Nitrogen availability affects the responses of marsh grass and sedge plants (Phragmites australis and Bolboschoenus planiculmis) to flooding time

Flooding time and external nitrogen (N) input have been projected to be the main threats to marsh ecosystems in the scenario of more intense flooding events and N deposition. How flooding and N addition experienced at different growth stages interact in determining phenotypic change remains scarce. We established a controlled experiment (3 flooding time treatments x 5 N addition levels) using two herbaceous marsh species (Phragmites australis and Bolboschoenus planiculmis) to assess the responses of six key traits to environmental changes and the indication of plant performance. Early flooding reduced plant height and aboveground biomass of P. australis and below/aboveground biomass ratio of B. planiculmis and increased below/aboveground biomass ratio of P. australis and root biomass of B. planiculmis, whereas late flooding reduced root biomass of P. australis and ramet number and aboveground biomass of B. planiculmis. The combination of flooding and high N (16 and 32 g N m-2) exerted negative effects on ramet number of both plant species. The interaction of early flooding and low-medium N (8 and 16 g N m-2) inhibited clonal/belowground biomass ratio of both plant species. The combination of early flooding and low N (0, 4 and 8 g N m-2) promoted root biomass and below/aboveground biomass ratio of P. australis. Ramet number, plant height, and root biomass explained 80-90 % of aboveground biomass variation of both plant species, and the contribution of ramet number was greater than that of the other two traits. These results highlight that the influence of flooding time and external N input on the performance of marsh plants depends on species identity. Meanwhile, the ramet number-plant height-root biomass (RHR) strategy is supposed to be the adaptation strategy of wetland clonal plants to environmental changes, and clonal reproductive traits should be incorporated into vegetation dynamics models for marsh plants.

Alpine plant species converge towards adopting elevation-specific resource-acquisition strategy in response to experimental early snow-melting

Snow-melt is one of the important factors limiting growth and survival of alpine plants. Changes in snow-melt timing have profound effects on eco-physiological characteristics of alpine plant species through alterations in growing season length. Here, we conducted a field experiment and studied species response to experimentally induced early snow-melting (ES) (natural vs. early) at an alpine site (Rohtang) in the western Himalaya region. Eco-physiological response of eight snow-bed restricted alpine plant species from different elevations (lower: 3850 m and upper: 4150 m amsl) and belonging to contrasting resource acquisition strategies (conservative and acquisitive) were studied after 2-years (2019 & 2020) of initiating ES field experiment. We estimated the functional traits related to leaf economic spectrum and physiological performance and assessed their pattern of phenotypic plasticity. Analysis by linear mixed effect model showed that both the 'conservative' and 'acquisitive' species had responded to ES with significant effects on species specific leaf area, leaf dry matter content, leaf thickness, leaf water content and sugar content. Our results also revealed that ES treatment induced significant increase in leaf C/N ratio (10.57 % to 13.65 %) and protein content (15.85 % to 20.76 %) at both the elevations, irrespective of species groups. The phenotypic plasticity was found to be low and was essentially species-specific. However, for leaf protein content, the upper elevation species exhibited a higher phenotypic plasticity (0.43 ± 0.18) than the lower elevation species (0.31 ± 0.21). Interestingly, we found that irrespective of species unique functional strategy, species adapt to perform more conservative at lower elevation and more acquisitive at upper elevation, in response to ES. We conclude that plants occurring at contrasting elevations respond differentially to ES. However, species showed capacity for short-term acclimation to future environmental conditions, but may be vulnerable, if their niche is occupied by new species with greater phenotypic plasticity and a superior competitive ability.

Aridity drives the variability of desert soil microbiomes across north-western China

Dryland covers >35 % of the terrestrial surface and the global extent of dryland increases due to the forecasted increase in aridity driven by climate change. Due to the climate change-driven aridity ecosystems, deserts provide one of the most hostile environments for microbial life and survival. Therefore, a detailed study was carried out to explore the deserts with different aridity levels (exposed to severe climate change) influence on microbial (bacteria, fungi, and protist) diversity patterns, assembly processes, and co-occurrence. The results revealed that the aridity (semi-arid, arid, and hyper-arid) patterns caused distinct changes in environmental heterogeneity in desert ecosystems. Similarly, microbial diversities were also reduced with increasing the aridity pattern, and it was found that environmental heterogeneity is highly involved in affecting microbial diversities under different ecological niches. Interestingly, it was found that certain microbes, including bacterial (Firmicutes), fungal (Sordariomycetes), and protistan (Ciliophora) abundance increased with increasing aridity levels, indicating that these microbes might possess the capability to tolerate the environmental stress conditions. Moreover, microbial community turnover analysis revealed that bacterial diversities followed homogenous selection, whereas fungi and protists were mostly driven by the dispersal limitation pattern. Co-occurrence network analysis showed that hyper-arid and arid conditions tightened the bacterial and fungal communities and had more positive associations compared to protistan. In conclusion, multiple lines of evidence were provided to shed light on the habitat specialization impact on microbial (bacteria, fungi, and protists) communities and composition under different desert ecosystems.

