Traits Of Assemblages Research Articles

Benthic taxonomic and functional diversity change across a depth gradient in the Southern Benguela Shelf ecoregion

Functional trait-based approaches improve biodiversity assessment and have consequently been gaining traction in ecology, including marine benthic studies. However, taxonomic diversity is still the default biodiversity metric applied to monitor benthic community responses to environmental variation despite not always representing functional diversity change. Therefore, we used Biological Traits Analysis (BTA) to quantify functional diversity for infauna and epifauna communities collected from the same locations across a depth gradient in the Southern Benguela Shelf ecoregion. Infauna experienced an increase in functional uniqueness with depth, whereas epifauna experienced an increase in functional redundancy with depth. As a result, the epifauna species assemblage predicted 43 % of the epifauna trait assemblage, whereas the infauna species assemblage predicted only 8 % of the infauna trait assemblage. These findings suggest that taxonomic diversity and functional diversity changes are not congruent within and between marine benthic faunal groups. We emphasize the need to utilise both biodiversity metrics when quantifying marine biodiversity for conservation and management objectives.

Fungal trait‐environment relationships in wood‐inhabiting communities of boreal forest patches

Abstract Fungal traits can provide a mechanistic understanding of how wood‐inhabiting fungi interact with their environment and how that influences community assembly in deadwood. However, fungal trait exploration is relatively new and almost no studies measure fungal traits in their environment. In this study we tested species‐ and trait‐environment relationships in reproducing fungal communities inhabiting 571 Norway spruce (Picea abies) logs in 55 isolated forest patches (0.1–9.9 ha) of different naturalness types, located in Northern boreal Sweden. The studied patches were (1) semi‐natural set‐aside patches within highly managed landscapes, or (2) old‐growth natural patches located in an unmanaged landscape. We tested species and trait relationships to deadwood substrate and forest patch variables. We measured mean fruit body size and density for each of the 19 species within communities. Traits assembled in relation to log decay stage and forest patch naturalness, illustrating the important role of deterministic environmental filtering in shaping reproducing wood‐inhabiting fungal communities. Early decay stage communities had larger, less dense, annual fruiting bodies of half‐resupinate type and were more often white‐rot fungi. Species rich mid‐decay stage communities had mixed trait assemblages with more long lived perennial fruit bodies of intermediate size, and both brown‐ and white‐rot fungi equally represented. Finally, late decay stage communities had smaller, denser and perennial fruit bodies, more often of the brown‐rot type. The relationships between the studied traits and decay stages were similar in both set‐aside and natural patches. However, set‐aside semi‐natural patches in highly managed landscapes more frequently supported species with smaller, perennial and resupinate fruit bodies compared to natural patches in an unmanaged landscape. Synthesis. We found that log decay stage was the primary driver of fungal community assembly of species and traits in isolated forest patches. Our results suggest that decay stage filters four reproduction traits (fruit body density, size, lifespan and type) and one resource‐use trait (white or brown rot). Our results highlights, for the first time, that communities with diverse fungal reproductive traits are maintained foremost across all deadwood decay stages under different forest naturalness conditions. Read the free Plain Language Summary for this article on the Journal blog.

Future climate doubles the risk of hydraulic failure in a wet tropical forest.

Future climate presents conflicting implications for forest biomass. We evaluate how plant hydraulic traits, elevated CO2 levels, warming, and changes in precipitation affect forest primary productivity, evapotranspiration, and the risk of hydraulic failure. We used a dynamic vegetation model with plant hydrodynamics (FATES-HYDRO) to simulate the stand-level responses to future climate changes in a wet tropical forest in Barro Colorado Island, Panama. We calibrated the model by selecting plant trait assemblages that performed well against observations. These assemblages were run with temperature and precipitation changes for two greenhouse gas emission scenarios (2086-2100: SSP2-45, SSP5-85) and two CO2 levels (contemporary, anticipated). The risk of hydraulic failure is projected to increase from a contemporary rate of 5.7% to 10.1-11.3% under future climate scenarios, and, crucially, elevated CO2 provided only slight amelioration. By contrast, elevated CO2 mitigated GPP reductions. We attribute a greater variation in hydraulic failure risk to trait assemblages than to either CO2 or climate. Our results project forests with both faster growth (through productivity increases) and higher mortality rates (through increasing rates of hydraulic failure) in the neo-tropics accompanied by certain trait plant assemblages becoming nonviable.

