Towards a trait-based quantification of species niche

Aims Although the niche concept is of prime importance in ecology, the quantification of plant species' niches remains difficult. Here we propose that plant functional traits, as determinants of species performance, may be useful tools for quantifying species niche parameters over environmental gradients.Important findings Under this framework, the mean trait values of a species determine its niche position along gradients, and intraspecific trait variability determines its niche breadth. This trait-based approach can provide an operational assessment of niche for a potentially large number of species, making it possible to understand and predict species niche shifts under environmental changes. We further advocate a promising method that recently appeared in the literature, which partitions trait diversity into among- and within-community components as a way to quantify the species niche in units of traits instead of environmental parameters. This approach allows the switch of the focus from ecological niches to trait niches, facilitating the examination of species coexistence along undefined environmental gradients. Altogether, the trait-based approach provides a promising toolkit for quantifying the species ecological niche and for understanding the evolution of species niche and traits.     

Differential environmental response of plant functional types in hedgerow habitats

Classifying species into functional groups reacting similar to multiple environmental factors based on shared biological characteristics forms a major challenge faced by present-day ecologists. Based on data of a hedgerow plant community, this study uses a multivariate approach to analyse if trait-based emergent species groups have real functional significance, i.e. if these groups are characterised by specific response profiles to a wide range of environmental factors. First, the influence of explanatory variable groups (abiotic environmental conditions, management variables, structural aspects, historical background and spatial configuration of the hedgerow network) on distribution patterns of individual plant species was analysed with partial logistic regression. Significant relationships were found between the ecological characteristics of a species and the relative importance of variable groups affecting the distribution of that species within a hedgerow network landscape. Next, a trait-based classification of hedgerow plant species was constructed using a hierarchical clustering procedure. Woody species segregated into two distinct groups, with differences predominantly associated with generative traits, herbaceous species in four groups differing mainly in vegetative traits and habitat preferences. Clear differences in response to multiple environmental factors between the emergent species groups demonstrated the functional significance of the constructed classification. Relationships between the trait- and response profile were examined and their ecological relevance discussed. With respect to the woody species groups, zoochorous species were affected more strongly by hedgerow structure and landscape context than anemochorous species. For the herbaceous species clustering, a relatively strong impact was found, amongst others, of historical variables on species with woodland preference in comparison with other species groups.

Zusammenfassung

Die Klassifizierung von Arten in funktionelle Gruppen, die aufgrund von gemeinsamen biologischen Eigenschaften in gleicher Weise auf multiple Umweltfaktoren reagieren, ist eine große Herausforderung, vor der heutige Ökologen stehen. Auf der Grundlage von Daten einer Heckenpflanzen-Lebensgemeinschaft folgt diese Untersuchung einer multivariaten Vorgehensweise, um zu analysieren, ob die auftretenden Artengruppen auf der Basis von Merkmalen eine wirkliche funktionelle Bedeutung haben, d. h. ob diese Gruppen durch spezifische Antwortprofile auf eine große Auswahl von Umweltfaktoren charakterisiert sind. Zuerst wurde der Einfluss von Gruppen erklärender Variablen (abiotische Umweltbedingungen, Managementvariablen, strukturelle Aspekte, geschichtlicher Hintergrund und räumliche Anordnung des Heckennetzes) auf die Verteilungsmuster einzelner Pflanzenarten mit partiellen logistischen Regressionen analysiert. Signifikante Beziehungen wurden zwischen den ökologischen Eigenschaften einer Art und der relativen Wichtigkeit von Variablengruppen gefunden, die die Verbreitung der Art innerhalb der Heckennetzlandschaft beeinflussen. Im Anschluss wurde eine merkmalsbasierte Klassifikation der Heckenpflanzenarten unter der Verwendung einer hierarchischen Gruppierungsprozedur konstruiert. Aufgrund von Unterschieden, die vor allem mit den Fortpflanzungsmerkmalen einhergingen, trennten sich die holzigen Arten in zwei verschiedene Gruppen auf. Krautige Arten trennten sich in vier Gruppen auf, die sich vor allem in den vegetativen Merkmalen und Habitatpräferenzen unterschieden. Klare Unterschiede in den Reaktionen auf multiple Umweltfaktoren zwischen den entstandenen Artengruppen demonstrierten die funktionelle Bedeutung der konstruierten Klassifikation. Die Beziehungen zwischen den Merkmals- und Antwortprofilen wurden untersucht und ihre ökologische Relevanz diskutiert. In Bezug auf die holzigen Artengruppen waren die zoochoren Arten stärker von der Heckenstruktur und dem Landschaftskontext beeinflusst als anemochore Arten. Für die krautigen Artencluster wurde unter anderem ein relativ starker Einfluss von historischen Variablen auf die Arten mit Waldpräferenz im Vergleich zu anderen Artengruppen gefunden.     

