Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad
The interest for alternative forest regeneration methods increased significantly during the 1990´s after 50 years dominance of the clear-cutting system (Holgén & Hånell 2000). One reason for this was that clear-cutting was being more and more questioned by different envi-ronmental organizations and...
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| Formato: | Otro |
| Lenguaje: | sueco sueco |
| Publicado: |
2007
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| Acceso en línea: | https://stud.epsilon.slu.se/11997/ |
| _version_ | 1855571980111052800 |
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| author | Tjernell, Tomas |
| author_browse | Tjernell, Tomas |
| author_facet | Tjernell, Tomas |
| author_sort | Tjernell, Tomas |
| collection | Epsilon Archive for Student Projects |
| description | The interest for alternative forest regeneration methods increased significantly during the 1990´s after 50 years dominance of the clear-cutting system (Holgén & Hånell 2000). One reason for this was that clear-cutting was being more and more questioned by different envi-ronmental organizations and because the forest sector for economical reasons wanted to find cheaper ways to regenerate forests. In the beginning of the 1990´s two shelterwood experi-ments were established in a joint effort by Svenska Cellulosa Aktiebolaget (SCA) and the Dept of Silviculture, Swedish University of Agricultural Sciences (SLU). The experiments include various forms of cutting and shelterwood densities and represent productive spruce forests in central and north Sweden (Roggsjön in the province of Medelpad and Skikkis-jöberg in the province of Västerbotten, respectively ). The experiment next to Roggsjön has been reported earlier in three MSc theses, and is also the focus of this thesis.
The experiment includes two adjacent spruce stands with elements of birch and is located east of the lake Roggsjön (62, 4˚ degrees N, 216 above sea level) about 60 km west of Sundsvall. The stands are managed and administered by SCA. At the time of the shelterwood cutting, in early 1994, both stands were about 90 years old and contained approximately 300m3/ha (Andersson, 1995). The experiment was designed in randomized blocks with two blocks and four shelterwoods: 400 Dominant trees (400 H), 250 Dominant trees (250 H), 400 Co- dominant trees (400 MH), 250 Co- dominant trees (250 MH).
Thirteen years later windthrow damage were extensive among the co- dominant trees, fore-most in the sparser shelterwood (250 MH), where 70 % of the trees had blown down. In the denser shelterwood (400 MH) approx. 40 % had blown down whereas the windthrow dam-ages where fairly small in the shelterwoods with dominant trees, (approx. 10 %). A strong correlation was stated between strength of cutting and redundancy. In all shelterwoods the spruce regeneration met the requirements of the Swedish Forestry Act (SVL) concerning natural regeneration. The mean height was over one meter in all the shelterwoods, which partly was due to the high amount of advance spruce regeneration. The occurrence of de-ciduous trees was high in all the shelterwoods except for the densest one (400 H). The mean height of the deciduous trees was significantly lower in the shelterwoods with dominant trees.
The species composition in the field and bush layers varied greatly between the shelterwoods with dominant and co-dominant trees. Under the cover of the dominant trees there was hardly any bush layer whilst under the co- dominant trees there were in places plenty of raspberry and rosebay. High occurrence of raspberry and rosebay were found to have a nega-tive effect on the height increment of the spruce regeneration. In the field layer the dwarf-shrubs where found almost exclusively under the cover of the dominant trees whereas bracken and low-herbs were found under the co- dominant ones. In the bottom layer the main part of the moss indicated mesic-dry conditions, and sphagnum was found exclusively under the dominating shelter trees. |
| format | Otro |
| id | RepoSLU11997 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish swe |
| publishDate | 2007 |
| publishDateSort | 2007 |
| record_format | eprints |
| spelling | RepoSLU119972017-11-14T10:03:09Z https://stud.epsilon.slu.se/11997/ Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad Tjernell, Tomas Forest injuries and protection The interest for alternative forest regeneration methods increased significantly during the 1990´s after 50 years dominance of the clear-cutting system (Holgén & Hånell 2000). One reason for this was that clear-cutting was being more and more questioned by different envi-ronmental organizations and because the forest sector for economical reasons wanted to find cheaper ways to regenerate forests. In the beginning of the 1990´s two shelterwood experi-ments were established in a joint effort by Svenska Cellulosa Aktiebolaget (SCA) and the Dept of Silviculture, Swedish University of Agricultural Sciences (SLU). The experiments include various forms of cutting and shelterwood densities and represent productive spruce forests in central and north Sweden (Roggsjön in the province of Medelpad and Skikkis-jöberg in the province of Västerbotten, respectively ). The experiment next to Roggsjön has been reported earlier in three MSc theses, and is also the focus of this thesis. The experiment includes two adjacent spruce stands with elements of birch and is located east of the lake Roggsjön (62, 4˚ degrees N, 216 above sea level) about 60 km west of Sundsvall. The stands are managed and administered by SCA. At the time of the shelterwood cutting, in early 1994, both stands were about 90 years old and contained approximately 300m3/ha (Andersson, 1995). The experiment was designed in randomized blocks with two blocks and four shelterwoods: 400 Dominant trees (400 H), 250 Dominant trees (250 H), 400 Co- dominant trees (400 MH), 250 Co- dominant trees (250 MH). Thirteen years later windthrow damage were extensive among the co- dominant trees, fore-most in the sparser shelterwood (250 MH), where 70 % of the trees had blown down. In the denser shelterwood (400 MH) approx. 