Variations in the plasticity of functional traits indicate the differential impacts of abiotic and biotic factors on the structure and growth of trees in tropical dry forest fragments

Abiotic and biotic factors have considerable impact on the plasticity of plant functional traits, which influences forest structure and productivity; however, their inter-relationships have not been quantified for fragmented tropical dry forest (TDF) ecosystems. We asked the following questions: (1) what are the variations in the plasticity of functional traits due to soil moisture availability in TDF fragments? (2) what are the roles of soil nutrients and forest disturbances in influencing variations in the plasticity of functional traits in the TDF fragments? and (3) how do the variations in the plasticity of functional traits influence the structure and productivity of TDF fragments? Based on linear mixed-effects results, we observed significant variations among tree species for soil moisture content (SMC) under the canopy and selected functional traits across forest fragments. We categorized tree species across fragments by principal component analysis (PCA) and hierarchical clustering on principal components (HCPC) analyses into three functional types, viz., low wood density high deciduous (LWHD), high wood density medium deciduous (HWMD), and high wood density low deciduous (HWLD). Assemblage of functional traits suggested that the LWHD functional type exhibits a drought-avoiding strategy, whereas HWMD and HWLD adopt a drought-tolerant strategy. Our study showed that the variations in functional trait plasticity and the structural attributes of trees in the three functional types exhibit contrasting affinity with SMC, soil nutrients, and disturbances, although the LWHD functional type was comparatively more influenced by soil resources and disturbances compared to HWMD and HWLD along the declining SMC and edge distance gradients. Plasticity in functional traits for the LWHD functional type exhibited greater variations in traits associated with the conservation of water and resources, whereas for HWMD and HWLD, the traits exhibiting greater plasticity were linked with higher productivity and water transport. The cumulative influence of SMC, disturbances, and functional trait variations was also visible in the relative abundance of functional types in large and small sized fragments. Our analysis further revealed the critical differences in the responses of functional trait plasticity of the coexisting tree species in TDF, which suggests that important deciduous endemic species with drought-avoiding strategies might be prone to strategic exclusion under expected rises in anthropogenic disturbances, habitat fragmentation, and resource limitations.

Reconciling continuous and discrete models of C4 and CAM evolution.

A current argument in the CAM biology literature has focused on the nature of the CAM evolutionary trajectory: whether there is a smooth continuum of phenotypes between plants with C3 and CAM photosynthesis or whether there are discrete steps of phenotypic evolutionary change such as has been modelled for the evolution of C4 photosynthesis. A further implication is that a smooth continuum would increase the evolvability of CAM, whereas discrete changes would make the evolutionary transition from C3 to CAM more difficult. In this essay, I attempt to reconcile these two viewpoints, because I think in many ways this is a false dichotomy that is constraining progress in understanding how both CAM and C4 evolved. In reality, the phenotypic space connecting C3 species and strong CAM/C4 species is both a continuum of variably expressed quantitative traits and yet also contains certain combinations of traits that we are able to identify as discrete, recognizable phenotypes. In this sense, the evolutionary mechanics of CAM origination are no different from those of C4 photosynthesis, nor from the evolution of any other complex trait assemblage. To make progress, we must embrace the concept of discrete phenotypic phases of CAM evolution, because their delineation will force us to articulate what aspects of phenotypic variation we think are significant. There are some current phenotypic gaps that are limiting our ability to build a complete CAM evolutionary model: the first is how a rudimentary CAM biochemical cycle becomes established, and the second is how the 'accessory' CAM cycle in C3+CAM plants is recruited into a primary metabolism. The connections to the C3 phenotype we are looking for are potentially found in the behaviour of C3 plants when undergoing physiological stress - behaviour that, strangely enough, remains essentially unexplored in this context.

