276 research outputs found
Species evenness affects ecosystem processes in situ via diversity in the adaptive strategies of dominant species
No full textCommunity biomass production reflects species evenness (relative abundance), suggesting that particular adaptive/survival strategies contribute disproportionately to ecosystem processes. We hypothesized that diversity in the strategies of dominant species would be a better predictor of biomass production than species diversity per se. We compared species diversity, strategy diversity, peak biomass, soil and leaf nutrient status, and leaf area index (LAI) in situ for related sub-alpine plant communities differing only in the intensity of cattle grazing and manuring; with identical climatic exposure, slope, aspect and parent material. Greater total biomass was associated with greater strategy richness and evenness and, to a lesser extent, species evenness-but species richness and aboveground biomass were not significantly different. Diversity in the adaptive strategies of dominant species allowed more effective deployment of canopy biomass (greater LAI), providing superior photosynthetic nutrient use efficiencies and greater total biomass despite lower nutrient status. This was reflected in species evenness, but not species richness
LA BETA-LATTAMASI A SPETTRO ESTESO NEI BATTERI GRAM-NEGATIVI IN ITALIA. ABSTRACT: 10° CONGRESSO NAZIONALE SIMMOC, SIENA 19-21 GIUGNO 2002
No full textSpecies evenness affects ecosystem processes in situ via diversity in the adaptive strategies of dominant species.
No full textCommunity biomass production reflects species evenness (relative abundance), suggesting that particular adaptive/survival strategies contribute disproportionately to ecosystem processes. We hypothesized that diversity in the strategies of dominant species would be a better predictor of biomass production than species diversity per se. We compared species diversity, strategy diversity, peak biomass, soil and leaf nutrient status, and leaf area
index (LAI) in situ for related sub-alpine plant communities differing only in the intensity of cattle grazing and manuring; with identical climatic exposure, slope, aspect and parent material. Greater total biomass was associated with greater strategy richness and evenness and, to a lesser extent, species evenness— but species richness and aboveground biomass were not significantly different. Diversity in the adaptive strategies of dominant species allowed more effective deployment of canopy biomass (greater LAI), providing superior photosynthetic nutrient use efficiencies and greater total biomass despite lower nutrient status. This was reflected in species evenness, but not species richness
CHARACTERIZATION OF AN ESBL, PER-1-LIKE PRODUCED BY A CLINICAL ISOLATE OF ALCALIGENES FAECALIS FROM AN ICU OF A N ITALIAN HOSPITAL
No full textRisultati preliminari dell’impiego del sistema MGIT per la diagnosi microbiologica di infezioni da micobatteri, per la valutazione diretta e indiretta della suscettibilità all’isoniazide e identificazione con probe da coltura
No full textEpidemiologia delle batteriemie e tempi di positivizzazione delle emocolture: valutazione di due sistemi automatici
No full textDisturbance is a principal alpha-scale filter determining niche differentiation, coexistence and biodiversity in an alpine community
No full text1. Many current biodiversity theories assume that resource competition determines niche segregation and thus coexistence within communities (i.e. at the alpha-scale). However, the action of disturbance, creating heterogeneous environments and suppressing potential dominants, may also be important for biodiversity maintenance.
2. Hypothesis: subordinate species exhibit primarily opportunistic (ruderal) survival strategies, with increasing disturbance intensity constraining dominant species - favouring opportunistic strategies and thus functional and species diversity.
3. The diversity, character and frequency of strategies in an alpine sedge-dominated vascular plant community were quantified in situ using CSR (competitor, stress-tolerator, ruderal) classification, and compared with a pasture in the same alpine vegetation belt (i.e. with additional disturbance). Adaptive trends were confirmed by independent multivariate analysis [detrended correspondence analysis (DCA) and non-metric multidimensional scaling (NMDS)].
4. The extremely stress-tolerant sedge Carex curvula (C : S : R = 17.2 : 72.9 : 9.9%) dominated the relatively undisturbed community (frequency = 52%), with 32 subordinates (typically < 5%) exhibiting a functional spectrum encompassing stress tolerance to ruderalism, but not competitive strategies. With grazing, the community exhibited weaker co-dominance by five species, greater biodiversity (76 species) and greater functional diversity, characterized by larger numbers of ruderals and some competitive-ruderals. The principal variation in both DCA1 and NMDS1 for both communities directly reflected CSR strategy spectra, confirmed by Spearman's correlation.
5. Dominance by stress-tolerators and restricted functional diversity demonstrates habitat-level (beta-scale) functional convergence in response to stress. A spectrum of S to R strategies demonstrates alpha-scale functional divergence in response to differential stress and disturbance. Grazing suppresses potentially dominant species and favours diversity, with the additional presence of competitive-ruderals suggestive of a more intricate niche topology including more relaxed abiotic opportunities.
6. Natural communities are not necessarily structured according to the rules of resource competition models, as these fail to account for disturbance and facilitation processes
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