| 1. |
- Diehl, Eva, et al.
(författare)
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Effects of predator specialization, host plant and climate on biological control of aphids by natural enemies: a meta-analysis
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 50:1, s. 262-270
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Forskningsöversikt (refereegranskat)abstract
- Aphids are among the most severe invertebrate pests of crops and cause high economic losses. The control of aphids by natural enemies is an essential ecosystem service with high relevance to management strategies applied in agricultural plant production and horticulture. However, the current knowledge on the effectiveness of specialist and generalist predators in aphid control with respect to host plants and climatic conditions has not yet been summarized in a meta-analytical approach. We collected 60 studies providing 168 independent cases of predator exclusion experiments to analyse how predator and host plant group and climatic conditions affect aphid control by natural enemies. Effects of natural enemies on aphid populations were strongest in assemblages that included specialist predators, either alone or with generalist predators. Generalists alone also reduced aphid numbers significantly, but not to the same extent as specialists. Effects of natural enemies were weaker on aphid populations feeding on legumes compared with aphids on grasses or herbs. The percentage reduction of aphids feeding on grasses, herbs or legumes was higher in treatments with assemblages or specialists alone compared with generalists with the largest difference on grasses. According to all field studies from the temperate zone, effects of natural enemies on aphid populations were strongest in areas with high precipitation seasonality. A relationship between predator effects and temperature seasonality was only found for the USA. Synthesis and applications. Specialist predators alone or assemblages of specialists and generalists had the strongest effect on aphid populations, especially when either feeding on grasses and herbs or when exposed to extreme weather events. The control of aphids by natural enemies is most promising in grass and herb crops, whereas it is less suited for controlling aphids in legume crops. Facing climate change, the effect of extreme weather events on aphid control by natural enemies will have further implications for developing management strategies for aphid control in the future.
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| 2. |
- Rader, Romina, et al.
(författare)
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Organic farming and heterogeneous landscapes positively affect different measures of plant diversity
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51:6, s. 1544-1553
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Tidskriftsartikel (refereegranskat)abstract
- Increasing landscape heterogeneity and organic farming practices are known to enhance species richness in agroecosystems. However, little is known about the consequences of these management options on other biodiversity components such as community composition, phylogenetic structure and functional diversity which may be more closely linked to ecosystem functioning. We surveyed semi-natural plant communities within the uncultivated field margins of 18 arable farms in Skane, south Sweden. We investigated how taxonomic, phylogenetic and functional diversity responds to landscape heterogeneity (presence of semi-natural habitat) and farm management intensity (organic vs. conventional farming). Plant species richness and functional diversity metrics all responded positively to landscape heterogeneity, with the strongest effect occurring on conventional farms. Community composition differed with farm management, and mean phylogenetic relatedness, an indicator of phylogenetic structure, was significantly higher on the field margins of organic compared to conventional farms. Individual plant functional groups themselves responded in unique ways to land management and landscape heterogeneity.Synthesis and applications. Management strategies that promote the conservation of heterogeneous landscapes (i.e. a higher proportion of semi-natural habitats) and organic farm management practices are important for maintaining plant phylogenetic, functional and taxonomic diversity in agroecosystems. Accommodating various forms of diversity is important to ensure that ecosystems have the greatest possible array of species ecologies'. Such measures will help to improve the capacity of these ecosystems to provide multiple ecosystem functions, including the sustaining and regulating services of benefit to people. Management strategies that promote the conservation of heterogeneous landscapes (i.e. a higher proportion of semi-natural habitats) and organic farm management practices are important for maintaining plant phylogenetic, functional and taxonomic diversity in agroecosystems. Accommodating various forms of diversity is important to ensure that ecosystems have the greatest possible array of species ecologies'. Such measures will help to improve the capacity of these ecosystems to provide multiple ecosystem functions, including the sustaining and regulating services of benefit to people.
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| 3. |
- Rusch, Adrien, et al.