Ecomorphological groups in oribatid mite communities shift with time after topsoil removal – Insight from multi-trait approaches during succession in restored heathlands

Restoration of nutrient-enriched heathlands and similar dry habitats via topsoil removal requires the re-assembly of above and belowground communities to attain fully functional ecosystems. Top-soil removal provides unique opportunities to study the assembly processes, but research has traditionally focused on succession of the aboveground part of the ecosystem. Oribatid mites are a dominant group of soil mesofauna in the belowground part of heathlands. They possess attributes for bioindication and have shown high sensitivity to environmental changes during succession. However, few studies have focused on changes in functional community profiles and the factors shaping them with time. We sampled heathlands of different restoration ages located in East Belgium, studied traits of oribatid mite communities of a chronosequence, and assessed the interaction between traits and abiotic variables using community weighted means (CWM) and an iterative co-correlation analysis between abiotic parameters, species trait attributes and species abundances (iterative RLQ analysis). Our study suggests that moisture preferences, concealability (i.e. defence mechanism against desiccation and predation), and body length were the dominant traits structuring the oribatid mite communities. We found that both dispersal and environmental filters shape the assembly of oribatid mite communities, but these drivers dominate different stages of succession. Moreover, trait assemblages deriving from three well-defined eco-morphological groups closely followed these constraints in time. Thus, the shifting dominance of specific groups provides valuable insight on the soil community functioning in a changing environment.

Exploring fish functional trait assemblages in Eastern Mediterranean rivers: a study across multiple scales using network analysis

Functional traits of river fish assemblages have rarely been studied in the Eastern Mediterranean region. A dataset of 254 Greek electrofished near-natural sites (427 samples) was analyzed to explore native fish functional structure across three spatial scales: (a) among six ecoregions, (b) within a single ecoregion, and (c) in a river basin. Overall, 76 native fish species were assigned eight functional categories, involving 24 different traits. Bipartite networks were used to interpret spatial patterns of species trait data. Two major trait assemblage types were detected in all three spatial scales: the upland type, dominated by insectivorous, benthic, rheophilic, intolerant species, and the lowland type, incorporating omnivorous, limnophilic, phytophilic, and tolerant species. In order to provide further insights between traits and key environmental variables, redundancy analysis (RDA) was employed. The RDA depicted a strong upstream–downstream environmental gradient. Upland and lowland assemblage types form two distinct functional zones along the upstream and downstream river stretches, respectively. Yet, no consistent boundary criteria seem to exist between them. Notably, within a region of high fish assemblage heterogeneity such as the Eastern Mediterranean, functional patterns follow well-established phenomena along the upstream–downstream longitudinal profile of temperate lotic waters.

Co-variation of fish and coral traits in relation to habitat type and fishery status

Escalating climate impacts on coral reefs are increasingly expanding management goals beyond preserving biodiversity to also maintaining ecosystem functions. Morphological and ecological species traits can help assess changes within reef communities beyond taxonomic identities alone. However, our limited understanding of trait interactions between habitat-building corals and associated reef fishes and whether they are captured by current monitoring practices hampers management. Here, we apply co-inertia analyses to test whether trait assemblages in corals and fishes co-vary across different habitats and test whether different components of the reef fish community (fisheries vs. non-target species) display distinct relationships. We find that spatial co-variation across habitat types between coral and fish traits is strengthened by the addition of non-target fishes. Additionally, even in fisheries with diverse targets, non-target species make unique contributions to the overall trait structure and highlight the importance of considering monitoring protocols when drawing conclusions about traits and ecosystems.