Testing Surrogacy Assumptions: Can Threatened and Endangered Plants Be Grouped by Biological Similarity and Abundances?

There is renewed interest in implementing surrogate species approaches in conservation planning due to the large number of species in need of management but limited resources and data. One type of surrogate approach involves selection of one or a few species to represent a larger group of species requiring similar management actions, so that protection and persistence of the selected species would result in conservation of the group of species. However, among the criticisms of surrogate approaches is the need to test underlying assumptions, which remain rarely examined. In this study, we tested one of the fundamental assumptions underlying use of surrogate species in recovery planning: that there exist groups of threatened and endangered species that are sufficiently similar to warrant similar management or recovery criteria. Using a comprehensive database of all plant species listed under the U.S. Endangered Species Act and tree-based random forest analysis, we found no evidence of species groups based on a set of distributional and biological traits or by abundances and patterns of decline. Our results suggested that application of surrogate approaches for endangered species recovery would be unjustified. Thus, conservation planning focused on individual species and their patterns of decline will likely be required to recover listed species.     

A trait-based approach to community assembly: partitioning of species trait values into within- and among-community components

Plant functional traits vary both along environmental gradients and among species occupying similar conditions, creating a challenge for the synthesis of functional and community ecology. We present a trait-based approach that provides an additive decomposition of species' trait values into alpha and beta components: beta values refer to a species' position along a gradient defined by community-level mean trait values; alpha values are the difference between a species' trait values and the mean of co-occurring taxa. In woody plant communities of coastal California, beta trait values for specific leaf area, leaf size, wood density and maximum height all covary strongly, reflecting species distributions across a gradient of soil moisture availability. Alpha values, on the other hand, are generally not significantly correlated, suggesting several independent axes of differentiation within communities. This trait-based framework provides a novel approach to integrate functional ecology and gradient analysis with community ecology and coexistence theory.     

Defining plant functional groups to guide rare plant management

To effectively manage plant populations for conservation, there is a need to provide reliable information on the conditions required for maintaining viable populations. This is particularly true for the management of populations of rare plant taxa. Western Australia contains over 45% of Australia’s gazetted rare or threatened flora, 80% of which are found within the highly fragmented southwest region. Resources do not exist to undertake comprehensive studies on the population dynamics and demographics for every rare plant of this diverse region. Here, we describe a method of classifying rare plant taxa into functional groups as a basis for guiding rare flora conservation and management. Data on four floral and two life-history traits were collected for each of the 351 declared rare flora taxa of Western Australia. A hierarchical, agglomerative clustering method was applied to the resulting taxa by traits matrix to extract emergent groupings of plant taxa. The resulting polythetic groups were analysed to determine the variation in traits, including response to disturbance and recorded flower visitors, and how these may affect population persistence in a fragmented landscape. Multivariate methods were used to define emergent groups based on a combination of floral structure and life-history traits of the declared rare flora of Western Australia. Seven emergent functional groups were identified and were largely differentiated by flower shape and life form. These seven functional groupings varied significantly in their response to disturbance. By deriving these functional groups, we plan to develop models for each group on how rates of pollination, seed production and seed fitness are affected by population size and landscape context. The rationale would be to use these profiles to determine whether there are thresholds in population size or position in the landscape at which reproductive rates severely decline. General management guidelines could then be developed for each functional group. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Nomenclature Paczkowska and Chapman (2000).     

