1,721,036 research outputs found
Long-term decline in the abundance of leafhoppers and planthoppers (Auchenorrhyncha) in Central European protected dry grasslands
No full textLandscapes in Central Europe have changed considerably during the last five decades, while nature reserves have been less affected. However, there is growing concern that species richness and population size of animals in reserves may decrease even under protection. We performed a comparative study of the development in auchenorrhynchan communities of governmentally protected dry grasslands in Eastern Germany and tested whether reserves were effective in maintaining insect communities. The historical surveys are from 1963 to 1967. Between 2008 and 2010 we revisited 26 of the original sites and sampled leafhoppers and planthoppers by applying the same sampling technique as in the 1960s. Thus, we were able to perform a 40-year-comparison for auchenorrhynchan species richness and abundance. Comparisons capturing three successive years of each period allowed us to assess interannual variability in abundance. Species richness hardly differed between the two periods. However, some new species were found, and therefore species composition changed. Species abundance and overall numbers of individuals declined. Mainly species known to be very common dry grassland specialists exhibited strong declines in abundance. On average, only 27% of auchenorrhynchan numbers caught from 1964 to 1966 were recorded for the years 2008 to 2010. The results suggest that weather conditions and climate change are minor factors in the decline in auchenorrhynchan populations in recent years. Although the studied areas were under protection during the last 50 years, air-borne nitrogen deposition, the introduction of modern intense land use practices and alterations in plant communities, are likely to have influenced auchenorrhynchan abundance to a large extent. (c) 2012 Elsevier Ltd. All rights reserved.State of Lower Saxony (Ministry of Science and Culture
Scale-dependent diversity patterns. affect spider assemblages of two contrasting forest ecosystems
No full textSpiders are important generalist predators in forests. However, differences in assemblage structure and diversity can have consequences for their functional impact. Such differences are particularly evident across latitudes, and their analysis can help to generate a better understanding of region-specific characteristics of predator assemblages. Here, we analyse the relationships between species richness, family richness and functional diversity (FD) as well as alpha- and beta-components of epigeic spider diversity in semi-natural temperate and subtropical forest sites. As expected, within-plot and overall spider species and family richness were higher in the subtropical plots. In contrast, local FD within plots was similar between sites, and differences in FD only became evident at larger spatial scales due to higher species turnover in the subtropical forests. Our study indicates that the functional effects of predator assemblages can change across spatial scales. We discuss how differences in richness and functional diversity between contrasting forest ecosystems can depend on environmental heterogeneity and the effects of species filters acting at local scales. The high turnover observed in the species-rich subtropical forests also requires a more regional perspective for the conservation of the overall diversity and the ecological functions of predators than in less diverse forests, as strategies need to account for the large spatial heterogeneity among plots. (C) 2013 Elsevier Masson SAS. All rights reserved
The Collembola community of pure and mixed stands of beech (Fagus sylvatica) and spruce (Picea abies) of different age
No full textThe idea of establishing mixed forests that are better adapted to site conditions than spruce monocultures has attracted increasing attention of forest owners and governmental. institutions over the last decades. Currently, beech is being replanted and an increasing proportion of German forests are mixed stands. Focusing on the reaction of the soil fauna to forest conversion, this study investigates the response of the Collembola community to replacement of beech by spruce or by mixed stands of beech and spruce. Stands of different age were investigated in a factorial design with the factors stand type (beech, spruce and mixed stands) and stand age (30 and 120 years). Cottembola communities did not differ strongly between stand types and stand age and were dominated by Folsomia quadrioculata and Mesaphorura species (e.g. Mesaphorura macrochaeta). Moreover, neither total abundance of Collembota nor densities of the fungal feeding