Lower Functional Diversity Research Articles

Functional susceptibility of tropical forests to climate change.

Tropical forests are some of the most biodiverse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forests' functional diversity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional diversity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits sampled from 2,461 individual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional diversity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally diverse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional diversity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional diversity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.

Increasing abundance of an invasive C4grass is associated with larger community changes away than at home

AbstractAimWe evaluated stands of the invasive grass,Sporobolus cryptandrusin its native North American range and its non‐native European range, where it is a recent invader. Our aim was to reveal how the species’ increasing abundance affects functional diversity and the ecosystem service‐provisioning capacities of plant communities in both ranges.LocationSand grasslands in the Kiskunság, Hungary and in Montana, USA.MethodsAll vascular plant species and their relative abundances were recorded in a stratified random manner in 1 m × 1 m plots in each range, using the following cover categories ofSporobolusas strata: 1%–25%, 26%–50%, 50%–75%, and 75%–100%. The functional characteristics of the plant communities in the two continents were compared. We performed comparisons of the communities both with and without includingSporobolus.ResultsIncreasingSporoboluscover resulted in a lower functional diversity and species richness, reduced average specific leaf area and increased the height of whole plant communities in both ranges but these effects were significantly stronger in the non‐native stands.Sporobolusalso negatively affected the cover of insect‐pollinated plant species and the proportion of native perennials, switching the rest of the community from perennial‐dominated to annual‐dominated. In plant communities withoutSporobolus, increasingSporoboluscover led to a higher specific leaf area and seed mass in both ranges, but average height was decreasing along theSporobolusabundance gradient in the native range, whereas it was increasing in the non‐native range.ConclusionsThe spread ofSporobolus, away from its native range, leads to the impoverishment of host communities and compromises the biomass and floral resource‐provisioning capacity of the vegetation to higher trophic levels. Tackling the spread of this new invader should therefore be a priority task.

Connectivity Shapes Functional Diversity and Maintains Complementarity in Surf Zones on Exposed Coasts

Habitat complexity and connectivity can influence the number of species and their diversity across a landscape. For the surf zones of ocean-exposed beaches, globally one of the longest habitat interfaces, the assumed low structural complexity, and apparent homogeneity, of the sandy seafloor habitats predicts low taxonomic and functional diversity. Here, we assessed how the configuration of the seascape and the context of different beach structure functional diversity and functional niche space of fish assemblages in surf zones. We expected that beaches that were well connected with highly productive and complex estuarine and reef habitats would support a greater level of functional diversity, and a greater degree of functional complementarity within different niches. We sampled surf zones at twenty-five beaches along 50 km of coastline in southeast Queensland, Australia. We calculated functional diversity and functional niche space using variation in the functional traits of fish assemblages. We found that increased proximity with nearby subtidal rocky reefs was the key feature of the coastline shaping functional diversity and functional niche space in surf zone fishes. These effects resulted in increased functional complementarity within a number of fish functional group niches when rocky reefs were nearby. We provide empirical evidence that habitat proximity can structure functional diversity and complementarity in the surf zones of ocean beaches, a system traditionally viewed as having low habitat heterogeneity. Our results highlight the focus management must take in conserving these highly connected ecosystems to avoid negative functional consequences.

Bacillus velezensis supernatant mitigates tomato Fusarium wilt and affects the functional microbial structure in the rhizosphere in a concentration-dependent manner