A proposal to use plant demographic data to assess potential weed biological control agents impacts on non-target plant populations

Weed biocontrol programs aim to reduce the spread and population growth rate of the target plant while stabilizing or increasing populations of those native species considered under threat by invasive plants. This goal is not unique to weed biocontrol but applies to all other invasive plant management techniques, though such information is rarely collected. Without this information, success of management interventions can be ambiguous, and regulatory agencies, the public, policy makers, funders and land managers cannot be held accountable for chosen treatments. A fundamental reform, including use of demographic studies and long-term assessments, are essential to guide weed biocontrol programs. We propose to add use of plant demography (an assessment of how environmental factors and ecological interactions, for example competition, disease or herbivory, may affect plant populations by altering survival, growth, development and reproductive rates of plant individuals) during host specificity risk assessments of potential biological control agents. Demographic models can refine assessments of potential impacts for those plant species that experience some feeding or larval development during host specificity testing. Our proposed approach to focus on impact on plant demography instead of attack on plant individuals is useful in appropriately gauging threats potential weed biocontrol agents may pose to non-target species after field release.     

A functional trait perspective on plant invasion

Background and Aims

Global environmental change will affect non-native plant invasions, with profound potential impacts on native plant populations, communities and ecosystems. In this context, we review plant functional traits, particularly those that drive invader abundance (invasiveness) and impacts, as well as the integration of these traits across multiple ecological scales, and as a basis for restoration and management.

Scope

We review the concepts and terminology surrounding functional traits and how functional traits influence processes at the individual level. We explore how phenotypic plasticity may lead to rapid evolution of novel traits facilitating invasiveness in changing environments and then ‘scale up’ to evaluate the relative importance of demographic traits and their links to invasion rates. We then suggest a functional trait framework for assessing per capita effects and, ultimately, impacts of invasive plants on plant communities and ecosystems. Lastly, we focus on the role of functional trait-based approaches in invasive species management and restoration in the context of rapid, global environmental change.

Conclusions

To understand how the abundance and impacts of invasive plants will respond to rapid environmental changes it is essential to link trait-based responses of invaders to changes in community and ecosystem properties. To do so requires a comprehensive effort that considers dynamic environmental controls and a targeted approach to understand key functional traits driving both invader abundance and impacts. If we are to predict future invasions, manage those at hand and use restoration technology to mitigate invasive species impacts, future research must focus on functional traits that promote invasiveness and invader impacts under changing conditions, and integrate major factors driving invasions from individual to ecosystem levels.     

An invasive plant and climate change threat index for weed risk management: Integrating habitat distribution pattern and dispersal process

Invasive plants pose a significant threat to the integrity and biodiversity of native systems. Weed risk assessment and management provides a framework for assessing this threat. However, relatively little attention has been paid to the threat posed to biodiversity by invasive plants in a rapidly changing climate. This paper aims to estimate the impacts of climate change on exotic plant habitats, and incorporates elements of dispersal to develop a management index for identifying invasive plant threat under climate change. The spatial distribution of habitat suitability is modelled at the landscape scale for multiple exotic plant species under current climate and a climate change scenario for the year 2030. Expert opinion of the dominant dispersal mechanisms and weed status is used to model relative dispersal threat of each exotic plant species. These pattern and process outputs are integrated to create a multi-species management priority layer in an effort to synthesise the inherently complex outputs from multiple models of multiple species. The overall multi-species management index thus combines pattern and process to identify geographic locations at greatest threat from invasion under climate change.     

