Competitor, Stress-tolerator, Ruderal Research Articles

Plant water use related to leaf traits and CSR strategies of 10 common European green roof species

The vegetation layer contributes to multiple functions of green roofs including their hydrological function as plants remove water from substrates between rainfall events through evapotranspiration, restoring the green roofs storage capacity for rainfall retention. While individual traits have been related to water use strategies of green roof plants, these traits are inconsistent, suggesting the importance of trait combinations which may be reflected in CSR (competitor, stress tolerator, ruderal) strategies. Therefore, relating plant water use to leaf traits and CSR strategies could help facilitate green roof plant selection into new geographical regions where green roof technology is developing. For example, in high latitude northern European regions with long daylight during the growing season. Growth (shoot biomass, relative growth rate and leaf area), leaf traits (leaf dry matter content, specific leaf area and succulence) and CSR strategies were determined of 10 common European green roof plants and related to their water use under well-watered (WW) and water-deficit (WD) conditions. All three succulent species included in the experiment showed mostly stress tolerant traits and their water loss was less than the bare unplanted substrate, likely due to mulching of the substrate surface. Plants with greater water use under WW conditions had more ruderal and competitive strategies, and greater leaf area and shoot biomass, than species with lower WW water use. However, the four species with the highest water use under WW conditions were able to downregulate their water use under WD, indicating that they could both retain rainfall and survive periods of water limitations. This study indicates that, for optimal stormwater retention, green roof plant selection in high latitude regions like northern Europe, should focus on selecting non-succulent plants with predominantly competitive or ruderal strategies to make the most of the long daylight during the short growing season.

Do the same genus plants have consistent adaptation strategies in cold-wet environments? A case study of leaf suitability of 19 Syringa species

Carbon cost-benefit theory indicates that leaf photosynthesis benefit and structure cost have scaling relationship. However, this relationship has not been tested in the perennial cold-wet regions. Shorter growing seasons in cold-wet climates severely limit plant growth, making it important to explore the light interception and economic strategies for the survival of plants in this region. We measured leaf area (LA), leaf fresh mass (LFM) and leaf dry mass (LDM) of 19 Syringa species around Xi’ning city to explore leaf scaling relationship and adaptation strategies. Our results showed that LA, LFM and LDM varied among species, with the coefficients of variation (CV) among species being 64.61%, 76.43% and 65.94%, respectively. For all species, LDM with LFM and LA showed isometric growth, and only LA and LFM followed allometric growth with a scaling exponent greater than 1 (p < 0.05). Linear correlation indicated that, with the increase of LA, the scaling constant tended diminishingly. Ultimately, according to the CSR (Competitor - Stress tolerator - Ruderal) strategy division, nineteen plants were divided into strategy CS (competitor & stress tolerator) and strategy S/CS (stress tolerator/competitor & stress tolerator). What’s more, LA, LFM and LDM of CS strategy plant were all significantly greater than S/CS strategy. In conclusion, plants in cold-wet habitats tend to have a more conservative economic strategies; and combined with the CSR theory, these plants are more competitive and stress tolerators. More attention should be paid to the effects of harsh environments on plant life history strategies.

The leaf anatomical trade-offs associated with plant ecological strategy variation

Plant functioning depends on variation in resource economics traits (acquisition vs. conservation) and the size of plants and their parts (the ‘global spectrum of plant form and function’). The anatomical basis of single traits (e.g., leaf mass per area; LMA) is generally understood, but little is known regarding the relationship between anatomical trade-offs and ecological strategies (representing integrated suites of traits). We hypothesised correlations between the relative extent of leaf tissue types and Grime’s Competitor Stress-tolerator Ruderal (CSR) strategies, principally a trade-off between structural (mechanical/fibro-vascular) vs. photosynthetic (chlorenchyma and intercellular airspace; ICAS) tissues, for ecologically contrasting herbaceous angiosperms in northern Italy. Specifically, that in the lamina portion, the trade-off represents the economics spectrum (S-R selection), but in the midvein portion, it reflects the mechanical constraints inherent to supporting large leaves (i.e., varies with C-selection). We used microscopy and image analysis to determine the relative cross-sectional area of tissues from transverse leaf sections (lamina and midvein portions) of angiosperms of contrasting CSR strategies. Principal components analysis (PCA) determined that the main trade-off (PCA1) was between mechanical/fibro-vascular tissues vs. ICAS/epidermis/chlorenchyma, but that this was associated with the economics spectrum (R- to S-selection) in the lamina, and with size (C-selection) for the midvein. A secondary trade-off in both lamina and midvein portions involved ICAS (i.e., the internal gas diffusion pathway) vs. chlorenchyma/epidermis (light capture), associated with S- to R-selection, respectively. Our results confirm the expectation that ecological strategy variation has a basis in underlying trade-offs between tissues with contrasting metabolic/architectural (i.e., economics/size-related) roles.