40 % had blown down whereas the windthrow dam-ages where fairly small in the shelterwoods with dominant trees, (approx. 10 %). A strong correlation was stated between strength of cutting and redundancy. In all shelterwoods the spruce regeneration met the requirements of the Swedish Forestry Act (SVL) concerning natural regeneration. The mean height was over one meter in all the shelterwoods, which partly was due to the high amount of advance spruce regeneration. The occurrence of de-ciduous trees was high in all the shelterwoods except for the densest one (400 H). The mean height of the deciduous trees was significantly lower in the shelterwoods with dominant trees. The species composition in the field and bush layers varied greatly between the shelterwoods with dominant and co-dominant trees. Under the cover of the dominant trees there was hardly any bush layer whilst under the co- dominant trees there were in places plenty of raspberry and rosebay. High occurrence of raspberry and rosebay were found to have a nega-tive effect on the height increment of the spruce regeneration. In the field layer the dwarf-shrubs where found almost exclusively under the cover of the dominant trees whereas bracken and low-herbs were found under the co- dominant ones. In the bottom layer the main part of the moss indicated mesic-dry conditions, and sphagnum was found exclusively under the dominating shelter trees. Intresset för alternativa skogsföryngringsmetoder ökade väsentligt under 1990-talet efter 50 års dominans av kalhyggesbruk (Holgen & Hånell 2000). Anledningen till det ökade intresset var att kalhyggesbruket började ifrågasättas alltmer av olika miljöorganisationer samt att man inom skogsbruket av ekonomiska skäl ville finna billigare sätt att föryngra skogen. I början av 1990-talet anlades två stora försök med högskärmar på Svenska Cellulosa Aktiebolagets (SCA) marker i samarbete med Institutionen för skogsskötsel vid SLU. I dessa experiment jämförs olika huggningsformer och skärmtätheter i södra Norrland (Roggsjön i Medelpad) och norra Norrland (Skikkisjöberg i Västerbotten). Försöket vid Roggsjön har tidigare studerats i tre examensarbeten och utgör också grund för detta arbete. Försöksområdet utgörs av två närliggande granbestånd med inslag av björk och återfinns öster om sjön Roggsjön (62,4 grader N, 216 m ö h.) ca 6 mil väster om Sundsvall. Bestånden återfinns under Medelpads förvaltning vid SCA. Vid tidpunkten för skärmhuggningen, våren 1994 var båda bestånden ca 90 år och innehöll ca 300m3/ha enligt beståndsregistret (Andersson, 1995). Försöket utformades som ett randomiserat blockförsök med två block och fyra försöksled/skärmar enligt följande: 400 Härskande träd (400 H), 250 Härskande träd (250 H), 400 Medhärskande träd (400 MH), 250 Medhärskande träd (250 MH). Tretton år senare var avgångarna i form av vindfällen omfattande bland de medhärskande skärmträden, främst i den glesare skärmen (250 MH), där 70 % av träden blåst ner. I den tätare skärmen (400 MH) hade ca 40 % av träden fallit omkull medan avgångarna var ganska små i skärmarna med härskande träd, (ca 10 %). Ett starkt samband kunde konstateras mellan huggningsstyrka och avgång. Granföryngringen var i samtliga skärmtyper godkänd enligt SVL:s krav på naturlig föryngring och medelhöjden var över en meter i samtliga skärmar vilket delvis beror på den rikliga beståndsföryngring som fanns innan skärmarna ställdes. Lövträdsförekomsten var hög i alla skärmar utom den tätaste (400 H). Lövträdens medelhöjd var dock betydligt lägre i skärmarna med härskande träd. Skillnaden i vegetationens sammansättning var markant mellan skärmarna med härskade och medhärskande träd. Buskskikt förekom knappt under de härskande trädens kronor medan det bitvis var rikligt med hallon och mjölkört under de medhärskande träden. Hög förekomst av hallon och mjölkört visade sig ha en negativ effekt på granplantornas höjdtillväxt. I fältskiktet hittades riset nästan uteslutande i skärmar av härskande träd medan ekbräken och lågörter återfanns i skärmarna av medhärskande träd. I bottenskiktet dominerade friskmossorna, medan vitmossor uteslutande hittades i skärmarna av härskande träd. 2007-08-21 Other NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/11997/1/tjernell_t_171114.pdf Tjernell, Tomas, 2007. Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad. UNSPECIFIED, Umeå. Umeå: (S) > Dept. of Forest Ecology and Management <https://stud.epsilon.slu.se/view/divisions/OID-241.html> urn:nbn:se:slu:epsilon-s-8780 swe |
| spellingShingle | Forest injuries and protection Tjernell, Tomas Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title | Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title_full | Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title_fullStr | Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title_full_unstemmed | Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title_short | Vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i Medelpad |
| title_sort | vindfällning, tillväxt och plantuppslag i en 13-årig granskärm i medelpad |
| topic | Forest injuries and protection |
| url | https://stud.epsilon.slu.se/11997/ https://stud.epsilon.slu.se/11997/ |