Drought intensity and post-drought precipitation determine vegetation recovery in a desert steppe in Inner Mongolia, China

Extreme drought events are expected to increase in frequency and severity, posing significant threats to ecosystems worldwide. While considerable research has been concentrated on the effects of climate extremes on the stability of grasslands, the process by which grassland productivity may recover after extreme drought events are still not well understood. Here, we conducted a four-year (2019-2022) recovery investigation after four-year's (2015-2018) extreme drought treatments of different intensities (control, press and pulse) to explore the vegetation recovery of desert-grassland ecosystems Inner Mongolia, China. Press drought involved a 66 % reduction in natural precipitation from May to August, while pulse drought reduced it by 100 % during June and July. We found that both press and pulse droughts led to a sharp decrease in aboveground net primary productivity (ANPP) after four years, primarily due to reduced growth, density, and productivity of annual and perennial plants. However, ANPP under pulse drought could recover fully after four years of stopping of drought treatment, and it could not under press drought. Additionally, community structure (i.e., species richness, plant density, and height) fully recovered within 1 year after the end of the two extreme drought treatments. Both plant density and height contributed to the ANPP recovery after press and pulse droughts. Structural equation modeling (SEM) results further revealed that the reduction in ANPP during the extreme drought was primarily due to a decrease in plant density caused by reduced soil water content. The recovery of ANPP in pulse drought was directly caused by increased soil water content in the post-extreme drought. These results suggest that drought intensity and precipitation determine ANPP recovery in a degraded desert steppe. Our findings are crucial for deepening understanding of the processes and mechanisms of ecosystem recovery after extreme drought, as well as for the successful management and protection of grassland ecosystems.

A functional perspective on the factors underpinning biomass-bound carbon stocks in coastal macrophyte communities

Coastal ecosystems have received international interest for their possible role in climate change mitigation, highlighting the importance of being able to assess and predict how changes in habitat distributions and their associated communities may impact the greenhouse gas sink potential of these vegetated seascapes. Importantly, the range and diversity of macrophytes within the vegetated seascape have different capacities to store C within their biomass and potentially sequester C depending on their functional trait characteristics. To bridge the present knowledge gaps in linking macrophyte traits to C storage in tissue, we (1) quantified biomass-bound C stocks within diverse macrophyte communities, separately for soft and hard bottom habitats and (2) explored the links between various traits of both vascular plants and macroalgae and their respective biomass-bound C stocks using structural equation modeling (SEM). We conducted a field survey where we sampled 6 soft bottom locations dominated by aquatic vascular plants and 6 hard bottom locations dominated by the brown algae Fucus vesiculosus in the Finnish archipelago. Macrophyte carbon stocks of hard bottom locations were an order of magnitude higher than those found in soft bottom locations. Biodiversity was associated with aquatic plant carbon stocks through mass ratio effects, highlighting that carbon stocks were positively influenced by the dominance of species with more acquisitive resource strategies, whereas age was the main driver of carbon in the mono-specific macroalgal communities. Overall, our results demonstrate that habitat type and dominating life-history strategies influenced the size of the organism-bound carbon stocks. Moreover, we showed the importance of accounting for the diversity of different traits to determine the drivers underpinning carbon storage in heterogenous seascapes composed of macrophyte communities with high functional diversity.

Isopod mouthpart traits respond to a tropical forest recovery gradient

Functional trait ecology has the potential to provide generalizable and mechanistic predictions of ecosystem function from data of species distributions and traits. The traits that are selected should both respond to environmental factors and influence ecosystem functioning. Invertebrate mouthpart traits fulfill these criteria, but are seldom collected, lack standardized measurement protocols, and have infrequently been investigated in response to environmental factors. We surveyed isopod species that consume plant detritus, and tree communities in 58 plots across primary and secondary forests in Singapore. We measured body dimensions (body size traits), pereopod and antennae lengths (locomotory traits), dimensions of mandible structures (morphological mouthpart traits), and mechanical advantages generated by mandible shape (mechanical mouthpart traits) for six isopod species found in these plots and investigated if these traits respond to changes in tree community composition, tree diversity, and forest structure. Morphological mouthpart traits responded to a tree compositional gradient reflecting forest recovery degree. Mouthpart features associated with greater consumption of litter (broader but less serrated/rugose lacinia mobilis [an important cutting and chewing structure on the mandible]) were most prevalent in abandoned plantation and young secondary forests containing disturbance-associated tree species. Feeding strategies associated with fungi grazing (narrower and more serrated/rugose lacinia mobilis) were most prevalent in late secondary forests containing later successional tree species. Since morphological mouthpart traits likely also predict consumption and excretion rates of isopods, these traits advance our understanding of environment-trait-ecosystem functioning relationships across contrasting tropical forest plots that vary in composition, disturbance history, and post-disturbance recovery.

