The global spectrum of plant form and function

Climate regulation processes are linked to the functional composition of plant communities in European forests, shrublands, and grasslands

Terrestrial ecosystems affect climate by reflecting solar irradiation, evaporative cooling, and carbon sequestration. Yet very little is known about how plant traits affect climate regulation processes (CRPs) in different habitat types. Here, we used linear and random forest models to relate the community-weighted mean and variance values of 19 plant traits (summarized into eight trait axes) to the climate-adjusted proportion of reflected solar irradiation, evapotranspiration, and net primary productivity across 36,630 grid cells at the European extent, classified into 10 types of forest, shrubland, and grassland habitats. We found that these trait axes were more tightly linked to log evapotranspiration (with an average of 6.2% explained variation) and the proportion of reflected solar irradiation (6.1%) than to net primary productivity (4.9%). The highest variation in CRPs was explained in forest and temperate shrubland habitats. Yet, the strength and direction of these relationships were strongly habitat-dependent. We conclude that any spatial upscaling of the effects of plant communities on CRPs must consider the relative contribution of different habitat types.

Moss functional trait ecology: Trends, gaps, and biases in the current literature

Functional traits are critical tools in plant ecology for capturing organism-environment interactions based on trade-offs and making links between organismal and ecosystem processes. While broad frameworks for functional traits have been developed for vascular plants, we lack the same for bryophytes, despite an escalation in the number of studies on bryophyte functional trait in the last 45 years and an increased recognition of the ecological roles bryophytes play across ecosystems. In this review, we compiled data from 282 published articles (10,005 records) that focused on functional traits measured in mosses and sought to examine trends in types of traits measured, capture taxonomic and geographic breadth of trait coverage, reveal biases in coverage in the current literature, and develop a bryophyte-function index (BFI) to describe the completeness of current trait coverage and identify global gaps to focus research efforts. The most commonly measured response traits (those related to growth/reproduction in individual organisms) and effect traits (those that directly affect community/ecosystem scale processes) fell into the categories of morphology (e.g., leaf area, shoot height) and nutrient storage/cycling, and our BFI revealed that these data were most commonly collected from temperate and boreal regions of Europe, North America, and East Asia. However, fewer than 10% of known moss species have available functional trait information. Our synthesis revealed a need for research on traits related to ontogeny, sex, and intraspecific plasticity and on co-measurement of traits related to water relations and bryophyte-mediated soil processes.

Seed mucilage in temperate grassland species is unrelated to moisture requirements

Myxospermy, the release of seed mucilage upon hydration, plays multiple roles in seed biology. Here, we explore whether seed mucilage occurs in a suite of temperate grassland species to test if the prevalence of species producing seed mucilage is associated with habitat type or seed characteristics. Seventy plant species found in wet or dry North American temperate grasslands were tested for the presence of seed mucilage through microscopic examination of seeds imbibed with histochemical stain for mucilage. Mucilage production was compared among species with different moisture requirements and seed mass. In this study, 43 of 70 of species tested produced seed mucilage. Seed mucilage did not differ based on habitat type, species moisture requirements, or seed mass. Most seed mucilage was non-adherent and did not remain stuck to the seed after extrusion. Seed mucilage was a common trait in the surveyed temperate grassland species and was observed in 61% of evaluated species. Surprisingly, seed mucilage was more common in temperate grasslands than in previous ecological surveys from arid/semiarid systems, which found 10%-31% myxospermous species. Given the high prevalence, seed mucilage may influence seedling ecology in temperate grasslands and requires further investigation.

Functional traits shape plant-plant interactions and recruitment in a hotspot of woody plant diversity

Understanding and predicting recruitment in species-rich plant communities requires identifying functional determinants of both density-independent performance and interactions. In a common-garden field experiment with 25 species of the woody plant genus Protea, we varied the initial spatial and taxonomic arrangement of seedlings and followed their survival and growth during recruitment. Neighbourhood models quantified how six key functional traits affect density-independent performance, interaction effects and responses. Trait-based neighbourhood models accurately predicted individual survival and growth from the initial spatial and functional composition of species-rich experimental communities. Functional variation among species caused substantial variation in density-independent survival and growth that was not correlated with interaction effects and responses. Interactions were spatially restricted but had important, predominantly competitive, effects on recruitment. Traits increasing the acquisition of limiting resources (water for survival and soil P for growth) mediated trade-offs between interaction effects and responses. Moreover, resprouting species had higher survival but reduced growth, likely reinforcing the survival-growth trade-off in adult plants. Resource acquisition of juvenile plants shapes Protea community dynamics with acquisitive species with strong competitive effects suffering more from competition. Together with functional determinants of density-independent performance, this makes recruitment remarkably predictable, which is critical for efficient restoration and near-term ecological forecasts of species-rich communities.

Vertical variation in leaf functional traits of Parashorea chinensis with different canopy layers

Introduction

Canopy species need to shift their ecological adaptation to improve light and water resources utilization, and the study of intraspecific variations in plant leaf functional traits based at individual scale is of great significance for evaluating plant adaptability to climate change.

Methods

In this study, we evaluate how leaf functional traits of giant trees relate to spatial niche specialization along a vertical gradient. We sampled the tropical flagship species of Parashorea chinensis around 60 meters tall and divided their crowns into three vertical layers. Fourteen key leaf functional traits including leaf morphology, photosynthetic, hydraulic and chemical physiology were measured at each canopy layer to investigate the intraspecific variation of leaf traits and the interrelationships between different functional traits. Additionally, due to the potential impact of different measurement methods (in-situ and ex-situ branch) on photosynthetic physiological parameters, we also compared the effects of these two gas exchange measurements.

Results and discussion

In-situ measurements revealed that most leaf functional traits of individual-to-individual P. chinensis varied significantly at different canopy heights. Leaf hydraulic traits such as midday leaf water potential (MWP) and leaf osmotic potential (OP) were insignificantly correlated with leaf photosynthetic physiological traits such as maximal net assimilation rate per mass (A mass). In addition, great discrepancies were found between in-situ and ex-situ measurements of photosynthetic parameters. The ex-situ measurements caused a decrease by 53.63%, 27.86%, and 38.05% in A mass, and a decrease of 50.00%, 19.21%, and 27.90% in light saturation point compared to the in-situ measurements. These findings provided insights into our understanding of the response mechanisms of P. chinensis to micro-habitat in Xishuangbanna tropical seasonal rainforests and the fine scale adaption of different resultant of decoupled traits, which have implications for understanding ecological adaption strategies of P. chinensis under environmental changes.

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.