Trait-trait relationships and tradeoffs vary with genome size in prokaryotes.

We report genomic traits that have been associated with the life history of prokaryotes and highlight conflicting findings concerning earlier observed trait correlations and tradeoffs. In order to address possible explanations for these contradictions we examined trait-trait variations of 11 genomic traits from ~18,000 sequenced genomes. The studied trait-trait variations suggested: (i) the predominance of two resistance and resilience-related orthogonal axes and (ii) at least in free living species with large effective population sizes whose evolution is little affected by genetic drift an overlap between a resilience axis and an oligotrophic-copiotrophic axis. These findings imply that resistance associated traits of prokaryotes are globally decoupled from resilience related traits and in the case of free-living communities also from traits associated with resource availability. However, further inspection of pairwise scatterplots showed that resistance and resilience traits tended to be positively related for genomes up to roughly five million base pairs and negatively for larger genomes. Genome size distributions differ across habitats and our findings therefore point to habitat dependent tradeoffs between resistance and resilience. This in turn may preclude a globally consistent assignment of prokaryote genomic traits to the competitor - stress-tolerator - ruderal (CSR) schema that sorts species depending on their location along disturbance and productivity gradients into three ecological strategies and may serve as an explanation for conflicting findings from earlier studies. All reviewed genomic traits featured significant phylogenetic signals and we propose that our trait table can be applied to extrapolate genomic traits from taxonomic marker genes. This will enable to empirically evaluate the assembly of these genomic traits in prokaryotic communities from different habitats and under different productivity and disturbance scenarios as predicted via the resistance-resilience framework formulated here.

Mega-fire in redwood tanoak forest reduces bacterial and fungal richness and selects for pyrophilous taxa that are phylogenetically conserved.

Mega-fires of unprecedented size, intensity and socio-economic impacts have surged globally due to climate change, fire suppression and development. Soil microbiomes are critical for post-fire plant regeneration and nutrient cycling, yet how mega-fires impact the soil microbiome remains unclear. We had a serendipitous opportunity to obtain pre- and post-fire soils from the same sampling locations after the 2016 Soberanes mega-fire burned with high severity throughout several of our established redwood-tanoak plots. This makes our study the first to examine microbial fire response in redwood-tanoak forests. We re-sampled soils immediately post-fire from two burned plots and one unburned plot to elucidate the effect of mega-fire on soil microbiomes. We used Illumina MiSeq sequencing of 16S and ITS1sequences to determine that bacterial and fungal richness were reduced by 38%-70% in burned plots, with richness unchanged in the unburned plot. Fire altered composition by 27% for bacteria and 24% for fungi, whereas the unburned plots experienced no change in fungal and negligible change in bacterial composition. Pyrophilous taxa that responded positively to fire were phylogenetically conserved, suggesting shared evolutionary traits. For bacteria, fire selected for increased Firmicutes and Actinobacteria. For fungi, fire selected for the Ascomycota classes Pezizomycetes and Eurotiomycetes and for a Basidiomycota class of heat-resistant Geminibasidiomycete yeasts. We build from Grime's competitor-stress tolerator-ruderal (C-S-R) framework and its recent microbial applications to show how our results might fit into a trait-based conceptual model to help predict generalizable microbial responses to fire.

Species Diversity Regulates Ecological Strategy Spectra of Forest Vegetation Across Different Climatic Zones.