Untangling the impact of plantation type and functional traits on ecosystem nutrient stocks in an experimentally restored forest ecosystem

The primary objective of ecological restoration is recovering biodiversity and ecosystem functioning. While a functional trait-based approach can help understand community assembly and ecosystem function recovery during ecological restoration, there still exists a knowledge gap in assessing how functional traits indicate the mediating roles of the plant community in response to forest restoration effects on ecosystem functions. This study applied the "response-effect trait" framework to investigate experimentally whether the treatment of plantation type has an impact on community trait compositions, which in turn could affect forest ecosystem nutrient stocks - here, carbon (C) and nitrogen (N) and phosphorus (P) stocks in tree, understory, litter and soil pools at an experimental station in subtropical China. We used structural equation models (SEMs) to examine the relationships among plantation type, community weighted mean of traits, and nutrient stocks in each pool. Our results show that most of the tree and understory traits studied were response traits to plantation type. Moreover, certain traits played a significant role in mediating plantation-type effects on C, N and P stocks for understory pool (e.g., understory stem specific density and specific leaf area, tree leaf phosphorus content), and for litter and soil pools (e.g., tree leaf carbon or phosphorus content, understory specific leaf area, leaf nitrogen or phosphorus content), known as "response-effect traits". For the tree pool, only effect traits, and no "response-effect" tree traits, were found for the N stock. Total effects of SEMs indicated that, understory or tree traits can have a greater impact than plantation type on understory or litter C, N or P stocks. After approximately 35 years of natural restoration, exotic plantations exhibited a different community trait characteristic from native plantations. The important roles of traits in mediating the effects of plantation type on non-tree pool C, N and P stocks were highlighted.

Functional trait diversity and aboveground biomass of herbaceous vegetation in temperate forests of Kashmir Himalaya

Studying functional trait diversity can provide crucial clues about the adaptive survival strategies of regional plant species pool. Despite large-scale trait datasets available worldwide, the plant trait data from many biodiversity hotpot regions, like the Himalaya is still scarce. In this study, we aimed to investigate the plant functional traits and aboveground biomass of understory herbaceous vegetation in temperate forests of Overa-Aru wildlife sanctuary of Kashmir Himalaya. We also investigate how these functional traits correlate and what is the magnitude of trait-biomass relationship across the herbaceous species pool. For this, we conducted field sampling and measured leaf functional traits and aboveground biomass of 38 plant species in the study region during peak growing season (July-August) in the year 2021. The results revealed a significant interspecific trait variability among the species studied. We observed a high variability in leaf size and type spectra of the species, with nanophyll and simple leaf lamina, respectively, the most common types among the species studied. The correlation analysis revealed that plant height was positively correlated with aboveground biomass. The variation partitioning analysis revealed that the plant height explained the maximum fraction of variation in aboveground biomass, while least by specific leaf area. Overall, the findings from the present study provide useful insights in understanding trait-trait relationship and trait-environment interaction at the regional scale and can also help in recognizing adaptive functional traits of plant species that determine plant survival under the changing climate in this Himalayan region.

The trait co-variation regulates the response of bryophytes to nitrogen deposition: A meta-analysis

