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.
2019
Authors
Fasil Eregno Arve HeistadAbstract
No abstract has been registered
Authors
Simone Russo Jana Sillmann Sebastian Sippel Monika J. Barcikowska Claudia Ghisetti Marek Smid Brian O'NeillAbstract
No abstract has been registered
Authors
Tomas Persson Mats Höglind Marcel van Oijen Panu Korhonen Taru Palosuo Guillaume Jégo Perttu Virkajärvi Gilles Bélanger Anne-Maj GustavssonAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Many nonlinear methods of time series analysis require a minimal number of observations in the hundreds to thousands, which is not always easy to achieve for observations of environmental systems. Eddy Covariance (EC) measurements of the carbon exchange between the atmosphere and vegetation provide a noticeable exception. They are taken at high temporal resolution, typically at 20 Hz. This generates very long time series (many millions of data points) even for short measurement periods, rendering finite size effects unimportant. In this presentation, we investigate high-resolution raw data of 3D wind speed, CO2 concentrations, water vapor and temperature measured at a young forest plantation in Southeast Norway since July 2018. Guiding for the analysis is the gain or added value of the high resolution compared to more aggregated data, i.e. the scaling behavior of nonlinear properties of the time series. We present results of complexity analysis, Tarnopolski diagrams, q-Entropy, Hurst analysis, Empirical Mode Decomposition and Singular System Analysis. This provides detailed insights into the nature of dynamics of carbon fluxes across this system boundary at different temporal scales.
Authors
J. William Allwood Tomasz Leszek Woznicki Yun Xu Alexandre Foito Kjersti Aaby Julie Sungurtas Sabine Freitag Royston Goodacre Derek Stewart Siv Fagertun Remberg Ola M Heide Anita SønstebyAbstract
No abstract has been registered
Authors
Kristi Parro Kajar Köster Kalev Jogiste Katrin Seglinš Allan Sims John A. Stanturf Marek MetslaidAbstract
Boreal forests are an important carbon (C) sink and fire is the main natural disturbance, directly affecting the Ccycle via emissions from combustion of biomass and organic matter and indirectly through long-term changes in C-dynamics including soil respiration. Carbon dioxide (CO2) emission from soil (soil respiration) is one of the largest fluxes in the global C-cycle. Recovery of vegetation, organic matter and soil respiration may be influenced by the intensity of post-fire management such as salvage logging. To study the impact of forest fire, fire and salvage, and recovery time on soil respiration and soil C and N content, we sampled two permanent research areas in north-western Estonia that were damaged by fire: Vihterpalu (59°13′ N 23°49′ E) in 1992 and Nõva (59°10′ N 23°45′ E) in 2008. Three types of sample plots were established: 1) unburned control with no harvesting (CO); 2) burned and uncleared (BU); and 3) burned and cleared (BC). Measurements were made in 2013, 21 years after wildfire in Vihterpalu and 5 years after wildfire in Nõva. Soil respiration ranged from 0.00 to 1.38 g CO2 m−2 h−1. Soil respiration in the burned and cleared areas (BC) was not reduced compared to burned and uncleared (BU) areas but the average soil respiration in unburned control areas was more than twice the value in burned areas (average soil respiration in CO areas was 0.34 CO2 m−2 h−1, versus 0.16 CO2 m−2 h−1, the average soil respiration of BC and BU combined). Recovery over 20 years was mixed; respiration was insignificantly lower on younger than older burned sites (when BC and BU values were combined, the average values were 0.15 vs. 0.17 g CO2 m−2 h−1, respectively); soil-C was greater in the older burned plots than the younger (when BC and BU values were combined, the average values were 9.71 vs. 5.99 kgm−2, respectively); but root biomass in older and recently burned areas was essentially the same (average 2.23 and 2.11 kgm−2, respectively); soil-N was highest on burned areas 20 years after fire. Twenty years post-fire may be insufficient time for carbon dynamics to fully recover on these low productivity sandy sites.
