| 1. |
- Drössler, Lars, et al.
(författare)
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Simulated transformation of even-aged Norway spruce stands to multi-layered forests: an experiment to explore the potential of tree size differentiation
- 2014
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Ingår i: Forestry. - : Oxford University Press (OUP). - 0015-752X .- 1464-3626. ; 87, s. 239-248
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Tidskriftsartikel (refereegranskat)abstract
- The study investigated the possibility to transform normal young Norway spruce (Picea abies (L.) Karst) forests to develop more heterogeneous stand structures, aiming for multi-layered forest in the long run. On three sites in central and south Sweden, 60 per cent of stand basal area was removed by thinning mainly medium-sized trees and leaving the smallest and the largest trees. Over the next 50 years, future stand development was simulated using a single-tree growth model. Simulations were run with and without ingrowth. An additional ingrowth scenario after soil preparation was tested. Basal area was kept between 10 and 20 m(2) ha(-1) during simulations. Projected stem wood production for the next 50 years was one-third lower compared with conventional thinning regimes. After 50 years, a multi-layered forest structure was indicated for the boreal sites in central Sweden, but not for the site in south Sweden.
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| 2. |
- del Río, Miren, et al.
(författare)
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Emerging stability of forest productivity by mixing two species buffers temperature destabilizing effect
- 2022
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Ingår i: Journal of Applied Ecology. - : John Wiley & Sons. - 0021-8901 .- 1365-2664. ; 59:11, s. 2730-2741
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Tidskriftsartikel (refereegranskat)abstract
- The increasing disturbances in monocultures around the world are testimony to their instability under global change. Many studies have claimed that temporal stability of productivity increases with species richness, although the ecological fundamentals have mainly been investigated through diversity experiments. To adequately manage forest ecosystems, it is necessary to have a comprehensive understanding of the effect of mixing species on the temporal stability of productivity and the way in which it is influenced by climate conditions across large geographical areas. Here, we used a unique dataset of 261 stands combining pure and two-species mixtures of four relevant tree species over a wide range of climate conditions in Europe to examine the effect of species mixing on the level and temporal stability of productivity. Structural equation modelling was employed to further explore the direct and indirect influence of climate, overyielding, species asynchrony and additive effect (i.e. temporal stability expected from the species growth in monospecific stands) on temporal stability in mixed forests. We showed that by adding only one tree species to monocultures, the level (overyielding: +6%) and stability (temporal stability: +12%) of stand growth increased significantly. We identified the key effect of temperature on destabilizing stand growth, which may be mitigated by mixing species. We further confirmed asynchrony as the main driver of temporal stability in mixed stands, through both the additive effect and species interactions, which modify between-species asynchrony in mixtures in comparison to monocultures. Synthesis and applications. This study highlights the emergent properties associated with mixing two species, which result in resource efficient and temporally stable production systems. We reveal the negative impact of mean temperature on temporal stability of forest productivity and how the stabilizing effect of mixing two species can counterbalance this impact. The overyielding and temporal stability of growth addressed in this paper are essential for ecosystem services closely linked with the level and rhythm of forest growth. Our results underline that mixing two species can be a realistic and effective nature-based climate solution, which could contribute towards meeting EU climate target policies.