The nitrogen deposition has the potential to alter the trait composition of plant communities by affecting the fitness and physiological adaptation of species, consequently exerting an influence on ecosystem processes. Despite the importance of bryophytes in nutrient and carbon dynamics across different ecosystems, there is a lack of research examining the relationship between nitrogen deposition and the co-variation of bryophyte traits. To address this gap, a meta-analysis was conducted using data from 27 independent studies to investigate potential associations between trait co-variation of bryophytes and nitrogen deposition. The results revealed that interspecific variability regulates the influence of nitrogen deposition on bryophytes by affecting trait co-variation. Multiple correspondence analysis identified six combinations of closely related traits. For example, species with unbranched main stems frequently exhibit robust leaf midribs, leading to leaf wrinkling and leaf clasping around the stem as a response to water loss. Some weft or mat species tend to obtain resources (nitrogen) through their scale hairs on the main stem. Some species with narrow leaves require leaf teeth to maintain a normal leaf shape. The subgroup analyses indicated that certain traits, including unbranched main stem, changes in leaf morphology, robust leaf midrib, main stem without scale hairs, narrow leaf, leaf margin with teeth, undeveloped apophysis, and erect capsule minimize interaction with pollutants and represent a resource strategy. Conversely, functional traits representing a resource acquisition strategy, such as branched main stem, no changes in leaf morphology, short and weak leaf midrib, main stem with scale hairs, broad leaf, leaf margin without teeth, developed apophysis, and non-erect capsule increase pollutant exposure. Overall, our results suggest that anthropogenic global change may significantly impact bryophytes due to changes in their individual physiology and colony ecological indicators caused by increased nitrogen deposition.

Divergence in functional traits in seven species of neotropical palms of different forest strata

Functional traits are morphological and physiological characteristics that determine growth, reproduction, and survival strategies. The leaf economics spectrum proposes two opposing life history strategies: species with an "acquisitive" strategy grow fast and exploit high-resource environments, while species with a "conservative" strategy emphasize survival and slow growth under low resource conditions. We analyzed intra and interspecific variation in nine functional traits related to biomass allocation and tissue quality in seven Neotropical palm species from understory and canopy strata. We expected that the level of resources of a stratum that a species typically exploits would determine the dominance of either the exploitative or conservative strategy, as well as degree of divergence in functional traits between species. If this is correct, then canopy species will show an acquisitive strategy emphasizing traits targeting a larger size, whereas understory species will show a conservative strategy with traits promoting efficient biomass allocation and survival in the shade. Two principal components (57.22% of the variation) separated palm species into: (a) canopy species whose traits were congruent with the acquisitive strategy and emphasized large size (i.e., diameter, height, carbon content, and leaf area), and (b) understory species whose traits were associated with efficient biomass allocation (i.e., dry mass fraction -DMF- and tissue density). As we unravel the variation in functional traits in palms, which make up a substantial proportion of the tropical flora, we gain a deeper understanding of how plants adapt to environmental gradients.

Similar seed preferences explain trophic ecology of functionally distinct, but co-occurring and closely related harvester ants

To understand how food resource use and partitioning by closely related species allows local coexistence, it is key to determine whether a species' diet reflects food availability or food preferences. Here, we analysed the diets, seed selection, and seed preferences of three closely related harvester ants: Messor barbarus, M. bouvieri, and M. capitatus. Sympatric within a Mediterranean shrubland, these species differ in foraging behaviour and worker polymorphism. For 2 years, we studied the ants' diets and seed selection patterns as well as the local availability of seeds. Additionally, we performed a seed-choice experiment using a paired comparison design, offering the ants seeds from eight native plant species. The three ant species had the same general diet, which was primarily granivorous. Although they all consumed a wide variety of seeds, they mostly selected seeds from a small subset of plant species. Despite their morphological and behavioural differences, the ants displayed similar seed preferences that were highly consistent with their diets and seed selection patterns. Our results support the idea that the trophic ecology of these three harvester ants is driven by similar seed preferences rather than by their morphological and behavioural differences. Seed diversity and abundance were high near the ants' nests, suggesting that seed availability is not limiting and could in fact favour local species coexistence.

Nitrogen addition changes the canopy biological characteristics of dominant tree species in an evergreen broad-leaved forest

Many studies have focused on the impact of nitrogen deposition on plants, but due to technical limitations, research on the responses of forest canopy to manipulated nitrogen deposition is relatively scarce. Based on a canopy nitrogen addition (CN) platform, this study used laboratory analysis and unmanned aerial vehicle (UAV) observations to assess the impact of CN on the canopy traits of dominant tree species (Engelhardia roxburghiana, Schima superba, and Castanea henryi) in an evergreen broad-leaved forest in China. The results showed that nitrogen application at 25 kg N ha-1 y-1 (CN25) and 50 kg N ha-1 y-1 (CN50) significantly increased the actual net photosynthetic rate (An) of all the three tree species. CN25 significantly increased superoxide dismutase (SOD), catalase (CAT), and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activities in C. henryi. CN50 significantly increased the leaf area of all the three tree species and significantly reduced the leaf thickness of C. henryi, and significantly increased the POD and Rubisco activities in S. superba and C. henryi. CN significantly changed the number of forest gaps, but did not significantly change the area of forest gaps within the sample plots. CN25 significantly decreased the vertical projection area but increased the canopy flowering coverage of S. superba in dominant directions. CN25 and CN50 significantly increased the flowering coverage of C. henryi in favorable directions. It is found that under long-term (10-year) nitrogen addition, the balance between carbon fixation and antioxidant defense functions of E. roxburghiana may be broken down, but the carbon assimilation, antioxidant capacity and reproduction potential of S. superba and C. henryi may be well coordinated, which will have a potential impact on the species composition and ecological functions of the evergreen broad-leaved forest. This study may also provide scientific basis for forest management in the context of enhanced atmospheric nitrogen deposition.