Ecological strategy is the tactics employed by species in adapting to abiotic and biotic conditions. The ecological strategy spectrum is defined as the relative proportion of species in different ecological strategy types within a community. Determinants of ecological strategy spectrum of plant community explored by most previous studies are about abiotic factors. Yet, the roles of biotic factors in driving variations of ecological strategy spectra of forest communities across different geographic regions remains unknown. In this study, we established 200 0.04-ha forest dynamics plots (FDPs) and measured three-leaf functional traits of tree and shrub species in four forest vegetation types across four climatic zones. Based on Grime’s competitor, stress-tolerator, ruderal (CSR) triangular framework, and the StrateFy method, we categorized species into four ecological strategy groups (i.e., C-, S-, Int-, and R-groups) and related the ecological spectra of the forests to three species diversity indices [i.e., species richness, Shannon-Wiener index, and stem density (stem abundance)]. Linear regression, redundancy analysis, and variance partition analysis were utilized for assessing the roles of species diversity in regulating ecological strategy spectra of forest communities across different climatic zones. We found that the proportion of species in the C- and Int-groups increased, while the proportion of species in the S-group decreased, with the increase of three indices of species diversity. Among the three species diversity indices, stem abundance played the most important role in driving variations in ecological strategy spectra of forests across different climatic zones. Our finding highlights the necessity of accounting for biotic factors, especially stem abundance, in modeling or predicting the geographical distributions of plant species with varied ecological adaptation strategies to future environmental changes.

Root and Rhizosphere Processes under Drought: Digging Deeper to Enhance Ecosystem Resilience

Root and Rhizosphere Processes under Drought: Digging Deeper to Enhance Ecosystem Resilience

竞争-耐胁迫-杂草型植物对策理论及其应用研究进展

竞争-耐胁迫-杂草型植物（CSR）对策理论主要研究植物对环境胁迫和干扰的适应性特化。从功能生态学角度讲，CSR理论是通过解释各种功能性状协同变异的主导维度来反映植物的生态对策。而物种所采取的生态对策将决定其在群落中的生态位，并最终会影响生态系统过程与功能。自1974年Grime首次提出CSR对策的概念以来，CSR对策思想就受到了生态学家很大的关注，经过近半个世纪的发展，目前已经形成了比较完整的理论和研究方法体系。试图在回顾CSR理论及其研究方法发展的基础上，阐述其基本内涵，并重点从功能性状变异空间、植物适应性、群落过程和生态系统特性等4个方面概述CSR理论及其分析模型的验证及应用，梳理其最新研究进展。CSR理论已经得到了很多研究的广泛验证并应用于多种尺度上的植物生态学研究，但仍有一些方面值得进一步发展完善，如第四区缺失问题、功能性状变异主轴以外的变异、CSR对策与功能性状种内变异和谱系关系的联系等方面需要深入研究。;Competitor, stress-tolerator, ruderal (CSR) theory, regarded as one of the best developed plant ecological strategy schemes, mainly studies the adaptive specialisation that plants evolve to achieve fitness in response to natural selection pressures, resulting in a triangular distribution of species optima along axes of habitat productivity and disturbance. From the perspective of functional ecology, the CSR theory reflects plant ecological strategies by explaining the principal functional spectra in the multidimensional trait space, that is, the world-wide economics spectrum and the size spectrum as fundamental gradients of plant evolution are major components of the CSR strategy variation. The ecological strategies adopted by plants then determine their ecological niche in the community and ultimately affect ecosystem processes and functions. Thus the CSR theory could not only be used as a framework for functionally classifying plants and predicting impacts of environmental change on vegetation, but also serves as a conceptual framework for investigating and interpreting community processes and ecosystem functioning. Since the concept of CSR strategies was first raised by Grime in 1974, the idea of CSR strategies has attracted much attention from ecologists, and the CSR theory has formed a relatively complete system of theories and research methods over the last half century. In this paper, we introduce the development and characteristics of the CSR theory and its methods to expound the core philosophy of the theory, review the verification and application of the CSR theory and its models by addressing the relevance of CSR strategies to functional trait variations, species adaptation, community processes and ecosystem properties, and summarize the advances in this theory. The CSR theory has been extensively validated by many studies and widely applied as a very useful analysis tool to plant ecology research on a variety of scales, but it needs further research, such as the missing fourth corner in the Grime's C-S-R triangular model, the rest functional variations beyond the principally functional trait spectra that are not explained by the CSR scheme, and the relationships between CSR strategies and the intraspecific trait variation and phylogenetic signal. Especially for the rest functional variations, the CSR theory does not preclude the existence of additional axes of variability subordinate to the principal functional spectra, nor that these may be certainly key to fitness and survival in specific cases. The CSR theory could be seen as a general adaptive strategy, since it is consistent with economics and size tradeoffs evident throughout the tree of life, hinting at overarching natural selection filters operating universally within the biosphere.

