Southeast Norway Research Articles

Fungal pathogens in Norwegian lettuce fields

Norwegian field production of lettuce has increased considerably since the early 1990s. Disease problems rarely required fungicide applications before 1996, when lettuce downy mildew (Bremia lactucae) caused severe losses. From 2002 to 2004, surveys were conducted to identify fungal diseases in Buskerud, Vestfold and Østfold counties in the south-east and Rogaland County in the south-west, representing the main lettuce production regions of Norway. The distribution and incidence of B. lactucae was highly variable, but this pathogen was the most important due to the destructive nature of uncontrolled epidemics. Septoria lactucae caused severe damage, but was found in only one field. Sclerotinia sclerotiorum was the most widespread pathogen, found in 32% of the fields, but usually affecting less than 10% of the plants. Pythium tracheiphilum was reported from 33% of the fields in south-east Norway, but was not found in the south-west. Disease incidence was usually less than 5%, and a disease incidence of more than 10% was reported in one field only. Other pathogens of potential economic importance in Norwegian lettuce fields are Alternaria spp., Botrytis cinerea and Rhizoctonia solani, although they were sporadically distributed in relatively few fields in this survey.

Fungicide Leaching from Golf Greens: Effects of Root Zone Composition and Surfactant Use

Soil water repellency in golf putting greens may induce preferential "finger flow," leading to enhanced leaching of surface applied fungicides. We examined the effects of root zone composition, treatment with a non-ionic surfactant, and the use of the fungicide iprodion or a combination of azoxystrobin and propiconazole on soil water repellency, soil water content distributions, fungicide leaching, and turf quality during 1 yr. Soil water repellency was measured using the water drop penetration time (WDPT) test and tension infiltrometers. Our study was made on a 3-yr-old experimental green seeded with creeping bentgrass (Agrostis stolonifera L.) 'Penn A-4' at Landvik in southeast Norway. The facility consists of 16 lysimeters with two different root zone materials: (i) straight sand (1% gravel, 96% sand, 3% silt and clay, 4 g kg(-1) organic matter) (SS) and (ii) straight sand mixed with garden compost to an organic matter content of 21 g kg(-1) (Green Mix [GM]). Surfactant treatment resulted in 96% lower average WDPTs at 1 cm depth, three times higher water infiltration rates at the soil surface, and reduced spatial variation in soil water contents. Fungicide leaching was close to zero for the GM lysimeters probably due to stronger sorption. Concentrations in the drainage water from SS lysimeters often exceeded surface water guideline values for all three fungicides, but surfactant treatment dramatically reduced fungicide leaching from these lysimeters. In autumn and winter, surfactant-treated plots were more infected with fungal diseases probably because of higher water content in the turfgrass thatch layer.

Relations between nitrogen leaching and food productivity in organic and conventional cropping systems in a long-term field study

An ideal agricultural system should both maximize food production and minimize undesirable effects on the environment. The long-term Apelsvoll cropping system experiment, located in southeast Norway, was used in this study, to compare yields, major N flows (in particular measured leaching/runoff losses) and the N loss-to-food production ratios (LFP-ratios) in six different cropping systems over a 4-year period. The experiment included three systems with cash-cropping (CA1: conventional arable farming; CA2: arable farming practice with environmentally sound management; OA: organic arable farming with 25% of the area as green manure, and three systems with both arable and fodder crops, representing mixed dairy production (CM: conventional farming practice with 50% grass–clover ley; OM1: organic farming with 50% grass–clover ley; OM2: organic farming with 75% grass–clover ley). The forage production was assumed to be used for milk and meat production, in amounts calculated on the basis of available feed and estimated requirements for dairy cattle. All farm produce (cereals, potatoes, milk and meat) was converted into metabolizable energy for human consumption. Organic cropping gave significantly lower yields than conventional cropping, for both arable and mixed dairy systems, most likely due to sub-optimal plant nutrition and the lack of plant protection in the organic systems. The average net energy production in CA1 and CA2 was 2.4–5.3 times greater than that in the other systems, which illustrates the energy costs of taking 25% of the area out of food production to produce green manure (OA) and the energy cost of including an extra trophic level in the nutrient chain (CM, OM1 and OM2). Only CA2 and CM appeared to have a balanced N budget, whereas the other systems all had N deficits, in particular CA1 and OA. The total N losses to drainage were largest from CA1, but not significantly larger than those from OA, which had the largest N runoff of the systems, most likely due to the green manure in its rotation. The conventional system with environmentally sound management (CA2) had the lowest LFP-ratios overall. Among the arable cropping systems, the organic system with 25% green manure (OA) had the highest LFP-ratios. The mixed dairy systems had generally higher LFP-ratios than the arable systems. Including leaching/runoff N losses in the LFP-ratio, CA1, CA2, OA, CM, OM1 and OM2 appeared to lose 0.6, 0.4, 1.1, 0.9, 1.2 and 1.1 kg N, respectively, per GJ of produced metabolizable energy for human consumption.

