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.
2010
Abstract
Transport and turnover of dissolved organic carbon (DOC) is important in the C cycle of organic soils. The concentration of DOC in soil water is buffered by adsorption to the soil matrix, and has been hypothesized to depend on the pool size of adsorbed DOC. We have studied the effect of frequent artificial excessive leaching events on concentration and flux of DOC in shallow, organic rich mountain soils. Assuming a constant Kd value for DOC adsorption to the soil matrix, we used these data to assess the change in the pool of adsorbed (or potential) DOC in the soil. The study involved manipulation of precipitation amount and frequency in summer and autumn in small, heathland catchments at Storgama, southern Norway. The shallow soils (16-34 cm deep on average) limit the possibility for changes in water flow paths during events. The mini-catchments range in size from 75 to 98 m(2). Our data show that after leaching of about 1.2 g DOC m(-2) the DOC concentration in runoff declines by approximately 50%. From this we conclude that the pool size of adsorbed potential DOC in the shallow soils at any time is of the order 2-3 g m(-2). Frequent episodes suggest that the replenishment rate, which depends on the decomposition rate of soil organic matter, is fast and the potential DOC pool could be fully restored probably within days during summer, but with some more time required in autumn, due to lower temperatures. Both pool size of potential DOC and replenishment rate are seasonally dependent. The pool of potential DOC, and thus the DOC concentration in discharge, is at their maximum in the growing season. However, under non-leaching conditions, the concentration of DOC in soil water and thus the pool size of potential DOC seems to level off, possibly due to conversion of DOC to less reversibly bound forms, or to further decomposition to CO2.
Abstract
We investigated concentrations of dissolved organic carbon (DOC) in throughfall and soil solutions at 5, 15 and 40 cm depth in 16 Norway spruce and 2 Scots pine plots throughout Norway between 1996 and 2006. Average DOC concentrations ranged from 2.3 mg/l to 23.1 mg/l and from 1.1 mg/l to 53.5 mg/l in throughfall water and soil solutions, respectively. Concentrations of DOC in throughfall and soil waters varied seasonally at most plots with peaks in the growing season. By contrast to recently reported positive long-term trends in DOC concentrations in surface waters between 1986 and 2003, soil water data from 1996 to 2006 showed largely negative trends in DOC concentrations and no significant trends in throughfall. However, regression analysis for individual sites, particularly at 5 and 15 cm soil depths, showed that DOC concentrations in soil water were significantly and negatively related to non-marine sulphate (SO4) and chloride (Cl-). The lack of a long-term increase in DOC in soil water in the period May 1996 – December, 2006 may be due to the relatively small changes in the deposition of SO4 and Cl- in this period.
Abstract
Dissolved organic nitrogen (DON) plays an important ecological role in forest ecosystems, and its concentration is related to that of dissolved organic carbon (DOC). We investigated DON concentrations and ratios of DOC to DON in throughfall and soil waters in 16 Norway spruce and two Scots pine forest stands sampled at weekly intervals between 1996 and 2006. The stands are all included in the ICP Forests Level II monitoring program and are located throughout Norway. DON concentrations were significantly and positively related to DOC concentrations in throughfall (r (2) = 0.72, p < 0.0001) and soil water at 5, 15, and 40 cm (r (2) = 0.86, 0.32, and 0.84 and p < 0.0001, 0.04, and < 0.0001, respectively). At most sites, the annual median DOC/DON ratio in throughfall ranged from 20.3 to 55.5, which is lower than values in soil water, which ranged from 24.5 to 81.3, gradually decreasing with soil depth. DON concentrations varied seasonally in throughfall at many plots and in soil water at 5-cm depth at one plot only, with higher values in the growing season, but there was no noticeable seasonality at greater depth. The ratios of DOC/DON in soil water were significantly positively related to the C/N ratio in soil at the same depth. Above-ground litter input was the main factor having a significant, negative relationship to DOC/DON in soil water at all depths studied. This might reflect the effect of site conditions on both DOC/DON ratios and litter quantity.