Plant life history strategies vary in subtropical forests with different disturbance histories: an assessment of biodiversity, biomass, and functional traits

Disturbance alters environmental conditions in forests. Plants growing in forests with different disturbance histories in diverse environments may adopt varying life history strategies, but few studies focus on this effect. This study comprehensively investigated plant biodiversity, biomass, and functional traits in subtropical forests with two different disturbance histories in east China to explore differences in life history strategies. Biodiversity was slightly higher in disturbed compared to conserved forests. Significantly higher biomass was measured in conserved relative to disturbed evergreen broadleaved forests (P < 0.05). In conserved forests, leaf tissue density (LTD) was significantly higher and leaf thickness (LT), leaf dry matter content (LDMC), twig tissue density (TTD), twig dry matter content (TDMC), bark tissue density (BTD) and dry matter content (BDMC), and stem tissue density (STD) and dry matter content (SDMC) were significantly lower than in disturbed forests (P < 0.05). In terms of associated plant biodiversity, biomass, and functional traits, conserved forests adopted a resource acquisition strategy, reducing biodiversity and developing multiple functional traits such as high leaf area and specific leaf area and low LT, LDMC, TTD, TDMC, BTD, BDMC, STD, and SDMC to support a high biomass accumulation rate. Disturbed forests adopted a resource conservation strategy, enhancing biodiversity and developing converse trait combinations to lower the rate of biomass accumulation. A comprehensive investigation of plant biodiversity, biomass, and functional traits and subsequent assessment of plant life history strategies in conserved and disturbed forests will aid investigations of regional biodiversity and carbon reserves, contribute data to the TRY and Chinese plant trait databases, and improve ecological management and restoration efforts in east China.

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.

Future changes in key plant traits across Central Europe vary with biogeographical status, woodiness, and habitat type

Many plant traits covary with environmental gradients, reflecting shifts in adaptive strategies and thus informing about potential consequences of future environmental change for vegetation and ecosystem functioning. Yet, the evidence of trait-environment relationships (TERs) remains too heterogeneous for reliable predictions, partially due to insufficient consideration of trait syndromes specific to certain growth forms and habitats. Moreover, it is still unclear whether non-native and native plants' traits align similarly along environmental gradients, limiting our ability to assess the impacts of future plant invasions. Using a Bayesian multilevel modelling framework, we assess TERs for native and non-native woody and herbaceous plants across six broad habitat types in Central Europe at a resolution of c. 130 km2 and use them to project trait change under future environmental change scenarios until 2081-2100. We model TERs between three key plant traits (maximum height, Hmax; specific leaf area, SLA; seed mass, SM) and individual environmental factors (7 climate variables and % urban land cover) and estimate trait change summed across all environmental effects. We also quantify the change in the average trait difference between native and non-native plants. Our models depict multiple TERs, with important differences attributed to biogeographical status and woodiness within and across habitat types. The overall magnitude of trait change is projected to be greater for non-native than native taxa and to increase under more extreme scenarios. Native woody plant assemblages may generally experience a future increase across all three traits, whereas woody non-natives may decline in Hmax and increase in SLA and SM. Herbaceous Hmax is estimated to increase and SLA to decrease in most habitats. The obtained trait projections highlight conditions of competitive advantage of non-native plants over natives and vice versa and can serve as starting points for projecting future changes in ecosystem functions and services.

Fluctuations in resource availability shape the competitive balance among non-native plant species

Fluctuating resource availability plays a critical role in determining non-native plant invasions through mediating the competitive balance between non-native and native species. However, the impact of fluctuating resource availability on interactions among non-native species remains largely unknown. This represents a barrier to understanding invasion mechanisms, particularly in habitats that harbor multiple non-native species with different responses to fluctuating resource availability. To examine the responses of non-native plant species to nutrient fluctuations, we compared the growth of each of 12 non-native species found to be common in local natural areas to nutrients supplied at a constant rate or supplied as a single large pulse in a pot experiment. We found that seven species produced more biomass with pulsed nutrients compared to constant nutrients (hereafter "benefitting species"), while the other five species did not differ between nutrient enrichment treatments (hereafter "non-benefitting species"). To investigate how nutrient fluctuations influence the interactions among non-native plant species, we established experimental non-native communities in the field with two benefitting and two non-benefitting non-native species. Compared with constant nutrient supply, the single large pulse of nutrient did not influence community biomass, but strongly increased the biomass and cover of the benefitting species and decreased those of the non-benefitting species. Furthermore, the benefitting species had higher leaf N content and greater plant height when nutrients were supplied as a single large pulse than at a constant rate, whereas the non-benefitting species showed no differences in leaf N content and were shorter when nutrients were supplied as a single large pulse than at a constant rate. Our results add to the growing evidence that the individual responses of non-native species to nutrient fluctuation are species-specific. More importantly, benefitting species were favored by nutrients coming in a pulse, while non-benefitting ones were favored by nutrients coming constantly when they grew together. This suggests that nutrient fluctuations can mediate the competitive balance among non-native plants and may thus determine their invasion success in a community harboring multiple non-native plant species.

Improper data practices erode the quality of global ecological databases and impede the progress of ecological research

The scientific community has entered an era of big data. However, with big data comes big responsibilities, and best practices for how data are contributed to databases have not kept pace with the collection, aggregation, and analysis of big data. Here, we rigorously assess the quantity of data for specific leaf area (SLA) available within the largest and most frequently used global plant trait database, the TRY Plant Trait Database, exploring how much of the data were applicable (i.e., original, representative, logical, and comparable) and traceable (i.e., published, cited, and consistent). Over three-quarters of the SLA data in TRY either lacked applicability or traceability, leaving only 22.9% of the original data usable compared with the 64.9% typically deemed usable by standard data cleaning protocols. The remaining usable data differed markedly from the original for many species, which led to altered interpretation of ecological analyses. Though the data we consider here make up only 4.5% of SLA data within TRY, similar issues of applicability and traceability likely apply to SLA data for other species as well as other commonly measured, uploaded, and downloaded plant traits. We end with suggested steps forward for global ecological databases, including suggestions for both uploaders to and curators of databases with the hope that, through addressing the issues raised here, we can increase data quality and integrity within the ecological community.

Nitrogen availability and plant functional composition modify biodiversity-multifunctionality relationships

Biodiversity typically increases multiple ecosystem functions simultaneously (multifunctionality) but variation in the strength and direction of biodiversity effects between studies suggests context dependency. To determine how different factors modulate the diversity effect on multifunctionality, we established a large grassland experiment manipulating plant species richness, resource addition, functional composition (exploitative vs. conservative species), functional diversity and enemy abundance. We measured ten above- and belowground functions and calculated ecosystem multifunctionality. Species richness and functional diversity both increased multifunctionality, but their effects were context dependent. Richness increased multifunctionality when communities were assembled with fast-growing species. This was because slow species were more redundant in their functional effects, whereas different fast species promoted different functions. Functional diversity also increased multifunctionality but this effect was dampened by nitrogen enrichment and enemy presence. Our study suggests that a shift towards fast-growing communities will not only alter ecosystem functioning but also the strength of biodiversity-functioning relationships.

When do plant hydraulics matter in terrestrial biosphere modelling?