(författare)
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Flow and stability of natural pest control services depend on complexity and crop rotation at the landscape scale
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 50:2, s. 345-354
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Tidskriftsartikel (refereegranskat)abstract
- Increasing landscape complexity can enhance biodiversity and ecosystem services in agroecosystems. However, policies based on conversion of arable land into semi-natural habitats to increase landscape complexity and ecosystem services can be difficult to implement. Although it appears to be a promising management option, nothing is known about the effect of increasing landscape diversity through crop rotations on the delivery of ecosystem services. In this study, we examined how landscape complexity and crop rotation intensity in the landscape at different spatial scales affect the flow and the stability of natural pest control services in barley fields using manipulative cage experiments. Exclusion experiments revealed that natural enemies can have a strong impact on aphid population growth and that the delivery of pest control services is strongly dependent on the landscape context. We found that the overall level of pest control increased with landscape complexity and that this effect was independent of crop rotation intensity. In addition, the within-field stability in pest control services increased with crop rotation intensity in the landscape, although stability in parasitism rates decreased. Multiple spatial scales analyses showed that the mean level of natural pest control was best predicted by landscape complexity at the 0 center dot 5-km and the 1-km spatial scales. The stability in overall pest control decreased with proportion of ley at the 2 center dot 5-km and the 3-km spatial scales. Synthesis and applications. Our study disentangled, for the first time, the relative effects of landscape complexity and crop rotation intensity on the delivery of an ecosystem service. We show that combined management of semi-natural habitat and crop rotation can stabilize and enhance natural pest control in agricultural landscapes. Our findings have important implications in terms of management options to maintain and enhance ecosystem services in agroecosystems. They suggest that conservation of heterogeneous landscapes, characterized by a higher proportion of semi-natural habitats such as pastures and relatively small fields, is essential for maintaining and enhancing effective biological control in agroecosystems.
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| 4. |
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| 5. |
- Angerbjörn, Anders, et al.
(författare)
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Carnivore conservation in practice : replicatedmanagement actions on a large spatial scale
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 50:1, s. 59-67
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Tidskriftsartikel (refereegranskat)abstract
- More than a quarter of the world’s carnivores are threatened, often due to multiple andcomplex causes. Considerable research efforts are devoted to resolving the mechanisms behindthese threats in order to provide a basis for relevant conservation actions. However, evenwhen the underlying mechanisms are known, specific actions aimed at direct support for carnivoresare difficult to implement and evaluate at efficient spatial and temporal scales.2. We report on a 30-year inventory of the critically endangered Fennoscandian arctic foxVulpes lagopus L., including yearly surveys of 600 fox dens covering 21 000 km2. These surveysshowed that the population was close to extinction in 2000, with 40–60 adult animalsleft. However, the population subsequently showed a fourfold increase in size.3. During this time period, conservation actions through supplementary feeding and predatorremoval were implemented in several regions across Scandinavia, encompassing 79% of thearea. To evaluate these actions, we examined the effect of supplemental winter feeding andred fox control applied at different intensities in 10 regions. A path analysis indicated that47% of the explained variation in population productivity could be attributed to lemmingabundance, whereas winter feeding had a 29% effect and red fox control a 20% effect.4. This confirms that arctic foxes are highly dependent on lemming population fluctuationsbut also shows that red foxes severely impact the viability of arctic foxes. This study also highlightsthe importance of implementing conservation actions on extensive spatial and temporalscales, with geographically dispersed actions to scientifically evaluate the effects. We note thatpopulation recovery was only seen in regions with a high intensity of management actions.5. Synthesis and applications. The present study demonstrates that carnivore populationdeclines may be reversed through extensive actions that target specific threats. Fennoscandianarctic fox is still endangered, due to low population connectivity and expected climate impactson the distribution and dynamics of lemmings and red foxes. Climate warming is expected tocontribute to both more irregular lemming dynamics and red fox appearance in tundra areas;however, the effects of climate change can be mitigated through intensive managementactions such as supplemental feeding and red fox control.
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| 6. |
- Edsman, Lennart, et al.
(författare)
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Detection of crayfish plague spores in large freshwater systems
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51, s. 544-553
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Tidskriftsartikel (refereegranskat)abstract
- Our study demonstrates a low amount of pathogen spores are present in aquatic environments with non-indigenous crayfish species, emphasizing the need for large-volume filtering techniques for successful detection. The approach can be used for risk assessments and to improve conservation and management strategies of crayfish in Europe. Applications of this method include targeted disease surveillance, habitat evaluation prior to crayfish re-stockings and water monitoring that can minimize disease transmission and spread, for example in crayfish farms and prior to fish movements for stocking purposes.
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| 7. |
- Feckler, Alexander, et al.
(författare)
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Cryptic species diversity: an overlooked factor in environmental management?