Mercury budget of a small forested boreal catchment in southeast Norway

We present input and output fluxes of total mercury (Hg tot) and methyl mercury (MeHg) based on throughfall, litterfall and stream water samples from 2004/2005 from a small forested catchment (Langtjern) in Norway. Hg tot input via throughfall and litterfall was estimated to 6.7 and 2.7 µg m − 2 yr − 1 , respectively, which is considerably lower than previously reported from other boreal catchments in Scandinavia. A likely cause for the low input flux is the sparseness and low productivity of the forest in the Langtjern catchment, with less atmospheric scavenging and lower litterfall fluxes than previously studied sites. In addition there has been a general decrease in mercury (Hg) in the atmosphere on the northern hemisphere in the last decade. The estimated output flux of Hg tot with surface water was 2.5 µg m − 2 yr − 1 , which is comparable to what has been reported elsewhere. The ratio of Hg tot output flux to input flux was 26%, which is considerably higher than reported from other sites. This illustrates that catchment properties have greater importance for surface water export of Hg than the current atmospheric input. The estimated total soil pool of Hg tot in the catchment was 17.4 mg m − 2 . This corresponds to roughly 8000 years of the current surface water output flux and 2000 years of the current input flux.

Centric fission in Microtus oeconomus. A new locality in south east Norway.

Centric fission in Microtus oeconomus. A new locality in south east Norway.

Vitamin status in morbidly obese patients: a cross-sectional study

Background:Morbid obesity is associated with low circulating concentrations of 25-hydroxyvitamin D. Few data on the concentrations of other vitamins in morbidly obese patients are available. Objective:The objective was to compare serum and blood vitamin concentrations in morbidly obese patients with those in healthy subjects. Design:In 2 public hospital departments (southeast Norway), we prospectively examined 110 consecutive patients (76 women) and 58 healthy controls (30 women) not taking multivitamin supplements. Patients and controls did not differ significantly in age or ethnicity. The mean (±SD) body mass index (in kg/m2) was 45 ± 7 in the patients and was 24 ± 3 in the controls. Patients with vitamin concentrations lower than 2 SD below the sex-specific mean in controls were considered to have inadequate vitamin status. Results:The morbidly obese women and men had significantly lower concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and lipid-standardized vitamin E than did the healthy controls (P < 0.01 for each). The status of these vitamins was inadequate in a substantial proportion of the patients (11–38%). The status of vitamins A, B-1, B-2, and B-12 and of folic acid was adequate in most of the patients (95–100%). A moderately elevated C-reactive protein concentration was associated with lower vitamin A, B-6, and C concentrations. In a multiple regression analysis, concentrations of alkaline phosphatase (inverse relation) and vitamin C were the strongest determinants of serum vitamin B-6 concentrations. Conclusions:Low concentrations of vitamin B-6, vitamin C, 25-hydroxyvitamin D, and vitamin E adjusted for lipids are prevalent in morbidly obese Norwegian patients seeking weight-loss treatment.

