Shifts In Functional Traits Research Articles

Examining functional responses of ant communities to fire in Northwestern African afforested landscapes

In fire prone-regions, forest fires play a vital role in shaping animal communities, particularly for groups like ants strongly associated with vegetation and soil. While prior works on the impact of forest fires on biodiversity focused on taxonomic responses, there is a growing interest on exploring functional responses. This study assesses the taxonomic and functional response of ant species to fire in afforested landscapes (pine plantations) in northern Morocco. These landscapes are widely recognized as suboptimal for many taxonomic groups, suggesting a positive responses of ant communities to fire. Our specific hypotheses were: (1) increasing post-fire openness enhances the richness and abundance of ant species in burnt plots, and (2) fire induces shifts in functional traits within ant communities influencing their composition, potentially favoring species with adaptations suited to the post-fire environment. Our results reveal that fire altered the taxonomic (winner and loser ant species) and functional composition (higher functional richness in burnt plots) of ant communities. Burnt areas harbored a greater abundance of ant species adapted to open habitats, characterized by ground nesting habits, ground foraging, and a preference for readily available resources like seeds. In contrast, unburnt plots hosted species ideally adapted to denser vegetation, utilizing arboreal nesting and foraging strategies and resource niches in the canopy. Overall, we found that fire significantly shapes ant communities by promoting the arrival of species tolerant of open areas and capable of exploiting new available resources in the post-fire habitat.

Functional diversity buffers biomass production across variable rainfall conditions through different processes above‐ versus below‐ground

Abstract Understanding precipitation controls on functional diversity is important in predicting how change in rainfall patterns will alter plant productivity in the future. Trait‐based approaches can provide predictive knowledge about how certain species will behave and interact with the community. However, how functional diversity relates to above‐ and below‐ground biomass production in variable rainfall conditions remains unclear. Here, we tested the role of mass ratio and niche complementarity hypotheses in shaping above‐ and below‐ground biomass–functional diversity relationships in seasonal drought. We implemented a fully crossed experiment that manipulated drought timing (fall dry, spring dry, consistent dry and ambient rainfall) and community composition (grass‐dominated, forb‐dominated and mixed grass–forb) in a California annual grassland. Plant communities with mixed functional groups showed higher above‐ and below‐ground biomass than either the grass‐ or forb‐dominant communities. We found divergent functional diversity–biomass relationships for above‐ and below‐ground biomass. Above‐ground biomass decreased with community weighted means (CWMs) of specific leaf area (SLA) and height, supporting the mass ratio hypothesis, which posits that dominant species with specific traits drive biomass production of the community. Below‐ground biomass showed no evidence of either mass ratio hypothesis or niche complementarity. While biomass was largely unaffected by the timing of drought in one season, we found community‐wide functional trait shifts in response to rainfall treatments. Above‐ground traits shifted to higher SLA in consistent dry compared to ambient. Below‐ground traits shifted to longer, finer and denser roots in fall and consistent dry, and shorter and coarser roots in spring dry. Functional diversity buffered biomass production by enabling shifts in above‐ and below‐ground functional traits across variable rainfall conditions. Read the free Plain Language Summary for this article on the Journal blog.

Urbanization causes shifts in the functional traits and foraging activity, and alters food particle size preference and biomass removal of urban-dwelling ants

