Competitive Ability Of Species Research Articles

Grazing and light modify Silene latifolia responses to nutrients and future climate

Altered climate, nutrient enrichment and changes in grazing patterns are important environmental and biotic changes in temperate grassland systems. Singly and in concert these factors can influence plant performance and traits, with consequences for species competitive ability, and thus for species coexistence, community composition and diversity. However, we lack experimental tests of the mechanisms, such as competition for light, driving plant performance and traits under nutrient enrichment, grazer exclusion and future climate. We used transplants of Silene latifolia, a widespread grassland forb in Europe, to study plant responses to interactions among climate, nutrients, grazing and light. We recorded transplant biomass, height, specific leaf area (SLA) and foliar carbon to nitrogen ratio (C:N) in full-factorial combinations of future climate treatment, fertilization, grazer exclusion and light addition via LED-lamps. Future climate and fertilization together increased transplant height but only in unlighted plots. Light addition increased SLA in ambient climate, and decreased C:N in unfertilized plots. Further, transplants had higher biomass in future climatic conditions when protected from grazers. In general, grazing had a strong negative effect on all measured variables regardless of added nutrients and light. Our results show that competition for light may lead to taller individuals and interacts with climate and nutrients to affect traits related to resource-use. Furthermore, our study suggests grazing may counteract the benefits of future climate on the biomass of species such as Silene latifolia. Consequently, grazers and light may be important modulators of individual plant performance and traits under nutrient enrichment and future climatic conditions.

Thermoregulatory opportunity and competition act independently on life‐history traits in aquatic ectotherms

Abstract Many ectothermic species use behavioural thermoregulation to reduce their exposure to climate change. The buffering effect of behavioural thermoregulation will depend on the time available for an ectotherm to attain a body temperature within the target range, that is, the ‘opportunity for thermoregulation’. Behavioural thermoregulation can be further altered by the presence of competitors. Spatiotemporal dynamics in opportunity for thermoregulation and competition intensity should affect variation in ectotherm life history and fitness; however, experimental support for their joint influence is missing. I tested this prediction in a mesocosm experiment using larvae of two sympatric amphibians, the alpine newt Ichthyosaura alpestris and the common newt Lissotriton vulgaris. Thermoregulatory opportunities and competition intensities were manipulated by exposing larvae to warmer temperatures and altering densities of con‐ and heterospecifics. Life‐history traits were monitored until metamorphic emergence from the water. Thermoregulatory opportunity accelerated differentiation rate and time to metamorphic emergence, while both intra‐ and interspecific competition affected growth rate and mass at emergence. The impact of competition on survival and injury rates varied between taxa. Thermoregulatory opportunity and competition impacted larval life‐history traits in an additive fashion. Suitable conditions for thermoregulation allowed larvae to shorten their developmental period, and thus escape from the aquatic environment earlier than in thermoregulatory challenging environment. Competition was a primary determinant of mass at emergence, which is an important fitness correlate in amphibians. Species‐specific survival under competition may contribute to variation in habitat requirements between sympatric taxa. To sum up, predictions on the impact of climate change on ectotherm life histories require information not only about environmental temperatures, but also about species thermoregulatory opportunities and competitive abilities. Thermoregulatory opportunity is an ecologically relevant habitat property not only for basking ectotherms but also for taxa using less conspicuous thermoregulatory adjustments. The influence of thermoregulatory opportunity and competitive interactions on life histories varies among traits, indicating the need for a multi‐trait approach for understanding the complex influences of environmental change on ectotherm population dynamics and species interactions. Read the free Plain Language Summary for this article on the Journal blog.