How ecological and evolutionary theory expanded the 'ideal weed' concept

Since Baker's attempt to characterize the 'ideal weed' over 50 years ago, ecologists have sought to identify features of species that predict invasiveness. Several of Baker's 'ideal weed' traits are well studied, and we now understand that many traits can facilitate different components of the invasion process, such as dispersal traits promoting transport or selfing enabling establishment. However, the effects of traits on invasion are context dependent. The traits promoting invasion in one community or at one invasion stage may inhibit invasion of other communities or success at other invasion stages, and the benefits of any given trait may depend on the other traits possessed by the species. Furthermore, variation in traits among populations or species is the result of evolution. Accordingly, evolution both prior to and after invasion may determine invasion outcomes. Here, we review how our understanding of the ecology and evolution of traits in invasive plants has developed since Baker's original efforts, resulting from empirical studies and the emergence of new frameworks and ideas such as community assembly theory, functional ecology, and rapid adaptation. Looking forward, we consider how trait-based approaches might inform our understanding of less-explored aspects of invasion biology ranging from invasive species responses to climate change to coevolution of invaded communities.

Is the relationship between body length and body mass consistent across habitats? A case study on Niphargus (Crustacea: Amphipoda)

Body size is one of the main characteristics of any organism and influences various aspects of individual's biology. In animal ecology, it represents a key functional trait that can be quantified using different measures and is often used as a proxy for different organismal functions. The way we quantify body size is critical in any study using this measure alone or to scale other organismal traits. It is especially important in groups that act as model systems across different fields of biological research. One of such groups are amphipods, which are at focus in many ecological studies where appropriate quantification of body size is needed. Here, we explored the relationship between body length and body mass in the largest freshwater amphipod genus Niphargus, and evaluated whether the two measures lead to different conclusions in a putative ecological study of species coexistence. We selected 16 species inhabiting two different subterranean habitats, cave lakes and cave streams. The relationship between log-transformed body mass and body length was linear in all species, but body mass increased steeper among species from cave lakes than from cave streams, reflecting the stouter body shape of the former. In the simulated ecological study, the comparisons of the two measures showed that they may yield different results: in 10 % of cases, body length detected differences between species when body mass did not and vice versa (13 %). Usage of body length or body mass can thus lead to different conclusions. We recommend avoiding direct transformations between body length and body mass in ecological studies. Whenever needed, such transformations should be done with caution using habitat-specific body mass - body length ratios.

Improved assessment of the impacts of plant protection products on certain soil ecosystem services requires better consideration of terrestrial microalgae and cyanobacteria

There is growing scientific and societal consciousness that the environmental risks and impacts of plant protection products (PPPs) cannot be properly assessed without considering ecosystem services. However, the science on this issue remains incomplete and fragmented, as recently illustrated in a collective scientific assessment that pointed out the limited knowledge on the risks and impacts of PPPs on soil ecosystem services, which are clearly overlooked. Beside soil ecosystem services, certain key players involved in these services are largely overlooked in the scientific literature on the risks and impacts of PPPs, namely soil microbial photosynthetic communities. Here, we followed the principles of evidence-based logic chain approaches to show the importance of considering these microorganisms when studying the impacts of PPPs on certain services provided by soil ecosystems, with a focus on regulating and maintenance services that play a role in the regulation of baseline flows and extreme events. Terrestrial microalgae and cyanobacteria are ubiquitous photosynthetic microorganisms that, together with other soil micro- and macro-organisms, play key roles in the ecosystem functions that underpin these ecosystem services. There is an extensive literature on the ecotoxicological effects of PPPs on different organisms including soil microorganisms, but studies concerning soil microbial photosynthetic communities are very scarce. However, there is scientific evidence that herbicides can have both direct and indirect impacts on these microbial photosynthetic communities. Given that they play key functional roles, we argue that soil microbial photosynthetic communities warrant greater attention in efforts to assess the environmental risks and impacts of PPPs and, ultimately, help preserve or restore the regulating and maintenance services provided by soil ecosystems.

