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.
2010
Forfattere
Erling MeisingsetSammendrag
Det er ikke registrert sammendrag
Forfattere
Kjersti Holt HanssenSammendrag
De siste årene har det blitt rapportert om stedvis kraftige angrep av gransnutebiller i foryngelsesfelt på Vestlandet og i Trøndelagsfylkene. Vi ønsket derfor å gjennomføre en undersøkelse av snutebilleskader i felt på Vestlandet og i Trøndelag. Til sammen 50 flater i kystfylkene Rogaland, Hordaland, Sogn og Fjordane, Møre og Romsdal, Sør-Trøndelag og Nord-Trøndelag ble undersøkt høsten 2009. Disse var plantet til i 2008 eller 2009, og det hadde ikke gått mer enn to sesonger siden hogst ved tilplantingen. På hvert felt ble alle kulturplantene på 20 sirkelflater á 20 m2 undersøkt for snutebillegnag og andre skader, og vitaliteten ble bedømt i fire klasser. For hvert felt ble variabler som høyde over havet, flatestørrelse, helling, eksposisjon og plantetype registrert.....
Sammendrag
Competition for canopy space is a fundamental structuring feature of forest ecosystems and remains an enduring focus of research attention. We used a spatial neighborhood approach to quantify the influence of local competition on the size of individual tree crowns in north-central British Columbia, where forests are dominated by subalpine fir (Abies lasiocarpa), lodgepole pine (Pinus contorta) and interior spruce (Picea glaucax engelmanii).Using maximum likelihood methods, we quantified crown radius and length as functions of tree size and competition, estimated by the species identity and spatial arrangement of neighboring trees.Tree crown size depended on tree bole size in all species. Given low levels of competition, pine displayed the widest, shortest tree crowns compared to the relatively long and narrow crowns found in spruce and fir. Sensitivity to crowding by neighbors declined with increasing tree height in all but the pine crown radius model. Five of the six selected best models included separate competition coefficients for each neighboring tree species, evidence that species generally differ in their competitive effects on neighboring tree crowns.The selected crown radius model for lodgepole pine, a shade-intolerant species, treated all neighbors as equivalent competitors. In all species, competition from neighbors exerted an important influence on crown size. Per-capita effects of competition across different sizes and species of neighbors and target trees varied, but subalpine fir generally displayed the strongest competitive effects on neighbors.Results from this study provide evidence that species differ both in their response to competition and in their competitive influence on neighbors, factors that may contribute to maintaining coexistence.
Sammendrag
The primary aim of this study was to investigate the suitability of interferometric X-band SAR (InSAR) for inventory of boreal forest biomass. We investigated the relationship between SRTM X-band InSAR height and above-ground biomass in a study area in southern Norway. We generated biomass reference data for each SRTM pixel from a field inventory in combination with airborne laser scanning (ALS). One set of forest inventory plots served for calibrating ALS based biomass models, and another set of field plots was used to validate these models. The biomass values obtained in this way ranged up to 250 t/ha at the stand level. The relationship between biomass and InSAR height was linear, no apparent saturation effect was present, and the accuracy was high (RMSE = 19%). The relationship differed between Norway spruce and Scots pine, where an increase in InSAR height of 1 m corresponded to an increase in biomass of 9.9 and 7.0 t/ha. respectively. Using a high-quality terrain model from ALS enabled biomass to be estimated with a higher accuracy as compared to using a terrain model from topographic maps. Interferometric X-band SAR appears to be a promising method for forest biomass monitoring. (C) 2010 Elsevier Inc. All rights reserved.
Forfattere
Rasmus AstrupSammendrag
Skog som hugges til sagtømmer, massevirke eller bioenergi vil gjenoppstå og er – i motsetning til fossilt brennstoff – fornybar. Spørsmålet er bare i hvilket tidsperspektiv. Skogen bør hugges for å gi størst mulig produksjon av trevirke over tid. Rapporten ”Klimakur 2020” har skapt debatt om skogens rolle i klimapolitikken, og rundt bruken av skog som klimatiltak. Skog er sentral for klimagassregnskapet – både nasjonalt og globalt. Men skal skogen brukes til å maksimere CO2–opptaket på kort sikt, eller er hovedmålet mer langsiktig; leveranse av energi og trematerialer på vei mot et karbonnøytralt samfunn?
