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.
2013
Forfattere
Joachim Paul Spindelbøck Zöe Cook Matthew I. Daws Einar Heegaard Inger Elisabeth Måren Vigdis VandvikSammendrag
Background and Aims: Across their range, widely distributed species are exposed to a variety of climatic and other environmental conditions, and accordingly may display variation in life history strategies. For seed germination in cold climates, two contrasting responses to variation in winter temperature have been documented: first, an increased ability to germinate at low temperatures (cold tolerance) as winter temperatures decrease, and secondly a reduced ability to germinate at low temperatures (cold avoidance) that concentrates germination towards the warmer parts of the season. Methods: Germination responses were tested for Calluna vulgaris, the dominant species of European heathlands, from ten populations collected along broad-scale bioclimatic gradients (latitude, altitude) in Norway, covering a substantial fraction of the species' climatic range. Incubation treatments varied from 10 to 25 °C, and germination performance across populations was analysed in relation to temperature conditions at the seed collection locations. Key Results: Seeds from all populations germinated rapidly and to high final percentages under the warmer incubation temperatures. Under low incubation temperatures, cold-climate populations had significantly lower germination rates and percentages than warm-climate populations. While germination rates and percentages also increased with seed mass, seed mass did not vary along the climatic gradients, and therefore did not explain the variation in germination responses. Conclusions: Variation in germination responses among Calluna populations was consistent with increased temperature requirements for germination towards colder climates, indicating a cold-avoidance germination strategy conditional on the temperature at the seeds' origin. Along a gradient of increasing temperatures this suggests a shift in selection pressures on germination from climatic adversity (i.e. low temperatures and potential frost risk in early or late season) to competitive performance and better exploitation of the entire growing season.
Sammendrag
Det er ikke registrert sammendrag
Sammendrag
When calculating the Bandt and Pompe ordinal pattern distribution from given time series at depth D, some of the D! patterns might not appear. This could be a pure finite size effect (missing patterns) or due to dynamical properties of the observed system (forbidden patterns). For pure noise, no forbidden patterns occur, contrary to deterministic chaotic maps. We investigate long time series of river runoff for missing patterns and calculate two global properties of their pattern distributions: the Permutation Entropy and the Permutation Statistical Complexity. This is compared to purely stochastic but long-range correlated processes, the k-noise (noise with power spectrum f−k), where k is a parameter determining the strength of the correlations. Although these processes closely resemble runoff series in their correlation behavior, the ordinal pattern statistics reveals qualitative differences, which can be phrased in terms of missing patterns behavior or the temporal asymmetry of the observed series. For the latter, an index is developed in the paper, which may be used to quantify the asymmetry of natural processes as opposed to artificially generated data.
Sammendrag
An 11-year remotely sensed surface albedo dataset coupled with historical meteorological and stand-level forest management data for a variety of stands in Norway’s most productive logging region is used to develop regression models describing temporal changes in forest albedo following clear-cut harvest disturbance events. Datasets are grouped by dominant tree species, and two alternate multiple regression models are developed and tested following a potential-modifier approach. This result in models with statistically significant parameters (p < 0.05) that explain a large proportion of the observed variation, requiring a single canopy modifier predictor coupled with either monthly or annual mean air temperature as a predictor of a stand’s potential albedo. Models based on annual mean temperature predict annual albedo with errors (RMSE) in the range of 0.025–0.027, while models based on monthly mean temperature predict monthly albedo with errors ranging between of 0.057–0.065 depending on the dominant tree species. While both models have the potential to be transferable to other boreal regions with similar forest management regimes, further validation efforts are required. As active management of boreal forests is increasingly seen as a means to mitigate climate change, the presented models can be used with routine forest inventory and meteorological data to predict albedo evolution in managed forests throughout the region, which, together with carbon cycle modeling, can lead to more holistic climate impact assessments of alternative forest harvest scenarios and forest product systems.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Kathrin Seidel Johannes Kahl Flavio Paoletti Inés Birlouez-Aragone Nicolaas Busscher Ursula Kretzschmar Marjo Särkka-Tirkkonen Randi Seljåsen Fiorella Sinesio Torfinn Torp Irene BaiamonteSammendrag
Det er ikke registrert sammendrag
Sammendrag
Seasonal time-courses of flower bud initiation and differentiation were monitored during two growing seasons (2011 and 2012) in 19 black currant cultivars of distant geographic origin, grown in the field at a South Norwegian locality (60°40’N, 10°52’E; 250 m asl). For comparison, the time-courses of shoot elongation growth in 15 of the same cultivars were also monitored during the 2012 growing season.The results revealed widely different seasonal timings of growth cessation and floral initiation in cultivars of different latitudinal origin. High latitude cultivars originating from crosses and selections of local, wild black currant populations from the Kola peninsula and Swedish Lapland were particularly early and had ceased growing and had initiated floral primordia by mid-June.This was approx. 5 – 6 weeks earlier than any of the other cultivars from lower latitudes. However, these also varied in their earliness of growth cessation and flower initiation in relation to their latitudinal origin. Many cultivars bred and selected in Southern Scandinavia, Scotland, and Poland did not cease growing and initiate floral primordia until late August, 9 weeks after the early, highlatitude cultivars. Overall, the 19 cultivars constituted a typical latitudinal cline in their photoperiodically controlled timing of growth and flowering responses. The high-latitude Russian cultivars ‘Imandra’ and ‘Murmanschanka’ represent valuable additions to the limited diversity of the available black currant gene-pool, and may be of particular use for breeding cultivars adapted to the sub-Arctic environment.