Urbanization may lead to changes in assemblage and result in shifts in trait distribution from natural habitats to highly urbanized habitats. The shift in functional traits can affect ecosystem functions in urban areas. This study explored the foraging period of ants over 72 h and determined the relationship between the behavioral, morphological, and physiological traits of local foragers ants and environmental conditions in urban and forest sites. In addition, this study examined the ants’ ecosystem functions and compared it with that of their forest counterparts. Our results revealed that the foraging period of ants (i.e., Cardiocondyla sp.1, Monomorium chinense, Paratrechina longicornis, Pheidole megacephala, and Solenopsis sp.1) in urban areas peaked between 0900 and 1500 and that of some ants (i.e., Carebara diversa, P. megacephala, Pheidole fervens, Plagiolepis longwang, and Nylanderia sp.1) in forest areas was constant over time. For urban ants, a weak correlation was observed between foraging period and body size traits (i.e., Weber’s length and head width). This finding indicates that the major factor underlying the change in the foraging period might not be related to body size. Rather, the change may be attributed to synchronization between food availability and human activity (waste disposal; i.e., between 0900 and 1800). The shift in the functional traits of ants affects ecosystem functions in urban areas. In urban areas, although only one predatory ant species (P. megacephala) was sampled, its activity density was high. Most of these individuals were active during the daytime, indicating that the predatory behavior of ants in the novel urban environment has decreased temporally and is limited to the daytime. Urban ants tended to choose smaller food particles, whereas forest ants preferred larger food particles and had a twofold higher food removal rate.

Shifts in functional traits and interactions patterns of soil methane-cycling communities following forest-to-pasture conversion in the Amazon Basin.

Deforestation threatens the integrity of the Amazon biome and the ecosystem services it provides, including greenhouse gas mitigation. Forest-to-pasture conversion has been shown to alter the flux of methane gas (CH4 ) in Amazonian soils, driving a switch from acting as a sink to a source of atmospheric CH4 . This study aimed to better understand this phenomenon by investigating soil microbial metagenomes, focusing on the taxonomic and functional structure of methane-cycling communities. Metagenomic data from forest and pasture soils were combined with in situ CH4 fluxes and soil edaphic factors measurements and analysed using multivariate statistical approaches. We found a significantly higher abundance and diversity of methanogens in pasture soils. As inferred by co-occurrence networks, these microorganisms seem to be less interconnected within the soil microbiota in pasture soils. Metabolic traits were also different between land uses, with increased hydrogenotrophic and methylotrophic pathways of methanogenesis in pasture soils. Land-use change also induced shifts in taxonomic and functional traits of methanotrophs, with bacteria harboring genes encoding the soluble form of methane monooxygenase enzyme (sMMO) depleted in pasture soils. Redundancy analysis and multimodel inference revealed that the shift in methane-cycling communities was associated with high pH, organic matter, soil porosity, and micronutrients in pasture soils. These results comprehensively characterize the effect of forest-to-pasture conversion on the microbial communities driving the methane-cycling microorganisms in the Amazon rainforest, which will contribute to the efforts to preserve this important biome.

Demographic trade-offs and functional shifts in a hurricane-impacted tropical forest.

Understanding shifts in the demographic and functional composition of forests after major natural disturbances has become increasingly relevant given the accelerating rates of climate change and elevated frequency of natural disturbances. Although plant demographic strategies are often described across a slow-fast continuum, severe and frequent disturbance events influencing demographic processes may alter the demographic trade-offs and the functional composition of forests. We examined demographic trade-offs and the shifts in functional traits in a hurricane-disturbed forest using long-term data from the Luquillo Forest Dynamics Plot (LFPD) in Puerto Rico. We analysed information on growth, survival, seed rain and seedling recruitment for 30 woody species in the LFDP. In addition, we compiled data on leaf, seed and wood functional traits that capture the main ecological strategies for plants. We used this information to identify the main axes of demographic variation for this forest community and evaluate shifts in community-weighted means for traits from 2000 to 2016. The previously identified growth-survival trade-off was not observed. Instead, we identified a fecundity-growth trade-off and an axis representing seedling-to-adult survival. Both axes formed dimensions independent of resprouting ability. Also, changes in tree species composition during the post-hurricane period reflected a directional shift from seedling and tree communities dominated by acquisitive towards conservative leaf economics traits and large seed mass. Wood specific gravity, however, did not show significant directional changes over time. Our study demonstrates that tree demographic strategies coping with frequent storms and hurricane disturbances deviate from strategies typically observed in undisturbed forests, yet the shifts in functional composition still conform to the expected changes from acquisitive to conservative resource-uptake strategies expected over succession. In the face of increased rates of natural and anthropogenic disturbance in tropical regions, our results anticipate shifts in species demographic trade-offs and different functional dimensions.

