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.
1988
Forfattere
Gunnar Ogner Kristian BjorSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor J. JohansenSammendrag
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Forfattere
Halvor WesternSammendrag
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Forfattere
Bjørn Langerud Martin SandvikSammendrag
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Forfattere
Eivind Bauger Arnstein OrlundSammendrag
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Forfattere
Petter NilsenSammendrag
The cutting system described in this report is a form of selective cutting used in some mountain forest areas in Norway. The largest trees and most of the middle-sized trees are removed in the cutting. Dead and sick trees are also removed. Where the original stands are rather dense, a small clearcut area or opening can be made. For other places, the result can be more like an ordinary shelter wood cutting. The cutting system is flexible in this way. The main result, however, is one of a heavy selective cutting. This investigation deals with such remaining stands. The aim of this investigation was to study regeneration and production after selective cutting in Norway spruce forests. Thirty-two sample plots from two areas in the Trysil and Gausdal municipalities were investigated (Fig. 2). The sample plots were 400 m2 and the data collection was made 10 years after the cutting on an average. Data for some stands are presented in Table 1. All advance growth (trees less than 3 m of height) and seedlings that appeared after cutting were counted, and their height was measured. All larger trees in the remaining stand were measured for diameter. The sample plots were classified as one of 4 vegetation types: Melico-Piceetum aconitetosum, Eu-Piceetum dryopteridetosum, Eu-Piceetum myrtilletosum and Vaccinio-Pinetum. The advance growth varied a lot, both within and between the different vegetation types. On an average there were 470 plants per ha in Gausdal and 304 plants per ha in Trysil. Twelve and one-half per cent of the plants originated from layers. The largest number of plants were found at the M.-Pic. aconitetosum and Eu-Pic. dryopteridetosum types (Fig. 3). The favourable moisture condition under these types is probably the explanation for this. The number of plants increased slightly with increasing vertical distance from the timberline. The number of seedlings established after the cuttings are shown in Fig. 8. The tendency here is also that the moist vegetation types have the largest number of seedlings. Only seedlings from the 1983-seed year are separated by age. The age estimation on the other seedlings is uncertain. Regional reports show that there were good cone years in 1973, 1976 and 1983. There was moderate amount of cones in 1972, \"74, \"78 and \"80. Such moderate years are probably of minor importance for regeneration. The total number of plants under 3 m of height (for both advance growth and new regeneration) was an average of 820 per ha. 1680 plants per ha on the M.-Pic. aconitetosum type, 860 on Eu-Pic. dryopteridetosum type, 490 and 380 on the Eu-Pic. myrtilletosum and Vac.-Pinetum types, respectively. The zero-square percentage averaged 80 for all vegetation types (Fig. 9). Trees in most of the remaining stands had reacted positively after the cutting. The basal area increment in a three year period before registration was calculated in percent of the basal area increment three years before cutting. In Fig. 10 this relative increment is plotted against the percentage removal of basal area. Only a few stands lay under a line representing no reaction in the remaining stand. The variation in relative increment is large. It decreases with increasing removal of basal area. This factor explains however, only 15 % of the variation. Some objective criteria were used to pick out small plants supposed to be able to survive in the long run. The plants should be without crown competition from older trees, they should have a minimum height growth and they should be more than 10 cm of height. In this way the number of plants were reduced from 820 to 305 per ha and the zero square percentage rose from 80 to 90. The future development of the stands are estimated based on the height increment of the trees. The diameter distribution 40 years after cutting is shown in Fig. 12. The diameter distribution on the M.-Pic. aconitetosum type will be nearest the starting point on average. The two Eu-Piceetum types will tend against a two storied stand with little representation for diameters from 10-15 cm. The largest uncertainty concerns the amount of small plants that will be in the stands after a 40-year period. In this selective cutting method all advance growth must be saved. On the Eu-Pic. myrtilletosum type the cutting strength should be restricted to 50-60 % of standing basal area. Heavier cuttings can lead to grass invasion of the ground and large problems for seedling establishment. In addition, the production loss will be large in the remaining stand. On the moister vegetation types the possibilities of heavier cuttings are better because of a higher number of small plants. However, problems with weeds and shrubs can cause difficulties here.
