| 1. |
- Amelia, Tudoran, et al.
(författare)
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Using associational effects of European beech on Norway spruce to mitigate damage by a forest regeneration pest, the pine weevil Hylobius abietis
- 2021
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 0378-1127 .- 1872-7042. ; 486
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Tidskriftsartikel (refereegranskat)abstract
- Forest regeneration can be compromised by insect damage to newly-planted conifer seedlings, with the pine weevil, Hylobius abietis, being the most economically important pest in Europe. Seedling protection strategies include physical barriers, silvicultural measures and insecticides, while the potential benefits of Associational Effects (AE) have been little explored. Associational Resistance (AR) or Susceptibility (AS) arise when neighbouring plants decrease or increase, respectively, the likelihood and extent of attack on a focal plant. We investigated the potential of European beech, Fagus sylvatica, to mediate AE for Norway spruce, Picea abies, seedlings against pine weevil damage. First, we examined the effects of neighbor identity on damage to P. abies at a small scale, using choice arenas in the lab. Then, in the field, we examined these effects at a larger scale using plots containing only Norway spruce, or both species. We found that P. abies seedlings were attacked and damaged less by weevils when beech was their close neighbor, relative to having another Norway spruce as a neighbor in the lab. Yet, no difference in damage between only spruce and mixed seedling plots was found in the field. Our results indicate that the susceptibility of P. abies to H. abietis can be influenced by neighbor identity, and effects can vary with inter-plant distance. In close proximity, the presence of the non-host F. sylvatica can alter pine weevil feeding behaviour and thus, has the potential to mediate AR. However, these associational effects appear not to provide enhanced seedling protection at a larger scale.
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| 2. |
- Ammunét, Tea, et al.
(författare)
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Northern geometrids and climate change: from abiotic factors to trophic interactions
- 2015
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Ingår i: Climate change and insect pests. - 9781780643786 ; 7, s. 235-247
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Bokkapitel (refereegranskat)abstract
- The subarctic mountain birch forests have been periodically disturbed by geometrid moth outbreaks since at least the mid-19th century. The effects of these disturbances can be seen from landscape-level dieback of the birch forest to local-level changes in soil processes. Recent research efforts have demonstrated that the geometrid moth-birch forest system is undergoing changes that could be linked to the ongoing climate warming. Milder winter and spring temperatures influence winter survival and outbreak ranges of the moths, and are also alleviating range expansions and the spread of new species to the area. Moreover, phenology matching with the host plant may be altered. The outcome appears to be intensified outbreaks and a potential for altered species interactions and dynamics with ecosystem-wide consequences.This chapter will first introduce the prevailing dynamics of the mountain birch-geometrid system and the reported ecosystem effects of geometrid outbreaks. Second, the chapter summarizes observations of ongoing abiotic changes in the area and presents the potential known and unknown effects on the study species. Finally, the chapter discusses the future scenarios for this northern ecosystem and the possibility of major ecosystem changes.
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| 3. |
- Berggren Nieto, Kristina, et al.
(författare)
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Synergistic effects of methyl jasmonate treatment and propagation method on Norway spruce resistance against a bark-feeding insect
- 2023
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Ingår i: Frontiers in Plant Science. - 1664-462X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- Utilizing plants with enhanced resistance traits is gaining interest in plant protection. Two strategies are especially promising for increasing resistance against a forest insect pest, the pine weevil (Hylobius abietis): exogenous application of the plant defense hormone methyl jasmonate (MeJA), and production of plants through the clonal propagation method somatic embryogenesis (SE). Here, we quantified and compared the separate and combined effects of SE and MeJA on Norway spruce resistance to pine weevil damage. Plants produced via SE (emblings) and nursery seedlings (containerized and bare-root), were treated (or not) with MeJA and exposed to pine weevils in the field (followed for 3 years) and in the lab (with a non-choice experiment). Firstly, we found that SE and MeJA independently decreased pine weevil damage to Norway spruce plants in the field by 32-33% and 53-59%, respectively, compared to untreated containerized and bare-root seedlings. Secondly, SE and MeJA together reduced damage to an even greater extent, with treated emblings receiving 86-87% less damage when compared to either untreated containerized or bare-root seedlings in the field, and by 48% in the lab. Moreover, MeJA-treated emblings experienced 98% lower mortality than untreated containerized seedlings, and this high level of survival was similar to that experienced by treated bare-root seedlings. These positive effects on survival remained for MeJA-treated emblings across the 3-year experimental period. We conclude that SE and MeJA have the potential to work synergistically to improve plants' ability to resist damage, and can thus confer a strong plant protection advantage. The mechanisms underlying these responses merit further examination.