This study aimed to test the hypothesis whether the soil-application of Bacillus velezensis Bs006 and its supernatant affect the rhizospheric microbial community of tomato-Fusarium oxysporum f. sp. lycopersici pathosystem. The relationship between the functional response of the microorganisms measured through use of carbon sources and the disease development was determined under a dose-response test between Fusarium wilt development and Bs006-based treatments (spores at 1 × 107 and 1 × 109 cfu ml−1 and supernatant at 1 and 10%). Use of carbon sources by the microbial community in the rhizosphere at 3 and 30 days after treatment were determined through the Ecoplate Biolog® microplate assays. The efficacy against disease development was dependent on the concentrations of biocontrol treatments, with low concentrations (Supernatant-1% and Bs006-107 cfu ml−1) significantly reducing the incidence of tomato vascular wilt compared to the effect of the highest concentrations (Supernatant-10% and Bs006-109 cfu ml−1). The use of carbon sources expressed as the average metabolic response (AMR), by the rhizosphere microbial community was higher in the less effective treatments of biocontrol than the absolute control and the plants treated with low concentration of biocontrol treatments. The high AMR was related with low functional microbial diversity, expressed as the number of carbon sources consumed, which was also low in the rhizosphere of the negative control. On the contrary, the AMR was lower, and the functional microbial diversity was higher in the most effective treatments against Fusarium wilt. Functional microbial groups consuming carbohydrates, polymers and amines were associated with the less effective treatments, while the use of amino acids and carboxylic acids was associated with the most effective treatments. We conclude that treatments containing Supernatant-10% changed the rhizosphere microbial behavior for carbon sources consumption and it was stablished as a factor that promotes the tomato Fusarium-wilt development. This study contributes to the aspects to be considered in the generation of use directions of fungicides based on Bacillus spp.

Divergent responses of functional diversity to an elevational gradient for vascular plants, bryophytes and lichens

AbstractQuestionCold environments are stressful for vascular plants, and stress‐tolerant non‐vascular photoautotrophs, e.g. bryophytes and lichens, become relatively more important as competition from vascular plants decreases towards higher elevations. Under increasingly stressful climatic conditions, species assembly of vascular plants is commonly driven more by environmental filtering, and abiotic constraints may lead to increased similarity between species and thus low functional diversity. Because bryophytes and lichens are less constrained by harsh environments, environmental filtering may be less strong. Instead, reduced competition from vascular plants can potentially free up niche space for non‐vascular vegetation. Therefore, we hypothesized that functional diversity of vascular plants, bryophytes and lichens are likely to show contrasting responses to elevation.LocationFinse Alpine Research Centre, Southern Norway.MethodsWe utilized measurements of species abundance and functional traits of the three groups along a 500‐m elevational gradient in alpine southern Norway and calculated multi‐trait and single‐trait functional dispersion.ResultsFunctional diversity of vascular plants declined with elevation, indicating increased environmental filtering. By contrast, functional diversity of lichens and bryophytes increased along the same gradient, suggesting they are less exposed to environmental filtering, in line with our hypothesis. Instead, they likely benefit from the lower abundance of vascular plants at higher elevation.ConclusionsOur findings suggest that different photoautotroph groups vary in how they respond to the same environmental gradient, which may contribute to contrasting community assembly processes across groups. These divergent responses likely occur because non‐vascular vegetation differs from vascular plants in terms of nutrient acquisition and water economy strategies, meaning that they respond differently to the same factors. This highlights the need to explicitly consider bryophytes and lichens in community‐level studies whenever these groups are abundant.

Changes in plant community composition and functional plant traits over a four-year period on an extensive green roof

Constructed ecosystems like green roofs are increasingly deployed in cities to mitigate issues associated with urbanization. To minimize the cost of green roof infrastructure, shallow growing media (substrate) for plants is often employed. Spatial heterogeneity in substrate depth has also been hypothesized to allow greater plant species diversity without adding to the weight. Stress and competition can change green roof plant communities after initial planting, but little is known about the long-term effects of spatial heterogeneity on vegetation composition and functional characteristics. Our goal was to determine how green roof plant communities and, in turn, functional plant traits, change over time in response to environmental stress and substrate heterogeneity. This four-year experiment used four substrate depth treatments: three with homogenous substrate depths of 5 cm, 10 cm, and 15 cm, and one treatment with a heterogenous substrate depth that varied between 5 cm and 15 cm (5/15 cm). The volume of the substrate in the 10 cm treatment and 5/15 cm treatment was equal. By the end of this four-year experiment, variation occurred between treatments for community composition and functional diversity, with the greatest species richness observed in the least stressful treatment (15 cm) and the greatest functional diversity and evenness observed in the most stressful treatment (5 cm). Additionally, each treatment had lower functional diversity after four years compared to the initially planted community. When the heterogenous 5/15 cm treatment was compared to the homogenous 10 cm treatment, there were no differences in the number of plant species, but the treatments contained two distinct plant communities. Furthermore, the 5/15 cm treatment supported taller species, a trait value associated with reduced stormwater runoff and substrate temperature. This finding indicates that creating green roofs with a heterogenous substrate depth could improve overall green roof function without increasing roof weight. Substrate depth can be manipulated by green roof designers to alter vegetation characteristics, but species and functional diversity showed opposite trends along the depth gradient.

