Epsilon Archive for Student Projects

Abstract

The society of today is dependent of secure transports and deliveries of electrical power. Interruptions in different activities because of fallen trees cost a great deal of money in form of reparations and claimed damages for transport companies and electrical suppliers. Fallen trees along some railway sections are a severe problem. For instance, to repair the damages of the storm of week 5 year 2002, costed 2 800 000 SEK for the line region of Hässleholm. Today, the Banverket railroad company has no norms in general for how close to the railway the forest is allowed to grow. Private forest owners manage the forest that is situated most close to the railway without any influences from Banverket. In some sections though, are security felling carried out approximately every tenth year, when the unstable trees most close
to the railway are removed. The work was carried out as a case study of the 55-kilometre Emmaboda-Karlskrona section. The criterion for the selected section was that it was supposed to be situated within the line region of Hässleholm and also be severely affected by wind throws. The aim of the study was to examine how big part of the section that would be regarded as a high-risk area of wind throws. Another motive was to study what the forest looked like from a viewpoint of the risk of wind throws. The result of the studied section will be the basis of a long term silvicultural suggestion to bring about more stable border zones most close to the railway, without silviculture of too high intense and expense.On the 14-kilometre section between Emmaboda and the border of Blekinge County, 30 percents of the forest consisted of risky stands. The reason for the great amount of high risk stands was that the forest mainly consisted of old spruce forest and that many landowners did not pay any real attention to the risk of wind throws in their silvicultural activities in the forest that borders the railway.
If the share of risky stands is to be decreased, more consideration must be taken to closely situated stands. Late thinning in higher border zones ought to be avoided and final felling should instead be carried out earlier.
The silviculture method, suggested to reach more stable edges of the stands, is about
managing a 25-metre broad zone of broadleaved trees between the railway and the other
stand. There is need for neither soil scarification nor planting within the border zone, since it is almost always naturally regenerated. A sparse regeneration is enough, since trees with high stability, not quality, is the target. The trees need a lot of space from an early age to be able to develop a robust root system and a coarse stem. It is therefore important with heavy and early thinnings.
If the suggested silviculture is implemented will the borders of the forest be approaching the ideal state in about 50 years. The scenario also shows that the problem with wind throws is not solvable during a too short period of time. The goal must be in the term of long-range. There may also be problems from an organisational viewpoint, due to the high number of landowners that are influenced and the long distance of the section that is affected. There will be a minor economical loss for the private landowners due to the small area that is touched
upon, and a small cost for Banverket as well. Out of one kilometre of railway is the impact only on 3 ha, since 15 metres on each side of the track shall be managed as a broadleavedOn the 14-kilometre section between Emmaboda and the border of Blekinge County, 30 percents of the forest consisted of risky stands. The reason for the great amount of high risk stands was that the forest mainly consisted of old spruce forest and that many landowners did not pay any real attention to the risk of wind throws in their silvicultural activities in the forest that borders the railway.
If the share of risky stands is to be decreased, more consideration must be taken to closely situated stands. Late thinning in higher border zones ought to be avoided and final felling should instead be carried out earlier.
The silviculture method, suggested to reach more stable edges of the stands, is about
managing a 25-metre broad zone of broadleaved trees between the railway and the other
stand. There is need for neither soil scarification nor planting within the border zone, since it is almost always naturally regenerated. A sparse regeneration is enough, since trees with high stability, not quality, is the target. The trees need a lot of space from an early age to be able to develop a robust root system and a coarse stem. It is therefore important with heavy and early thinnings.
If the suggested silviculture is implemented will the borders of the forest be approaching the ideal state in about 50 years. The scenario also shows that the problem with wind throws is not solvable during a too short period of time. The goal must be in the term of long-range.
There may also be problems from an organisational viewpoint, due to the high number of
landowners that are influenced and the long distance of the section that is affected. There will be a minor economical loss for the private landowners due to the small area that is touched upon, and a small cost for Banverket as well. Out of one kilometre of railway is the impact only on 3 ha, since 15 metres on each side of the track shall be managed as a broadleavedfringe. The 10 metres most close to the railway are never to comprise any bigger trees. The estimated total loss in soil expatiation value will in this study be approximately 27 000 SEK per kilometre railway.

Samhället kräver idag säkra transporter och elleveranser. Avbrott i verksamheter på grund av
nedfallna träd kostar transportbolag och elleverantörer stora belopp i form av reparationer och
skadestånd. Stormfällning utmed järnvägen är på vissa sträckor ett stort problem. Att åtgärda
skadorna efter stormen som drog in över södra Sverige under vecka 5, år 2002 kostade till
exempel 2 800 000 kr för banområde Hässleholm.
Banverket har idag inga generella normer för hur nära järnvägsrälsen skogen får växa. Privata
skogsägare sköter den järnvägsnära skogen utan påverkan från Banverket. På vissa sträckor
sker det dock säkerhetsavverkningar ca vart tionde år, då de mest instabila träden närmast
järnvägen avverkas.
Arbetet genomfördes som en fallstudie av den 5,5 mil långa sträckan Emmaboda-Karlskrona.
Urvalskriteriet var att sträckan skulle ligga inom Hässleholms banområde samt var hårt
drabbad av stormfällda träd.
Studiens syfte var att undersöka hur stor del av den studerade sträckan som hade stor risk för
stormfällning. Ett annat skäl var att studera hur skogen ser ut och sköts med hänsyn till risken
för stormfällning. Resultatet från den studerade sträckan ligger sedan till grund för
skogsskötselförslag för att åstadkomma stabilare kantzoner närmast järnvägen, utan alltför
intensiv och kostsam skötsel.
På den 14 km långa sträckan mellan Emmaboda och gränsen mot Blekinge bestod hela 30
procent av skogen riskbestånd. Anledning till den stora andelen riskbestånd var att skogen
huvudsakligen bestod av gammal granskog och att många markägare inte tog någon särskild
hänsyn till risken för stormfällning vid skötsel av skog som gränsar mot järnvägen.
Om andelen riskbestånd ska minskas måste större hänsyn tas till närliggande bestånd vid
avverkningar. Sena gallringar i täta höga kantzoner bör undvikas, och slutavverkning bör
istället tidigareläggas.
Den föreslagna skötseln för att få stabilare beståndskanter går i stora drag ut på att sköta en 25
meter bred lövzon mellan järnvägen och det övriga beståndet. Kantzonen behöver varken
markberedas eller planteras eftersom det i de flesta fall blir någon form av självföryngring. En
gles föryngring är tillräcklig eftersom det är stabila träd och inte kvalitet som eftersträvas. För
att utveckla ett kraftigt rotsystem och grov stam kräver träden mycket utrymme redan från en
tidig ålder. Det är därför viktigt att röja och gallra hårt i kantzonen.
Om den föreslagna skötseln implementeras närmar sig skogskanterna ett idealt tillstånd efter
ca 50 år. Scenariot visar även att problemet med stormfällning inte går att lösa under en allt
för kort tidsperiod, utan målet måste vara långsiktigt. Organisatoriskt kan det uppstå problem
på grund av det stora antalet markägare och den långa sträckan som berörs. Det blir dock en
liten ekonomisk förlust för den enskilde markägaren på grund av den lilla ytan som berörs och
likaledes en liten kostnad för banverket. På en km järnväg är det totalt 3 ha som berörs
eftersom det är 15 meter på var sida om spåret som skall skötas som ett lövbryn. De tio
närmsta meterna skall ju alltid vara utan större träd. Den totala markvärdesförlusten blir då ca
27000 kr per km järnväg.