Geographic range size and species morphology determines the organization of sponge host-guest interaction networks across tropical coral reefs

Sponges are widely spread organisms in the tropical reefs of the American Northwest-Atlantic Ocean, they structure ecosystems and provide services such as shelter, protection from predators, and food sources to a wide diversity of both vertebrates and invertebrates species. The high diversity of sponge-associated fauna can generate complex networks of species interactions over small and large spatial-temporal gradients. One way to start uncovering the organization of the sponge host-guest complex networks is to understand how the accumulated geographic area, the sponge morphology and, sponge taxonomy contributes to the connectivity of sponge species within such networks. This study is a meta-analysis based on previous sponge host-guest literature obtained in 65 scientific publications, yielding a total of 745 host-guest interactions between sponges and their associated fauna across the Caribbean Sea and the Gulf of Mexico. We analyzed the sponge species contribution to network organization in the Northwest Tropical Atlantic coral reefs by using the combination of seven complementary species-level descriptors and related this importance with three main traits, sponge-accumulated geographic area, functional sponge morphology, and sponges' taxonomy bias. In general, we observed that sponges with a widespread distribution and a higher accumulated geographic area had a greater network structural contribution. Similarly, we also found that Cup-like and Massive functional morphologies trend to be shapes with a greater contribution to the interaction network organization compared to the Erect and Crust-like morphos. Lastly, we did not detect a taxonomy bias between interaction network organization and sponges' orders. These results highlight the importance of a specific combination of sponge traits to promote the diversity of association between reef sponges and their guest species.

Climate and litter traits affect the response of litter decomposition to soil fauna

OBJECTIVES

Soil fauna plays a crucial role in contributing to litter breakdown, accelerating the decomposition rate and enhancing the biogeochemical cycle in terrestrial ecosystems. Comprehending the specific fauna role of functional species in litter decomposition is challenging due to their vast numbers and diversity. Climate and litter quality are widely acknowledged as dominant drives of litter decomposition across large spatial scales. However, the pattern of climate and litter quality modulates the effect of soil fauna on litter decomposition remains largely unexplored. To address this gap, we conducted an extensive analysis using data from 81 studies to investigate how climate and litter traits affects soil fauna in the decomposition.

DATA DESCRIPTION

The paper describes fauna body size, climate zones (tropical, subtropical and temperate), ecosystem types (forest, grassland, wetland and farmland), soil types (sand, loam and clay), decomposed duration (< 180, 180-360, > 360 days), litter initial traits, average annual temperature and precipitation. The litter traits encompass various parameters such as concentrations of carbon, nitrogen, phosphorus, potassium, lignin, cellulose, total phenol, condensed tannin, hydrolysable tannin and other nutrient traits. These comprehensive datasets provide valuable insights into the role of soil fauna on the decomposition at global scale. Furthermore, the data will give researchers keys to assess how climate, litter quality and soil fauna interact to determine decomposition rates.

Variation in leaf photosynthetic capacity within plant canopies: optimization, structural, and physiological constraints and inefficiencies

Leaf photosynthetic capacity (light-saturated net assimilation rate, AA) increases from bottom to top of plant canopies as the most prominent acclimation response to the conspicuous within-canopy gradients in light availability. Light-dependent variation in AA through plant canopies is associated with changes in key leaf structural (leaf dry mass per unit leaf area), chemical (nitrogen (N) content per area and dry mass, N partitioning between components of photosynthetic machinery), and physiological (stomatal and mesophyll conductance) traits, whereas the contribution of different traits to within-canopy AA gradients varies across sites, species, and plant functional types. Optimality models maximizing canopy carbon gain for a given total canopy N content predict that AA should be proportionally related to canopy light availability. However, comparison of model expectations with experimental data of within-canopy photosynthetic trait variations in representative plant functional types indicates that such proportionality is not observed in real canopies, and AA vs. canopy light relationships are curvilinear. The factors responsible for deviations from full optimality include stronger stomatal and mesophyll diffusion limitations at higher light, reflecting greater water limitations and more robust foliage in higher light. In addition, limits on efficient packing of photosynthetic machinery within leaf structural scaffolding, high costs of N redistribution among leaves, and limited plasticity of N partitioning among components of photosynthesis machinery constrain AA plasticity. Overall, this review highlights that the variation of AA through plant canopies reflects a complex interplay between adjustments of leaf structure and function to multiple environmental drivers, and that AA plasticity is limited by inherent constraints on and trade-offs between structural, chemical, and physiological traits. I conclude that models trying to simulate photosynthesis gradients in plant canopies should consider co-variations among environmental drivers, and the limitation of functional trait variation by physical constraints and include the key trade-offs between structural, chemical, and physiological leaf characteristics.