Limited role of soil texture in mediating natural vegetation response to rainfall anomalies

Evidence suggests that the response of rainfed crops to dry or wet years is modulated by soil texture. This is a central tenet for certain agronomic operations in water-limited regions that rely on spatial distribution of soil texture for guiding precision agriculture. In contrast, natural vegetation in climatic equilibrium evolves to form a dynamic assemblage of traits and species adapted to local climatic conditions, primarily precipitation in water-limited regions. For undisturbed landscapes, we hypothesize that natural vegetation responds to rainfall anomalies irrespectively of local soil texture whereas rainfed crops are expected to respond to texture-mediated plant available water. Earth system models (ESMs) often quantify vegetation response to drought and water stress based on traditional agronomic concepts despite fundamental differences in composition and traits of natural vegetation and crops. We seek to test the hypothesis above at local and regional scales to differentiate natural vegetation and rainfed crops response to rainfall anomalies across soil types and better link them to water and carbon cycles. We employed field observations and remote sensing data to systematically examine the response of natural and rainfed cropped vegetation across biomes and scales. At local scales (field to ∼0.1 km), we used crop yields from literature data and natural vegetation productivity as gross primary productivity (GPP) from adjacent FLUXNET sites. At regional scales (∼102 km), we rely exclusively on remote-sensing-based GPP. Results confirm a lack of response of natural vegetation productivity to soil texture across biomes and rainfall anomalies at all scales. In contrast, crop yields at field scale exhibit correlation with soil texture in dry years (in agreement with conventional agronomic practices). These results support the hypothesis that natural vegetation is decoupled from soil texture, whereas rainfed crops retain dependency on soil texture in dry years. However, the observed correlation of crops with soil texture becomes obscured at larger scales by spatial variation of topography, rainfall, and uncertainty in soil texture and GPP values. The study provides new insights into what natural vegetation’s climatic equilibrium might mean and reveals the role of scale in expressing such sensitivities in ESMs.

Decoupling linked coral and fish trait structure

In coral reef systems, increasingly frequent, severe climate change-driven disturbances are responsible for declines in vulnerable species, and a reorganisation of assemblages. Whilst these changes will certainly elicit shifts in ecosystem functioning, how trait distributions and cross-taxon interactions are altered remains largely unmeasured, hampering our ability to predict functional shifts and target management actions to support reef health and recovery. We quantify trait distributions and interactions between habitat-engineering corals affected by a coral-bleaching mortality and associated fished reef fish assemblages. First, we assess changes in the proportional contributions of different traits pre- vs. post-disturbance. We then quantify changes in the trait associations that underpin cross-taxon interactions, and test relationships between coral and fish traits. The effects of reef type and survey atoll on coral trait structure are most influential, and there is a subtle temporal shift over the survey period. The trait structure of the fish assemblage remains stable. This suggests a simplification of the coral assemblage as vulnerable species disappear. The stability of the fish trait assemblage could indicate a lagged response, limited reliance on coral habitat, influence of other drivers or relative resilience. However, when examining traits of both taxa together, we discover that associations between individual coral and fish traits break down over time. We find reduced co-structure between the assemblages’ trait distributions, altering the associations between taxa. Our study signals weakened associations of fishes with their habitat as coral assemblages degrade with climate change, potentially disrupting the ecosystem functions that support services of coral reefs.

Functional and species composition of understory plants varies with mistletoe-infection on Vachellia karroo trees in a semi-arid African savanna