The ascent of water from the soil to the leaves of vascular plants, described by the study of plant hydraulics, regulates ecosystem responses to environmental forcing and recovery from stress periods. Several approaches to model plant hydraulics have been proposed. In this study, we introduce four different versions of plant hydraulics representations in the terrestrial biosphere model T&C to understand the significance of plant hydraulics to ecosystem functioning. We tested representations of plant hydraulics, investigating plant water capacitance, and long-term xylem damages following drought. The four models we tested were a combination of representations including or neglecting capacitance and including or neglecting xylem damage legacies. Using the models at six case studies spanning semiarid to tropical ecosystems, we quantify how plant xylem flow, plant water storage and long-term xylem damage can modulate overall water and carbon dynamics across multiple time scales. We show that as drought develops, models with plant hydraulics predict a slower onset of plant water stress, and a diurnal variability of water and carbon fluxes closer to observations. Plant water storage was found to be particularly important for the diurnal dynamics of water and carbon fluxes, with models that include plant water capacitance yielding better results. Models including permanent damage to conducting plant tissues show an additional significant drought legacy effect, limiting plant productivity during the recovery phase following major droughts. However, when considering ecosystem responses to the observed climate variability, plant hydraulic modules alone cannot significantly improve the overall model performance, even though they reproduce more realistic water and carbon dynamics. This opens new avenues for model development, explicitly linking plant hydraulics with additional ecosystem processes, such as plant phenology and improved carbon allocation algorithms.

Global patterns and drivers of plant-soil microbe interactions

Plant-soil feedback (PSF) is an important mechanism determining plant community dynamics and structure. Understanding the geographic patterns and drivers of PSF is essential for understanding the mechanisms underlying geographic plant diversity patterns. We compiled a large dataset containing 5969 observations of PSF from 202 studies to demonstrate the global patterns and drivers of PSF for woody and non-woody species. Overall, PSF was negative on average and was influenced by plant attributes and environmental settings. Woody species PSFs did not vary with latitude, but non-woody PSFs were more negative at higher latitudes. PSF was consistently more positive with increasing aridity for both woody and non-woody species, likely due to increased mutualistic microbes relative to soil-borne pathogens. These findings were consistent between field and greenhouse experiments, suggesting that PSF variation can be driven by soil legacies from climates. Our findings call for caution to use PSF as an explanation of the latitudinal diversity gradient and highlight that aridity can influence plant community dynamics and structure across broad scales through mediating plant-soil microbe interactions.

On functional groups and forest dynamics

Functional trait variation measured on continuous scales has helped ecologists to unravel important ecological processes. However, forest ecologists have recently moved back toward using functional groups. There are pragmatic and biological rationales for focusing on functional groups. Both of these approaches have inherent limitations including binning clearly continuous distributions, poor trait-group matching, and narrow conceptual frameworks for why groups exist and how they evolved. We believe the pragmatic use of functional groups due to data deficiencies will eventually erode. Conversely, we argue that existing conceptual frameworks for why a limited number of tree functional groups may exist is a useful, but flawed, starting point for modeling forests that can be improved through the consideration of unmeasured axes of functional variation.

Leaf-age and petiole biomass play significant roles in leaf scaling theory

Foliage leaves are essential for plant survival and growth, and how plants allocate biomass to their leaves reveals their economic and ecological strategies. Prior studies have shown that leaf-age significantly influences leaf biomass allocation patterns. However, unravelling the effects of ontogeny on partitioning biomass remains a challenge because it is confounded by the effects of environmental factors. Here, we aim to elucidate whether leaf-age affects the allocation to the lamina and petiole by examining leaves of known age growing in the same general environmental context. We sampled 2698 Photinia serratifolia leaves developing in the same environment from April to November 2021, representing eight leaf-ages (n > 300 for each leaf-age). Petiole and lamina biomass, and lamina area were measured to evaluate the scaling relationships using reduced major axis regression protocols. The bootstrap percentile method was used to determine the differences in scaling exponents among the different leaf-ages. ANOVA with Tukey's HSD was used to compare the ratios of petiole and lamina biomass to lamina area across the leaf-ages. Correlation tests were used to determine if exponents, intercepts, and ratios differed significantly across the different leaf-ages. The data indicated that (i) the ratio of petiole and lamina biomass to lamina area and the scaling exponent of lamina biomass versus lamina area correlate positively with leaf-age, and (ii) the scaling exponent of petiole biomass versus lamina area correlates negatively with leaf-age. Leaf maturation process involves an inverse proportional allocation between lamina and petiole biomass for expanding photosynthetic area. This phenomenon underscores the effect of leaf-age on biomass allocation and the importance of adopting an ontogenetic perspective when entertaining plant scaling theories and unravelling the principles governing shifts in biomass allocation throughout the leaf lifespan.

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.

Global erosion of terrestrial environmental space by artificial light at night

Artificial light at night (ALAN) disrupts natural light cycles, with biological impacts that span from behaviour of individual organisms to ecosystem functions, and across bacteria, fungi, plants and animals. Global consequences have almost invariably been inferred from the geographic distribution of ALAN. How ALAN is distributed in environmental space, and the extent to which combinations of environmental conditions with natural light cycles have been lost, is also key. Globally (between 60°N and 56°S), we ordinated four bioclimatic variables at 1.61 * 1.21 km resolution to map the position and density of terrestrial pixels within nighttime environmental space. We then used the Black Marble Nighttime Lights product to determine where direct ALAN emissions were present in environmental space in 2012 and how these had expanded in environmental space by 2022. Finally, we used the World Atlas of Artificial Sky Brightness to determine the proportion of environmental space that is unaffected by ALAN across its spatial distribution. We found that by 2012 direct ALAN emissions occurred across 71.9 % of possible nighttime terrestrial environmental conditions, with temperate nighttime environments and highly modified habitats disproportionately impacted. From 2012 to 2022 direct ALAN emissions primarily grew within 34.4 % of environmental space where it was already present, with this growth concentrated in tropical environments. Additionally considering skyglow, just 13.2 % of environmental space now only experiences natural light cycles throughout its distribution. With opportunities to maintain much of environmental space under such cycles fast disappearing, the removal, reduction and amelioration of ALAN from areas of environmental space in which it is already widespread is critical.

Linking functional composition moments of the sub-Mediterranean ecotone with environmental drivers

Introduction

Functional trait-based approaches are extensively applied to the study of mechanisms governing community assembly along environmental gradients. These approaches have been classically based on studying differences in mean values among species, but there is increasing recognition that alternative metrics of trait distributions should be considered to decipher the mechanisms determining community assembly and species coexistence. Under this framework, the main aim of this study is to unravel the effects of environmental conditions as drivers of plant community assembly in sub-Mediterranean ecotones.

Methods

We set 60 plots in six plant communities of a sub-Mediterranean forest in Central Spain, and measured key above- and belowground functional traits in 411 individuals belonging to 19 species, along with abiotic variables. We calculated community-weighted mean (CWM), skewness (CWS) and kurtosis (CWK) of three plant dimensions, and used maximum likelihood techniques to analyze how variation in these functional community traits was driven by abiotic factors. Additionally, we estimated the relative contribution of intraspecific trait variability and species turnover to variation in CWM.