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| 4. |
- Berggren, Åsa, et al.
(författare)
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The distribution and abundance of animal populations in a climate of uncertainty
- 2009
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Ingår i: Oikos. - : Wiley. - 0030-1299 .- 1600-0706. ; 118, s. 1121-1126
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Tidskriftsartikel (refereegranskat)abstract
- Current predictions regarding the ecological consequences of climate change on animal populations are generally autecological and species-specific, and/or non-mechanistic extrapolations of recent short-term patterns. To better understand and predict the effects of climate change on the distribution of species and the abundance of populations we offer a novel, broad theoretical framework. Climate-induced changes in trophic structure may actually be more predictable than effects on individual species. The logic is that there are general differences in climatic sensitivity among trophic levels - specifically, that as one moves up trophic levels, there is an increase in the temperature sensitivity of vital rates. More precisely, we provide: (1) a formal mathematical definition of distribution limits that is both operational and conceptual, introducing the concept DL(50), defined as the geographic and climatic isoline representing an equilibrium occupancy of half of the suitable habitats; (2) a matrix of the possible changes in trophic structure from climate change and the general theoretical consequences; and (3) a new idea that predicts broad effects of climatic warming on trophic systems. Our intention is to help meet the challenge of developing and testing general theoretical models that can predict which species will be winners and losers in ecological time, which evolutionary traits will be favoured or selected against, and what will be consequences for ecosystem structure and function.
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| 5. |
- Birkhofer, Klaus, et al.
(författare)
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Methods to identify the prey of invertebrate predators in terrestrial field studies
- 2017
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 7:6, s. 1942-1953
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Tidskriftsartikel (refereegranskat)abstract
- Predation is an interaction during which an organism kills and feeds on another organism. Past and current interest in studying predation in terrestrial habitats has yielded a number of methods to assess invertebrate predation events in terrestrial ecosystems. We provide a decision tree to select appropriate methods for individual studies. For each method, we then present a short introduction, key examples for applications, advantages and disadvantages, and an outlook to future refinements. Video and, to a lesser extent, live observations are recommended in studies that address behavioral aspects of predator-prey interactions or focus on per capita predation rates. Cage studies are only appropriate for small predator species, but often suffer from a bias via cage effects. The use of prey baits or analyses of prey remains are cheaper than other methods and have the potential to provide per capita predation estimates. These advantages often come at the cost of low taxonomic specificity. Molecular methods provide reliable estimates at a fine level of taxonomic resolution and are free of observer bias for predator species of any size. However, the current PCR-based methods lack the ability to estimate predation rates for individual predators and are more expensive than other methods. Molecular and stable isotope analyses are best suited to address systems that include a range of predator and prey species. Our review of methods strongly suggests that while in many cases individual methods are sufficient to study specific questions, combinations of methods hold a high potential to provide more holistic insights into predation events. This review presents an overview of methods to researchers that are new to the field or to particular aspects of predation ecology and provides recommendations toward the subset of suitable methods to identify the prey of invertebrate predators in terrestrial field research.
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| 6. |
- Björkman, Christer, et al.
(författare)
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Causes behind insect folivory patterns in latitudinal gradients
- 2011
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Ingår i: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 99, s. 367-369
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Tidskriftsartikel (refereegranskat)abstract
- Summary 1. Adams and Zhang recently published one of the best studies so far of patterns of insect folivory along a latitudinal (climatic) gradient. They show clear negative trends in foliage loss in relation to temperature for certain groups of insect herbivores. 2. Although their suggestion that the plant–herbivore interaction may be more important in cooler climates could be valid, they did not bring up the complementary explanation that interactions between predators and herbivores could also vary with climate. There are indications that insect natural enemies may respond more positively than insect herbivores to an increase in temperature. We argue that higher predator pressure in warmer climates may partly explain the patterns observed by Adams and Zhang. 3. Synthesis. To further develop the important research concerning herbivory in a changing climate, both theoretically and empirically, plant ecologists and entomologists would mutually benefit fromjoining forces. Key-words: climate, herbivory, plant–herbivore interactions, temperature, trophic interactions
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| 7. |
- Björkman, Christer, et al.