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| 3. |
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| 4. |
- Drössler, Lars
(författare)
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Bestandesentwicklung in zwei plenterartig strukturierten Buchen-Edellaubholz-Mischbeständen in Thüringen
- 2015
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Ingår i: Jahrestagung - Deutscher Verband Forstlicher Forschungsanstalten, Sektion Ertragskunde. - 1432-2609.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Zwei Untersuchungsflächen in einem ungleichaltrigen Buchenwald mit hohem Edellaubholzanteil wurden nach 15 Jahren erneut aufgenommen. Sie haben eine besondere historische Waldnutzung ohne Überführung in den Altersklassenwald hinter sich. Während die typischen Plenterwälder im Hainich nahezu reine Buchenbestände sind, ist der untersuchte Wald durch einen hohen Bergahornanteil gekennzeichnet. Er ist ein Musterbeispiel für Buchen-Edellaubholz-Mischbestände als Waldentwicklungsziel auf Muschelkalkstandorten in der kollinen Höhenstufe, wie sie in Waldbauprogrammen beschrieben werden. Ziel der waldbaulichen Untersuchung war es, die Durchmesserverteilung und Entwicklung der Bergahornbäume zu beschreiben und Möglichkeiten einer nachhaltigen Edellaubholzwirtschaft zu diskutieren. Grundlage der Untersuchung sind die Inventuraufnahmen auf zwei representativ ausgewählten Versuchsflächen im Frühjahr 2000 und 2015. In der ersten Versuchsfläche wurden seit 30 Jahren Lü- ckenhiebe angelegt, in denen sich bereits reichlich anfliegende Bergahornverjüngung etabliert hatte und zum Zeitpunkt der Erstaufnahme bis zum Stangenholzstadium herangewachsen war. Der Vergleich mit der zweiten Versuchsfläche zeigt, dass stärkere punktuelle Engriffe als die klassische Plenternutzung notwendig sind, um zukünftig neue Individuen des Bergahorns in die Oberschicht einwachsen zu lassen. Eine strikte einzelstammweise Nutzung in der zweiten Versuchsfläche führte zu nahezu vollständiger Dominanz der Rotbuche in der Unter- und Mittelschicht.
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| 5. |
- Drössler, Lars
(författare)
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Development and Traits of Wolf Trees in Scots Pine (Pinus sylvestris L.): A Literature Review
- 2016
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Ingår i: Baltic Forestry. - 1392-1355. ; 22, s. 181-188
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Forskningsöversikt (refereegranskat)abstract
- This article reviewed studies from Germany, Russia, Lithuania, Sweden and Finland about wolf trees in Scots pine (Pinus sylvestris L.) forests and examined the definition of a wolf tree. In addition, we analyzed the main traits and parameters of these trees, such as lower crown ratio, more conical stem taper, partly deformed crown, and thicker and longer branches. The analysis revealed changes in the definition of a wolf tree during the XX century and different definitions over various regions. The differences between wolf trees and common trees were found in growth patterns, stress sensitivity and genetics. Also this article reviewed several possible reasons for the occurrence of wolf trees in forest stands.
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| 6. |
- Drössler, Lars, et al.
(författare)
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Early development of pure and mixed tree species plantations in Snogeholm, southern Sweden
- 2015
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 30, s. 304-316
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Tidskriftsartikel (refereegranskat)abstract
- There is a lack of experimental studies comparing the forest production of mixed tree species stands and monocultures. As a case study, in 1994 an experiment was established in an afforestation landscape in southern Sweden with 66 plots: 18 planted with single tree species (including most native Swedish trees, plus Populus and Larix hybrids) and 48 with various non-replicated mixtures. Fifteen years after planting, stand growth did not differ significantly between the mixtures and the monocultures. However, the monocultures did exhibit a higher variation in growth levels relative to the moderate but comparatively consistent growth levels exhibited by the mixtures; particularly those comprised of more than two species. A specific analysis of mixtures containing either the tree species Picea abies or Quercus robur and their corresponding monocultures demonstrated the importance of the tree species admixed as a determinant of production outcomes early in the rotation. In the case of P. abies, tree species mixtures tended to reduce production, whereas in the case of Q. robur, mixtures tended to increase production. In addition no consistent differences in the mean height and mean diameter growth of P. abies and Q. robur between mixtures and monocultures were detected. A major conclusion is that adding more than two species did not increase stand volume growth.
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| 7. |
- Drössler, Lars, et al.