Stand age and fine root biomass, distribution and morphology in a Norway spruce chronosequence in southeast Norway

We assessed the influence of stand age on fine root biomass and morphology of trees and understory vegetation in 10-, 30-, 60- and 120-year-old Norway spruce stands growing in sandy soil in southeast Norway. Fine root (< 1, 1-2 and 2-5 mm in diameter) biomass of trees and understory vegetation (< 2 mm in diameter) was sampled by soil coring to a depth of 60 cm. Fine root morphological characteristics, such as specific root length (SRL), root length density (RLD), root surface area (RSA), root tip number and branching frequency (per unit root length or mass), were determined based on digitized root data. Fine root biomass and morphological characteristics related to biomass (RLD and RSA) followed the same tendency with chronosequence and were significantly higher in the 30-year-old stand and lower in the 10-year-old stand than in the other stands. Among stands, mean fine root (< 2 mm) biomass ranged from 49 to 398 g m(-2), SLR from 13.4 to 19.8 m g(-1), RLD from 980 to 11,650 m m(-3) and RSA from 2.4 to 35.4 m(2) m(-3). Most fine root biomass of trees was concentrated in the upper 20 cm of the mineral soil and in the humus layer (0-5 cm) in all stands. Understory fine roots accounted for 67 and 25% of total fine root biomass in the 10- and 120-year-old stands, respectively. Stand age had no affect on root tip number or branching frequency, but both parameters changed with soil depth, with increasing number of root tips and decreasing branching frequency with increasing soil depth for root fractions < 2 mm in diameter. Specific (mass based) root tip number and branching density were highest for the finest roots (< 1 mm) in the humus layer. Season (spring or fall) had no effect on tree fine root biomass, but there was a small and significant increase in understory fine root biomass in fall relative to spring. All morphological characteristics showed strong seasonal variation, especially the finest root fraction, with consistently and significantly higher values in spring than in fall. We conclude that fine root biomass, especially in the finest fraction (< 1 mm in diameter), is strongly dependent on stand age. Among stands, carbon concentration in fine root biomass was highest in the 30-year-old stand, and appeared to be associated with the high tree and canopy density during the early stage of stand development. Values of RLD and RSA, morphological features indicative of stand nutrient-uptake efficiency, were higher in the 30-year-old stand than in the other stands.

Gyrodactylus species (Monogenea) infecting alpine bullhead (Cottus poecilopus Heckel, 1837) in Norway and Slovakia, including the description of Gyrodactylus mariannae sp. nov.

AbstractGyrodactylus specimens infecting the skin and fins of two alpine bullhead (Cottus poecilopus) populations from the rivers Signaldalselva (North Norway) and Rena (South-East Norway) were characterized by both morphological and molecular means. Morphometrical differences were minor and the nucleotide sequences of the internal transcribed spacers (ITS) of the nuclear rDNA cluster were identical for parasites from both localities. Based on earlier descriptions, the relatively closest species are Gyrodactylus hrabei Ergens, 1957, described from common bullhead (Cottus gobio) in Slovakia and G. sp. Malmberg, 1973, from alpine bullhead in Sweden. The Norwegian Gyrodactylus specimens from the two alpine bullhead populations were morphometrically different from both the type material of G. hrabei from Slovakia and newly collected Gyrodactylus specimens from alpine bullhead in two Slovakian localities. The Slovakian Gyrodactylus specimens were found to be identical with type material of G. hrabei. The nucleotide sequences of the ITS of the Norwegian Gyrodactylus species were different from the Slovakian material. Hence, the Norwegian Gyrodactylus specimens from the alpine bullhead represent a new species, G. mariannae sp. nov.

Habitat and diet of young grouse broods: resource partitioning between Capercaillie (Tetrao urogallus) and Black Grouse (Tetrao tetrix) in boreal forests

We compared habitat use and diets of young Capercaillie and Black Grouse broods in a boreal forest in southeast Norway. We used pointing dogs to search for broods (N = 83) in mature “natural” forest types and examined the crop content of 66 chicks 1–9 weeks old. We also measured the abundance of insects in the habitats where broods were found. Although overlapping substantially in both habitat and diets, there were notable differences: Capercaillie broods were more frequently recorded in bilberry-dominated forest types, whereas Black Grouse preferentially used pine bog forest, a more open habitat with little bilberry. Capercaillie chicks ate proportionally more insects, particularly lepidopteran larvae, and insects dominated their diet for a longer period of time (until age 28–29 days) than in Black Grouse (14–15 days). After reaching their peaks, the quantity of insects in the crops declined rapidly especially in Capercaillie, and in one of 2 years this occurred at a time when insects, including larvae, were still abundant in the habitats. Among plant foods, both species ate large amounts of Bilberry (Vaccinium myrtillus) and Bog Whortleberry (V. uliginosum). The main difference between species was a large proportion of both over-wintered and new, not yet ripe, berries of Cranberry (Oxycoccus quadripetalus) in Black Grouse, and a higher proportion of the forb Melampyrum sylvaticum in Capercaillie. The difference in diets reflected their differential use of habitats; the Vaccinium-preferred habitats of Capercaillie were richer in insects, particularly larvae, than the pine bog habitat preferred by Black Grouse. Because insects, especially larvae, comprised a larger proportion of the diet of Capercaillie chicks and chicks of this species need more food to sustain their rapid growth, Capercaillie is likely to be more sensitive to variation in insect food than Black Grouse. Also, by reducing the abundance of bilberry, the main host plant of larvae chick food, clearcutting forestry has negative effects on the brood habitat quality of both species.