Differences in leaf traits of Spartina alterniflora between native and invaded habitats: Implication for evolution of alien species competitive ability increase

The enemy release and pre-adaptation of alien species often drive their contemporary evolution across latitudinal gradients within its invasive and native ranges. Leaf functional traits constitute an important part of plant functional traits, reflecting their resource acquisition and usage. Thus, comparing the leaf functional traits (growth and defense traits) and latitude patterns of invasive and native plants could provide leading indicators of contemporary evolutionary and adaptative abilities that explain the success of invasive plants. Spartina alterniflora, a coastal wetland invasive plant native to the Atlantic coast and the Gulf of Mexico, has invaded China along the coast wetland (19–40 °N), similar to the United States (27–43 °N). To understand the leaf trait differences and variation across latitudes among continents of S. alterniflora within its invasive and native ranges and determine which factors drive leaf trait variation across latitudes, we investigated the relationship between leaf traits, related to growth (leaf area and specific leaf area), and defensive traits (leaf thickness and leaf toughness) at 10 invaded locations and 15 native locations. We identified correlations between leaf traits and abiotic conditions such as annual mean temperature, tide range, and soil salinity. Compared with native S. alterniflora, Chinese costal S. alterniflora has a larger leaf area and specific leaf area, less leaf thickness, and lower leaf toughness, suggesting that biosynthetic resources are transferred from defense to competitive traits, and indirectly supporting the Evolution of Increased Competitive Ability (EICA) hypothesis. The leaf area, specific leaf area, thickness, and toughness of S. alterniflora from both ranges had similar quadratic latitudinal relationships. Some of these relationships were stronger in the invasive range than the native range, indicating that the leaf traits of invasive S. alterniflora experienced pre-adaptation and had high phenotypic plasticity. Tide range, soil salinity, and especially temperature formed latitudinal gradients in different geographic regions. By analyzing indicators of leaf functional traits across geographical ranges, this study shows that the escape from natural enemies plays an important role in the successful invasion of S. alterniflora, while pre-adaptation and high phenotypic plasticity promote its rapid expansion along the latitudinal gradients.

The role of fluvial landforms as a driver of vegetation variation on a floodplain in southern Thailand

Floodplain vegetation is rare in southern Thailand due to the generally steep gradient through which major rivers flow and high pressure of land use. This study aims to increase the understanding of factors and processes that govern vegetation variation and diversity in a floodplain to provide information for conservation and management of this threatened and rare ecosystem. A total of 20 plots, each 625 m2, were laid on three broad categories of fluvial landforms to collect data on the number of tree species (woody plants with diameter at breast height (DBH) ≥ 5 cm), soil variables, flooding, history of land use and distance to the inner curve of the channel in Nong thung thong Non-Hunting Area, Thailand. Three 4 m2 subplots were nested within each 625 m2 plot to estimate shrub composition and coverage. The alpha and beta diversity of the tree species in each fluvial landform were calculated. The relationships between vegetation data and environmental factors were explored through transformation-based Redundancy Analysis (tb-RDA) and univariate analyses. Beta diversity between abandoned channel and ridge plots, and between ridge and shallow depression plots was higher than the dissimilarities within each fluvial landform, and the balanced variation in abundance contributed to the major part of the dissimilarities. These results indicate different tolerance ranges or competitive ability of species between these fluvial landforms. Results from the tb-RDA showed that tree species composition varied with fluvial landforms and soil calcium content. Median of flooding was associated with fluvial landforms. In addition, soil calcium content could be controlled by fluvial landform because clay and calcium were correlated, and both were associated with fluvial landforms. These results suggest that variation in fluvial landforms causes variation in flooding duration, edaphic factors, vegetation variation, and ultimately, the biodiversity in this floodplain.

Habitat heterogeneity mediates effects of individual variation on spatial species coexistence.

Numerous studies have documented the importance of individual variation (IV) in determining the outcome of competition between species. However, little is known about how the interplay between IV and habitat heterogeneity (i.e. variation and spatial autocorrelation in habitat quality) affects species coexistence at the landscape scale. Here, we incorporate habitat heterogeneity into a competition model with IV, in order to explore the mechanism of spatial species coexistence. We find that individual-level variation and habitat heterogeneity interact to promote species coexistence, more obviously at lower dispersal rates. This is in stark contrast to early non-spatial models, which predicted that IV reinforces competitive hierarchies and therefore speeds up species exclusion. In essence, increasing variation in patch quality and/or spatial habitat autocorrelation moderates differences in the competitive ability of species, thereby allowing species to coexist both locally and globally. Overall, our theoretical study offers a mechanistic explanation for emerging empirical evidence that both habitat heterogeneity and IV promote species coexistence and therefore biodiversity maintenance.

