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Sökning: WFRF:(Jonason Dennis)

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1.
  • Bergman, Karl-Olof, et al. (författare)
  • Clear-cuts are temporary habitats, not matrix, for endangered grassland burnet moths (Zygaena spp.)
  • 2020
  • Ingår i: Journal of Insect Conservation. - : Springer Science and Business Media LLC. - 1366-638X .- 1572-9753. ; 24:2, s. 269-277
  • Tidskriftsartikel (refereegranskat)abstract
    • Burnet moths (Zygaena spp.) are day-flying Lepidoptera considered indicative of species-rich grasslands. In the present study, our aim was to clarify whether clear-cuts are habitat, supporting habitat or matrix for three species of Zygaena. We did so by sampling these species with sex pheromones on 48 clear-cuts, varying in amount of host and nectar plants, in southern Sweden. To compare the efficiency of such sampling, we also conducted transect walks on these clearcuts. Overall, host-plants on clear-cuts best explained the abundance of Zygaena spp. recorded, better than nectar-plants or connectivity with nearby grasslands. These results indicate that clear-cuts with an abundance of host plants are used as a fully functional habitat, and not a supporting habitat in the sense of only providing nectar. There is no support in these results for considering clear-cuts as an inert matrix. With about half the work-effort, pheromone traps recorded 100 times more Zygaena spp. as transect walks. The poor correspondence between observations during transects walks and pheromone trap catches suggest Zygaena spp. being difficult to monitor by transect walks. In contrast to grasslands, clear-cuts are short-term in nature requiring repeated recolonization, indicating the importance of permanent grasslands. However, clear-cuts are important temporary insect habitats due to their great acreage, and suitable management can increase the time they remain a habitat.
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2.
  • Blixt, Torbjörn, et al. (författare)
  • Clear-cuts in production forests: From matrix to neo-habitat forbutterflies
  • 2015
  • Ingår i: Acta Oecologica. - : Elsevier. - 1146-609X .- 1873-6238. ; 69, s. 71-77
  • Tidskriftsartikel (refereegranskat)abstract
    • Butterfly conservation in Europe is mainly focused on well-defined grassland habitat patches. Such anapproach ignores the impact of the surrounding landscape, which may contain complementary resourcesand facilitate dispersal. Here, we investigated butterfly species richness and abundance in a habitatnormally regarded as unsuitable matrix: production forestry clear-cuts. Butterflies were recorded in 48clear-cuts in southern Sweden differing with regards to the time since clear-cutting and land-use history(meadow or forest based on historical maps from the 1870s). All clear-cuts had been managed as productionforests for at least 80e120 years. A total of 39 species were found in clear-cuts of both land-usehistories, but clear-cuts with a history as meadow had on average 34% higher species richness and 19%higher abundance than did clear-cuts with a history as forest. No effect of the time since clear-cuttingwas found, irrespective of land-use history, which was likely due to the narrow timespan sampled (<8years). The absence of temporal effect suggests that clear-cuts may provide butterflies with valuableresources for 10e15 years. Assuming a 100 year forest rotational cycle, this means that 10e15% of thetotal forested area are made up by clear-cuts valuable to butterflies, which corresponds to an area aboutfour times as large as that of species-rich semi-natural grasslands. The study illustrates the importance ofconsidering land-use legacies in ecological research and question the landscape-ecological view thatclear-cuts make up an unsuitable matrix for butterflies. Moreover, forest conservation management withspecial attention to land-use history may increase the quality of the landscape, thus facilitating butterflymetapopulation persistence. Given their large area and assets of nectar and host plant resources, clearcutsmust be considered as a butterfly habitat in its own right. Being a man-made environment withshort history, we might call it a neo-habitat.
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3.