Functional plasticity of carabids can presume better the changes in community composition than taxon-based descriptors.

Although the functional trait approach can facilitate the understanding of mechanisms that underline community responses to habitat alteration, only a few studies used this way on exploring the structure of insect assemblages compared to taxon-based analyses. We compared the descriptive power of medium-term effects (2014-2018) of forestry treatments in a temperate managed oak-dominated forest on taxon- vs. trait-based descriptors of ground beetle assemblages. The treatments included rotation forestry (partial preparation cutting, clear-cutting, retention-tree group, and mature closed forest as control) and continuous cover forestry (gap cutting) operations. The species composition was only slightly influenced by the treatments; on the ordination biplot, the control, retention tree group, and clear-cutting treatments formed relatively homogeneous groups, well separated from each other, while the others were scattered randomly in the ordination space. Over time, the species richness decreased in all treatments, but it was higher in the retention tree group treatment than in others in 2016 and 2017. The activity density also declined between years, but an immediate mass effect was revealed after the implementation of treatment types especially in the control, gap, and preparation cuts. We found that assemblages in the clear-cutting and retention-tree group had similar characteristics: high functional diversity; more open-habitat, generalist, and omnivore species and fewer carnivore species; while those in the control, gap, and preparation cutting groups had the opposite: lower functional diversity, more forest species, and more carnivorous species. Our findings will demonstrate that the simultaneous use of the two approaches will allow the most articulate understanding of the status of ground beetles assemblages in managed forests.

Does island ontogeny dictate the accumulation of both species richness and functional diversity?

AbstractAimThe accumulation of functional diversity in communities is poorly understood. Conveniently, the general dynamic model of island biogeography (GDM) makes predictions for how such diversity might accumulate over time. In this multiscale study of land snail communities on 10 oceanic archipelagos located in various regions of the globe, we test hypotheses of community assembly in systems where islands serve as chronosequences along island ontogeny.LocationTen volcanic archipelagos.Time periodFrom 23 Ma to the present.Major taxa studiedEndemic land snails.MethodsInitially, we assembled geological island characteristics of area, isolation and ontogeny for all studied islands. We then characterized island‐scale biotic variables, including the species diversity and functional diversity of snail communities. From these data, we assessed relationships between island and snail community variables as predicted by the GDM, focusing initially on the islands of the Galápagos archipelago and thereafter with a broader analysis of 10 archipelagoes.ResultsAs in other studies of island assemblages, in Galápagos we find a hump‐shaped curve of species richness, with depauperate snail faunas on early‐ontogeny islands, increasing species richness on mid‐ontogeny islands and low species richness on islands in late ontogeny. We find exceptionally low functional diversity on early‐ontogeny islands that increases through mid‐ontogeny, whereas late‐ontogeny islands exhibit a range of functional diversity. The analysis including all 10 archipelagos indicates a major role of archipelago‐specific factors. In both sets of analyses, functional diversity is exceptionally low on early‐ontogeny islands, and island ontogeny is a significant predictor of morphology.Main conclusionsConsistent patterns of functional diversity across island ontogeny on all examined archipelagos indicate a common role for habitat filtering, ecological opportunity and competition in a diversity of systems, leading to predictable changes in functional diversity and average morphology through island ontogeny, whereas patterns of species richness appear subject to archipelago‐specific factors.