Derivation of species interactions strength in a plant community with game theory

Derivation of species interactions function in a plant community and the quantified analysis of the effects of multi-species interactions poses a challenge because of the large number of interactions in a community. However, through the interaction with the local environment and resources as well as the adjustment of species richness and distribution frequency, the community will eventually reach the highest resources utilization efficiency to attain the status of an ecologically stable community. We developed the species-interaction function based on above characteristic of stable community and the evolutionarily stable strategies theory of game theory, the conditions of coexistence, and the maximization of the utilization efficiency of minimal restriction resources. We discovered that once the ability of different species to occupy an unoccupied or vacant place in a plant community (the competitive ability of species) has been realized to the maximum extent, the product of the community richness and the harmonic mean of the fitness of all species is equal to the product of the total amount of minimal restriction resources and the resources utilization efficiency of the community. The species-interaction strength further proves that the interspecific and intraspecific interactions strengths are unified in the process of competing for resources. Through validation with published species diversity data covering fifteen years of a grassland community, it is proved that our species interaction model was able to explain the changes of plant diversity in the communities with the minimum limitation resource changes with the impact of global climate changes.

Mechanistically derived dispersal kernels explain species-level patterns of recruitment and succession.

Species-level dispersal information can give mechanistic insights into how spatial processes impact plant communities. Unfortunately, field-based estimates of the dispersal abilities of multiple members of a community are often lacking for many plant systems. Here, we provide a simple method for measuring dispersal ability for large numbers of grassland plant species based on functional traits. Using this method, we estimated the dispersal ability of 50 co-occurring grassland species using the Wald Analytical Long-distance Dispersal (WALD) model. Grassland plants species are often used for developing community theory, yet species-level estimates of their dispersal abilities are comparatively rare. We use these dispersal measurements to examine the relationship between species dispersal abilities and successional dynamics using data from a 90-yrold field chronosequence. We find that our estimated dispersal measurements matched field-based establishment observations well, and estimated species colonization, competitive, and establishment abilities. We hope that this method for measuring dispersal ability of multiple species within a community, and its demonstrated ability to generate predictions for spatial ecology, will encourage more studies of the explicit role of dispersal in plant community ecology.

Local canopy diversity does not influence phenotypic expression and plasticity of tree seedlings exposed to different resource availabilities

Species diversity seems to favour the environmental heterogeneity and habitat complexity, which in turn favour the selection of greater levels of phenotypic plasticity of plant species. While recent evidence suggested that local species diversity and environmental heterogeneity act as selective pressures over mean traits and plasticity for herbs, which adjust their traits to the identity and species richness of their neighbors, little is known for tree species. Here, we investigated shifts in the phenotypic expression and plasticity of seedlings of two functional groups (broadleaved and conifers) coming from communities with different canopy species richness in two contrasting forest types (a hemiboreal and a Mediterranean forest). We carried out a greenhouse experiment to test the response of seedlings to different light and nutrient availability, measuring different functional traits related to resource acquisition. Our results indicated that seedlings coming from monospecific and more diverse communities had similar phenotypic expression and response capacity to the study treatments. This finding suggests that canopy species richness did not exert a detectable selective pressure on tree phenotypes and plasticity at this early stage. Additionally, we found great differences in the phenotypic expression and plasticity between the two major functional groups (conifers and broadleaved species). Specifically, we found that broadleaves reached higher mean values in key functional traits by a greater plasticity to both light and nutrient treatment than coniferous species, mainly in the Mediterranean forest. This finding suggests that broadleaved species potentially have a higher capacity to respond to future changing environmental conditions than conifers at early stages, conferring an advantage that can be crucial for the species competitive ability for resources and, therefore, for survival.