  • Jonason, Dennis, et al. (författare)
  • Assessing the effect of the time since transition to organic farming on plants and butterflies
  • 2011
  • Ingår i: Journal of Applied Ecology. - : Wiley. - 1365-2664 .- 0021-8901. ; 48:3, s. 543-550
  • Tidskriftsartikel (refereegranskat)abstract
    • P>1. Environmental changes may not always result in rapid changes in species distributions, abundances or diversity. In order to estimate the effects of, for example, land-use changes caused by agri-environment schemes (AES) on biodiversity and ecosystem services, information on the time-lag between the application of the scheme and the responses of organisms is essential. 2. We examined the effects of time since transition (TST) to organic farming on plant species richness and butterfly species richness and abundance. Surveys were conducted in cereal fields and adjacent field margins on 60 farms, 20 conventional and 40 organic, in two regions in Sweden. The organic farms were transferred from conventional management between 1 and 25 years before the survey took place. The farms were selected along a gradient of landscape complexity, indicated by the proportion of arable land, so that farms with similar TST were represented in all landscape types. Organism responses were assessed using model averaging. 3. Plant and butterfly species richness was c. 20% higher on organic farms and butterfly abundance was about 60% higher, compared with conventional farms. Time since transition affected butterfly abundance gradually over the 25-year period, resulting in a 100% increase. In contrast, no TST effect on plant or butterfly species richness was found, indicating that the main effect took place immediately after the transition to organic farming. 4. Increasing landscape complexity had a positive effect on butterfly species richness, but not on butterfly abundance or plant species richness. There was no indication that the speed of response to organic farming was affected by landscape complexity. 5. Synthesis and applications. The effect of organic farming on diversity was rapid for plant and butterfly species richness, whereas butterfly abundance increased gradually with time since transition. If time-lags in responses to AESs turn out to be common, long-term effects would need to be included in management recommendations and policy to capture the full potential of such schemes.
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4.
  • Jonason, Dennis, et al. (författare)
  • Field scale organic farming does not counteract landscape effects on butterfly trait composition
  • 2012
  • Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier BV. - 1873-2305 .- 0167-8809. ; 158, s. 66-71
  • Tidskriftsartikel (refereegranskat)abstract
    • We tested how dispersal capacity, host plant specificity and reproductive rate influenced the effects of farming system and landscape composition on butterfly species richness and abundance. In no case did variation in these traits explain species responses to organic farming, indicating that all species benefit equally. In contrast, butterflies with high mobility and reproductive rate were disproportionally more abundant in landscapes dominated by arable land, and the species richness of butterflies with low mobility tended to decrease with increasing proportion of arable land whereas those of high mobility remained fairly constant. Hence, although organic farming increased biodiversity, it did not counteract landscape effects on butterfly trait composition. As a trait dependent loss of biodiversity may result in a larger decline of functional trait diversity compared to species diversity, these results imply that organic farming may not increase or restore functional agro-ecosystem diversity. Information provided by species traits, rather than biodiversity per se, may provide important information for successful revisions of future agri-environment schemes.
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5.
  • Jonason, Dennis, et al. (författare)
  • Land-use history exerts long-term effects on the clear-cut flora in boreonemoral Sweden
  • 2016
  • Ingår i: Applied Vegetation Science. - : WILEY-BLACKWELL. - 1402-2001 .- 1654-109X. ; 19:4, s. 634-643
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionsCan signs of 19th century grassland management, which can be observed in the flora immediately (2-4yrs) after clear-cutting in boreonemoral Sweden, still remain 4yrs later? Do the effects from the time since clear-cutting differ between forest and grassland plant species? LocationProvince of ostergotland, southern Sweden. MethodsTwelve contemporary clear-cut areas that were once meadows and 12 that were once forests were selected using land-use maps from the 1870s. Grasses and herbaceous plants were surveyed twice, once in 2009 and once in 2013 (2-4 and 6-8yrs after clear-cutting, respectively). Plant presence was recorded within 100 circular sample plots (radius 1m) placed evenly throughout each respective clear-cut area along transects spaced 25-m apart. The number of sample plots in which a species was present was taken as a measure of that species frequency. Random effects meta-analysis, odds ratios and ANCOVA were used to analyse species responses to clear-cutting over time. ResultsA total of 170 plant species were found in the study, of which 33 were classified as grassland indicator species and 31 as plants primarily confined to forests. Clear-cut areas with a history as meadowland had, on average, up to 64% higher total species richness and 110% more grassland indicator species than did clear-cut areas with a history as forest. The time since clear-cutting had no effect on total species richness. However, the odds of finding a grassland indicator species decreased with the time since clear-cutting, whereas the odds of finding a forest species increased. ConclusionsWe concluded that land-use history plays an important role in explaining the flora found in Swedish clear-cuts, and that its effects on species richness remain for a minimum of 8yrs after harvest (conservative estimate). This phenomenon highlights the importance of acknowledging land-use legacies in ecological research and conservation. Future studies should investigate various options for the promotion of grassland plants in clear-cuts with a history of grassland management while also acknowledging the potential conflicts between conservation and production. The results may pertain to other countries with similar land-use histories.