Quantifying the relationship linking the community-weighted means of plant traits and soil fertility.

Is it possible to generalize relationships between certain plant traits and soil fertility? In particular, are there quantitative relationships between community-weighted mean (CWM) trait values of leaf dry-matter content (LDMC), specific leaf area (SLA), plant height, and Grime's competitor-stress tolerator-ruderal (CSR) strategy scores and the generalized soil fertility, FG (i.e., the capacity of a soil to produce biomass when all nonsoil variables are held constant) that are generalizable across different species assemblages and geographical areas? We assessed FG in 21 sites in southern Quebec and 7 sites in southern France using a previously published method based on structural equationmodeling. We then determined the CWM values of LDMC, SLA, plant height, and CSR scores in the 21 Quebec sites to obtain quantitative relationships between FG and these CWM traits. Using these relationships, we independently tested the generality of the trait-fertility relationships using data from French sites. The relationships between FG and the CWM traits were nonlinear, but displayed the expected qualitative trends as reported in the literature. In particular, the S score and CWM LDMC decreased with increasing soil fertility, and the R score and CWM SLA increased. CWM traits were more strongly correlated to measures of FG (r2 up to 0.48) than to measures of other soil characteristics (r2 up to 0.17 for nitrogen flux). Importantly, the independently tested French FG -trait relationships showed no significant deviations from these quantitative relationships. Further investigation is necessary to confirm if the same trend applies to other regions and or ecosystems.

Effects of logging on the ecological strategy spectrum of a tropical montane rain forest

Ecological strategy is the various adaptation tactics of species to different living conditions, which can reflect their contrasting approaches to survival in varying habitats. The number and relative abundance of species in different types of ecological strategies actually forms an ecological strategy spectrum in a community. Logging is a widespread driver of forest degradation, severely influencing the composition of communities and the ecological strategy spectra in forest ecosystems. Understanding effects of logging on the ecological strategy composition of communities is vital to biodiversity conservation and efficient restoration of degraded forest ecosystems. Yet, the knowledge of how ecological strategies of different communities respond to varying types and intensities of disturbances in tropical forests are largely unknown. Here, by establishing forest dynamics plots (FDPs) in communities experienced increasing logging intensities (no logging (old-growth (OG)), selective logging (SL), and clear-cutting (CL) and measuring plant functional traits in a tropical montane rain forest, we compared the changes in ecological strategies of these stands by using Grime’s competitor, stress-tolerator, ruderal (CSR) scheme and by “StrateFy” ordination method based on measurements of three plant functional traits (Leaf area (LA), leaf dry matter content (LDMC), and specific leaf area (SLA)). Results showed that strategy number increased and ecological strategy spectra of communities changed significantly with increasing logging intensity: the proportion of S-selected strategies decreased while those of C- and R-selected strategies increased with increasing logging intensity. Community-weighted mean CSR (CWM-CSR) strategies of stands shifted from S to the C & R direction, i.e. CWM-C and CWM-R values increased and CWM-S values decreased with increasing logging intensity. Our findings suggest that logging intensity should be carefully controlled in harvesting planning, so that the recovery of species assemblages with multiple ecological strategies can be assured and the ecosystem services from these biodiverse forests can be provided sustainably.