Vegetation Height as the Primary Driver of Functional Changes in Orthopteran Assemblages in a Roadside Habitat.

Simple SummaryThis paper reports the results of a field research that investigates functional changes in grasshopper and cricket (Orthoptera) assemblages with distance from a major road (at 10, 25, 50, 100 and 500 m). Expanding on a previous study that adopted a species-based approach to the same subject, in order to gain a different perspective on road-associated dynamics of orthopteran assemblages with potential implications for ecosystem functioning, we aimed for the following: (1) to test how motorway proximity affects functional diversity of orthopteran assemblages and functional traits related to mobility, feeding guild, lifestyle and moisture preference; and (2) to assess the relationships between trait composition and road-influenced environmental factors. We recorded a significant increase in functional diversity and the occurrence of omnivorous and shrub-dwelling orthopterans, and a decrease in larger ground-dwelling orthopterans at sites close to the motorway. Road-induced changes in vegetation height were identified as the primary driver of these changes. Our findings contribute to a more thorough understanding of the links between road-associated changes in vegetation cover and insect community assembly in grassland habitats.Exhibiting manifold ecological impacts on terrestrial biota, roads have become a major driver of environmental change nowadays. However, many insect groups with high indication potential, such as grasshoppers and crickets (Orthoptera), have been largely neglected in road ecology research from a functional perspective. Using two complementary sampling methods, we have investigated the spatial dynamics of functional diversity and six functional traits in orthopteran assemblages, with respect to motorway proximity and the associated environmental factors, in a grassland habitat in the Lika region, Croatia. This research shows, for the first time, that road proximity can facilitate an increase in the functional diversity of orthopteran assemblages, with shifts in functional traits related to mobility, feeding habits and lifestyle being primarily driven by changes in vegetation height. Our findings also suggest that our ability to detect road-related patterns depends on the choice of a diversity measure and sampling method, since different components of orthopteran assemblages (plant-dwelling vs. ground-dwelling) exhibit different functional responses to road proximity.

Variation in cloud immersion, not precipitation, drives leaf trait plasticity and water relations in vascular epiphytes during an extreme drought.

Epiphytes are abundant in ecosystems such as tropical montane cloud forests where low-lying clouds are often in contact with vegetation. Climate projections for these regions include more variability in rainfall and an increase in cloud base heights, which would lead to drier conditions in the soil and atmosphere. While recent studies have examined the effects of drought on epiphytic water relations, the influence that atmospheric moisture has, either alone or in combination with drought, on the health and performance of epiphyte communities remains unclear. We conducted a 10-week drought experiment on seven vascular epiphyte species in two shadehouses, one with warmer and drier conditions and another that was cooler and more humid. We measured water relations across control and drought-treatment groups and assessed functional traits of leaves produced during drought conditions to evaluate trait plasticity. Epiphytes exposed to drought and drier atmospheric conditions had a significant reduction in stomatal conductance and leaf water potential and an increase in leaf dry matter. Nonsucculent epiphytes from the drier shadehouse had the greatest shifts in functional traits, whereas succulent epiphytes released stored leaf water to maintain water status. Individuals in the drier shadehouse had a substantial reduction in performance, whereas drought-treated individuals that experienced cloud immersion displayed minimal changes in water status. Our results indicate that projected increases in the cloud base height will reduce growth and performance of epiphytic communities and that nonsucculent epiphytes may be particularly vulnerable.

Interspecific interactions alter plant functional strategies in a revegetated shrub-dominated community in the Mu Us Desert, China.

