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.
2007
Authors
Zhihui Yang Bal Ram Singh Sissel Hansen Zhengyi Hu Hugh RileyAbstract
Understanding soil sulfur pools and associated aggregates S fractions can provide a platform for monitoring S dynamics in soils. A long-term experiment established in 1922 on an Aquic Eutrocryepts in South-eastern Norway was chosen to investigate the effects of long-term fertilization on S fractions in bulk soil and those associated with aggregates. Chloroform fumigation-extraction was used to determine Microbial biomass S (MBS) and the wet chemical analysis method was used to fractionate soil S into ester S (hydriodic acid reducible S), carbon-bonded S (Raney nickel reducible S) and residual S (Raney nickel non-reducible S). High farmyard manure (FYM) application resulted in higher MBS in bulk soil than nitrogen + potassium (NK) application, but it did not differ significantly from the control. Application of FYM at 60 Mg ha(-1) resulted into accumulation of total S, total organic S and carbon-bonded Sin bulk soils, while mineral fertilizer (nitrogen+phosphorus+potassium+sulfur [NPKS] and NK) and the medium rate of FYM did not increase the accumulation of total S and organic S fractions. The macroaggregate sizes (> 2 and 1-2 mm) and the finest aggregate size (< 0.106 mm) showed significantly greater total S concentration than other aggregate sizes. Ester S and residual S were predominant organic S fractions and they accounted for 39 to 52% and 38 to 51% of the organic S, respectively. The macroaggregate sizes (> 2 and 1-2 mm) contained the highest ester S, but microaggregates (< 0.106 mm) exhibited higher carbon-bonded S and residual S than other aggregates. In conclusion, the accumulation of S was dependent on fertilizer type, the rate of FYM application and aggregate sizes.
Abstract
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Abstract
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Authors
Zhihui Yang Bal Ram Singh Sissel HansenAbstract
Farmyard manure (FYM) and fertilizer applications are important management practices used to improve nutrient status and organic matter in soils and thus to increase crop productivity and carbon (C) sequestration. However, the long-term effects of fertilization on C, nitrogen (N) and sulfur (S) associated with aggregates, especially on S are not fully understood. We investigated the effects of more than 80 years of FYM (medium level of 40 Mg ka(-1) and high level of 60 Mg ka(-1)) and mineral fertilizer (NPKS and NK) on the concentrations and pools of C, N, and S and on their ratios in bulk soil, dry aggregates and water stable aggregates on an Aquic Eutrocryepts soil in South-eastern Norway. A high level of FYM and NPKS application increased the proportion of small dry aggregates (<0.6 mm) by 8%, compared with the control (without fertilizer). However, both medium and high level of FYM application increased the proportion of large water stable aggregates (>2 mm) compared with mineral fertilizer (NPKS and NK). The total C and N pools in bulk soils were also increased in FYM treatments but no such increase was seen with mineral fertilizer treatments. The increased total S pool was only found under high level of FYM application. Water stable macroaggregates (>2 and 1-2 mm) and microaggregates (<0. 106 mm) contained higher concentrations of C, N and S than the other aggregate sizes, but due to their abundance, medium size water stable aggregates (0.5-1 mm) contained higher total pools of all three elements. High level of FYM application increased the C concentration in water stable aggregates >2, 0.5-1 and <0. 106 mm, and increased the S concentration in most aggregates as compared with unfertilized soils. Higher ON, C/S and N/S ratios were found both in large dry aggregates (>20 and 6-20 mm) and in the smallest aggregates (<0.6 mm) than in other aggregate sizes. In water stable aggregates, the C/N ratio generally increased with decreasing aggregate size. However, macroaggregates (>2 mm) showed higher N/S ratios than microaggregates (<0. 106 mm). We can thus conclude, that long-term application of high amounts of FYM resulted in C, N and S accumulation in bulk soil, and C and S accumulation in most aggregates, but that the accumulation pattern was dependent on aggregate size and the element (C, N and S) considered.(C) 2007 Published by Elsevier B.V.
