1. |
- Allan, Eric, et al.
(författare)
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Interannual variation in land-use intensity enhances grassland multidiversity
- 2014
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 111:1, s. 308-313
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Tidskriftsartikel (refereegranskat)abstract
- Although temporal heterogeneity is a well-accepted driver of biodiversity, effects of interannual variation in land-use intensity (LUI) have not been addressed yet. Additionally, responses to land use can differ greatly among different organisms; therefore, overall effects of land-use on total local biodiversity are hardly known. To test for effects of LUI (quantified as the combined intensity of fertilization, grazing, and mowing) and interannual variation in LUI (SD in LUI across time), we introduce a unique measure of whole-ecosystem biodiversity, multidiversity. This synthesizes individual diversity measures across up to 49 taxonomic groups of plants, animals, fungi, and bacteria from 150 grasslands. Multidiversity declined with increasing LUI among grasslands, particularly for rarer species and aboveground organisms, whereas common species and belowground groups were less sensitive. However, a high level of interannual variation in LUI increased overall multidiversity at low LUI and was even more beneficial for rarer species because it slowed the rate at which the multidiversity of rare species declined with increasing LUI. In more intensively managed grasslands, the diversity of rarer species was, on average, 18% of the maximum diversity across all grasslands when LUI was static over time but increased to 31% of the maximum when LUI changed maximally over time. In addition to decreasing overall LUI, we suggest varying LUI across years as a complementary strategy to promote biodiversity conservation.
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2. |
- Soliveres, Santiago, et al.
(författare)
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Biodiversity at multiple trophic levels is needed for ecosystem multifunctionality
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 536:7617, s. 456-459
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Tidskriftsartikel (refereegranskat)abstract
- Many experiments have shown that loss of biodiversity reduces the capacity of ecosystems to provide the multiple services on which humans depend. However, experiments necessarily simplify the complexity of natural ecosystems and will normally control for other important drivers of ecosystem functioning, such as the environment or land use. In addition, existing studies typically focus on the diversity of single trophic groups, neglecting the fact that biodiversity loss occurs across many taxa and that the functional effects of any trophic group may depend on the abundance and diversity of others. Here we report analysis of the relationships between the species richness and abundance of nine trophic groups, including 4,600 above- and below-ground taxa, and 14 ecosystem services and functions and with their simultaneous provision (or multifunctionality) in 150 grasslands. We show that high species richness in multiple trophic groups (multitrophic richness) had stronger positive effects on ecosystem services than richness in any individual trophic group; this includes plant species richness, the most widely used measure of biodiversity. On average, three trophic groups influenced each ecosystem service, with each trophic group influencing at least one service. Multitrophic richness was particularly beneficial for 'regulating' and 'cultural' services, and for multifunctionality, whereas a change in the total abundance of species or biomass in multiple trophic groups (the multitrophic abundance) positively affected supporting services. Multitrophic richness and abundance drove ecosystem functioning as strongly as abiotic conditions and land-use intensity, extending previous experimental results to real-world ecosystems. Primary producers, herbivorous insects and microbial decomposers seem to be particularly important drivers of ecosystem functioning, as shown by the strong and frequent positive associations of their richness or abundance with multiple ecosystem services. Our results show that multitrophic richness and abundance support ecosystem functioning, and demonstrate that a focus on single groups has led to researchers to greatly underestimate the functional importance of biodiversity.
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3. |
- Soliveres, Santiago, et al.
(författare)
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Locally rare species influence grassland ecosystem multifunctionality
- 2016
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Ingår i: Philosophical Transactions of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 371:1694
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Tidskriftsartikel (refereegranskat)abstract
- Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity-multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land-use intensity (LUI) gradient. The diversity of above-and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community-level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species-specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities.
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4. |
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5. |
- Andersson, Georg, et al.
(författare)
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Landscape heterogeneity and farming practice alter the species composition and taxonomic breadth of pollinator communities
- 2013
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 14:7, s. 540-546
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Tidskriftsartikel (refereegranskat)abstract
- Effects of landscape heterogeneity and farming practice on species composition are less well known than those on species richness, in spite of the fact that community composition can be at least as important for ecosystem services, such as pollination. Here, we assessed the effect of organic farming and landscape heterogeneity on pollinator communities, focusing on multivariate patterns in species composition and the taxonomic breadth of communities. By relating our results to patterns observed for species richness we show that: (1) species richness generally declines with decreasing landscape heterogeneity, but taxonomic breadth only declines with landscape heterogeneity on conventionally managed farms. We further highlight the importance to provide results of species composition analyses as (2) primarily hoverfly species benefited from organic farming, but three bee species from different families were favoured by conventionally managed farms and (3) two hoverfly species with aphidophagous larvae showed contrasting responses to landscape heterogeneity. These results advance the understanding of how landscape heterogeneity and farming practices alter insect communities and further suggest that diversity patterns need to be analysed beyond species richness to fully uncover consequences of agricultural intensification.
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6. |
- Arvidsson, Fredrik, et al.
(författare)
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Geographic location, not forest type, affects the diversity of spider communities sampled with malaise traps in Sweden
- 2016
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450 .- 0003-3847. ; 53:3-4, s. 215-227
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Tidskriftsartikel (refereegranskat)abstract
- The latitudinal diversity gradient predicts higher species richness at lower latitudes. Here, we utilize the data from a long-term monitoring with malaise traps to analyse if spider communities in Sweden are affected by geographic gradients and if these effects hold independent of forest type. The species richness and the effective number of species in spider communities were not significantly related to the latitudinal gradient. The effective number of species and the taxonomic distinctness of spider communities were related to longitude, with a higher number, but fewer related species in western parts of Sweden. The species and family composition were significantly related to latitude independent of forest type, with a dominance of Linyphiidae individuals and species in the north. Our study demonstrates the suitability of malaise trap sampling to contribute to a better understanding of local spider communities, as several rare and locally new species were recorded in this study.
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7. |
- Arvidsson, Fredrik, et al.
(författare)
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Geographic location, not forest type, affects the diversity of spider communities sampled with malaise traps in Sweden
- 2016
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Ingår i: Annales Zoologici Fennici. - : Finnish Zoological and Botanical Publishing Board. - 0003-455X .- 1797-2450 .- 0003-3847. ; 53:3-4, s. 215-227
-
Tidskriftsartikel (refereegranskat)abstract
- The latitudinal diversity gradient predicts higher species richness at lower latitudes. Here, we utilize the data from a long-term monitoring with malaise traps to analyse if spider communities in Sweden are affected by geographic gradients and if these effects hold independent of forest type. The species richness and the effective number of species in spider communities were not significantly related to the latitudinal gradient. The effective number of species and the taxonomic distinctness of spider communities were related to longitude, with a higher number, but fewer related species in western parts of Sweden. The species and family composition were significantly related to latitude independent of forest type, with a dominance of Linyphiidae individuals and species in the north. Our study demonstrates the suitability of malaise trap sampling to contribute to a better understanding of local spider communities, as several rare and locally new species were recorded in this study.
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8. |
- Berger, Josef S., et al.
(författare)
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Landscape configuration affects herbivore–parasitoid communities in oilseed rape
- 2018
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Ingår i: Journal of Pest Science. - : Springer Science and Business Media LLC. - 1612-4758 .- 1612-4766. ; 91:3, s. 1093-1105
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Tidskriftsartikel (refereegranskat)abstract
- It is crucial to consider the effects of large-scale drivers on species presences and ecological interactions to understand what structures communities. In our study, we investigated how the species composition and the potential interaction networks of herbivore and parasitoid communities in oilseed rape fields are affected by agricultural landscape characteristics. Insect communities of 26 winter oilseed rape fields in southern Sweden were captured in water traps over a continuous time span of 30 ± 2 days. In total, 31% of the variation in the composition of herbivore host communities was explained by a combination of the surrounding oilseed rape area in the study year and the previous year and distance to the nearest forest. The oilseed rape area in the study year and distance to forest also explained 14% of the variation in the composition of parasitoid communities. Distance to the nearest forest together with the area of oilseed rape in the previous year explained 45% of the variation in asymmetry of interaction webs. These results indicate that several measures of landscape configuration are important both for the composition of host and parasitoid communities and also for the structure of interaction networks. Our results support the view that it is an appropriate strategy to cultivate oilseed rape in landscapes that are far away from forests, in order to minimize recolonization by pest species and at the same time to attract parasitoid species from the open landscape.
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9. |
- Bilde, Trine, et al.
(författare)
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Survival benefits select for group living in a social spider despite reproductive costs
- 2007
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 20:6, s. 2412-2426
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of cooperation requires benefits of group living to exceed costs. Hence, some components of fitness are expected to increase with increasing group size, whereas others may decrease because of competition among group members. The social spiders provide an excellent system to investigate the costs and benefits of group living: they occur in groups of various sizes and individuals are relatively short-lived, therefore life history traits and Lifetime Reproductive Success (LRS) can be estimated as a function of group size. Sociality in spiders has originated repeatedly in phylogenetically distant families and appears to be accompanied by a transition to a system of continuous intra-colony mating and extreme inbreeding. The benefits of group living in such systems should therefore be substantial. We investigated the effect of group size on fitness components of reproduction and survival in the social spider Stegodyphus dumicola in two populations in Namibia. In both populations, the major benefit of group living was improved survival of colonies and late-instar juveniles with increasing colony size. By contrast, female fecundity, female body size and early juvenile survival decreased with increasing group size. Mean individual fitness, estimated as LRS and calculated from five components of reproduction and survival, was maximized for intermediate- to large-sized colonies. Group living in these spiders thus entails a net reproductive cost, presumably because of an increase in intra-colony competition with group size. This cost is traded off against survival benefits at the colony level, which appear to be the major factor favouring group living. In the field, many colonies occur at smaller size than expected from the fitness curve, suggesting ecological or life history constraints on colony persistence which results in a transient population of relatively small colonies.
