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.
1999
Sammendrag
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Forfattere
Espen Haugland R.J Froud-WilliamsSammendrag
1. In order to investigate the factors influencing the establishment of seedlings in permanent grassland, the influence of soil moisture and nitrogen fertilisation on competition between established Lolium perenne and seedlings of Phleum pratense or Trifolium pratense was studied in two experiments under greenhouse conditions using the `split-box"-technique. 2. There was no difference in the production of plant dry matter of P. pratense or T. pratense between 30 % volumetric soil water content (-0.005 MPa) and 22 % (-0.04 MPa), but 15 % soil moisture (-0.33 MPa) reduced plant growth. L. perenne yields were linearly reduced by reduced soil moisture content. 3. Shoot competition from L. perenne reduced the plant dry matter yield of P. pratense and T. pratense more than did root competition in these experiments. When shoot competition was present, differences between moisture contents were not detected, indicating that light was probably the limiting resource under such conditions. No significant interaction between root competition and soil moisture were observed for plant weight. 4. Root competition was not prevented even though sufficient water and nitrogen were supplied. This indicated either that some other growth factor was limiting or the plants competed for resources at the root hair level even though sufficient resources were supplied at the pot or field scale. Therefore, in the situation of direct drilling of species during grassland renovation, it may be difficult to alleviate competition by adequate provision of water and nitrogen.
Forfattere
O. Janne KjønaasSammendrag
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Forfattere
O. Janne KjønaasSammendrag
Mixed bed ion exchange resin bags have previously been used in studies of soil N transformation rates with NH4-N and NO3-N being adsorbed from the solution percolating through the incubated soil core. An evaluation of the in situ adsorption efficiency of mixed bed resin bags was performed by comparing dissolved inorganic nitrogen (DIN, sum of NH4-N NO3-N) accumulated in resins with DIN fluxes in throughfall (TF) and with DIN concentrations in soil water. A significant correlation was found between DIN fluxes in TF and accumulated DIN in resins placed at the soil surface (r2= 0.92 for NO3-N, r2=0.86 for NH4-N, p0.001). The ratio of accumulated DIN in resins to DIN flux in TF was significantly affected by season. A low but significant correlation was found between NO3-N concentrations in soil water and NO3-N contents in resins deployed in the bottom of soil cylinders (r2=0.34, p0.01), however, when only the winter periods were taken into account, the correlation improved (r2=0.72, p0.001). As little water and few nutrients are removed from the soil water by the vegetation during the dormant season, the conditions inside and outside the core were more comparable. For NH4-N there was no correlation between accumulated amounts in the resins and concentrations in soil water sampled at 13 cm and 20 cm depth, respectively, probably due to the strong depth gradient in the NH4-N concentrations of the soil. Although the resin bags were unable to adsorb all the incoming DIN, they gave valuable information on small scale input of N and small scale differences in NO3-N leaching.
Forfattere
A. FriesSammendrag
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Forfattere
Kari Anne Sølvernes Gunnar OgnerSammendrag
The impact of climate change on a mini forest ecosystem was studied for three years in an open-top chamber (OTC) experiment with an outside control plot. Clones of Silver birch (Betula pendula Roth.) and Norway spruce (Picea abies (L.) Karst) were grown in monolithic lysimeters containing undisturbed profiles of podsolic forest soil. The original understory was also present.The soil temperature was increased with 2-3 C. The atmospheric CO2 concentration in the OTCs was ambient (380mol mol-1 CO2), approximately 500 and 700 mol mol-1 CO2. The leachates from the lysimeters was collected, and the solute concentration was analysed monthly.Increased soil temperature increased the mineralisation of soil organic matter, and large amounts of nitrate, dissolved organic nitrogen (DON) and aluminium were released. In the leachates from the 500 mol mol-1 CO2 birch lysimeters, high concentrations of Al were recorded during the second and third growth seasons.The high concentrations of Al were correlated with high concentration of total organic carbon (TOC) and increased pH. Large amounts of Al was organically bound in these leachates. The origin of the organic ligands could have been products of the birch roots, e.g. root exudates.
Forfattere
Gunnar Ogner Kari Anne SølvernesSammendrag
The impact of elevated CO2 and increased temperature on the soil of a mini forest ecosystem was investigated in an open-top chamber experiment. The CO2 treatments of the OTCs were ambient, 500 and 700 mmol CO2 mol-1 with an ambient outdoor control. All soils were warmed by natural air flow and radiation to a temperature 2-3 C above a corresponding forest soil site. Overheating was prevented by a cooling system. Silver birch and Norway spruce were planted in undisturbed soil monolithic profiles, with their original understory, in lysimeters and compared to a lysimeter control with understory only. Soil samples were collected in the forest at the end of the experiment and used as reference samples. Increased temperature was found to cause the greatest effect on soil. All data clearly indicated increased breakdown of the soil organic matter with increased temperature. The breakdown of raw humus gave a decrease in concentration of total C, total N, and in the exchangeable plus extractable elements (org.-C, Ca, K, Mg, Mn, t-P and t-S) relative to the original forest reference soil in the range of 18 - 57 %. The exchangeable plus extractable elements (Al, Fe, Si, NH4-N and org.-N) from the raw humus layer increased in concentration relative to original forest soil by 28 - 96 %. The effect of different vegetation on soil quality was less than for the temperature increase. Birch had the strongest effect by decreasing soil acidity and the concentration of exchangeable Al throughout the soil profile relative to spruce. Birch also increased weathering of mineral soil relative to spruce. The effects of CO2 treatment on the soil were clearly smaller than for the temperature and vegetation parameters. Elevated CO2 gave increased concentrations of exchangeable plus extractable Zn, organic C and organic N for the raw humus layer of the understory and spruce vegetation relative to the raw humus of the birch lysimeters. Principal component analysis of the complete data set indicated an effect of elevated CO2 on the humus layer relative to the ambient treatments. This effect was seen most clearly in the lysimeters with understory vegetation.
Forfattere
Magne SætersdalSammendrag
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Forfattere
Toril Håkestad KristiansenSammendrag
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Sammendrag
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