Moose winter browsing affects the breeding success of great tits

In many areas, ungulates may have a large impact on the landscape due to their large body size and wide distribution. Moose (Alces alces) winter feeding has been carried out for a decade in parts of Hedmark County, southeast Norway. Previous studies have documented a gradual decline in browsing pressure away from the feeding stations. We utilized this gradient to study the indirect effects of moose browsing on a passerine bird, the great tit (Parus major). The downy birch (Betula pubescens) trees surrounding the feeding stations are subject to an intense browsing pressure gradually decreasing outwards. We put up nest boxes at feeding stations (i.e., sites of intense browsing pressure), with nearby controls with low visible browsing. The number of tall birch trees and the birch canopy cover was lower in browsed compared to control plots. Due to the reduced birch canopy cover, the total biomass of arthropods available around the nest boxes was lower in browsed compared to control plots. Great tit breeding pairs produced 1.3 fewer fledglings in browsed compared to control plots. We suggest this difference to be caused by lack of food in the browsed plots. Hence, moose browsing may reduce the breeding success of great tits through a series of knock-on effects through two other components of the boreal forest community.

Predicting snow density using meteorological data

AbstractThis paper presents a simple method for predicting snow density by use of weather data. Six hundred and eight snow density (bulk weight density) measurements from the period 1967–1986 are used in a multiple regression analysis. The measurements are performed at 105 sites in the Ås area situated in Akershus County in southeast Norway. The area has a relatively stable winter climate. Weather data from an observing station with three registrations a day are used in the analyses. The distance between the measurement sites and the meteorological station varied between 0.6 and 14 km. A clear correlation is found between the observed climate and the measured snow density. A multiple regression equation is developed with a coefficient of determination equal to 70% and a standard deviation equal to 24 kgm−3. Snow density values suggested in the Norwegian code NS 3491‐3 is in most cases overestimated. Expressions given in an annex to the international regulations for snow loading on roofs (ISO 4355) are less applicable to prescribing snow density for climate studied in this investigation. Still, they can be used as simple and rough estimates. Copyright © 2007 Royal Meteorological Society

Hospital‐treated psychosis and suicide in a rural community (1877–2005). Part 1: Incidence rates

To calculate the incidence rates of hospital-treated psychosis and suicide in historical cohorts of a small rural community in southeast Norway, and to compare the local findings with the national ones. We have carried out a longitudinal epidemiological study, reviewing the patient records at the mental hospitals of people born in the rural community after 1845. Based on these records, we have constructed a local register of psychosis and suicide in this population. The local incidence rates of psychosis and suicide have been compared with the national ones. The overall local incidence rates of psychosis and suicide were similar to the national ones. The local rates of schizophrenia dropped considerably after World War II. The overall local incidence rates of psychosis and suicide seem to be representative for the country at large despite frequent endogamy. The recent drop in the incidence rate of schizophrenia seems to be in agreement with several international studies.

