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1989
Forfattere
Sverre SkoklefaldSammendrag
The experimental area is situated in southeast Norway (1119\" E.Gr., 6055\" N.), about 500 m above sea level (Fig. 1). Eu-Piceetum myrtilletosum was the dominating vegetation type, but also species belonging to Eu-Piceetum dryopteridetosum were found.The main aim of the investigation was to examine natural regeneration, both under a shelterwood of 225 Norway spruce trees per hectare and on a 50 m wide clear-cut area. 2/2 bare-root spruce seedlings were planted under shelterwood and on the clear-cut area. Spot scarification was carried out here and in an adjacent stand.The seed fall was registered continuously by seed traps, and all seeds were X-ray analysed. Seeds with embryos were classified as filled and seeds without embryos as empty. Spot scarification was carried out manually within a 50 x 80 cm frame in the second and fifth growing seasons after the regeneration cutting.The humus layer including the ground vegetation was removed without disturbing the mineral soil beneath and turned upside down. The dynamics of seedling establishment were examined by marking the seedlings with plastic sticks of different colours each year. Thus it was possible to estimate the number as well as the height of seedlings of different ages during the research period.To estimate the annual diameter increment of shelter trees and trees in an adjacent stand, two bore cores were taken from each sample tree just before the final cutting. The height development of the same trees was estimated by measuring the top shoots of each year after the cutting. By use of volume functions the volume of each single tree was calculated, and the volume increment was determined as the difference between volumes in different years.Four seed years (1964, 67, 69 and 73) contributed to the natural regeneration, but seed production was modest in three of these. Although the seed supply was abundant in 1973, years with minimal or no production of germinable seeds dominated (Fig. 3). Even though the seed supply during the investigation period was relatively modest new seedlings were found in scarified spots after every seed year.However, the seedling mortality was high (Figs. 4 and 5). The best results were obtained under shelterwood, but even there only 50% of the spots had one or more seedlings 3 years after the removal of shelter trees (Fig. 7). The seedlings grew slowly below shelterwood. Thus, the oldest seedlings, which germinated in the third grow season after the cutting, attained a height of only 17 cm during 11 years (Fig. 8).On the clear-cut area the height growth was considerably better. On the other hand, both the number of seedlings and the percentage of scarified spots with seedlings were lower. In intact vegetation only a sparse element of advance growth was found, both under shelterwood and on clear-cut area. In both cases the total number of seedlings increased modestly until the shelter trees and the surrounding spruce stand were cut. However, 9 years after the final cut it was found that the number of seedlings had increased greatly on the initially clear-cut area, but only to a small extent where the shelterwood was removed (Table 9).The zero-square percentages (the number of 2 x 2 m squares without seedlings as percentage of all squares surveyed) were 41 and 59 respectively, which indicated a future volume production about 90% and 75% of normal (Braathe 1953). Probably, the main explanation of the lower number of seedlings on the initially shelterwood plot was that the greater part of seedlings germinating after the excellent seed year of 1973 died after the release cutting.On the clear-cut area the advance growth attained a height of about 3 m during 22 years (Fig. 10). At the same time the plantation was about 3.5 m high (Fig. 11). The time saved by planting correspond to about 2 years. A dense shelterwood of spruce considerably reduces the height growth of seedlings. However, the advance growth, which had been suppressed for 13 years, reacted quickly with increased growth after the release.At the end of the investigation period the difference in height between the plantation on the clearcut area and the released advance growth corresponded to about 7 years of growth. The loss of time with natural regeneration may