Previous studies investigating plant-plant interactions have focused on plant growth, context dependence and shifts in interactive outcomes. However, changes in functional traits in the context of interactions have been inadequately explored; few studies have focused on the effects of interactions on the plasticity of functional strategies. We conducted a 4-year removal experiment for the xeric shrub Artemisia ordosica and perennial graminoids (PGs) in the Mu Us Desert, northern China. Soil nutrient content, biomass and 12 functional traits related to plant morphology and nutrient status were measured for the shrub species and a dominant PG species (i.e. Leymus secalinus) in the presence and absence of shrubs and PGs. Shrubs affected the functional traits of L. secalinus, reducing leaf dry matter content and increasing plant height, which probably promoted the functional strategy of L. secalinus towards a more resource-acquisitive and competitive strategy. In contrast, when the shrubs were affected by PGs, they shifted towards a resource-conservative and stress-tolerative strategy, by increasing leaf dry matter content and decreasing specific leaf area. Moreover, the shrub species relied more on internal nutrient recycling (higher nitrogen resorption efficiency) rather than on external nitrogen uptake under nitrogen competition; instead, L. secalinus tended to exhibit higher external nitrogen uptake from soil during nitrogen shortages. This study indicated that the functional strategies and nutrient cycling of the shrub species and the dominant PG were altered by each other. The shifts in functional traits may help plants to coexist in the community for a relatively long time. Our findings highlighted that interspecific interactions alter plant functional strategies and provided new insights into community assembly and succession mechanisms in a revegetated shrubland for ecological restoration of drylands.

Crossing the Divide: An Exploration of Functional Traits in Ferns that Grow Across Terrestrial, Epipetric, and Epiphytic Habitats

Plants are characterized by their marked plasticity and ability to alter their functional biology to partition ecological niches. However, there are limits to functional trait exploration especially in complex and stressful habitats. Highly specialized traits may control a species ability to explore within and across habitats. Such may be especially true of epiphytes, whose array of unique traits may constrain their ability to cross establish in epiphytic and terrestrial habitats. In the case of ferns, there are few reported examples of species that can grow across these habitats with regularity. However, this study reports and explores species that exhibit great ecological flexibility growing across a wide range of habitats and growth forms. Specifically, we examine species that grow as 1) terrestrially rooted and epiphytic individuals, 2) nest and non-nest-forming epiphytes; and nest-forming terrestrially rooted individuals, and 3) species that grow as terrestrial, epiphytic, and epipetric individuals. We use natural abundance foliar stable isotope ratios (SIR) of N15 and C13, and %N, to explore intraspecific variation in mineral nutrition and water relations across and within niches. Our results reveal the 1) unreported ability of some species to grow across the epiphytic/terrestrial divide, 2) surprising ability of some species to explore these habitats with little to no shift in functional traits; 3) a potentially new function for the nest in nest-forming epiphytes. Finally, our work highlights the need to consider intraspecific trait variation more carefully when studying ferns that occur across a wide range of habitats.

The Importance of Forest-Nonforest Transition Zones for Avian Conservation in a Vegetation Disturbance Gradient in the Northern Neotropics

Tropical landscape connectivity and matrix quality near large stands of primary forest are important factors that dictate biodiversity trends in communities. Suitable matrix management surrounding primary forest may help conserve biodiversity, but areas with poor matrix management need attention to determine their long-term viability to support native levels of biodiversity. We examined variations in species and functional diversity and community composition using point-count surveys placed in preserved (PRES), transition (TRA), and disturbed (DIS) areas according to percent land cover of forest and cattle pasture along a human disturbance gradient in the northern Neotropics during an 8 month period from 2019–2020. We expected the gradient of human disturbance to drive species diversity loss of forest specialists from PRES to DIS, resulting in changes to functional diversity and community composition. We detected 228 species overall, with 163 in PRES (40 unique species), 159 in TRA (9 unique species), and 152 in DIS (20 unique species). TRA supported an avian community with shared aspects of PRES and DIS, leading to the highest functional, Shannon (85.8 estimated species), and Simpson (57.9 estimated species) diversity. Higher diversity of open-area specialists in TRA and DIS has led to shifts in functional traits and different species and functional community compositions relative to PRES. Land management in Neotropical human-modified landscapes must focus on increasing habitat quality in remnant forest fragments in the vicinity of large stands of primary forest to prevent species and ecosystem service loss from preserved areas and the distancing of local community compositions.