Results and discussion

The first three axes of variation of the principal component analyses were related to three main plant ecological dimensions: Leaf Economics Spectrum, Root Economics Spectrum and plant hydraulic architecture, respectively. Type of community was the most important factor determining differences in the functional structure among communities, as compared to the role of abiotic variables. We found strong differences among communities in their CWMs in line with their biogeographic origin (Eurosiberian vs Mediterranean), while differences in CWS and CWK indicate different trends in the functional structure among communities and the coexistence of different functional strategies, respectively. Moreover, changes in functional composition were primarily due to intraspecific variability.

Conclusion

We observed a high number of strategies in the forest with the different communities spreading along the acquisitive-conservative axis of resource-use, partly matching their Eurosiberian-Mediterranean nature, respectively. Intraspecific trait variability, rather than species turnover, stood as the most relevant factor when analyzing functional changes and assembly patterns among communities. Altogether, our data support the notion that ecotones are ecosystems where relatively minor environmental shifts may result in changes in plant and functional composition.

Response of leaf functional traits to soil nutrients in the wet and dry seasons in a subtropical forest on an island

Introduction

Island ecosystems often have a disproportionate number of endemic species and unique and fragile functional characteristics. However, few examples of this type of ecosystem have been reported.

Methods

We conducted a comprehensive field study on Neilingding Island, southern China. The leaf samples of 79 subtropical forest tree species were obtained and their functional traits were studied in the dry and wet seasons to explain the relationships between plant functional traits and soil nutrients.

Results

We found a greater availability of soil moisture content (SMC) and nutrients in the wet season than in the dry season. The values of wet season soil available phosphorus (5.97 mg·kg-1), SMC (17.67%), and soil available potassium (SAK, 266.96 mg·kg-1) were significantly higher than those of the dry season. The leaf dry matter content, specific leaf weight, leaf density, leaf total carbon, leaf total nitrogen, leaf total calcium, and the N/P and C/P ratios of leaves were all significantly higher in the dry season than in the wet season, being 18.06%, 12.90%, 12.00%, 0.17%, 3.41%, 9.02%, 26.80%, and 24.14% higher, respectively. In contrast, the leaf area (51.01 cm2), specific leaf area (152.76 cm2·g-1), leaf water content (0.59%), leaf total nitrogen (1.31%), leaf total phosphorus (0.14%), and leaf total magnesium (0.33%) were much lower in the dry season than in the wet one. There were significant pairwise correlations between leaf functional traits, but the number and strength of correlations were significantly different in the dry and wet seasons. The SAK, soil total phosphorus (STP), and pH impacted plant leaf functional traits in the dry season, whereas in the wet season, they were affected by SAK, STP, pH, and NO3- (nitrate).

Discussion

Both soil nutrients and water availability varied seasonally and could cause variation in a number of leaf traits.

Differences in functional niche hypervolume among four types of forest vegetation and their environmental determinants across various climatic regions in China

Functional traits play an important role in studying the functional niche in plant communities. However, it remains unclear whether the functional niches of typical forest plant communities in different climatic regions based on functional traits are consistent. Here, we present data for 215 woody species, encompassing 11 functional traits related to three fundamental niche dimensions (leaf economy, mechanical support, and reproductive phenology). These data were collected from forests across four climatic zones in China (tropical, subtropical, warm-temperate, and cold-temperate) or sourced from the literature. We calculated the functional niche hypervolume, representing the range of changes in the multidimensional functional niche. This metric quantifies how many functional niche spaces are occupied by existing plants in the community. Subsequently, we analyzed differences in functional niche hypervolume and their associated environmental factors across different types of forest vegetation. The results indicate that the functional niche hypervolume and the degree of forest vegetation overlap decrease with increasing latitude (e.g., from tropical rainforest to cold temperate coniferous forest). The total explanatory power of both climate and soil factors on the variation in functional niche hypervolume was 50%, with climate factors exhibiting a higher explanatory power than soil factors. Functional niche hypervolume is positively correlated with climate factors (annual mean temperature and annual precipitation) and negatively correlated with soil factors (soil pH, soil organic matter content, soil total nitrogen content, and soil total phosphorus content). Among these factors, annual mean temperature, soil pH, and soil total nitrogen content most significantly affect the difference in functional niche hypervolume among forest vegetation. Our study emphasizes the significant variation in the functional niche hypervolume among typical forest vegetation in China.

Evolution of masting in plants is linked to investment in low tissue mortality

Masting, a variable and synchronized variation in reproductive effort is a prevalent strategy among perennial plants, but the factors leading to interspecific differences in masting remain unclear. Here, we investigate interannual patterns of reproductive investment in 517 species of terrestrial perennial plants, including herbs, graminoids, shrubs, and trees. We place these patterns in the context of the plants' phylogeny, habitat, form and function. Our findings reveal that masting is widespread across the plant phylogeny. Nonetheless, reversion from masting to regular seed production is also common. While interannual variation in seed production is highest in temperate and boreal zones, our analysis controlling for environment and phylogeny indicates that masting is more frequent in species that invest in tissue longevity. Our modeling exposes masting-trait relationships that would otherwise remain hidden and provides large-scale evidence that the costs of delayed reproduction play a significant role in the evolution of variable reproduction in plants.

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.

Body size determines multitrophic soil microbiota community assembly associated with soil and plant attributes in a tropical seasonal rainforest

To understand soil biodiversity we need to know how soil communities are assembled. However, the relationship between soil community assembly and environmental factors, and the linkages between soil microbiota taxonomic groups and their body sizes, remain unexplored in tropical seasonal rainforests. Systematic and stratified random sampling was used to collect 243 soil and organism samples across a 20-ha plot in a tropical seasonal rainforest in southwestern China. High-throughput sequencing, variation analysis and principal coordinates of neighbourhood matrices were performed. Soil community composition, spatial distribution and assembly processes based on propagule size (including archaea, bacteria, fungi and nematodes) were investigated. The results showed that: (i) the community assembly of small soil microorganisms (bacteria, fungi) was mostly influenced by stochastic processes while that of larger soil organisms (nematodes) was more deterministic; (ii) the independent effects of habitat (including soil and topographic variables) and its interaction with plant attributes for community structure significantly decreased with increasing body size; and (iii) plant leaf phosphorus directly influenced the spatial distribution of soil-available phosphorus, which indicates their indirect impact on the assembly of the soil communities. Our data suggest that the assembly of multitrophic soil communities can be explained to some extent by changes in above-ground plant attributes. This highlights the importance of above- and below-ground linkages in influencing multitrophic soil microbiota community assembly.

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.