be rather high, especially if the main part of the seeds are spread late in the regeneration period.On the clear-cut area, new seedlings were only about 50 cm high 22 years after the cutting. Probably most of these had germinated in 1974. The plantation attained a corresponding height after 6 years. After planting, both under shelterwood and on clear-cut areas, the seedling mortality was rather low.The shelterwood greatly reduced the height growth of seedlings. After 13 years, when the shelter trees were removed, the mean height was about 95 cm, versus 170 cm without shelter. After release, the seedlings reacted quickly with increased growth. The time lost by planting under shelter corresponded to about 5 years. The diameter increment of the shelter trees increased quickly and culminated in sixth year after the shelterwood cutting. During the remaining 7 years of the shelterwood phase the diameter increment remained high (Fig. 13).The shelterwood cutting did not seem to affect the height growth of the trees. The height growth of both the shelter trees and the trees in the adjacent stand decreased in the investigation period (Fig. 15). The annual volume increment during the shelterwood phase (1963-75) was 3.38 m3 per hectare, and increment of single trees was much higher in the shelterwood than in the adjacent stand (Fig. 16).The shelter trees were divided into three groups according to the diameter at breast height before the shelterwood cutting. Both the volume increment and the cone production were highest in the group of trees with the largest diameter. In cases where the shelter trees react positively to the cutting, on fields which are easy to regenerate naturally, the shelterwood method is interesting. The main drawbacks of the method are the increased danger of windthrow and a high seedling mortality associated with the release cuttings.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Tor J. JohansenSammendrag
Det er ikke registrert sammendrag
1988
Forfattere
Jarle BerganSammendrag
In the spring 1955 an experimental plot with 6 provenances of Scots pine from Norway was laid out in a fjord district at 69°04\"N - 60 m a.s.l.: Prov. 1. Målselv - 69°N, 0-150 m a.s.l. Prov. 2. Grovfjord - 68°40\"N, 0-150 m a.s.l. Prov. 3. Skjomen - 68°15\"N, 0-150 m a.s.l. Prov. 4. Saltdal - 66°55\"N, 0-150 m a.s.l. Prov. 5. Halsa - 63°05\"N, 0-150 m a.s.l. Prov. 6. Rindal - 63°05\"N, 0-150 m a.s.l. The plot was laid out on a clear-cut in a birch forest. In the surrounding area, the pine occurs spontaneously only as scattered single trees. The plot (90 m x 90 m) was divided in 36 squares (15 m x 15 m), and each provenance repeated 6 times. The spacing of plants was 1,5 m x 1,5 m. Each provenance was represented by 600 plants. Prov. 3 has been transferred about 100 km (aerial line) from south to north, Prov. 4 about 240 km. Fig. 1 shows the reduction in the survival percentage in the years 1955 to 1985. At the total age of 34 years, a strong correlation has been found between the survival percentage and the northern latitude of the provenances. In Fig. 8 is shown that the total production is related to the number of plants per hectare. The number of plants per hectare is decreasing with decreasing latitude of the provenances (Table 6). Provenances transferred 100 km or more from south to the north are not to be recommended by plantations in the fjord districts in Troms. They probably give less total production, larger diameters of stems and branches (Table 5), and lower values in the relationship of H/D (Height in m/Diameter in cm) than the most northern provenance (Table 6). The main reason is the lower density of plants caused by lower survival percentages by the southern provenances. However, the trees of the two most southern provenances (Prov. 5 and 6) have also revealed considerably less height growth than the others (Table 3). Prov. 1 and 2 originate respectively from inland and fjord districts. The results from the actual experiment show that the provenance from the inland of Troms has to be preferred by planting of Scots pine in the actual fjord district. In 1956 another experiment was laid out in the same area. This experiment included also comparison between Prov. 1 and 2 (Bergan 1987). The results at the total age of 27 years confirm the conclusions about these two provenances in this report.
