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En pollenanalytisk studie av råhumusprofiler från Säröhalvön i norra Halland

Jönsson, Emma (2003) In Examensarbeten i geologi vid Lunds universitet
Department of Geology
Abstract (Swedish)
Populärvetenskaplig sammanfattning: Särö Västerskog och Särö Nordanskog i norra Halland utgör de mest värdefulla och artrikaste skogsbestånden längs hela västkusten. De är klassade som riksintresse för naturvården. Den biologiska mångfalden är mycket stor och i skogarna förekommer många sällsynta och rödlistade arter. Som exempel kan nämnas den sällsynta idegranen (Taxus baccata). Särö täcks av relativt tunna jordlager. Inga mäktiga lagerföljder från mossar eller kärr finns i området som kan förse oss med material för pollenanalytiska studier. Därför har vi varit tvungna att använda oss av råhumusprofiler som sträcker sig bakåt i tiden ca 2000 år.

Vegetationens sammansättning varierar över tiden beroende på t.ex. klimatförändringar,... (More)
Populärvetenskaplig sammanfattning: Särö Västerskog och Särö Nordanskog i norra Halland utgör de mest värdefulla och artrikaste skogsbestånden längs hela västkusten. De är klassade som riksintresse för naturvården. Den biologiska mångfalden är mycket stor och i skogarna förekommer många sällsynta och rödlistade arter. Som exempel kan nämnas den sällsynta idegranen (Taxus baccata). Särö täcks av relativt tunna jordlager. Inga mäktiga lagerföljder från mossar eller kärr finns i området som kan förse oss med material för pollenanalytiska studier. Därför har vi varit tvungna att använda oss av råhumusprofiler som sträcker sig bakåt i tiden ca 2000 år.

Vegetationens sammansättning varierar över tiden beroende på t.ex. klimatförändringar, naturlig succession och mänsklig påverkan. Spår av mänskliga aktiviteter visas bl.a. genom närvaron av pollen från ogräs och sädeslag, och av en ökad andel gräspollen när skogarna öppnades och ängsmarker bildades.

För att studera vegetationsförändringarna på Särö har tre råhumusprofiler, två markprover och en kort borrkärna tagits upp för pollenanalytiska studier. För att göra jordproverna rena från organiskt material gjordes en pollenpreparering. Detta är en teknik som genom bl.a. tillsats av NaOH 10% (natriumhydroxid) och HF (fluorvätesyra) rengör proverna från organiskt och minerogent material så att pollenkorn och sporer kan studeras i mikroskop.

Både Särö Västerskog och Särö Nordanskog har en gång i tiden bestått av öppen gräsmark/ljunghed. Särö Västerskogs nordöstra del har troligtvis varit en klassisk ljunghed som har svedjats kontinuerligt. Idegran bör ha funnits i området under de senaste 200 åren men detta kunde dock inte bevisas av pollenanalysen. Träd som t.ex. björk, ek, tall och al har senare vuxit upp och trängt undan den öppna vegetationen. En tät blandskog med bl.a. tall och ek bildades så småningom och denna vegetationstyp täcker Särö än idag. (Less)
Abstract
The aim of this study was to make a pollenanalytical investigation of mor humus-profiles from the peninsula of Särö in northern Halland. The coastal forests are well preserved in this area and often hold a very interesting flora and fauna with many red-listed species. One can for example mention the rare species yew (Taxus baccata). The forests contain a mixture of deciduous and coniferous trees like oak (Quercus), beech (Fagus) and pine (Pinus). The forests have been spared from cutting for a long time probably much because there has been only one owner at a time.

The area that was investigated contains two smaller forest-areas, Särö Västerskog, which is a nature reserve, and Särö Nordanskog. This study has been directed towards... (More)
The aim of this study was to make a pollenanalytical investigation of mor humus-profiles from the peninsula of Särö in northern Halland. The coastal forests are well preserved in this area and often hold a very interesting flora and fauna with many red-listed species. One can for example mention the rare species yew (Taxus baccata). The forests contain a mixture of deciduous and coniferous trees like oak (Quercus), beech (Fagus) and pine (Pinus). The forests have been spared from cutting for a long time probably much because there has been only one owner at a time.