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6.
  • Jonason, Dennis, et al. (författare)
  • Landscape simplification promotes weed seed predation by carabid beetles (Coleoptera: Carabidae)
  • 2013
  • Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 1572-9761 .- 0921-2973. ; 28:3, s. 487-494
  • Tidskriftsartikel (refereegranskat)abstract
    • Weeds constitute major constraints for farmers by reducing crop yield and quality. However, weeds are managed effectively using herbicides, but this may cause harmful effects on human health and the environment. In an experiment on weed seed predation, we tested the biological control potential of carabid beetles to combat weeds in the absence of herbicides. Seeds from three common weed species were placed in cereal fields on conventional and organic farms located along a landscape complexity gradient (area annual crops within 1 km) in two distinct regions in Sweden. Carabid beetles were sampled in the same fields using pitfall traps. Neither carabid species richness nor seed removal was related to organic farming. Seed removal was significantly related to carabid species richness and both carabid species richness and seed removal was higher in landscapes with large total area of annual crops, although the evenness of the carabid communities was lower. The carabid genera with strongest positive relationship to seed removal differed between regions (Trechus in Uppland and Pterostichus in Scania), as did the preference for the different weed seed species. This study concludes that carabid species richness contributes to weed seed predation and that large scale landscape context explains more variation in the carabids' responses than local farming practices.
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7.
  • Jonason, Dennis (författare)
  • Monitoring of butterflies within a landscape context
  • 2007
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Monitoring of butterflies is most often only directed towards the grassland fauna. Species associated with other vegetation types, as well as the impact of the surrounding landscape, often become neglected. The aim with this study was, in contrast, to perform a novel landscape-based monitoring method for butterflies in diverse vegetation types and more specifically(i) evaluate the impact of environmental variables on butterfly abundance, (ii) compare the distribution of butterflies in different vegetation types and (iii) analyse and improve the monitoring method. Eight randomly placed study sites (750 m x 750 m) located in south eastern Sweden were used. The vegetation composition inside the squares had been assessed using aerial photos. Tree cover had largest impact on butterfly abundance with a negative linear relationship between abundance and increasing tree cover. Clear-cuts were the vegetation type harbouring the overall highest abundance and diversity of butterflies. In semi-natural grasslands, where the nationally-based monitoring of butterflies in Sweden currently is being performed, only 42% of the species were found, indicating a bias directed towards only a part of the species pool. The novel kind of monitoring presented here, using a landscape context, can, if performed regularly, increase our knowledge of how structural changes at landscape level affect butterflies and thereby improve the conservation efforts. 
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8.
