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.
2010
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Today the spruce bark beetle Ips typographus is always univoltine in Northern Europe including Norway and completes development from egg to adult between May and August. Further south in Europe, development is bivoltine with the completion of two generations in most years. A temperature-driven developmental model suggests that by 2070-2100 the voltinism of I. typographus will change dramatically in Norway. If summers become only 2.5°C warmer than today bivoltinism can be expected every single year in the major spruce growing areas in S-Norway. This is likely to have dramatic effects on forestry since two generations per year will give two, instead of one, attack periods each summer. In addition to increasing the number of attacked trees the effect of the attacks may also be more severe, as Norway spruce is more susceptible to beetle attacks later in the summer. However, climate change will probably also change the phenology of Norway spruce and thus its susceptibility to attack by I. typographus and its phytopathogenic fungal associates. We are currently modelling how tree resistance varies with temperature and tree phenology in order to provide more well-founded advice to forest managers on the interaction between bark beetles and tree in a future climate.
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We have recently found that Norway spruce (Picea abies (L.) Karst.) can rapidly adjust its adaptive performance, probably through an epigenetic mechanism. This appears to employ a kind of long-term memory of temperature sum and (probably) photoperiod from the time of its embryo development. In our research we made identical controlled crosses and produced seed lots under controlled temperature and day-length conditions and later observed phenology, growth and hardiness traits in the progenies. It was repeatedly found that temperature conditions during seed set, in particular, influence the phenotypes of the offspring; seedlings from seeds produced under warm conditions have later terminal bud set and reduced autumn frost hardiness than those from seed produced under colder conditions, and thus perform like a more southern provenance. When embryonic clones were derived from mature zygotic embryos and were cultured at different temperatures, the plants cultured under warm in vitro temperature were the last to set bud and grew taller than those cultured at lower temperatures. Progenies produced in Norway by Central European mother trees had a bud set curve skewed towards that of the local Norwegian performance. A comparison of the performance of seedlings from seeds collected in the same provenance regions in 1970 and 2006 shows that the more recent seed lots consistently produce taller seedlings with a later bud set, probably due to higher temperatures during seed production in 2006. The effect of reproductive environment has been shown to persist for years. It mimics the variation between provenances from different latitudes and altitudes and may explain much of the observed variability in bud set and early height growth between natural populations of Norway spruce. The observed phenomenon suggests an epigenetic mechanism in the developing embryo, either zygotic or somatic, that senses environmental signals such as temperature and influences adaptive traits. Research is underway to understand the molecular basis of this mechanism. We will discuss the implications of this epigenetic phenomenon for the interpretation of provenance differences, for tree breeding and for its possible role in adaptation to climate change.
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We monitored the effects of the drought stress on 20-year old clones of Norway spruce (Picea abies) by using a range of instrumental methods. On two experimental plots (Hoxmark, Norway, 59°40\"14`N, 10°47\"36`E) the drought was induced in a period between May and October 2009 by removing the throughfall using the rain shelters and trenching. We collected data on soil moisture, stem and branch sap flow, xylem diameter, anatomical and calorimetric analysis of the needles, fine root biomass and dynamics and resistance to pathogens. Standard meteorological data were collected locally throughout the whole period. Here we present the preliminary analysis of sap flow and xylem diameter in a period 1-17 august 2009. The sap flow was measured on stems in the breast height by using the method of stem tissue heat balance (THB, EMS Brno). The values were measured once in 2 minutes and saved as the average of 10 minutes. The fluctuations in xylem diameter was monitored by using the automatic dendrometers DR26 (EMS Brno). We evaluated both diurnal and seasonal dynamics. Preliminary results show a significant difference in shape of diurnal curves of transpiration as well as different time lag among the sap flow and the potential evapo-transpiration. Also the differences in diurnal dynamics of the stem circumference suggested different xylem water potential in stressed and control trees. In the drought-stressed trees the diurnal fluctuation in stem diameter was about 4 times higher and the total stem increment one third lower, com-pared to the control trees.
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