Intensive site preparation for reforestation wastes multi-trophic biodiversity potential in commercial oak woodlands

Lowland oak forests host high biodiversity throughout Europe, and to maintain their high biodiversity potential we need to understand how current silviculture practices influence these ecosystems. The most common harvest approach in oak woodlands remains clear-cutting followed by site preparation for reforestation. The site preparation can vary in intensity and possibly affect forest biodiversity in various ways. We studied the impact of site preparation intensity on ground-dwelling arthropod predators and detritivores in commercial oak woodlands. The intensive management included mechanical site preparation with soil milling, stump removal, and herbicide application. The extensive management consisted of natural succession after reforestation with only such slight disturbances as regular hand-provided mowing of vegetation. We recorded 120 spider species, 92 species of ground beetles, 10 species of centipedes, 17 species of millipedes, and 7 species of woodlice, including a relatively large number of threatened species. We found that intensive post-logging management strongly homogenized the habitat structure, and this led to low multi-trophic taxonomic and functional diversity in comparison to that under extensive management. At sites with extensive management, there was not only high functional diversity but also high functional redundancy. Species of conservation concern almost vanished from clearings under intensive management. The high multi-trophic diversity and functional redundancy indicate that extensive site preparation may enhance ecosystem multi-functionality, including primary productivity and ecosystem resilience. Extensive post-harvest management is therefore strongly preferable, and it is also economically more feasible. Intensive post-harvest management should be prohibited in lowland forests within transition zones to localities under nature protection or in natural oak forests.

Invasive tree cover covaries with environmental factors to explain the functional composition of riparian plant communities.

Invasive species are a major cause of biodiversity loss worldwide, but their impact on communities and the mechanisms driving those impacts are varied and not well understood. This study employs functional diversity metrics and guilds-suites of species with similar traits-to assess the influence of an invasive tree (Tamarix spp.) on riparian plant communities in the southwestern United States. We asked: (1) What traits define riparian plant guilds in this system? (2) How do the abundances of guilds vary along gradients of Tamarix cover and abiotic conditions? (3) How does the functional diversity of the plant community respond to the gradients of Tamarix cover and abiotic conditions? We found nine distinct guilds primarily defined by reproductive strategy, as well as growth form,height, seed weight, specific leaf area, drought and anaerobic tolerance. Guild abundance varied along a covarying gradient of local and regional environmental factors and Tamarix cover. Guilds relying on sexual reproduction, in particular, those producing many light seeds over a long period of time were more strongly associated with drier sites and higher Tamarix cover. Tamarix itself appeared to facilitate more shade-tolerant species with higher specific leaf areas than would be expected in resource-poor environments. Additionally, we found a high degree of specialization (low functional diversity) in the wettest, most flood-prone, lowest Tamarix cover sites as well as in the driest, most stable, highest Tamarix cover sites. These guilds can be used to anticipate plant community response to restoration efforts and in selecting appropriate species for revegetation.

Palaeoecological patterns of change in marine invertebrate faunas across the End-Triassic mass extinction event: Evidence from Larne, Northern Ireland

The End-Triassic mass extinction event [ETE] (201.5 Ma) marks a drastic turnover and loss of >50% of marine biodiversity. Suggested environmental factors include extreme climate change and global carbon-cycle perturbations linked to Central Atlantic Magmatic Province (CAMP) volcanism. Considerable attention has been paid to disentangling the causes and selectivity of the ETE, whilst downplaying the patterns of change in the structure and functioning of marine paleofauna. Here we provide detailed quantitative information from across the Triassic-Jurassic boundary at Waterloo Bay, Larne, Northern Ireland, to describe patterns of changes in different palaeoecological parameters across the ETE. The analysis was based on abundance data of species sampled from approximately 1 m intervals through the sequence. Dominance and richness were estimated using rarefaction techniques and β-diversity index, and distinctness diversity indices were calculated. Changes in species composition were evaluated by multivariate analysis (nMDS, ANOMSIM and SIMPER). Rank abundance models were fitted, and functional diversity were estimated based on an ecospace model, applied to each sampled unit to detect changes in structure and ecological complexity. Across the ETE three distinctive states were identified: the pre-extinction state (Westbury Formation), characterised by an assemblage with high species richness and ecological redundancy, and with low taxonomic variation and functional diversity. The extinction state (Cotham and Langport members) represents a shift of the marine ecosystem, where >70% marine species disappears decreasing the ecosystems functioning the marine ecosystem around 80%. The recovery state (Lias Group), commencing some ~150 ky after the extinction, with ecologically complex assemblages as new taxa colonised, increasing variation in taxonomic distinctness and new contributing ecological traits and functional richness through the Hettangian. The palaeoecological patterns described here are robust enough to discount possible facies effects, but more important, is consistent with other studies reported globally, and demonstrates that the ecological signals detected in this study are real.

