Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2002
Authors
H. Mäkinen P. Nöjd H.P. Kahle U. Neumann Bjørn Tveite K. Mielikäinen H. Röhle H. SpieckerAbstract
Regional and temporal growth variation of Norway spruce (Picea abies (L.) Karst.) and its dependence on air temperature and precipitation were compared in stands across latitudinal and altitudinal transects in southwestern and eastern Germany, Norway, and Finland.The temporal variation of radial growth was divided into two components: medium- and high-frequency variation, i.e. decadal and year-to-year variation, respectively. The medium-frequency component was rather different between regions, especially the southern and northern ones. However, within each region the medium-frequency growth variation was relatively similar, irrespective of altitudinal and latitudinal differences of the sample sites.A part of the high-frequency variation was common to all four regions, which suggests that some factors synchronising tree growth are common for the entire study area. The high-frequency component of growth was more strongly related to monthly air temperature and precipitation than was the medium-frequency variation. The limiting effect of low temperatures was more significant at northern as well as high-altitude sites, while the importance of precipitation increased in the south and at low altitudes.
Abstract
Concentrations and fluxes of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), together with pools of carbon and nitrogen in the soil and biomass, were determined along north-south and east-west transects across Norway, Sweden and Finland. The data were analysed statistically and modelled using the mechanistic model DyDOC.Concentrations of DOC and DON were greatest in the O horizon and decreased downwards in the soil. The highest production of dissolved organic matter appears to take place in the O horizon and any contribution from thoroughfall is probably small. A pronounced seasonal effect with peak DOC concentrations in late summer/early autumn may be due to a seasonal (largely temperature) effect on DOC production.The effect of acidic precipitation upon DOC concentrations and fluxes was unclear. DOC in the O horizon was mostly of recent origin, while DOC in the B horizon appeared to include some older material, possibly desorbed from the soil. A positive correlation was found with electrical conductivity and a negative correlation with pH in DOC concentrations from the O horizon.A lack of correlation between DOC concentrations and temperature is probably due to a time lag between peak temperatures and peak DOC concentrations. Modelling of DOC concentrations and fluxes using DyDOC gave rasonable results, suggesting that it might be possible to use DyDOC as a general tool for modelling and forecasting DOC concentrations and fluxes in Nordic forest ecosytems.Scenario analysis using DyDOC suggested that increased temperature without increased litter input might result in increased production of CO2 rather than DOC. An increase in both temperature and litter input would lead to increased DOC concentrations, with possible implications for drinking water quality. Increased precipitation will lead to increased fluxes of DOC.
Authors
Harald Kvaalen Ola Gram Dæhlen Ulrika EgertsdotterAbstract
No abstract has been registered
Authors
David Wei Zheng M. Freeman J. Bergh Ingvald Røsberg Petter NilsenAbstract
A process-based model was used to simulate biomass production of Norway spruce under both current climate and climate change scenarios. The model was parameterized for Nordmoen in south-east Norway using real climate data for the period 1987-1989. The model was applied to predict the biomass production responses to three climate change scenarios.The results showed that net primary production (NPP) increased by 7% under an elevated annual mean air temperature of 4C from the current 10.1 t dry mass ha-1 yr-1. A doubled current ambient CO2 concentration significantly increased NPP by 36%.The scenario of both elevated temperature and elevated CO2 concentration led to an increase in the NPP of 49%, higher than the sum of the two effects acting singly. The results also showed that forest production responses to climate change depend on the conditions of climate used for reference.
Authors
Erik Næsset Tonje ØklandAbstract
Tree height, the height from the ground surface to the tree crown, and the crown length as a proportion of tree height of individual trees were derived from various canopy height metrics measured by a small-footprint airborne laser scanner flown over a boreal forest reserve. The average spacing on the ground of the laser pulses ranged from 0.66 to 1.29 m. Ground-truth values were regressed against laser-derived canopy height metrics. The regressions explained 75%, 53%, and 51% of the variability in ground-truth tree height, height to the crown, and relative crown length, respectively. Cross-validation of the regressions revealed standard deviations of the differences between predicted and ground-truth values of 3.15 m (17.6%), 2.19 m (39.1%), and 10.48% (14.9% of ground-truth mean), respectively. On 10 plots with size 50 m2 in the boreal forest reserve and on 27 plots with size 200 m2 in a managed spruce forest, mean tree height, average height from the ground surface to the crown, and average relative crown length were regressed against laser canopy height metrics. The coefficients of determination (R2) ranged from .47 to .91. Cross-validation revealed a precision of 1.49 m (7.6%), 1.24-1.52 m (20.9-23.3%), and 6.32-7.11% (8.8-10.9% of ground-truth mean) for mean tree height, average height to the crown, and average relative crown length, respectively. At least, mean tree height can be determined more accurately from laser data than by current methods.
Authors
Kjersti Holt HanssenAbstract
No abstract has been registered
Authors
Gro HylenAbstract
No abstract has been registered
Authors
Bernt-Håvard Øyen Petter NilsenAbstract
Growth effects in a sub-alpine, low-yield Norway spruce forest in southeast Norway are reported. Sixteen sample plots of 400 m2, established 8-9 years after a mountain forest selective (MFS) cutting in the mid-1970s, were re-investigated in 2000. The selective cutting was heavy, with a mean felling volume of 72 per cent of the standing volume. Most trees in the remaining stands responded positively with increased growth after the cutting, and this was most pronounced in small and medium sized trees. A weak relationship between standing volume before and after felling, and the actual stand volume increment in the 25-year period was revealed. The felling has stimulated natural regeneration and increased the proportion of birch. The results indicate that not more than ~65 per cent of the standing volume should be cut in a single intervention if cutting cycle is less than 50 years.
Authors
Oddvar Skre R. Baxter R.M.M. Crawford T.V. Callaghan A. FedorkovAbstract
Modeling studies indicate that if the global warming persists over centuries, the tundra-taiga boundary will move northwards. However, on a regional scale large variations may exist, and in oceanic areas a southwards retreat may also be expected. This tendency is reinforced by human activity, in particular in northern Russia. Local changes over short periods therefore requires continuous observation and monitoring of treeline movement, from an economic as well as forecology and conservation.
Authors
Kjell Andreassen Bernt-Håvard ØyenAbstract
Six experimental sites in the coastal spruce (Picea abies L. Karst.) forest of central Norway were investigated. A comparison of different silviculture systems was performed based on the present situation of mature stands, and a single tree selection system, a group system and a clearcutting system were studied. The diameter distribution shows the classical inverse J-shaped curve at five of six sites. The mean tree volume removed in the selection system was 0.6 m3, and about 0.3 m3 for the other two methods. The harvesting cost was about 14 Euro/m3 for clearcutting, and about 10% higher for the group and selection systems. In simulations of all future revenues and expenses based on the observed stand conditions, cutting and extraction costs, the net present value (NPV) was app. 15% lower for the group and selection systems compared to clearcutting. A lower stem volume production in uneven-aged stands and higher administration and harvesting costs had only a minor influence on the NPV. One percent higher interest rate lowered the NPV of the group and selection systems to 75% of the clearcutting method.