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One of the unifying goals of ecology is understanding the mechanisms that drive ecological patterns. For any particular observed pattern, ecologists have proposed varied mechanistic models. However, in spite of their differences, all of these mechanistic models rely on either abiotic conditions or biotic conditions, our "ecological first principles". These major components underlie all of the major mechanistic explanations for patterns of diversity like the latitudinal gradient in diversity, the maintenance of diversity, and the (often positive) biodiversity-ecosystem functioning relationship. These components and their interactions alter the dynamics of plant populations, which ultimately determine local coexistence at the community level, and functioning at the ecosystem level. We present a review, starting from ecological first principles of the ways in which ecosystem functioning may be linked to local coexistence in plant communities via mutual effects on and reactions to the abiotic and biotic conditions in which they are imbedded. [ABSTRACT FROM AUTHOR]

Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape. [ABSTRACT FROM AUTHOR]

The importance of competition has been defined as the impact or role of competition relative to the total impact of the environment, and the intensity of competition is its absolute impact. Understanding the distinction has been proposed as key in reconciling long-running ecological debates., An index of competition importance, Cimp, has been used in a number of recent studies. Rees, Childs & Freckleton (2012) present a strong attack on the competition index Cimp (and the associated interaction index Iimp) and question the underlying rationale for the concept of competition importance. We assess their critique and challenge it in a number of areas., Rees et al. conflate criticism of the index Cimp with criticism of the concept of competition importance. Their approach to assessing the properties of Cimp (and Iimp), including the use of target plant success in the absence of neighbours ( PNC) as a measure of environmental severity, is biased towards demonstrating a simple linear relationship between severity and Cimp, and supporting the argument that there is no need for separate measurements of importance., We consider the proposal by Rees et al. for the use of variance partitioning to assess importance. Although providing a measure of the relative role of competition, it is unable to assess the shape of the importance-severity relationship, something central to testing important ecological theories such as those of Grime (1979) or Bertness & Callaway (1994). We discuss alternative approaches which might address this question., Synthesis. Responding to Rees et al. has been beneficial in clarifying points of difference between our approaches, and the need to visualize the shape of the importance-severity relationship. From this response we draw three broad conclusions. We need: (i) metrics of environmental severity that are independent of the success of target species; (ii) analytical approaches that avoid the statistical problems associated with ratios whilst enabling us to assess the shape of the severity-importance relationship; (iii) new data to assess the generality of proposed relationships. Studies incorporating these elements will take forward our understanding of the role of competition in plant communities. [ABSTRACT FROM AUTHOR]

1. Projection matrices have become the dominant modelling approach in plant demography because they (i) are relatively easy to formulate, (ii) compile complex data in a structured and analytically tractable manner, (iii) provide numerous parameters with direct biological meaning, (iv) allow the investigator to address broad or specific, experimental and/or theoretical, ecological and evolutionary questions, and (v) produce uniform outputs, enabling direct comparisons between the results of different studies. 2. The last decade has witnessed major advancements in this field that have brought demographic models much closer to the real world, in particular in the analysis of effects of spatial and temporal environmental variation on populations. The present Special Feature contributes to that progress with novel methodologies and applications on Integral Projection Models, stochastic Life Table Response Experiment analyses, stochastic elasticities, transient dynamics and phylogenetic analyses. 3. Synthesis. Environmental stochasticity is an integral part of ecosystems, and plant populations exhibit a tremendous array of demographic strategies to deal with its effects. The analytical challenge of understanding how populations avoid, tolerate or depend on stochasticity is finally overcome with the new matrix approaches. The tools are now available to interpret the effects of changes in temporal and spatial variation on plant populations. [ABSTRACT FROM AUTHOR]

1. An increasing body of evidence suggests that within-species diversity plays an important role for community and ecosystem functioning, alters complex trophic interactions and affects patterns of species diversity and coexistence. Nonetheless, we lack a good understanding of how genotypic trait variation translates into shifts in the relative abundance of genotypes within populations. 2. In this study, we show that genotypic selection strongly alters dominance relationships among genotypes over a period of 5 years. This resulted in remarkably consistent changes in the proportional representation of genotypes, and in a concomitant decline of diversity and evenness in our experimental populations. 3. High growth rates and the production of large offspring were positively associated with genotypic performance. Vegetative abundances of genotypes translated monotonically into flowering frequencies. 4. Synthesis. We conclude that genotypic selection markedly affects patterns of diversity and consistently alters genotypic abundance and mean trait distributions in plant populations over a relatively short period of time. [ABSTRACT FROM AUTHOR]

For effective management of endangered species it is pivotal to understand why a species is endangered and which key life cycle components are involved in its response to environmental changes. Our objective was to investigate the response of rosettes of the redlisted clonal herb Cirsium dissectum to anthropogenic nutrient enrichment, which threatens its populations, and the consequences of these responses for its population dynamics. We constructed matrix population models with demographic data from three populations and four annual transitions and we decomposed the spatiotemporal variation in projected population growth rates into contributions from life cycle components. These patterns were compared with below-ground rosette dynamics in different fields, and with the below- and above-ground rosette dynamics in a garden experiment with nutrient enrichment and competing grasses. The decomposition analysis revealed that increased clonal rosette formation and decreased rosette survival were driving the spatial variation in the population growth rate. Excavating the below-ground rhizome network revealed a higher rosette turn-over in experimentally fertilized garden plots, which not only resulted in increased plot-level extinction, but also in increased spread of the clonal offspring. This supported the observed trend among field populations: rosette formation trades off with rosette survival. Surviving seedlings were only found in areas where the topsoil had been removed. The endangered C. dissectum is vulnerable when its habitat becomes more productive, because this species does not have the necessary capability to build up biomass. Small-scale disturbances such as created by sod-cutting or trampling cattle are essential for seedling establishment and necessary to render the explorative strategy of rhizomatous clonal spread successful. [ABSTRACT FROM AUTHOR]