Plant functional composition and ecosystem properties: the case of peatlands in South Africa

The assumption that ecosystems with similar emergent properties consist of similar functional groupings of plant species is tested by comparing three peatlands from different bioregions across South Africa. They are Mfabeni Swamp in the subtropical coastal region, Wakkerstroom on the inland plateau, and Goukou wetland in the Winter Rainfall region of the Western Cape. In each of the three peatlands, about 400 small vegetation plots have been made from which the abundance of each species per wetland can be assessed. The most dominant species in these plots have been investigated for 17 traits. The functional composition of the vegetation types has been compared across the three peatlands and Functional Diversity has been calculated, taking the dominance of each species into account. One peatland differed greatly from the other two, since the dominant species was of a functional type (“Palmiet/woody sedge”) that was very divergent from any other peatland species found in the study. This functional type can be considered an ecosystem engineer and the effects that this functional type has on the ecosystem results in the occurrence of many other functional types that do not occur in the other peatlands. When we consider emergent traits of an ecosystem as a function of all the plant functional traits that occur in that ecosystem, then peatlands can be regarded as a heterogeneous group of ecosystems. Even if emergent properties such as peat formation are similar between ecosystems, those ecosystems may still consist of very different functional groups. Ecosystem engineers have an impact on the final functional composition of an ecosystem and the degree in which ecosystem engineering plays a role in peatlands differs between different peatlands.     

Necessity and reality of monitoring threatened European vascular plants

Species monitoring is the regular observation and recording of changes in status and trend of species in a certain territory. The primary purpose of monitoring is to collect information that can be used to examine the outcomes of management actions and to guide management decisions. Here, we analyze plant species monitoring to provide a first overview on efforts made to monitor trends in vascular plant biodiversity in Europe. Our study is based on an assessment of 63 plant monitoring schemes from Europe (collected into a database “DaEuMon”), and 33 schemes found with literature screening. Altogether, the monitoring schemes cover 354 vascular plant species, of which 69 are listed in Annex II of the EU Habitats Directive (= EU protected species; Annex II includes 420 species). In most cases, an EU protected plant species occurs in 3 countries but is monitored in only 1 country. Scientific interest was the main reason for launching a monitoring scheme in 21% of the schemes from the database, but in 58% of the schemes from the literature survey. The current schemes collect insufficient data particularly on the dynamics of the extent and distribution pattern of species. We conclude that planning to publish monitoring data when designing a scheme would improve the quality and general effect of monitoring programs. The needs to cover the taxonomic diversity and the integration of different scales, as well as the inclusion of monitoring in the context of different types of sustainable management would require a strong emphasis in the development of monitoring schemes.     

Comparison of two plant functional approaches to evaluate natural restoration along an old‐field – deciduous forest chronosequence

Question: Are direct and indirect trait‐based approaches similar in their usefulness to synthesize species responses to successional stages? Location: Northern hardwood forests, Québec, Canada (45°01′–45°08′N; 73°58′–74°21′W). Methods: Two different trait‐based approaches were used to relate plant functional traits to succession on an old‐field – deciduous forest chronosequence: (i) a frequently used approach based on co‐occurrence of traits (emergent groups), and (ii) a new version of a direct functional approach at the trait level (the fourth‐corner method). Additionally, we selected two different cut‐off levels for the herb subset of the emergent group classification in order to test its robustness and ecological relevance. Results: Clear patterns of trait associations with stand developmental stages emerged from both the emergent group and the direct approach at the trait level. However, the emergent group classification was found to hide some trait‐level differences such as a shift in seed size, light requirement and plant form along the chronosequence. Contrasting results were obtained for the seven or nine group classification of the herbaceous subset, illustrating how critical is the number of groups for emergent group classification. Conclusion: The simultaneous use of two different trait‐based approaches provided a robust and comprehensive characterization of vegetation responses in the old‐field – deciduous forest chronosequence. It also underlines the different goals as well as the limitations and benefits of these two approaches. Both approaches indicated that abandoned pastures of the northern hardwood biome have good potential for natural recovery. Conversion of these lands to other functions may lead to irremediable loss of biodiversity.     

