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.
2017
Sammendrag
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Sammendrag
The use of digital aerial photogrammetry (DAP) for forest inventory purposes has been widely studied and can produce comparable accuracy compared with airborne laser scanning (ALS) in small, homogeneous areas. However, the accuracy of DAP for large scale applications with heterogeneous terrain and forest vegetation has not yet been reported. In this study we examined the accuracy of timber volume, biomass and basal area prediction models based on DAP and national forest inventory (NFI) data on a large area in central Norway. Two separate point clouds were derived from aerial image acquisitions of 2010 and 2013. Vegetation heights were extracted by subtracting terrain elevation derived from ALS. A large number of NFI sample plots (483) measured between 2010 and 2014 were used as reference data to fit linear models for timber volume, biomass and basal area with height metrics derived from the DAP data as explanatory variables. Variables describing the heterogeneous environmental and image acquisition conditions were calculated and their influence on the model accuracy was tested. The results showed that forest parameter prediction using DAP works well when applied to a large area. The model fits of the timber volume, biomass and basal area models were good with R2 of 0.80, 0.81, 0.81 and RMSEs of 41.43 m3 ha−1 (55% of the mean observed value), 32.49 t ha−1 (47%), 5.19 m2 ha−1 (41%), respectively. Only a small proportion of the variation could be attributed to the heterogeneous conditions. The inclusion of the relative sun inclination led to an improvement of the model RMSEs by 2% of the mean observed values. The relatively low cost and stability across large areas make DAP an attractive source of auxiliary information for large scale forest inventories.
Forfattere
Belachew Gizachew Zeleke Rasmus Astrup Pål Olav Vedeld Eliakimu M. Zahabu Lalisa A. DugumaSammendrag
REDD+, a climate change mitigation mechanism that values carbon in tropical forests, is expected to provide Africa with a range of environmental and socio-economic benefits. Drawing on a vast array of literature and personal experiences, this review analyzed particular features and challenges that REDD+ implementation has faced on the continent. The distinct contexts and major challenges regarding governance, finance and technical capacities are discussed, and mechanisms to fill these gaps are suggested. Radical land tenure reform and a perfect safeguard mechanism that transfers forest land and carbon to the communities are unlikely. REDD+ should rather look for systems that respect local institutional arrangements, and allow forest-based communities to participate in decision-making and benefit sharing, particularly benefits from emerging REDD+. Finances for REDD+ infrastructure and the results-based payment are in short supply. While negotiating for potential external sources in the short term, Africa should generate domestic financial resources and look for additional payments for ecosystem services. Africa should also negotiate for forest monitoring capacity building, while strengthening local community forest monitoring. This review contributes to an improved understanding of the contexts and challenges to consider in the capacity and policy development for REDD+ implementation.
Forfattere
Graham Alan Ormondroyd Gry Alfredsen Raghavalu Thirumalai Durai Prabhakaran Simon F. Curling Bronia K. Stefanowski Morwenna J. Spear Lone RossSammendrag
Microbiological degradation of wood by decay fungi can cause a rapid change in the structural properties of timber which can result in both strength and mass loss. Traditional techniques for the evaluation of decay (e.g. mass loss) lack the sensitivity to evaluate the effects of the very first stages of the decay process. This paper describes the effects of initial brown rot decay, defined by the amount of Poria placenta genomic DNA (gDNA) present in the samples, on the dynamic mechanical properties of the timber. It was found that there is a correlation between the mean storage modulus of the timber and the amount of P. placenta gDNA present, and therefore the level of decay. This shows that using dynamic mechanical analysis is a viable technique that can be used to study initial decay processes.
