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Heathland plant species composition and vegetation structures reflect soil‐related paths of development and site history
No full textAbstract Questions To improve our knowledge on how environmental conditions determine the development of high‐value Calluna vulgaris heathland habitats, we studied the floristic and structural characteristics of heathland plant communities across North Germany and how they are influenced by edaphic, climatic and management factors. We ask how heathland development is related to these factors and what are the implications for conservation management and restoration. Location North German Plain. Methods We collected 350 relevés in 18 dry Calluna heathland areas. Plant communities were classified using Isopam, and Redundancy Analysis (RDA) determined effects of environmental conditions. Potential pathways of development and the nature conservation status of the communities were identified on a multifactorial basis. Results We found nine floristically and structurally distinct heathland plant communities. Heathland vegetation showed distinct patterns along Calluna age development stages and environmental conditions. Soil conditions and related effects of long‐term site history and recent management turned out to be the predominant factors influencing species composition and diversity, resulting in three potential heathland succession pathways. Mosaic‐like communities with particularly high taxonomic diversity and conservation value occurred on early‐successional inland dunes or as regeneration stage growing on nutrient‐poor sandy soils without humus accumulation. Conclusions The study reveals fundamental differences between historically farmed heathland in the oceanic Northwest and former military training areas mainly in northeastern Germany with consequences for restoration ecology. Present nature conservation criteria turned out to be insufficient in predicting habitat quality, as lichens are frequently disregarded. Our findings highlight the need for intense soil disturbance to maintain early‐stage soil conditions and a diverse Calluna growth‐phase composition, as these factors essentially determine species richness in lowland heaths.We studied the factors characteristic of Calluna vulgaris dry lowland heathlands in North Germany. Land use, both past and present, as well as management effects on soil conditions strongly influence heathland structures and diversity. We identified two pathways, psammophilous and consolidated sand heath trajectories, each with stages different in species composition, lichen richness, age structure composition and nature conservation value. imageGerman Federal Environmental Foundation http://dx.doi.org/10.13039/10000763
Close to the edge: Spatial variation in plant diversity, biomass and floral resources in conventional and agri‐environment cereal fields
No full textAbstract Non‐crop (segetal) plants in arable systems are commonly perceived simply as ‘weeds’, that is, harmful at worst and undesirable at best. The increase in management intensity in European arable systems has vastly reduced the populations of all but the most disturbance‐tolerant plant species, negatively impacting the whole agricultural food web. In recent years, efforts have been made to promote agricultural biodiversity through measures such as flower strips and unsprayed field margins. However, studies of their impacts on the arable flora have rarely considered their spatial variation within the crop field. We investigated the spatial distribution of vascular plant species richness and their contribution to the food web via biomass and flower units in conventional and agri‐environment cereal fields in six regions of Germany. We studied two types of in‐crop measures (extensive cereals without pesticides or fertiliser, and with or without intercropping with flowering species) and one adjacent measure (neighbouring flower strip), recording at 1‐m intervals from the field edge to the interior. These results were then extrapolated to illustrate the effects of these measures on resource provision at the field scale. Species richness and plant biomass dropped off sharply after the first metre in the conventional treatments, regardless of the adjacent habitat. The ‘extensive’ treatments maintained a much higher level of diversity and resource provision in the field interior. At the field level, this can mean more than a 60‐fold difference in the provision of flowering resources between conventional management (1900 flower units/ha) and agri‐environment measures (AEMs) (127,000 units/ha for extensive cereals). Synthesis and applications . The