How does market power affect the resilience of food supply?

Food system shocks are mediated through value chains and underlying market structures, characterised by elements of power. Power imbalances are assumed to be detrimental to food security and to economic welfare, but the links between market power and food system resilience have not been extensively explored. This paper considers how shocks are potentially mitigated or amplified by the increasing consolidation of market power in globally interconnected food supply chains. We use UK examples to highlight evolving power-resilience dynamics and challenges from the perspectives of supply chain actors and regulators. We find that the impact of market power on the resilience of food supply is mixed. Low functional diversity levels, inflexible contracts and homogenous processes may increase supply chain vulnerability. A degree of power in terms of financial capacity, robust logistics and cooperation can enable firms to better mitigate shock impacts. Episodic crises appear to highlight the value of cooperation and of supply chain redundancy or slack, rather than the efficiency of perfect competition. This suggests a more nuanced perspective on market power than the largely detrimental perception implied by dominant economic theory. The discussion of the role of power in the food system should also consider social and environmental accountabilities of dominant food system actors, and whether these are sufficiently considered by existing regulatory structures.

Taxonomic and functional patterns of macrobenthic communities on a high Arctic shelf: A case study from the East Siberian Sea

The Siberian Arctic is one of the regions, where the ongoing climate change is the most evident. There is limited knowledge available on the distribution of macrobenthic communities in the Siberian Arctic, their stability and functional structure. We used data from two latitudinal transects from the East Siberian Sea shelf to describe the distribution of macrobenthic communities as well as to identify the main environmental drivers responsible for the observed patterns. Almost all the studied area was under the direct influence of river runoff. Macrobenthic communities were dominated by the bivalve Portlandia arctica and were generally characterised by low species and functional diversity. We suggest that the observed pattern is a direct consequence of considerable river runoff combined with low primary productivity. The overall pattern of macrobenthic distribution corresponds well with the data obtained in the previous decades, suggesting long-term stability of these communities.

Nitrogen fertilizer rate effects on yield and botanical components of summer annual forage mixtures

AbstractSummer annual grass‐legume mixtures may provide supplemental grazing for livestock when cool‐season pastures are less productive, but nitrogen fertilizer recommendations for these mixtures are not well established. Inputs to these systems are often high, so optimizing N fertilizer rates may increase appeal to producers. This study evaluated the effects of increasing botanical diversity and N fertilizer application on the yield and botanical composition of summer annual mixtures in four environments in Kentucky. Nitrogen fertilizer rates of 0, 56, 112, 168, and 224 kg N ha–1 were applied to a sudangrass [Sorghum bicolor (L.) Moench × Sorghum sudanese (P.) Stapf] monoculture, a three‐species mixture, and an 11‐species mixture. In three out of four environments, sward biomass increased as N application increased (average of 15 kg dry matter (DM) ha–1 increase per kg N ha–1; p < .05). Mixture complexity had no effect on forage DM accumulation in three out of four environments (4,000, 5,830, and 7,280 kg DM ha–1 averaged over mixture for three environments; p > .05). Mixtures were overwhelmingly dominated by grasses, resulting in low functional diversity. Legumes did not respond to N (p > .05), but their contribution to sward DM was <4%. Species compatibility should be a priority when utilizing multi‐species mixtures. If a stronger legume component is desired, care must be taken to provide management that favors these species, such as reduced grass‐seeding rates to limit competition, especially during initial establishment.

Latitude dictates plant diversity effects on instream decomposition.