  • Jonason, Dennis, et al. (författare)
  • Monitoring of butterflies within a landscape context in south-eastern Sweden
  • 2010
  • Ingår i: JOURNAL FOR NATURE CONSERVATION. - : Elsevier Science B.V., Amsterdam. - 1617-1381. ; 18:1, s. 22-33
  • Tidskriftsartikel (refereegranskat)abstract
    • Monitoring of butterflies is often directed only towards grassland fauna. Species associated with other habitats, as well as the impact of the surrounding landscape, are often neglected. The aim with this study was, in contrast, to perform and evaluate a landscape-based monitoring method for butterflies in diverse habitats and more specifically to (i) evaluate the impact of environmental variables on butterfly abundance; (ii) compare the distribution of butterflies in different habitats; and (iii) analyse data from the study with the aim of improving the method. Eight randomly placed study sites (750 m x 750 m) located in south-eastern Sweden were used. The vegetation composition (tree cover, percentage of coniferous and deciduous forest, shrubs, dry, mesic, damp and wet land) inside the squares was analysed using aerial photos and habitats along transects were categorised in the field. The butterfly composition varied depending on the landscape composition. Tree cover had the largest impact on butterfly abundance with a negative relationship between abundance and increasing tree cover. The most species-rich habitats were other grasslands (abandoned fields and fallows), clear-cuts, semi-natural grasslands, and bogs, each habitat also harbouring unique species. Clear-cut was the habitat harbouring the highest abundance and other grasslands the highest diversity of butterflies. Semi-natural grasslands, where the nationally based monitoring of butterflies in Sweden currently is being performed, constitutes andlt;1% of the total land area in Sweden, indicating a current bias in monitoring directed towards only a part of the species pool. The landscape-based form of monitoring presented here can, if performed regularly, increase our knowledge of how structural changes of landscape affect butterflies and thereby improve conservation efforts.
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9.
  • Jonason, Dennis, et al. (författare)
  • Surveying Moths Using Light Traps: Effects of Weather and Time of Year
  • 2014
  • Ingår i: PLOS ONE. - : Public Library of Science. - 1932-6203. ; 9:3, s. 0092453-
  • Tidskriftsartikel (refereegranskat)abstract
    • Light trapping is an ideal method for surveying nocturnal moths, but in the absence of standardised survey methods effects of confounding factors may impede interpretation of the acquired data. We explored the influence of weather, time of year, and light source on nightly catches of macro moths in light traps, and compared four strategies for sampling by estimating observed species richness using rarefaction. We operated two traps with different light sources for 225 consecutive nights from mid-March to the end of October in eastern Germany in 2011. In total, 49 472 individuals of 372 species were recorded. Species richness and abundance per night were mainly influenced by night temperature, humidity and lamp type. With a limited sample size (less than10 nights) it was slightly better to concentrate sampling on the warmest summer nights, but with more sampling nights it was slightly better to sample during the warmest nights in each month (March to October). By exploiting the higher moth activity during warm nights and an understanding of the species phenology, it is possible to increase the number of species caught and reduce effects of confounding abiotic factors.
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10.
  • Jonason, Dennis (författare)
  • Temporal effects of organic farming on biodiversity and ecosystem services
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Agricultural intensification has caused a dramatic decline of global biodiversity and associated ecosystem services. Organic farming has been shown to partially counteract agricultural intensification by applying environmentally friendly and resource efficient farming practices, but opportunities to improve in efficiency still remain. This thesis investigates the contribution of organic farming to biodiversity and ecosystem services with focus on the effect of the time since transition (TST) to organic farming methods. Surveys on butterflies, plants, moths, carabid beetles and an experimental study on weed seed predation were performed on conventional and organic farms situated in landscapes differing in landscape complexity. The organic farms had been under organic management between 1 and 25 years before surveys. This design allowed for analyzes of the effect of organic farming while accounting for the time since transition and landscape composition. The overall effect of organic farming was small. Only butterflies and plants (in one out of two studies) had higher species richness and abundance on organic compared to conventional farms. However, analyses of the time since transition to organic farming revealed novel facts: butterfly abundance increased gradually by 100% over 25 years, whereas butterfly and plant species richness increased rapidly at the transition and then remained fairly constant. The moths that initially did not appear to increase in the organic farming system showed a clear positive response to newly transitioned farms (TST≤6 years), whereas conventional and old organic farms (TST≥15 years) had similar diversity. Two plant species occurred more frequently on new organic farms and two species on old organic farms. Neither carabids nor seed predation showed any temporal responses to organic farming. This thesis shows that explicitly addressing temporal effects of organic farming may result in novel and unexpected findings. Control for temporal effects opens up for better understanding of the complexities between organic farming, biodiversity and ecosystem services over time. Future evaluations need to address this factor for high credibility and usefulness in the development of improved policies for organic farming.