Nitrogen rates in seed production of two contrasting cultivars of common bent (Agrostis capillaris)

Field trials comparing various combinations of 0, 30 or 60 kg N ha−1 in autumn (September) and/or spring (April) to seed crops of common bent (syn. browntop, US: colonial bentgrass, Agrostis capillaris L.) ‘Leikvin’ (main use: long-lasting pastures and utility turf) and ‘Nor’ (main use: lawns and golf course fairways) were carried out on silt loam soils at Landvik, south-east Norway (58°N) from 1989 to 1994. One trial per cultivar was established in 1989, 1990 and 1991, each trial being harvested for three years. On average, for nine harvests and nine N treatments, ‘Leikvin’ and ‘Nor’ gave seed yields of 276 and 128 kg ha-1, respectively. Seed yields of ‘Leikvin’ increased with increasing N rate up to 60 kg N ha−1 in autumn and 30 kg N ha−1 in spring; no interaction between autumn and spring N rate could be detected in this cultivar. In ‘Nor’, a significant autumn x spring rate interaction indicated a linear seed yield response to N in spring on plots that had received 60 kg N ha−1 in autumn, but a diminishing response to N in spring on plots that had received 0 or 30 kg N ha-1 in autumn; the highest seed yield was produced with autumn + spring applications of 60 + 60 kg N ha−1 in this lawn cultivar. While panicle number and seed number per panicle were equally important for seed yield in ‘Leikvin’, panicle number had the stronger impact on seed yield in'Nor'. Seed crops of ‘Leikvin’ were generally taller and more susceptible to lodging than seed crops of ‘Nor’. Year-to-year variations in seed yield level and optimal N regime were less related to crop age than to weather conditions and seed crop management. Given the present prices for fertilizer and seed, it is concluded that Norwegian seed crops of common bent should receive 50–60 kg N ha−1 in autumn regardless of cultivar. Economically optimal N rates in spring are 30 and 60 kg N ha−1 to ‘Leikvin’ and ‘Nor’, respectively.

Elevated levels of polybrominated diphenyl ethers (PBDEs) in fish from Lake Mjøsa, Norway

Surprisingly high levels of PBDEs (polybrominated diphenyl ethers) in fish from Lake Mjøsa watercourse initialized a more detailed study of PBDE contamination in the Lake Mjøsa region as well as fish from other lakes in southeast Norway. With exception of the fish from Lake Mjøsa, the sum concentration of PBDEs in trout was, on a wet weight (ww) basis, in the range of 0.3–40 ng/g (21–1215 ng/g lipid weight (lw)) in fish fillet and 39–446 ng/g (125–915 ng/g lw) in burbot liver. The PBDE levels in fish from Lake Mjøsa, was found in the range of 72–1120 ng/g ww (2348–16,753 ng/g lw) in trout and 156–2265 ng/g ww (4201–45,144 ng/g lw) in burbot. It was later confirmed that the elevated levels in Lake Mjøsa were mainly caused by the release of PBDEs to the water from a textile manufacturer in the town of Lillehammer. In addition to PBDE levels in fish we also present information on the spatial distribution of PBDEs in air around the Mjøsa watercourse, based on the complementary use of passive air samples and analysis of moss, including data on measured air concentrations. The results confirm the presence of an active source of atmospheric PBDEs in the region of Lillehammer. Although this source appears to have a limited impact on atmospheric levels towards the southern reaches of the lake, it could still be a significant source of PBDEs to the lake as a whole. However, more research is needed to better understand and quantify the relative importance of various sources and pathways for which PBDEs enter Lake Mjøsa in order to support the development of future control strategies.

Multistage, Long‐Range Natal Dispersal by a Global Positioning System‐Collared Scandinavian Wolf

Abstract: We document a new record dispersal for wolves worldwide. The natal straight‐line dispersal distance of a Global Positioning System‐collared female wolf from the Scandinavian population was 1,092 km from southeast Norway to northeast Finland, with a multistage actual travel distance of &gt;10,000 km. Natural gene flow to the isolated, inbred Scandinavian wolf population may occur if survival of dispersers is improved.

Cold climatic conditions: Effects on bioavailability and leaching of the mobile pesticide metribuzin in a silt loam soil in Norway