Authors
Sigrun H. Kværnø Lars Egil Haugen Trond BørresenAbstract
The ability to predict the timing of optimum soil workability depends on knowledge of the extent and structure of variability in main physical characteristics of the soil. Our objectives were to quantify the variability in texture and carbon content within soil map units in a small agriculture-dominated catchment in South-east Norway and to assess implications of variability in texture and carbon content on land management operations, using the predicted maximum water content for optimum workability as an example. Information from three different sources were used: a soil map (1:5000), a large sample grid (100 m spacing, 270 ha extent), and a small sample grid (10 m spacing, 2.25 ha extent). Readily available information on texture and organic matter content from the soil map was found to be of limited use for soil management due to broad textural classes together with deviations from the mapped main textural classes. There were significant differences in clay, silt and sand content between the different soil textural classes on the soil map. Statistical distributions within soil map units were generally either positively or negatively skewed and the coefficient of variation was intermediate, 15-50%. Most of the variation in both grids was spatially correlated. The large grid was dominated by a patchy structure, whilst the small grid showed a systematic trend with a gradual transition indicating fuzzy boundaries between map units in this catchment. The effective range for texture was 16 times larger in the large grid. Implications of variability in texture and carbon content on land management operations were assessed for the maximum water content for optimum workability (Wopt), predicted using pedotransfer functions. Wopt was usually in the same range as the water content at-100 kPa matric potential, indicating that considerable evaporation in addition to drainage is required for obtaining workable conditions in the field. The time required for obtaining the water content was estimated to about 5 days, which is longer than an average length of periods without precipitation in the area, median 3.7 days. Wopt predicted from the soil map deviated strongly from Wopt predicted from the sample grids. Comparing estimates of Wopt from the large grid with measurements in the small grid showed differences corresponding to +/-2-3 days of evaporation. (C) 2007 Elsevier B.V. All rights reserved.
Authors
Anita Sønsteby Ola M. HeideAbstract
Perpetual-flowering strawberry cultivars are commonly classified as photoperiodically day-neutral, even though early investigations demonstrated long-day (LD) regulation. An important reason for this inconsistency is that these freely flowering plants are difficult to establish in a true vegetative state, and experiments have therefore often been started using runner plants with pre-formed inflorescences. In order to circumvent this problem, we have used the perpetual-flowering F-1-hybrid 'Elan' that. is propagated by seed, and is thus not pre-conditioned by its earlier life history. The results demonstrated a marked quantitative LD response across a range of temperatures from 9 degrees - 27 degrees C. Seedlings were responsive to the LD stimulus at an early stage, and early flowering required LD exposure almost from germination. The critical daylength for the early flowering response was about 15 h at 18 degrees C. Because of this threshold LD response, it is concluded that regulation of flowering is truly photoperiodic in nature, and not merely an effect of additional light. Flower development was also slightly advanced by LD conditions. Stolon formation was strongly enhanced by short-day conditions in combination with high temperature. Thus, not only flowering, but also runnering, was oppositely affected by photoperiod in 'Elan' compared with mono-flowering cultivars. The results are discussed in relation to the photoperiodic classification of strawberries.
Abstract
Floral induction and development requirements of a range of latitudinal and altitudinal Norwegian populations of the wild strawberry Fragaria vesca L. have been studied in controlled environments. Rooted runner plants were exposed to a range of photoperiods and temperatures for 5 weeks for floral induction and then transferred to long day (LD) at 20 degrees C for flower development. A pronounced interaction of temperature and photoperiod was shown in the control of flowering. At 9 degrees C, flowers were initiated in both short day (SD) and LD conditions, at 15 and 18 degrees C in SD only, whereas no initiation took place at 21 degrees C regardless of daylength conditions. The critical photoperiod for SD floral induction was about 16 h and 14 h at 15 and 18 degrees C, respectively, the induction being incomplete at 18 degrees C. The optimal condition for floral induction was SD at 15 degrees C. A minimum of 4 weeks of exposure to such optimal conditions was required. Although the populations varied significantly in their flowering performance, no clinal relationship was present between latitude of origin and critical photoperiod. Flower development of SD-induced plants was only marginally advanced by LD conditions, while inflorescence elongation and runnering were strongly enhanced by LD at this stage. The main shift in these responses took place at photoperiods between 16 and 17 h. Unlike all other populations studied, a high-latitude population from 70 degrees N ('Alta') had an obligatory vernalization requirement. Although flowering and fruiting in its native Subarctic environment and after overwintering in the field in south Norway, this population did not flower in the laboratory in the absence of vernalization, even with 10 or 15 weeks of exposure to SD at 9 degrees C. Flowering performance in the field likewise indicated a vernalization requirement of this high-latitude population.
