177,427 research outputs found
A preliminary floristic classification of southern and northern Victoria Land vegetation, continental Antarctica
No full textThis paper proposes a new objectively-generated vegetation classification for southern and northern Victoria Land (continental Antarctica) based on the floristic composition of the plant communities. The new classification aims to integrate the existing physiognomic classification of the cryptogamic Antarctic tundra,
provide useful data on floristic composition and distribution of the vegetation occurring in southern and northern Victoria Land, and develop a suitable tool allowing easy comparison of syntaxa from different locations. Field data from 26 sites along a latitudinal gradient (728–778S) were analysed by a hierarchical classification integrated with multivariate statistics, including indirect ecological information (Principal Component Analysis). Similarity of the identified groups was assessed through the Jaccard similarity index. The new classification is compatible with previous ones and is widely applicable to Victoria Land and includes previous classification. This standardized approach relates plant communities to their floristic composition and provides a basis for relating vegetation composition to environmental gradients and to patterns of vegetation dynamics and succession which are still poorly understood in Antarctica
<em>Caloplaca coeruleofrigida</em> sp. nova, a species from continental Antarctica
No full textlav Antarktis CaloplacaCaloplaca coeruleofrigida Søchting & Seppelt is described from Southern Victoria Land, continental Antarctica. It is characterized by vertically elongated papillae and a pale orange pigmentation on shaded parts, and black thallus and apothecia on exposed parts of the thallu
Windmill Islands Vegetation GIS Dataset
No full textProgress Code: completedThis is a GIS dataset of the vegetation of the Windmill Islands. <br/>Interpretation was done by Rod Seppelt (Australian Antarctic Division) based on his field work, Zeiss aerial photography flown in January 1994 and a paper: Melick, D.R., Hovenden, M.J., Seppelt, R.D. (1994) Phytogeography of bryophyte and lichen vegetation in the Windmill Islands, Wilkes Land, Continental Antarctica. Vegetatio 111. 71-87 The data have been formatted according to the SCAR Feature Catalogue (see link below)
How do Changes in Land Use Patterns Affect Species Diversity? an Approach for Optimizing Landscape Configuration
No full textHeterogeneity of agricultural landscapes is supposed to be of significant importance for species diversity in agroecosystems (Weibull et al. 2003). Thus it is necessary to account for structural aspects of landscapes in land management decision processes. Spatial optimization models of land use can serve as tools for decision support. These models can aim at various landscape functions like nutrient leaching and economical aspects (Seppelt and Voinov 2002), water quality (Randhir et al. 2000) or habitat suitability (Nevo and Garcia 1996). However neighbourhood effects stay unconsidered in these approaches. In this paper we present an optimization model concept that aims at maximizing habitat suitability of selected species by identifying optimum spatial configurations of agricultural land use patterns. Bird species with diverging habitat requirements were chosen as target species. Habitat suitability models for these species are used to set up the performance criterion. Landscape structure is quantified by landscape metrics (McGarigal et al. 2002) estimated within the species home range. Statistical significance of these metrics for species presence was proven by a logistic regression model (Fielding and Haworth 1995). The landscape is represented by a grid based data set. Based on a genetic algorithm the optimization task is to identify an optimum configuration of model units. These model units are defined by contiguous cells of identical land use. Within this concept we can study how optimum but possibly artificial landscapes vary in structure depending on the selected species for which habitat suitability is maximized.
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Biostratigraphy and sedimentary sequences of the Toarcian Hainberg section (Northwestern Harz foreland, Northern Germany)
No full textA temporary outcrop in southern Lower Saxony permitted the sedimentological, geochemical and palaeontological investigation of a 40.8 m thick Toarcian section, from the top of the Amaltheenton Formation, through the Posidonienschiefer and Jurensismergel Formations, to lower parts of the Opalinuston Formation. Bed by bed collected ammonites and belemnites, bivalve associations, as well as data from neighbouring sections indicate a largely complete sequence of ammonite zones and subzones for the Lower Toarcian. A prominent stratigraphic gap at the Posidonienschiefer/Jurensismergel Formation boundary probably comprises the Semipolitum Subzone as well as the Variabilis and Thouarsense Zones. Above a condensed Dispansum Zone follows the higher Upper Toarcian with a presumably largely complete sequence of zones and subzones, although direct evidence for this is only sporadic. However, a thin condensed bed with stromatolite crusts is recognisable at the boundary Pseudoradiosa to Mactra/Aalensis Subzone. The Toarcian/Aalenian boundary can only be drawn on basis of belemnite finds at another thin condensed bed. Only a few metres above, the Opalinum Zone is evident by ammonite findings. Based on discontinuities, lithofacies, biofacies and correlations with neighbouring sections, a subdivision into alloformations, which largely correspond to formations, is applied. Based on that, a sequence stratigraphic interpretation with respect to third order transgression-regression cycles (T-R sequences) can be inferred: Above the regressive upper parts alloformation 1 (Amaltheenton Formation) with a maximum regression surface (mrs) near its top, the T-R sequence of the alloformation 2 (Posidonienschiefer Formation) is developed, with a maximum flooding surface (mfs) at the transition Falciferum/Commune Subzone and the regressive phase within the later Bifrons Zone. For the Commune Subzone, belemnite alignment indicates a seawater bottom current from SSE. The following maximum regression surface (mrs) lies near the Bifrons/Variabilis Zone boundary. The next sequence is not preserved at the studied location, but is preserved further East as well as further West, represented by the transgressive Dörnten Member (Variabilis and Thouarsense Zone). However, the regressive phase (Fallaciosum Subzone) is also missing there, indicated by a prominent sequence boundary with erosional relief at the base of the Dispansum Zone. The following alloformation 3 (Jurensismergel Formation and lowermost parts Opalinuston Formation) represents another T-R sequence with a maximum transgressive surface (base Mactra/Aalensis subzone) and a slightly thicker regressive Aalensis Subzone. The following maximum regression surface represents the boundary to alloformation 4 (major parts of Opalinuston Formation), followed again by a short transgressive phase (Pseudolotharingicum Subzone), condensation horizon and a longer regressive phase (Opalinum Zone). These sequence stratigraphic interpretations are largely consistent with previous investigations in Northern and Southern Germany. Minor deviations in the timely position of maximum flooding and regression surfaces likely reflect effects of a higher subsidence at variable sedimentation rate in the North German Basin. With respect to the, at the site of investigation, incompletely exposed Opalinuston Formation, further studies on complete drill core sections are required
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Heard Island lichen samples collected by John Jenkin in 1980
No full textProgress Code: completedStatement: Not all samples were collected by John Jenkin, hence one sample collection date in March is unknown. Only approximate locations are available.A description of lichen samples collected from Heard Island during March of 1980. The samples were mostly collected by John Jenkin, but some other collectors were also used. On return to Australia, the samples were lodged with the Australian Antarctic Division Herbarium (Code- ADT) under the control of Rod Seppelt. The samples are distinguishable within the herbarium by their 3 digit code.<br/><br/>The dataset details the date each collection was made on, as well as an approximate descriptive location. Unless otherwise specified, all samples were collected by John Jenkin
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
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