The effects of human disturbance on the species composition, species diversity and functional diversity of a Miombo woodland in northern Malawi

AbstractAnthropogenic disturbances have serious impacts on ecosystems across the world. Understanding the effects of disturbance on woodlands, especially in regions where local people depend on these natural resources, is essential for sustainable natural resource management and biodiversity conservation. In this study, we evaluated the effects of anthropogenic disturbance, specifically selective logging of Brachystegia floribunda, on woodlands by comparing species composition, species diversity and functional diversity of woody plants between disturbed and undisturbed woodlands. We combined species data and functional trait data for leaves, fruits and other traits related to resource and disturbance responses to calculate functional indices (functional richness, evenness and divergence) and community‐weighted means of each trait. Shifts in taxonomic species composition were analysed using nonmetric multi‐dimensional scaling. Species composition differed significantly between disturbed and undisturbed woodlands. Tree density was greater in disturbed woodlands, whereas evenness, functional evenness and functional divergence were greater in undisturbed woodlands. In terms of forest cover, selective logging of B. floribunda appeared to have little impact on Miombo woodlands, but some shifts in functional traits, such as the shift from a deciduous to evergreen phenology, may increase the vulnerability of these ecosystems to environmental change, especially drought.

Soil fungal community composition and functional similarity shift across distinct climatic conditions.

A large part of ecosystem function in woodland systems depends on soil fungal communities. However, global climate change has the potential to fundamentally alter these communities as fungal species are filtered with changing environmental conditions. In this study, we examined the potential effects of climate on host-associated (i.e. tree-associated) soil fungal communities at climatically distinct sites in the Tehachapi Mountains in California, where more arid conditions represent likely regional climate futures. We found that soil fungal community composition changes strongly across sites, with species richness and diversity being highest at the most arid site. However, host association may buffer the effects of climate on community composition, as host-associated fungal communities are more similar to each other across climatically distinct sites than the whole fungal community. Lastly, an examination of functional traits for ectomycorrhizal fungi, a well-studied guild of fungal mutualist species, showed that stress-tolerant traits were more abundant at arid sites than mesic sites, providing a mechanistic understanding of these community patterns. Taken together, our results indicate that fungal community composition will likely shift with future climate change but that host association may buffer these effects, with shifts in functional traits having implications for future ecosystem function.

Urban bumblebees are smaller and more phenotypically diverse than their rural counterparts.

With urbanization identified as being one of the key drivers of change in global land use, and the rapid expansion of urban areas world-wide, it is relevant to evaluate how novel ecological conditions in cities shape species functional traits, which are essential for how species interact with their environments and with each other. Despite the many comparative studies on organisms living in urban and non-urban areas, our knowledge on species responses to urban environments remains limited. For one, much of the ecological research has assumed that the environment changes in a linear fashion from the city core to the city edges, whereas in reality the environments within the cities are highly heterogeneous. Furthermore, studies on species responses to these highly variable ecosystems are often based on interspecific mean trait values, which ignore the potential for high levels of intraspecific variation among individuals in key functional traits. The current study investigated intraspecific functional trait differences for four functional traits associated with body size, mobility and resource selection among rural and urban populations of two common bumblebee species, Bombus pascuorum and Bombus lapidarius, in urban centres and adjacent rural areas in Switzerland. We document shifts in functional traits towards smaller individuals and higher multidimensional trait variation in urban populations compared to rural conspecifics of both species. This shows that urban individuals for both species are on average smaller sized but populations are distinctively different from rural population by increasing their trait richness and diversifying their trait combinations. In addition, we found bimodality in tongue length within urban B.pascuorum populations. Our results suggest that urban and rural populations possibly experience differential selection pressures resulting in trait differences across and among populations. We argue that variations in the respective foraging landscapes in cities leads to smaller sized but phenotypically more diverse populations, and drive functional trait divergence.