Alien flora of mountains: global comparisons for the development of local preventive measures against plant invasions

Aim We use data from 13 mountain regions and surrounding lowland areas to identify (1) the origins, traits and cultural uses of alien plant species that establish in mountains, (2) the alien species that are most likely to be a threat and (3) how managers might use this information to prevent further invasions. Location Australia, Canada, Chile, India, New Zealand, South Africa, Spain, Switzerland, USA. Methods Lists of alien species were compiled for mountains and their surrounding or nearby lowlands. Principal co‐ordinates analysis was performed on a matrix of similarities created using presence/absence data for alien species. The significance of differences between means for (1) similarity metrics of lowland and mountain groups and (2) species traits of lowland and mountain alien floras was determined using t‐tests. In seven of the 13 mountain regions, lists of alien species undergoing management were compiled. The significance of differences between proportions of traits for species requiring and not requiring management input was determined with chi‐square tests. Results We found that the proximal lowland alien flora is the main determinant of a mountain region’s alien species composition. The highest similarities between mountain floras were in the Americas/Pacific Region. The majority of alien species commonly found in mountains have agricultural origins and are of little concern to land managers. Woody species and those used for ornamental purposes will often pose the greatest threat. Main conclusions Given the documented potential threat of alien species invading mountains, we advise natural resource managers to take preventive measures against the risk of alien plant invasion in mountains. A strategy for prevention should extend to the surrounding lowland areas and in particular regulate the introduction of species that are already of management concern in other mountains as well as climatically pre‐adapted alien mountain plants. These may well become more problematic than the majority of alien plants currently in mountains.     

Spatial Prediction of Invasion Success Across Heterogeneous Landscapes using an Individual-Based Model

The limited resources available for managing invasive plant species in native ecosystems and the magnitude of the problem make it essential that we develop methods to prioritize sites for management efforts. We used the individual-based simulation model ECOTONE in conjunction with climate and soil texture data to identify grassland site types where the invasive perennial forb Acroptilon repens is likely to be successful, and to create a threat map indicating the most vulnerable regions of Colorado. Acroptilon repens has the potential to become most abundant in dry areas with fine-textured soils. This information can be used to direct management efforts towards the areas at greatest risk, allowing the most effective use of limited resources. The most common approach for identifying invasible regions has been to extrapolate from the locations of existing invasions to find similar sites. Two major drawbacks to this method are the lack of consideration of the role of the existing plant community in inhibiting or facilitating invasion, and the assumption that the invading species is at equilibrium with the environment. The combination of an individual-based simulation model and a geographic information system provides a flexible tool to investigate the community and regional dynamics of invasive plant species.     

Securing a future for China's plant biodiversity through an integrated conservation approach

The severely threatened Chinese flora urgently needs a new, well adapted to China and properly formulated conservation strategy. The present review provides a detailed conservation methodology that complements previously described guidelines for preservation of plant species with extremely small populations (PSESP) in China. This review adds to the above concept in several aspects, making it relevant to all threatened Chinese plant species. The proposed integral conservation strategy has the following crucial components: -ecoregional basis for conservation planning and implementation; -a unified scoring system that is used in regional systematic planning for reserve design, monitoring and assessment of efficiency of a reserve network, and creation of seed banks and living collections; -a focus on population demography and the presence of naturally occurring regeneration as the key criteria for defining the conservation status of a species and the appropriate major focus of the species recovery plan; -creation of multi-species living collections that preserve species genetic variation and provide material for in situ actions; -experimental translocation of threatened species into multiple locations within and outside their known range. Adopting and implementing these strategies successfully and more fully in China requires that the country changes PA legislation and improves PA management, the National Science Foundation of China (NSFC) re-prioritizes the type of research that receives research funds, and local scientists improve their approach toward information sharing.     