Stable functional structure despite high taxonomic variability across fungal communities in soils of old-growth montane forests

BACKGROUND

Major advances over the past decade in molecular ecology are providing access to soil fungal diversity in forest ecosystems worldwide, but the diverse functions and metabolic capabilities of this microbial community remain largely elusive. We conducted a field survey in montane old-growth broadleaved and conifer forests, to investigate the relationship between soil fungal diversity and functional genetic traits. To assess the extent to which variation in community composition was associated with dominant tree species (oak, spruce, and fir) and environmental variations in the old-growth forests in the Jade Dragon Snow Mountain in Yunnan Province, we applied rDNA metabarcoding. We also assessed fungal gene expression in soil using mRNA sequencing and specifically assessed the expression of genes related to organic matter decomposition and nutrient acquisition in ectomycorrhizal and saprotrophic fungi.

RESULTS

Our taxonomic profiling revealed striking shifts in the composition of the saprotrophic and ectomycorrhizal guilds among the oak-, fir-, and spruce-dominated forests. The core fungal microbiome comprised only ~ 20% of the total OTUs across all soil samples, although the overlap between conifer-associated communities was substantial. In contrast, seasonality and soil layer explained only a small proportion of the variation in community structure. However, despite their highly variable taxonomic composition, fungal guilds exhibited remarkably similar functional traits for growth-related and core metabolic pathways across forest associations, suggesting ecological redundancy. However, we found that the expression profiles of genes related to polysaccharide and protein degradation and nutrient transport notably varied between and within the fungal guilds, suggesting niche adaptation.

CONCLUSIONS

Overall, our metatranscriptomic analyses revealed the functional potential of soil fungal communities in montane old-growth forests, including a suite of specialized genes and taxa involved in organic matter decomposition. By linking genes to ecological traits, this study provides insights into fungal adaptation strategies to biotic and environmental factors, and sheds light on the importance of understanding functional gene expression patterns in predicting ecosystem functioning. Video Abstract.

Detecting sediment recovery below an offshore longline mussel farm: A macrobenthic Biological Trait Analysis (BTA)

Expansion of bivalve aquaculture offshore reports lower environmental impacts compared to inshore farms. Taking a Before-After Control-Impact approach, this study presents the first functional diversity analysis and long-term Biological Trait Analysis (BTA) of infauna functional traits following the development of the United Kingdom's first large-scale, offshore longline mussel farm. Located in an area historically impacted by mobile fishing gear, farm sites had the greatest number of taxa and abundance compared to control sites. Functional diversity varied significantly across treatments (farm, near control, far control); while Functional Diversity, Richness, Divergence and Dispersion increased over time within the farm, Functional Evenness and Redundancy decreased. Bioturbation, body size, diet, feeding mode, life span, motility, sediment position, sensitivity and substrate type were chosen for Community-level Weighted Mean analysis, depicting the most frequently affected biological traits by shellfish farming. Farm sites developed a wider range of traits enhancing ecosystem function and habitat recovery after years of seabed damage. Outcomes support the use of functional diversity and BTA analysis to perform ecosystem assessment, supporting decision-makers implement policy and management.

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

BACKGROUND AND AIMS

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.

METHODS

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.

KEY RESULTS

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.

CONCLUSIONS

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.

Linking ecotoxicological effects on biodiversity and ecosystem functions to impairment of ecosystem services is a challenge: an illustration with the case of plant protection products

There is growing interest in using the ecosystem services framework for environmental risk assessments of chemicals, including plant protection products (PPPs). Although this topic is increasingly discussed in the recent scientific literature, there is still a substantial gap between most ecotoxicological studies and a solid evaluation of potential ecotoxicological consequences on ecosystem services. This was recently highlighted by a collective scientific assessment (CSA) performed by 46 scientific experts who analyzed the international science on the impacts of PPPs on biodiversity, ecosystem functions, and ecosystem services. Here, we first point out the main obstacles to better linking knowledge on the ecotoxicological effects of PPPs on biodiversity and ecological processes with ecosystem functions and services. Then, we go on to propose and discuss possible pathways for related improvements. We describe the main processes governing the relationships between biodiversity, ecological processes, and ecosystem functions in response to effects of PPP, and we define categories of ecosystem functions that could be directly linked with the ecological processes used as functional endpoints in investigations on the ecotoxicology of PPPs. We then explore perceptions on the possible links between these categories of ecosystem functions and ecosystem services among a sub-panel of the scientific experts from various fields of environmental science. We find that these direct and indirect linkages still need clarification. This paper, which reflects the difficulties faced by the multidisciplinary group of researchers involved in the CSA, suggests that the current gap between most ecotoxicological studies and a solid potential evaluation of ecotoxicological consequences on ecosystem services could be partially addressed if concepts and definitions related to ecological processes, ecosystem functions, and ecosystem services were more widely accepted and shared within the ecotoxicology community. Narrowing this gap would help harmonize and extend the science that informs decision-making and policy-making, and ultimately help to better address the trade-off between social benefits and environmental losses caused by the use of PPPs.