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51, s. 958-967
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Tidskriftsartikel (refereegranskat)abstract
- 1. Molecular genetic methods continuously uncover cryptic lineages harboured by various species. However, from an applied perspective, it remains unclear whether and to which extent such a genetic diversity affects biological traits (e. g. ecological, behavioural and physiological characteristics) and environmental management.2. We assessed potential deviations regarding the trait 'environmental stress tolerance' using individuals from five field populations of each of two cryptic lineages (called A and B) comprised under the nominal species Gammarus fossarum. We used ammonia as a chemical stressor while assessing the feeding rate on leaf discs as a measure of sublethal response. In this context, we established a restriction fragment length polymorphism assay to allow a rapid identification of the lineages.3. We observed a biologically meaningful and statistically significant twofold higher overall tolerance of one cryptic lineage, lineage B, over the other. Confounding factors that may have the potential to influence the test results, such as life stage, sex, season of collection, parasitism, physiological status of organisms and upstream land-use patterns of the river catchments, were either controlled for or displayed only minor deviations between lineages.4. Synthesis and applications. The trait differences observed in the present study seem to be mainly explained by the considerable genetic differentiation between cryptic lineages of one nominal species. Although traits other than tolerance have been minimally investigated in this context, this study indicates implications in the reliability and quality of environmental monitoring and management if cryptic lineage complexes are ignored.
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| 8. |
- Fedrowitz, Katja, et al.
(författare)
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Can retention forestry help conserve biodiversity? A meta-analysis
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51, s. 1669–1679-
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Forskningsöversikt (refereegranskat)abstract
- Industrial forestry typically leads to a simplified forest structure and altered species composition. Retention of trees at harvest was introduced about 25years ago to mitigate negative impacts on biodiversity, mainly from clearcutting, and is now widely practiced in boreal and temperate regions. Despite numerous studies on response of flora and fauna to retention, no comprehensive review has summarized its effects on biodiversity in comparison to clearcuts as well as un-harvested forests. Using a systematic review protocol, we completed a meta-analysis of 78 studies including 944 comparisons of biodiversity between retention cuts and either clearcuts or un-harvested forests, with the main objective of assessing whether retention forestry helps, at least in the short term, to moderate the negative effects of clearcutting on flora and fauna. Retention cuts supported higher richness and a greater abundance of forest species than clearcuts as well as higher richness and abundance of open-habitat species than un-harvested forests. For all species taken together (i.e. forest species, open-habitat species, generalist species and unclassified species), richness was higher in retention cuts than in clearcuts. Retention cuts had negative impacts on some species compared to un-harvested forest, indicating that certain forest-interior species may not survive in retention cuts. Similarly, retention cuts were less suitable for some open-habitat species compared with clearcuts. Positive effects of retention cuts on richness of forest species increased with proportion of retained trees and time since harvest, but there were not enough data to analyse possible threshold effects, that is, levels at which effects on biodiversity diminish. Spatial arrangement of the trees (aggregated vs. dispersed) had no effect on either forest species or open-habitat species, although limited data may have hindered our capacity to identify responses. Results for different comparisons were largely consistent among taxonomic groups for forest and open-habitat species, respectively.Synthesis and applications. Our meta-analysis provides support for wider use of retention forestry since it moderates negative harvesting impacts on biodiversity. Hence, it is a promising approach for integrating biodiversity conservation and production forestry, although identifying optimal solutions between these two goals may need further attention. Nevertheless, retention forestry will not substitute for conservation actions targeting certain highly specialized species associated with forest-interior or open-habitat conditions.Our meta-analysis provides support for wider use of retention forestry since it moderates negative harvesting impacts on biodiversity. Hence, it is a promising approach for integrating biodiversity conservation and production forestry, although identifying optimal solutions between these two goals may need further attention. Nevertheless, retention forestry will not substitute for conservation actions targeting certain highly specialized species associated with forest-interior or open-habitat conditions.
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| 9. |
- Frankow-Lindberg, Bodil, et al.
