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.
1999
Authors
Oddvar Skre M. NæssAbstract
No abstract has been registered
Authors
Oddvar SkreAbstract
Seedlings of white birch seem to tolerate high winter temperatures to a higher degree than spruce seedlings, and were also more able to take advantage of elevated CO2 levels. Large differences were observed between provenances in response patterns. The southern provenance of birch was more tolerant against raised winter temperatures than the northern ecotype, and the southern spruce provenance seemed to differ from the two northern provenances in the same way. The Icelandic birch population seemed to have developed a low-growth strategy with strong CO2 acclimation and no significant CO2 responses in photosynthetic rates and growth parameters. This differing response may be explained by long-term selection pressure due to heavy grazing. One of the spruce provenences showed a similar pattern.
Authors
M. Haapanen J. Mikola S. Ruotsalainen M. VenäläinenAbstract
No abstract has been registered
Authors
D. Lindgren Tim J. Mullin Y.Q. ZhengAbstract
No abstract has been registered
Authors
Sharon FriedmanAbstract
No abstract has been registered
Authors
Ulrik Bräuner NielsenAbstract
No abstract has been registered
Authors
Albert WinsentsAbstract
Describes results of a comparison of logging with running skylines on low bearing capacity terrain and typical skyline terrain in Norway. Study addresses technical issues of the same growing concern to minimize logging impact on sensitive terrain. Study also describes use of running skylines over special intermediate supports. Future research needs for mobile tailholds and supports, plus mechanized harvesting opportunities are suggested.
Authors
Tore SkrøppaAbstract
No abstract has been registered
Authors
Svein SolbergAbstract
Relationships within stands between growth and crown condition are presented. The data set contained about 25000 trees on 500 plots. Growth of single trees was determined by diameter measurements in 1991 and 1996. Diameter increments were recalculated to relative values in two steps; firstly relative to their stem diameter, and secondly relative to reference values for trees in the same plot, having no defoliation or no discoloration. These relative increment values, or growth indices, were distributed on a scale common for all plots, rendering them influenced neither by site and stand properties, nor by social status of each tree. The correlation between crown condition and growth, although of moderate strength, did validate crown condition assessments as a meaningful, but rough measure of forest health or vigour. The relationships were concave, and considerable growth depressions were already found at slight levels of defoliation and discoloration. Growth approached zero as defoliation and discoloration increased towards 100%. These relationships applied for all plots, regardless of their site productivity, development stage or regeneration method
Abstract
This study describes how crown density changes were distributed within monitoring plots, in order to determine whether the reduced crown density observed could be explained as a worsening of a limited number of unhealthy or small and slightly suppressed trees.Crown density, yellowing, coning and stem diameter data were available from 447 selected plots comprising 22560 single trees all having a complete 1990-97 series of crown condition data.The eight years series of crown density for each tree were recalculated to two median values, for 1990-93 and 1994-97, in order to reduce the influence from short time variations including random errors. The scores for yellowing and amounts of cones were averaged over the years 1990-93. These variables, and diameter, were recalculated to rank indices within each plot.Relationships between variables were described by graphs and examined by correlation analyses of the indices. The trees tended to retain their internal ranking. Generally, when crown density for a plot has changed, most of the trees were affected. The most defoliated trees in each plots had the least negative changes, but except from that the trees were equally affected regardless of their yellowing, amount of cones, and their size.The results demonstrates that any effects from competition between the trees were sufficiently removed in the assessments, even in densely stocked stands.