from tall trees.
2004
Sammendrag
Det er foretatt kartlegging av arealer og skogressurser som ligger innenfor de ulike kategorier inngrepsfrie naturområder, og i buffersonen rundt disse hvor det ikke kan bygges veier dersom de inngrepsfrie områdene skal bevares som inngrepsfrie. Sannsynligvis vil noe mer enn halvparten av den 1 km brede buffersonen rundt de inngrepsfrie områdene kunne utnyttes uten bygging av nye veier. Dermed vil bevaring av alle inngrepsfrie områder medføre at 15-20% av produktivt skogareal ikke vil kunne nyttes.
Forfattere
Lars Sandved Dalen H. Danforth J. Einset Carl Gunnar Fossdal Aksel Granhus Øystein Johnsen Harald Kvaalen Nina Elisabeth Nagy P. Rinne Linda Ripel S. Torre Gunnhild Søgaard C. van der SchootSammendrag
Det er ikke registrert sammendrag
Forfattere
Svein SolbergSammendrag
Det er ikke registrert sammendrag
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Extensive monitoring of forest health in Europe has been carried out for two decades, based mainly on defoliation and discolouration. Together these two variables reflect chlorophyll amounts in the tree crown, i.e. as an indicator of foliar mass, and chlorophyll concentration in the foliage, respectively.In a current project we try to apply remote sensing techniques to estimate canopy chlorophyll mass, being a suitable forest health variable. So far, we limit this to Norway spruce only. LIDAR data here play an important role, together with optical and spectral data, either from survey flights or from satellites. We intend to model relationships between foliar mass and LIDAR data for sample trees, and then scale up this to foliar mass estimates for the entire LIDAR area.Similarly, we try to scale up chlorophyll concentrations in sample trees, by modelling a relationship between sample tree chlorophyll and hyper-spectral data. The estimates of foliar mass and chlorophyll concentrations are then aggregated to every 10x10 m pixel of a SPOT satellite scene which is also covered by airborne data, providing an up-scaled ground truth. If we are successful with this, it might be a starting point for developing a new nationwide forest health monitoring system in Norway.