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.
1998
Forfattere
Martin Weih P. Staffan Karlsson Oddvar SkreSammendrag
Intra-specific relationships between growth traits and nitrogen economy were studied for seedlings of mountain birch (Betula pubescens ssp. tortuosa) originating from three climatically different regions within the northern forest margin in subarctic Fennoscandia. The experiment was carried out using potted seedlings grown in Abisko, northern Sweden, through two complete growing seasons. The seedlings were grown in peat and assigned to two different temperature and fertilization treatments according to a factorial design. The treatments were ambient and ca. 2.5oC elevated temperature (passive greenhouse), and soil nutrient fertilization corresponding to 1 and 10 g nitrogen m-2 season-1. Significant differences among provenances were found in almost all growth and nitrogen economy traits studied. The differences in growth rate, which reached 47%, were explained primarily by leaf weight ratio (biomass allocation to leaves) and secondly by leaf area productivity (biomass production per unit leaf area). Both the nitrogen productivity and residence time of nitrogen (with respect to above-ground nitrogen losses) varied between provenances; no significant relationship was found between these two traits. Differences in residence time of nitrogen were more related to biomass loss ratio (leaf biomass losses per unit total plant biomass production) than to nitrogen concentration of abscised leaves. The intra-specific variation in nitrogen economy between mountain birch provenances is discussed with respect to the possibility of significant genotype x environment interaction.
Forfattere
Arne Olav Stuanes O. Janne KjønaasSammendrag
Nitrogen has been added to a forested 0.52 ha headwater catchment (G2 NITREX) at Grdsjn, Sweden, to study the ecosystem response to elevated N deposition. The catchment is dominated by naturally regenerated, mixed-age conifers, mainly Norway spruce, with Scots pine dominating in dry areas. After a pre-treatment period of about 1 yr of soil solution sampling, N was added to the whole catchment as an NH4NO3 solution by means of sprinklers. Total N input as throughfall to the catchment increased from the ambient 13 kg N ha-1 yr-1 in the pre-treatment year to a total of about 50 kg N ha-1 yr-1 in the 4 treatment years. Soil solution was collected by tension lysimeters at 4 locations in G2 NITREX covering a moisture gradient from the dry upper to the lower wet parts of the catchment, at 2 locations in a nearby control catchment (F1 CONTROL), and at 2 locations in an adjacent catchment (G1 ROOF) at which ambient throughfall is excluded by a roof and replaced by unpolluted throughfall added by sprinklers. After 4 yr of N addition, the volume-weighted average NO3 concentrations in G2 NITREX were higher than the pre-treatment values. Concentrations showed a progressive increase over time. In the 2 first treatment years this increase occurred only in the rooting zone but during the second 2 treatment years a pronounced increase also came in deeper layers. The lack of these trends in the F1 CONTROL and G1 ROOF catchments precludes natural variations in climatic conditions as the main cause for this increase. Relative to inputs, NO3 concentrations in soil solution were low and showed large variations between the drier and wetter locations with peak concentrations in late fall and spring. Nitrate in soil solution generally constitutes less than 10% of the inorganic mobile anions and thereby contributes much less to the leaching of H, Al, and base cations than CI and SO4, the dominant mobile anions. Soil solution NH4 has not changed relative to the control and roof catchments. However, the system is changing. Increases in NO3 leaching indicate reduced immobilization of NO3 that can be due to episodic excess N supply of the microflora together with episodes of high waterflow.
Forfattere
Jan-Ole SkageSammendrag
Foredraget gir en orientering om NISK-Bergens forsøksvirksomhet med treslag og provenienser til produskjon av juletrær i Trøndelag. De fleste forsøkene med treslag og provenienser har som formål å bedre plantematerialet innen arter som dyrkes til juletrær. Dette gjøres ved å velge ut materiale med egenskaper som har betydning for treets utseende, som for eksempel jevnhet, retthet, vidde, høyde og farge
Forfattere
Fred Midtgaard B.A. Rukke Anne Sverdrup-ThygesonSammendrag
Habitat use of Bolitophagus reticulatus (L.) (Coleoptera: Tenebrionidae), living in the basidiocarps of Fomes fomentarius (L.) Kickx, was investigated in three forest areas in south-eastern Norway: a continuous, coniferous forest, an agricultural area with mostly deciduous forest islands in a matrix of cultivated land a homogeneous, old deciduous forest stand. B. reticulatus was almost exclusively found inside dead basidiocarps. The size of the basidiocarp was the most important variable for predicting the probability of B. reticulatus presence in the basidiocarps from all three study areas. Drier basidiocarps had a higher probability of beetle presence than the wetter ones. Basidiocarps situated above the ground level had a higher probability of beetle presence than those close to or on the ground level.In the first study area, the presence of Cisidae was found to reduce the probability of B. reticulatus presence perhaps as a result of competition. The disappearance of beetles from previously inhabited basidiocarps seemed to be due to depletion of resources.