In savanna ecosystems, tree canopy patches differ in plant species composition compared to adjacent intercanopy spaces due to different levels of resource availabilities. Mistletoes further augment nutrients underneath tree canopies whilst reducing their hosts’ competitive edge, thus providing more resources and creating patches that support higher understory species richness. However, little is known on how understory species and functional trait assemblages, in both canopy and intercanopy spaces, are affected by varying overstory mistletoe infection intensities. This study investigated how functional and species diversity/composition varied within and between canopy patches and intercanopy spaces of high- and low mistletoe-infected Vachellia karroo trees. The affinity of individual species to the different canopy patches and intercanopy spaces was also assessed. Microhabitats had significantly different species compositions. A higher proportion of species (34%) showed a strong positive affinity towards canopy patches whilst intercanopy spaces were strongly associated with only 9% of recorded species, indicating greater dominance of some species there. Generally, subcanopy patches had significantly higher species richness and diversity, and functional diversity, compared to adjacent intercanopy spaces. These variables increased with increasing mistletoe infection, thus grass, forb and tree species diversity were 17–43% higher, and functional diversity indices were 0.5–28% greater in high- compared to low mistletoe-infection canopy patches. Furthermore, species richness and diversity of C 3 , C 4 , annual and perennial plants were 1.27–3.13-fold higher within canopy patches compared to intercanopy spaces and 1.28–1.74-fold greater within high- compared to low mistletoe-infection microhabitats. Consequently, high mistletoe-infection canopy patches had between 1.08 and 3.76-fold greater species richness and diversity of C 3 , C 4 , annual and perennial plants compared to the other three microhabitats. Our findings suggest that by enhancing spatial heterogeneity, variations in mistletoe infection facilitate biodiversity and to a lesser extent vegetation structural diversity in these semi-arid savannas. • Mistletoes provide additional resources to understory plants. • Species and functional diversity are greater within subcanopies than intercanopies. • Increased mistletoe infection, proliferates species and functional diversity. • Many species have a strong affinity to high mistletoe-infection subcanopies. • Mistletoes increase plant diversity in semi-arid savannas.

Responses of Collembola communities to mixtures of wheat varieties: A trait-based approach

The genetic diversity of cultivated crops has decreased continuously since the beginning of the 20th century, because of the gradual replacement of genetically heterogeneous traditional varieties by new genetically homogenous varieties, grown in monospecific stands. The resulting agro-ecosystems are now considered as unsustainable. Increasing within-field genetic crop diversity by using a mixture of varieties could increase the sustainability of these agro-ecosystems. This could also potentially increase non-crop biodiversity. In the present study we used an experimental approach to test whether the number of wheat varieties (genetic diversity), the number of functional groups (functional diversity), the composition of functional groups and wheat traits influence (1) species richness and abundance of Collembola, and (2) species and trait assemblages of Collembola. A total of 104 plots were seeded with either monocultures or mixtures of 2, 4 and 8 wheat varieties. Soil cores were collected in each plot to extract Collembola and measure soil features. The number of wheat varieties and the functional wheat diversity did not influence the abundance and species richness of Collembola. The sensitivity of wheat to septoria leaf blotch was positively related to abundance and species richness of Collembola, while specific root length was positively related to collembolan species richness. Wheat traits related to sensitivity to fungal diseases, (more especially septoria leaf blotch) and characteristics of aerial parts and roots impacted collembolan species and trait assemblages, but these effects were weak. Soil features, especially the proportion of coarse silt, were also influential. Our study did not show a favorable impact of wheat genetic diversity on soil Collembola, which might result from their low abundance. Nevertheless, it suggests correlations between some variety traits and the species richness and abundance of Collembola.

Multi‐scale biodiversity analyses identify the importance of continental watersheds in shaping lake zooplankton biogeography

AbstractAimWe examined variation in crustacean zooplankton composition and diversity across Canada, the most lake‐rich country in the world. In addition to α‐diversity patterns, we explore mechanisms behind β‐diversity spatial variation, using taxonomic and functional metrics. Our goal was to explore geographical gradients and related mechanisms shaping zooplankton distribution across different spatial scales.LocationCanada.TaxonCrustacean zooplankton.MethodsPelagic zooplankton was sampled in and characterized for 624 lakes across Canada, spanning 12 ecozones (defined by climatic, vegetation and geological differences) or 6 continental drainage basins as part of the NSERC Canadian Lake Pulse Network project. We compared taxon and trait distributions, as well as spatial (longitudinal and latitudinal) patterns of community composition and diversity. We computed taxonomic and functional spatial β‐diversity indices, decomposing these into taxon replacement and richness differences. Finally, species (or traits) and lake uniqueness (contributions) to β‐diversity (SCBD and LCBD) were estimated by ecozone and continental basin.ResultsIn all, 90 crustacean zooplankton species were identified across the country. Differences in zooplankton taxonomic and functional composition were more distinct when considered by continental basin than by ecozone. α‐diversity varied greatly across space, with greatest diversity in eastern Canada. β‐diversity was greatest when based on taxonomy and was driven by richness differences across all spatial and biodiversity dimensions.Main conclusionsStructuring factors influencing zooplankton taxon and trait assemblages vary across spatial scales, being more important at the broadest scale considering continental hydrodynamics. Our results point to the combined effects of physical barriers to longitudinal dispersal and climate change in shaping zooplankton taxonomic and functional biogeography across Canadian lakes.

