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Träfflista för sökning "WFRF:(Fahrig Lenore) "

Search: WFRF:(Fahrig Lenore)

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1.
  • Alignier, Audrey, et al. (author)
  • Configurational crop heterogeneity increases within-field plant diversity
  • 2020
  • In: Journal of Applied Ecology. - : Wiley. - 0021-8901 .- 1365-2664. ; 57:4, s. 654-663
  • Journal article (peer-reviewed)abstract
    • Increasing landscape heterogeneity by restoring semi-natural elements to reverse farmland biodiversity declines is not always economically feasible or acceptable to farmers due to competition for land. We hypothesized that increasing the heterogeneity of the crop mosaic itself, hereafter referred to as crop heterogeneity, can have beneficial effects on within-field plant diversity. Using a unique multi-country dataset from a cross-continent collaborative project covering 1,451 agricultural fields within 432 landscapes in Europe and Canada, we assessed the relative effects of compositional and configurational crop heterogeneity on within-field plant diversity components. We also examined how these relationships were modulated by the position within the field. We found strong positive effects of configurational crop heterogeneity on within-field plant alpha and gamma diversity in field interiors. These effects were as high as the effect of semi-natural cover. In field borders, effects of crop heterogeneity were limited to alpha diversity. We suggest that a heterogeneous crop mosaic may overcome the high negative impact of management practices on plant diversity in field interiors, whereas in field borders, where plant diversity is already high, landscape effects are more limited. Synthesis and applications. Our study shows that increasing configurational crop heterogeneity is beneficial to within-field plant diversity. It opens up a new effective and complementary way to promote farmland biodiversity without taking land out of agricultural production. We therefore recommend adopting manipulation of crop heterogeneity as a specific, effective management option in future policy measures, perhaps adding to agri-environment schemes, to contribute to the conservation of farmland plant diversity.
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2.
  • Hass, Annika L., et al. (author)
  • Landscape configurational heterogeneity by small-scale agriculture, not crop diversity, maintains pollinators and plant reproduction in western Europe
  • 2018
  • In: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 285:1872
  • Journal article (peer-reviewed)abstract
    • Agricultural intensification is one of the main causes for the current biodiversity crisis. While reversing habitat loss on agricultural land is challenging, increasing the farmland configurational heterogeneity (higher field border density) and farmland compositional heterogeneity (higher crop diversity) has been proposed to counteract some habitat loss. Here, we tested whether increased farmland configurational and compositional heterogeneity promote wild pollinators and plant reproduction in 229 landscapes located in four major western European agricultural regions. High-field border density consistently increased wild bee abundance and seed set of radish (Raphanus sativus), probably through enhanced connectivity. In particular, we demonstrate the importance of crop-crop borders for pollinator movement as an additional experiment showed higher transfer of a pollen analogue along crop-crop borders than across fields or along semi-natural crop borders. By contrast, high crop diversity reduced bee abundance, probably due to an increase of crop types with particularly intensive management. This highlights the importance of crop identity when higher crop diversity is promoted. Our results show that small-scale agricultural systems can boost pollinators and plant reproduction. Agri-environmental policies should therefore aim to halt and reverse the current trend of increasing field sizes and to reduce the amount of crop types with particularly intensive management.
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3.
  • Ranius, Thomas, et al. (author)
  • A comparison of patch connectivity measures using data on invertebrates in hollow oaks
  • 2010
  • In: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 33, s. 971-978
  • Journal article (peer-reviewed)abstract
    • This study aimed at comparing six patch connectivity measures by fitting them to field data. We used occupancy data for eight beetle and two pseudoscorpion species from 281 hollow oaks in southeast Sweden. Species occupancy was modelled in relation to tree characteristics and one measure of patch connectivity at a time. For each connectivity measure we searched for the spatial scale that generated the best fit to field data. Connectivity measures that only include occupied patches provided better model fits than those that include all patches. When occupancy data are absent for surrounding habitat patches, information that reflects occurrence probabilities can be included in the connectivity measure. However, in this study incorporation of such information resulted in only a slight improvement of model fit. A frequently used connectivity measure based on the negative exponential function was relatively poor in explaining species' occurrence; for eight species out of nine a buffer measure was better. A better fit was obtained when the negative exponential function was modified to take into account that habitat patches may "compete'' for the immigrants. The spatial scale with the best fit tended to be larger when we used connectivity measures in which dispersal sources are identified with lower precision. Thus, the outcomes from different multiple-scale studies are not directly comparable if the density of dispersal sources is not measured in the same way. Overall we conclude that buffer measures are useful, as they give good predictions and are easy to understand and use. If a biologically more realistic measure is needed, one that up-weights the closest patches should be used. Finally, the possibility that habitat patches may compete with each other for immigrants should be considered when selecting a connectivity measure.
