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.
2006
Authors
Svein Solberg Erik Næsset Ole Martin BollandsåsAbstract
No abstract has been registered
Abstract
In this study, we present a new method for single tree segmentation and characterization from a canopy surface model (CSM), and its corresponding point cloud, based on airborne laser scanning. The method comprises new algorithms for controlling the shape of crown segments, and for residual adjustment of the canopy surface model (CSM). We present a new criterion that measures the success of locating trees, and demonstrate how this criterion can be used for optimizing the degree of CSM smoothing. From the adjusted CSM segments, we derived tree height and crown diameter, and based on all first laser pulse measurements within the segments we derived crown-base height. The method was applied and validated in a Norway spruce dominated forest reserve having a heterogeneous structure. The number of trees automatically detected varied with social status of the trees, from 93 percent of the dominant trees to 19 percent of the suppressed trees. The RMSE values for tree height, crown diameter, and crown-base height were around 1.2 m, 1.1 m, and 3.5 m, respectively. The method overestimated crown diameter (0.8 m) and crown base height (3.0 m).
Authors
Bed Mani Dahal Bishal K. Sitaula Roshan M. Bajracharya K. Atreya Alhaji JengAbstract
No abstract has been registered
Authors
Helge Lundekvam Lillian Øygarden Trond Børresen Arnold Arnoldussen John Boardman Jean PoesenAbstract
Soil erosion in Norway Abstract Soil erosion in Norway mainly occurs in autumn and winter period. High soil losses may occur by heavy snowmelt and/or rainfall in combination with frozen and not covered soil. Dominating erosion processes are sheet and rill erosion, deeper rilling caused by concentrated surface runoff, gullying and erosion in connection with tile drains. Research on tillage systems have been ongoing since the mid- seventies and the systems have been ranked according to their relative erosion risk. Soil losses are documented both in plot, field and at catchment scale and also in the National Agricultural Environmental Monitoring Programme (JOVA). The data have been used for the development of the Norwegian erosion risk model ERONOR and in several governmental actions involving subsidies and new regulations based on soil erosion risk maps using an USLE ?equation adapted to Norwegian conditions. Subsidies are given for tillage practice with low erosion risk, catch crops, grass covered waterways, buffer zones and sedimentation ponds. Soil losses (annual mean values) have been 0.1- 4.36 t ha-1 in plot studies, 0.028 ? 5.2 t ha-1 in field scale studies and 0.1- 3.5 t ha-1 in catchment studies. Soil losses by extreme gullying have exceeded 100 t ha-1.
Abstract
Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing conclusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability.
Authors
Kinga Adam Anne Kristine Søvik Tore KrogstadAbstract
Sorption of P to the filter material Filtralite-p (TM) was examined at a small, medium and large scale. in the small- and meso-scale laboratory models, the sorbed amount of total phosphorus (P) was heterogeneously distributed with more P sorbed in the inlet zone and the bottom layers. The full-scale system had, on the other hand, the highest sorbed concentration in the outlet region. The overall P sorption capacity of the material was 8030, 4990 and 521 mg P kg(-1) Filtralite-P (TM) for Box 1, Box 2 and meso scale, respectively This equals 4.4, 2.8 and 0.29 kg p m(-3) material, respectively However, the maximum sorption capacities found were 2500, 3887 and 4500 mg P kg(-1) Filtralite-P (TM) for the two small-scale box systems and the meso-scale container, respectively. in the full-scale system the overall P sorption capacity of the material was 52 mg P kg(-1) Filtralite-P (TM) (0.029 kg P m(-3) Filtralite-P (TM)) with a maximum sorbed amount of P of 249 mg P kg(-1). Results from both the small- and meso-scale system show that when a constructed wetland (CW) is saturated, i.e. when the outlet concentration has reached its maximum allowed concentration of 1.0 mg P l(-1), only parts of the filter material will have reached the sorption capacity. Sequential extractions of Filtralite-P (TM) showed that the loosely bound P, Ca-P and AI-P were the primary P sorption pools both in the small-scale models and in the full-scale CW However, the proportion of these three fractions varied with time and change in pH. A white product precipitated in the outlet zone of both the small-scale box models as well as the onsite CW The surface of these precipitation particles was identified by X-ray diffraction and SEM method as CaCO3 and precipitated Ca- and Mg-phosphates. (c) 2006 Elsevier Ltd. All rights reserved.
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No abstract has been registered
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No abstract has been registered
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No abstract has been registered
Authors
Michael M. Müller Kari KorhonenAbstract
No abstract has been registered