Local habitat is a strong determinant of spatial and temporal patterns of macrophyte diversity and composition in boreal lakes

Abstract Macrophyte species and trait assemblages from 104 minimally disturbed boreal forest lakes, covering broad environmental and geographic gradients were analysed to identify associations with environmental variables at different spatial scales: geographic context (GEO) and catchment (CATCH) and lake (LOCAL) characteristics. Constrained ordination and variation partitioning were used to quantify variation in species (canonical correspondence analysis [CCA] and pCCA) and trait (redundancy analysis [RDA] and pRDA) compositions that could be explained by environmental variables, and to rank the main environmental factors associated with spatial and temporal patterns. Diversity and assemblage composition correlated with spatial context and variables related to the length of the growing season, catchment forest type and with lake characteristics such as ecosystem size, lake productivity and alkalinity. Variation partitioning showed that lake characteristics alone explained 53% (species) and 73.5% (traits) of the variability in macrophyte assemblages. Contrary to predictions, the shared variance component between latitude and catchment forest type (GEO&CATCH < 0.1% for both species and traits) and between latitude and lake characteristics (GEO&LOCAL = 6.7% for species and 3.9% for traits) was low. Temporal variability, measured as changes in species richness, diversity and a pollution‐specific index (the Trophic Macrophyte Index), using a subset of the lakes sampled on two occasions (19 lakes sampled in 2012 and 2018 and five lakes sampled in 2013 and 2019) did not differ (p > 0.05, paired t‐test). Ordination showed that among‐year variability in macrophyte assemblage composition was also negligible (0.3%) compared to the variability explained by GEO, CATCH and LOCAL variables. Combined, these findings indicate low species turnover in the boreal lakes of our study. Responses of macrophyte species and trait assemblages and the TMI index were predictable and significantly correlated with lake characteristics associated with nutrient enrichment (Chl a, nutrients) and alkalinity supporting their use in monitoring eutrophication of boreal lakes.

Composition and Specialization of the Lichen Functional Traits in a Primeval Forest—Does Ecosystem Organization Level Matter?

Current trends emphasize the importance of the examination of the functional composition of lichens, which may provide information on the species realized niche diversity and community assembly processes, thus enabling one to understand the specific adaptations of lichens and their interaction with the environment. We analyzed the distribution and specialization of diverse morphological, anatomical and chemical (lichen secondary metabolites) traits in lichen communities in a close-to-natural forest of lowland Europe. We considered these traits in relation to three levels of forest ecosystem organization: forest communities, phorophyte species and substrates, in order to recognize the specialization of functional traits to different levels of the forest complexity. Traits related to the sexual reproduction of mycobionts (i.e., ascomata types: lecanoroid apothecia, lecideoid apothecia, arthonioid apothecia, lirellate apothecia, stalked apothecia and perithecia) and asexual reproduction of mycobionts (pycnidia, hyphophores and sporodochia) demonstrated the highest specialization to type of substrate, tree species and forest community. Thallus type (foliose, fruticose, crustose and leprose thalli), ascospore dark pigmentation and asexual reproduction by lichenized diaspores (soredia and isidia) revealed the lowest specialization to tree species and substrate, as well as to forest community. Results indicate that lichen functional trait assemblage distribution should not only be considered at the level of differences in the internal structure of the analyzed forest communities (e.g., higher number of diverse substrates or tree species) but also studied in relation to specific habitat conditions (insolation, moisture, temperature, eutrophication) that are characteristic of a particular forest community. Our work contributes to the understanding of the role of the forest structure in shaping lichen functional trait composition, as well as enhancing our knowledge on community assembly rules of lichen species.