Forfattere
Liv G. HineSammendrag
Bakgrunnen for forsøksresultatene fra Vestlandet er følgende flater: Erdalsdalen, 7 vekstsesonger Hamra og Skiple, 5 vekstsesonger Frotveit, 11 vekstsesonger Valdersnes, 12 vekstsesonger. Den oppgitte alderen er tidsrommet mellom etablering av forsøket og den siste registreringen på feltet. Marktypen var røsslyngmark på Valdersnes og Frotveit. Forsøket på Hamra ble lagt på en hogstflate i ei bratt nordøstvendt li, der blåbær utgjør den vanligste arten i feltskiktet. På Skiple ligger feltet i et gammelt bjørkebestand i ei nordvestvendt li. I Erdalsdalen kan marktypen karakteriseres som oremark. Følgende plantetyper og plantemetoder ble brukt: Barrot - hakkeplanting Kopparfors (pluggplanter) - hullpipe med og uten flekking og Pottiputki. En sammenlikning mellom de to plantetypene barrotplanter og pluggplanter, viser at barrotplantene i de fleste tilfelle har hatt minst avgang. Bare ved sommerplanting, spesielt i juni, har resultatet vært dårligere enn for pluggplantene. Også når det gjelder høydetilvekst har barrotplantene generelt sett vært best. Dette hovedresultatet går igjen på alle forsøksflater der barrotplanter er med. Det kan således ikke påvises noen effekt av feltenes beliggenhet og markbonitet. Bare plantetidspunktet synes å påvirke forholdet mellom de to plantetypene. For pluggplantene ble det brukt tre plantemetoder. Hullpipe med flekking, det vil si fjerning av vegetasjonsdekket på planteplassen, har i de fleste tilfeller gitt gode resultater både med hensyn til tilslag og vekst. Plantemetoden hullpipe uten flekking har så og si uten unntak ført til størst avgang og minst vekst. Resultatene viser at en flekkstørrelse på 9 dm2 fører til signifikant større overleving sammenliknet med planting uten flekking. Flekking av plantestedet har hatt den samme gunstige virkningen på alle marktyper og ved alle plantetidspunkter. Resultatene viser således at hullpipe med flekking definitivt er den beste plantemetoden for pluggplantene. I denne undersøkelsen har bruk av barrotplanter gitt best resultat. Det beste alternativet til barrotplantene ser ut til å være pluggplanter plantet om våren på avflekkete planteplasser. Det er på grunnlag av disse forsøkene ikke mulig å gi anbefalinger om plantetype/-metoder på ulike boniteter.
Forfattere
Torbjørn OkstadSammendrag
Geometric properties, wood properties and quality were measured in a sample of pulpwood logs from Central Norway. The average middle diameters with bark of butt logs, middle logs and top logs were 17.2 cm, 16.6 cm and 10.6 cm respectively (Table 1). The frequency distribution of the diameters is given in Fig. 1. The average log length in this sample is 4.32 m (Table 2). The frequency distribution of the log length is illustrated in Fig. 2. Log taper was calculated to be 1.40 cm/m on the average (Table 3). Log taper increases with increasing diameter (Fig. 3). The ovality of the logs increases with increasing diameter (Fig. 4). The average basal area quotient is calculated to be 0.88 (Table 4). Double bark thicknesses of the butt logs, middle logs and top logs in this sample are 10.9 mm, 10.3 mm and 7.2 mm respectively (Table 5). Average bark volume percentages are 11.7%, 12.0% and 13.2% respectively. The corresponding figures measured according to special rules by the measurement society are 11.2%, 12.4% and 14.6% respectively (Table 6). The average log volume with bark of this sample is 75.3 dm3 (Table 7). The frequency distribution of the log volume is given in Fig. 7. The proportion of knotwood and compression wood of the total wood volume is on the average 2.0% and 5.8% respectively (Tables 8 and 9). The proportion of decayed wood is 3.3% (Table 10). The measurement society classified 86.6% of the total volume as first class quality, 6.6% as second class quality and 6.8% as cull (Table 11). The growth ring width in this sample was on the average 1.3 mm (Table 12). The basic density of the logs is given in Table 13 and was on the average 415.0 kg/m3. The relationship between basic density decreases with increasing growth ring width. The moisture content (per cent of green weight) at the time of delivery is highest in the winter and lowest in the late summer (Fig. 11).