Sammendrag
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Forfattere
Linda Meyer-Veltrup Christian Brischke Gry Alfredsen Miha Humar Per Otto Flæte Tord Isaksson Pia Larsson Brelid Mats Westin Jöran JermerSammendrag
Comprehensive approaches to predict performance of wood products are requested by international standards, and the first attempts have been made in the frame of European research projects. However, there is still an imminent need for a methodology to implement the durability and moisture performance of wood in an engineering design method and performance classification system. The aim of this study was therefore to establish an approach to predict service life of wood above ground taking into account the combined effect of wetting ability and durability data. A comprehensive data set was obtained from laboratory durability tests and still ongoing field trials in Norway, Germany and Sweden. In addition, four different wetting ability tests were performed with the same material. Based on a dose– response concept, decay rates for specimens exposed above ground were predicted implementing various indicating factors. A model was developed and optimised taking into account the resistance of wood against soft, white and brown rot as well as relevant types of water uptake and release. Decay rates from above-ground field tests at different test sites in Norway were predicted with the model. In a second step, the model was validated using data from laboratory and field tests performed in Germany and Sweden. The model was found to be fairly reliable, and it has the advantage to get implemented into existing engineering design guidelines. The approach at hand might furthermore be used for implementing wetting ability data into performance classification as requested by European standardisation bodies.
Forfattere
Stephanie Eisner Martina Flörke Alejandro Chamorro Prasad Daggupati Chantal Donnelly J. Huang Yeshewatesfa Hundecha Hagen Koch Andrey Kalugin Inna Krylenko Vimal Mishra Mikołaj Piniewski Luis Samaniego Ousmane Seidou Markus Wallner Valentina KrysanovaSammendrag
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Forfattere
Hugh Cross Jørn Henrik Sønstebø Nina Elisabeth Nagy Volkmar Timmermann Halvor Solheim Isabella Børja Håvard Kauserud Tor Carlsen Barbara Rzepka Katarzyna Wasak Adam Vivian-Smith Ari HietalaSammendrag
High biodiversity is regarded as a barrier against biological invasions. We hypothesized that the invasion success of the pathogenic ascomycete Hymenoscyphus fraxineus threatening common ash in Europe relates to differences in dispersal and colonization success between the invader and the diverse native competitors. Ash leaf mycobiome was monitored by high-throughput sequencing of the fungal internal transcribed spacer region (ITS) and quantitative PCR profiling of H. fraxineus DNA. Initiation of ascospore production by H. fraxineus after overwintering was followed by pathogen accumulation in asymptomatic leaves. The induction of necrotic leaf lesions coincided with escalation of H. fraxineus DNA levels and changes in proportion of biotrophs, followed by an increase of ubiquitous endophytes with pathogenic potential. H. fraxineus uses high propagule pressure to establish in leaves as quiescent thalli that switch to pathogenic mode once these thalli reach a certain threshold – the massive feedback from the saprophytic phase enables this fungus to challenge host defenses and the resident competitors in mid-season when their density in host tissues is still low. Despite the general correspondence between the ITS-1 and ITS-2 datasets, marker biases were observed, which suggests that multiple barcodes provide better overall representation of mycobiomes.
Sammendrag
Methods: In 2009, we resurveyed three plant sociological studies up to 85 years after the first surveys. Vegetation data were recorded from 1m2 non-permanently marked plots, and soil pH was measured. We applied restricted permutation tests to evaluate whether observed changes in vegetation (species richness, occurrence frequency, coverage) and in soil pH were significant and independent of plant community type. We compared species co-occurrences over time to study changes in species composition and to identify the species most likely causing these changes. Results: Total number of species and average number of species per plot has not changed and are 75 and 9, respectively. Occurrence frequency changed significantly for 34% of the 64 species tested (11 species increased, 11 decreased). Species cover decreased significantly for 27% of the species and increased for one species. Observed changes in frequency and cover are not significantly related with species’ functional groups or species affiliated with moist or dry habitats. Polygonum viviparum, Saxifraga cernua and Alopecurus borealis have changed most in co-occurring with other species. Soil pH increased significantly from 6.4 to 6.8. Conclusions: Our results suggest that the strong climatic warming in the High Arctic over the past decades has contributed to significant changes in the vegetation studied on Svalbard over the past 85 years. Internal community re-structuring and the overall stability in species richness may be explained by time-delayed responses of well-established communities, and/or by a limited size of the species pool in the area.
Sammendrag
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