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.
2011
Forfattere
Kjersti Holt HanssenSammendrag
The pine weevil (Hylobius abietis) is an important pest to conifer seedlings in large parts of Europe. To get an objective measure of the extent of damages related to pine weevils in South-Eastern Norway, a survey was implemented in the autumn of 2010 in nine counties. Altogether, 155 stands regenerated by planting in 2009 or 2010 were examined. The percentage of seedlings killed from pine weevil attacks varied between 0 and 63 % in the surveyed fields. On average, 7 % of the seedlings were killed by pine weevils, while 23 % had bark wounds. In addition, 3 % of the seedlings were killed by other causes. Few of the registered field variables were correlated to the degree of damage, but there was a tendency towards higher mortality at the largest clear cuts, in hilly areas, and for dry soil types. The present survey shows that in unscarified stands in SE Norway pine weevils are the most important cause of seedling mortality. A total seedling mortality of at least 10% should be expected the first two years.
Sammendrag
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Sammendrag
The use of logging residues for bioenergy is encouraged in many countries, due to an increasing demand for renewable energy. However, there is concern that removal of logging residues may cause a long-term reduction in soil nutrient availability, reducing forest growth in the remaining stand. To quantify the growth response of Norway spruce and Scots pine to whole-three harvesting at first thinning a series of eight field experiments was set up in SE Norway in the seventies. Results after 25 years showed that whole-tree thinning lead to a decrease in forest growth. The effect was present more or less immediately after thinning, and was still present after 25 years. The average reduction in growth was around 10 % after 25 years in the spruce stands, while in the pine stands a non-significant average growth reduction of 4 % was found. The results are generated under experimental conditions, and in practice a share of the residues is left on site, decreasing the nutrient loss.
Forfattere
Kjersti Holt HanssenSammendrag
De siste årene har det blitt rapportert om stedvis kraftige angrep av gransnutebiller i foryngelsesfelt i Norge. En undersøkelse ble utført på Vestlandet og i Trøndelag i 2009, og det var et ønske fra skognæring og -forvaltning å utføre en tilsvarende undersøkelse på Øst- og Sørlandet. Til sammen 142 foryngelsesfelt i fylkene Østfold, Akershus, Hedmark, Oppland, Buskerud, Vestfold, Telemark, Aust-Agder og Vest-Agder ble undersøkt høsten 2010. Disse var plantet til i 2009 eller 2010, og det hadde ikke gått mer enn to sesonger siden hogst ved tilplantingen. På hvert felt ble alle kulturplantene på 20 sirkelflater á 20 m2 undersøkt for snutebillegnag og andre skader, og vitaliteten ble bedømt i fire klasser. For hvert felt ble variabler som høyde over havet, flatestørrelse, jordfuktighet, helling, eksposisjon og plantetype registrert....
Sammendrag
Four Norway spruce stands treated with single tree selection were studied 11 years after the cuttings. In each of the stands we performed four strengths of cuttings in 0.2 ha plots, with removals ranging from zero to 70 % of the basal area. We investigated accumulated and annual growth, changes in stand structure, tree age and tree damage. 10-20 % of the living trees were still damaged 11 years after the cutting. The diameter distribution displayed a reverse J-curve in all plots both before and after the cuttings. Eleven years later, the curve is only slightly changed. Annual ring widths from 300 increment cores were analysed. Most trees started to increase the growth two or three years after the cutting. This improved growth accelerated the following six or seven years with 20-80 % increase. Both small and large trees reacted, including severely suppressed trees. The initial crown volume and crown vitality after cutting is essential for the increased growth since several years are necessary to build up a larger and better crown. A reduced volume per hectare provided an increased growth for each of the remaining trees and indicates less competition for nutrients and light after cutting. The observed growth during the 11-year post-harvest period was about 10 % less than the estimated yield capacity for even-aged stands.
Sammendrag
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Sammendrag
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Sammendrag
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Sammendrag
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Forfattere
Holger LangeSammendrag
In ecosystem research, data-driven approaches to modeling are of major importance. Models are more often than not shaped by the spatiotemporal structure of the observations: an inverse modeling approach prevails. Here, I investigate the insights obtained from Recurrence Quantification Analysis of observed ecosystem time series. As a typical example of available long-term monitoring data, I choose time series from hydrology and hydrochemistry. Besides providing insights into the nonstationary and nonlinear dynamics of these variables, RQA also enables a detailed and temporally local model-data comparison.