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10. |
- Birkhofer, Klaus, et al.
(författare)
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A framework to identify indicator species for ecosystem services in agricultural landscapes
- 2018
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 91, s. 278-286
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Tidskriftsartikel (refereegranskat)abstract
- Improving our understanding of the relationships between biodiversity and the delivery of ecosystem services is crucial for the development of sustainable agriculture. We introduce a novel framework that is based on the identification of indicator species for single or multiple ecosystem services across taxonomic groups based on indicator species analyses. We utilize multi-species community data (unlike previous single species approaches) without giving up information about the identity of species in our framework (unlike previous species richness approaches). We compiled a comprehensive community dataset including abundances of 683 invertebrate, vertebrate and plant species to identify indicator species that were either positively or negatively related to biological control, diversity of red-listed species or crop yield in agricultural landscapes in southern Sweden. Our results demonstrate that some taxonomic groups include significantly higher percentages of indicator species for these ecosystem services. Spider communities for example included a higher percentage of significant positive indicator species for biological control than ground or rove beetle communities. Bundles of indicator species for the analysed ecosystem service potentials usually included species that could be linked to the respective ecosystem service based on their functional role in local communities. Several of these species are conspicuous enough to be monitored by trained amateurs and could be used in bundles that are either crucial for the provision of individual ecosystem services or indicate agricultural landscapes with high value for red-listed species or crop yields. The use of bundles of characteristic indicator species for the simultaneous assessment of ecosystem services may reduce the amount of labour, time and cost in future assessments. In addition, future analysis using our framework in other ecosystems or with other subsets of ecosystem services and taxonomic groups will improve our understanding of service-providing species in local communities. In any case, expert knowledge is needed to select species from the identified subsets of significant indicator species and these species should be validated by existing data or additional sampling prior to being used for ecosystem service monitoring.
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11. |
- Birkhofer, Klaus, et al.
(författare)
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Arthropod food webs in organic and conventional wheat farming systems: a stable isotope approach
- 2011
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Ingår i: Agricultural and Forest Entomology. - : Wiley. - 1461-9555. ; 13:2, s. 197-204
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Tidskriftsartikel (refereegranskat)abstract
- 1 Agricultural intensification not only alters the structure of arthropod communities, but also may affect biotic interactions by altering the availability of basal resources. We analyzed variations in stable isotope ratios (15N/14N and 13C/12C) of fertilizers, plants, prey and generalist predators in organic and conventional farming systems in a long-term agricultural experiment [DOK trial (bioDynamic, bioOrganic, Konventionell)]. Two basal resources with pronounced differences in carbon isotope signatures, wheat litter (C3 plant) and maize litter (C4 plant), were used to uncover differences in food web properties between the two farming systems (conventional versus organic). 2 Predators incorporated significantly higher proportions of carbon from wheat sources in organically managed fields, suggesting that they were more closely linked to wheat-consuming prey in this system. The δ15N values of three predaceous species were more than 2‰ greater in summer than in spring. 3 The results obtained suggest that generalist predators consumed higher proportions of herbivore prey in the organic system and that starvation and intraguild predation rates increased in some predator species with time. 4 Because the effects of farming system and sampling date on predators were species-specific, conserving a diverse natural enemy community including species with different phenologies and sensitivities to management practices may, in the long term, be a good strategy for maintaining high pest suppression throughout the growing season.
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12. |
- Birkhofer, Klaus, et al.
(författare)
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Assessing spatiotemporal predator-prey patterns in heterogeneous habitats
- 2010
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 11:6, s. 486-494
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Tidskriftsartikel (refereegranskat)abstract
- Disentangling the contribution of biotic interactions (density-dependent) and environmental heterogeneity (density-independent) to the formation of spatial patterns between predators and prey is crucial for a better understanding of food-web interactions. Most techniques for the analysis of spatial patterns assume that abiotic processes influence the distribution of individuals with similar intensity at all locations of a study area (stationarity). This simplification may result in a spurious description of predator–prey associations in environmentally heterogeneoushabitats. In a spatially explicit way we sampled ground-active linyphiid and lycosid spiders and their Collembola prey along a forest-meadow gradient and analysed the change in spatial relationships with time. We used techniques of point pattern analysis and pair-correlation functions to summarize spatial patterns. To disentangle the contribution of biotic interactions and environmental heterogeneity on pattern formation we compared observed functions with those arising from null models either assuming environmental homogeneity or accounting for habitat heterogeneity. All taxa were aggregated at the three sampling periods if habitat homogeneity was assumed, but only linyphiid spiders were still clustered after accounting for environmental heterogeneity. A similarly contrasting result was present for the spatial relationship between predators and their prey, with association under the assumption of homogeneity, but strong repulsion that intensified with time if accounting for environmental heterogeneity. Results from additional bivariate null models under which either predator or prey locations were fixed, suggest that Collembola showed lower activity density in more suitable, but predator-rich habitats. Biotic interactions were important drivers of the spatial distribution of ground-active predators and their decomposer prey in the analysed forest floor food-web. However, these structuring forces remain hidden when using simple spatial models that ignore environmental heterogeneity. Therefore, for understanding predator–prey interactions in spatially complex habitats, such as grasslands and forests, spatial models considering habitat heterogeneity are indispensible.
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13. |
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14. |
- Birkhofer, Klaus, et al.
(författare)
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Conventional agriculture and not drought alters relationships between soil biota and functions
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Soil biodiversity constitutes the biological pillars of ecosystem services provided by soils worldwide. Soil life is threatened by intense agricultural management and shifts in climatic conditions as two important global change drivers which are not often jointly studied under field conditions. We addressed the effects of experimental short-term drought over the wheat growing season on soil organisms and ecosystem functions under organic and conventional farming in a Swiss long term trial. Our results suggest that activity and community metrics are suitable indicators for drought stress while microbial communities primarily responded to agricultural practices. Importantly, we found a significant loss of multiple pairwise positive and negative relationships between soil biota and process-related variables in response to conventional farming, but not in response to experimental drought. These results suggest a considerable weakening of the contribution of soil biota to ecosystem functions under long-term conventional agriculture. Independent of the farming system, experimental and seasonal (ambient) drought conditions directly affected soil biota and activity. A higher soil water content during early and intermediate stages of the growing season and a high number of significant relationships between soil biota to ecosystem functions suggest that organic farming provides a buffer against drought effects.
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15. |
- Birkhofer, Klaus, et al.
(författare)
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Cursorial spiders retard initial aphid population growth at low densities in winter wheat
- 2008
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Ingår i: Bulletin of Entomological Research. - 1475-2670. ; 98:3, s. 249-255
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Tidskriftsartikel (refereegranskat)abstract
- Generalist predators contribute to pest suppression in agroecosystems. Spider communities, which form a substantial fraction of the generalist predator fauna in arable land, are characterized by two functional groups: web-building and cursorial (non-web-building) species. We investigated the relative impact of these two functional groups on a common pest (Sitobion avenae, Aphididae) in wheat by combining a molecular technique that revealed species-specific aphid consumption rates with a factorial field experiment that analyzed the impact, separately and together, of equal densities of these two spider functional groups on aphid population growth. Only cursorial spiders retarded aphid population growth in our cage experiment, but this effect was limited to the initial aphid-population growth period and low-to-intermediate aphid densities. The molecular analysis, which used aphid-specific primers to detect aphid DNA in predator species, detected the highest proportion of aphid-consuming individuals in two cursorial spiders: the foliage-dwelling Xysticus cristatus (Thomisidae) and the ground-active Pardosa palustris (Lycosidae). The results suggest that manipulating the community composition in favour of pest-consuming functional groups may be more important for improving biological control than fostering predator biodiversity per se. Agricultural management practices that specifically foster effective species or functional groups (e.g. mulching for cursorial spiders) should receive more attention in low-pesticide farming systems.
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16. |
- Birkhofer, Klaus, et al.
(författare)
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Density-dependent and -independent effects on the joint use of space by predators and prey in terrestrial arthropod food-webs
- 2011
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 120:11, s. 1705-1711
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Tidskriftsartikel (refereegranskat)abstract
- The spatial distribution of predators and their prey is affected by their joint use of space. While the formation of such spatial patterns may be driven by density-dependent and -independent factors our knowledge on the contribution of different land-use activities on the formation of spatial patterns between predators and prey remains very limited. Agriculture is one of the most prevailing land-use activities with strong effects on invertebrate densities and structural habitat conditions. Here, we used replicated conventionally and organically managed winter wheat fields to investigate the effects of agricultural land-use on the spatial patterns of generalist predators and decomposer prey. We then identified the explanatory power of density-dependent (prey and predator activity density) and density-independent (vegetation structure) predictors for the observed spatial patterns. Generalist predators were regularly distributed only in conventionally managed fields and this pattern intensified with decreasing Collembola prey availability and increasing spider activity density. Segregation between carabid and spider predators was strongest in fields with lowest wheat plant height, suggesting more intense intraguild interactions in structurally less complex habitats. Collembola were aggregated independent of management and aggregation was strongest in fields with highest Collembola and carabid activity density. Spiders and Collembola prey were associated, but higher aphid densities under conventional management weakened or interrupted this spatial relationship. We conclude that active control of crop plant physiognomy by growth hormones and herbicides in conventionally managed fields promotes predator–predator segregation and that a high availability of aphid prey seems to decouple predator–Collembola prey associations. Our results emphasise the need for a more mechanistic understanding of the effects of land-use on the formation of spatial patterns and species interactions, especially under scenarios of environmental change and an ongoing loss of biodiversity.
