| 1. |
- Holmström, Emma, et al.
(author)
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Detection of Retention Trees on Clearcuts, a 50-Year Perspective
- 2020
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In: Open Journal of Forestry. - : Scientific Research Publishing, Inc.. - 2163-0429 .- 2163-0437. ; 10
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Journal article (peer-reviewed)abstract
- Changes in clearcut management over time were evaluated using aerial photographs taken between 1960 and 2010. Temporal changes were analysed in two different climatic zones in Sweden: a typical boreal forest zone (the coast of Västerbotten County), and the hemi-boreal zone of southern Sweden (represented by Kronoberg County). The study covers the periods before and after the paradigm shift in Swedish forestry caused by the equalization of the production and nature conservation objectives specified in the first paragraph of the Swedish Forestry Act. Photographs were processed to determine clearcut size and shape and to register solitary retention trees and groups of retention trees. Small but significant changes in clearcut size were detected over time. The number of retention trees increased over time, a result that was also found in other studies using different methodologies. The results demonstrate that measurable structural changes have occurred in Swedish forests over the 25 years since the paradigm shift. Results from this study also show that digital detection of green tree retention could be a future complement to field inventory and monitoring.
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| 2. |
- Lariviere, Delphine
(author)
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Old trees in young forests : Biodiversity management in planted conifer forests in southern Sweden
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Sweden’s long history of intensive forest management has made conservation measures in the forest landscape necessary to counteract the loss of biodiversity. Retention forestry has been systematically practiced since 1993 and consists of the preservation of different structures and habitats to create and maintain suitable habitats for species that do not cope well with clear-cutting. Many of these stands are now entering thinning. The aim of this thesis was to evaluate how choices in forest management contribute to biodiversity with the example of tree retention in thinning or through the choice of rotation length. First, gap cutting around old oaks (Quercus robur) in a Norway spruce (Picea abies) forest was investigated as an example of retention management in southern Sweden (I + II). We found that oaks contributed to the diversity of the stand due to their specific associated species. The removal of Norway spruce next to the oaks at the time of thinning boosted oak vitality and increased the species richness and abundance of vascular plants and saproxylic beetles due to increased temperature and light exposure, especially oak-associated beetles. In another study, the effect of forest age was investigated on four taxa: birds, bryophytes, lichens, and vascular plants in Norway spruce and Scots pine (Pinus sylvestris) stands (III). The older stands, both of Norway spruce and Scots pine, had a distinct species community of understorey species and epiphytes. In Norway spruce stands, older stands typically had more deadwood, which could have favoured bryophytes and birds by providing specific habitats and resources. Older Scots pine stands had the highest lichen species richness, but the implementation of other understorey species was impaired by the dominance of a few competitive dominating species. Finally, we explored the potential of using a canopy height model (CHM) to find and map retention trees (IV). We concluded that this method is a cost-effective solution to map and characterise past retention efforts to facilitate forest management and ensure that old trees are kept throughout the present and subsequent rotations. Our results indicate that this method can discern retention areas to an accuracy of 66%. The findings in this thesis provide knowledge on how the management of retention trees and the choice of rotation length can support biodiversity and provide guidelines for forest management so that their positive effects on forest biodiversity can be maintained over time.
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| 3. |
- Lariviere, Delphine, et al.
(author)
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Release of retained oaks in Norway spruce plantations. A 10-year perspective on oak vitality, spruce wood production and ground vegetation
- 2021
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In: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 480
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Journal article (peer-reviewed)abstract
- This study explores the decade-long effects of release cutting around old retained oaks (Quercus robur L.) in a Norway spruce (Picea abies L. Karst) stand that was 33 year old when thinned. The impacts on both nature conservation values and spruce wood production were evaluated in a randomized block design. To release oaks from competition, stems of Norway spruce were cut around 33 oaks, in three different treatments: high release (HR), medium release (MR) and no release (NR). Trees within a circular sample plot (15 m radius from the oak) were measured at time of treatment and 10 years after. The treatment effects on stand development, oak vitality and understory vegetation were evaluated after ten years, using tree diameter, height measurements, oak crown and tree structure estimates as well as ground vegetation surveys. Release cutting did not impact spruce production within the sample plot, and given that there were no other obvious sources of spruce suppression in the stand, we speculate that release cutting has little to no impact at the stand scale. Oak crowns in the control plots (NR) became smaller after ten years, while the crowns expanded and colonized the gap in the release treatments. Simultaneously, the amount of dead wood in the crown increased among oaks in the control treatment, indicating dieback. Cover and species richness of vascular plants in the understory were significantly higher in the HR and MR treatments compared to NR. These results suggest that the creation of relatively wide gaps (greater than 2 m) around retained oak crowns is one efficient approach to maintain their conservation values in a spruce dominated stand on a longer time frame. This will allow oaks to expand their crowns, increase their vitality and increase species richness and diversity of plants under the canopy. The economic loss of creating large gaps instead of no gaps may be negligible since the overall spruce production was not affected within 15 m of each oak.