The carbon balance of plants: economics, optimization, and trait spectra in a historical perspective

Over fifty years have passed since the publication of Harold Mooney's formative paper, "The Carbon Balance of Plants" on pages 315-346 of Volume 3 (1972) of Annual Review of Ecology and Systematics. Arguably, the conceptual framework presented in that paper, and the work by Mooney and his students leading up to the paper, provided the foundational principles from which core disciplines emerged in plant economic theory, functional trait theory and, more generally, plant physiological ecology. Here, we revisit the primary impacts of those early discoveries to understand how researchers constructed major concepts in our understanding of plant adaptations, and where those concepts are likely to take us in the near future. The discipline of functional trait ecology, which is rooted in the principles of evolutionary and economic optimization, has captured the imagination of the plant physiological ecology research community, though its emphasis has shifted toward predicting species distributions and ecological roles across resource gradients. In the face of 'big-data' research pursuits that are revealing trait expression patterns at the cellular level and mass and energy exchange patterns at the planetary scale, an opportunity exists to reconnect the principles of plant carbon balance and evolutionary optimization with trait origins at the genetic and cellular scales and trait impacts at the global scale.

Relationships among sporophytic and gametophytic traits of 27 subtropical montane moss species

PREMISE

Moss sporophytes differ strongly in size and biomass partitioning, potentially reflecting reproductive and dispersal strategies. Understanding how sporophyte traits are coordinated is essential for understanding moss functioning and evolution. This study aimed to answer: (1) how the size and proportions of the sporophyte differ between moss species with and without a prominent central strand in the seta, (2) how anatomical and morphological traits of the seta are related, and (3) how sporophytic biomass relates to gametophytic biomass and nutrient concentrations.

METHODS

We studied the relationships between seta anatomical and morphological traits, the biomass of seta, capsule, and gametophyte, and carbon, nitrogen, and phosphorus concentrations of 27 subtropical montane moss species.

RESULTS

(1) Moss species with a prominent central strand in the seta had larger setae and heavier capsules than those without a prominent strand. (2) With increasing seta length, setae became thicker and more rounded for both groups, while in species with a prominent central strand, the ratio of transport-cell area to epidermal area decreased. (3) In both groups, mosses with greater gametophytic biomass tended to have heavier sporophytes, but nitrogen and phosphorus concentrations in the gametophyte were unrelated to sporophytic traits.

CONCLUSIONS

Our study highlights that the central strand in the seta may have an important functional role and affect the allometry of moss sporophytes. The coordinated variations in sporophyte morphological and anatomical traits follow basic biomechanical principles of cylinder-like structures, and these traits relate only weakly to the gametophytic nutrient concentrations. Research on moss sporophyte functional traits and their relationships to gametophytes is still in its infancy but could provide important insights into their adaptative strategies.

Plant trait relationships are maintained within a major crop species: lack of artificial selection signal and potential for improved agronomic performance

The exploration of phenotypic spaces of large sets of plant species has considerably increased our understanding of diversification processes in the plant kingdom. Nevertheless, such advances have predominantly relied on interspecific comparisons that hold several limitations. Here, we grew in the field a unique set of 179 inbred lines of durum wheat, Triticum turgidum spp. durum, characterized by variable degrees of artificial selection. We measured aboveground and belowground traits as well as agronomic traits to explore the functional and agronomic trait spaces and to investigate trait-to-agronomic performance relationships. We showed that the wheat functional trait space shared commonalities with global cross-species spaces previously described, with two main axes of variation: a root foraging axis and a slow-fast trade-off axis. Moreover, we detected a clear signature of artificial selection on the variation of agronomic traits, unlike functional traits. Interestingly, we identified alternative phenotypic combinations that can optimize crop performance. Our work brings insightful knowledge about the structure of phenotypic spaces of domesticated plants and the maintenance of phenotypic trade-offs in response to artificial selection, with implications for trade-off-free and multi-criteria selection in plant breeding.

Experimental warming altered plant functional traits and their coordination in a permafrost ecosystem

Knowledge about changes in plant functional traits is valuable for the mechanistic understanding of warming effects on ecosystem functions. However, observations have tended to focus on aboveground plant traits, and there is little information about changes in belowground plant traits or the coordination of above- and belowground traits under climate warming, particularly in permafrost ecosystems. Based on a 7-yr field warming experiment, we measured 26 above- and belowground plant traits of four dominant species, and explored community functional composition and trait networks in response to experimental warming in a permafrost ecosystem on the Tibetan Plateau. Experimental warming shifted community-level functional traits toward more acquisitive values, with earlier green-up, greater plant height, larger leaves, higher photosynthetic resource-use efficiency, thinner roots, and greater specific root length and root nutrient concentrations. However, warming had a negligible effect in terms of functional diversity. In addition, warming shifted hub traits which have the highest centrality in the network from specific root area to leaf area. These results demonstrate that above- and belowground traits exhibit consistent adaptive strategies, with more acquisitive traits in warmer environments. Such changes could provide an adaptive advantage for plants in response to environmental change.

Testing the hierarchy of predictability in grassland restoration across a gradient of environmental severity

Ecological restoration is critical for recovering degraded ecosystems but is challenged by variable success and low predictability. Understanding which outcomes are more predictable and less variable following restoration can improve restoration effectiveness. Recent theory asserts that the predictability of outcomes would follow an order from most to least predictable from coarse to fine community properties (physical structure > taxonomic diversity > functional composition > taxonomic composition) and that predictability would increase with more severe environmental conditions constraining species establishment. We tested this "hierarchy of predictability" hypothesis by synthesizing outcomes along an aridity gradient with 11 grassland restoration projects across the United States. We used 1829 vegetation monitoring plots from 227 restoration treatments, spread across 52 sites. We fit generalized linear mixed-effects models to predict six indicators of restoration outcomes as a function of restoration characteristics (i.e., seed mixes, disturbance, management actions, time since restoration) and used variance explained by models and model residuals as proxies for restoration predictability. We did not find consistent support for our hypotheses. Physical structure was among the most predictable outcomes when the response variable was relative abundance of grasses, but unpredictable for total canopy cover. Similarly, one dimension of taxonomic composition related to species identities was unpredictable, but another dimension of taxonomic composition indicating whether exotic or native species dominated the community was highly predictable. Taxonomic diversity (i.e., species richness) and functional composition (i.e., mean trait values) were intermittently predictable. Predictability also did not increase consistently with aridity. The dimension of taxonomic composition related to the identity of species in restored communities was more predictable (i.e., smaller residuals) in more arid sites, but functional composition was less predictable (i.e., larger residuals), and other outcomes showed no significant trend. Restoration outcomes were most predictable when they related to variation in dominant species, while those responding to rare species were harder to predict, indicating a potential role of scale in restoration predictability. Overall, our results highlight additional factors that might influence restoration predictability and add support to the importance of continuous monitoring and active management beyond one-time seed addition for successful grassland restoration in the United States.

Variability in seed salinity tolerance in an island coastal community

BACKGROUND AND AIMS

Islands, with their long coastlines and increased vulnerability to sea level rise, offer compelling opportunities to investigate the salinity tolerance of coastal plants. Seeds are generally more vulnerable than other plant stages to increased stressors. The aim of this study was to characterize salinity tolerance during germination across a diverse pool of 21 species from 14 plant families found in coastal communities throughout the Hawaiian Islands in order to increase our general understanding of coastal plant ecology for conservation and restoration.