Island disharmony revisited using orchids as a model group.

One central concept in island biology is that island assemblages form subsets of the mainland species pool, being disproportionately rich or poor in certain taxonomic groups. This unbalanced composition, termed 'disharmony', is generally explained using a taxon-centred approach, linking the over- or under-representation of taxa to their colonisation abilities. However, islands may also harbour 'functionally' disharmonic flora, being disproportionately rich or poor in species with certain traits, which may offer greater insights into the processes driving island colonisation. Here, we use orchids as a model to illustrate key processes involved in the formation of functionally disharmonic island floras, including filtering effects (for example biotic interactions), and speciation. Our synthesis is based on a comprehensive orchid dataset of 27637 species and combines both a literature review and simple exploratory analyses to show that orchids are significantly under-represented on islands relative to mainland regions and that insular orchids display shifts in functional traits, from the shortening of nectar spurs to facilitate ornithophily to changes in colour associated with generalist insect pollinators. We highlight that taxa are simply coarse proxies and that we need to consider species traits and interactions to gain a full understanding of the processes constraining plant assembly on islands.

Raised atmospheric CO2 levels affect soil seed bank composition of temperate grasslands

AbstractQuestionsSoil seed banks buffer plant populations against environmental variability. But environmental changes can have profound impact on them. Several studies addressed the effect of climate change on aboveground vegetation, but studies on changes in the seed bank are rare. Thus, we studied the seed bank of a temperate grassland at a long‐term FACE (Free‐Air Carbon dioxide Enrichment) site, with the following questions: (a) Are there general differences in the species composition between aboveground vegetation and seed bank; (b) what are the impacts of elevated CO2 (eCO2) on seed density and species composition of the seed bank; and (c) are there differences in the functional traits of the seed bank species under eCO2 versus ambient CO2 (aCO2)?LocationTemperate grassland, Gießen, Germany.MethodThirty soil cores were taken in six FACE rings. Emerging seedlings were identified to species level after germination and aboveground vegetation was sampled. From the seed bank data, we derived diversity measures and weighted means of species traits, e.g., seed longevity and regeneration type, and compared eCO2 (+20% CO2 above ambient conditions) with aCO2 treatment.ResultsNonmetric multidimensional scaling ordination revealed a clear separation between seed bank and aboveground vegetation but no clear CO2 effect. Analyses revealed higher seed densities under eCO2. Species diversity and Shannon diversity were not significantly affected. Evenness decreased significantly under eCO2. There are shifts in functional traits of seed bank species. Seed density of long‐term‐persistent species increased, while short‐term‐persistent species decreased. Seed densities of species with generative reproduction increased under eCO2, while numbers of species with vegetative reproduction decreased.ConclusionThe observed trait compositions of the seed bank under eCO2 indicate that species relying on generative reproduction and production of long‐term‐persistent seeds have a competitive advantage under eCO2. The changes in the plant communities described above may lead to profound changes in the supply of grassland ecosystem services.

Using museum specimens to track morphological shifts through climate change.

