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.
2008
Sammendrag
Many time series analysis methods depend on equally spaced observations with no data point missing. If this condition is met, powerful techniques are available that identify temporal structures such as trends or periodic phenomena or nonlinear dynamics. Unfortunately, most of observations of natural systems, in particular over longer periods of time such as decades, are prone to sampling errors leading to missing points in the observations. Singular System Analysis (SSA) is a powerful tool to extract the dynamics contained in time series at arbitrary temporal scales...
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
Twenty-one species of green algae isolated from marine, freshwater and terrestrial environments were screened for the ability to produce H2 under anaerobic conditions. Seven strains found positive for H2 production under anaerobic conditions were also screened for the ability to produce H2 under sulfur (S) deprivation. In addition to the traditional model species Chlamydomonas reinhardtii, C. noctigama (freshwater) and C. euryale (brackish water) were able to produce significant amounts of H2 under S-deprivation. These species were also able to utilize acetate as a substrate for growth in light. The S-deprivation experiments were performed under photoheterotrophic conditions in a purpose-specific designed bioreactor, and it was shown that an automated pH adjustment feature was essential to maintain a stable pH in the cultures. Several materials commonly used in bioreactors, such as rubber materials, plastics and steel alloys, had a negative effect on the survival of S-deprived algae cultures. Unexpectedly, traces of H2 were produced under S-deprivation during O2 saturation in the cultures, possibly derived from local anaerobic environments formed in algal biofilms on the membranes covering the O2 electrodes.
Sammendrag
Runoff time series are known to contain long term structures on interannual to decadal time scales. Investigating spatial patterns of long term structures is a way to elucidate the relationship between external forcings and watershed properties. This would be a valuable contribution to an improved water resources management. Singular System Analysis (SSA) is a powerful technique to identify and extract significant long term components from time series. However, many observations from natural systems are prone to missing data that hamper many analysis techniques, including the SSA in its original formulation...
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Sammendrag
Insect-induced damages in forests are a major concern for timber production, landscape conservation and ecosystem research. Early detection methods based on remote sensing data can document the severity and spatial extent of ongoing attacks and might aid in designing mitigation measures or even prevention where necessary. In southeastern Norway, a large-scale insect defoliation of pine trees is ongoing. The larvae of the Pine sawfly Neodiprion sertifer reate it with its mass attacks during their feeding on needles in June and July. In the winter before the attack, egg galleries are evident in the needles. This provides a test case for early detection methods and remote sensing techniques for monitoring forest health....
Forfattere
Ketil HaarstadSammendrag
Det er ikke registrert sammendrag
Forfattere
Tormod Briseid Anne BøenSammendrag
Hvordan kan man kan få et marked for avfallsbasert biorest.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
In European forests, standings stocks are currently increasing and are higher than ever during the last decades. This is due to a multitude of reasons; human impacts such as reduced logging or the abandonment of agricultural land are clearly among them. However, data from intensive monitoring plots reveal an increased growth even in the absence of direct human intervention. For this study, we used a set of 363 such plots from 16 European countries, which are a subset of the ICP-Forests Level II plots, and are typically rectangular areas with a size of 0.25 ha. We investigated the influence of environmental factors on forest growth. In particular, the role of nitrogen, sulphur and acid deposition, temperature, precipitation and drought was elucidated. The study focussed on the tree species Norway spruce, Scots pine, common beech and European as well as sessile oak. We used existing information on site productivity, stand age and stand density to estimate expected growth. Relative tree growth was then calculated as the ratio between actual growth, obtained within a five years observation period, and expected growth. The site productivity incorporates past environmental conditions and was either computed from site index curves, where we distinguished Northern, Central and Southern Europe variants, or was taken from expert estimates. The models explained between 18% and 39% of the variance. Site productivity and stand age were positively and negatively related to actual growth, respectively. The results indicated consistently a fertilizing effect from nitrogen deposition, with roughly one percent increase in site productivity per kg of nitrogen deposition per ha and year, most pronounced for plots having soil C/N ratios above 25. We also found a positive albeit less clear relationship between relative growth and summer temperatures. Other influences were uncertain. In particular, we cannot conclude on detrimental effects on growth from sulphur and acid deposition or from drought periods.