177,043 research outputs found
Reciprocal extrapolation of species distribution models between two islands – Specialists perform better than generalists and geological data reduces prediction accuracy
No full textThis study aims to test the extrapolation effects of species distribution models (SDM) using three groups of predictor variables: climate, relief and geology (bedrock type). We highlight potential ecological differences for selected taxa, regarding both generalists and specialists in terms of edaphic conditions. We used distributional data of 12 woody species shared by two large Mediterranean islands (Crete and Sicily) to calibrate Maxent models of their potential distribution. We trained models with data from Crete and extrapolated to Sicily and vice versa. We tested ten proxies for the three variable groups and compared AUC values as a measure of model performance. Extrapolation of SDMs worked fairly well across species and islands for those models including climatic and relief data, while those including geological information performed worse for the tested species. Edaphic generalists performed less well compared to edaphic specialists. The latter performed best with climate data included in models and more poorly with only geological data. This may be due to differences in bedrock type affinities of species between the two islands
Alien plant invasions in Mediterranean habitats. An assessment for Sicily
No full textLevels of plant invasions in different habitat types were assessed in several regional studies, but few of them were from the Mediterranean. Here we compare the levels of vascular plant invasion across habitats and plant communities of Sicily. We used a large dataset of plant species presences/absences in vegetation plots to analyze the invasion patterns across habitats considering biogeography, life form and phenology of alien plants. Vegetation plots were classified based on the EUNIS classification of European habitats. The invasiveness of each species was expressed in terms of its absolute and percentage frequency. Representation of different life forms and phenological patterns was compared between alien and native species. The fidelity of alien species to individual habitats was calculated using the phi coefficient. Our analysis shows that annual and woody species are the most represented life forms in the alien flora of Sicily and that alien species tend to have a longer flowering period than the native species. The investigated habitats differed strongly in their level of invasion by alien species, ranging from 0 to 15.6% of aliens of all species recorded. Most of the habitats were colonized by very few alien species or completely lacked them, except for sandy coasts, naturally-disturbed riverbeds, and synanthropic habitats. It must be noted, however, that the number of alien species occurring in a given habitat does not relate to the severity of the impact of invasion in that habitat. Some habitats are invaded by few (or single) species, which attain a high cover, transforming the whole ecosystem. The habitat-based approach proved to be suitable for evaluating the habitat specificity and frequency of alien species at a regional scale, improving the capacity for risk assessment in different ecological contexts
Thirty years unmanaged green roofs: Ecological research and design implications
No full textThe variations in species composition and assemblage of unmanaged simple-intensive green roofs in
Hannover, Germany, were investigated over a thirty year period, in order to assess the persistence of
the initial seed mixture and to evaluate floristic changes. The roofs were greened in 1985 with soilbased
turf rolls sown with a mixture of five grasses (Festuca rubra, Festuca ovina, Agrostis capillaris, Lolium
perenne and Poa pratensis). Three sets of 120 phytosociological relevés, sampled in 1987, 1999 and 2014,
have been compared to assess: (1) nestedness vs spatial turnover, (2) functional diversity and (3) the
importance of vegetation dynamics on green roof performance and design. Results demonstrated that
from 1987 to 1999 the species diversity increased and the species turnover prevailed over nestedness,
due to the progressive niche occupation by new species. In contrast, from 1999 to 2014 species diversity
remained steady, suggesting that nestedness prevailed over species turnover. The main driver of the
observed functional changes was a shift towards relatively more thermoxeric conditions. In terms of
plant life strategies, the competitive species sown on the roof gradually gave way to stress-tolerant and
ruderal species, along with a progressive increase in species with shortdistance seed dispersal strategies.
It is concluded that: (a) to create resilient green roofs, spontaneous colonisation should be accepted
and considered as a design factor; and (b) regional plant communities could serve as a model for seed
recruitment and installations
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
"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.
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
Letter from R. R. Zellick, Assistant Trust Officer, Anglo California National Bank of San Francisco, to Joseph R. Goodman, October 2, 1942
No full textLetter from R. R. Zellick, Assistant Trust Officer at The Anglo California National Bank of San Francisco, to Joseph R. Goodman, regarding property owned by Dave Tatsuno. Zellick mentions a dispute between current tenants and Tatsuno, and that Tatsuno has asked Goodman to help locate trustworthy tenants.Personal correspondence, organizational records, government documents, publications, and other papers created or collected by Joseph R. Goodman documenting the forced removal and incarceration of Japanese Americans during World War II, as well as organized resistance to incarceration. Included in the collection are records of the Japanese Young Men's Christian Association and the Japanese American Citizens' League in San Francisco, including papers of the Japanese YMCA's executive secretary Lincoln Kanai; Sakai family papers; Goodman's correspondence to and from Japanese American incarcerees, organizations opposing forced removal and incarceration of Japanese Americans, the War Relocation Authority, and others; publications, photographs, and ephemera from the Topaz Relocation Center, where Goodman taught high school; War Relocation Authority records and publications; and newspaper clippings, pamphlets, and reports about forced removal and incarceration created by various government, religious, and civic organizations, in California and nationwide
Unraveling the Influences of Edaphic and Topographic Factors on High-Mountain Plant Communities: first results from the MO.MO.ME. Project
No full textThe Project ‘Monitoring Network for Studying the Effects of Climate Change on Mediterranean High-Mountain Grasslands
in Natura2000 Sites (MO.MO.ME.)’ aims at analyzing the differences in plant communities, microclimate, and
topography across various study areas. The main goal is to improve understanding of the biotic and abiotic factors
regulating the assembly of high-mountain communities, focusing on the functional and structural dynamics of Mediterranean
grasslands.
We present the first results of our analysis focused on the role of edaphic and topographic gradients on vegetation
patterns above 1900 m a.s.l. on Pizzo Carbonara (Madonie Mountains, Northern Sicily), a carbonate massif shaped by
karst erosion, resulting in a system of sinkholes and windy ridges across the summit plateau. We sampled 42 vegetation
plots, georeferenced using sub-metric GPS. Various topographic variables were derived from Sicily’s regional
technical map (2 m resolution) using QGIS. Additionally, chemical and biochemical soil parameters were analyzed for
each plot.
Plant species were classified into three life-form groups: chamaephytes, hemicryptophytes, and therophytes. Data
were analyzed using three response variables: species richness, vegetation cover, and species composition. For the
first two, we applied a Generalized Linear Model (GLM), while compositional data were processed using distance-based
redundancy analysis (db-RDA) with variation partitioning.
The results indicate that life forms are differentially filtered by edaphic and topographic variables. The topographic
factors influence the relative performance of co-occurring vascular plant species, shaping the structure and composition
of local plant communitie
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