strong edge effects we found in conventional cultivation support the premise that reducing field sizes could play a role in promoting in‐crop biodiversity. However, incorporating extensive field margins as an AEM would be more efficient at maximising the diversity of generalists whilst maintaining high yields.Zusammenfassung Ackerwildkräuter (sogenannte Segetalpflanzen) werden häufig einfach als ‘Unkraut’ wahrgenommen, d. h. schlimmstenfalls als schädlich und bestenfalls als unerwünscht. Die zunehmende Bewirtschaftungsintensität in europäischen Ackerbausystemen hat die Populationen aller Ackerwildkräuter mit Ausnahme der störungsresistentesten stark reduziert, was sich negativ auf das gesamte landwirtschaftliche Nahrungsnetz auswirkt. In den letzten Jahren wurden Anstrengungen unternommen, die biologische Vielfalt in der Landwirtschaft durch Maßnahmen wie Blühstreifen und ungespritzte Feldränder zu fördern. Bei der Untersuchung ihrer Auswirkungen auf die Ackerflora wurde jedoch nur selten ihre räumliche Variation innerhalb des Ackers berücksichtigt. Wir haben die räumliche Verteilung der Ackerwildkrautdiversität sowie deren Biomasse und die Anzahl von Blüteneinheiten in konventionellen und agrarumweltgerechten Getreidefeldern in sechs Regionen Deutschlands studiert. Wir untersuchten zwei Maßnahmen in der Kultur (Extensivgetreide mit oder ohne blühende Untersaat) und eine angrenzende Maßnahme (benachbarter Blühstreifen) und platzierten Aufnahmen in Abständen von 1 m vom Feldrand bis ins Feldinneren. Diese Ergebnisse wurden dann extrapoliert, um die Auswirkungen dieser Maßnahmen auf die Ressourcenbereitstellung auf der Feldskala zu veranschaulichen. Der Artenreichtum und die Pflanzenbiomasse nahmen im konventionellen Getreide nach dem ersten Meter stark ab, unabhängig vom angrenzenden Vegetationstyp. Diese Abnahme war im Extensivgetreide viel schwächer ausgeprägt. Auf der Feldebene kann dies einen mehr als sechzigfachen Unterschied in der Bereitstellung von Blütenressourcen zwischen der konventionellen Bewirtschaftung (1900 Blüteneinheiten/ha) und dem Extensivgetreide (127.000 Einheiten/ha) bedeuten. Synthese und Anwendung in der Praxis . Die starken Randeffekte, die wir bei der konventionellen Bewirtschaftung feststellten, unterstützen die Annahme, dass die Verringerung der Feldgröße eine Rolle bei der Förderung der biologischen Vielfalt spielen dürfte. Die Anlage von Extensivgetreidestreifen am Feldrand als Agrarumweltmaßnahme wäre jedoch ein effizienterer Weg, um die Vielfalt der Generalisten zu erhöhen und gleichzeitig hohe Erträge zu erhalten.Abstract Non‐crop (segetal) plants in arable systems are commonly perceived simply as ‘weeds’, that is, harmful at worst and undesirable at best. The increase in management intensity in European arable systems has vastly reduced the populations of all but the most disturbance‐tolerant plant species, negatively impacting the whole agricultural food web. In recent years, efforts have been made to promote agricultural biodiversity through measures such as flower strips and unsprayed field margins. However, studies of their impacts on the arable flora have rarely considered their spatial variation within the crop field. We investigated the spatial distribution of vascular plant species richness and their contribution to the food web via biomass and flower units in conventional and agri‐environment cereal fields in six regions of Germany. We studied two types of in‐crop measures (extensive cereals without pesticides or fertiliser, and with or without intercropping with flowering species) and one adjacent measure (neighbouring flower strip), recording at 1‐m intervals from the field edge to the interior. These results were then extrapolated to illustrate the effects of these measures on resource provision at the field scale. Species richness and plant biomass dropped off sharply after the first metre in the conventional treatments, regardless of the adjacent habitat. The ‘extensive’ treatments maintained a much higher level of diversity and resource provision in the field interior. At the field level, this can mean more than a 60‐fold difference in the provision of flowering resources between conventional management (1900 flower units/ha) and agri‐environment measures (AEMs) (127,000 units/ha for extensive cereals). Synthesis and applications . The strong edge effects we found in conventional cultivation support the premise that reducing field sizes could play a role in promoting in‐crop biodiversity. However, incorporating extensive field margins as an AEM would be more efficient at maximising the diversity of generalists whilst maintaining high yields.Zusammenfassung Ackerwildkräuter (sogenannte Segetalpflanzen) werden häufig einfach als ‘Unkraut’ wahrgenommen, d. h. schlimmstenfalls als schädlich und bestenfalls als unerwünscht. Die zunehmende Bewirtschaftungsintensität in europäischen Ackerbausystemen hat die Populationen aller Ackerwildkräuter mit Ausnahme der störungsresistentesten stark reduziert, was sich negativ auf das gesamte landwirtschaftliche Nahrungsnetz auswirkt. In den letzten Jahren wurden Anstrengungen unternommen, die biologische Vielfalt in der Landwirtschaft durch Maßnahmen wie Blühstreifen und ungespritzte Feldränder zu fördern. Bei der Untersuchung ihrer Auswirkungen auf die Ackerflora wurde jedoch nur selten ihre räumliche Variation innerhalb des Ackers berücksichtigt. Wir haben die räumliche Verteilung der Ackerwildkrautdiversität sowie deren Biomasse und die Anzahl von Blüteneinheiten in konventionellen und agrarumweltgerechten Getreidefeldern in sechs Regionen Deutschlands studiert. Wir untersuchten zwei Maßnahmen in der Kultur (Extensivgetreide mit oder ohne blühende Untersaat) und eine angrenzende Maßnahme (benachbarter Blühstreifen) und platzierten Aufnahmen in Abständen von 1 m vom Feldrand bis ins Feldinneren. Diese Ergebnisse wurden dann extrapoliert, um die Auswirkungen dieser Maßnahmen auf die Ressourcenbereitstellung auf der Feldskala zu veranschaulichen. Der Artenreichtum und die Pflanzenbiomasse nahmen im konventionellen Getreide nach dem ersten Meter stark ab, unabhängig vom angrenzenden Vegetationstyp. Diese Abnahme war im Extensivgetreide viel schwächer ausgeprägt. Auf der Feldebene kann dies einen mehr als sechzigfachen Unterschied in der Bereitstellung von Blütenressourcen zwischen der konventionellen Bewirtschaftung (1900 Blüteneinheiten/ha) und dem Extensivgetreide (127.000 Einheiten/ha) bedeuten. Synthese und Anwendung in der Praxis . Die starken Randeffekte, die wir bei der konventionellen Bewirtschaftung feststellten, unterstützen die Annahme, dass die Verringerung der Feldgröße eine Rolle bei der Förderung der biologischen Vielfalt spielen dürfte. Die Anlage von Extensivgetreidestreifen am Feldrand als Agrarumweltmaßnahme wäre jedoch ein effizienterer Weg, um die Vielfalt der Generalisten zu erhöhen und gleichzeitig hohe Erträge zu erhalten.Bundesministerium für Umwelt, Naturschutz, nukleare Sicherheit und Verbraucherschutz https://doi.org/10.13039/50110001354
Elytrigia repens co-occurs with glycophytes rather than characteristic halophytes in low-growing salt meadows on the southern Baltic Sea coast
No full textPatterns and drivers of deadwood quantity and variation in mid-latitude deciduous forests
No full text
The Calluna life cycle concept revisited: implications for heathland management
No full textAbstract
Heather, Calluna vulgaris, is a key species of European dry heath and central determinant of its conservation status. The established Calluna life cycle concept describes four phases—pioneer, building, mature, and degeneration—distinguishable by growth and vitality characteristics of undisturbed plants grown from seeds. However, little is known about the life cycle and ageing of plants subjected to severe disturbance, although measures to this effect (burning, mowing) are common in heathland management. We studied the vitality of over 400 heather plants by examining multiple morphological (plant height, long shoot and inflorescence lengths, flowering activity), anatomical (growth rings) and environmental (management, nitrogen deposition, climate) attributes. We found Calluna vitality to be mainly determined by the aboveground stem age, and that severe disturbances promote vigorous vegetative regeneration. Ageing-related shifts in the habit and vitality of plants resprouting from stem-base buds is similar to that of seed-based plants, but the former revealed higher vitality when young, at the cost of a shorter life span. In contrast, plants originating from decumbent stems resemble building-stage plants but apparently lack the capacity to re-enter a cycle including stages other than degeneration-type. As a consequence, we supplemented the established heather life cycle concept with a post-disturbance regeneration cycle of plants derived from resprouting. We conclude that management of dry lowland heathlands should include rotational small-scale severe disturbance to support both seed germination and seedling establishment as well as vegetative regeneration chiefly of young heather plants capable of resprouting from buds near rootstock.Deutsche Bundesstiftung Umwelt http://dx.doi.org/10.13039/100007636Georg-August-Universität Göttingen (1018
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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