Forfattere
O. Janne Kjønaas Arne Olav Stuanes Magne HuseSammendrag
In spite of nitrogen being a major limiting factor for forest growth in most parts of Scandinavia, increased nitrate levels in surface waters and soil water have been coupled to questions of increased inputs and decreasing immobilization of nitrogen in watersheds. To study an ecosystem response to elevated nitrogen deposition, NH4NO3 was added to a 0.52 ha forested headwater catchment in weekly portions by means of sprinklers below the canopy. Total nitrogen input as throughfall increased from the ambient 11 kg N ha-1 yr-1 to approximately 51 kg ha-1 yr-1 in the treatment years. The catchment, situated in Grdsjn, Sweden, is dominated by naturally generated Norway spruce with Scots pine in drier areas. The mean age of the forest is 104 yr. N concentrations in foliage, weight and N concentrations in litterfall, in situ net N mineralization and nitrate transformation (resin core technique), and leaching of N below the organic LFH horizon were studied on a catchment (NITREX) or plot (NITREX, CONTROL) level. This was coupled with input-output budgets to estimate fluxes and cycling of N during the pre-treatment year and the third year of treatment. There was a significant increase in net N mineralization in the NITREX plots the 3rd year of treatment, and a significant interaction between plot and year indicating a response to N addition for both net mineralization and nitrate transformation. The increased flux of nitrate from incubated soil cores, as well as the increased concentration in soil water and runoff indicated that the increased nitrification was possibly coupled with a preferential uptake of NH4---N by the microflora. The spatial variability of the nitrogen transformation rates was generally large and increased with treatment. The N concentration in needle litter showed an increase the 5th year of treatment, but no effect of nitrogen addition was found on the total weight of litterfall or on the N concentration of foliage. The key processes that determine the ecosystem response to increased inputs of nitrogen seem to be net mineralization and nitrogen transformation rates, together with the mechanism and capacity of N assimilation into the soil pool. The major sink for both externally added and internally produced inorganic N was calculated to be the soil organic pool. N assimilation into the upper organic LF horizon dominated, and this assimilation is the first of three suggested ways for coniferous ecosystems to respond to increased chronic N input.Over time, the system is hypothesized to change towards a system with a reduced assimilation capacity, a possible decreased decomposition rate, and an increased export of nitrate through leaching. The time-span of these changes is still uncertain.
Forfattere
Bernt-Håvard ØyenSammendrag
Gjennom et litteraturstudium av offentlig statistikk og andre kilder er det foretatt en vurdering av forekomst og fordeling av skog- og utmarksbranner i Norge de siste ca 200 år. Før 1913, da brannstatistikken ble en offentlig oppgave, foreligger det hovedsakelig spredte, dels usikre oppgaver. I gjennomsnitt for de siste 85 år har det brent ca 7200 dekar årlig. De årlige variasjonene i brannareal har vært store, fra ca 600 til 86 000 dekar. Omtrent ni tideler av branntilfellene er mindre enn 25 dekar. Av brente arealer er en fjerdedel produktiv veksterlig barskog, resten er mindre veksterlig barskog, uproduktiv skogsmark samt annen utmark. Gjennomsnittlig brannfeltstørrelse har falt fra ca 55 daa rundt 1920 til ca 20 daa i 1990-årene. Etter 1960 har antall branntilfeller økt, men det er trolig at mer effektiv brannbekjempelse de siste tiårene har bidratt til at arealene som rammes av skogbrann likevel synes å ligge på et relativt stabilt nivå. De tilgjengelige statistiske oppgavene indikerer at brannarealet ikke har endret seg nevneverdig siden slutten av 1800-tallet. Relativt store skogarealer ble rammet av kulturbetingete branner i midten av forrige århundre. Også kulturbetingete branner har dominert på 1900-tallet. Mer enn 80 prosent av de registrerte skogbranntilfellene i perioden 1913-97 har vært forårsaket av mennesker.
