1,720,956 research outputs found
Dual-mycorrhizal plant functional responses following shifts in soil nutrient availability during ecosystem development
No full textThe majority of terrestrial plants form root symbioses with arbuscular mycorrhizal (AM) fungi to enhance nutrient (particularly phosphorus, P) acquisition. However, some of these plant species also form dual symbioses involving ectomycorrhizal (ECM) fungi. The factors driving plants to form dual-mycorrhizal symbioses is poorly understood. It has been suggested that these plants show plasticity in root symbioses to optimize nutrient acquisition depending on the type and strength of soil nutrient limitation (e.g., N vs. P). Alternatively, the degree of investment or ?preference? in particular root symbioses might simply reflect differences in inoculum potential among soils of contrasting nutrient availability, reflecting adaptations of root symbionts to different edaphic conditions. To better understand the ecology of dual-mycorrhizal plants, we grew two co‐occurring plant species forming AM and ECM (Acacia rostellifera and Melaleuca systena) symbioses in soils of increasing age and contrasting nutrient availability from an Australian long‐term soil chronosequence. Specifically, we aimed to disentangle the relative importance of abiotic factors (e.g., soil nutrient availability) and biotic factors (e.g., soil inoculum potential) in determining root colonization patterns and functional outcomes of these multiple root symbioses. For both plant species, we found clear hump‐shaped plant growth patterns along the strong gradient in soil nutrient availability, with peak growth in intermediate‐aged soils, while high levels of mycorrhizal colonization by the ?preferred? root symbionts were maintained across all soils. We found large increases (540%) in foliar manganese concentrations with increasing soil age and declining P availability, suggesting that plants may be relying on the release of carboxylates to help acquire P in the most P‐impoverished soils. Finally, we found that soil abiotic properties, such as strong differences in soil nutrient availability, are generally more important than soil inoculum potential in explaining these shifts in our plant and root responses. Our study suggests that plants capable of forming dual-mycorrhiza root symbioses show plasticity in their nutrient‐acquisition strategies following shifts in soil nutrients during long‐term ecosystem development, yet maintain a preference for certain root symbionts despite changes in soil microbial inoculum.Fil: Teste, Francois Philippe. University of Western Australia; Australia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Laliberté, E.. University of Western Australia; AustraliaII International Symposium Mycorrhizal Symbiosis in South AmericaSan Carlos de BarilocheArgentinaUniversidad Nacional del ComahueUniversidad Austral de ChileUniversidad Nacional del Comahue. Instituto Andino Patagónico de Tecnologías Biológicas y GeoambientalesUniversidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambient
Plant-soil feedback in the ‘real world’: how does fire fit into all of this?
Full text linkAims: Plant–soil feedback (PSF) is an important mechanism controlling plant growth, vegetation dynamics, and longer-term and larger-scale patterns of plant community diversity. We know that feedback between plants and soil biota depends on several external factors, such as nutrient and water availability, and interactions with neighbouring plants. We argue that in the ‘real world’, PSF are not working in isolation but instead proceed within a complex context of multiple interacting factors. Fire is one of those complex external factors which could greatly alter PSF by re-setting or re-directing plant-soil biota interactions.
Methods: We reviewed key literature on the effects of fire on soil biota and soil physicochemical properties with soil depth, to generate predictions on the complex effects of fire on PSF.
Results: We highlight that fire has strong potential to directly and indirectly affect the strength of PSF. To what extent this influences longer-term plant community trajectories depends on the interactions between fire characteristics and ecosystem type. Here, we conceptualized these effects of fire on soil properties and biota, and then discuss the main pathways through which fire should alter PSF.