euedaphic Onychiurinae and Tullbergiinae significantly responded to stand type and stand age. The density of the epedaphic and partly herbivorous groups Symphypteona/Neelipleona and Entomobryidae in the 120-year-old stands significantly exceeded that in the 30-year-old stands; presumably, this was due to the well developed herb layer in the 120-year-old stands with more open canopies. Canonical correspondence analysis (CCA) of the Collembota community of the L/F horizon also indicated that most of the epigeic species were associated with the 120-year-old stands. Moreover, the diversity of Collembota significantly increased with forest age which likely reflects increased amount and diversity of food resources in the 120-year-old stands. The density of the hygrophilous species Fo. quadrioculata was significantly higher in the spruce than in the beech stands; probably this was due to the higher water content in litter of the spruce stands. Moreover, the results of the CCAs indicated that soil pH is an important structuring force for the Collembola communities. Overall, the results suggest that stand type and forest age impact Collembola communities, presumably via changes in the amount and quality of food resources, such as living plant and herb litter materials. The pronounced changes which occurred with forest age likely were related to the development of more dense and diverse herb layer in mature forests which provides additional food resources in particular for epedaphic species. On the other hand, dominant species/functional groups of Collembota, such as hemiedaphic species, appear to depend predominantly on abiotic factors, most importantly soil pH and soil water content. (C) 2007 Elsevier GmbH. All rights reserved
Increasing syrphid fly diversity and density in sown flower strips within simple vs. complex landscapes
No full text1. The structural complexity of agricultural landscapes influences the local biodiversity and associatedecosystem services. Hence, developing effective biodiversity management requires a betterunderstanding of the relative importance of local and landscape changes, especially for functionallyimportant organisms such as hoverflies benefiting from flowering plants.2. We examined hoverfly (Diptera: Syrphidae) communities in broad and narrow sown flowerstrips, in naturally developed grassy strips and in wheat fields (as a control). We also investigatedthe effects of these four habitat types on syrphid occurrence in the adjacent wheat fields.3. The relative influence of local vs. landscape effects was tested by selecting study sites along agradient of structural complexity from simple landscapes (100% arable land) to complex landscapes(up to 70% semi-natural habitats such as fallows, field margins, hedges and grassland).Landscape complexity was assessed within landscape sectors of 0Æ5–4Æ0 km radius around strips.4. Syrphid density and in particular, the density of aphidophagous species, was higher in narrow andbroad sown flower strips compared to grassy strips and wheat–wheat boundary controls at the milkripeningstage of the wheat. In addition, species richness of aphidophagous syrphids within wheatfields adjacent to broad sown flower strips was higher at the wheat peak-ripening stage. This indicatesa spillover between habitats and a positive effect of these sown flower strips on potential biocontrol ofcereal aphids. Flower densities and syrphid diversity and density, respectively, were closely related.5. Species richness and abundance in the sown flower strips increased as the proportion of arableland in the surrounding landscape increased, suggesting that within structurally simple landscapes(at 0Æ5–1 km radius around the sites) syrphid flies concentrated on the most rewarding resourceswithin the sown flower strips. Sown flower strips were more effective at increasing syrphid speciesrichness and abundance in simple landscapes, presumably because the creation of flower resourcesmade the greatest difference in such homogeneous, intensively managed arable landscapes.6. Synthesis and applications. Agri-environment schemes should take the surrounding landscapecharacteristics into account when considering using sown flower strips to enhance syrphid densityand diversity, and their biocontrol function, in arable landscapes. Creating locally such flower stripsis more effective in simple landscapes containing a high proportion of arable land, while in complexlandscapes, keeping the overall diversity is important
Abschlussbericht zum Forschungsvorhaben „Beiträge zur natürlichen und anthropogenen Stoffdispersion im Osterzgebirge - Quellen und Senken im Ökosystem zwischen Erzgebirgskamm und Talsperre Malter (Stoffdispersion Osterzgebirge) - Teil Limnologie" (1991 – 1994)