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17. |
- Birkhofer, Klaus, et al.
(författare)
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Ecosystem services - current challenges and opportunities for ecological research
- 2015
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 2:12 January 2015
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Forskningsöversikt (refereegranskat)abstract
- e concept of ecosystem services was originally developed to illustrate the benefits that natural ecosystems generate for society and to raise awareness for biodiversity and ecosystem conservation. In this article we identify major challenges and opportunities for ecologists involved in empirical or modeling ecosystem service research. The first challenge arises from the fact that the ecosystem service concept has not been generated in the context of managed systems. Ecologists need to identify the effect of anthropogenic interventions in order to propose practices to benefit service-providing organisms and associated services. The second challenge arises from the need to evaluate relationships between indicators of ecosystem services that are collected in ecological studies while accounting for uncertainties of ecological processes that underlie these services. We suggest basing the assessment of ecosystem services on the utilization of sets of indicators that cover aspects of service-providing units, ecosystem management and landscape modification. The third challenge arises from the limited understanding of the nature of relationships between services and a lack of a general statistical framework to address these links. To manage ecosystem service provisioning, ecologists need to establish whether services respond to a shared driver or if services are directly linked to each other. Finally, studies relating biodiversity to ecosystem services often focus on services at small spatial or short temporal scales, but research on the protection of services is often directed toward services providing benefits at large spatial scales. Ecological research needs to address a range of spatial and temporal scales to provide a multifaceted understanding of how nature promotes human well-being. Addressing these challenges in the future offers a unique opportunity for ecologists to act as promoters for the understanding about how to conserve benefits gained from nature.
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18. |
- Birkhofer, Klaus, et al.
(författare)
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Effects of extreme climatic events on small-scale spatial patterns: a 20-year study of the distribution of a desert spider.
- 2012
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 170:3, s. 651-657
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Tidskriftsartikel (refereegranskat)abstract
- Individuals of most animal species are non-randomly distributed in space. Extreme climatic events are often ignored as potential drivers of distribution patterns, and the role of such events is difficult to assess. Seothyra henscheli (Araneae, Eresidae) is a sedentary spider found in the Namib dunes in Namibia. The spider constructs a sticky-edged silk web on the sand surface, connected to a vertical, silk-lined burrow. Above-ground web structures can be damaged by strong winds or heavy rainfall, and during dispersal spiders are susceptible to environmental extremes. Locations of burrows were mapped in three field sites in 16 out of 20 years from 1987 to 2007, and these grid-based data were used to identify the relationship between spatial patterns, climatic extremes and sampling year. According to Morisita's index, individuals had an aggregated distribution in most years and field sites, and Geary's C suggests clustering up to scales of 2 m. Individuals were more aggregated in years with high maximum wind speed and low annual precipitation. Our results suggest that clustering is a temporally stable property of populations that holds even under fluctuating burrow densities. Climatic extremes, however, affect the intensity of clustering behaviour: individuals seem to be better protected in field sites with many conspecific neighbours. We suggest that burrow-site selection is driven at least partly by conspecific cuing, and this behaviour may protect populations from collapse during extreme climatic events.
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19. |
- Birkhofer, Klaus, et al.
(författare)
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Effects of Ground Cover Management on Biotic Communities, Ecosystem Services and Disservices in Organic Deciduous Fruit Orchards in South Africa
- 2019
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Ingår i: Frontiers in Sustainable Food Systems. - : Frontiers Media SA. - 2571-581X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Organic orchards may have higher biodiversity and levels of ecosystem services compared to conventionally managed orchards. However, it is not well-understood how management decisions within organic orchards alter biotic communities and ecosystem services. The simultaneous provision of individual ecosystem services and mitigation of disservices is crucial for organic growers who cannot replace natural regulatory processes by artificial inputs. This study addresses one of the major constraints for organic fruit production in South Africa, namely the availability of strategies for pest control and nutrient management in soils. Partly due to these constraints, organic certification of deciduous fruits is very uncommon in South Africa and limited our selection of study plots. A field experiment on a single farm was established to study the impact of a treatment with dead organic mulch compared to controls on the composition of biotic communities, the simultaneous provision of ecosystem services, and the mitigation of disservices in five organic deciduous fruit orchards in the Western Cape province. Mulching did not significantly reduce weed cover or alter the taxonomic composition of weed communities, but affected soil organisms. Mulched subplots had significantly higher densities of Collembola and phytophagous nematodes and lower microbial activity and woodlice numbers. Independent of mulch treatment, both orchard type (conventional: apricot and organic: apricot, peach, plum, and quince) and weed cover had pronounced effects on the composition of biotic communities and ecosystem service and disservice potentials. The community composition of plants, microbes and web-building spiders differed significantly between organically and conventionally managed plots. The composition of communities and levels of ecosystem service and disservice potentials also differed significantly between organic orchards of different fruit type. Two potential pest groups (phytophagous nematodes and arthropods) were most abundant in peach subplots with high weed cover and tree age and least abundant in conventionally managed apricot plots. These results emphasize the crucial importance to consider weed-microbe-animal interactions when developing management practices in organic orchards. Management decisions in organic orchards hold the potential to affect biotic communities to the benefit of pest control and soil nutrient services, but can also result in unexpected detrimental effects on ecosystem services.
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20. |
- Birkhofer, Klaus, et al.
(författare)
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Environmental Impacts of Organic Farming
- 2016
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Ingår i: eLS. - : Wiley. - 9780470015902 ; , s. 1-7
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Organic agriculture is a production system that aims at sustaining healthy soils, ecosystems and people by prohibiting the application of synthetic pesticides and fertilisers in crop production and by emphasising animal welfare in livestock breeding. This article shows that organic agriculture is characterised by higher soil quality and reduced nutrient or pesticide leaching compared to nonorganic agriculture, but that positive effects on biological control services or emission of greenhouse gases are less evident. Yield gaps between organic and nonorganic agriculture are on average 20%, but vary between crops and regions. Given the environmental risks that are associated with intensive, nonorganic agriculture, farming practices should be modified to decrease risks. Organic agriculture can be a more environmentally friendly alternative, but individual farming practices need improvement to meet the demands of a growing human population. Further growth of the organic farming sector will contribute to reduce the negative environmental impact of agriculture.
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21. |
- Birkhofer, Klaus, et al.
(författare)
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General Relationships between Abiotic Soil Properties and Soil Biota across Spatial Scales and Different Land-Use Types.
- 2012
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- Very few principles have been unraveled that explain the relationship between soil properties and soil biota across large spatial scales and different land-use types. Here, we seek these general relationships using data from 52 differently managed grassland and forest soils in three study regions spanning a latitudinal gradient in Germany. We hypothesize that, after extraction of variation that is explained by location and land-use type, soil properties still explain significant proportions of variation in the abundance and diversity of soil biota. If the relationships between predictors and soil organisms were analyzed individually for each predictor group, soil properties explained the highest amount of variation in soil biota abundance and diversity, followed by land-use type and sampling location. After extraction of variation that originated from location or land-use, abiotic soil properties explained significant amounts of variation in fungal, meso- and macrofauna, but not in yeast or bacterial biomass or diversity. Nitrate or nitrogen concentration and fungal biomass were positively related, but nitrate concentration was negatively related to the abundances of Collembola and mites and to the myriapod species richness across a range of forest and grassland soils. The species richness of earthworms was positively correlated with clay content of soils independent of sample location and land-use type. Our study indicates that after accounting for heterogeneity resulting from large scale differences among sampling locations and land-use types, soil properties still explain significant proportions of variation in fungal and soil fauna abundance or diversity. However, soil biota was also related to processes that act at larger spatial scales and bacteria or soil yeasts only showed weak relationships to soil properties. We therefore argue that more general relationships between soil properties and soil biota can only be derived from future studies that consider larger spatial scales and different land-use types.
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22. |
- Birkhofer, Klaus, et al.