Shelf and deep-water benthic macrofauna assemblages from the western Gulf of Mexico: Temporal dynamics and environmental drivers

Shelf and deep-water soft-bottom macrofauna were explored in the western Gulf of Mexico in terms of species and functional trait assemblages. Their variation was analysed as functions of depth and time, and the relationship with sea-bottom environmental conditions was examined to disentangle their association with potential environmental drivers. Four consecutive cruises (two per year, at the end of the dry and rainy seasons) were performed during 2016–2017 at 27 fixed stations distributed from 42 to 3565 m depth. Changes in macrofauna composition were tested considering species and functional trait assemblages. Environmental variables associated with sediment features (i.e., grain structure, organic matter, pH, redox), oceanographic conditions (i.e., temperature, dissolved oxygen, particulate organic carbon flux) and potential contaminants (i.e., hydrocarbons and metals) were analysed to identify potential drivers that would shape the structure of macrofauna assemblages. The results suggest that the structures of both species and functional trait assemblages change according to depth and show temporal variation in composition at seasonal and interannual scales. The effect of temporal variation represented about 12% of total variation in the assemblages (11.4 for species and 12.5% for functional-traits). Different patterns of spatial and temporal variation between shelf and deep benthic communities were observed. Variation in species assemblages on the shelf were related to the variation in lead, polycyclic aromatic hydrocarbons and the fine sand ratio. In the deep benthos, particulate carbon flux showed high correlation with the spatial and temporal variation in species assemblage. In the deep benthos the changes in the species assemblage between the dry and the rainy seasons and the interannual variation were highly correlated with particulate organic carbon input in the area.

Wheat and barley cultivars show plant traits acclimation and increase grain yield under simulated shade in Mediterranean conditions

AbstractAgroforestry systems are reported as climate‐resilient productive systems, but it is yet unclear how tree shade affects crops performance. The aim of this work was to assess how the phenology, plant traits and grain yield of wheat and barley were affected by shade. In an open greenhouse experiment, we cultivated in pots nine cultivars differing in precocity for each species and imposed three artificial shading levels (S0 ~ 0%, S1 ~ 25%, S2 ~ 50%) at the start of cereal booting. Our results showed that shade speeded up first growth stages in both species, until the starting of milk development. Barley showed consistent phenological responses to the three irradiance levels among cultivars, but not wheat that showed larger phenological differences among cultivars at moderate shade. Deep shade prolonged the time needed for wheat grain ripening. Both species increased grain yield by 15%–20% with shade, driven by shade‐acclimations of plant traits that differed among species. For wheat, grain yield was determined by the assemblage of traits that contribute to yield, such as grain weight, precocity and non‐photochemical quenching, while, for barley, SPAD value, precocity to reach phenological stages, grains per spike and plant height had the strongest influence. These traits varied widely among cultivars and seem of interest to identify best suited cultivars for shading conditions of Mediterranean agroforestry systems.

Early avian functional assemblages after fire, clearcutting, and post-fire salvage logging in North American forests

Increased demand for timber, the reduction in the available timber resources, and more frequent and severe forest fires under a changing climate have increased the use of salvage logging in North American forests despite concerns regarding impacts on biodiversity and long-term forest productivity. We aimed to complement previous approaches that used bird species richness or individual abundance in salvage-logged habitats to assess the sustainability of this practice. We looked for commonalities in the taxonomic, functional, and phylogenetic components of bird assemblages among these three post-disturbance habitats across a broad geographic range. We compiled six North American datasets selected from primary and grey literature that documented species composition of avian assemblages in habitats after recent fire, post-fire salvage logging, and traditional logging. Our results revealed contrasting patterns of bird trait assemblage among burned, post-fire salvage, and traditionally logged habitats. In salvage-logged habitats, taxonomic diversity, functional diversity, and functional and phylogenetic redundancy were significantly lower than in both burned and traditionally logged habitats. The frequency of insectivores was significantly lower after salvage logging than after both fire and traditional logging. These findings suggest that cumulative disturbances have a negative effect on early assembly of bird communities. The outcomes of this study encourage further assessments, at landscape level, of salvage logging intensity, burn size, and fire severity on bird functional structure to better plan for their conservation.