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11.
  • Jonason, Dennis, et al. (författare)
  • Transient peak in moth diversity as a response to organic farming
  • 2013
  • Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1618-0089 .- 1439-1791. ; 14:6, s. 515-522
  • Tidskriftsartikel (refereegranskat)abstract
    • Few initiatives to preserve and enhance biodiversity on farmland have been as thoroughly evaluated and debated as the agri-environment schemes (AES). Yet, little is known how confounding factors co-varying with the specific AES measures may affect species responses. Here, we quantify the influence of one such factor, the time since transition to organic farming, on moth diversity patterns. We found that species richness and abundance of moths were higher on new organic farms (years since transition ≤6) compared to old organic (≥15 years) and conventional farms, indicating a transient diversity peak. This correlates with the abundance patterns of the weed Cirsium arvense, which also reached its highest densities on new organic farms. Weeds such as C. arvense constitute a notorious problem in organic farming. However, they also provide various resources for farmland biodiversity, and our results strongly suggest that the transient weed peak may be important in influencing the parallel peak among the moths. This stresses the problem in balancing out production and conservation values. More generally, our results show that rather than having static effects on the environment, AES can have an important temporal component and result in a dynamic interplay between different trophic levels.
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12.
  • Jonason, Dennis, et al. (författare)
  • Vegetation in clear-cuts depends on previous land use : a century-old grassland legacy
  • 2014
  • Ingår i: Ecology and Evolution. - : John Wiley & Sons. - 2045-7758. ; 4:22, s. 4287-4295
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant species richness in central and northern European seminatural grasslandsis often more closely linked to past than present habitat configuration, which isindicative of an extinction debt. In this study, we investigate whether signs ofhistorical grassland management can be found in clear-cuts after at least80 years as coniferous production forest by comparing floras between clear-cutswith a history as meadow and as forest in the 1870s in Sweden. Study sites wereselected using old land-use maps and data on present-day clear-cuts. Speciestraits reflecting high capacities for dispersal and persistence were used toexplain any possible links between the plants and the historical land use. Clearcutsthat were formerly meadow had, on average, 36% higher species richnessand 35% higher richness of grassland indicator species, as well as a larger overallseed mass and lower anemochory, compared to clear-cuts with history asforest. We suggest that the plants in former meadows never disappeared afterafforestation but survived as remnant populations. Many contemporary forestsin Sweden were managed as grasslands in the 1800s. As conservation of remaininggrassland fragments will not be enough to reduce the existing extinctiondebts of the flora, these young forests offer opportunities for grassland restorationat large scales. Our study supports the concept of remnant populationsand highlights the importance of considering historical land use for understandingthe distribution of grassland plant species in fragmented landscapes, aswell as for policy-making and conservation.
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13.
