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The number of genetically distinct individuals within a community is a key component of biodiversity and yet its impact at different trophic levels, especially upon the diversity of functionally important soil microorganisms is poorly understood. Here, we test the hypothesis that plant communities that are genetically impoverished will support fewer species of root-associated fungi. We used established grassland mesocosms comprising non-sterile natural soil supporting defined communities of 11 clonally-propagated plant species. Half of the mesocosms contained one genotype per species and half 16 genotypes per species. After 8 years growth, we sampled roots from the mesocosms and measured root-associated fungal richness and diversity using terminal restriction fragment length polymorphism (T-RFLP). Contrary to our hypothesis, we found that the roots of genetically impoverished communities contained more species of fungi and had greater diversity compared to genetically rich communities. Analysis of the plant species composition of the mesocosm communities indicated that genotypic diversity affects root-fungal diversity indirectly through its influence upon plant species diversity. Our findings highlight the need to include feedbacks with plant intraspecific diversity into existing models describing the maintenance of soil biodiversity. [ABSTRACT FROM AUTHOR]

1. Limestone grasslands are among the most floristically rich ecosystems in northern Europe and have recently been shown to sustain ecosystem functioning under conditions of heavy nitrogen (N) deposition. Here we report a long-term mesocosm experiment, designed to measure the importance of major component plants and community composition in providing ecosystem services (in particular preventing leaching of inorganic N). 2. A number of important steps were taken in the experimental design to increase conformity of the experimental communities to real limestone pasture, including using natural soils, plant cuttings of limestone grassland provenance and simulated management. Furthermore, communities were allowed to establish for 8 years before measurements were made. 3. Leaching of and were found to differ by up to a considerable two orders of magnitude according to functional group composition, with sedges and forbs leaching the most. Grass communities and communities containing all three functional groups (grasses, sedges and forbs) leached similarly low amounts of and . 4. Levels of soil and followed a similar pattern of inter-community differences to leaching, while vegetation biomass and vegetation N stocks were very similar between communities consisting of only grasses, only sedges and the most species rich community (4 grasses + 4 sedges + 4 forbs). 5. Perennial grasses appeared to play the key role in inorganic N retention, with communities consisting of these plants having equally low leaching as more species rich communities. Indeed, most ecosystem services were performed comparatively well by grass communities as by the most species rich community. 6. No overall effects on provision of services resulted from mixing functional groups or increasing the number of species representing each functional group. 7. Synthesis. This work shows that more than order-of-magnitude differences in provision of ecosystem services can occur between species that coexist naturally in ancient limestone pasture. However, despite these large differences, because of the key role played by grasses, expected shifts in community composition anticipated as a result of N pollution may not impair the capacity of these systems to provide ecosystems services. [ABSTRACT FROM AUTHOR]

The article discusses a study that used 10-year-old model plant communities to investigate how the diversity and composition of plant communities influence soil respiration rates. The results showed that soil respiration was driven by plant community composition. The effect of biodiversity at the three levels tested was not significant. Soil respiration is not also affected by above-ground biomass and root density.

Climate shifts over this century are widely expected to alter the structure and functioning of temperate plant communities. How- ever, long-term climate experiments in natural vegetation are rare and largely confined to systems with the capacity for rapid com- positional change. In unproductive, grazed grassland at Buxton in northern England (U.K.), one of the longest running experimental manipulations of temperature and rainfall reveals vegetation highly resistant to climate shifts maintained over 13 yr. Here we document this resistance in the form of: (i) constancy in the relative abundance of growth forms and maintained dominance by long- lived, slow-growing grasses, sedges, and small forbs; (ii) immediate but minor shifts in the abundance of several species that have remained stable over the course of the experiment; (iii) no change in productivity in response to climate treatments with the exception of reduction from chronic summer drought; and (iv) only minor species losses in response to drought and winter heating. Overall, compositional changes induced by 13-yr exposure to climate regime change were less than short-term fluctuations in species abundances driven by interannual climate fluctuations. The lack of progressive compositional change, coupled with the long-term historical persistence of unproductive grasslands in northern En- gland, suggests the community at Buxton possesses a stabilizing capacity that leads té long-term persistence of dominant species. Unproductive ecosystems provide a refuge for many threatened plants and animals and perform a diversity of ecosystem services. Our results support the view that changing land use and overexploitation rather than climate change perse constitute the primary threats to these fragile ecosystems. [ABSTRACT FROM AUTHOR]

