Syntaxonomy and ecology of plant communities of the Carici rupestris-Kobresietea bellardii in the western carpathians

We present a syntaxonomic account of the communities of the alliances of Oxytropido-Elynion Br.-Bl. 1949 and Festucion versicoloris Krajina 1933 from Western Carpathians. Both alliances comprise naked-rush, cushion form and dwarf-shrub heath communities typical of wind-exposed habitats occurring at the highest altitudes of the Tatra Mts. They represent a relic vegetation of the cold stages of the Pleistocene (probably Late Glacial Maximum) and they can be classified within the class of Carici rupestris-Kobresietea bellardii Ohba 1974. A set of relevés was subject to numerical-classification analysis. Floristics and ecology of the communities were characterised and the relationships to similar syntaxa were discussed. The Oxytropido-Elynion is restricted to the extreme ridge positions in the highest altitudes of the Belianske Tatry Mts. Five associations were distinguished, such as the Pyrolo carpaticae-Salicetum reticulatae, the Festuco versicoloris-Oreochloetum distichae, the Festucetum versicoloris, the Oxytropido carpaticae-Elynetum myosuroides and the Drabo siliquosae-Festucetum versicoloris. The Festucion versicoloris is limited to the mylonite zone of the alpine and subnival belt of the Vysoké Tatry and Západné Tatry Mts (and found as rare in the Nízke Tatry Mts). The stands of these communities prefer terraces of steep rocky faces and cliffs and stabilised small-grained screes below the cliffs. Within this alliance, three associations were described, including the Agrostio alpinae-Festucetum versicoloris, the Silenetum acaulis and the Salicetum kitaibelianae.     

Patterns in the production of antiherbivore chemical defenses in plant communities

The diversity of chemical identity and mode of action of toxic substances present in plants is suggested to be partially the result of generalist herbivore grazing pressure, while convergence in digestibility-reducing substances and their method of function is due primarily to specialist herbivore. Analysis of alkaloid patterns from herbaceous and woody perennials show that most species differ in their alkaloid composition and many sympatric species and subspecies show unique patterns. The high degree of functional convergence in digestibility-reducing substances is supported by convergent patterns in tannins among woody perennials.     

Helminth communities in Audouin's gulls, Larus audouinii from Chafarinas Islands (western Mediterranean)

A survey of intestinal helminth communities of Audouin's gulls Larus audouinii, from their breeding colonies in Chafarinas Islands, western Mediterranean, Spain was conducted to determine the abundance and species diversity of intestinal parasites of these birds. The sample of 58 gulls harbored intestinal helminth infracommunities composed of species that are gull generalists, including the digeneans Cardiocephalus longicollis, Knipowitschiatrema nicolai, Condylocotyla pilodora, and Aporchis massiliensis, and the cestode Tetrabothrius cylindraceus. Two nematodes are waterfowl generalists (Cosmocephalus obvelatus and Paracuaria adunca), whereas the digenean Acanthotrema armata is an Audouin's gull specialist. The relative high values of species richness and diversity of the helminth infracommunities are comparable to those of other gulls (Larus philadelphia, Larus canus), probably reflecting the specialized, nonselective fish diet of L. audouinii.     

Plant volatiles inhibit restoration of plant species communities in dry grassland

Benefits from livestock grazing have declined in regions where vegetation has been degraded by overgrazing. The vegetation can be restored by excluding livestock for a period, but it takes longer in drier regions. Here we propose a possible mechanism for delays in the recovery of poor vegetation for livestock grazing in dry grassland, introducing a case in Mongolia where steppe vegetation dominated by Stipa krylovii, a palatable grass, can become dominated by Artemisia adamsii, an unpalatable forb, when the grassland is overgrazed. Our long-term field experiment shows that the exclusion of livestock has not enhanced the recovery of palatable species in 6 years, indicating that A. adamsii is a strong competitor in the plant community. To understand why livestock exclusion is ineffective, we examined the ecological significance of volatile organic compounds (VOCs) released by A. adamsii. In ex situ experiments, the VOCs promoted photosynthesis of S. krylovii with enhanced stomatal conductance, and S. krylovii grew faster and consumed more water when exposed to the VOCs even with water deficiency. These findings imply that S. krylovii would be more likely to face severe drought before the next rain falls. We therefore conclude that plant volatiles may reduce the resilience of overgrazed vegetation in arid environments.     