Functional Diversity Effects of Vegetation on Runoff to Design Herbaceous Hedges for Sediment Retention

Background: Functional diversity effects on ecosystem processes, like on soil erosion, are not fully understood. Runoff and soil erosion in agricultural landscapes are reduced by the hydraulic roughness (HR) of vegetation patches, which furthers sediment retention. Vegetation with important stem density, diameters, leaf areas, and density impact the HR. A functional structure composed of these negatively correlated traits involved in the increase of the HR would constitute a positive effect of the functional diversity. Methods: Runoff simulations were undertaken on four mono-specific and two multi-specific communities, using herbaceous plant species from North-West Europe, presenting six contrasting aboveground functional traits involved in the HR increase. Results: An effect of dominant traits in the community was found on the HR, identified as the community-weighted leaf density. The non-additive effect of functional diversity on the HR could be explained by the presence of species presenting large stems in the communities with high functional diversity. Conclusion: We argued that functional diversity effect on the HR could change due to idiosyncratic effects of the plant traits, which would be influenced by soil properties, phylogeny diversity, and plant species interactions. These findings constitute an advancement in the understanding of plant trait assemblage on runoff and soil erosion processes.

Collapse of dispersal trait diversity across a long‐term chronosequence reveals a strong negative impact of frugivore extinctions on forest resilience

Abstract Understanding how seed dispersal disruption may alter plant community diversity and dynamics over a large temporal scale remains a challenge. Here, we use a long‐term chronosequence to compare changes in the richness and composition of different dispersal trait assemblages in communities established before and after human colonization in the Mascarene archipelago. Our study was located on Réunion on the slopes of the Piton de la Fournaise which is one of the most active volcanoes worldwide. We analysed 151 vegetation surveys on lava flows dated between 1401 AD and 1956 AD and in tropical rainforests established on older substrata. We defined five classes of substratum age, according to the well‐known chronology of native frugivore defaunation: ‘old substrata’ and [1401, 1665[ when frugivores were abundant and diverse before permanent human settlement; [1665, 1800[ when large‐bodied frugivore populations were strongly reduced; [1800, 1900[ when large‐bodied frugivores went extinct and small‐bodied frugivores were still abundant; [1900, 1956] decline in the populations of small‐bodied frugivores. Based on dispersal traits, we categorized 146 native woody species as anemochorous, small fleshy‐fruited or large fleshy‐fruited, i.e. plant of which fruit could not theoretically be dispersed by extant frugivores. Changes in dispersal trait diversity strongly correlated with the chronology of defaunation. Species‐rich communities settled before human colonization was strongly dominated by fleshy‐fruited species. Large fleshy‐fruited plants in the oldest communities settled after human colonization declined markedly and almost disappeared after 1800. The richness of small fleshy‐fruited plants decreased less rapidly across the chronosequence, with medium levels on [1665, 1800[ and [1800, 1900[ lava flows and low levels on [1900, 1956] lava flows. Conversely, the richness of anemochorous plants remained unchanged. Communities settled before human colonization had a similar composition. Fleshy‐fruited assemblages showed strong species loss across the chronosequence, while anemochorous assemblages showed strong species turnover, which was probably due to lower dispersal limitation. Synthesis. Our results provide the first insights into the tremendous impact that frugivore extinction has on plant colonization dynamics over 300 years. The dramatic loss of fleshy‐fruited plant diversity on historical lava flows highlights the irreplaceable dispersal role played by frugivores, especially large‐bodied species. The conservation of plant–animal mutualistic interactions is invaluable and refaunation efforts need to be undertaken in areas where frugivores have been extirpated.