Authors
Andreas C. Drichoutis Rudolfo M. Jr. Nayga Panagiotis LazaridisAbstract
No abstract has been registered
Abstract
During the first few weeks of life, chicks of the capercaillie (Tetra urogallus) and black grouse (T. tetrix) subsist mainly on insects, of which lepidopteran and hymenopteran larvae are the main components. We studied the breeding phenology of these two species and examined how the timing of breeding was related to the temporal distribution of their larval food source. During a five-year survey, capercaillie mated and hatched consistently four to six days before black grouse. Depending on the vegetation type, the number of larvae (>= 2 mm in length) increased between five and ten times within 10 days, and hatching coincided roughly with the peaks in larval numbers. Due to body growth, however, larval abundance in terms of volume was reached later and occurred 8-9 and 13-14 days after the mean hatching dates in the two species, respectively. Slightly later development of Hymenoptera as compared with that of Lepidoptera contributed in extending the period of high larval abundances for more than one week. The timing of breeding of the two species appears, therefore, to match the temporal distribution of insect food for the fast-growing chicks as they hatch several days before the peak in larval volumes. In one year, when mating was advanced, presumably due to exceptionally warm weather before mating (yet the temporal abundance of larvae was unchanged), breeding success was higher than in years when mating occurred later.
Abstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Earliness, fruit yield and quality of six annual-fruiting raspberry (Rubus idaeus L.) cultivars were tested under protected cultivation in a cool Nordic environment. After raising plants for 5 weeks in greenhouses with average mean temperatures of 20 degrees C, 22 degrees C, or 26 degrees C, the plants were cropped in an open plastic tunnel at latitude 61 degrees N. The highest yielding cultivars were 'Autumn Bliss' and 'Polka', with 640 g plant(-1). Overall, the most promising cultivar was 'Polka' which combined high yield with large fruit of good flavour and firmness. In earliness, 'Polka' was surpassed only by 'Autumn Bliss', which confirmed its position as the earliest commercial annual-fruiting cultivar. However, 'Autumn Bliss' had soft fruits with little flavour and a short shelf-life, which greatly reduced the potential of the cultivar for the fresh fruit market. The later ripening cultivar 'Erika' did not complete its crop under these conditions, but its large unrealised yield potential and good fruit quality rendered it extremely promising for environments with a longer growing season. 'Sugana' was late, with low yields and poor fruit quality, while 'Marcela' did not yield enough fruit to be of interest under the present conditions. High temperatures during the 5-week raising period generally advanced flowering and fruit ripening in all cultivars, with the notable exception of 'Autumn Treasure' in which flowering was suppressed and strongly delayed by high temperature. Under the present conditions, there was a highly positive correlation between earliness and fruit yield. Regression analyses identified a low number of dormant buds as the single most important component of plant architecture associated with high fruit yield, accounting for 47% of the total variation.
Abstract
No abstract has been registered
Authors
Håvard SteinshamnAbstract
Literature data from experiments with lactating dairy cows offered silage-based diets was reviewed to evaluate the effects of the grassland legume species Trifolium repens (WC, white clover), Trifolium pratense (RC, red clover) and Medicago sativa (M, lucerne) on feed intake, milk production and milkquality. Seven data sets were created to compare grass silage (G) with grassland legumes in general (L), G with RC, G with WC, G with M, RC with WC, RC with M and different silage proportions of RC. Daily dry matter intake and milk yield were on average 1.6 and 1.6 kg, respectively, higher and milk fat content 1.2 g/kg milk lower on L than on G based diets. Similar differences were found when G was compared with RC or WC diets. Cows offered WC yielded 1.1 kg/d more milk than RC, and milk produced on WC and M contained 0.7 g more protein per kg than milk from RC diets. Increasing the silage diet RC proportion from 0.5 to 1.0 also decreased the milk protein content by 0.8 g/kg milk. RC increased the level of poly-unsaturated fatty acids, particularly C18:3n-3, and isoflavones, particularly equol, in milk. Effects are discussed in relation to plant cell wall characteristics, plant chemical constituents and changes in rumen digestion to explain the origin of the differences in intake, milk yield and milk composition.