Survey of biomass and net production of higher plant communities in fishponds

After a brief account of both past and present fishpond management and of its impact on the fishpond vegetation of higher plants, a survey is given of the biomass and total net production in various types of communities constituting this vegetation. Relatively stable and unstable communities are distinguished and further differentiated by the dominant plant life-forms. The biomass and production data are highly variable, depending on actual conditions in the fishpond habitats, but the maximum recorded values of annual net production (in terms of dry matter produced per year) appear to decrease in the following order: the communities dominated by ochthohydrophytes (over 3kg.m^?2)-hydroochthophytes and euochthophytes (about 2kg.m^?2)-pleustophytes and aerohydatophytes (upto 1kg.m^?2)-euhydatophytes (upto 0.5kg.m^?2). The original data were gathered in Czechoslovakia and the conclusions apply to fishponds in Central Europe.     

Red Queen: from populations to taxa and communities

Biotic interactions via the struggle for control of energy and the interactive effects of biota with their physical environment characterize Van Valen's Red Queen (VRQ). Here, we review new evidence for and against a VRQ view of the world from studies of increasing temporal and spatial scales. Interactions among biota and with the physical environment are important for generating and maintaining diversity on diverse timescales, but detailed mechanisms remain poorly understood. We recommend directly estimating the effect of biota and the physical environment on ecological and evolutionary processes. Promising approaches for elucidating VRQ include using mathematical modelling, controlled experimental systems, sampling and processes-oriented approaches for analysing data from natural systems, while paying extra attention to biotic interactions discernable from the fossil record.     

Plant traits shape the effects of tidal flooding on soil and plant communities in saltmarshes

Saltmarshes are recognised worldwide to be among the most complex ecosystems, where several environmental factors concur to sustain their fragile functioning. Among them, soil–plant interactions are pivotal but often overlooked. The aim of this work was to use a structural equation modelling (SEM) approach to get new insight into soil–plant interactions, focusing on the effect of plant traits and abundance on soil, and test the effect of soil and/or plants on the entire community, monitoring changes in plant richness. The target halophytes Limonium narbonense and Sarcocornia fruticosa were sampled in the Marano and Grado lagoon (northern Adriatic Sea). Basal leaves of L. narbonense and green shoots of S. fruticosa were used to estimate plant growth, while the abundance of both species was used as a proxy of species competition. SEM was applied to test relationships between predictors and response variables in a single causal network. The flooding period (hydroperiod) negatively affected plant growth and soil properties, whereas plants decreased the intensity of soil reduction. Flooding did not directly affect species abundance or diversity, whose changes were instead driven by plant traits. The direct relationships between plant traits and species richness highlighted that species competition could be even more important than environmental stresses in defining plant diversity and zonation.     

中条山中段木本植物群落植物种多样性分析

采用样方法取样,依据重要值指标运用双向指示种分析(TWINSPAN)法,将山西中条山中段植被群系分成16个群丛。应用丰富度指数（R₁、R₂）、Simpson指数（λ）,Shannon-Weiner指数(H′)和均匀度指数(E₁、E₅)研究了16个群丛的植物种多样性。结果表明：群系植物种多样性指数的大小受立地生境和人为活动的综合影响;森林群落的植物种多样性指数明显高于灌丛群落;群落植物种多样性在空间上的差异不仅决定于物种丰富度指数,更与各物种间的均匀度指数密切相关;进而影响不同层次的物种多样性对群落总体物种多样性的贡献。