Skötsel av älgskadade bestånd
Sweden has today the highest moose (Alces alces) population in the world. The population has been very high since the late seventies and in the beginning of the eighties there was a big "moose explosion". The main food source for moose during the winter is young pine (Pinus sylvestris) and birch (Be...
| Autor principal: | |
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| Formato: | L3 |
| Lenguaje: | sueco Inglés |
| Publicado: |
SLU/Dept. of Silviculture
2005
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| Materias: |
| _version_ | 1855572123107459072 |
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| author | Skoog, Johan |
| author_browse | Skoog, Johan |
| author_facet | Skoog, Johan |
| author_sort | Skoog, Johan |
| collection | Epsilon Archive for Student Projects |
| description | Sweden has today the highest moose (Alces alces) population in the world. The population has been very high since the late seventies and in the beginning of the eighties there was a big "moose explosion". The main food source for moose during the winter is young pine (Pinus sylvestris) and birch (Betula spp.). The high moose population has therefore lead to high damage on pine forests over big areas. These forests are now about to be commercial thinned for the first time. Because of that the difficult, but important question of how to manage these damaged forests in the best way arises.
The aim of this work was to investigate if there were some alternative management programs for the damaged forests which were better than those used today. Therefore the following three questions were formulated:
- Is it profitable to take away all the damaged stems at the first commercial thinning, to be able to manage an undamaged "repaired" stand?
- Should you clear cut the stands with the most severe damage earlier than normal and instead regenerate with spruce (Picea abies) if the site index is good?
- Is it profitable to cross-cut damaged stands differently?
This exam work was done as an assignment to Bergvik Skog. It was performed as an inventory and a following calculation of the material, but it was also done as a literature study. The inventory took place at the "Nornområdet" in Bergslagen where there already is a moose project going on. Twenty-three randomly chosen pine stands with a height around 10 meters were inventoried. The invented data included both forest data and data of the moose damage. The result showed that most stands had serious damage, in average 46.9 % of the pine had viewable damage.
A simulation of eight different management alternatives was done for each stand. These were conducted with ProdMod2, which is a computer program that can calculate the production on a stand. For the economic calculations there was constructed a program in Excel in which net values and net present values could be calculated. The values were used to evaluate which management alternative that gave the highest economical value for each stand.
The results showed that over a certain limit of damage it was not profitable to manage the forest according to the normal management alternative. At moderate damage it was best to mark the damaged trees before the first commercial cut, to be able to take away all the damaged stems. At higher levels of damage it was better to cut down the forest earlier than normal, because the expected increase in value in the end of the rotation period will not occur. At levels of damage higher than approximately 55 %, the stands should not only be cut down earlier but the pines should also be cross-cut differently. By making pulpwood of the lowest 3 meters the moose damage will disappear from the remaining part of the stem, which then can be handled as undamaged. In stands with high share of damage but with a lower share of pine the forest should be allowed to grow as normal. But at the cuttings the pine should be cross-cut differently with a 3 meters pulp wood log in the lowest part. |
| format | L3 |
| id | RepoSLU12745 |
| institution | Swedish University of Agricultural Sciences |
| language | swe Inglés |
| publishDate | 2005 |
| publishDateSort | 2005 |
| publisher | SLU/Dept. of Silviculture |
| publisherStr | SLU/Dept. of Silviculture |
| record_format | eprints |
| spelling | RepoSLU127452017-10-19T11:08:59Z Skötsel av älgskadade bestånd Management of stands damaged by moose Skoog, Johan ekonomi gallring produktionsförluster slutavverkning skötselprogram tall älgskador Sweden has today the highest moose (Alces alces) population in the world. The population has been very high since the late seventies and in the beginning of the eighties there was a big "moose explosion". The main food source for moose during the winter is young pine (Pinus sylvestris) and birch (Betula spp.). The high moose population has therefore lead to high damage on pine forests over big areas. These forests are now about to be commercial thinned for the first time. Because of that the difficult, but important question of how to manage these damaged forests in the best way arises. The aim of this work was to investigate if there were some alternative management programs for the damaged forests which were better than those used today. Therefore the following three questions were formulated: - Is it profitable to take away all the damaged stems at the first commercial thinning, to be able to manage an undamaged "repaired" stand? - Should you clear cut the stands with the most severe damage earlier