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.
1999
Authors
Per Holm NygaardAbstract
This thesis deals with effects of acidification, fertilisation and addition of Al on boreal vegetation as studied in different field- and laboratory experiments. The results are discussed in relation to the natural vegetation dynamics and critical loads of S and N for forest soils. Field experiments with artificial acid rain caused damage to bryophytes like Pleurozium schreberi and Dicranum polysetum at pH 2.5 and pH 3.0. The presence of Melampyrum pratense was reduced when treated with pH 2.5 and pH 3.0. For the pH 2.5 treatment, a decreased leaf production and decreased internal Mg concentration of Vaccinium myrtillus leaves were recorded. Treatment with pH 2.5 and 3.0 resulted in decreased base saturation in the O and E horizons, in particular Mg2, which may explain the effects on V. myrtillus. Repeated N-fertiliser additions caused vegetation changes, particularly at higher doses (1500 kg N/ha).An increase in cover of the species Deschampsia flexuosa, Molinia caerulea, Agrostis capillaris, Carex canescens, Rubus idaeus, Epilobum angustifolium and Dryopteris assimilis were found 8 years after the last N-application. Chemical analysis of leaves of V. myrtillus demonstrated an increase in N and a decrease in P concentrations on the fertilised plots compared to controls.The concentration of exchangeable Ca2, Mg2and K in the humus layer were reduced in fertilised plots compared to control plots. No differences in pH(H2O) or exchangeable acidity in the humus layer were found between fertilised plots and control plots. Laboratory experiments with Mg-limited Norway spruce seedlings showed that 80 M Al3 and a constant molar Ca/Al ratio of 0.2 decreased the uptake of Ca2 and Mg2, and reduced root length growth. However, no indication of an ameliorating effect of K on Al were seen, therefore these experiments give no support for including K into the critical load criterion. In the critical load calculation it seems that the molar Ca/Al ratio has been emphasised too much, and in particular that the scientific evidence of the critical chemical value (Ca/Al=1) is not well documented. A lot of the processes going on in the forest ecosystem are oversimplified or even left out in the present calculations. Long-term monitoring of forest vegetation at Karlshaugen, under moderate deposition regime of S and N, showed that other processes than deposition of S and N determine the vegetation dynamics, in particular the development of the dominant canopy species and field layer species seems to be much more important because of their influence on light and nutrients. Reduced frequency and persistence were shown for many field layer species and cryptogames during a 60 years period. A comparison of pH in soilwater from O-layer between 1961 and 1991 showed an increase in median pH of 0.1 pH unit for the area
Authors
Celine Rebours Chantal Billard Anne Marie Rusig Joel CossonAbstract
No abstract has been registered
Authors
O. Janne Kjønaas Anne Camilla Bergkvist Arne Olav StuanesAbstract
No abstract has been registered
Authors
Tonje Økland Rune Halvorsen Økland Eiliv SteinnesAbstract
No abstract has been registered
Authors
Svein Ole BorgenAbstract
No abstract has been registered
Authors
Svein Ole BorgenAbstract
No abstract has been registered
Authors
Per Ivar Våje Bal Ram Singh Rattan LalAbstract
Nitrogen and water are both major limiting factors for agronomic production in Africa. The effect of erosion on the availability of N and water for plants is not known for major soils of the tropics. Therefore, a study was conducted to assess erosional effects on N- and water-balance on a Mollic Andosol of 9-17% slope at Lyamungu Agricultural Research and Training Institute (ARTI), Kilimanjaro region, Tanzania. Soil erosion phases were established on the bases of the topsoil depth (TSD) as an indicator of previous erosion: <1 cm; severely eroded, 16-25 cm; moderately eroded and 26-35 cm; slightly eroded. Fill-in lysimeters (80 cm diameter, 80 cm deep) and field runoff plots (4x10 m) were used to monitor evapotranspiration (ET) and seepage, and N losses through erosion, runoff leaching and plant uptake. Maize (Zea mays var. Kilima) was planted in lysimeters and runoff-plots over two cropping seasons (1995 and 1996). Rainfall and evaporation (E) were measured daily. Sediment samples from runoff plots were analysed for total N, P and C, and water samples from leachate, runoff, and
Authors
O. Janne KjønaasAbstract
No abstract has been registered
Authors
O. Janne KjønaasAbstract
Mixtures of cation and anion exchange resins are used as part of the resin core technique to determine nitrogen transformation in forest soils as they adsorb the NH4-N and NO3-N from soil solution percolating through the incubated soil cores. In the field, the exchange resins may be subjected to a variety of conditions, involving drying, rehydration, freezing, and thawing. This paper examines how these processes affect adsorption of NH4-N and NO3-N and the stability of the resins. Lab tests were performed on the anion resin Amberlite IRA-93, the cationresin Amberlite IR-120, and a mixture of IRA-93 and IR-120, and the commercially-mixed bed resin Amberlite MB1. The background content of NO3-N and NH4-N on the resins was large and highly variable between different batches of resins in spite of a 2 M NaCl pre-rinse. The IR-120 cation resin that was subjected to 48 hours air-drying contained significantly less NH4-N than the most resins, while the drying of the IRA-93 anion resin caused a significant release of NO3-N from resins with no N addition. Although the variation was large, the mixed bed resin MB1 indicated a release of NH4-N, which supports results from long term in situ deployments. A reduced adsorption of NO3-N was found on the IRA-93 anion resins and the MB1 mixed bed resins that were dried prior to N addition while the dry IR-120 cation resins adsorbed significantly less NH4-N than the control resin. No effect of freezing the thawing efficiency was observed on resin stability or N adsorption efficiency. Sufficient blanks that have been subjected to similar moisture changes are necessary in N limited systems with low levels of avialable NH4-N and NO3-N.
Authors
Mehreteab TesfaiAbstract
No abstract has been registered