| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
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| 6. |
- 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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| 7. |
- Drössler, Lars
(författare)
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Heterogen skog : för komplex för skogsbruk och tillämpad skogsforskning?
- 2016
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Ingår i: Fakta. Skog. - 1400-7789.
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Annan publikation (populärvet., debatt m.m.)abstract
- Svensk skogsforskning är inriktad på skötsel av trädslagsrena bestånd. I södra Sverige utgörs dock skogarna i relativt hög grad av blandskogar med olika sammansättningar. Kunskaperna om hur sådana skogar sköts är inte tillräcklig. Det finns många andra kombinationer av trädslag och beståndsstrukturer som är mindre typiska än tall–gran eller gran–björk och även mindre utforskade. Andra exempel på kunskapsbrist att sköta bestånd är skog med någon form av självföryngring. Om den tillämpade skogsforskningen inte har samma resurser för att utforska blandskog eller flerskiktad skog som bestånd med bara ett trädslag, då finns ett behov av ett mer generellt koncept för att också sköta heterogena bestånd. Praktiska råd i skogen för de som ibland arbetar med mer heterogena bestånd, av mindre vanlig typ: Börja med att kartlägga diameterfördelningen av beståndet, använd Heureka Beståndsvis och ha koll på självföryngring ifall du vill uppskatta framtidens beståndsutveckling och skötsel! Sedan kan man göra jämförelser med fallstudier beskrivna i litteraturen.
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| 8. |
- Drössler, Lars, et al.
(författare)
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Mixing of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) enhances structural heterogeneity, and the effect increases with water availability
- 2016
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 373, s. 149-166
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Tidskriftsartikel (refereegranskat)abstract
- The mixing of tree species with complementary ecological traits may modify forest functioning regarding productivity, stability, or resilience against disturbances. This may be achieved by a higher heterogeneity in stand structure which is often addressed but rarely quantified. Here, we use 32 triplets of mature and fully stocked monocultures and mixed stands of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) located along a productivity and water availability gradient through Europe to examine how mixing modifies the stand structure in terms of stand density, horizontal tree distribution pattern, vertical stand structure, size distribution pattern, and variation in tree morphology. We further analyze how site conditions modify these aspects of stand structure. For this typical mixture of a light demanding and shade tolerant species we show that (i) mixing significantly increases many aspects of structural heterogeneity compared with monocultures, (ii) mixing effects such as an increase of stand density and diversification of vertical structure and tree morphology are caused by species identity (additive effects) but also by species interactions (multiplicative effects), and (iii) superior heterogeneity of mixed stands over monocultures can increase from dry to moist sites. We discuss the implications for analyzing the productivity, for modelling and for the management of mixed species stands. (C) 2016 Elsevier B.V. All rights reserved.
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| 9. |
- Drössler, Lars, et al.
(författare)
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Natural Regeneration in a Multi-Layered Pinus sylvestris-Picea abies Forest after Target Diameter Harvest and Soil Scarification
- 2017
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Forest management in Sweden can be characterized by even-aged silviculture heavily relying on three established harvest regimes: clearcutting, the seed-tree method, and the shelterwood system. Less intense, small-scale retention harvest systems such as single tree and group selection harvest are rarely used. In addition, natural regeneration dynamics without enrichment planting have barely been studied. Consequently, this study examined natural regeneration establishment in a multi-layered Pinus sylvestris-Picea abies forest stand in southwest Sweden after target diameter harvesting and soil scarification. The creation of forest canopy gaps had a positive effect on total seedling density five years after harvest, mainly due to a significantly higher number of Betula pendula individuals. Seedling density of more desirable tree species suitable for continuous cover forestry such as Fagus sylvatica, Quercus petraea and Picea abies also increased substantially in gaps when compared to pre-harvest conditions or the unharvested plots. In contrast, soil scarification did not increase the number of seedlings of desired tree species due to a significant decrease in Picea abies abundance. Soil moisture and gap size significantly improved Betula pendula seedling establishment while a larger number of Quercus petraea seedlings were observed in Vaccinium myrtillus patches. We conclude that canopy gaps are beneficial under the encountered stand conditions to initiate forest regeneration, and that soil scarification without the timely occurrence of a mast year of desired tree species is not effective in the type of forest studied.
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| 10. |
- Drössler, Lars, et al.
(författare)
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Over- and Underyielding in Time and Space in Experiments with Mixed Stands of Scots Pine and Norway Spruce
- 2018
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Pine-spruce forests are one of the commonest mixed forest types in Europe and both tree species are very important for wood supply. This study summarized nine European studies with Scots pine and Norway spruce where a mixed-species stand and both monocultures were located in an experimental set-up. Overyielding (where growth of a mixed stand was greater than the average of both monocultures) was relatively common and often ranged between 0% and 30%, but could also be negative at individual study sites. Each individual site demonstrated consistent patterns of the mixing effect over different measurement periods. Transgressive overyielding (where the mixed-species stand was more productive than either of the monocultures) was found at three study sites, while a monoculture was more productive on the other sites. Large variation between study sites indicated that the existing experiments do not fully represent the extensive region where this mixed pine-spruce forest can occur. Pooled increment data displayed a negative influence of latitude and stand age on the mixing effect of those tree species in forests younger than 70 years.
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