Emergence of weak‐intransitive competition through adaptive diversification and eco‐evolutionary feedbacks

Abstract Indirect biotic interactions—such as intransitive competition—are increasingly recognized as being important in shaping ecological patterns in natural systems. Over long time‐scales, such indirect interactions may affect the evolution of species phenotypes, which in turn can modify these interactions, thereby begetting eco‐evolutionary feedbacks. If indirect intransitive interactions can emerge in situ during lineage diversification, they could profoundly affect species’ phenotypic diversity, temporal stability, and subsequent diversification rates. We address these questions by investigating the conditions under which indirect intransitive competition can emerge from a lineage diversifying in sympatry. We use an adaptive dynamics model to study the ecological and evolutionary properties of this lineage under different scenarios where competition for resources between phenotypes varies in strength and (a)symmetry. Results show that weak‐intransitive competition can emerge during the sympatric diversification of a single lineage. “Weak‐intransitivity” here refers to situations where species interactions are not perfectly transitive, that is, there is no strict hierarchy in species competitive abilities. The strength of such weak‐intransitivity increases when the competition between phenotypes increases in strength and asymmetry. The strength of intransitivity also correlates with other system properties. We notably found that the strength of intransitivity increases with the number of phenotypes, and that greater intransitivity correlates with the evolution of greater functional trait divergences between phenotypes, greater resistance to invasion by new phenotypes but lower resistance to disturbances as well as slower evolutionary rates. Synthesis. This theoretical exploration of the evolution of intransitive competition provides the first formal bridge between the ecological and evolutionary aspects of intransitive competition. We show that, when competitive interactions are strong enough, weak‐intransitive competition is more likely to emerge through adaptive diversification than from a random community assembly. Intransitive competition is, therefore, not only restricted to between‐species interactions but can also function as a regulator of diversification within species, thereby affecting lineage functional diversity, and ecological and evolutionary stability.

Responses of biotic interactions of dominant and subordinate species to decadal warming and simulated rotational grazing in Tibetan alpine meadow.

Warming increases competition among plant species in alpine communities by ameliorating harsh environmental conditions, such as low temperatures. Grazing, as the main human activity, may mitigate the effect of warming, as previously reported. However, it is critical to refine the effects of warming on biotic interactions among species, for example, by taking the competitive ability of species into consideration. Based on a 10-year warming and grazing experiment in a Tibetan alpine meadow, we evaluated interspecific biotic interactions of dominant and subordinate species, using the approach of interspecific spatial associations. Warming significantly increased competition between subordinate and dominant species as well as among subordinate species, but not among dominant species. Moreover, facilitation of dominant-subordinate species also increased under warming. Simulated rotational grazing had similar effects to warming, with increasing interspecific competition. Our results show that, when studying the effects of warming on biotic interactions among species, it is necessary to characterize different species pairs relative to their competitive ability, and that simulated rotational grazing does not mitigate the effects of warming in the long term. Our results also provide evidence that the spatial pattern of species is a critical mechanism in species coexistence.

Maternal experience and soil origin influence interactions between resident species and a dominant invasive species.

Invasive species dominance in invaded communities may not be long-lasting due to regulatory processes, such as plant-soil feedbacks and neighboring species adaptation. Further, the change in species competitive ability may be contingent upon neighbor identity (i.e., specialized response) or consistent across neighbors (i.e., generalized response). Specialized responses can facilitate overall coexistence, while generalized responses may result in competitive exclusion. We set up a greenhouse experiment to test, in three species, the effect of soil conditions (non-invaded vs. invaded soil) and maternal experience (offspring of maternal plants from invaded vs. non-invaded areas) on species competitive ability against the invader Bromus inermis and conspecifics. If changes in species competitive ability against B. inermis were also evident when interacting with conspecifics, it would suggest a generalized increased/decreased competitive ability. Maternal experience resulted in reduced suppression of B. inermis in the three species and no change in tolerance. On the other hand, tolerance to B. inermis was enhanced when plants grew in soil from invaded areas, compared to non-brome soil. Importantly, both the decreased suppression due to maternal experience with B. inermis and the increased tolerance in invaded soil appear to be invader specific, as no such effects were observed when interacting with conspecifics. Specialized responses should facilitate coexistence, as no individual/species is a weaker or stronger competitor against all other neighbors or under all local soil conditions. Further, the negative plant-soil feedback for B. inermis should facilitate native species recovery in invaded areas and result in lower B. inermis performance and dominance over time.

