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.
2019
Sammendrag
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Forfattere
Inger HansenSammendrag
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Forfattere
Trygve S. AamlidSammendrag
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Sammendrag
Im Laufe der vergangenen 15 Jahre wurden in verschiedenen, vor allem europäischen Ländern große Anstrengungen unternommen, Modelle zur Vorhersage der Gebrauchsdauer von Holzbauteilen zu entwickeln. Heute steht ein System zur Verfügung, mit dem sich Exposition, Dimension, Konstruktionsdetails und die Fähigkeit des Holzes, Wasser aufzunehmen und wieder abzugeben, so miteinander in Beziehung setzen lassen, dass sich das feuchteinduzierte Befallsrisiko für Holzprodukte quantitativ abschätzen lässt. Das Ziel dieser Studie war es, die „Vorhersagekraft“ von Performancemodellen einerseits und unterschiedlichen Gruppen von Holzverwendern andererseits zu vergleichen. Neben Zimmerern und Tischlern wurden auch Holzwissenschaftler, Architekten und Kunden sogenannter „Heimwerkermärkte“ gebeten, die Zeitspanne zwischen Beginn der Exposition und dem ersten Auftreten pilzlicher Holzschäden für eine Reihe von Fallbeispielen mit bekannter Historie und Gebrauchsdauer abzuschätzen. Die verwendeten Modelle sagten die Gebrauchsdauern der Bauteile in den unterschiedlichen Fallbeispielen zufriedenstellend vorher, mit Ausnahme eines Spielgerätes, das aus schutzmittelbehandeltem Holz gefertigt war. Weitere materialspezifische Daten zur Resistenz und zum Feuchteverhalten sind offenbar notwendig, um die Genauigkeit des Modells zu erhöhen. In vielen Fällen lag der Mittelwert der Gebrauchsdauerabschätzung der Befragten ebenfalls recht nahe an der tatsächlich erreichten Gebrauchsdauer. Die Einzelschätzungen unterlagen hierbei jedoch einer extrem hohen Streuung. Expertengruppen, wie z. B. Holzhandwerker und Holzwissenschaftler, vermochten die Gebrauchsdauern nicht genauer vorherzusagen als die Gruppe von Laien. Die Notwendigkeit für umfassende und komplexe Vorhersageinstrumente wurde sehr deutlich, da weder Laien noch Experten sich in der Lage zeigten, ausreichend genau und statistisch verlässlich die Gebrauchsdauern von Holzbauteilen vorherzusagen.
Forfattere
Olalla Díaz-Yáñez Blas Mola-Yudego José Ramón González-OlabarriaSammendrag
Snow and wind damages are one of the major abiotic disturbances playing a major role in forest ecosystems and affecting both stand dynamics and forest management decisions. This study analyses the occurrence of wind and snow damage on Norwegian forests, based on data from four consecutive forest inventories (1995–2014). The methodological approach is based on boosted regression trees, a machine learning method aiming to demonstrate the effects of different variables on damage probability and their interactions as well as to spatialize damage occurrence to make predictions. In total, 313 models are fitted to detect trends, interactions and effects among the variables. The main variables associated with damage occurrence are consistent across all the models and include: latitude, altitude and slope (related to site and location), and tree density, mean diameter and height (related to forest characteristics). The results show that stand dominant height is a key variable in explaining damage probability, whereas stand slenderness has a limited effect. More heterogeneous forest structures make birch dominated stands more resistant to damage. Finally, the models are translated into occurrence maps, to provide landscape-level information on snow and wind damage hazard. Further application of the models can be oriented towards assessing the probability of damage for alternate stand management scenarios.
Forfattere
Marleen Pallandt Bernhard Ahrens Sönke Zaehle Marion Schrumpf Holger Lange Markus ReichsteinSammendrag
Soil organic carbon (SOC) is the largest terrestrial carbon pool. Changes in the hydrological cycle affect C-cycle turnover, with potential effects on the global C balance’s response to global change. However, large scale model representations of the sensitivity of soil carbon to soil moisture, through decomposition and interactions with nutrient cycles, are largely empirical to semi-empirical and uncertain. To better represent these dynamics, the aims of this PhD project* are to: • Investigate the role of soil moisture on SOC decomposition over a vertical profile; • Assess which moisture controls are (most) important in a multi-layered, mechanistic soil biogeochemistry model, the Jena Soil Model (JSM, Fig 2); • Update and improve the representations of soil moisture dynamics in JSM and evaluate this model for multiple sites along a moisture gradient and global scale.