Weeds and biodiversity conservation: A review of managing weeds under the New South Wales Threatened Species Conservation Act 1995

Summary   In New South Wales, alien plants pose the second greatest threat to biodiversity behind land clearing and habitat loss, yet current weed management does not always address the biodiversity at risk or put in place mechanisms to ensure their recovery. The problem arises in part from an assumption that control programmes which focus only on the weed will result in a biodiversity benefit, rather than acknowledging the need for an assessment of the biodiversity at risk and subsequent incorporation of such information into management strategies. The New South Wales Threatened Species Conservation Act 1995 (TSC Act) has been used as a tool to integrate weed control and biodiversity management through the listing of weeds as key threatening processes and the development and implementation of Threat Abatement Plans (TAPs). Through this process, weed management is forced to focus on actual biodiversity conservation outcomes by directing control to areas where the likelihood of a positive biodiversity response is maximized. Bitou Bush ( Chrysanthemoides monilifera ssp. rotundata ) was the first weed species listed under the TSC Act as a key threatening process and to have a TAP prepared. Implementation of the Bitou Bush TAP is now potentially assisting the recovery of over 150 native plant species and 24 ecological communities at more than 160 sites. The TAP process is now being used for Lantana ( Lantana camara ) nationally and for all widespread weed species that threaten biodiversity within each of the 13 Catchment Management Authorities across New South Wales. By focusing the objectives of weed control on biodiversity protection and recovery, and ensuring that sites throughout the distribution of the weed are prioritized, threat reduction and conservation outcomes are more likely to occur at a landscape scale.     

Changes in plant species diversity of aquatic ecosystems in the agricultural landscape in West Poland in the last 30 years

The aim of this study was to diagnose changes in species composition and their dynamics caused by human impact in aquatic and marsh vegetation in the contemporary agricultural landscape. The most serious threat was an increase in the nitrogen content of surface waters and groundwater which had resulted from the intensive management of the surrounding areas. Floristic data were collected in a lake, peaty pools and a drainage ditch within agricultural areas in the Wielkopolska region (West Poland) in 2006–2007, and compared with data from 1976–1980. The species richness had significantly increased and the shares of sociological and geographical–historical groups had changed clearly. This was reflected in an increase in the synanthropization index from 32.6 to 48.5. All the changes resulted from human impact, which had caused the acceleration of eutrophication in the water bodies. The natural plant succession, especially in the reed beds and sedge communities, was also accelerated due to human pressure. The vascular plant species richness in aquatic and marsh habitats increased by 40, because 15 species had disappeared and 55 new had appeared. However, six moss and four stonewort species had disappeared and only three new moss species were found. The increase in species richness did not raise the natural value of the flora, because the new species group is composed mainly of synanthropic species: native (apophytes) and alien, whereas all the lost species are endangered and rare native species (spontaneophytes), which occur only in natural or seminatural conditions. On the local scale, as species richness increases, plant communities lose their natural value. As an effect of synanthropization the stenotopic species disappear, while the widespread species spread even more. The increase in species richness is a consequence of appearance of species with a wide ecological scale that are not typical for aquatic ecosystems in patches of emergent vegetation. Finally, the species diversity of the whole landscape declines.     

Dispersal traits determine passive restoration trajectory of a Nigerian montane forest

Passive restoration methods offer great promise for tropical regions where resources are limited but the success of such efforts can be variable. Using trait-based theory, we investigated the likely trajectories of passive restoration efforts in a degraded Nigerian montane forest system recently protected from burning and cattle grazing. We quantified the density, species richness, and functional trait dispersion of dispersed seeds and seedling communities at increasing distances from the forest edge. We then determined which plant traits are responsible for colonisation by quantifying changes in functional-trait dispersion and relative frequencies of dispersal-linked traits with increasing distance from the forest. We found a rapid decrease in density and species richness, and significant species turnover in both seeds and seedlings just beyond the forest edge. This was mirrored by a significant decline in functional-trait dispersion and a shift in the relative frequencies of dispersal-linked traits. These findings suggest that the reassembly of plant communities adjacent to remnant forest is dependent on functional traits present in these remnant source populations, providing support for the incorporation of trait-based theory in restoration management.     