Forfattere
Jon BekkenSammendrag
Skogbrukslovens formålsparagraf sier at det skal legges `vekt på skogens betydning som livsmiljø for planter og dyr`. Formuleringen innebærer at man i planlegging og gjennomføring av hogst og andre skogbrukstiltak skal innarbeide hensyn til bl.a. fuglelivet. Rapporten gjennomgår status og biotopkrav til de fugleartene som påvirkes negativt og dagens skogsdrift, samt hvilke hensyn som bør tas i skogbruket. De viktigste hensynene er: 1. Sett igjen osp for spetter og hullrugere, og la nye ospeholt utvikles. La en del osper og andre lauvtrær (særlig bjørk) dø en naturlig død. Ingen skadeinsekter som betyr noe utvikles i lauvtrær, mens f.eks. den sjeldne hvitryggspetten lever av vedborende insektlarver. Over 25 andre fuglearter benytter gamle spettehull. Spetter og andre hullrugere utgjør ca. 1/3 av fugleartene i skog. 2. Registrér hekkelokaliteter til spesielle arter: a) De store kvistreirbyggerne, særlig kongeørn, havørn, fiskeørn, hønsehauk, musvåk og vepsevåk. Unngå hogst i en radius av 200 m omkring reir av kongeørn og havørn, og i en radius av 50 m omkring reir av de andre artene. Forstyrrelser må unngås i hekketiden i et mye større område. Tillat at nye hekkelokaliteter for rovfugl, med store, gamle trær, utvikles. b) Hubro: Ved bergskrenter der hubro hekker, bør hogst ikke foretas i en radius på minst 50 m og aktivitet nærmere enn 500 m bør ikke forekomme i tiden mars - september. c) Trane og smålom: Behold disse myrstrekningene intakte og unngå å legge skogsbilveier i nærheten. Ferdsel og forstyrrelse må unngås i hekketiden, og en brem av skog beholdes omkring myrene. 3. Innslag av våtmark og sumpskog beholdes og hogges kun forsiktig (eller spares). Dette er ofte svært artsrike lokaliteter. 4. Hensyn til storfugl: Registrér spillplasser og beitetrær, og unngå helst hogst i disse områdene. Også områdene omkring selve leiken må holdes mest mulig intakte. Ungene er avhengige av sumpskog i oppveksten! 5. Unngå hogst i følgende lavproduktive miljøer: Berglendte koller og rabber, skrenter og rasmark. Også kløfter og bekkeraviner bør spares, selv om boniteten her kan være bedre. Øyer på myr og i vann kan være viktige lokaliteter og bør likeledes unntas fra skogsdrift. 6. Sett igjen kanter mot myr, elver og vann. Nærmere studier pågår om ønskelig bredde av slike kanter.
Forfattere
Jarle Bergan Trygve EideSammendrag
During 1979-82 seven field tests were carried out at 69°N in Norway (Table 1). Four tests included seeding of Pinus sylvestris under plastic cones (K) and funnels (T) compared to seeding without cover (S) and plug planting (P) (see Fig. 1). Three field tests included seeding of Picea abies in funnels located in virgin vegetation in birch forests on the hillsides. Here the seeding in funnels was compared to plug planting. The plant percentage means the percentage of seeds forming plants up to the first autumn. The germination percentage of the seed used has been 92.5% to 95.0%. The number of pine seeds per spot was four seeds in cones and funnels, and 15 seeds in open sowings on scarified patches. Six spruce seeds were used in each funnel in the tests on the hillside. The survival percentage means the percentage of cones, funnels or patches with one or more living plants. The vegetation type of the areas of pine plots is Vaccinio-Pinetum boreale, and on spruce areas Eu-Piceetum abietis-subass. dryopteridetosum. The seeding in cones (Method K) has turned out to be a reliable method with high survival percentage and relatively good height development, especially the first years with seedlings inside the cones. The consumption of seed is very low in relation to open sowings (Method S). The plant percentage in cones has in average been about 80% compared to 53% in open sowings (Table 2). However, there is a risk of cones being removed by persons, birds, and strong wind. Method S has shown more varying results as regards plant percentage and survival percentage. However, by using 25 seeds per patch instead of 15 seeds, the possibility of increasing the survival percentage in years with unfavourable climatic conditions, would have been quite good. Bergan (1957 and 1981) found high positive correlation between the number of plants per patch and the survival percentage. Also plug planting is a highly acceptable regeneration method. On the other hand, sowing in funnels (Method T) has been less successful in all tests both regarding survival percentage and height development. The choice of regeneration method between the methods K, S and P at pine areas at these northern latitudes depends on the supply of seed, economic calculations, and administration conditions.
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
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.