Little research has been done on pesticide dissipation under cold climates, and there is a need to focus on the influence of climate on pesticide degradation in soil and the risk of leaching to surface and ground waters. The objective of the work reported here was to increase the knowledge on the fate and risk of leaching of the mobile herbicide metribuzin under cold climatic conditions. Small-scale laboratory investigations of the metribuzin transformation process in soil at temperatures above and below 0 °C have been performed parallel to and for comparison with, metribuzin dissipation studies under field conditions at a field site on silt loam soil (Fluvic Cambisol) in the South East of Norway. As expected, field results indicated faster degradation of metribuzin with increasing temperature, as summer temperatures differed significantly between years. Estimated dissipation rates appeared to be further affected by precipitation patterns, with high precipitation causing faster pesticide transport through the soil profile and possibly bypassing layers of high biological activity. Estimated half-lives close to 1 month during summer were in accordance with other reports, and in good agreement with laboratory scale studies under optimum conditions at 20 °C (t1/2 = 22 days). Sorption experiments showed weak sorption of metribuzin in this silt loam soil (Kd-values below 0.5), only poorly correlated to soil organic carbon content (r2 = 0.76). Laboratory studies of metribuzin degradation and bioavailability at low and below zero temperatures, indicated that frost will increase the mobility of metribuzin in soil by increasing the pore water concentrations upon release of frost; the longer the frost period, the larger the increase in leachable metribuzin concentrations. Further, metribuzin degradation at temperatures below 5 °C was found to be so slow that we would not expect the soil microorganisms to be able to exploit this increased availability of metribuzin. Leaching during cold climatic periods (autumn, winter and spring) in this temporarily frozen soil, will bring metribuzin to deeper soil layers of low biological activity and a generally lower sorption capacity for pesticides, due to lower contents of soil organic carbon. Hence, residues of metribuzin might be recovered in the soil, down to deeper soil layers, one year after spraying. Risk assessment methods for pesticide leaching in cold climatic conditions should consider winter/spring processes, and knowledge about winter processes will be particularly important for forecasting effects of climatic change on leaching.

Optimizing seed crops of common bent (Agrostis capillaris) by sowing rate

As part of a project to stimulate Norwegian seed production of common bent (syn. browntop, US: colonial bentgrass, Agrostis capillaris L. syn. A.tenuis Sibth.) field trials comparing sowing rates of 2.5, 5.0, 7.5 or 10 kg ha−1 were conducted at Landvik, south-east Norway, (58°N) from 1989 to 1994. Three trials were laid out of the forage cultivar ‘Leikvin’ and three trials of the lawn cultivar ‘Nor’, each trial being harvested for three consecutive years. While the average per cent ground cover in spring increased from 87% at 2.5 kg ha−1 to 94–96% at 7.5 kg ha−1, seed yields decreased with increasing sowing rate in both cultivars. On average for all harvests, quadrupling the sowing rate from 2.5 to 10 kg ha−1 reduced seed yield by 9% in ‘Leikvin’ and 15% in ‘Nor’, the stronger effect probably being associated with a greater competition between tillers in the lawn cultivar. Seed yield reductions with increasing sowing rate showed no relationship with crop age, but were less accentuated for crops undersown in spring wheat in a dry year than for crops established without cover crop in years with ample rainfall in early summer. Increasing sowing rates reduced plant height and panicle number in ‘Nor’, but had no effect on seed weight or germination in any of the cultivars. It is concluded that seed crops of common bent should be established with a sowing rate of 2–5 kg ha−1, with the lowest rate in lawn cultivars, under ideal seedbed conditions and when seed crops are sown without cover crop.

Using airborne laser scanning to monitor tree migration in the boreal–alpine transition zone

The boreal tree line is expected to advance upwards into the mountains and northwards into the tundra due to global warming. The major objective of this study was to find out if it is possible to use high-resolution airborne laser scanner data to detect very small trees — the pioneers that are pushing the tree line up into the mountains and out onto the tundra. The study was conducted in a sub-alpine/alpine environment in southeast Norway. A total of 342 small trees of Norway spruce, Scots pine, and downy birch with tree heights ranging from 0.11 to 5.20 m were precisely georeferenced and measured in field. Laser data were collected with a pulse density of 7.7 m − 2 . Three different terrain models were used to process the airborne laser point cloud in order to assess the effects of different pre-processing parameters on small tree detection. Greater than 91% of all trees > 1 m tall registered positive laser height values regardless of terrain model. For smaller trees (< 1 m), positive height values were found in 5–73% of the cases, depending on the terrain model considered. For this group of trees, the highest rate of trees with positive height values was found for spruce. The more smoothed the terrain model was, the larger the portion of the trees that had positive laser height values. The accuracy of tree height derived from the laser data indicated a systematic underestimation of true tree height by 0.40 to 1.01 m. The standard deviation for the differences between laser-derived and field-measured tree heights was 0.11–0.73 m. Commission errors, i.e., the detection of terrain objects — rocks, hummocks — as trees, increased significantly as terrain smoothing increased. Thus, if no classification of objects into classes like small trees and terrain objects is possible, many non-tree objects with a positive height value cannot be separated from those actually being trees. In a monitoring context, i.e., repeated measurements over time, we argue that most other objects like terrain structures, rocks, and hummocks will remain stable over time while the trees will change as they grow and new trees are established. Thus, this study indicates that, given a high laser pulse density and a certain density of newly established trees, it would be possible to detect a sufficient portion of newly established trees over a 10 years period to claim that tree migration is taking place.