Forfattere
Jan Světlík Isabella Børja Sabine Rosner Jan Čermák Valeriy Nadezhdin Nadezhda NadezhdinaSammendrag
In cases where sap flow is measured in trees and cross-sectional sapwood is not uniformly distributed, as in stems of diseased trees, an additional method may refine the sap flow measurements. If the studied trees are felled, the modified differential translucence method (MDT) for quantifying sapwood distribution in cross-sectional area may be compared with sap flow measurements. We studied sap flow by the heat field deformation method (HFD) in 12 Norway spruce trees with visible dieback symptoms and 12 without symptoms. Later, all sample trees were felled and analysed by MDT method. Results from MDT described well the differences and abnormalities which were also detected by HFD at any depth of the sapwood. Sap flow for whole tree (SF1) was calculated in accordance with radial and circumferential variation of sap flow density detected by HFD (based on average sap flow radial profiles). Other sapwood disturbances in parts not covered by HFD measurements were later corrected by MDT and refined total sap flow (SF2) was calculated. Relative differences between SF1and SF2 reached an interval from -0.21 to 0.41 for symptomatic trees and from -0.15 to 0.29 for non-symptomatic trees. The majority of the non-symptomatic trees had the relative difference close to zero. The theoretical use of single-point sensors for sap flow measurement was compared with the proportions of three wood types in a line 2 cm below the vascular cambium (a-sapwood, b-borders sapwood/heartwood or embolism, c-heartwood or embolism). The variability across wood types in the chosen line in the symptomatic trees was high and therefore quantifying the sap flow by the single point method was not possible.
Sammendrag
Originally, Trypophloeus dejevi (Stark, 1936) was described from Sakhalin Island in the Far East of Russia, and it remained undetected in Europe until 2009, when one Swedish specimen was found in the collection of the late Lars Huggert. This specimen was sampled in Northern Sweden in Torne Lappmark: Årosjokk, 67°52’ N/19°22’E, in 1968. In 2010, the species was found in five new localities in the same area. Here we present T. dejevi, recorded in 2012 as a new species to Norway and Finland. In Norway, galleries with beetles were found in Salix myrsinifolia Salisbury and in Finland Salix glauca L. was the observed host tree. Both are common willow species in Northern Fennoscandia. The distribution of the beetle within trunks of living Salix combined with a low population-density may be an explanation to why T. dejevi has been overlooked until now.
Sammendrag
Information on tree species effects on soil organic carbon (SOC) stocks is scattered and there have been few attempts to synthesize results for forest floor and mineral soil C pools. We reviewed and synthesized current knowledge of tree species effects on SOC stocks in temperate and boreal forests based on common garden, retrospective paired stand and retrospective single-tree studies. There was evidence of consistent tree species effects on SOC stocks. Effects were clearest for forest floor C stocks (23 of 24 studies) with consistent differences for tree genera common to European and North American temperate and boreal forests. Support for generalization of tree species effects on mineral soil C stocks was more limited, but significant effects were found in 13 of 22 studies that measured mineral soil C. Proportional differences in forest floor and mineral soil C stocks among tree species suggested that C stocks can be increased by 200–500% in forest floors and by 40–50% in top mineral soil by tree species change. However, these proportional differences within forest floors and mineral soils are not always additive: the C distribution between forest floor and mineral soil rather than total C stock tends to differ among tree species within temperate forests. This suggests that some species may be better engineers for sequestration of C in stable form in the mineral soil, but it is unclear whether the key mechanism is root litter input or macrofauna activity. Tree species effects on SOC in targeted experiments were most consistent with results from large-scale inventories for forest floor C stocks whereas mineral soil C stocks appeared to be stronger influenced by soil type or climate than by tree species at regional or national scales. Although little studied, there are indications that higher tree species diversity could lead to higher SOC stocks but the role of tree species diversity per se vs. species identity effects needs to be disentangled in rigorous experimental designs. For targeted use of tree species to sequester soil C we must identify the processes related to C input and output, particularly belowground, that control SOC stock differences. We should also study forms and stability of C along with bulk C stocks to assess whether certain broadleaves store C in more stable form. Joint cooperation is needed to support syntheses and process-oriented work on tree species and SOC, e.g. through an international network of common garden experiments.