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Masterredovisning Biologi


Exjobbsredovisning på master-nivå, biologi

27 okt 2021
13:00 - 14:00
Zoologen, Medicinaregatan 18A/Zoom
Ytterligare information

Boel Nilsson, Naturvårdsbiologi, 60 hp

"To be or not to be - The question of long-term retention persistence in Swedish forestry"

Handledare: Frank Götmark
Examinator: Johan Uddling



Retention forestry is an approach to forest management which integrates biodiversity conservation with forest production. The model provides an alternative to conventional clear cutting, with the core aim of conserving important structures and organisms during harvest. Retention requirements are an integrated part of Swedish forestry – yet it has never before been investigated how these retained areas develop over time. Do they persist, or do they disappear? Aiming to bring some clarity to this question, the current study has been conducted in cooperation with the Swedish Forest Agency, using original Polytax inventory material as a basis for follow-up. The 134 identified retention areas were re-localised stepwise over approximately a ten-year period, through aerial orthophotos in ArcGIS. A subsample of 30 areas spread across southwestern Sweden were also revisited in the field. The study of retention area persistence was done both based on area estimates of absolute size, and based on observations. Permutation tests evaluated the difference in area size between the beginning and the end of the follow-up period. A generalised linear model was fitted to the observational data, distinguishing which area properties that could explain the differences in retention persistence. While the differences in absolute size were found to be small, and overall non-significant (p <0.05), the observational data suggests that between 20-30 % of the retention areas have decreased over the studied time period. County affiliation was found to be the main contributing factor of difference. Larger areas and protection zones appear to have decreased to a higher degree, compared to smaller areas and habitats with specific values. Our results indicate that the common assumption of retention area permanency may be erroneous. It could entail negative consequences for the functionality of these areas, which play an important role in the conservation of biodiversity in the modern forestry ecosystem.