Plot studies and modelling of hydrology and erosion in southeast Norway

Soil erosion causes environmental problems in the agriculture landscapes of southeast Norway (785 mm y − 1 , 5.3 °C), especially on artificially levelled soils. Plot at five sites located within 60 km of Oslo mostly cultivated with small grain were used. They represented three soils: A) artificially levelled silty clay loam (3 sites); B) clay (1 site); and C) unlevelled loam with high aggregate stability (1 site). Mostly two of the used tillage systems are reported here: Pl-Au (ploughing in autumn, harrowing in spring), No-Au (no tillage in autumn). Winters could be cold, mild or variable. Due to the distribution of rainfall, evaporation and soil frost during the year, most of the surface runoff occurred during winter and early spring, but also in late autumn due to soil saturation by water. Average losses over 7 yr by Pl-Au were: 2700–6350 kg ha − 1 yr − 1 for soil type A, 1043 for type B and 158 for type C. With no tillage in autumn the following losses relative to ploughing autumn were 0.12, 0.2 and 0.66 respectively for A, B and C soils. Erosion risk was highest with autumn tillage, especially on soil A mostly due to the levelling effect. Infiltration capacity were greatest and erodibility lowest on soil type C. Infiltration capacity was less than 1 mm/h at saturation on soil type A causing surface runoff, even with moderate rainfall intensities. The empirical yet dynamic erosion model ERONOR simulated well the average soil losses for soil types and tillage systems over several years and also distributed surface runoff and soil losses throughout the year satisfactorily. The model does not handle processes on a large scale, but still it worked rather well in agricultural watersheds with no appreciable net losses due to large scale processes. The model can point out parcels with a high erosion risk within a watershed, and it can estimate the energy factor R in the Norwegian version of the USLE. The model predicts increased erosion in southeast Norway based on climate predictions of milder and rainier winters.

Variability in topsoil texture and carbon content within soil map units and its implications in predicting soil water content for optimum workability

The ability to predict the timing of optimum soil workability depends on knowledge of the extent and structure of variability in main physical characteristics of the soil. Our objectives were to quantify the variability in texture and carbon content within soil map units in a small agriculture-dominated catchment in South-east Norway and to assess implications of variability in texture and carbon content on land management operations, using the predicted maximum water content for optimum workability as an example. Information from three different sources were used: a soil map (1:5000), a large sample grid (100 m spacing, 270 ha extent), and a small sample grid (10 m spacing, 2.25 ha extent). Readily available information on texture and organic matter content from the soil map was found to be of limited use for soil management due to broad textural classes together with deviations from the mapped main textural classes. There were significant differences in clay, silt and sand content between the different soil textural classes on the soil map. Statistical distributions within soil map units were generally either positively or negatively skewed and the coefficient of variation was intermediate, 15–50%. Most of the variation in both grids was spatially correlated. The large grid was dominated by a patchy structure, whilst the small grid showed a systematic trend with a gradual transition indicating fuzzy boundaries between map units in this catchment. The effective range for texture was 16 times larger in the large grid. Implications of variability in texture and carbon content on land management operations were assessed for the maximum water content for optimum workability (Wopt), predicted using pedotransfer functions. Wopt was usually in the same range as the water content at–100 kPa matric potential, indicating that considerable evaporation in addition to drainage is required for obtaining workable conditions in the field. The time required for obtaining the water content was estimated to about 5 days, which is longer than an average length of periods without precipitation in the area, median 3.7 days. Wopt predicted from the soil map deviated strongly from Wopt predicted from the sample grids. Comparing estimates of Wopt from the large grid with measurements in the small grid showed differences corresponding to ±2–3 days of evaporation.