Conclusions: We think that PSF processes should be nullified under and after fire. Average neutral PSF responses are expected to be more common in the short-term or within the timeframe required for major soil microbial players to regain their pre-fire abundances and diversity. We conclude by providing directions for future research and possible methods to study fire effects on PSF both in the field and under controlled conditions.EEA San LuisFil: Kardol, P. Swedish University of Agricultural Sciences. Department of Forest Ecology and Management; SueciaFil: Yang, T. Agriculture and Agri-Food Canada. Swift Current Research & Development Centre; CanadáFil: Arroyo, Daniel Nicolas. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Luis; ArgentinaFil: Teste, Francois Philippe. Agriculture and Agri-Food Canada. Swift Current Research & Development Centre; CanadáFil: Teste, Francois Philippe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis; ArgentinaFil: Teste, Francois Philippe. Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis; Argentin
Associations between fungal root endophytes and grass dominance in arid highlands
No full textIn arid highland environments harsh conditions for vegetation establishment prevail. Plants in theseenvironments develop different strategies to survive, including associations with fungal root endophytes.These associations may improve plant growth, helping plant resistance to adverse environments. Theaim of this study was to determine the relationship among arbuscular mycorrhizal fungi (AMF), darkseptate endophytes (DSE) and dominance degree of Poaceae in arid highlands of Argentine Puna. Westudied AMF and DSE root colonization, and rhizospheric hyphal densities of dominant and subordinategrass species. Dual and positive associations between AMF and DSE prevailed. Dominant grasses had thehighest levels of AMF and DSE root colonization. Dominant and intermediate grasses were associatedwith the highest values of rhizospheric hyphal density. In Puna highlands, the interactions among AMF,DSE and grasses suggest that fungal root endophytes may play a role in structuring grass communities bydifferentially improving the resistance to harsh conditions.Fil: Menoyo, Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Teste, Francois Philippe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Ferrero, Marcela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Lugo, Mónica Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto Multidisciplinario de Investigaciones Biológicas de San Luis; Argentin
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
Changes in ectomycorrhizal fungal community composition and diversity along a two-million year coastal dune chronosequence in a biodiversity hotspot
No full textEctomycorrhizal (ECM) fungi enhance plant nitrogen (N) and phosphorus (P) acquisition. During long-term soil and ecosystem development, plant growth shifts from being N-limited to P-limited. However, how community composition and diversity of ECM fungi change during ecosystem development remains unknown. We studied ECM communities and diversity along a two million year Australian dune chronosequence, which shows a clear shift from N- to P-limitation of plant growth with increasing soil age. We hypothesised that ECM community composition strongly varies along the chronosequence, reflecting soil properties, and that diversity increases during pedogenesis. We grew two ECM plant species in soils collected from five distinct chronosequence stages, and quantified ECM operational taxonomy units (OTU) and diversity on roots using next-generation sequencing. To distinguish changes in ECM community composition due to soil properties vs ECM inoculum, we used three soil treatments: i) unaltered soil from each stage (?as is?), ii) triple-pasteurised, mixed soil from all five stages, with addition of live soil inoculum from each particular stage (?specific inoculum?), and iii) triple-pasteurised soil from particular stages, with addition of mixed live inoculum from all five stages (?average inoculum?). We obtained 175 unique ECM OTUs. ECM differed considerably among chronosequence stages in the ?as is? treatment, and these differences were associated with shifts in soil pH and nutrients. Furthermore, OTU richness declined with soil age in the ?as is? treatment. In contrast, there were no differences in ECM community composition or richness in the other two soil treatments. We suggest that strong changes in ECM community composition and diversity along this chronosequence do not simply reflect differences in soil abiotic properties or ECM inoculum, but reflect complex long-term interactions between these factors. Finally, we surmise that the decline in OTU richness is due to few ECM species being effective at acquiring P from severely P-impoverished soils.Fil: Albornoz, F.. No especifíca;Fil: Teste, Francois Philippe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi". Universidad Nacional de San Luis. Facultad de Ciencias Físico, Matemáticas y Naturales. Instituto de Matemática Aplicada de San Luis "Prof. Ezio Marchi"; ArgentinaFil: Lambers, H.. No especifíca;Fil: Bunce, M.. No especifíca;Fil: Murray, Dáithí C.. No especifíca;Fil: White, Nicole E.. No especifíca;Fil: Laliberté, E.. No especifíca;Eighth International Conference on Mycorrhiza (ICOM8): Mycorrhizal Integration Across Continents & ScalesFlagstaffEstados UnidosInternational Mycorrhiza Societ
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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