  • Jonason, Dennis, et al. (författare)
  • Weak functional response to agricultural landscape homogenisation among plants, butterflies and birds
  • 2017
  • Ingår i: Ecography. - : Wiley. - 0906-7590 .- 1600-0587. ; 40:10, s. 1221-1230
  • Tidskriftsartikel (refereegranskat)abstract
    • Measures of functional diversity are expected to predict community responses to land use and environmental change because, in contrast to taxonomic diversity, it is based on species traits rather than their identity. Here, we investigated the impact of landscape homogenisation on plants, butterflies and birds in terms of the proportion of arable field cover in southern Finland at local (0.25 km2) and regional (> 10 000 km2) scales using four functional diversity indices: functional richness, functional evenness, functional divergence and functional dispersion. No uniform response in functional diversity across taxa or scales was found. However, in all cases where we found a relationship between increasing arable field cover and any index of functional diversity, this relationship was negative. Butterfly functional richness decreased with increasing arable field cover, as did butterfly and bird functional evenness. For butterfly functional evenness, this was only evident in the most homogeneous regions. Butterfly and bird functional dispersion decreased in homogeneous regions regardless of the proportion of arable field cover locally. No effect of landscape heterogeneity on plant functional diversity was found at any spatial scale, but plant species richness decreased locally with increasing arable field cover. Overall, species richness responded more consistently to landscape homogenisation than did the functional diversity indices, with both positive and negative effects across species groups. Functional diversity indices are in theory valuable instruments for assessing effects of land use scenarios on ecosystem functioning. However, the applicability of empirical data requires deeper understanding of which traits reliably capture species' vulnerability to environmental factors and of the ecological interpretation of the functional diversity indices. Our study provides novel insights into how the functional diversity of communities changes in response to agriculturally derived landscape homogenisation; however, the low explanatory power of the functional diversity indices hampers the ability to reliably anticipate impacts on ecosystem functioning.
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14.
  • Lichtenberg, Elinor M., et al. (författare)
  • A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes
  • 2017
  • Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 23:11, s. 4946-4957
  • Tidskriftsartikel (refereegranskat)abstract
    • Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in-field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in-field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.
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15.
  • Milberg, Per, et al. (författare)
  • Flower abundance and vegetation height as predictors fornectar-feeding insect occurrence in Swedish semi-natural grasslands
  • 2016
  • Ingår i: Agriculture, Ecosystems & Environment. - : Elsevier. - 0167-8809 .- 1873-2305. ; 230, s. 47-54
  • Tidskriftsartikel (refereegranskat)abstract
    • With steadily shrinking areas of species-rich semi-natural grasslands in Europe, the management of theremaining fragments becomes ever more crucial for the preservation of key elements of biodiversity inthe agricultural landscape. Detailed knowledge about species-wise, as well as group-wise, relationshipscan provide guidelines for conservation management and a basis for predictions about differentmanagement scenarios. In the present study, we related the occurrence of species of bumblebees (N = 12),butterflies (31) and day-flying moths (4) and their total richness in 424 sites in southern Sweden to threegrass sward attributes, (i)flower abundance, (ii) height of the grass sward and (iii) within-site variation inheight of vegetation. The abundance of nectar-bearingflowers proved overall the best predictor ofrichness and in most of the occurrence-based species-wise models. However, both high grass swardheight and high variation in grass sward height contributed significantly to species richness andoccurrence of individual species. There was a tendency for bumblebees to respond less positively toflower abundance and vegetation height than butterflies and moths. One expectation was that grasslandspecialists, red-listed species, or species decreasing in other part of Europe, would be more responsive totall vegetation orflower abundance but there was no support for this in the data. Hence, managementstrategies that promote common species will also benefit all, or most of, the rare ones as well.
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16.
  • Milberg, Per, et al. (författare)
  • Land-use history influence the vegetation in coniferous production forests in southern Sweden
  • 2019
  • Ingår i: Forest Ecology and Management. - : ELSEVIER SCIENCE BV. - 0378-1127 .- 1872-7042. ; 440, s. 23-30
  • Tidskriftsartikel (refereegranskat)abstract
    • During the last centuries, land use in Europe intensified, which has led to a drastic decrease in the cover of semi-natural grasslands. In Sweden, much of the lost grasslands was turned into forest. This study investigated if species typical of managed grasslands could be found in coniferous production forests more than 80 years after grassland management ceased. Species and trait composition for plants was investigated in two types of forest differing in land use history (meadow in the 1870s or continuous coniferous forest), and in reference grasslands. The average plant species richness as well as the richness of grassland indicator species were 30% higher in forests with a history as meadow compared to in forests with a history as forest, hence clear signs of historical grassland management in todays forests. Compared with forests with continuous coniferous history, vegetation in forests with a meadow history tended to be more similar to reference grassland regarding both plant species and especially plant trait composition. The study provides proof of remnant grassland populations in coniferous production as the source for the biodiversity of clearcuts, rather than seed dispersal or seed bank survival. The result highlights the importance of land use for biodiversity of clearcuts, and points to the potential value of forests with a history of meadow in grassland conservation and restoration.
