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.
2012
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2011
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This study is a part of a larger project designed to find out the causes of top dieback symptoms in Norway spruce in SE Norway. Because sapwood tracheids constitute a water transport system while parenchyma serves as a reserve tissue (Sellin, 1991), the separation and quantification of the sapwood and heartwood may contribute to understanding of the healthy tree functioning. As the extent of sapwood is related to tree vitality, it reflects the tree growth, health and effect of environmental factors (Sandberg & Sterley, 2009). Therefore, the sapwood cross-sectional area is widely used as a biometric parameter indicating the tree vitality, although its estimation and evaluation is prone to scaling errors....
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Aims Beech (Fagus sylvatica L.) is an important species in natural and managed forests in Europe. This drought-sensitive species dominates even-aged stands as well more natural stands composed of a mixture of tree species, age and size classes. This study evaluates the extent that heterogeneity in spacing and tree diameter affect the seasonal availability and use of water. Methods Two stands were evaluated: 1) a heterogeneous forest remnant (NAT) with trees up to ca. 300 years old, a mean top height of 28.4 m, and a total of 733 stems ha-1 with stem diameters averaging 18 cm and 2) an even-aged 80-year old stand (MAN), with a height of 25 m, and a total of 283 stems ha-1 with diameters averaging 38 cm. Stem sap flow, Js (g m-2 s-1), was continuously measured in 12 (MAN) and 13 (NAT) trees using 20 mm long heat dissipation sensors. Individual tree measures of sap flow were correlated using non-linear statistical methods with air vapour pressure deficit (D, hPa) and global radiation (Rg, J m-2 day-1), along with contraints imposed by reductions in soil water content (SWC). Soil water content was measured as volumetric % using time domain reflectometry. Important findings The daily integrated Js (Js-sum) for trees growing in the evenly spaced MAN stand and trees in canopy and closed forest positions in NAT stand decreased as the availability of soil moisture was reduced. In the heterogeneous NAT stand, SWC in a recently formed canopy gap remained high throughout the vegetation period. Based on regression models, the predicted relative decrease in Js-sum for dry relative to moist soil water conditions in the closed forest (at mean daily D = 10 hPa) was 7-11% for trees near the gap and 39-42% for trees in the closed forest. In MAN the reduction in Js-sum was 29% in dry relative to moist conditions. Js-sum in the outer 20 mm of the xylem in NAT was lower than that in MAN and the rate of decline in Js with xylem depth was less in NAT than in MAN. In MAN, Js-sum in deep and outer xylem was negatively affected at low soil moisture availability; in NAT this was the case for only the outer xylem indicating that deep roots could be important in supplying water at times of low soil moisture in the upper soil.
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Authors
Gunnhild Søgaard Inger Sundheim Fløistad Aksel Granhus Kjersti Holt Hanssen Harald Kvaalen Tore Skrøppa Arne SteffenremAbstract
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The species composition of wood-inhabiting fungi (polypores and corticoids) was investigated on 1138 spruce logs and 992 pine logs in 90 managed and 34 natural or near-natural spruce and pine forests in SE Norway. Altogether, the study included 290 species of wood-inhabiting fungi. Comparisons of logs with similar properties (standardized tree species, decay class, dimension class) in natural and managed forests showed a significant reduction in species number per log in managed spruce forests, but not in managed pine forests. The species number per log in managed spruce forests was 10–55% lower than on logs from natural spruce forests. The reduction was strongest on logs of large dimensions. A comparison of 200–400 spruce logs from natural and managed forests showed a 25% reduction in species richness corresponding to a conservative loss of ca. 40 species on a regional scale. A closer inspection revealed that species confined to medium and very decayed spruce logs were disfavored in managed forests, whereas species on early decay classes and decay generalists were unaffected. Similarly, species preferring large spruce logs were disfavored in managed forests. Forest management had strongest impact on low-frequent species in the spruce forests (more than 50% reduction), whereas common species were modestly affected. Corticoid fungi were more adversely affected than polypore fungi. These results indicate that wood-decaying fungi in pine forests are more adapted to forest disturbances than spruce-associated species. Management measures securing a continuous supply of dead wood are more important in spruce forests than in pine forests.