Are endemic species necessarily ecological specialists? Functional variability and niche differentiation of two threatened Dianthus species in the montane steppes of northeastern Iran

Endemic species are believed to converge on narrow ranges of traits, with rarity reflecting adaptation to specific environmental regimes. We hypothesized that endemism is characterized by limited trait variability and environmental tolerances in two Dianthus species (Dianthus pseudocrinitus and Dianthus polylepis) endemic to the montane steppes of northeastern Iran. We measured leaf functional traits and calculated Grime’s competitor/stress-tolerator/ruderal (CSR) adaptive strategies for these and co-occurring species in seventy-five 25-m2 quadrats at 15 sites, also measuring a range of edaphic, climatic, and topographic parameters. While plant communities converged on the stress-tolerator strategy, D. pseudocrinitus exhibited functional divergence from S- to R-selected (C:S:R = 12.0:7.2:80.8% to 6.8:82.3:10.9%). Canonical correspondence analysis, in concert with Pearson’s correlation coefficients, suggested the strongest associations with elevation, annual temperature, precipitation seasonality, and soil fertility. Indeed, variance (s2) in R- and S-values for D. pseudocrinitus at two sites was exceptionally high, refuting the hypothesis of rarity via specialization. Rarity, in this case, is probably related to recent speciation by polyploidy (neoendemism) and dispersal limitation. Dianthus polylepis, in contrast, converged towards stress-tolerance. ‘Endemism’ is not synonymous with ‘incapable’, and polyploid neoendemics promise to be particularly responsive to conservation.

Plant functional groups associate with distinct arbuscular mycorrhizal fungal communities.

The benefits of the arbuscular mycorrhizal (AM) symbiosis between plants and fungi are modulated by the functional characteristics of both partners. However, it is unknown to what extent functionally distinct groups of plants naturally associate with different AM fungi. We reanalysed 14 high-throughput sequencing data sets describing AM fungal communities associating with plant individuals (2427) belonging to 297 species. We examined how root-associating AM fungal communities varied between plants with different growth forms, photosynthetic pathways, CSR (competitor, stress-tolerator, ruderal) strategies, mycorrhizal statuses and N-fixing statuses. AM fungal community composition differed in relation to all studied plant functional groups. Grasses, C4 and nonruderal plants were characterised by high AM fungal alpha diversity, while C4 , ruderal and obligately mycorrhizal plants were characterised by high beta diversity. The phylogenetic diversity of AM fungi, a potential surrogate for functional diversity, was higher among forbs than other plant growth forms. Putatively ruderal (previously cultured) AM fungi were disproportionately associated with forbs and ruderal plants. There was phylogenetic correlation among AM fungi in the degree of association with different plant growth forms and photosynthetic pathways. Associated AM fungal communities constitute an important component of plant ecological strategies. Functionally different plants associate with distinct AM fungal communities, linking mycorrhizal associations with functional diversity in ecosystems.

Soil–plant interactions in a pasture of the Italian Alps

ABSTRACT A detailed assessment of a pasture’s functioning based on soil properties characterization, floristic composition, and ‘functional summary’ by evaluating competitor–stress tolerator–ruderal (CSR) strategies is provided for a doline in Central Italian Alps. A floristic survey was carried out at 35 sampling points, representative of the main topographic features, soil and vegetation types; the functional profile at the community level was evaluated by assessing for each species its Grime’s CSR strategy; each point was characterized through soil profiles and topsoil (0–10 cm) sampling; pH, soil organic carbon and total nitrogen, available P, soil humus fraction, root density, bulk density, water content, and available water capacity were determined. Our study showed i) a strong relationship between vegetation, soil properties, topography, and grazing; ii) a prevalence of stress-tolerant strategies; iii) the ability of plant strategy variation to reflect the ecological parameters; and iv) the vegetation potentiality to be an indicator of environmental spatial variability.

Effectiveness of modern leaf analysis tools for the morpho‐ecological study of plants: the case of Primula albenensis

Scientific and technological progress has led to the creation of analysis tools that have revolutionized traditional studies in morphology and plant ecology. Recently developed methods and tools which, on the basis of leaf samples, allow for geometric morphometric analyses and the evaluation of functional strategies are good examples. These methods, still little used, have never been applied on leaf samples to simultaneously obtain information on their morphometry and the ecology of the plants. This article discusses the effectiveness of modern leaf analysis tools for geometric morphometrics (outline analysis) and studies of functional strategies based on the competitor‐stress tolerator‐ruderal (CSR) scheme, using a study of a steno‐endemic plant of the Alps, Primula albenensis Banfi et Ferl. as an example. These aspects were analyzed using leaf samples collected in the only two areas where this species grows. CSR analyses revealed that P. albenensis is not a stress‐tolerant species (C:S:R = 37:1:62), as previously thought. Moreover, no significant intraspecific differences in functional strategy were revealed. Instead, outline analysis highlighted a significant difference (p &lt; 0.001) between leaves collected from the two sampling areas. The results of this study and others reported in the literature therefore suggest that these modern methods of leaf analysis are cheap, effective and relatively simple to perform. Furthermore, researchers are able to carry out geometric morphometric and CSR analysis using the same samples of leaves in order to maximize the information content provided by the analysis of a plant material which may not be easily available.