Effects of species and soil‐nitrogen availability on root system architecture traits – study on a set of weed and crop species

AbstractBetter managing crop : weed competition in cropping systems while reducing both nitrogen and herbicide inputs is a real challenge that requires a better understanding of crop and weed root architecture in relation to soil‐nitrogen availability. An original approach was used which considered the parameters of a simulation model of root architecture as traits to analyse (a) the interspecific diversity of root system architecture, and (b) its response to soil‐nitrogen availability. Two greenhouse experiments were conducted using three crop and nine weed species grown at two contrasted concentrations of soil‐nitrogen availability. Plant traits were measured to characterise both overall plant growth and root architecture, with a focus on primary root emergence, root elongation and branching. The studied root traits varied among species (from a twofold to a fourfold factor, depending on the trait), validating their use as indicators to analyse the interspecific variability of root architecture. The largest interspecies differences were for two traits: ‘maximal apical root diameter’ and ‘interbranch distance’ (distance between two successive laterals on the same root). Conversely, most of the studied root traits varied little with soil‐nitrogen availability (from no variation to a 1.1‐fold factor, depending on the trait) even though soil‐nitrogen availability varied with a 17‐fold factor and impacted the overall shoot and root biomass. So, the root traits used in this article are stable whatever soil‐nitrogen availability. As they reflect processes underlying root system architecture, this low effect of nitrogen suggests that the rules governing root architecture are little affected by plant nitrogen status and soil‐nitrogen availability. We propose that the determinants of differences in root system architecture between soils with contrasted nitrogen availability mainly originate from differences in the amount of carbon allocated to and within the root system. Characterising each plant species by a combination of root traits gave insights regarding the potential species competitive ability for soil resources in agroecosystems.

Using a forest dynamics model to link community assembly processes and traits structure

Summary Trait‐based approaches have been increasingly used to understand the role of environmental and biotic filters on species assembly. However, our understanding of the relationships between traits and community assembly processes remain limited. Indeed, various assembly processes may lead to similar functional patterns, and the effects of a given process may vary with the considered traits. Especially, competition can result in trait divergence or convergence depending on whether the trait is related to niche differences or to species’ competitive abilities. In this study, we used a process‐based forest gap‐model to explore the effects of environmental and biotic assembly processes on the functional diversity of tree communities along a productivity gradient of 11 sites across central Europe. In a simulation experiment, we (i) disentangled the effects of environmental and biotic filtering on community structure, and (ii) tested whether competition resulted in trait divergence or convergence. Our results confirmed the expected decrease in species richness with decreasing site fertility. We detected environmental filtering for traits related to both species environmental requirements and species competitive ability, highlighting that environmental trait filtering can affect all aspects of tree life‐history strategies. We observed convergence of traits related to growth and light capture resulting from competition for light, suggesting that tree species assembly is mainly driven by differences in competitive abilities. Additionally, the observed trait convergence was stronger in more productive sites than in less fertile ones, reflecting the impact of environmental conditions on competitive interactions. Synthesis. Our study shows that process‐based forest gap‐models can help to test whether functional traits composition reveal the signature of community assembly processes. This process‐based approach challenges the classical view on the links between traits and mechanisms driving community assembly. A lay summary is available for this article.

Coexistence, association and competitive ability of Quercus petraea and Quercus robur seedlings in naturally regenerated mixed stands

In most mixed-species forestry systems, regeneration is a critical step for individual tree survival and species coexistence. Species coexistence is driven by the fine-scale spatial patterns and competitive abilities of species. In naturally regenerated mixed oak (Quercus petraea and Quercus robur: QP and QR, respectively) stands, species coexistence was assessed by analysing the spatial distribution of both species and their growth responses to intra- and interspecific competition.Four sites located in North Eastern France with an established (1.4–2.8-m-high) mixed QP and QR regeneration were selected for the study. In a first step, individual seedling location was recorded along line transects to analyse the spatial distribution of the two species. Univariate pair correlation functions were used to test for spatial aggregation for each species and bivariate pair correlation functions were used to test for spatial associations between the two species. In a second step, seedlings were measured in small plots to analyse their response to local competition. Mixed linear models were used to estimate the combined effects of density, mixture, seedling size and seedling status on seedling growth.QP and QR were both highly aggregated in monospecific patches, and the two species were strongly segregated at a decametric scale. Transition zones between monospecific patches were reduced to a few meters. For both species, mixture had no effect on seedling growth. In all sites, the two species showed very similar diameter and height growth rates in response to density, mixture, seedling size and seedling status, and similar intra- and interspecific competitive abilities.Highly patchy patterns of QP and QR regeneration strongly reduce interactions between the two species and, in transition zones between monospecific patches where the two species are mixed, no species is expected to outcompete its companion species. For each species, long-term persistence at the stand scale is determined by intraspecific competition rather than by interspecific competition. At this developmental stage, the QP-QR mixture appears to be very stable and no specific silvicultural treatment is required to maintain the mixture.