Forfattere
Bernhard Ahrens Marleen Pallandt Markus Reichstein Holger Lange Marion Schrumpf Sonke ZaehleSammendrag
The Jena Soil Model (JSM) is a multi-layer mechanistic soil biogeochemistry model with explicit representations of vertical transport, mineral sorption, and microbial control on decomposition rates. Reaction rates are further modified by temperature and moisture. While temperature determines the maximum reaction velocity (Vmax), moisture reduces this rate nonlinearly if either the diffusion of substrate is restricted (at low soil moisture) or oxygen availability for microbes is limited (at wet conditions). This moisture control on soil organic matter formation and decomposition is represented with the Dual Arrhenius Michaelis-Menten (DAMM) model concept (Davidson et al. 2012) and influences the reaction rates of microbial depolymerisation of litter and microbial residue pools as well as DOC (dissolved organic matter) uptake. Sorption of DOM and microbial residues to mineral surfaces is moisture dependent through a Langmuir sorption approach. We will validate the carbon cycle representation of moisture control on soil organic matter decomposition in JSM by comparing simulations with measured carbon stocks and respiration rates from different ecosystems ranging from boreal upland forests and wetlands to Mediterranean savannas. The modular structure of JSM will allow us to investigate the effect of moisture control on each decomposition step (depolymerisation, microbial uptake and growth, and OC sorption) separately.
Sammendrag
Temperature during seed maturation can induce an epigenetic memory effect in growth phenology of Norway spruce (Picea abies (L.) Karst.) that lasts for several years. To quantify the epigenetic modifications induced by natural climatic variation, common garden experiments with plants originating from different provenances and seed years were performed. Plants from warmer seed years showed delayed phenology with later bud flush, bud set and growth cessation. This effect was quantified by linear models of phenology traits as a function of climate indices for the origin and seed year of the plants. Significant effects of the temperature during seed production (seed year) was found for the bud set in seedlings in their first growing season and for bud flush and growth cessation in the 7th-8th growing season from seed. The models suggest that growth start and growth cessation are delayed 0.7–1.8 days per 100 additional degree days experienced by the seed during embryo development and seed maturation. Models that include factors that are known to induce epigenetic effects could be used to better predict future performance of forest reproductive material.
Sammendrag
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Sammendrag
A negative impact of multiple anthropogenic stressors on surface waters can be observed worldwide threatening fresh- and marine water ecosystem functioning, integrity and services. Water pollution may result from point or diffuse sources. An important difference between a point and a diffuse source is that a point source may be collected, treated or controlled. Agricultural activities related to crop production are considered as diffuse sources and are among the main contributors of nutrient loads to open water courses, being to a large degree responsible for the eutrophication of inland and coastal waters. Knowledge of hydrological and biogeochemical processes are needed for climate adaptive water management as well as for introducing mitigation measures aiming to improve surface water quality. Mathematical models have the potential to estimate changes in hydrological and biogeochemical processes under changing climatic or land use conditions. These models, indeed, need careful calibration and testing before being applied in decision making. The aim of this study was to evaluate the efficiency of various water protective adaptation strategies and mitigation measures in reducing the soil particle and nutrient losses towards surface water courses from agricultural dominated catchments. We applied the INCA-N and INCA-P models to a well-studied Norwegian watershed belonging to the Norwegian Agricultural Environmental Monitoring Program. Available measurements on water discharge, TN and TP concentration of stream water and local expert knowledge were used as reference data on land-use specific sediment, N and P losses. The calibration and the validation of both the models was successful; the Nash-Sutcliffe statistics indicated good agreement between the measured and simulated discharge and nutrient loads data. Further, we created a scenario matrix consisting of land use and soil management scenarios combined with different climate change scenarios. Our results indicate that land use change can lead to more significant reduction in particle and nutrient losses than changes in agricultural practices. The most favourable scenario for freshwater ecosystems would be afforestation: changing half of the agricultural areas to forest would reduce sediment, total N and total P losses by approximately 44, 35 and 40%, respectively. Changes in agricultural practices could also improve the situation, especially by reducing areas with autumn tillage to a minimum. We concluded, that the implementation of realistic land use and soil management scenarios still would not lead to satisfactory reduction in freshwater pollution. Hence, mitigation measures, enhancing water and particle retention in the landscape – as sedimentation ponds, constructed wetlands etc. – are important in facing the upcoming pressures on water quality in the future.