(författare)
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Generalist predators in organically and conventionally managed grass-clover fields: implications for conservation biological control
- 2008
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Ingår i: Annals of Applied Biology. - : Wiley. - 0003-4746 .- 1744-7348. ; 153:2, s. 271-280
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Tidskriftsartikel (refereegranskat)abstract
- Organically managed agroecosystems rely in part on biological control to prevent pest outbreaks. Generalist predators (Araneae, Carabidae and Staphylinidae) are a major component of the natural enemy community in agroecosystems. We assessed the seasonal dynamics of major generalist predator groups in conventionally and organically managed grass–clover fields that primarily differed by fertilisation strategy. We further established an experiment, manipulating the abundant wolf spider genus Pardosa, to identify the importance of these predators for herbivore suppression in the same system and growth period. Organic management significantly enhanced ground-active spider numbers early and late in the growing season, with potentially positive effects of plant cover and non-pest decomposer prey. However, enhancing spider numbers in the field experiment did not improve biological control in organically managed grass–clover fields. Similar to the survey results, reduced densities of Pardosa had no short-term effect on any prey taxa; however, spider guild structure changed in response to Pardosa manipulation. In the presence of fewer Pardosa, other ground-running spiders were more abundant; therefore, their impact on herbivore numbers may have been elevated, possibly cancelling increases in herbivore numbers because of reduced predation by Pardosa. Our results indicate positive effects of organic farming on spider activity density; however, our survey data and the predator manipulation experiment failed to find evidence that ground-running spiders reduced herbivore numbers. We therefore suggest that a positive impact of organic fertilisers on wolf spiders in grass–clover agroecosystems may not necessarily improve biological control when compared with conventional farming.
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23. |
- Birkhofer, Klaus, et al.
(författare)
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Global metawebs of spider predation highlight consequences of land-use change for terrestrial predator–prey networks
- 2017
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Ingår i: Adaptive Food Webs : Stability and Transitions of Real and Model Ecosystems - Stability and Transitions of Real and Model Ecosystems. - : Cambridge University Press. - 9781316871867 - 9781107182110 ; , s. 193-213
-
Bokkapitel (refereegranskat)abstract
- Land-Use Change and Terrestrial Predator–Prey Networks Land-use change, here defined as the conversion of one land-use type into another (e.g., forest to arable land), affects biodiversity and biotic interactions worldwide (Sala et al., 2000). Although there has been large regional variation in the extent of agricultural expansion and abandonment in Europe in the past 50 years (Rabbinge and van Diepen, 2000), there has been a general trend that forest has expanded at the expense of agricultural land (Kankaanpäa and Carter, 2004; Rounsevell et al., 2006). The patterns have been similar in North America the past decades (Smith et al., 2010). Globally, particularly in developing countries, the general pattern has instead been agricultural expansion (Smith et al., 2010), threatening forest ecosystems (DeFries et al., 2010; Lambin and Meyfroidt, 2011; but see Angelsen, 2010). In fact, models predict an increase of cropland between 10 and 25% up to 2050, mainly due to agricultural expansion in developing countries (Schmitz et al., 2014). Natural and semi-natural non-forest ecosystems are primarily threatened by a conversion to pasture land (Schmitz et al., 2014) or by cultivation with biofuels (Havlík et al., 2011). Climate change is an important additional driver of land-use conversion, as the range of crop species contract or expand (Olesen and Bindi, 2002) and as forests adapt to changing climatic conditions (Spittlehouse and Stewart, 2004). In the past, effects of land-use change were often exclusively assessed by their impact on species richness (Tilman et al., 2001). Today, it has increasingly become evident that we need metrics that capture additional features of biological communities to understand consequences of land-use change on ecosystem functions and the provision of ecosystem services (Tylianakis et al., 2007; Diehl et al., 2013). Trophic interactions that link species in food webs are important components that modulate functions provided by biological communities (Laliberté and Tylianakis, 2010; Tylianakis et al., 2010; Thompson et al., 2012). For example, the loss of large apex predators from an ecosystem due to anthropogenic disturbance may cascade through the food chain and lead to drastic effects on primary producers (Estes et al., 2011). Predator populations are often severely affected by anthropogenic disturbances (Attwood et al., 2008). Consequently, the conversion from one major land-use type into another may alter predator–prey interactions (Ives et al., 2005) and the provision of predator-mediated ecosystem services such as the control of agricultural pests (conservation biological control; Barbosa, 1998).
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24. |
- Birkhofer, Klaus, et al.
(författare)
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Grassy margins along organically managed cereal fields foster trait diversity and taxonomic distinctness of arthropod communities
- 2014
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Ingår i: Insect Conservation and Diversity. - : Wiley. - 1752-4598 .- 1752-458X. ; 7:3, s. 274-287
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Tidskriftsartikel (refereegranskat)abstract
- It is not known if grassy margins contribute to the conservation of biodiversity if situated along organically managed cereal fields as the contrast in environmental conditions between fields and margins may be too small in absence of pesticide applications. Communities of spiders, ground beetles, true bugs and aphids were sampled in 2years along transects from the centre of organically managed cereal fields into adjacent grassy margins. Based on species richness, abundances, ecological and body size traits of species and taxonomic distinctness between species, communities were compared between organically managed cereal fields and their grassy margins. The species richness, abundance and variation in taxonomic distinctness of true bugs were significantly higher in grassy margins. For spiders and ground beetles, these metrics were either higher in cereal fields or did not differ significantly. At the species level, spiders living under stones or in soil crevices, as well as phytophagous ground beetles and true bugs that overwinter as eggs benefited from grassy margins. True bug communities in cereal fields were dominated by a few abundant species, whereas communities in margins were rather dominated by a few large species. Our comprehensive analyses highlight the importance of accounting for species identities and biology in biodiversity studies. The traits that characterised arthropod species that benefited from margins are not characteristic for pest species. Grassy margins along organic fields therefore represent an important agri-environmental scheme for the conservation of several arthropod taxa and margins should not be removed to increase the crop production area in organically managed cereal fields.
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25. |
- Birkhofer, Klaus, et al.
(författare)
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Land-use effects on the functional distinctness of arthropod communities
- 2015
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 38:9, s. 889-900
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Tidskriftsartikel (refereegranskat)abstract
- Land-use change is a major driver of the global loss of biodiversity, but it is unclear to what extent this also results in a loss of ecological traits. Therefore, a better understanding of how land-use change affects ecological traits is crucial for efforts to sustain functional diversity. To this end we tested whether higher species richness or taxonomic distinctness generally leads to increased functional distinctness and whether intensive land use leads to functionally more narrow arthropod communities. We compiled species composition and trait data for 350 species of terrestrial arthropods (Araneae, Carabidae and Heteroptera) in different land-use types (forests, grasslands and arable fields) of low and high land-use intensity. We calculated the average functional and taxonomic distinctness and the rarified trait richness for each community. These measures reflect the range of traits, taxonomic relatedness and number of traits that are observed in local communities. Average functional distinctness only increased significantly with species richness in Carabidae communities. Functional distinctness increased significantly with taxonomic distinctness in communities of all analyzed taxa suggesting a high functional redundancy of taxonomically closely related species. Araneae and Heteroptera communities had the expected lower functional distinctness at sites with higher land-use intensity. More frequently disturbed land-use types such as managed grasslands or arable fields were characterized by species with smaller body sizes and higher dispersal abilities and communities with lower functional distinctness or trait richness. Simple recommendations about the conservation of functional distinctness of arthropod communities in the face of future land-use intensification and species loss are not possible. Our study shows that these relationships depend on the studied taxa and land-use type. However, for some arthropod groups functional distinctness is threatened by intensification and conversion from less to more frequently disturbed land-uses.
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26. |
- Birkhofer, Klaus, et al.
(författare)
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Land-use type and intensity differentially filter traits in above- and below-ground arthropod communities
- 2017
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Ingår i: Journal of Animal Ecology. - : Wiley. - 0021-8790 .- 1365-2656. ; 86:3, s. 511-520
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Tidskriftsartikel (refereegranskat)abstract
- Along with the global decline of species richness goes a loss of ecological traits. Associated biotic homogenization of animal communities and narrowing of trait diversity threaten ecosystem functioning and human well-being. High management intensity is regarded as an important ecological filter, eliminating species that lack suitable adaptations. Below-ground arthropods are assumed to be less sensitive to such effects than above-ground arthropods. Here, we compared the impact of management intensity between (grassland vs. forest) and within land-use types (local management intensity) on the trait diversity and composition in below- and above-ground arthropod communities. We used data on 722 arthropod species living above-ground (Auchenorrhyncha and Heteroptera), primarily in soil (Chilopoda and Oribatida) or at the interface (Araneae and Carabidae). Our results show that trait diversity of arthropod communities is not primarily reduced by intense local land use, but is rather affected by differences between land-use types. Communities of Auchenorrhyncha and Chilopoda had significantly lower trait diversity in grassland habitats as compared to forests. Carabidae showed the opposite pattern with higher trait diversity in grasslands. Grasslands had a lower proportion of large Auchenorrhyncha and Carabidae individuals, whereas Chilopoda and Heteroptera individuals were larger in grasslands. Body size decreased with land-use intensity across taxa, but only in grasslands. The proportion of individuals with low mobility declined with land-use intensity in Araneae and Auchenorrhyncha, but increased in Chilopoda and grassland Heteroptera. The proportion of carnivorous individuals increased with land-use intensity in Heteroptera in forests and in Oribatida and Carabidae in grasslands. Our results suggest that gradients in management intensity across land-use types will not generally reduce trait diversity in multiple taxa, but will exert strong trait filtering within individual taxa. The observed patterns for trait filtering in individual taxa are not related to major classifications into above- and below-ground species. Instead, ecologically different taxa resembled each other in their trait diversity and compositional responses to land-use differences. These previously undescribed patterns offer an opportunity to develop management strategies for the conservation of trait diversity across taxonomic groups in permanent grassland and forest habitats.
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27. |
- Birkhofer, Klaus, et al.