1. A recent experiment varied the genetic diversity of model grassland communities under standardized soil and management conditions and at constant initial species diversity. After 5 years’ growth, genetically diverse communities retained more species diversity and became more similar in species composition than genetically impoverished communities. 2. Here we present the results of further investigation within this experimental system. We proposed that two mechanisms – the first invoking genetically determined and constant differences in plant phenotypes and the second invoking genotype–environment interactions – could each underpin these results. This mechanistic framework was used as a tool to interpret our findings. 3. We used inter-simple sequence repeat (ISSR) DNA markers to confirm which of the individuals of six study species initially included in the model communities were unique genotypes. We then used the molecular markers to assess the survival and abundance of each genotype at the end of the 5-year experimental period. 4. The DNA marker data were used to create, for the first time, a genotype abundance hierarchy describing the structure of a community at the level of genotypes. This abundance hierarchy revealed wide variation in the abundance of genotypes within species, and large overlaps in the performance of the genotypes of different species. 5. Each genotype achieved a consistent level of abundance within genetically diverse communities, which differed from that attained by other genotypes of the same species. The abundance hierarchy of genotypes within species also showed consistency across communities differing in their initial level of genetic diversity, such that species abundance in genetically impoverished communities could be predicted, in part, by genotypic identity. 6. Three species (including two canopy-dominants) experienced shifts in their community-level genotype abundance hierarchies that were consistent with an increased influence of genotype–environment interactions in genetically impoverished communities. 7. Our results indicate that under relatively constant environmental conditions the species abundance structure of plant communities can in part be predicted from the genotypic composition of their component populations. Genotype–environment interactions also appear to shape the structure of communities under such conditions, although further experiments are needed to clarify the magnitude and mechanism of these effects. [ABSTRACT FROM AUTHOR]

1 It is suggested that arguments concerning the nature of primary plant strategies could have been resolved more rapidly by reference to older literature relating to the behaviour of solutes in the rhizosphere and by more active programmes of plant trait screening. 2 The critique of CSR theory in Craine (2005 ) is rejected largely on the basis that it misunderstands the role of fundamental and proximal controls on vegetation composition ( sensu Welden & Slauson 1986 ). 3 The ‘way forward’ advocated in Craine (2005 ) is flawed in its exclusive reliance on competition experiments. Recent progress in community and ecosystem ecology is strongly related to an increasing recognition of the declining importance of competition in unproductive or heavily disturbed environments. [ABSTRACT FROM AUTHOR]

Presents a forum on biodiversity, ecosystem function and plant traits in mature and immature plant communities. Evidence of a positive relationship between vascular plant diversity and biomass production; Exclusion of the natural sources of variation and create synthesized plant assemblages that vary only in artificially imposed levels of species richness; Monitor of the species richness of vascular plants.

Presents information on a study about the effects of invertebrate herbivory on plant community composition and on the rate of secondary succession, at differing levels of soil fertility, using outdoor microcosms. Methods and materials used in the study; Results; Discussion.

The article presents a study about the grassland vegetation of the Sheffield region. This study investigated the ecology of flowering plants in the Sheffield region in Britain which makes an excellent center for study for its location between highland and lowland areas of the country offering access to the climatic and biological expressions in each zone. Geological strata, altitude and land-use were important factors for this experiment. Diverse and intense biotic pressures were also recorded. Environmental variations and topography also helped in establishing the information needed for this study.

The article focuses on the number of species contributing to the vegetation of an upland grazing on Ffridd, Ddu, Aber in Caernarvonshire, Wales. The study uses an ordination approach technique in the analysis of some plant communities present on the upland grassland of Ffridd Ddu, Caernarvonshire, while the performance of individual plant species has been related to single axis of floristic variation which correlates well with similar single axis variation in some edaphic factors. Moreover, the particular technique of ordination used is described in detail and placed on the potential value of this approach in ecological analysis.