Abstract
Effects of mitigation measures in agriculture on abating eutrophication are difficult to evaluate by assessments of catchment monitoring data. Estimates of improved water quality by specific agricultural Best Management Practices (BMPs) are therefore often dependent on simulation modeling. A main objective was thus to assess the probable reductions in total phosphorus (TP) loading achieved by implemented agricultural mitigation measures. The case-study site was a catchment in southeastern Norway. Simulation modeling was conducted by use of The Soil and Water Assessment Tool (SWAT). The aim of this present study was to understand the model uncertainty associated both with calibration/validation (baseline) and TP loading scenarios based on BMP. The modeled decrease in TP loading by the set of implemented BMPs was assessed by comparing simulated baseline output with output where the set of abatement actions were removed. The model was set up for the years 2006–2010 and calibrated against observed monitoring data, including daily discharge, sediment- and TP fluxes. Model simulations were performed including and excluding the implemented set of mitigation measures. The simulated set of mitigation measures include decrease in amount of phosphorus fertilization, establishment of vegetated buffer strips along streams and constructed wetlands in the water courses, no autumn tilling and removal of point TP sources from scattered dwellings. Model calibration and uncertainty estimation are performed using an algorithm for Sequential Uncertainty Fitting (SUFI2; ver. 2). Probabilistic risk for given magnitudes of increased TP loading if existing BMPs were not implemented was assessed. Using this novel approach it was possible to state, with a 80th percentile confidence level, that the average annual TP loading would have been about 26% higher if no mitigation measures were implemented in the catchment. This was possible to assess even though the difference between baseline and BMP scenario was not significant.
Authors
Mekjell Meland Frank Maas Åge JørgensenAbstract
Sweet cherry production worldwide is grown in the open land. Production technique is more or less similar with scions grafted on dwarfing and semi-dwarfing rootstock and trees arranged in single rows. Sweet cherries can be grown in Norway in areas with suitable local climatic conditions up to 60°N. All orchards have high-density planting systems and are rain covered. Rain-induced fruit cracking in cherries remains a problem at an international level. The most common systems in Norway are multibay high tunnel systems and retractable rain covers. Covered orchard tunnel systems offer not only the advantage of rain exclusion but also allow additional manipulation of the environment, tree growth and fruiting. In general, sweet cherry high tunnel production gives increased yields of larger fruit than in the open land, but investment costs are higher. One more advanced way of producing sweet cherries is to grow the trees in small pots in greenhouses. A greenhouse gives opportunity to control the temperature regime and in that way program the maturity of the fruits. Research is conducted to test different cultivars, rootstocks, training methods in high-density production systems (1 tree m-2) with different fertigation levels. Preliminary results show that the yield potential is much higher than in the open land with larger fruits. Challenges are to optimize the water and nutrition supply and adjust the temperatures to obtain large yields of high quality fruits during different periods of the season.
Authors
Milica Fotiric Aksic B. Guffa U. Gasic D. Dabic Zagorac M. Natic Mekjell MelandAbstract
The presence of pollinators in orchards is crucial to obtain high fruit set and yields of fruits. Despite the fact that sour cherry cultivars are mainly autogamous, insect visits are still of great importance for their propagation. In order to attract and reward pollinators, flowers have to provide adequate nourishment to them. Besides nectar, bees gather pollen, which are a prerequisite for normal colony growth and development of their broods. ‘Oblačinska’ sour cherry (Prunus cerasus L.), an autochthonous cultivar, is the most highly planted cultivar in Serbian commercial orchards. Since the cultivar is actually a mixture of different clones, variability in numerous traits and, particularly, its yields has been reported. Since phenolic compounds are considered to be fundamental pollen chemicals, the aim of this study was to determine the phenolic compounds profile in pollen collected from 15 ‘Oblačinska’ sour cherry clones with varying productivity levels. Solid phase extraction (SPE), combined with ultra-high-performance liquid chromatography coupled with a diode array detector and a triple quadruple mass spectrometer (UHPLC DAD-MS/MS), was used to analyse the polyphenolic profile of pollen. Among 23 components quantified, rutin was the most abundant phenolic compound. It ranged from 98.49 (clone V/P) to 358.83 mg kg-1 (clone III/9) and was observed to contribute, on average, 56% of the total phenolic compounds in pollen as quantified in different ‘Oblačinska’ sour cherry clones. In addition to this compound, clones contained significant amounts of chlorogenic acid (12.92%), astragalin (8.19%), and hyperoside (5.59%) as well. Cluster analysis grouped pollen clones in four different clusters, which showed that clones III/9, IV/8, and V/P had unique phenolic profiles. Despite the significant differences among the studied clones, the contents of chlorogenic acid, rutin, naringin, hyperoside, astralgin, and phlorizin were distinguishable between the clusters.