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| 4. |
- Lariviere, Delphine, et al.
(author)
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Ten years after: Release cutting around old oaks still affects oak vitality and saproxylic beetles in a Norway spruce stand
- 2023
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In: Agricultural and Forest Entomology. - : Wiley. - 1461-9555 .- 1461-9563. ; 25, s. 416-426
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Journal article (peer-reviewed)abstract
- It is often suggested to release oaks (Quercus robur) from competition, to ensure their survival and boost their conservational value. However, few studies have explored how long-lasting this effect is and how it affects saproxylic beetles.Ten years after cutting, we investigated effects of different release cutting levels (high, medium, and no release) around 140-year-old retained oaks in a commercial forest with Norway spruce (Picea abies).We evaluated oak vitality using crown and dead wood measurements. Saproxylic beetles were caught in window traps, identified to species level, and grouped according to their association with oak and/or Norway spruce.Released oaks had more light, higher temperatures, greater crown growth, and less dead wood in the crown compared to the no-release control.After 10 years we still found a higher abundance of oak-associated beetles and higher overall species richness of saproxylic beetles in the released oaks. Beetle species composition significantly differed between released oaks and control.We suggest avoiding planting trees beneath retained oaks when regenerating conifer forests and to proceed with conservation management during subsequent thinning by removing regeneration under the oak crowns. We emphasize the benefits of monitoring the retained oaks to maintain tree vitality, habitat quality, and insolation.
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| 5. |
- Petersson, Lisa, et al.
(author)
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Conifer tree species and age as drivers of epiphytic lichen communities in northern European production forests
- 2022
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In: Lichenologist. - 0024-2829 .- 1096-1135. ; 54, s. 213-225
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Journal article (peer-reviewed)abstract
- The epiphytic lichen species richness and community composition was compared for 600 living trees distributed within the interior of 60 Scots pine and Norway spruce monoculture stands in southern Sweden. A higher species richness, and more unique species, was found on trees of Scots pine than of Norway spruce, and distinctive communities were associated with the two tree species. Lichen species composition also shifted between the 30-, 55- and 80-year-old stands, although there was no significant difference in species richness between the different age classes. Tree species and age of the stand explained most of the variation in community composition (41%), with additional variance explained by lichen proximity to the ground (6%) and aspect (1%) (northern/southern side of trunk). Scots pine and Norway spruce share many attributes, such as both being conifers with acidic bark properties and having a similar geographical distribution in Fennoscandia. However, our study showed that species richness and community composition can nevertheless diverge in stands dominated by these two tree species. Since the occurrence of red-listed species was low in these stands, we suggest that 80-year rotations are not long enough for the occurrence of the many rare and specialized lichen species that require old forest structures and long forest continuity in this region.
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| 6. |
- Petersson, Lisa, et al.
(author)
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Potential implications of shortened rotation length for forest birds, bryophytes, lichens and vascular plants: An example from southern Swedish production forests
- 2024
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In: PLoS ONE. - 1932-6203. ; 18
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Journal article (peer-reviewed)abstract
- The rotation lengths of intensively managed production forests may be altered to achieve a variety of goals, with correspondingly implications for biodiversity. Here we consider the potential implications of shortened rotation times for biodiversity in planted monocultures of the two most common production tree species in Sweden, Scots pine (Pinus sylvestris) and Norway spruce (Picea abies). To do so we surveyed bird, bryophyte, epiphytic lichen and vascular plant diversity in 80 and 55-year-old stands; stand ages which approximate present-day and potential future rotation lengths in this region respectively. We found clear differences in the species communities of the 55 compared to the 80-year-old stands for both understory species and epiphytes, but not for birds. Nevertheless, bird species richness was still highest in the 80-year-old Norway spruce dominated stands. Dead wood amount was also highest the 80-year-old Norway spruce stands. Highest species richness of epiphytic lichens was found in 80-year-old Scots pine stands. However, 55-year-old Scots pine stands had a higher understory species richness and diversity than the older Scots pine stands, including a larger number of open land species. The 80-year-old forest stands examined may be considered old with respect to production forest rotation lengths in Sweden but are relatively young when comparing stand ages of unmanaged natural forest stands. Nevertheless, our results indicate that shortening the rotation time of Scots pine and Norway spruce, in this part of Sweden from 80 to 55 years, could have important consequences for forest biodiversity. These consequences are primarily inferred from the likely implications from shortened rotations for lichens community composition and diversity in both Norway spruce and Scots pine stands, as well as impacts on understory plant species in Norway spruce stands.
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