The area that was investigated contains two smaller forest-areas, Särö Västerskog, which is a nature reserve, and Särö Nordanskog. This study has been directed towards analysing mor humus-profiles in order to reconstruct the history of vegetation over the last 2000 years. Specific issues are the magnitude of human impact on the vegetation and for how long time yew has grown in the area. The collecting of samples was done with help of iron chutes and a russian sampler. The pollen analysis was made on four profiles, two from Särö Västerskog and two from Särö Nordanskog. Two samples of recent litter and ground mosses, that were taken in a yew dominated stand, were also analysed. The mor humus-profiles was not dated independently, but an approximate age could be established by correlation with other profiles from the same area that has recently been 14C-dated.

The most common pollen grains in the profiles are Betula (birch), Pinus (pine), Quercus (oak), Ulmus (alder), Poaceae (grass) and Calluna (heather). The result shows that the area has been open pasture or grassland before the profiles started to develop. After some time various trees and bushes were established and these made it difficult for the herbs and grasses to grow. The pastures may have been small open patches. The vegetation was dominated by Calluna, which has been a characteristic element on the west-coast of Sweden, has also occurred on Särö. There is clear evidence that heather and heath-burning has occurred on Särö, especially from the sampling site Särö Västerskog 4. The rest of the area has been forest and more or less barren cliffs. The yew grew in the area as early as in the 17’th century and has remained there since then. Proof for the establishment of yew was not found in the profiles. This can depend on various things, for example that pollen from yew is poorly preserved, or that it has low pollen production. (Less)
Please use this url to cite or link to this publication:
author
Jönsson, Emma
supervisor
organization
alternative title
A pollenanalytical study of mor humus-profiles from the peninsula of Särö in northern Halland, Sweden
year
type
H1 - Master's Degree (One Year)
subject
keywords
Halland, Särö, råhumusprofil, pollenanalys, geologi, geografi
publication/series
Examensarbeten i geologi vid Lunds universitet
report number
167
language
Swedish
id
2342453
date added to LUP
2012-12-22 16:08:55
date last changed
2012-12-22 16:08:55
@misc{2342453,
  abstract     = {The aim of this study was to make a pollenanalytical investigation of mor humus-profiles from the peninsula of Särö in northern Halland. The coastal forests are well preserved in this area and often hold a very interesting flora and fauna with many red-listed species. One can for example mention the rare species yew (Taxus baccata). The forests contain a mixture of deciduous and coniferous trees like oak (Quercus), beech (Fagus) and pine (Pinus). The forests have been spared from cutting for a long time probably much because there has been only one owner at a time. 

The area that was investigated contains two smaller forest-areas, Särö Västerskog, which is a nature reserve, and Särö Nordanskog. This study has been directed towards analysing mor humus-profiles in order to reconstruct the history of vegetation over the last 2000 years. Specific issues are the magnitude of human impact on the vegetation and for how long time yew has grown in the area. The collecting of samples was done with help of iron chutes and a russian sampler. The pollen analysis was made on four profiles, two from Särö Västerskog and two from Särö Nordanskog. Two samples of recent litter and ground mosses, that were taken in a yew dominated stand, were also analysed. The mor humus-profiles was not dated independently, but an approximate age could be established by correlation with other profiles from the same area that has recently been 14C-dated.

The most common pollen grains in the profiles are Betula (birch), Pinus (pine), Quercus (oak), Ulmus (alder), Poaceae (grass) and Calluna (heather). The result shows that the area has been open pasture or grassland before the profiles started to develop. After some time various trees and bushes were established and these made it difficult for the herbs and grasses to grow. The pastures may have been small open patches. The vegetation was dominated by Calluna, which has been a characteristic element on the west-coast of Sweden, has also occurred on Särö. There is clear evidence that heather and heath-burning has occurred on Särö, especially from the sampling site Särö Västerskog 4. The rest of the area has been forest and more or less barren cliffs. The yew grew in the area as early as in the 17’th century and has remained there since then. Proof for the establishment of yew was not found in the profiles. This can depend on various things, for example that pollen from yew is poorly preserved, or that it has low pollen production.},
  author       = {Jönsson, Emma},
  keyword      = {Halland,Särö,råhumusprofil,pollenanalys,geologi,geografi},
  language     = {swe},
  note         = {Student Paper},
  series       = {Examensarbeten i geologi vid Lunds universitet},
  title        = {En pollenanalytisk studie av råhumusprofiler från Säröhalvön i norra Halland},
  year         = {2003},
}