(författare)
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Effects of crown architecture and stand structure on light absorption in mixed and monospecific Fagus sylvatica and Pinus sylvestris forests along a productivity and climate gradient through Europe
- 2018
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 106, s. 746-760
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Tidskriftsartikel (refereegranskat)abstract
- When tree-species mixtures are more productive than monocultures, higher light absorption is often suggested as a cause. However, few studies have quantified this effect and even fewer have examined which light-related interactions are most important, such as the effects of species interactions on tree allometric relationships and crown architecture, differences in vertical or horizontal canopy structure, phenology of deciduous species or the mixing effects on tree size and stand density.In this study, measurements of tree sizes and stand structures were combined with a detailed tree-level light model (Maestra) to examine the contribution of each light-related interaction on tree- and stand-level light absorption at 21 sites, each of which contained a triplet of plots including a mixture and monocultures of Fagus sylvatica and Pinus sylvestris (63 plots). These sites were distributed across the current distribution of these species within Europe.Averaged across all sites, the light absorption of mixtures was 14% higher than the mean of the monocultures. At the whole community level, this positive effect of mixing on light absorption increased as canopy volume or site productivity increased, but was unrelated to climate. At the species population or individual tree levels, the mixing effect on light absorption resulted from light-related interactions involving vertical canopy structure, stand density, the presence of a deciduous species (F.sylvatica), as well as the effects of mixing on tree size and allometric relationships between diameter and height, crown diameter and crown length.The mixing effects on light absorption were only correlated with the mixing effects on growth for P.sylvestris, suggesting that the mixing effects on this species were driven by the light-related interactions, whereas mixing effects on F.sylvatica or whole community growth were probably driven by non-light-related interactions.Synthesis. The overall positive effect of mixing on light absorption was the result of a range of light-related interactions. However, the relative importance of these interactions varied between sites and is likely to vary between other species combinations and as stands develop.
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| 8. |
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| 9. |
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| 10. |
- Drössler, Lars, et al.
(författare)
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Growth and yield of mixed versus pure stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) analysed along a productivity gradient through Europe
- 2015
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Ingår i: European Journal of Forest Research. - : Springer Science and Business Media LLC. - 1612-4669 .- 1612-4677. ; 134, s. 927-947
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Tidskriftsartikel (refereegranskat)abstract
- Mixing of complementary tree species may increase stand productivity, mitigate the effects of drought and other risks, and pave the way to forest production systems which may be more resource-use efficient and stable in the face of climate change. However, systematic empirical studies on mixing effects are still missing for many commercially important and widespread species combinations. Here we studied the growth of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in mixed versus pure stands on 32 triplets located along a productivity gradient through Europe, reaching from Sweden to Bulgaria and from Spain to the Ukraine. Stand inventory and taking increment cores on the mainly 60-80 year-old trees and 0.02-1.55 ha sized, fully stocked plots provided insight how species mixing modifies the structure, dynamics and productivity compared with neighbouring pure stands. In mixture standing volume (+12 %), stand density (+20 %), basal area growth (+12 %), and stand volume growth (+8 %) were higher than the weighted mean of the neighbouring pure stands. Scots pine and European beech contributed rather equally to the overyielding and overdensity. In mixed stands mean diameter (+20 %) and height (+6 %) of Scots pine was ahead, while both diameter and height growth of European beech were behind (-8 %). The overyielding and overdensity were independent of the site index, the stand growth and yield, and climatic variables despite the wide variation in precipitation (520-1175 mm year(-1)), mean annual temperature (6-10.5 A degrees C), and the drought index by de Martonne (28-61 mm A degrees C-1) on the sites. Therefore, this species combination is potentially useful for increasing productivity across a wide range of site and climatic conditions. Given the significant overyielding of stand basal area growth but the absence of any relationship with site index and climatic variables, we hypothesize that the overyielding and overdensity results from several different types of interactions (light-, water-, and nutrient-related) that are all important in different circumstances. We discuss the relevance of the results for ecological theory and for the ongoing silvicultural transition from pure to mixed stands and their adaptation to climate change.
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