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4.
  • Ranius, Thomas, et al. (author)
  • Predicting spatial occurrence of beetles and pseudoscorpions in hollow oaks in southeastern Sweden
  • 2011
  • In: Biodiversity and Conservation. - : Springer Science and Business Media LLC. - 0960-3115 .- 1572-9710. ; 20, s. 2027-2040
  • Journal article (peer-reviewed)abstract
    • We modelled presence/absence per tree of beetles and pseudoscorpions living in tree hollows in relation to trunk circumference, habitat openness, and connectivity (= density of hollow oaks in the surrounding area), using data from 281 oaks. The presence/absence models were then used to predict species' occurrences in a county (11,600 km(2)) in southeastern Sweden. For eight of the nine species, the most parsimonious occupancy model included a positive relationship with connectivity and at least one tree characteristic. Occupancy underestimates from occurrence records-the ratio of the area of occupancy based on our predictive model to the area of occupancy based on occurrence records-varied between 3 and 83 among species when using occurrence records up to 1993, with significantly larger underestimates for smaller beetle species. Today (after extensive surveys), underestimation has decreased to 1.3-25, confirming that calculations solely based on species occurrence records greatly underestimate the area of occupancy. We suggest this should be taken into account to a greater extent and in a clearer way than today when constructing red lists. The radius of the connectivity measure that generated the best fit varied between 135 and 2,857 m among species, with longer distances for more threatened species. Consequently, preservation of the most threatened species (Elater ferrugineus and Tenebrio opacus) requires conservation efforts at larger spatial scales than required to protect Osmoderma eremita, which frequently has been used as an indicator and umbrella species.
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5.
  • Sirami, Clélia, et al. (author)
  • Increasing crop heterogeneity enhances multitrophic diversity across agricultural regions
  • 2019
  • In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 116:33, s. 16442-16447
  • Journal article (peer-reviewed)abstract
    • Agricultural landscape homogenization has detrimental effects on biodiversity and key ecosystem services. Increasing agricultural landscape heterogeneity by increasing seminatural cover can help to mitigate biodiversity loss. However, the amount of seminatural cover is generally low and difficult to increase in many intensively managed agricultural landscapes. We hypothesized that increasing the heterogeneity of the crop mosaic itself (hereafter “crop heterogeneity”) can also have positive effects on biodiversity. In 8 contrasting regions of Europe and North America, we selected 435 landscapes along independent gradients of crop diversity and mean field size. Within each landscape, we selected 3 sampling sites in 1, 2, or 3 crop types. We sampled 7 taxa (plants, bees, butterflies, hoverflies, carabids, spiders, and birds) and calculated a synthetic index of multitrophic diversity at the landscape level. Increasing crop heterogeneity was more beneficial for multitrophic diversity than increasing seminatural cover. For instance, the effect of decreasing mean field size from 5 to 2.8 ha was as strong as the effect of increasing seminatural cover from 0.5 to 11%. Decreasing mean field size benefited multitrophic diversity even in the absence of seminatural vegetation between fields. Increasing the number of crop types sampled had a positive effect on landscape-level multitrophic diversity. However, the effect of increasing crop diversity in the landscape surrounding fields sampled depended on the amount of seminatural cover. Our study provides large-scale, multitrophic, cross-regional evidence that increasing crop heterogeneity can be an effective way to increase biodiversity in agricultural landscapes without taking land out of agricultural production.
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