Running waters contribute substantially to global carbon fluxes through decomposition of terrestrial plant litter by aquatic microorganisms and detritivores. Diversity of this litter may influence instream decomposition globally in ways that are not yet understood. We investigated latitudinal differences in decomposition of litter mixtures of low and high functional diversity in 40 streams on 6 continents and spanning 113° of latitude. Despite important variability in our dataset, we found latitudinal differences in the effect of litter functional diversity on decomposition, which we explained as evolutionary adaptations of litter-consuming detritivores to resource availability. Specifically, a balanced diet effect appears to operate at lower latitudes versus a resource concentration effect at higher latitudes. The latitudinal pattern indicates that loss of plant functional diversity will have different consequences on carbon fluxes across the globe, with greater repercussions likely at low latitudes.

A unique bacterial and archaeal diversity make mangrove a green production system compared to rice in wetland ecology: A metagenomic approach

Mangrove provides significant ecosystem services, however, 40% of tropical mangrove was lost in last century due to climate change induced sea-level rise and anthropogenic activities. Sundarban-India, the largest contiguous mangrove of the world lost 10.5% of its green during 1930–2013 which primarily converted to rice-based systems. Presently degraded mangrove and adjacent rice ecology in Sundarban-India placed side by side and create typical ecology which is distinct in nature in respect to soil physicochemical properties, carbon dynamics, and microbial diversities. We investigated the structural and functional diversities of bacteria and archaea through Illumina MiSeq metagenomic analysis using V3–V4 region of 16S rRNA gene approach that drives greenhouse gases emission and carbon-pools. Remote sensing-data base were used to select the sites for collecting the soil and gas samples. The methane and nitrous oxide emissions were lower in mangrove (−0.04 mg m−2 h−1 and −52.8 μg m−2 h−1) than rice (0.26 mg m−2 h−1 and 44.7 μg m−2 h−1) due to less availability of carbon-substrates and higher sulphate availability (85.8% more than rice). The soil labile carbon-pools were more in mangrove, but lower microbial activities were noticed due to stress conditions. A unique microbial feature indicated by higher methanotrophs: methanogens (11.2), sulphur reducing bacteria (SRB): methanogens (93.2) ratios and lower functional diversity (7.5%) in mangrove than rice. These could be the key drivers of lower global warming potential (GWP) in mangrove that make it a green production system. Therefore, labile carbon build-up potential (38%) with less GWP (63%) even in degraded-mangrove makes it a clean production system than wetland-rice that has high potential to climate change mitigation. The whole genome metagenomic analysis would be the future research priority to identify the predominant enzymatic pathways which govern the methanogenesis and methanotrophy in this system.

Does abiotic noise promote segregation of functional diversity in Neotropical anuran assemblages?

Abstract The abiotic noise of streams can mask the acoustic signals of anurans with a large body size calling at low frequencies, but not the signals emitted by anurans with a small body size calling at high frequencies. As a consequence, the body size of species in assemblages alongside streams is, on average, lower and less variable than that of assemblages away from streams. Given that the body size in anurans is frequently related to life-history traits, it is expected that functional diversity (FD) will be lower in anuran assemblages alongside streams than in assemblages away from streams. We calculated and compared FD, based on six functional traits, for anuran species in seven localities in different biogeographical regions in the Neotropics. In five lowland localities, FD was lower in assemblages alongside streams than in assemblages away from streams. However, the reverse trend was found in two Andean localities. Noise from streams, acting as an environmental filter, could promote low FD because taxa whose phenotype differs from an optimal type (high call frequency, small body size and associated traits) are excluded from riparian places. However, such habitat filtering could be stronger and affect more anurans in lowland assemblages than in those at medium elevation.

Soil chemistry drives below ground traits in an alternate successional pathway from forest to heath.