Global investigation of lake habitat coupling by fishes

Habitat coupling, where consumers acquire resources from different habitats, plays an important role in ecosystem functioning. In this study, we provide a global investigation of lake habitat coupling by freshwater fishes between littoral (nearshore) and pelagic (open water) zones and elucidate the extent to which magnitude of coupling varies according to environmental context and consumer traits. We consider the influence of lake factors (surface area, depth, shoreline complexity, and annual temperature), relative trophic position of consumers, fish community species richness, and fish morphological traits on habitat coupling by fishes. Using a worldwide dataset consisting of fish stable isotope values (δ¹³C and δ¹⁵N), we developed an index of habitat coupling, and used Bayesian hierarchical and non-hierarchical beta regressions to estimate the effects of environmental lake context and morphological traits on habitat coupling by fishes. Our results show high rates of habitat coupling among fishes globally with marked taxonomic differences in the magnitude and variation. Habitat coupling was higher in lower elevation lakes and in regions characterized by relatively colder climates, whereas other environmental context factors had little or no effects on habitat coupling. Furthermore, habitat coupling was associated with several locomotion and feeding traits, but independent from species maximum body length. Overall, we highlight the prevalence of multiple resources supporting fish populations and suggest future research identify implications to ecosystem functioning that may result from alterations to habitat coupling by fishes.

Functional diversity in an Andean subpáramo affected by wildfire in Colombia

Recently, the Andean subpáramo in Colombia has experienced severe wildfires, but little is known about the functional composition of recovering or not after a wildfire. Therefore, we examined the functional community composition subpáramo affected by fire in 2016. We documented how functional traits changed 31 months after the disturbance and compared them with an unburned site. We sampled from one to two years after the fire every four months, then registered all recruits in 16 5 × 5m plots. New individuals were classified into strategy functional groups based on the traits of persistence and dispersal. The first group was stem type and regeneration mechanism (seedling and resprout), and the second was fruit type and dispersal mode. We investigated the degree to which functional diversity changes plant communities over time (woody and non-woody), and we compared it with an unburned site. The most relevant results showed that resprouts and seed regenerated increased post-fire time and significant differences between sampling periods. The anemochory is the most relevant dispersal mode that indicates the community capacity to colonize the new gaps opened by the fire rapidly. We discuss how wildfire appears to be a triggering factor for persistence and dispersal strategy groups in subpáramo burned given their characteristics of tolerance to stress. For this reason, a greater functional divergence between the ecosystems studied post-fire recovery has been related to higher levels of biodiversity at the landscape scale due to the high degree of endemism and significant differences in species composition between páramos.

Legume effects in a native community invaded by alien Asteraceae in a multi-species comparison

Facilitation has been a long-neglected type of interaction but received more attention recently. Legumes are commonly involved in facilitative interactions due to their nitrogen fixation. Facilitative interactions are so far underappreciated yet potentially important for biological invasions, especially given increasing numbers of alien species. In a common garden experiment using 30 annual Asteraceae species (neophytes, archaeophytes, plus some natives), grown in communities with or without legume presence, we measured functional traits and fitness in focal Asteraceae, as well as nitrogen characteristics of Asteraceae and two native community phytometer species. We investigated how legume presence affects relationships between trait and nitrogen concentration and Asteraceae fitness; and whether mechanisms of facilitation in legume presence and its effects on aboveground performance differ among native phytometer, neophyte, and archaeophyte Asteraceae using the δ¹⁵N natural abundance method. Lower specific leaf area was associated with higher aboveground biomass and seed production, with a stronger effect in legume absence. Nitrogen concentration had a positive relationship with biomass, but did not generally increase seed production. Our results hint at N facilitation for the native grass phytometer Festuca rupicola when growing in legume presence, whereas the forb Potentilla argentea and 27 alien Asteraceae species did not indicate facilitative effects. Intriguingly, direct legume facilitation in native phytometer species was only detected when growing with archaeophytes neighbors, not with neophytes. This hints at varied mechanisms of competition for nitrogen between natives and alien species of different residence time and deepens the understanding of altered facilitative leguminous effects in alien species presence.