No full textZusammenfassung Im Rahmen eines interdisziplinären Forschungsvorhabens von Geowissenschaftlern und Biologen wurden zwischen 1991 und 1994 die anorganischen Stoffflüsse und die Gewässer im durch geogene und anthropogene Einflüsse stark belasteten Einzugsgebiet der Roten Weißeritz im Osterzgebirge untersucht. Ziel der limnologischen Forschungsarbeiten war die Ermittlung der Auswirkungen einzelner und miteinander kombinierter Systembelastungen auf die Gewässerbiozönosen. Untersuchungsschwerpunkte bildeten das Fließgewässersystem der Roten Weißeritz, in denen das Makrozoobenthos und die Fische bearbeitet wurden, und die als Schadstoffsenken fungierenden Stauseen Großer Galgenteich in der Kammregion und Talsperre Malter am unteren Ende des Untersuchungsgebietes, in denen sowohl das rezente Plankton und Benthos als auch in der Talsperre Malter die historische Belastungsentwicklung anhand der Änderungen der Diatomeen- und Cladocerenbesiedlung durch Sedimentkernanalysen untersucht wurden. Die oberen Bereiche des Untersuchungsgebietes waren insbesondere durch atmosphärische Schadstoffeinträge schwer geschädigt. Die Gewässer waren stark versauert und wiesen neben hohen Wasserstoffionenkonzentrationen auch hohe Metallbelastungen auf. Im oligotrophen, polymiktischen Großen Galgenteich lag der Schwerpunkt der Primärproduktion mit Juncus bulbosus bei den benthischen Makrophyten. Das Zooplankton war artenarm bei nur geringer Dichte. Das Fehlen von Fischen begünstigte invertebrate Räuber. Chironomiden stellten 2/3, Oligochaeten 1/3 der Abundanz des Benthos. Die Versauerungsbelastung machte sich durch episodische Säureschübe im gesamten Fließgewässersystem bis zur Talsperre Malter bemerkbar. Im mittleren und unteren Bereich war zusätzlich eine zunehmende Belastung vor allem durch häusliche Abwässer, teilweise auch durch landwirtschaftliche Einflüsse festzustellen. Die im oberen Bereich dominierenden Plecopteren wurden von Chironomiden und Oligochaeten abgelöst, Weidegänger und Zer-setzer durch Filtrierer und Sedimentfresser. Hauptbelastungsfaktoren in der dimiktischen Talsperre Malter stellten die hohe Trophie, hohe Metallkonzentrationen (v.a. Al, Mn, Cd, Zn) und hohe Fischdichten dar. Während der Sommerstagnation kam es zu anoxischen Bedingungen im Hypolimnion. Zooplankter waren in größerer Artenzahl und Dichte zu finden. Die Sedimentationsrate lag bei rund 2 cm pro Jahr. Das Benthos wurde von Oligochaeten dominiert. Die Belastungsgeschichte vom mesotrophen Ausgangszustand über eutrophe Verhältnisse bis zu hypertrophen Bedingungen war einschließlich des Auftretens von Versauerungsbelastungen gut in den Sedimenten dokumentiert
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Minor changes in orthopteran assemblages of Central European protected dry grasslands during the last 40 years
No full textDuring the past 50 years development of farming practices caused tremendous changes in European agricultural landscapes and many insect species became increasingly restricted to protected areas. Yet little is known about long-term trends of insect diversity and community composition in these often small reserves. We performed a comparative study on changes in orthopteran communities of protected dry grasslands in East Germany, which had been surveyed in the 1960s. Applying the same sampling techniques, we revisited 26 of the original sites in 2008 and 2009. Nearly all sites are controlled by conservation policies and changes in vegetation composition were relatively small, although some sites showed shrub encroachment. Changes in orthopteran diversity were not significant. Community composition showed minor changes which were correlated with evidence of woody plant encroachment as derived from historical and recent aerial imagery. The frequency of some Caelifera species decreased from the 1960s to 2008/2009 with one species inhabiting bare soils (Myrmeleotettix maculatus) showing the strongest decline. Some Ensifera, especially two species inhabiting open woodland and scrub (Tettigonia viridissima, Phaneroptera falcata) showed positive trends. Nevertheless, three different regions (each belonging to a different German federal state) had shown distinct orthopteran assemblages in the 1960s, and these were equally different 40 years later. We conclude that the orthopteran fauna of Central European protected dry grasslands showed small changes in species composition, and overall diversity remained rather constant during the past 40 years, which is in accordance with the minor changes in the surrounding landscape. Consequently, the applied conservation management practises-mainly sheep grazing and trimming-are largely effective
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