The influence of evolutionary history and body size on partitioning of habitat resources by mammalian herbivores in south-eastern Australia

Habitat use is the most common dimension along which sympatric species partition resources to reduce competition. We conducted faecal pellet counts at Wilsons Promontory National Park, Victoria, to examine habitat use by an assemblage of mammalian herbivores with disparate evolutionary histories and varying body size: introduced European rabbit (Oryctolagus cuniculus) and hog deer (Axis porcinus), and native eastern grey kangaroo (Macropus giganteus), swamp wallaby (Wallabia bicolor) and common wombat (Vombatus ursinus). Overlap in habitat use was low between four pairs of species, suggesting spatial partitioning of resources to reduce the potential for interspecific competition. More generally, however, overlap in habitat use was high, particularly between native and introduced grazers. These results indicate the potential for competition if resources were limiting and suggest that assemblages of species with independent evolutionary histories have inherently less resource partitioning to facilitate coexistence than assemblages of species with common evolutionary histories. Despite evidence of high overlap in habitat use between native and introduced species at a broad scale, and variation in the competitive ability of species, coexistence was likely facilitated by niche complementarity, including temporal and fine-scale partitioning of spatial resources. There was no relationship between body size and the diversity of habitats used. In contemporary assemblages of native and introduced species, evolutionary history is likely to have a strong influence on resource partitioning.

Patterns of biomass allocation between foliage and woody structure: the effects of tree size and specific functional traits

Biomass allocation is closely related to species traits, resources availability and competitive abilities, and therefore it is often used to capture resource utilisation within plants. In this study, we searched for patterns in biomass allocation between foliage and wood (stem plus branch), and how they changed with tree size (diameter), species identity and functional traits (leaf area and specific wood density). Using data on the aboveground biomass of 89 trees from six species in a Mistbelt forest (South Africa), we evaluated the leaf to wood mass ratio (LWR). The effects of tree size, species identity and specific traits on LWR were tested using Generalised Linear Models. Tree size (diameter) was the main driver of biomass allocation, with 44.43 % of variance explained. As expected, LWR declined significantly with increasing tree diameter. Leaf area (30.17% explained variance) and wood density (12.61% explained variance) also showed significant effects, after size effect was accounted for. Results also showed clear differences among species and between groups of species. Per unit of wood mass, more biomass is allocated to the foliage in the species with the larger leaf area. Inversely, less biomass is allocated to the foliage in species with higher wood density. Moreover, with increasing diameter, lower wood density species tended to allocate more biomass to foliage and less biomass to stems and branches. Overall, our results emphasise the influence of plant size and functional traits on biomass allocation, but showed that neither tree diameter and species identity nor leaf area and wood density are the only important variables.

EFFECT OF RED DEER GRAZING ON ALPINE HAY MEADOWS: BIODIVERSITY AND MANAGEMENT IMPLICATIONS

Large mammalian herbivores are keystone species affecting the biodiversity and functioning of ecosystems, since herbivory directly influences plant species competitive ability. Thus, when managing habitats for conservation it is crucial to understand the selection patterns of large herbivores and their effect on plant diversity and assemblage. With this aim, we studied a pastoral system placed in central- eastern Alps, comparing late mowing with grazing by red deer. We found that, with high stocking rates, red deer significantly affects the species and functional composition of alpine productive pastures, mostly by competitive exclusion of subordinate species due to the spread of poorly palatable, competitive, stress-tolerant tall grasses with strong avoidance strategies. We argued that grazing by red deer with high stocking rates is harmful when acts on formerly managed meadows, while it has a positive impact on plant diversity of long-term abandoned grasslands. Our results indicated that grazing by red deer with high stoking rates hinders the spread of successional/ruderal species, but allows the establishment of competitive dominant tall grasses. Our findings also confirmed the hypothesis that the impact of red deer on grassland biodiversity follows the intermediate disturbance hypothesis.