than normal and instead regenerate with spruce (Picea abies) if the site index is good? - Is it profitable to cross-cut damaged stands differently? This exam work was done as an assignment to Bergvik Skog. It was performed as an inventory and a following calculation of the material, but it was also done as a literature study. The inventory took place at the "Nornområdet" in Bergslagen where there already is a moose project going on. Twenty-three randomly chosen pine stands with a height around 10 meters were inventoried. The invented data included both forest data and data of the moose damage. The result showed that most stands had serious damage, in average 46.9 % of the pine had viewable damage. A simulation of eight different management alternatives was done for each stand. These were conducted with ProdMod2, which is a computer program that can calculate the production on a stand. For the economic calculations there was constructed a program in Excel in which net values and net present values could be calculated. The values were used to evaluate which management alternative that gave the highest economical value for each stand. The results showed that over a certain limit of damage it was not profitable to manage the forest according to the normal management alternative. At moderate damage it was best to mark the damaged trees before the first commercial cut, to be able to take away all the damaged stems. At higher levels of damage it was better to cut down the forest earlier than normal, because the expected increase in value in the end of the rotation period will not occur. At levels of damage higher than approximately 55 %, the stands should not only be cut down earlier but the pines should also be cross-cut differently. By making pulpwood of the lowest 3 meters the moose damage will disappear from the remaining part of the stem, which then can be handled as undamaged. In stands with high share of damage but with a lower share of pine the forest should be allowed to grow as normal. But at the cuttings the pine should be cross-cut differently with a 3 meters pulp wood log in the lowest part. Sverige har idag världens högsta älgstam. Allt sedan slutet av 1970 talet har stammen varit väldigt hög och i början av 80-talet inträffade den sk. ”älgexplosionen”, då antalet älgar steg kraftigt. Älgens huvudsakliga föda utgörs vintertid av tall och björk. Den höga älgpopulationen har därför medfört att stora arealer tallskog har blivit svårt skadad av älgbete. När nu dessa skogar närmar sig tiden för första gallring uppstår den svåra men viktiga frågan hur de ska skötas på bästa sätt. Syftet med detta examensarbete var att försöka se om det för älgskadad skog kan finnas alternativa skötselprogram, vilka är bättre än dagens skötsel. Följande tre frågeställningar formulerades därför: - Är det ekonomiskt fördelaktigt att gallra bort de skadade stammarna vid en första gallring för att sedan kunna satsa på ett oskadat ”reparerat” bestånd? - Bör man avveckla de mest skadade bestånden i förtid och istället satsa på en ny generation av granskog där ståndortsindex talar för detta? - Är det lönsamt att aptera skadade bestånd annorlunda? Examensarbetet utfördes på uppdrag av Bergvik Skog. Det gjordes som en inventering med efterföljande beräkningar av material men även som en litteraturstudie. Inventeringen förlades till det sk. ”Nornområdet” i Bergslagen, där ett älgprojekt pågår sedan tidigare. Tjugotre slumpade avdelningar i höjd runt 10 meter inventerades i avseende både på såväl skogliga data som älgskador. Inventeringen visade att de flesta avdelningar hade kraftiga skador av älg, i medel hade 46.9 % av alla tallar synliga skador. För varje avdelning utfördes simuleringar av 8 olika behandlingsprogram. Dessa utfördes med ProdMod2, vilket är ett dataprogram som kan beräkna produktionen för ett bestånd. Till de ekonomiska beräkningarna konstruerades ett beräkningsprogram i Excel i vilket nettovärden och nettonuvärden erhölls. Värdena användes för att bestämma vilka behandlingsprogram som var bäst för respektive avdelning. Resultaten visade att över en viss gräns av skador är det inte försvarbart att sköta skogen enligt normala skötselmallar. Vid måttliga skador är det bäst att ”stämpla” de skadade träden innan första gallringen för att sedan gallra bort alla skadade stammar. Vid högre skadenivåer är det bättre att slutavverka skogen tidigare än normalt, då den förväntade värdeökningen i slutet av omloppstiden uteblir. Vid skadeandelar högre än ca 55 % bör tallarna apteras annorlunda i samband med den tidigarelagda slutavverkningen. Genom att aptera massaved av den nedersta tremetersbiten försvinner älgskadan, varvid resten av stammen kan hanteras som oskadad. I avdelningar med hög skadeandel men med mindre tallandel bör skogen tillåtas växa enligt normala modeller, men tallen bör vid avverkning apteras med 3 meter massaved i botten. SLU/Dept. of Silviculture 2005 L3 swe eng https://stud.epsilon.slu.se/12745/ |
| spellingShingle | ekonomi gallring produktionsförluster slutavverkning skötselprogram tall älgskador Skoog, Johan Skötsel av älgskadade bestånd |
| title | Skötsel av älgskadade bestånd |
| title_full | Skötsel av älgskadade bestånd |
| title_fullStr | Skötsel av älgskadade bestånd |
| title_full_unstemmed | Skötsel av älgskadade bestånd |
| title_short | Skötsel av älgskadade bestånd |
| title_sort | skötsel av älgskadade bestånd |
| topic | ekonomi gallring produktionsförluster slutavverkning skötselprogram tall älgskador |