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17.
  • Ranius, Thomas, et al. (författare)
  • The evolutionary species pool concept does not explain occurrence patterns of dead-wood-dependent organisms: implications for logging residue extraction
  • 2019
  • Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 191, s. 241-252
  • Tidskriftsartikel (refereegranskat)abstract
    • Emulation of natural disturbances is often regarded as a key measure to make forestry biodiversity-oriented. Consequently, extraction of logging residues is assumed to have little negative effect in comparison to extraction of dead wood mainly formed at natural disturbances. This is consistent with the evolutionary species pool hypothesis, which suggests that most species are evolutionary adapted to the naturally most abundant habitats. We tested this hypothesis for dead-wood-dependent macrofungi, lichens, and beetles in a boreal forest landscape in central Sweden, assuming that species are adapted to conditions similar to today's unmanaged forest. No occurrence patterns, for the species groups which we investigated, were consistent with the hypothesis. Overall, stumps and snags had the highest habitat quality (measured as average population density with equal weight given to each species) and fine woody debris the lowest, which was unexpected, since stumps were the rarest dead-wood type in unmanaged forest. We conclude that the evolutionary species pool concept did not explain patterns of species' occurrences, and for two reasons, the concept is not reliable as a general rule of thumb: (1) what constitute habitats harbouring different species communities can only be understood from habitat-specific studies and (2) the suitability of habitats is affected by their biophysical characteristics. Thus, emulation of natural disturbances may promote biodiversity, but empirical studies are needed for each habitat to understand how natural disturbances should be emulated. We also conclude that stump extraction for bioenergy is associated with larger risks for biodiversity than fine woody debris extraction.
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18.
  • Westerberg, Lars, et al. (författare)
  • Color pan traps often catch less when there are more flowers around
  • 2021
  • Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 11:9, s. 3830-3840
  • Tidskriftsartikel (refereegranskat)abstract
    • When assessing changes in populations of species, it is essential that the methods used to collect data have some level of precision and preferably also good accuracy. One commonly used method to collect pollinators is colour pan traps, but this method has been suggested to be biased by the abundance of surrounding flowers. The present study evaluated the relationship between pan trap catches and the frequency of flowers on small (25 m(2)) and large (2-6 ha) spatial scales. If pan traps work well, one should assume a positive relationship, that is, more insects caught when they have more food. However, in contrast, we found that catches in pan traps were often negatively affected by flower frequency. Among the six taxa evaluated, the negative bias was largest in Vespoidea and Lepturinae, while there was no bias in solitary Apoidea (Cetoniidae, Syrphidae and social Apoidea were intermediate). Furthermore, red flowers seemed to contribute most to the negative bias. There was also a tendency that the negative bias differed within the flight season and that it was higher when considering the large spatial scale compared to the small one. To conclude, pan trap catches may suffer from a negative bias due to surrounding flower frequency and color. The occurrence and magnitude of the negative bias were context and taxon dependent, and therefore difficult to adjust for. Thus, pan traps seem less suited to evaluate differences between sites and the effect of restoration, when gradients in flower density are large. Instead, it seems better suited to monitor population changes within sites, and when gradients are small.
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19.