Space resource utilisation: a novel indicator to quantify species competitive ability for light.

Species richness and productivity are two fundamental aspects of ecosystems. As a result, the relationship between species richness and productivity has been widely studied. A series of fertilisation experiments in an alpine meadow on the Tibetan Plateau were performed to study the relationship between species richness and productivity. In this paper, we present a novel indicator, i.e., space resource utilisation (SRU), which is calculated by a volume formula (Vi = hi · Si; hi = plant height of species i, Si = quadrat area × percent cover of species i). SRU more fully reflected species competitive ability for light in both horizontal and vertical dimensions compared with plant height and cover. We used this novel indicator to investigate the effects of SRU on the changes in species richness and productivity following fertilisation. We found that the SRU of the community was correlated with increasing productivity and decreasing species richness following fertilisation and was a better predictor of species richness than productivity. The changes in SRU following fertilisation vary among species. These results demonstrate that SRU can be a more useful tool in explaining plant biodiversity loss and predicting the fate of different species than each of height, cover and productivity.

Functional diversity: an overview of its history and applicability

Ecological investigations are increasingly using functional diversity in order to understand different patterns, such as species occurrence, species competitive abilities, and the influence of biological communities on ecosystem functioning. Here we provide an overview of the history and applicability of functional diversity in ecological studies. We found that the idea of functional diversity emerged many times and in distinct fields over the years. Functional diversity was conceived as an alternative classification to measure the ecological importance of species in a community, as well as a way to understand how biodiversity affects specific ecosystem functions. Gradually, new questions regarding functional traits emerged. Some examples include understanding species competitive abilities, patterns of species co-occurrence, community assembly, and the role of different traits on ecosystem functioning. The increasing use of functional-based approaches fueled the search for new metrics aiming at accurately estimating functional diversity and, consequently, categorical-based classifications of functional traits have been gradually replaced by continuous multi-trait approaches. More recently, the role of functional diversity was recognized as a key factor to maintain important functions and services of ecosystems. We present empirical evidence supporting this statement.

Light-driven host-symbiont interactions under hosts’ range shifts caused by global warming: A review

The spectrum of light has received little attention as an ecological factor and in this review we highlight the importance of a changing light environment in plant range shifts under conditions of global warming. Although distinct clinal responses to light quality have not been earlier reported, some studies have shown that northern ecotypes are more sensitive to changes in light quality. The northern light environment may significantly modify competition between plant species and within photoperiodic ecotypes, if predicted rapid range shifts of forest trees are realized. Southern photoperiodic ecotypes of forest trees migrating northward will encounter both changed light quality and a different photoperiod. Our special focus is on carbon economy and biomass partitioning between the autotrophic hosts and heterotrophic ectomycorrhizal fungal (EMF) symbionts, reciprocally dependent on each other. This applies also to the level of fungal community structure, which is assumed to be determined in part by host carbon economy. We hypothesize, that (1) Carbon allocation to roots and EMF in different host species and locally adapted photoperiodic ecotypes will respond differentially to northern light climate, especially to photoperiod and proportionally higher diffuse blue light; (2) Since carbon flux belowground may start later in northward-shifted southern populations in the autumn, also mycelial growth and reproduction in the EMF associated with southern populations could occur later. This may also lead to changes in fungal community composition; (3) EMF phenology and community composition may show different responses to changing light climate when associated with host trees of fixed or free growth pattern; and (4) Responses of EMF symbionts associated with locally adapted host populations vary, possibly leading to changes in EMF communities. We also discuss potential experimental approaches mimicking range shift conditions in terms of light quality due to global warming and compare reaction norms in key traits between southern and northern populations and species. Further, we exemplify how data obtained from experimental studies may be used for modelling of host plant and symbiont growth, which may in turn affect species competitive ability and distribution.