METHODS

Seeds of each species were exposed to unfiltered/untreated seawater (35 ppt total salinity) and two salinity treatments (10 and 20 ppt) in which the seawater was diluted with distilled water, and germination percent and timing were compared to seeds in a distilled water control. Non-germinated seeds were then tested for recovery germination. We quantified and compared germination percent, time and recovery among species and across salinity levels and tested for heterogeneity related to seed size, dormancy class, habit and threatened status.

KEY RESULTS

Although salinity tolerance varied considerably among species, salinity exposure generally reduced and delayed germination. The greatest effects were detected at higher salinity levels. Recovery germination overall was higher for seeds that had been exposed to higher salinity. None of the factors we explored emerged as predictors of salinity tolerance except seed mass, which tended to enhance germination at higher salinity.

CONCLUSIONS

Species responses to salinity exposure indicate high vulnerability of coastal systems to increased salinity stress, and variability among species could lead to shifts in community assembly and composition under sea level rise. These results can help guide coastal ecosystem conservation and restoration management decisions in the face of climate change.

Nitrogen addition strengthens the stabilizing effect of biodiversity on productivity by increasing plant trait diversity and species asynchrony in the artificial grassland communities

Background and aims

Nitrogen (N) enrichment usually weakens the stabilizing effect of biodiversity on productivity. However, previous studies focused on plant species richness and thus largely ignored the potential contributions of plant functional traits to stability, even though evidence is increasing that functional traits are stronger predictors than species richness of ecosystem functions.

Methods

We conducted a common garden experiment manipulating plant species richness and N addition levels to quantify effects of N addition on relations between species richness and functional trait identity and diversity underpinning the 'fast-slow' economics spectrum and community stability.

Results

Nitrogen addition had a minor effect on community stability but increased the positive effects of species richness on community stability. Increasing community stability was found in the species-rich communities dominated by fast species due to substantially increasing temporal mean productivity relative to its standard deviation. Furthermore, enhancement in 'fast-slow' functional diversity in species-rich communities dominated by fast species under N addition increased species asynchrony, resulting in a robust biodiversity-stability relationship under N addition the artificial grassland communities.

Conclusion

The findings demonstrate mechanistic links between plant species richness, 'fast-slow' functional traits, and community stability under N addition, suggesting that dynamics of biodiversity-stability relations under global changes are the results of species-specific responses of 'fast-slow' traits on the plant economics spectrum.

Quercus wutaishanica shrub affects temperate forest community composition and soil properties under different restoration stage

Quercus wutaishanica is the dominant tree species in the natural ecosystem restoration of temperate forests in China, and it plays an active role in maintaining ecological balance. However, little is known about how ecosystem versatility develops during the restoration of forest ecosystems dominated by Q. wutaishanica. In this study, we investigated the species composition of the Q. wutaishanica community, soil nutrients, and their functional traits at various restoration stages, and comprehensively analyzed the correlations among them. At the early stage of restoration (10 years of restoration), there were Spiraea pubescens and Syringa pubescens in Q. wutaishanica community (87% of the total species), while had a larger niche width. In the middle of restoration (30 years of restoration), shannon and evenness indices were the largest, while soil total carbon, ammonium nitrogen and chlorophyll content of Q. wutaishanica leaves were the highest; among them, soil total carbon was 15.7% higher than that in 10 years of restoration, 32.4% higher than that in 40 years of restoration, ammonium nitrogen was 71.7% higher than that in 40 years of restoration, and chlorophyll content was 217.9% higher than that in 10 years of restoration, and 51.8% higher than that in 40 years of restoration. At the later stage of restoration (40 years of restoration), Lonicera ferdinandii occupied the dominant ecological niche, and soil available nitrogen, available phosphorus content and leaf thickness were the largest; while AN was 10.9% higher than that of 10 years of restoration, 16.5% higher than that of 30 years of restoration, AP was 60.6% higher than that of 10 years of restoration, 21.6% higher than that of 30 years of restoration, leaf thickness was 22.3% higher than that of 10 years of restoration, 84.9% higher than that of 30 years of restoration. However, the restriction of various soil nutrients was reduced. Our study highlighted the effectiveness of soil resource availability in plant communities during restoration, reduced competition for light among plants, and altered species richness. Furthermore, changes in the interrelationship between plant community composition and leaf functional traits of the dominant species responded positively to community restoration. These results further deepen our understanding of forest management and restoration of forest communities. In the future, it is necessary to comprehensively consider the influence of various factors on forest community restoration.

Phylogeny more than plant height and leaf area explains variance in seed mass

Although variation in seed mass can be attributed to other plant functional traits such as plant height, leaf size, genome size, growth form, leaf N and phylogeny, until now, there has been little information on the relative contributions of these factors to variation in seed mass. We compiled data consisting of 1071 vascular plant species from the literature to quantify the relationships between seed mass, explanatory variables and phylogeny. Strong phylogenetic signals of these explanatory variables reflected inherited ancestral traits of the plant species. Without controlling phylogeny, growth form and leaf N are associated with seed mass. However, this association disappeared when accounting for phylogeny. Plant height, leaf area, and genome size showed consistent positive relationship with seed mass irrespective of phylogeny. Using phylogenetic partial R2s model, phylogeny explained 50.89% of the variance in seed mass, much more than plant height, leaf area, genome size, leaf N, and growth form explaining only 7.39%, 0.58%, 1.85%, 0.06% and 0.09%, respectively. Therefore, future ecological work investigating the evolution of seed size should be cautious given that phylogeny is the best overall predictor for seed mass. Our study provides a novel avenue for clarifying variation in functional traits across plant species, improving our better understanding of global patterns in plant traits.

Plant functional traits and biodiversity can reveal the response of ecosystem functions to grazing

Plant functional traits can elucidate the response of plant communities and ecosystems to biotic and abiotic disturbances. However, whether livestock consume more aboveground biomass (AGB) in communities dominated by species with 'acquisitive' traits or in communities where biodiversity is high is not well known. Here, we measured 22 functional traits of the grazing communities and control communities in a Mongolian Plateau desert steppe. The effects of grazing on AGB, CWM traits, species diversity, and functional diversity (FD) were analysed, furthermore, we estimated the grazing impact by using the log response ratio (LRR, an increasing value shows a higher grazing impact) and investigated the correlations between the LRR, plant growth, and community-weighted mean (CWM) traits and diversity indices. We found that grazing significantly increased the CWM dry matter content and carbon-to‑nitrogen ratio and decreased the CWM height, specific leaf area (SLA), and nitrogen and phosphorus contents. The AGB decreased, while species diversity and FD increased under grazing treatments. Additionally, we found that plant traits and biodiversity could predict the response of AGB to grazing, the LRR was higher in patches dominated by species with 'acquisitive' foliage and in patches with higher biodiversity; in these patches, plant growth was lower. In the study area, the response of CWM traits to grazing suggests an avoidance strategy, which may be more conducive for adapting to low resource utilization environments. Also, the relationship between the CWM traits and the LRR indicated that the effect of grazing on AGB was mainly related to the selective foraging of herbivores. In addition, patches preferred by livestock may not recover quickly, leading to slow growth and thus reduced biomass under grazing treatments after prolonged grazing.