(författare)
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Effects of new forest management on insect damage risk in a changing climate
- 2015
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Ingår i: Climate change and insect pests. - 9781780643786 ; 7, s. 248-266
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Bokkapitel (refereegranskat)abstract
- Recent findings suggest that damage by forest insect pests will increase as a consequence of climate warming. Here, we ask whether changes in forest management can alter and possibly mitigate the increased risk of damage and outbreaks. We focus mainly on conditions in northern Europe, particularly Sweden, but conclusions should be valid for northern temperate forests. Three types of insect pests are considered; the regeneration pest,Hylobius abietis(pine weevil), defoliators and the bark beetle,Ips typographus. We compare the expected effect of new management methods with the presently predominant method of even-aged stands, which are thinned two to three times before final harvest by clear-felling. Continuous cover forestry (CCF) is the method most different from the present practice. CCF would lead to a drastic decrease in pine weevils, and also less damage by defoliators, but this latter prediction is uncertain. For the bark beetle, the uncertainty is even greater. In mixed forests, all three insect pest types are expected to become less of a problem. Putative mechanisms involve more abundant and diverse natural enemy fauna, and a more scattered distribution of food resources. A shorter rotation period (including no thinning) is expected to increase the damage by pine weevils, as it will result in more abundant breeding material. For defoliators, it is difficult to foresee the effects. A shorter rotation period will decrease the risk of bark beetle outbreaks, as storm-fellings will be less frequent and young stands more common. The effects of exotic tree species and clonal forestry are complex and will depend on several factors. A general conclusion is that forest management may be used to mitigate the anticipated risk of insect pest damage as a consequence of climate warming, but more research is required to certify these indications
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| 8. |
- Björkman, Christer, et al.
(författare)
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Insect Pests in Future Forests: More Severe Problems?
- 2011
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Ingår i: Forests. - : MDPI AG. - 1999-4907. ; 2, s. 474-485
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: A common concern is that damage by insects will increase in forests as a consequence of climate change. We are assessing the likelihood of this predicted outcome by examining how other factors (especially changes in forest management practices) may interact with effects of climate change. Here we describe the strategies for improving understanding of the causes of insect outbreaks and predicting the likelihood of insect-mediated damage increasing in the future. The adopted approaches are: (i) analyses of historical data, (ii) comparison of life history traits of outbreak and non-outbreak species, (iii) experiments along climatic gradients to quantify the strength of trophic interactions, and (iv) modeling. We conclude that collaboration by researchers from many disciplines is required to evaluate available data regarding the complex interactions involved, to identify knowledge gaps, and facilitate attempts to progress beyond speculation to more robust predictions concerning future levels of insect damage to forests
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| 9. |
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| 10. |
- Björkman, Christer, et al.
(författare)
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Stand structure of Monocotyledons and Dicotyledons in different successional stages in Corcovado National Park, Costa Rica
- 2011
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Ingår i: Bois Et Forets Des Tropiques. - 0006-579X. ; , s. 33-40
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Tidskriftsartikel (refereegranskat)abstract
- The two major groups of angiosperms, monocotyledons and dicotyledons, differ in several of their life history traits. Despite the obvious differences between the two groups, there are few studies elaborating on how these may relate to their ecological succession. The study compares the relative densities of these two fundamental groups of plants with different evolutionary histories in forests in two different successional stages at the Sirena station in Costa Rica's Corcovado National Park, in Central America. The hypothesis was that the monocotyledons/dicotyledons ratio would decrease in later successional stages. A total of 40 right-angled triangular plots ((5 x 5 m)/2) were sampled and the plants were divided into four crown size classes, as well as into monocotyledons and dicotyledons. Plant densities and crown size class distribution were analysed using ANOVA with the general linear model (GLM) procedure. The mean overall plant density in the secondary forest was significantly greater than in the primary forest (P < 0.001). The structure of the crown size class distribution, however, was similar for both monocotyledons and dicotyledons, and for the primary and secondary forest types. There was no significant difference between the two forests in the monocotyledons to dicotyledons ratio (P = 0.99). The crown size class distribution results indicate that there is a similar distribution trend in monocotyledon and dicotyledon succession, although there are always more dicotyledons than monocotyledons. These results led to conclude that a larger difference between successional stages is necessary to perceive the difference anticipated in this study.
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