Forfattere
Mette M. HandlerSammendrag
This report describes a square spacing experiment with Picea abies situated in the eastern part of Norway approximately 350 m above sea level. The following distances are represented: 1.2 m, 1.8 m, 2.4 m and 3.0 m. The experiment is a Latin square i.e. with 4 replications of each treatment. Each plot is 20 m x 20 m (Fig. 1). The experiment was measured in 1977 after heavy snow damage (Braastad 1979) and in 1984 at a top height of 14 m and total age 35 years (Table 1-3). The site index class (H40) is 20.6. The report deals with the measurement in 1984 and the increment period 1977-1984. The preliminary results show: The snow damage caused a heavy reduction in stem number in the 1.2 m spacing, moderate reduction in the 1.8 m spacing, while the two widest spacings were almost unaffected. In the last period the natural thinning has been negligible (Fig. 2). The top height does not seem to have been influenced by the spacing (Fig. 3). The basal area mean diameter and the diameter increment increase with increasing spacing (Fig. 4 and 6). The widest spacing has lost about 60 m3 per ha in standing volume in proportion to the other spacings and has a lower volume increment (Fig. 5 and 7). Diameter and diameter increment of the 800 largest trees per ha (according to diameter) increase with increasing spacing, but the differences are small (Fig. 4 and 6). Volume and volume increment of the 800 largest trees increase with increasing spacing (Fig. 5 and 7). The difference in standing volume between the widest and closest spacing is 24 m3 per ha. The experiment will be left unthinned in the future, and it is expected that the difference in volume production between the close and the widest spacing will not increase considerable. Time will show, whether the competition from the smaller trees in the close spacings will reduce the growth of the largest trees and thereby increase the tendency to increased growth of the largest trees with increasing spacing. The height to first live branch has increased by approximately 2 m since the measurement in 1977; from 1.9 m to 4.1 m in the closest spacing and from 0.5 m to 2.9 m in the widest spacing (Fig. 8). Branch diameter on bark was measured on the 15 largest trees on an inner plot of 15 m x 15 m. The horisontal diameter of the thickest branch in each whorl from 1.3 m to 5.0 m above ground was measured. The mean branch diameter of the thickest branches between 1.3 m and 5.0 m above ground increases with increasing spacing from 14.8 mm to 20.4 mm. Mean branch diameter of the thickest branch per tree increases from 19.1 mm for spacing 1.2 m to 24.3 mm for spacing 3.0 m (Fig. 9). On average for each spacing this branch diameter has increased maximum 1 mm, and for 95 % of the single trees less than 3 mm since the measurement in 1977. The diameter of the thickest branch is expected to have reached almost its final magnitude. The thickest branch is for 79 % of the trees situated 4.5 m or more above the ground. The planting distance should not exceed 2.4 m on this locality and with this provenance (Norwegian), if the maximum branch diameter is not to exceed 20 mm u.b. 5.0 m above ground.
Forfattere
Tore SkrøppaSammendrag
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Forfattere
Bjørn Langerud Martin Sandvik Anders SjøvoldSammendrag
Norway spruce seedlings were grown with three, peat based growth media (Table 1) subjected to three irrigation regimes in three forest nurseries in the Eastern part of Norway. The irrigation regimes were defined by the volume of liquid in the growth growth substrate one hour after irrigation and re-irrigation started when 20, 40 or 60 % of this volume of liquid was lost. The irrigation frequency and intensity was determined by the weight of specific multipot containers (Fig. 1). The results differed from what we expected from literature and laboratory studies: The deviations were mainly attributed to variation within the `experimental treatments`. Great variation was observed in bulk density, ash concentration and phase distribution in the growth media (Table 1, Figs. 2 and 3), and within, although not always between, irrigation regimes (Figs. 4, 5, 6 and 7). The experiment was further disturbed by the influence of growth media on germination (Table 2). The dry weight of seedlings did not relate to irrigation and growth media in an unique manner (Fig. 8): The variation in important factors and the improper control of the irrigation regimes made a discussion with respect to `average` growing conditions impossible. The results initiated a discussion on research strategies in the `applied sciences`, and the conclusion was towards more distinct criteria for the `applied` and the `science`. The variation and the unreliable routines induced this question: Which of the individual seedlings were under which of the irrigation regimes in which growth substrate and under which climate at which time and at which of the nurseries?. In conclusion, the variations in growth media properties, germination and growing routines have to be delt with in a better way than at present before a satisfactory growing control is achieved.
Forfattere
Kåre Olav Venn Arne Olav StuanesSammendrag
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