Comparing and contrasting threat assessments of plant species at the global and sub-global level

Evidence-based assessments of extinction risk are established tools used to inform the conservation of plant species, and form the basis of key targets within the framework of the Global Strategy for Plant Conservation (GSPC). An overall picture of plants threat assessments is challenging due to the use of a variety of methodologies and range in scope from global to subnational. In this study, we quantify the state of progress in assessing the extinction risk of all land plants, determine the key geographic and taxonomic gaps with respect to our understanding of plant extinction risk, and evaluate the impact of different sources and methodologies on the utility of plant assessments. To this end, we have analyzed a cleaned dataset compiled from IUCN Red List of Threatened Species and Regional Red Lists. We reveal that there are assessments available for 89,810 distinct species or 25% of all accepted land plant species. However unlike with other major organismal lineages the bulk of the plant species assessments are derived from Regional Red Lists, and not the Global IUCN Red List. We demonstrate that this bias towards regional assessments results in distinct taxonomic and geographic strengths and weaknesses, and we identify substantial taxonomic and geographic gaps in the assessment coverage. With species that have been assessed in common at both global and regional levels, we explore the implications of combining threat assessments from different sources. We find that half of global and regional assessments do not agree on the exact category of extinction risk for a species. Regional assessments assign a higher risk of extinction; or underestimate extinction risk with almost equal frequency. We conclude with recommended interventions, but support the suggestion that all threat assessments should be pooled to provide more data and broaden the scope of threat assessments for monitoring progress towards GSPC targets.     

Invasive plants and their ecological strategies: prediction and explanation of woody plant invasion in New England

Effective management of introduced species requires the early identification of species that pose a significant threat of becoming invasive. To better understand the invasive ecology of species in New England, USA, we compiled a character data set with which to compare non-native species that are known invaders to non-native species that are not currently known to be invasive. In contrast to previous biological trait-based models, we employed a Bayesian hierarchical analysis to identify sets of plant traits associated with invasiveness for each of three growth forms (vines, shrubs, and trees). The resulting models identify a suite of 'invasive traits' highlighting the ecology associated with invasiveness for each of three growth forms. The most effective predictors of invasiveness that emerged from our model were 'invasive elsewhere', 'fast growth rate', 'native latitudinal range', and 'growth form'. The contrast among growth forms was pronounced. For example, 'wind dispersal' was positively correlated with invasiveness in trees, but negatively correlated in shrubs and vines. The predictive model was able to correctly classify invasive plants 67% of the time (22/33), and non-invasive plants 95% of the time (204/215). A number of potential future invasive species in New England that deserve management consideration were identified.     

Aboveground resilience to species loss but belowground resistance to nitrogen addition in a montane plant community

Aims Decades of empirical work have demonstrated how dominant plant species and nitrogen fertilization can influence the structure and function of plant communities. More recent studies have examined the interplay between these factors, but few such studies use an explicit trait-based framework. In this study, we use an explicit trait-based approach to identify potential mechanisms for community-level responses and to test ecological niche theory.Methods We experimentally manipulated plant communities (control, ?dominant species, ?random biomass) and nitrogen (N) inputs (control, +organic N, +inorganic N) in a fully factorial design. We predicted that traits related to plants' ability to take up different forms of soil N would differ between dominant and subordinate species, resulting in interactive effects of dominant species loss and N fertilization on plant community structure and function. The study took place in a montane meadow in the Rocky Mountains, Colorado, USA.Important findings After four years, the plant community in removal plots converged toward a species composition whose leaf and root functional traits resembled those of the previously removed dominant species. Ecosystem productivity generally increased with N addition: soil carbon efflux was ~50% greater when either form of N was added, while inorganic N addition increased aboveground biomass production by ~60% relative to controls. The increase in production was mediated by increased average height, leaf mass:area ratio and leaf dry matter content in plant communities to which we added inorganic N. Contrary to our predictions, there were no interactive effects of N fertilization and dominant species loss on plant community structure or ecosystem function. The plant community composition in this study exhibited resistance to soil N addition and, given the functional convergence we observed, was resilient to species loss. Together, our results indicate that the ability of species to compensate functionally for species loss confers resilience and maintains diversity in montane meadow communities.