(författare)
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Ecosystem function enhanced by combining four functional types of plant species in intensively managed grassland mixtures: a 3-year continental-scale field experiment
- 2013
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 50, s. 365-375
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Tidskriftsartikel (refereegranskat)abstract
- A coordinated continental-scale field experiment across 31 sites was used to compare the biomass yield of monocultures and four species mixtures associated with intensively managed agricultural grassland systems. To increase complementarity in resource use, each of the four species in the experimental design represented a distinct functional type derived from two levels of each of two functional traits, nitrogen acquisition (N2-fixing legume or nonfixing grass) crossed with temporal development (fast-establishing or temporally persistent). Relative abundances of the four functional types in mixtures were systematically varied at sowing to vary the evenness of the same four species in mixture communities at each site and sown at two levels of seed density. Across multiple years, the total yield (including weed biomass) of the mixtures exceeded that of the average monoculture in >97% of comparisons. It also exceeded that of the best monoculture (transgressive overyielding) in about 60% of sites, with a mean yield ratio of mixture to best-performing monoculture of 1 center dot 07 across all sites. Analyses based on yield of sown species only (excluding weed biomass) demonstrated considerably greater transgressive overyielding (significant at about 70% of sites, ratio of mixture to best-performing monoculture=1 center dot 18). Mixtures maintained a resistance to weed invasion over at least 3years. In mixtures, median values indicate <4% of weed biomass in total yield, whereas the median percentage of weeds in monocultures increased from 15% in year 1 to 32% in year 3. Within each year, there was a highly significant relationship (P<0 center dot 0001) between sward evenness and the diversity effect (excess of mixture performance over that predicted from the monoculture performances of component species). At lower evenness values, increases in community evenness resulted in an increased diversity effect, but the diversity effect was not significantly different from the maximum diversity effect across a wide range of higher evenness values. The latter indicates the robustness of the diversity effect to changes in species' relative abundances. Across sites with three complete years of data (24 of the 31 sites), the effect of interactions between the fast-establishing and temporal persistent trait levels of temporal development was highly significant and comparable in magnitude to effects of interactions between N2-fixing and nonfixing trait levels of nitrogen acquisition. Synthesis and applications. The design of grassland mixtures is relevant to farm-level strategies to achieve sustainable intensification. Experimental evidence indicated significant yield benefits of four species agronomic mixtures which yielded more than the highest-yielding monoculture at most sites. The results are relevant for agricultural practice and show how grassland mixtures can be designed to improve resource complementarity, increase yields and reduce weed invasion. The yield benefits were robust to considerable changes in the relative proportions of the four species, which is extremely useful for practical management of grassland swards.
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| 10. |
- Johansson, Maria, et al.
(författare)
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Fuel, fire and cattle in African highlands: traditional management maintains a mosaic heathland landscape
- 2014
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Ingår i: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 51, s. 1396-1405
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Tidskriftsartikel (refereegranskat)abstract
- 1. Shrubland ecosystems are often inherently flammable due to a canopy structure favourable for fire propagation. At the same time, the fuel bed is not spatially uniform, but a complex mix of shrubs and herbaceous vegetation that will change with time since fire. These patterns are further influenced by megaherbivores capable of consuming large quantities of biomass that otherwise would enter the fuel bed, but the net effects for temporal thresholds of flammability are poorly known.2. We quantified post-fire fuel succession and effects of free-ranging cattle in high-elevation Erica shrublands in Ethiopia where traditional fire management is still practised above the treeline at 3500 m, despite being challenged by authorities.3. We found a near-linear accumulation of canopy fuel at 2 . 6 Mg ha(-1) year(-1), but stands <5 years old did not burn due to spatial separation of individual Erica shrubs before canopy closure and lack of fine dead fuels.4. Inside cattle exclosures, Erica height growth was nearly three times faster and reached the assumed flammability threshold c. 3 years earlier than in browsed/grazed stands, where cattle also kept herbaceous vegetation between shrubs short, thus eliminating litter that could otherwise bridge the discontinuous fuel bed in early succession.5. Modelling of fire behaviour indicated progressively higher fire intensity and rate of spread for stands >5 years. But if stands escape fire for several decades, flammability again decreases as canopy fuels become increasingly separated from the ground. This may be the ultimate reason for sharp treelines on many tropical mountains where fire is confined mainly to higher elevations.6. Synthesis and applications. In shrublands where dominant plants can outgrow consumption by large herbivores, provision of good cattle habitat typically requires fire. We found that fire and cattle interact to maintain a relatively stable system, where fuel limitation in early succession creates fire breaks that prevent landscape-wide wildfires. The same negative feedback protects the Erica from degradation by too frequent fires. As shrublands can have widely different compositions, the response to variation in fire frequency and herbivore pressure is likely to differ, but for sustainable management fire and grazing have to be treated in consort.
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