(författare)
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Long-term organic farming fosters below and aboveground biota: Implications for soil quality, biological control and productivity
- 2008
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 40:9, s. 2297-2308
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Tidskriftsartikel (refereegranskat)abstract
- Organic farming may contribute substantially to future agricultural production worldwide by improving soil quality and pest control, thereby reducing environmental impacts of conventional farming. We investigated in a comprehensive way soil chemical, as well as below and aboveground biological parameters of two organic and two conventional wheat farming systems that primarily differed in fertilization and weed management strategies. Contrast analyses identified management related differences between "herbicide-free" bioorganic (BIOORG) and biodynamic (BIODYN) systems and conventional systems with (CONFYM) or without manure (CONMIN) and herbicide application within a long-term agricultural experiment (DOK trial, Switzerland). Soil carbon content was significantly higher in systems receiving farmyard manure and concomitantly microbial biomass (fungi and bacteria) was increased. Microbial activity parameters, such as microbial basal respiration and nitrogen mineralization, showed an opposite pattern, suggesting that soil carbon in the conventional system (CONFYM) was more easily accessible to microorganisms than in organic systems. Bacterivorous nematodes and earthworms were most abundant in systems that received farmyard manure, which is in line with the responses of their potential food sources (microbes and organic matter). Mineral fertilizer application detrimentally affected enchytraeids and Diptera larvae, whereas aphids benefited. Spider abundance was favoured by organic management, most likely a response to increased prey availability from the belowground subsystem or increased weed coverage. In contrast to most soil-based, bottom-up controlled interactions, the twofold higher abundance of this generalist predator group in organic systems likely contributed to the significantly lower abundance of aboveground herbivore pests (aphids) in these systems. Long-term organic farming and the application of farmyard manure promoted soil quality, microbial biomass and fostered natural enemies and ecosystem engineers, suggesting enhanced nutrient cycling and pest control. Mineral fertilizers and herbicide application, in contrast, affected the potential for top-down control of aboveground pests negatively and reduced the organic carbon levels. Our study indicates that the use of synthetic fertilizers and herbicide application changes interactions within and between below and aboveground components, ultimately promoting negative environmental impacts of agriculture by reducing internal biological cycles and pest control. On the contrary, organic farming fosters microbial and faunal decomposers and this propagates into the aboveground system via generalist predators thereby increasing conservation biological control. However, grain and straw yields were 23% higher in systems receiving mineral fertilizers and herbicides reflecting the trade-off between productivity and environmental responsibility. (C) 2008 Elsevier Ltd. All rights reserved.
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28. |
- Birkhofer, Klaus, et al.
(författare)
-
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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29. |
- Birkhofer, Klaus, et al.
(författare)
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Relationships between multiple biodiversity components and ecosystem services along a landscape complexity gradient
- 2018
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Ingår i: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 218, s. 247-253
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Tidskriftsartikel (refereegranskat)abstract
- The assessment of effects of anthropogenic disturbance on biodiversity (BD) and ecosystem services (ES) and their relationships are key priorities of the Intergovernmental Panel for Biodiversity and Ecosystem Services. Agricultural landscapes and their associated BD provide multiple ES and it is crucial to understand how relationships between ES and BD components change along gradients of landscape complexity. In this study, we related eight ES potentials to the species richness of five invertebrate, vertebrate and plant taxonomic groups in cereal farming systems. The landscape complexity gradient ranged from areas dominated by annually tilled arable land to areas with high proportions of unfertilized, non-rotational pastures and uncultivated field borders. We show that after accounting for landscape complexity relationships between yield and bird richness or biological control became more positive, but relationships between bird richness and biological control became less positive. The relationship between bird and plant richness turned from positive to negative. Multidiversity (overall biodiversity), was positively related to landscape complexity, whereas multifunctionality (overall ES provision), was not significantly related to either one of these. Our results suggest that multidiversity can be promoted by increasing landscape complexity; however; we found no support for a simultaneous increase of several individual ES, BD components or multifunctionality. These results challenge the assumption that bio-diversity-friendly landscape management will always simultaneously promote multiple ES in agricultural landscapes. Future studies need to verify this pattern by using multi-year data, larger sets of ES and BD components and a study design that is appropriate to address larger spatial scales and relationships in several regions.
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30. |
- Birkhofer, Klaus, et al.
(författare)
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Small-scale spatial pattern of web-building spiders (Araneae) in alfalfa: Relationship to disturbance from cutting, prey availability, and intraguild interactions
- 2007
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Ingår i: Environmental Entomology. - 1938-2936. ; 36:4, s. 801-810
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the development of spatial patterns in generalist predators will improve our ability to incorporate them into biological control programs. We studied the small-scale spatial patterns of spider webs in alfalfa by analyzing the relationship between web locations over distances ranging from 4 to 66 cm. Using a coordinate-based spatial statistic (O-ring) and assuming a heterogeneous distribution of suitable web sites, we analyzed the impact of cutting and changes in spider abundance on web distribution. We analyzed the influence of small-scale variation in prey availability by comparing web distributions to the pattern of sticky-trap captures of Aphididae and Diptera described by a count-based spatial statistic (SADIE). Cutting of alfalfa reduced the overall density of web-building spiders but had no immediate impact on the spatial distribution of their webs. Availability of aphids was highest before the alfalfa was cut and was clumped at a scale of 66 cm. Spider webs, however, were not clumped at any scale or date. In contrast, webs were regularly distributed at smaller distances (<20 cm) immediately before and after cutting. Because cursorial and web-building spiders were most active during this period, we hypothesize that the development of small-scale regularity in web locations was driven by intraguild interactions. Our results suggest that intraguild interactions contribute to the development of small-scale spatial patterns of spider webs in alfalfa. Variation in prey availability may have more of an influence on web distribution in crops with a different vegetation structure or if patterns are studied at larger spatial scales.
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31. |
- Birkhofer, Klaus, et al.
(författare)
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Soil fauna feeding activity in temperate grassland soils increases with legume and grass species richness
- 2011
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 43:10, s. 2200-2207
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Tidskriftsartikel (refereegranskat)abstract
- Edaphic fauna contributes to important ecosystem functions in grassland soils such as decomposition and nutrient mineralization. Since this functional role is likely to be altered by global change and associated shifts in plant communities, a thorough understanding of large scale drivers on below-ground processes independent of regional differences in soil type or climate is essential. We investigated the relationship between abiotic (soil properties, management practices) and biotic (plant functional group composition, vegetation characteristics, soil fauna abundance) predictors and feeding activity of soil fauna after accounting for sample year and study region. Our study was carried out over a period of two consecutive years in 92 agricultural grasslands in three regions of Germany, spanning a latitudinal gradient of more than 500 km. A structural equation model suggests that feeding activity of soil fauna as measured by the bait-lamina test was positively related to legume and grass species richness in both years. Most probably, a diverse vegetation promotes feeding activity of soil fauna via alterations of both microclimate and resource availability. Feeding activity of soil fauna also increased with earthworm biomass via a pathway over Collembola abundance. The effect of earthworms on the feeding activity in soil may be attributed to their important role as ecosystem engineers. As no additional effects of agricultural management such as fertilization, livestock density or number of cuts on bait consumption were observed, our results suggest that the positive effect of legume and grass species richness on the feeding activity in soil fauna is a general one that will not be overruled by regional differences in management or environmental conditions. We thus suggest that agri-environment schemes aiming at the protection of belowground activity and associated ecosystem functions in temperate grasslands may generally focus on maintaining plant diversity, especially with regard to the potential effects of climate change on future vegetation structure.
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32. |
- Birkhofer, Klaus, et al.
(författare)
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Spatial-pattern analysis in a territorial spider: evidence for multi-scale effects
- 2006
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 29:5, s. 641-648
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Tidskriftsartikel (refereegranskat)abstract
- Territorial animals maintain a certain distance to neighbouring conspecifics, presumably leading to a regular spatial pattern through social spacing. Nevertheless, most animal populations are assumed to show aggregation at certain distance ranges, reflecting the scale dependency of spatial patterns. Leucorchestris arenicola (Araneae: Sparassidae) is a burrow-living spider species that shows territorial behaviour against conspecifics. A multi-scale approach in spatial analysis revealed that territory owners had fewer neighbours than expected under spatial randomness at distances up to 6 m. Behavioural field experiments showed that territory owners were able to perceive and react to burrow constructing neighbours up to at least 4 m distance from their own burrow. At larger distances individuals were often more aggregated than expected under spatial randomness. Analysing adult and immature relationships showed attraction between different development stages at small distances and avoidance at larger distances. The analysis reveals diverse spatial patterns in a territorial and cannibalistic species, showing that both behaviour and environment affect pattern development at different distances. The study outlines the importance of multi-scale approaches for spatial analysis and the need for accompanying experiments to facilitate the interpretation of results.
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33. |
- Birkhofer, Klaus, et al.