Three main dimensions reflected by national SDG performance

Unraveling the complexity of the 17 interacting sustainable development goals (SDGs) is crucial for their achievement. Empirically revealing the dimensions of the SDGs helps generalize the dominant features of SDGs and better understand their drivers. Here, using a database of 166 countries' progress toward achieving each individual SDG, we found that about 70% of the variability of national SDG performance can be captured by three dimensions: socioeconomic development at the expense of resource and climate, the environment, and development at the expense of equality. Moreover, these dimensions are mainly affected by the economy; as gross domestic product (GDP) per capita increases, the first dimension increases monotonically, the environment dimension decreases and then increases, and the inequality dimension increases and then decreases. Our findings indicate a dim prospect of eventually achieving all SDGs because of the conflicts between economic growth and resource and climate goals under the current development paradigm, highlighting the importance of sustainable transformation.

Plant biodiversity offsets negative effects of metals and metalloids soil multi-contamination on ecosystem multifunctionality

Despite increasing metals and metalloids (MM) human-driven soil contamination, how it simultaneously alters biodiversity and ecosystem functioning remains unknown. We used a wide gradient of a 170-year-old MM soil multi-contamination in Mediterranean scrublands to assess the effects of soil multi-contamination on multiple plant biodiversity facets, microbial communities and ecosystem multifunctionality (EMF). We found an overall positive effect of plant biodiversity on EMF mediated by microbial communities, and allowing offsetting the negative impacts of MM soil multi-contamination, especially on soil water holding capacity and nitrogen content. The diversity of distant plant lineages was the key facet promoting EMF by enhancing microbial communities, whereas the subordinate species richness altered EMF. By developing a holistic approach of these complex relationships between soil multi-contamination, plant biodiversity, microbial communities and ecosystem functioning, our results reveal the potential of plant biodiversity, and especially the diversity of evolutionary distant species, to offset the alteration of ecosystem functioning by MM soil multi-contamination. In this worldwide decade of ecosystems restoration, our study helps to identify relevant facets of plant biodiversity promoting contaminated ecosystem functioning, which is crucial to guide and optimize management efforts aiming to restore ecosystems and preserve human health.

Short-term responses of ecosystem multifunctionality to fire severity are modulated by fire-induced impacts on plant and soil microbial communities

This study represents a first attempt to shed light into the mechanisms that modulate the response of ecosystem multifunctionality (EMF) to fire severity in post-fire landscapes. We specifically investigated the role played by fire-induced changes on above and belowground communities in the modulation of EMF responses at short-term after fire. For this purpose, we estimated EMF using an averaging approach from three ecosystem functions (carbon regulation, decomposition and soil fertility) and their standardized functional indicators in field plots burned at low and high fire severity 1-year after a wildfire occurred in a Mediterranean ecosystem in the central region of Spain. Plant taxonomic and functional richness, and the bacterial and fungal taxonomic richness, were measured in the plots as community properties with a potential intermediate control over fire severity effects on EMF. The ecological effects of fire severity on above and belowground communities were important in shaping EMF as evidenced by Structural Equation Modeling (SEM). Indeed, the evidenced shrinkage exerted by high fire severity on EMF at short-term after fire was not direct, but modulated by fire-induced effects on the plant functional richness and the microbial taxonomic richness. However, EMF variation was more strongly modulated by indirect effects of fire severity on the biodiversity of soil microbial communities, than by the effects on the plant communities. Particularly, the fungal community exerted the strongest intermediate control (standardized SEM β coefficient = 0.62), which can be linked to the differential response of bacterial (β = -0.36) and fungal (β = -0.84) communities to fire severity evidenced here. Our findings demonstrate that the effects of fire severity on above and belowground communities are important drivers of short-term ecosystem functioning. Efforts tailored to secure the provision of multiple functions should be focused on promoting the recovery on soil microbial communities under high-severity scenarios.

Within-individual leaf trait variation increases with phenotypic integration in a subtropical tree diversity experiment

Covariation of plant functional traits, that is, phenotypic integration, might constrain their variability. This was observed for inter- and intraspecific variation, but there is no evidence of a relationship between phenotypic integration and the functional variation within single plants (within-individual trait variation; WTV), which could be key to understand the extent of WTV in contexts like plant-plant interactions. We studied the relationship between WTV and phenotypic integration in c. 500 trees of 21 species in planted forest patches varying in species richness in subtropical China. Using visible and near-infrared spectroscopy (Vis-NIRS), we measured nine leaf morphological and chemical traits. For each tree, we assessed metrics of single and multitrait variation to assess WTV, and we used plant trait network properties based on trait correlations to quantify phenotypic integration. Against expectations, strong phenotypic integration within a tree led to greater variation across leaves. Not only this was true for single traits, but also the dispersion in a tree's multitrait hypervolume was positively associated with tree's phenotypic integration. Surprisingly, we only detected weak influence of the surrounding tree-species diversity on these relationships. Our study suggests that integrated phenotypes allow the variability of leaf phenotypes within the organism and supports that phenotypic integration prevents maladaptive variation.

The worldwide allometric relationship in anatomical structures for plant roots

The cortex (i.e., absorptive tissue) and stele (transportive vascular tissue) are fundamental to the function of plant roots. Unraveling how these anatomical structures are assembled in absorptive roots is essential for our understanding of plant ecology, physiology, and plant responses to global environmental changes. In this review, we first compile a large data set on anatomical traits in absorptive roots, including cortex thickness and stele radius, across 698 observations and 512 species. Using this data set, we reveal a common root allometry in absorptive root structures, i.e., cortex thickness increases much faster than stele radius with increasing root diameter (hereafter, root allometry). Root allometry is further validated within and across plant growth forms (woody, grass, and liana species), mycorrhiza types (arbuscular mycorrhiza, ectomycorrhiza, and orchid mycorrhizas), phylogenetic gradients (from ferns to Orchidaceae), and environmental change scenarios (e.g., elevation of atmospheric CO2 concentration and nitrogen fertilization). These findings indicate that root allometry is common in plants. Importantly, root allometry varies greatly across species. We then summarize recent research on the mechanisms of root allometry and potential issues regarding these mechanisms. We further discuss ecological and evolutionary implications of root allometry. Finally, we propose several important research directions that should be pursued regarding root allometry.

A global assessment of the Raunkiaeran shortfall in plants: geographic biases in our knowledge of plant traits

This article is part of the Special Collection ‘Global plant diversity and distribution’. See https://www.newphytologist.org/global-plant-diversity for more details.