  • Westerberg, Lars, 1970-, et al. (författare)
  • Colour pan-traps often catch less when there are more flowers around
  • 2021
  • Annan publikationabstract
    • When assessing changes in populations of species it is essential that the methods used to collect data have some level of precision and preferably also good accuracy. One commonly used method to collect pollinators is colour pan-traps, but this method has been suggested to be biased by the abundance of surrounding flowers. The present study evaluated the relationship between pan-trap catches and the frequency of flowers on small (25 m2) and large (2-6 ha) spatial scales. If pan-traps work well, one should assume a positive relationship, i.e. more insects caught when they have more food. However, in contrast, we found that catches in pan-traps were often negatively affected by flower frequency. Among the six taxa evaluated, the negative bias was largest in Vespoidea and Lepturinae, while there was no bias in solitary Apoidea (Cetoniidae, Syrphidae and social Apoidea were intermediate). Furthermore, red flowers seemed to contribute most to the negative bias. There was also a tendency that the negative bias differed within the flight season and that is was higher when considering the large spatial scale compared to the small one. To conclude, pan-trap catches may suffer from a negative bias due to surrounding flower frequency and colour. The occurrence and magnitude of the negative bias was context and taxon dependent, and therefore difficult to adjust for. Thus, pan-traps seems less suited to evaluate differences between sites and the effect of restoration, when gradients in flower density is large. Instead, it seems better suited to monitor population changes within sites, and when gradients are small.Methods STUDY SITES: Data were collected in 2015 in the province of Östergötland, southern Sweden. The landscape in the study area consists mainly of coniferous forest, but there are also bogs, lakes, small patches of seminatural grasslands and arable fields. Twelve clear-cuts were selected (2-6 ha and logged 4-6 years prior). Six of them had been marked as coniferous forests on maps from the 1870s when the other six were marked as meadows. Clear-cuts on former meadows have higher amounts of herbs than clear-cuts which were formerly forests. Hence, our site selection strategy covered the wide range of flower abundances that occur on clear-cuts in the study area. PAN-TRAPS: The pans used to collect pollinators were painted in one of the following colours: blue, white and yellow with UV-reflecting-colour (Soppec, Sylva mark fluo marker, Nersac, France). The pans had a diameter of 8.7 cm, a volume of 0.5 L and were filled with non-toxic propylene glycol (40% concentration), to conserve the pollinators and to decrease the surface tension. A small opening (4 mm in diameter) at the top of each bowl was made to ensure that rainwater could drain. One set of pan-trap consisted of three pans, one in each colour, placed on a steel stick.Four sets of pan-traps were placed in each clear-cut, in the same height as the vegetation and in places that were considered representative for the clear-cut. During the main flight period of most pollinating insects, three sampling periods were conducted: in the beginnings of June, beginning of July and beginning of August. Each period lasted for one week and had at least some days with more than 17°C and wind velocity less than four on the Beaufort scale. The pans were covered with caps between collecting periods. When a new collecting period started, some sets of pan-traps were moved - at most 30 cm - or some of the vegetation was removed to prevent overgrowth.In total there were 48 set of pan-traps collecting during each period, but a few sets of pan-traps had been knocked down by animals and were therefore excluded (1, 1 and 2 during the first, second and third period, respectively). In addition, a single blue pan went missing during the second period. Four taxonomic groups dominated the catches – Aculeata, Lepturinae, Cetoniidae and Syrphidae – and they were identified to species-level. Aculeata was subdivided as solitary Apoidea, social Apoidea (Bombus spp. Apis mellifera), and Vespoidea (including one species of Chrysidoidea). Other insects caught, that are not identified, were mainly small Coleoptera, small Lepidoptera and Symphyta.FLOWER FREQUENCY: The clear-cuts were photographed in conjunction with each collecting period to estimate flower frequency. A 1 m2 square was placed on the ground and photographed from above (from c 160 cm height). Around each pan-trap, at least 25 such 1 m2 squares were photographed reflecting small-scale flower abundance (“trap scale”). An additional at least 100 pictures were systematically distributed along transects over the whole clear-cut reflecting large-scale (“clear-cut scale”) flower abundance. Photos were taken during each collecting period, or at most 5 days before or after. All 8048 photos taken were inspected to see if they held flowers within the 1-m2 square and if so of which colours (red, yellow, blue and white). The frequencies of colours (i) around set of pan-traps, and (ii) on clear-cuts were expressed as the odds for the colour occurring in a square metre plot: (0.5+p)/(0.5+(1-p)), where p=frequency of photos with the colour. Also, we calculated the odds for flower of any colour occurring in a plot.
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