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
I denne rapporten legges det frem en metode utviklet for å identifisere konfliktområder mellom viktige naturverdier og spredning av fremmede karplantearter langs samferdselsårer. I korte trekk består metoden av en geografisk analyse der sammenfall mellom stedfestede data for samferdselsårer og tilgrensende arealer med viktige naturverdier vurderes mot truslene som forekomster av fremmede karplantearter representerer i disse potensielle konfliktområdene. Analysen tar utgangspunkt i data tilgjengelige gjennom nasjonal geografisk infrastruktur - Norge digitalt og tilsvarende nasjonale samarbeidsinitiativ som Artsdatabanken, Naturbase og lignende. [...]
Forfattere
Miguel D. Mahecha Markus Reichstein Martin Jung Sonia I. Seneviratne Sönke Zaehle Christian Beer Maarten C. Braakhekke Nuno Carvalhais Holger Lange Guerric Le Maire Eddy MoorsSammendrag
Terrestrial biosphere models are indispensable tools for analyzing the biosphere-atmosphere exchange of carbon and water. Evaluation of these models using site level observations scrutinizes our current understanding of biospheric responses to meteorological variables. Here we propose a novel model-data comparison strategy considering that CO2 and H2O exchanges fluctuate on a wide range of timescales. Decomposing simulated and observed time series into subsignals allows to quantify model performance as a function of frequency, and to localize model-data disagreement in time. This approach is illustrated using site level predictions from two models of different complexity, Organizing Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) and Lund-Potsdam-Jena (LPJ), at four eddy covariance towers in different climates. Frequency-dependent errors reveal substantial model-data disagreement in seasonal-annual and high-frequency net CO2 fluxes. By localizing these errors in time we can trace these back, for example, to overestimations of seasonal-annual periodicities of ecosystem respiration during spring greenup and autumn in both models. In the same frequencies, systematic misrepresentations of CO2 uptake severely affect the performance of LPJ, which is a consequence of the parsimonious representation of phenology. ORCHIDEE shows pronounced model-data disagreements in the high-frequency fluctuations of evapotranspiration across the four sites. We highlight the advantages that our novel methodology offers for a rigorous model evaluation compared to classical model evaluation approaches. We propose that ongoing model development will benefit from considering model-data (dis)agreements in the time-frequency domain.
Forfattere
Miguel D. Mahecha Markus Reichstein Nuno Carvalhais Gitta Lasslop Holger Lange Sonia I. Seneviratne Rodrigo Vargas Christof Ammann M.Altaf Arain Alessandro Cescatti Ivan A. Janssens Mirco Migliavacca Leonardo Montagnani Andrew D. RichardsonSammendrag
The respiratory release of carbon dioxide (CO2) from the land surface is a major flux in the global carbon cycle, antipodal to photosynthetic CO2 uptake. Understanding the sensitivity of respiratory processes to temperature is central for quantifying the climate–carbon cycle feedback. We approximated the sensitivity of terrestrial ecosystem respiration to air temperature (Q10) across 60 FLUXNET sites with the use of a methodology that circumvents confounding effects. Contrary to previous findings, our results suggest that Q10 is independent of mean annual temperature, does not differ among biomes, and is confined to values around 1.4 ± 0.1. The strong relation between photosynthesis and respiration, by contrast, is highly variable among sites. The results may partly explain a less pronounced climate–carbon cycle feedback than suggested by current carbon cycle climate models.
Sammendrag
Information retrieval from spatiotemporal data cubes is key to earth system sciences. Respective analyses need to consider two fundamental issues: First, natural phenomena fluctuate on different time scales. Second, these characteristic temporal patterns induce multiple geographical gradients. Here we propose an integrated approach of subsignal extraction and dimensionality reduction to extract geographical gradients on multiple time scales. The approach is exemplified using global remote sensing estimates of photosynthetic activity. A wide range of partly well interpretable gradients is retrieved. For instance, well known climate-induced anomalies in FAPAR over Africa and South America during the last severe ENSO event are identified. Also, the precise geographical patterns of the annual–seasonal cycle and its phasing are isolated. Other features lead to new questions on the underlying environmental dynamics. Our method can provide benchmarks for comparisons of data cubes, model runs, and thus be used as a basis for sophisticated model performance evaluations.