(författare)
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Subsidy from the Detrital Food Web, but Not Microhabitat Complexity, Affects the Role of Generalist Predators in an Aboveground Herbivore Food Web
- 2008
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 117:4, s. 494-500
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Tidskriftsartikel (refereegranskat)abstract
- The activity and density of generalist predators, such as carabid beedes, rove beedes and spiders, may increase in response to: (1) increased availability of prey from the belowground subsystem and/ or (2) enhanced complexity of aboveground vegetation. Organic farming practices support decomposer populations and enhance habitat complexity due to an increased weed density. A response by generalist predators to such below-or aboveground changes could affect predation rates on herbivores in the aboveground food web. We tested this hypothesis in a replicated field experiment conducted in a winter wheat field, where increased predator activity could lead to improved control of herbivorous pests. In a crossed design, we increased and lowered densities of decomposer prey, and manipulated vegetation complexity using artificial plants in order to examine the effect of structural complexity in isolation from effects of plant-attracted additional prey. Isotomid Collembola exhibited lowest activity-densities (AD) in plots treated with soil insecticide and had gradually increasing AD in untreated plots and plots receiving detrital subsidies. Carabid beedes and cursorial spiders did not respond to increased availability of isotomid prey, and they unexpectedly displayed higher AD in the structurally less-complex plots. Aphid density mirrored the positive response of isotomids to detrital subsidies, suggesting that aphids benefited from reduced predation due to predators switching to abundant prey in the decomposer subsystem. The absence of a numerical response by surface-active predators apparendy strengthened this indirect effect of isotomids on aphids. Our results suggest that indirect predator-mediated prey-prey interactions can reduce beneficial effects of detrital subsidies on pest suppression. We further demonstrated that generalist predators may not per se benefit from structural complexity. Both results document the challenges associated with management practices that support generalist predators, as these measures may not necessarily improve herbivore suppression.
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34. |
- Birkhofer, Klaus, et al.
(författare)
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The contribution of CAP greening measures to conservation biological control at two spatial scales
- 2018
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Ingår i: Agriculture, Ecosystems and Environment. - : Elsevier BV. - 0167-8809. ; 255, s. 84-94
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Tidskriftsartikel (refereegranskat)abstract
- To promote a more sustainable agricultural production, the European Commission implemented direct payments that require farmers to implement greening measures aimed at reducing negative effects of agriculture on the environment and biodiversity. These greening measures (including fallows and permanent grasslands) have been criticised for their potential inability to conserve biodiversity and promote associated ecosystem services. In this study, we investigate if the presence of old or recently established fallows and permanent grassland in the landscape are beneficial for the emergence, activity density and spillover of ground-running natural enemies and as a result aphid biological control in cereal fields. Lycosidae and Theridiidae were more numerous in fallows (emergence & activity density) compared to crop fields, while Staphylinidae and Linyphiidae showed opposite patterns. Spillover of Lycosidae was significantly higher from fallows into cereal fields, than between cereal fields. As a result of the opposite patterns in activity density in fallows between different groups of predators, a spillover from fallows did not result in a significantly higher aphid control in crop fields adjacent to them. A high proportion of permanent grassland in the landscape resulted in lower emergence of Linyphiidae and Carabidae. Our results support the assumption that a higher emergence and activity density of ground-running predators generally results in higher spillover to adjacent fields. However, patterns of emergence and activity density differed between individual natural enemy groups. Fallows, independent of age, can therefore act as source or sink depending on the focal predator group and more permanent grassland in the landscape can result in lower local emergence. Fallows at the local scale and permanent grassland at larger spatial scales therefore did not generally promote aphid biological control services provided by ground-running natural enemies.
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35. |
- Birkhofer, Klaus, et al.
(författare)
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Winners and losers of organic cereal farming in animal communities across Central and Northern Europe
- 2014
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Ingår i: Biological Conservation. - : Elsevier BV. - 1873-2917 .- 0006-3207. ; 175, s. 25-33
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Forskningsöversikt (refereegranskat)abstract
- Organic farming is promoted as a sustainable alternative to conventional farming, with positive effects on the diversity of plants and selected animal taxa. Here, we used a literature survey to collect presence/absence data on the composition of farmland bird, ground beetle, spider as well as butterfly and moth communities from 28 independent studies to identify genera and (sub-)families that had either higher (winners) or lower (losers) species richness under organic farming. We further tested if the taxonomic breadth of communities and the number of species of conservation concern differed between farming systems and if climate or fertilization intensity altered responses of animal communities to organic farming. Our results suggest that there are both winners and losers of organic farming and that this effect depends on whether taxa are predaceous (losers) or exclusively feed on plant material (winners). Organic farming did not lead to a higher number of exclusive species, but significantly more species of conservation concern were observed under organic farming. Organic farming consistently led to a slightly higher taxonomic breadth of bird communities. Finally, we did not find support that local long-term climatic conditions or differences in fertilization rates between farming systems altered the effect of organic farming. Overall, we did not find strong support for general positive effects of organic farming on animal diversity in the analysed groups across Central and Northern Europe. (C) 2014 Elsevier Ltd. All rights reserved.
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36. |
- Dahms, Henriette, et al.
(författare)
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Contrasting diversity patterns of epigeic arthropods between grasslands of high and low agronomic potential
- 2010
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 11:1, s. 6-14
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedIncreasing demand for food, fuel and fibre promotes the intensification of land-use, particularly in areas favourable for agricultural production. In less-favourable areas, more wildlife-friendly farming systems are often either abandoned or under pressure of conversion, e.g. for bioenergy production. This raises the question, to which extent areas of different agronomicpotential contribute to regional biodiversity. To approach this question on a regional scale, we established our study within a region where sites of high and lowagronomicpotential (AP) alternate on a small spatial scale. We selected 13 high-AP and 13 low-AP grasslands to quantify the contribution of these classes to the regional diversity of four epigeicarthropod taxa (ants, springtails, functional groups of ground beetles, and spiders). The regional diversity (γ) was partitioned into species richness per site (α-diversity), diversity among sites within one class (βwithin-diversity), and diversity between the two classes (βbetween-diversity). The β-diversity generally accounted for the largest share of the γ-diversity, with patterns of diversity components being highly taxon- and class-specific. Carnivorous carabids had a higherα-diversity at high-AP sites. Ants, springtails, and cursorial spiders had a higherβwithin-diversity in low-AP grasslands. Low-AP sites also harboured many more species that occurred exclusively in one grassland class. We conclude that grasslands that may be unfavourable for agricultural production contributed more to regional diversity of epigeicarthropods than favourable grasslands. We therefore suggest that future agricultural schemes should promote arthropod biodiversity by specifically targeting agri-environment schemes or other wildlife-friendly farming approaches to areas of lowagronomicpotential, since this bears the greatest potential to preserve a comparatively high species turnover (β-diversity) and in consequence high regional diversity.
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37. |
- de Vries, Franciska T., et al.
(författare)
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Soil food web properties explain ecosystem services across European land use systems
- 2013
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Ingår i: Proceedings of the National Academy of Sciences. - Washington, DC : Proceedings of the National Academy of Sciences. - 1091-6490 .- 0027-8424. ; 110:35, s. 14296-14301
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Tidskriftsartikel (refereegranskat)abstract
- Intensive land use reduces the diversity and abundance of many soil biota, with consequences for the processes that they govern and the ecosystem services that these processes underpin. Relationships between soil biota and ecosystem processes have mostly been found in laboratory experiments and rarely are found in the field. Here, we quantified, across four countries of contrasting climatic and soil conditions in Europe, how differences in soil food web composition resulting from land use systems (intensive wheat rotation, extensive rotation, and permanent grassland) influence the functioning of soils and the ecosystem services that they deliver. Intensive wheat rotation consistently reduced the biomass of all components of the soil food web across all countries. Soil food web properties strongly and consistently predicted processes of C and N cycling across land use systems and geographic locations, and they were a better predictor of these processes than land use. Processes of carbon loss increased with soil food web properties that correlated with soil C content, such as earthworm biomass and fungal/bacterial energy channel ratio, and were greatest in permanent grassland. In contrast, processes of N cycling were explained by soil food web properties independent of land use, such as arbuscular mycorrhizal fungi and bacterial channel biomass. Our quantification of the contribution of soil organisms to processes of C and N cycling across land use systems and geographic locations shows that soil biota need to be included in C and N cycling models and highlights the need to map and conserve soil biodiversity across the world.
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38. |
- 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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39. |
- Diehl, Eva, et al.
(författare)
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Management intensity and vegetation complexity affect web-building spiders and their prey
- 2013
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 1432-1939 .- 0029-8549. ; 173:2, s. 579-589
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Tidskriftsartikel (refereegranskat)abstract
- Agricultural management and vegetation complexity affect arthropod diversity and may alter trophic interactions between predators and their prey. Web-building spiders are abundant generalist predators and important natural enemies of pests. We analyzed how management intensity (tillage, cutting of the vegetation, grazing by cattle, and synthetic and organic inputs) and vegetation complexity (plant species richness, vegetation height, coverage, and density) affect rarefied richness and composition of web-building spiders and their prey with respect to prey availability and aphid predation in 12 habitats, ranging from an uncut fallow to a conventionally managed maize field. Spiders and prey from webs were collected manually and the potential prey were quantified using sticky traps. The species richness of web-building spiders and the order richness of prey increased with plant diversity and vegetation coverage. Prey order richness was lower at tilled compared to no-till sites. Hemipterans (primarily aphids) were overrepresented, while dipterans, hymenopterans, and thysanopterans were underrepresented in webs compared to sticky traps. The per spider capture efficiency for aphids was higher at tilled than at no-till sites and decreased with vegetation complexity. After accounting for local densities, 1.8 times more aphids were captured at uncut compared to cut sites. Our results emphasize the functional role of web-building spiders in aphid predation, but suggest negative effects of cutting or harvesting. We conclude that reduced management intensity and increased vegetation complexity help to conserve local invertebrate diversity, and that web-building spiders at sites under low management intensity (e.g., semi-natural habitats) contribute to aphid suppression at the landscape scale.