Museum specimens offer a largely untapped resource for detecting morphological shifts in response to climate change. However, morphological shifts can be obscured by shifts in phenology or distribution or sampling biases. Additionally, interpreting phenotypic shifts requires distinguishing whether they result from plastic or genetic changes. Previous studies using collections have documented consistent historical size changes, but the limited studies of other morphological traits have often failed to support, or even test, hypotheses. We explore the potential of collections by investigating shifts in the functionally significant coloration of a montane butterfly, Colias meadii, over the past 60 years within three North American geographical regions. We find declines in ventral wing melanism, which correspond to reduced absorption of solar radiation and thus reduced risk of overheating, in two regions. However, contrary to expected responses to climate warming, we find melanism increases in the most thoroughly sampled region. Relationships among temperature, phenology and morphology vary across years and complicate the distinction between plastic and genetic responses. Differences in these relationships may account for the differing morphological shifts among regions. Our findings highlight the promise of using museum specimens to test mechanistic hypotheses for shifts in functional traits, which is essential for deciphering interacting responses to climate change.This article is part of the theme issue 'Biological collections for understanding biodiversity in the Anthropocene'.

Progressively excluding mammals of different body size affects community and trait structure of ground beetles

Mammalian grazing induces changes in vegetation properties in grasslands, which can affect a wide variety of other animals including many arthropods. However, the impacts may depend on the type and body size of these mammals. Furthermore, how mammals influence functional trait syndromes of arthropod communities is not well known.We progressively excluded large (e.g. red deer, chamois), medium (e.g. alpine marmot, mountain hare), and small (e.g. mice) mammals using size‐selective fences in two vegetation types (short‐ and tall‐grass vegetation) of subalpine grasslands. We then assessed how these exclusions affected the community composition and functional traits of ground beetles (Coleoptera, Carabidae), and which vegetation characteristic mediated the observed effects.Total carabid biomass, the activity densities of carabids with specific traits (i.e. small eyes, short wings), the richness of small‐eyed species and the richness of herbivorous species were significantly higher when certain mammals were excluded compared to when all mammals had access, regardless of vegetation type. Excluding large and medium mammals increased the activity density of herbivorous carabid species, but only in short‐grass vegetation. Similarly, excluding large mammals (ungulates) altered carabid species composition in the short‐, but not in the tall‐grass vegetation. All these responses were related to aboveground plant biomass, but not to plant Shannon diversity or vegetation structural heterogeneity.Our results indicate that changes in aboveground plant biomass are key drivers of mammalian grazers’ influence on carabids, suggesting that bottom–up forces are important in subalpine grassland systems. The exclusion of ungulates provoked the strongest carabid response. Our results, however, also highlight the ecological significance of smaller herbivorous mammals. Our study furthermore shows that mammalian grazing not only altered carabid community composition, but also caused community‐wide functional trait shifts, which could potentially have a wider impact on species interactions and ecosystem functioning.

Functional trait shifts after disturbance reveal broad‐scale variability in temperate forest regional recruitment processes

AbstractQuestionDecreased above‐ground biomass and subsequent changes in resource availability exert a strong influence on seedling recruitment in post‐disturbance forests. Ecological trade‐offs underlie recruitment processes, as species vary in resource allocation, dispersal and stress tolerance strategies. Functional traits that indicate resource acquisition–conservation trade‐offs include leaf N content, wood density, maximum height, shade tolerance and drought tolerance, while seed mass can indicate species’ dispersal strategies. This study looks for generality in post‐disturbance trait responses, and asks whether these responses are additionally constrained or amplified by disturbance characteristics, climate and ecological provinces.LocationEastern US temperate forests.MethodsI leveraged a longitudinal, continental‐scale database of post‐disturbance forests to examine recruitment dynamics. Using multivariate, hierarchical Bayesian models, I examined how disturbance affects the traits of seedling layer communities where recruitment dynamics should be most evident, and compared this to undisturbed communities. I also examined how the traits underlying trade‐off axes varied across disturbance properties, ecological provinces and climatic gradients.ResultsAll traits except leaf N showed significant, study‐wide shifts in disturbed communities consistent with expectations of post‐disturbance stands. In undisturbed plots, all traits had significant shifts in the opposite direction to those observed in disturbed plots, except leaf N and drought tolerance, where no change was observed. Disturbance severity increased the magnitude of response of several, but not all, trait responses in disturbed plots. The traits that had significant shifts were idiosyncratic across ecological provinces, indicating unique processes influencing disturbance responses across the system. Moreover, while climate strongly correlated with all traits prior to disturbance in the initial sampling periods, it was not correlated with disturbance responses.ConclusionsThis study demonstrates general, biome‐wide trait shifts towards resource acquisition and bet‐hedging dispersal strategies in post‐disturbance forest seedling communities. At finer spatial scales, the traits underlying these trade‐offs varied, indicating that disturbance‐dependent species differ in life‐history strategies across the system. This variation across ecological provinces appears independent of temperature and precipitation, suggesting that unmeasured abiotic or biotic variables influence recruitment. Seedling recruitment is critical in shaping future adult tree communities, and this study reveals large‐scale contingencies in trait patterns associated with this process.