Remotely Sensing Variation in Ecological Strategies and Plant Traits of Willows in Perialpine Floodplains

AbstractNatural floodplains are characterized by a complex habitat mosaic. However, damming, water storage, and hydropower production affect many floodplains by altering their natural habitat diversity. Field sampling data and imaging spectroscopy are used in combination with statistical models to assess resource allocation strategies of willow stands in perialpine floodplains. Three contrasting floodplain reaches located along two rivers in Switzerland serve as test beds: The Sarine River is partitioned into an upstream and downstream segment under the influence of a dam and a hydropower plant, while the Sense River represents an undisturbed, natural floodplain. Airborne imaging spectrometer data allow mapping of spatially distributed Competitor/Stress tolerator/Ruderal (CSR) strategies using a partial least square modeling approach. Using cross validation, we demonstrate that a statistical modeling approach can reveal variations in CSR scores based on the StrateFy model. Such intraspecific variation of CSR scores cannot be captured by a strategy categorization based solely on the species. Results reveal that willows shifted toward more competition and less stress tolerance along hydrologically altered reaches compared to the willows strategy along the natural control. Moreover, the overall distribution of strategies indicates that stress factors (i.e., limiting growth factors), rather than disturbance (i.e., events leading to partial or total destruction), shape the plant traits of alluvial willow trees. Detailed assessments of resource allocation strategies contribute to a more complete understanding of the continuous and reciprocal shaping between flow regimes, landforms, and alluvial vegetation.

Competitive Traits Are More Important than Stress-Tolerance Traits in a Cadmium-Contaminated Rhizosphere: A Role for Trait Theory in Microbial Ecology.

Understanding how biotic and abiotic factors govern the assembly of rhizosphere-microbial communities is a long-standing goal in microbial ecology. In phytoremediation research, where plants are used to remediate heavy metal-contaminated soils, a deeper understanding of rhizosphere-microbial ecology is needed to fully exploit the potential of microbial-assisted phytoremediation. This study investigated whether Grime's competitor/stress-tolerator/ruderal (CSR) theory could be used to describe the impact of cadmium (Cd) and the presence of a Cd-accumulating plant, Carpobrotus rossii (Haw.) Schwantes, on the assembly of soil-bacterial communities using Illumina 16S rRNA profiling and the predictive metagenomic-profiling program, PICRUSt. Using predictions based on CSR theory, we hypothesized that Cd and the presence of a rhizosphere would affect community assembly. We predicted that the additional resource availability in the rhizosphere would enrich for competitive life strategists, while the presence of Cd would select for stress-tolerators. Traits identified as competitive followed CSR predictions, discriminating between rhizosphere and bulk-soil communities whilst stress-tolerance traits increased with Cd dose, but only in bulk-soil communities. These findings suggest that a bacterium's competitive attributes are critical to its ability to occupy and proliferate in a Cd-contaminated rhizosphere. Ruderal traits, which relate to community re-colonization potential, were synergistically decreased by the presence of the rhizosphere and Cd dose. Taken together this microcosm study suggests that the CSR theory is broadly applicable to microbial communities. Further work toward developing a simplified and robust strategy for microbial CSR classification will provide an ecologically meaningful framework to interpret community-level changes across a range of biomes.