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40. |
- Diekötter, Tim, et al.
(författare)
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Landscape and management effects on structure and function of soil arthropod communities in winter wheat
- 2010
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Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 1873-2305 .- 0167-8809. ; 137:1-2, s. 108-112
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the impact of agricultural management (organic vs. conventional) and landscape context on species richness and abundance of five soilarthropod taxa (ground beetles, spiders, springtails, millipedes, woodlice) and associated ecosystem functions (soil biological activity, weed seed predation, litter decomposition). A significant interaction between management type and landscape context was revealed in several cases. Activity density of millipedes and wood lice and species richness of ground beetles were higher in fields where local and regional management types were complementary, indicating a beneficial effect of environmental heterogeneity. In addition, seed predation on arable weeds was higher in organically than conventionally managed fields. It is concluded that the effect of agricultural management on soilarthropod biodiversity and functioning is often context dependent. The diversity of functionally important taxa such as ground beetles and decomposers may be enhanced by increasing environmental heterogeneity, a measure that is also beneficial for other components of agrobiodiversity. Thus, in a conventional agricultural context even managing only a fraction of fields organically may help to increase environmental heterogeneity and thereby promote soilarthropod diversity and the associated ecosystem functions.
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41. |
- Diekötter, Tim, et al.
(författare)
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Organic farming affects the potential of a granivorous carabid beetle to control arable weeds at local and landscape scales
- 2016
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Ingår i: Agricultural and Forest Entomology. - : Wiley. - 1461-9555. ; 18:2, s. 167-173
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Tidskriftsartikel (refereegranskat)abstract
- Organic farming not only increases plant diversity, but also simultaneously promotes biological weed control through provisioning of ample resources to seed predators. Harpalus affinis (Schrank, 1781) was collected from organically or conventionally managed winter-wheat fields with high or low surrounding shares of organic fields, aiming to test the impact of agricultural management on its activity density, body size and nutritional condition. Body size and nutritional condition were then related to the arable weed seed predation of this granivorous carabid beetle. Activity density of H. affinis was 3.5-fold higher in organically compared with conventionally managed fields, if these were primarily surrounded by conventional fields. Body size was larger in fields surrounded by large proportions of organically managed land, independent of local management. The nutritional condition of beetles was unaffected by local or landscape scale farming. Per capita seed predation significantly increased with body size, whereas nutritional condition had no effect. The results of the present study suggest that organic farming at local and landscape scales enhances the potential of species to control arable weeds by increasing activity densities and intraspecific body size. Seed predation therefore not only depends on local and landscape effects on the community composition of local guilds of granivores, but also on the contribution of individual species to this important ecosystem service.
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42. |
- Dänhardt, Juliana, et al.
(författare)
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Ekosystemtjänster i det skånska jordbrukslandskapet
- 2013
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Rapport (populärvet., debatt m.m.)abstract
- Jordbrukslandskapet tillhandahåller ekosystemtjänster som utgör förutsättningen för en uthållig jordbruksproduktion och är till nytta för samhället i stort. Bakom dessa finns ekologiska processer som beror av samspel mellan en mångfald av organismer. Skånes jordbruk har genomgått betydande förändringar som förändrat landskapet och livsmiljön för många av dessa. För att bevara och förvalta ekosystemtjänsterna krävs en förståelse för sambanden mellan jordbruk, landskap och ekosystemprocesser. Rapporten beskriver ekologiska processer som ligger till grund för några viktiga ekosystemtjänster i Skånes jordbrukslandskap och visar betydelsen av biologisk mångfald för deras funktion. Där så är möjligt beskrivs hur de kan värderas. Slutligen redovisas praktiska åtgärder som gynnar dem. Rapporten visar att ekosystemtjänster inte enkelt går att ersätta med teknologiska lösningar, utan att förvaltning av dessa tjänster lönar sig. Detta kräver ökad ekologisk kunskap och anpassade styrmedel vilket kräver ökat samråd och regelbunden återkoppling mellan lantbrukare, myndigheter och forskare. Förhoppningen är att rapporten, framtagen av Lunds universitet och Region Skåne, inspirerar till detta!
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43. |
- Effiom, Edu, et al.
(författare)
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Changes of community composition at multiple trophic levels due to hunting in Nigerian tropical forest
- 2014
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Ingår i: Ecography. - : Wiley. - 1600-0587 .- 0906-7590. ; 37, s. 367-377
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Tidskriftsartikel (refereegranskat)abstract
- Hunting in tropical forests decimates large mammals, and this may have direct and indirect effects on other trophic levels and lead to trophic cascades. We compared replicated sites of hunted and protected forests in southeastern Nigeria, with respect to community composition of primates, other mammals, birds, plant seedlings, and mature trees. We make predictions regarding the community composition at the different trophic levels. In forests where large primates are rare, we hypothesize that their ecological role will not be fully compensated for by small frugivores. We apply multivariate methods to assess changes in community composition of mammals, birds, and seedlings, controlling for any differences between sites in the other groups, including mature trees. Medium and large (4–180 kg) primates were much rarer in hunted sites, while porcupine and rock hyrax increased in abundance with hunting. In contrast, the community composition of birds was similar in both types of forests. Seedling communities were significantly related to the community composition of mammals, and thus strongly affected by hunting. In protected forests primate dispersed plant seedling species dominated, whereas in hunted forests the seedling community was shifted towards one dominated by abiotically dispersed species. This was probably both a consequence of reduced seed dispersal by primates, and increased seed predation by rodents and hyrax. Hence we found no evidence for buffering effects on tree regeneration through functional compensation by non-hunted animals (such as birds). Our results highlight how seedling communities are changed by the complex plant–animal intera ctions, triggered by the loss of seed dispersers. The results predict a rarity of primate-dispersed trees in future tropical forest canopies; a forest less diverse in timber and non-timber resources.
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44. |
- Ekroos, Johan, et al.
(författare)
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Sparing land for biodiversity at multiple spatial scales
- 2016
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Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- A common approach to the conservation of farmland biodiversity and the promotion of multifunctional landscapes, particularly in landscapes containing only small remnants of non-crop habitats, has been to maintain landscape heterogeneity and reduce land-use intensity. In contrast, it has recently been shown that devoting specific areas of non-crop habitats to conservation, segregated from high-yielding farmland (“land sparing”), can more effectively conserve biodiversity than promoting low-yielding, less intensively managed farmland occupying larger areas (“land sharing”). In the present paper we suggest that the debate over the relative merits of land sparing or land sharing is partly blurred by the differing spatial scales at which it is suggested that land sparing should be applied. We argue that there is no single correct spatial scale for segregating biodiversity protection and commodity production in multifunctional landscapes. Instead we propose an alternative conceptual construct, which we call “multiple-scale land sparing,” targeting biodiversity and ecosystem services in transformed landscapes. We discuss how multiple-scale land sparing may overcome the apparent dichotomy between land sharing and land sparing and help to find acceptable compromises that conserve biodiversity and landscape multifunctionality.
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45. |
- Feng, Lanya, et al.
(författare)
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Fallows and permanent grasslands conserve the species composition and functional diversity of carabid beetles and linyphiid spiders in agricultural landscapes
- 2021
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Ingår i: Insect Conservation and Diversity. - : Wiley. - 1752-458X .- 1752-4598. ; 14:6, s. 825-836
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Tidskriftsartikel (refereegranskat)abstract
- The European Union reformed the Common Agricultural Policy (CAP 2013) to include greening measures with the aim to decrease negative impacts of farming on the environment and biodiversity. The degree to which greening measures such as permanent grassland or fallows of different ages enhance biodiversity is still debated. We investigate the effect of fallows in two different age classes and permanent grassland in the surrounding landscape on the taxonomic and functional diversity of two numerically dominant groups of natural enemies in cereal fields: soil-emerging carabid beetles (Family Carabidae, Order Coleoptera) and ground-active linyphiid spiders (Family Linyphiidae, Order Araneae). The species richness, abundance and Hill–Shannon diversity of carabids and linyphiids did not differ significantly between fallows and cereal fields and was not significantly related to the proportion of permanent grassland in the surrounding landscape. The species composition of both communities differed significantly between cereal fields and fallows. The functional distinctness, as an index reflecting the similarity among species in terms of functional traits, of linyphiids was significantly higher in fallows than in cereal fields. The trait composition of carabids was significantly related to the proportion of permanent grassland depending on field type (cereal or fallow). Our results document considerable species turnover in natural enemy communities of adjacent cereal fields and fallows, and support the assumption that older fallows (>8 years) produce functionally more diverse natural enemy communities. Maintaining fallows for a long period is an important measure to promote the functional diversity in predaceous arthropod communities.
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46. |
- Hanson, Helena, et al.
(författare)
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Agricultural Land Use Determines the Trait Composition of Ground Beetle Communities.