To understand impacts of post-disturbance assembly mechanisms on the functional diversity (FD) of plant communities, it is necessary to determine how the environment drives their functional trait composition. In the boreal forest, post-fire abiotic filters may control community assembly by selecting plants with specific traits. Ericaceous heaths are characterized by low FD and are thought to be subject to such filters. We hypothesized that soil parameters select for a specific suite of traits and act as a secondary abiotic filter in post-fire ericaceous heath and contribute to the observed reduction of FD. We measured six soil parameters, five functional traits, and plant species abundances in eight post-fire heath and four regenerating forest sites in Eastern Canada. We conducted a combined analysis of RLQ (R-table Linked to Q-table) and fourth-corner methods to examine the links between plant traits and plot-level soil parameters, mediated by species abundances. Only below ground traits were significantly linked to soil variables. Specific root length and ericoid mycorrhizal associations were negatively linked to total soil nitrogen, available ammonium, and pH. Post-fire heath soils favour a specific suite of species traits. Only a portion of the regional species pool possesses the above-mentioned traits, and when they are favoured by habitat conditions, they assemble into a community with low FD. The novelty of our study is here we show how the relationship between traits and soil chemistry can act as a secondary filter and exert community-level trait changes responsible for the low functional diversity observed in heaths.

Saline gradient drives functional nestedness of polychaete communities in tropical estuaries

Estuarine environmental gradients are strong drivers structuring aquatic metacommunities and may cause an orderly loss or gain of species across sites. Locations with milder environmental conditions may allow the establishment of many species with different functional traits, while stressful sites may restrict the occurrence of a reduced set of species with specific functional traits. This can generate a functional nestedness pattern, where the functional traits present at sites with low functional diversity are subsets of the functional traits present at sites with higher functional diversity. In this study, we evaluated the functional nestedness of polychaete communities along salinity gradients of tropical estuaries, and the effects of seasonal periods on the distribution pattern. Two tropical estuarine ecosystems (Mamanguape and Paraíba do Norte, Northeastern Brasil) were sampled for two years. Three functional traits were considered due to their potential to reflect the species responses to the salinity gradient: maximum body size, life span and fecundity. Functional nestedness was estimated with the traitNODF metric. Subsequently, we used a permutation test to assess whether the nestedness observed along the salinity gradient was distinct from the expected at random. Our results demonstrated that the polychaete communities presented a tendency to functional nestedness along the salinity gradient of estuaries, with observed statistics higher than expected in six of the eight tests performed (2 estuaries * 2 years * 2 seasons). Therefore, the functional diversity of polychaete genera present in the low salinity sites in general were nested subsets of the diversity at high salinity sites. Our results suggest that salinity acted as a strong environmental filter in estuarine ecosystems, causing an orderly loss in the functional traits of polychaete genera along the longitudinal extension of the estuaries. Our results advance in the understanding on how environmental gradients structure polychaete communities and can support future studies aimed to develop conservation strategies for estuarine ecosystems located throughout the world.

Taxonomic and functional beta diversity of woody communities along Amazon forest succession: The relative importance of stand age, soil properties and spatial factor

Predicting how multiple drivers shape beta diversity across tropical forest is one of the most important issues in ecology. However, the relative importance of drivers to the spatial and temporal dissimilarities in woody species composition (beta diversity) along Amazon forest succession remains poorly studied. In this study, we assessed how stand age (factor related to habitat filtering and succession), soil properties (factors related to resource availability and environmental filtering) and forest patches distance (spatial factor related to dispersal limitation) affect the taxonomic and functional beta diversity along an Amazon forest succession. Taxonomic and functional beta diversity indices were quantified based on abundance-based metrics and trait-based approach using functional traits related to plant dispersion and growth. Overall, taxonomic and functional beta diversity was consistently higher in initial successional stage among plots and sites; however, old-growth forest presented the lowest functional beta diversity. We observed differences in beta diversity components among successional stages and old-growth forest. The beta diversity components showed a clear higher pattern in the different second-growth forests than in the old-growth forest. Soil fertility and stand age explained most of the variation in taxonomic and functional turnover and beta diversity. This pattern probably is an outcome of the patches within a continuous old-growth forest as main seed sources for the colonization and establishment of tree species. We observed that functional beta diversity was lower than taxonomic beta diversity; therefore we presumed that there is higher functional redundancy in old-growth forests, compared to taxonomic beta diversity. However, despite the lower functional beta diversity and higher functional redundancy in old-growth forest, probably shade-tolerant species have different functions than second-growth forests that re-growing after shifting cultivation. We argue that an old-growth forest has lower functional diversity than second-growth forests but, it is probably induced by a high turnover of second-growth forests.