Methane‐Oxidizing Bacteria Communities Shift to Attenuate a Controlled Vadose Zone Methane Release

Methane‐Oxidizing Bacteria Communities Shift to Attenuate a Controlled Vadose Zone Methane Release

A plant strategy approach to understand multidecadal change in community assembly processes in Australian grassy woodlands

Summary The mechanisms of community assembly underpinning plant invasion are contested; limiting similarity predicts divergence in the traits of native and alien species whilst habitat filtering predicts trait convergence. Using site‐based floristic data collected three decades apart, we ask whether the competitor–stress tolerator–ruderal (CSR) strategies of herbaceous alien and native plant species in Australian woodlands show evidence of divergence (indicating limiting similarity) or convergence (indicating habitat filtering). We also ask whether increasing dereliction between the two sampling periods, as a result of declining fire frequency, has influenced habitat filtering processes. Null models were used to assess the similarity in CSR strategies of native and alien species in order to identify the community assembly processes driving woodland invasions. The observed frequencies of CSR types were also compared to randomly assembled communities from null models for species experiencing increases, decreases or static abundance changes between the two surveys to assess the impacts of dereliction on habitat filters. The spectrum of CSR strategies of the most common aliens (n = 25) was highly convergent with the strategies of the most common natives (n = 51). Competitive–ruderal species dominated the flora (&gt; 30% of all species), and strict competitors were absent. No aliens exhibited a stress‐tolerant strategy, and ruderals were more common in the alien flora (i.e. 36% vs. 18% of native species). Null models revealed differences in the CSR strategies of increaser and decreaser species at three of the ten sites examined, although none of these trends were consistent across the sites, indicating that increasing dereliction has not dramatically altered the habitat filters determining species admission. Synthesis. The similarity of CSR types between alien and native species indicates that habitat filtering is the principal community assembly process operating in the study region. We discuss our findings with respect to suggestions that limiting similarity and environmental filtering may be occurring simultaneously to structure plant communities. Species abundance changes due to dereliction were not evident as a coordinated shift in the functional composition of woodland dominants suggesting that time lags between altered management regimes (dereliction) and the functional response of species to habitat filters may still be playing out.

Why are many anthropogenic agroecosystems particularly species-rich?

Species-rich meadow and pasture habitats are recognised by the European Union Habitats Directive as targets for biodiversity conservation. High species richness is hypothesised to be associated with diversity in plant functional traits and life-history strategies, which are potentially restricted in situations of extremely high and low biomass production. However, variability in functional traits has yet to be investigated across a broad biomass range in nature. We measured variability in a range of functional traits and Grime's competitor, stress-tolerator, ruderal (CSR) strategies for species comprising lowland meadows, subalpine pastures, abandoned grassland and field margins at sites in northern Italy, alongside peak above-ground biomass. The factor most highly and positively correlated with species richness was strategy richness (the number of CSR strategies; Pearson's r = 0.864, P < 0.0001, n = 39), followed by variance in traits involved in leaf resource economics and the timing of flowering. Species richness, trait variance and strategy richness were greatest at intermediate biomass. Thus whilst extremes of biomass production were associated with relatively few taxa exhibiting similar trait values and specialised strategies, greater species richness was apparent in meadows and pastures in which species exhibited divergence in resource economics trait values, reproductive timing and strategy richness.

How well do seed production traits correlate with leaf traits, whole-plant traits and plant ecological strategies?

The principal axes of variation in plant function include the economics spectrum and size variation, both of which are implicated in primary ecological strategies. However, it is unclear to what extent vegetative traits and primary strategies correlate with reproductive traits, particularly for seed production. Fifteen traits, including whole-plant, leaf and seed traits (mass, number, total mass of seeds, volume and variance), were measured for 371 species from a range of habitats in Italy. Classification of Grime’s competitor, stress-tolerator, ruderal (CSR) strategies was applied from leaf area, leaf dry matter content and specific leaf area data. Relationships between vegetative traits, CSR values and seed traits were determined using principal components analysis (PCA) and Pearson’s correlation coefficients. PCA1 was an axis of economics, significantly correlated (positively) with leaf carbon concentration and S-selection, and (negatively) with leaf nitrogen concentration, flowering period and R-selection, but not seed traits. PCA2 was a plant size axis, significantly positively correlated with canopy height, leaf mass, C-selection and to a lesser extent seed size traits and total mass of seeds. PCA3 was a specific seed size-seed output axis, correlated positively with seed mass and volume, and negatively with seed number and variance. The loading of seed production traits on a general plant size axis alongside C-selection demonstrates that seed production traits are integral to CSR strategies. However, the stronger contribution of seed traits to a specific axis of variability is suggestive of reproductive variability beyond the CSR strategy, as predicted by the twin-filter model.