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- In order to improve biological control of agricultural pests, it is fundamental to understand which factors influence the composition of natural enemies in agricultural landscapes. In this study, we aimed to understand how agricultural land use affects a number of different traits in ground beetle communities to better predict potential consequences of land-use change for ecosystem functioning. We studied ground beetles in fields with different agricultural land use ranging from frequently managed sugar beet fields, winter wheat fields to less intensively managed grasslands. The ground beetles were collected in emergence tents that catch individuals overwintering locally in different life stages and with pitfall traps that catch individuals that could have a local origin or may have dispersed into the field. Community weighted mean values for ground beetle traits such as body size, flight ability and feeding preference were estimated for each land-use type and sampling method. In fields with high land-use intensity the average body length of emerging ground beetle communities was lower than in the grasslands while the average body length of actively moving communities did not differ between the land-use types. The proportion of ground beetles with good flight ability or a carnivorous diet was higher in the crop fields as compared to the grasslands. Our study highlights that increasing management intensity reduces the average body size of emerging ground beetles and the proportion of mixed feeders. Our results also suggest that the dispersal ability of ground beetles enables them to compensate for local management intensities.
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47. |
- Hanson, Helena I., et al.
(författare)
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Agricultural land use affects abundance and dispersal tendency of predatory arthropods
- 2017
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791. ; 18, s. 40-49
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Tidskriftsartikel (refereegranskat)abstract
- Predatory arthropods contribute to biological control, but to become an integral part of agricultural management, it is essential to identify drivers of their spatio-temporal distribution at the landscape scale. This study focuses on how agricultural land use affects the community composition, emergence and dispersal tendency of predatory arthropods. The arthropods were collected in emergence traps during the growing season (14 weeks) in a gradient of agricultural land uses from intensively managed sugar beet fields, over winter wheat fields, to less intensively managed grasslands. The emergence traps were equipped with one pitfall trap and a collecting bottle at the top. The distribution of the arthropods between these two collecting methods was assumed to represent their tendency to move out of the habitat. The grasslands had the highest numbers of spiders, while the winter wheat fields had the highest numbers of omnivorous rove beetles and macropterous predaceous ground beetles. The phenology of emergence differed between the land-use types, resulting in seasonal differences in community composition. The overall dispersal tendency of predatory arthropods was higher in crop fields than in grasslands. This study suggests that only a diverse mix of agricultural land uses will provide high levels of predators from different functional groups, throughout the growing season.
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48. |
- Haslund, Knut Per, et al.
(författare)
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Bra vallersättning och kompensationsstöd? : Hur kan olika utformningar påverka jordbruket, miljön, och samhällsekonomin?
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Positiva och negativa miljöeffekterVallersättningen och kompensationsstödet leder båda till att arealen vall och antalet nötkreatur ökar kraftigt. Utredningen konstaterar att effekten av vallodling på biologisk mångfald, både när det gäller sällsynta arter och ekosystemtjänster, är otillräckligt känd. Kompensationsstödet gör det företagsekonomiskt lönsamt att hävda betydligt större areal permanent betesmark, men vallersättningen leder däremot till något lägre betesareal.Det svenska jordbrukets kväve- och fosforläckage har varit lägre under de bådaanalyserade programperioderna tack vare vallersättningen. Under perioden 2015–20 är kväveläckaget är lägre än vad det skulle ha varit utan stödet också i slättbygderna, till skillnad från i landsbygdsprogrammets föregåendeperiod 2007–14. Kompensationsstödet medför tvärtom att växtnäringsläckagetär högre än vad det skulle vara om stödet inte fanns. Användningen av växtskyddsmedel i jordbruket påverkas inte mycket av dessa stöd under perioden 2015–20. Kompensationsstödet har under båda perioderna medfört stora utsläpp av växthusgaser. Vallersättningen är däremot bra ur klimatsynpunkt, om än inte lika starkt under perioden 2015–20 som under den föregående perioden. Stödens klimatpåverkan sker huvudsakligen genom att påverka mängden kol bundet i marken och antalet nötkreatur som avger växthusgasen metan, medan deras inverkan på jordbrukets användning av fossilbränsle till traktorer och annat är liten i sammanhanget. Kompensationsstödet är samhällsekonomiskt olönsamtVallersättningen medförde stora samhällsekonomiska förluster i början av perioden 2007–10, men efter ändrade stödregler och med högre världsmarknadspriser blev den i stället mycket lönsam. Även under innevarande programperiod 2015–20 har den en viss samhällsekonomisk lönsamhet. Kompensationsstödet ger dock stora samhällsekonomiska förluster, både under perioden 2007–14 och 2015–20. Samhällsekonomiskt sett vore det bra att halvera båda stöden. Kompensationsstödet ger många extra arbetstillfällen i områden med sämre förutsättningar för odling men till hög samhällsekonomisk kostnad. En del av kostnaden är att kompensationsstödet sammanvägt medför ökad miljöbelastning. Per budgetkrona var dock kostnaden relativt låg jämfört med andra arbetsmarknadspolitiska åtgärder. Störst betydelse för stödens samhällsekonomiska lönsamhet är deras klimateffekter, att deras skattefinansiering ger förluster i annan verksamhet, och att de leder till mindre effektiv jordbruksproduktion av marknadsvaror. Effekterna av stöden beror mycket på de ekonomiska förutsättningarna i övrigt, till exempel prisnivån för jordbruksprodukter på världsmarknaden. Utfallet kan bli ett annat än väntat om förutsättningarna ändras under perioden. Detta hände under perioden 2007–2014.
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49. |
- Haubert, Dominique, et al.
(författare)
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Trophic structure and major trophic links in conventional vs organic farming systems as indicated by carbon stable isotope ratios of fatty acids
- 2009
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Ingår i: Oikos. - : Wiley. - 1600-0706 .- 0030-1299. ; 118:10, s. 1579-1589
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Tidskriftsartikel (refereegranskat)abstract
- Using bulk tissue and fatty acid 13C analysis we investigated major trophic pathways from soil microorganisms to microbial consumers to predators in conventional versus organic farming systems planted for the first time with maize. Organic farming led to an increase in microbial biomass in particular that of fungi as indicated by phospholipid fatty acids (PLFAs). Microbial PLFAs reflected the conversion from C3 to C4 plants by a shift in δ13C of 2‰, whereas the isotopic signal in fatty acids (FAs) of Collembola was much more pronounced. In the euedaphic Protaphorura fimata the δ13C values in maize fields exceeded that in C3 (soybean) fields by up to 10‰, indicating a close relationship between diet and vegetation cover. In the epedaphic Orchesella villosaδ13C values shifted by 4‰, suggesting a wider food spectrum including carbon of former C3 crop residues. Differences in δ13C of corresponding FAs in consumers and resources were assessed to assign food web links. P. fimata was suggested as root and fungal feeder in soybean fields, fungal feeder in conventional and leaf consumer in organically managed maize fields. O. villosa likely fed on root and bacteria under soybean, and bacteria and fungi under maize. Comparison of δ13C values in FAs of the cursorial spider Pardosaagrestis and O. villosa implied the latter as important prey species in soybean fields. In contrast, the web-building spider Mangora acalypha showed no predator–prey relationship with Collembola. The determination of δ13C values in trophic biomarker FAs allowed detailed insight into the structure of the decomposer food web and identified diet-shifts in both consumers at the base of the food web and in top predators in organic versus conventional agricultural systems. The results indicate changes in major trophic links and therefore carbon flux through the food web by conversion of conventional into organic farming systems.
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50. |
- Hauffe, T., et al.
(författare)
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Spatially explicit analyses of gastropod biodiversity in ancient Lake Ohrid
- 2010
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Ingår i: Biogeosciences Discussions. - : Copernicus GmbH. - 1810-6277. ; 7:4, s. 4953-4985
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Tidskriftsartikel (refereegranskat)abstract
- Abstract. Spatial heterogeneity of biodiversity arises from evolutionary processes, constraints of environmental factors and the interaction of communities. The quality of such spatial analyses of biodiversity is improved by (i) utilizing study areas with well defined physiogeographical boundaries, (ii) limiting the impact of widespread species, and (iii) using taxa with heterogeneous distributions. These conditions are typically met by ecosystems such as oceanic islands or ancient lakes and their biota. While research on ancient lakes has contributed significantly to our understanding of evolutionary processes, statistically sound studies of spatial variation of extant biodiversity have been hampered by the frequently vast size of ancient lakes, their limited accessibility, and the lack of infrastructure around them. The small European ancient Lake Ohrid provides a rare opportunity for such a reliable spatial study. The comprehensive horizontal and vertical sampling of a species-rich taxon, the Gastropoda, presented here, revealed interesting patterns of biodiversity, which, in part, have not been shown before for other ancient lakes. In a total of 224 locations throughout the Ohrid Basin, representatives of 68 gastropod species with 50 of them being endemic (=73.5%) could be reported. The spatial distribution of these species shows the following characteristics: (i) within Lake Ohrid, the most frequent species are endemic taxa with a wide depth range, (ii) widespread species (i.e. those occurring throughout the Balkans or beyond) are rare and mainly occur in the upper layer of the lake, (iii) while the total number of species decreases with water depth, the share of endemics increases, (iv) the deeper layers of Lake Ohrid appear to have a higher spatial homogeneity of biodiversity and related environmental factors, (v) biotic interaction due to possible spillover effects may contribute to the establishment of hotspots, and (vi) eco-insularity within the Ohrid Basin occurs at two levels, at the level of the lake proper and at the level of the feeder-springs. It is also shown that large scale effects such as type of water body or water depth are mainly responsible for the distribution of biodiversity. In addition, small scale effects like environmental gradients or biotic interaction affect gastropod composition within a particular depth zone.
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