Authors
Svein Solberg Erik NæssetAbstract
The aim of this article is to present a concept of using airborne laser scanning (LIDAR), with one scan only, to map defoliation as a forest health variable. The idea is to apply two independent algorithms on the LIDAR data set, to produce both actual and expected leaf area index (LAI) values for every cell in a grid over the area. LAI is estimated based on laser pulse penetration through the canopy layer, and expected LAI values are derived from stand density based on position and height of single trees as obtained from a single-tree segmentation algorithm. The results are preliminary findings from four ongoing and related studies. In the first study repeated laser scans had close to equal extinction coefficients for LAI estimation although the instruments and flight specifications were different. In the second study, based on the findings in the first we derived normal LAI values from extisting and large scale data sets with LIDAR and field data. The main independent variable was stand density, defined as the ratio between mean tree height and mean distance between the trees. The ratio between LAI and stand density was around 0.5, and this is a preliminary standard for a healthy pine forest. In a third study the woody area fraction of LAI was estimated from 14 total harvested trees, and turned out to be slightly below 50% for a healthy pine tree, which means that a totally defoliated pine forest would have an LAI/stand density ratio around 0.2. In the fourth study, these LAI standard values were confirmed with LIDAR data from a severe insect defoliation event in Norway 2005. In conclusion, the present preliminary results demonstrate a potential for application of airborne laser scanning for monitoring or mapping of defoliation as a forest health variable.
Abstract
Capercaillie Tetrao urogallus leks have repeatedly been reported to be located in old forest. However, two conditions may have biased this widely held view. First, leks are known to be continuously used over several decades, and therefore might have been established when forest stands were younger. Second, stand -replacement logging (clearcutting) was not widely applied until the 1950s, leaving even-aged regenerating stands too young for leks to have been established in the latter part of the 20th century. Here we report eight cases of lek formation in young plantations from south-central Norway. Stand age ranged within 2646 years when display activity started. At six of the sites, we confirmed that females were regularly feeding on pine trees in winter prior to lek establishment, and at four of these sites displaying males were observed courting the females in late winter. These findings support the hotspot model of lek formation put forward by Gjerde et al. (2000), and it offers promising options for managing capercaillie leks in commercially utilised forests.
Authors
Susanne Eich-Greatorex Trine A Sogn Anne Falk Øgaard Ivar AasenAbstract
The objective of the present study was to investigate the influence of soil organic matter content and pH on plant availability of both inorganic and organic selenium (Se) fertilisers. Further, the risk of Se leaching after application of inorganic Se fertiliser was evaluated. A new interpretation of an older field study at different sites in Southern Norway showed that organic C was correlated with grain Se concentration in wheat, barley and oats, explaining up to 60% of the variation in Se concentration. Pot experiments with a peat soil, a loam soil and a peat/loam soil mixture were conducted for the present study at a range of pH values between pH 5 and 7. Below pH 6, Se uptake from added Se fertiliser was higher in the soil types with high organic matter content than in the loam. The opposite occurred at a soil pH above 6, where Se uptake was higher in the loam than in the peat soil. A simple leaching experiment after one growing season confirmed the findings of the pot experiments that Se availability in the loam soil with a relatively low organic matter content increased with increasing pH, whereas it decreased in the peat soil. Neither Se yeast, nor pure Se methionine, used as organic Se fertiliser, resulted in any significant uptake of Se when added at concentrations similar to the inorganic Se applications.