Sammendrag
Concentrations of pigments in needles of yellowish Norway spruce (Picea abies (L.) Karst.) trees suffering from either N, Mg or K deficiency in field sites in southeast Norway are reported. The yellowish trees had a considerably lower (roughly 50%) pigment concentration, as well as a lower chlorophyll/carotenoid ratio, compared to the green trees within the same sites. Yellowing was interpreted as a general bleaching of colour, as well as a slight turn from the green (chlorophylls) towards yellow (lutein). Concentrations of pigments were highly intercorrelated. N deficiency was especially associated with low a-carotene concentrations. This was interpreted as a-carotene being the most sensitive pigment to stress. However, this pigment might be specifically sensitive to N deficiency. Carbohydrate concentrations were slightly higher in yellowish trees.
Forfattere
Arne Olav Stuanes Magne Huse O. Janne Kjønaas Per Holm NygaardSammendrag
Det er ikke registrert sammendrag
Forfattere
O. Janne Kjønaas Richard Frederic WrightSammendrag
Chronic deposition of inorganic nitrogen (N) compounds from the atmosphere to forested ecosystems can alter the status of a forest ecosystem from N-limited towards N-rich, which may cause, among other things, increased leaching of inorganic N below the rooting zone. To assess the time aspects of excess N leaching, a process-oriented dynamic model, MERLIN (Model of Ecosystem Retention and Loss of Inorganic Nitrogen), was tested on an N-manipulated catchment at Grdsjn, Sweden (NITREX project). Naturally generated mature Norway spruce dominates the catchment with Scots pine in drier areas. Since 1991, ammonium nitrate (NH4NO3) solution at a rate of about 35 kg N ha-1 yr-1 (250 mmol m-2 yr-1) has been sprinkled weekly, to simulate increased atmospheric N deposition. MERLIN describes C and N cycles, where rates of uptake and cycling between pools are governed by the C/N ratios of plant and soil pools. The model is calibrated through a hindcast period and then used to predict future trends. A major source of uncertainty in model calibration and prediction is the paucity of good historical information on the specific site and stand history over the hindcast period 1930 to 1990. The model is constrained poorly in an N-limited system. The final calibration, therefore, made use of the results from the 6-year N addition experiment. No independent data set was available to provide a test for the model calibration. The model suggests that most N deposition goes to the labile (LOM) and refractory (ROM) organic matter pools. Significant leaching is predicted to start as the C/N ratio in LOM is reduced from the 1990 value of 35 to 28. At ambient deposition levels, the system is capable of retaining virtually all incoming N over the next 50 years. Increased decomposition rates, however, could simulate nitrate leaching losses. The rate and capacity of N assimilation as well as the change in carbon dynamics are keys to ecosystem changes. Because the knowledge of these parameters is currently inadequate, the model has a limited ability to predict N leaching from currently N-limited coniferous forest ecosystems in Scandinavia. The model is a useful tool for bookkeeping of N pools and fluxes, and it is an important contribution to further development of qualitative understanding of forest N cycles.
Sammendrag
I Program for terrestrisk naturovervåking (TOV) ble det samlet inn jordvann fra fire over-våkingsflater i 1997. Disse ligger på Lund (Rogaland), Solhomfjell (Aust-Agder), Møsvatn (Telemark) og Gutulia (Hedmark). Flatene ligger i områder med blåbærskog. Fra overvåkingen startet i 1991 og frem til 1997 har det blitt registrert en nedgang i jordvannets pH fra henholdsvis 4,96 til 4,26 (medianverdier) og konsentrasjon av Ca2+ i 15 cm sjiktet på Lund fra 1,53 til 0,26 (medianverdier). Nedbør og kronedrypp fra Lund hadde også lavere pH samt høgere konsentrasjon av SO42- og Cl- enn det som var tilfelle på de andre flatene. Det var imidlertid ingen tegn på dårligere skogvitalitet på Lund som følge av forholdene nevnt over. Generelt for alle flatene var det store årlige variasjoner i konsentrasjonen av Ca2+, Mg2+, K+ og tot-Al i jordvannet i 5 cm sjiktet, mens konsentrasjonen og variasjonen avtok nedover i jorda. Alle flatene hadde lave konsentrasjoner av NH4-N og NO3-N i jordvannet (nær deteksjonsgrensen på henholdsvis 0,05 og 0,02 mg/l) i hele overvåkings-perioden. Det er sannsynligvis flere årsaker til de endringene som observeres i jordvannet. Dette er forhold som bør følges nøye videre i TOV.