Shift in functional traits along soil fertility gradient reflects non-random community assembly in a tropical African rainforest

Background and aims – There is increasing recognition that plant traits mediate environmental influenceon species distribution, justifying non-random community assembly. We studied the influence of local scale edaphic factors on the distribution of functional traits in a tropical rainforest of Cameroon with the aim to find correlations between the main edaphic gradient and community functional trait metrics (weighted mean trait, functional divergence and intraspecific variation). Methods – Within the Korup Forest Dynamics Plot (50 ha), we randomly selected 44 quadrats of 0.04 ha each, collected soils and analysed 11 topography and soil variables. Leaves were harvested from all 98 tree species found in the quadrats to calculate community trait metrics [quadrat-level weighted mean (qk) and functional divergence (FDivk)] for leaf area (LA), specific leaf area (SLA), leaf phosphorus (LPC), leaf nitrogen concentration (LNC) and nitrogen to phosphorus ratio (N:P ratio). We examined relationships between the main edaphic gradient with qk, with FDivk and with intraspecific variation and interpreted correlations as the effects of abiotic filtering and competitive interaction. Key results – Soil fertility was the main edaphic gradient and was significantly correlated with qk for LPC, LNC and LA and with FDivk for LPC, N:P ratio, LA and SLA, confirming the influence of abiotic filtering and competitive interaction by the soil fertility gradient, respectively. For a given trait, quadrats were either over-dispersed or under-dispersed, accounting for 7–33 % of non-random trait distribution along the soil fertility gradient. Trends in intraspecific traits variation were consistently lower than quadrat-level mean traits along the soil fertility gradient. Conclusions – This study demonstrates the influence of soil fertility gradient on local scale community trait distribution and its contribution to non-random community assembly.

Temporal shifts in functional traits of the fish community in Terminos Lagoon (Mexico) in three periods (1980, 1998 and 2011)

The trophic structure of the fish community ecosystem in the Terminos Lagoon (southern Gulf of Mexico) has shown a range of functional changes. The description of the heterogeneity of functional traits in a biological community allows the identification of the relevant functions in an ecosystem. An analysis was conducted of the functional traits (trophic level, reproductive and trophic guild, habitat, estuary use, essential habitat, salinity tolerance, body shape, mouth type, caudal fin type, and maximum length) of the fish community of the lagoon for three different years (1980, 1998 and 2011). We developed a new index to analyze the variation of functional diversity called the functional traits diversity index (FADI). This index takes into account the abundance of traits and emphasizes less common traits (i.e., those that are less redundant). The functional redundancy was different in the three periods studied. The FADI value for 1998 was the highest and was outside of the expected probability distribution, indicating a greater abundance of species with unique functional traits. A principal components analysis was performed to assess the relative contribution of functional traits to the overall variance of functional diversity over the three periods. We found that the trophic level, body shape, and mouth type were the most influential traits in the functional diversity changes. The environmental changes were correlated with the variability of the functional structure. Depth was the most influential environmental variable in the principal component analysis. The results indicate a reorganization of the functional structure of the fish community in the Terminos Lagoon. The FADI was helpful in explaining these changes observed throughout the three periods studied.