1 An increasing number of studies have shown that plants produce more root mass when sharing rooting space with an intraspecific neighbour as compared with plants growing alone. This so-called self/non-self discrimination has been suggested as a mechanism by which plants may prevent wasteful competition with their own roots and enhance their competitive ability for nutrients with roots of neighbouring plants. The overproduction of root biomass is said to result in a ‘tragedy of the commons’, because it appears to occur at the expense of reproductive biomass. 2 Studies on self/non-self root discrimination have commonly used a split-root design to distinguish self from non-self competition, while keeping the total amount of nutrients available per plant the same. This design has recently been criticized because the rooting volume differs between treatments. 3 Here, we use three general hypotheses to explain the published results without invoking the mechanism of self/non-self discrimination. The hypotheses propose that differences in root mass are due to differences in rooting volume, and differences in nutrient availability determine whole plant growth. More root mass without more growth results in less reproductive biomass. 4 A reanalysis of the results of root self/non-self discrimination confirms these hypotheses. Root overproduction in the presence of another plant, as found in nearly all studies, is consistent with effects of a larger soil volume available to these plants as compared with plants growing alone. Under the same total nutrient availability, total plant weight was the same or higher when more roots were produced. Inevitably, a larger root production with the same total biomass implies that less reproductive biomass is produced. 5 Although our analysis can explain most of the results of the split-root experiments, we cannot rule out the possibility that self/non-self root discrimination did take place. We discuss a limited set of experiments for which volume effects cannot explain the results, suggesting, in fact, that direct self/non-self root interactions have operated. We suggest experimental designs that can demonstrate their ecological significance in the future. 6 We conclude that there is ample evidence that plants can sense the volume of available rooting space, and a limited number of studies on individual roots show that plant roots may sense the identity of neighbouring roots and respond accordingly. The significance of these responses for whole plant growth and reproduction in relation to well-known resource competition effects is yet largely unknown and in urgent need of further study. [ABSTRACT FROM AUTHOR]

Question: Does disturbance reduce competition intensity and thus favour weak competitors that are presumably less affected by disturbance than strong competitors? Methods: We used a single flooding event with increasing duration to simulate disturbance with increasing intensity. Six flood-plain grass species, typical of different flood regimes were grown in monocultures and in an additive species mixture. Flooding took place early in the first growing season and changes were monitored until the end of the second growing season. Results: Longer flooding durations initially decreased competition, but only a single species (Agrostis) increased its abundance in mixtures after flooding. The two weakest competitors in our selection (Poa trivialis and Elytrigia repens) failed to benefit them flooding because direct losses from flooding exceeded gains from reduced competition. Accordingly, we found no trade-off between flooding tolerance and competitive ability indicating that floods affect strong and weak competitors equally, although some species tolerated floods better than others. Conclusions: Since competition is only temporarily weakened after disturbance, increased competitive ability relative to other species may provide a more effective strategy for persistence in flood-disturbed sites. Above-ground runners seem an important prerequisite for enhanced competitive ability of clonal species in flood-disturbed sites. [ABSTRACT FROM AUTHOR]

In a garden experiment we investigated the response to continuous removal of either flower buds or rosette buds in three perennial grassland species ( Hypochaeris radicata, Succisa pratensis and Centaurea jacea), which differ in longevity and flowering type. We distinguished two possible responses: compensation for lost buds by making more buds of the same type, and switching towards development of other life history functions. Both responses were demonstrated in our experiment, but bud removal had significantly different effects in each of the three species. The degree of compensation and the expression of trade-offs between life history functions differed markedly between species and seem related to longevity and developmental constraints. With respect to switching, our results suggest costs of reproduction and a trade-off between life history functions, at least for Hypochaeris and Succisa. For these species weight of new rosettes increased when resource allocation to flowering was inhibited. In Hypochaeris, we see that both compensation for lost flower buds and switching from lost rosette buds increased production of flower buds, underscoring the pivotal role of sexual reproduction in this short-lived species. The most prominent response seen in Centaurea is compensation for lost rosette buds, indicating that this long-lived species with monocarpic rosettes relies on rosette formation. Although Succisa does respond to bud removal, time is an important constraint in this species with long-lived rosettes and preformed flowering stalks. Trade-offs in Succisa seem to operate at a larger time scale, requiring long-lasting experiments to reveal them. We conclude that the response of these species to inflicted damage is likely to be linked to their longevity and developmental constraints. [ABSTRACT FROM AUTHOR]

The worldwide leaf economic spectrum (WLES) is a strikingly consistent pattern of correlations among leaf traits. Although the WLES effectively summarizes variation in plant ecological strategies, little is known about its evolution. We reviewed estimates of natural selection and genetic variation for leaf traits to test whether the evolution of the WLES was limited by selection against unfit trait combinations or by genetic constraints. There was significant selection for leaf traits on both ends of the WLES spectrum, as well as significant genetic variation for these traits. In addition, genetic correlations between WLES traits were variable in strength and direction. These data suggest that genetic constraints have had a smaller role than selection in the evolution of the WLES. [ABSTRACT FROM AUTHOR]