Life history strategies of soil bacterial communities across global terrestrial biomes

The life history strategies of soil microbes determine their metabolic potential and their response to environmental changes. Yet these strategies remain poorly understood. Here we use shotgun metagenomes from terrestrial biomes to characterize overarching covariations of the genomic traits that capture dominant life history strategies in bacterial communities. The emerging patterns show a triangle of life history strategies shaped by two trait dimensions, supporting previous theoretical and isolate-based studies. The first dimension ranges from streamlined genomes with simple metabolisms to larger genomes and expanded metabolic capacities. As metabolic capacities expand, bacterial communities increasingly differentiate along a second dimension that reflects a trade-off between increasing capacities for environmental responsiveness or for nutrient recycling. Random forest analyses show that soil pH, C:N ratio and precipitation patterns together drive the dominant life history strategy of soil bacterial communities and their biogeographic distribution. Our findings provide a trait-based framework to compare life history strategies of soil bacteria.

The global biogeography of tree leaf form and habit

Understanding what controls global leaf type variation in trees is crucial for comprehending their role in terrestrial ecosystems, including carbon, water and nutrient dynamics. Yet our understanding of the factors influencing forest leaf types remains incomplete, leaving us uncertain about the global proportions of needle-leaved, broadleaved, evergreen and deciduous trees. To address these gaps, we conducted a global, ground-sourced assessment of forest leaf-type variation by integrating forest inventory data with comprehensive leaf form (broadleaf vs needle-leaf) and habit (evergreen vs deciduous) records. We found that global variation in leaf habit is primarily driven by isothermality and soil characteristics, while leaf form is predominantly driven by temperature. Given these relationships, we estimate that 38% of global tree individuals are needle-leaved evergreen, 29% are broadleaved evergreen, 27% are broadleaved deciduous and 5% are needle-leaved deciduous. The aboveground biomass distribution among these tree types is approximately 21% (126.4 Gt), 54% (335.7 Gt), 22% (136.2 Gt) and 3% (18.7 Gt), respectively. We further project that, depending on future emissions pathways, 17-34% of forested areas will experience climate conditions by the end of the century that currently support a different forest type, highlighting the intensification of climatic stress on existing forests. By quantifying the distribution of tree leaf types and their corresponding biomass, and identifying regions where climate change will exert greatest pressure on current leaf types, our results can help improve predictions of future terrestrial ecosystem functioning and carbon cycling.

Resource co-limitation of community biomass but not structure of an alpine grassland

Anthropogenic environmental changes are influencing the structure and function of many ecological communities, but their underlying mechanisms are often poorly understood. We conducted a 7-year field experiment to explore the ecological consequences of nitrogen (N) and phosphorous (P) enrichment in a high-altitude Tibetan alpine grassland. We found that the enrichment of both N and P, but not either alone, increased plant above- and belowground biomass. In contrast, N, but not P, enrichment reduced species richness and altered plant phylogenetic diversity and structure. Whereas plant species loss and changes in phylogenetic structure were mainly driven by higher soil manganese levels under N addition, they were mainly driven by increased plant belowground biomass under the addition of both N and P. Our study highlights the resource co-limitation of community biomass but not the structure of the study grassland, while also identifying soil metal toxicity and belowground competition as important mechanisms driving community changes following nutrient amendment.

Fine-root traits are devoted to the allocation of foliar phosphorus fractions of desert species under water and phosphorus-poor environments

Traits of leaves and fine roots are expected to predict the responses and adaptation of plants to their environments. Whether and how fine-root traits (FRTs) are associated with the allocation of foliar phosphorus (P) fractions of desert species in water- and P-poor environments, however, remains unclear. We exposed seedlings of Alhagi sparsifolia Shap. (hereafter Alhagi) treated with two water and four P-supply levels for three years in open-air pot experiments and measured the concentrations of foliar P fractions, foliar traits, and FRTs. The allocation proportion of foliar nucleic acid-P and acid phosphatase (APase) activity of fine roots were significantly higher by 45.94 and 53.3% in drought and no-P treatments relative to well-watered and high-P treatments, whereas foliar metabolic-P and structural-P were significantly lower by 3.70 and 5.26%. Allocation proportions of foliar structural-P and residual-P were positively correlated with fine-root P (FRP) concentration, but nucleic acid-P concentration was negatively correlated with FRP concentration. A tradeoff was found between the allocation proportion to all foliar P fractions relative to the FRP concentration, fine-root APase activity, and amounts of carboxylates, followed by fine-root morphological traits. The requirement for a link between the aboveground and underground tissues of Alhagi was generally higher in the drought than the well-watered treatment. Altering FRTs and the allocation of P to foliar nucleic acid-P were two coupled strategies of Alhagi under conditions of drought and/or low-P. These results advance our understanding of the strategies for allocating foliar P by mediating FRTs in drought and P-poor environments.

Maximum stem diameter predicts liana population demography

Determining population demographic rates is fundamental to understanding differences in species' life-history strategies and their capacity to coexist. Calculating demographic rates, however, is challenging and requires long-term, large-scale censuses. Body size may serve as a simple predictor of demographic rate; can it act as a proxy for demographic rate when those data are unavailable? We tested the hypothesis that maximum body size predicts species' demographic rate using repeated censuses of the 77 most common liana species on the Barro Colorado Island, Panama (BCI) 50-ha plot. We found that maximum stem diameter does predict species' population turnover and demography. We also found that lianas on BCI can grow to the enormous diameter of 635 mm, indicating that they can store large amounts of carbon and compete intensely with tropical canopy trees. This study is the first to show that maximum stem diameter can predict plant species' demographic rates and that lianas can attain extremely large diameters. Understanding liana demography is particularly timely because lianas are increasing rapidly in many tropical forests, yet their species-level population dynamics remain chronically understudied. Determining per-species maximum liana diameters in additional forests will enable systematic comparative analyses of liana demography and potential influence across forest types.

Data-driven identification of major axes of functional variation in bacteria

The discovery of major axes of correlated functional variation among species and habitats has revealed the fundamental trade-offs structuring both functional and taxonomic diversity in eukaryotes such as plants. Whether such functional axes exist in the bacterial realm and whether they could explain bacterial taxonomic turnover among ecosystems remains unknown. Here, we use a data-driven approach to leverage global genomic and metagenomic datasets to reveal the existence of major axes of functional variation explaining both evolutionary differentiation within Bacteria and their ecological sorting across diverse habitats. We show that metagenomic variation among bacterial communities from various ecosystems is structured along a few axes of correlated functional pathways. Similar clusters of traits explained phylogenetic trait variation among >16,000 bacterial genomes, suggesting that functional turnover among bacterial communities from distinct habitats does not only result from the differential filtering of similar functions among communities, but also from phylogenetic correlations among these functions. Concordantly, functional pathways associated with trait clusters that were most important for defining functional turnover among bacterial communities were also those that had the highest phylogenetic signal in the bacterial genomic phylogeny. This study overall underlines the important role of evolutionary history in shaping contemporary distributions of bacteria across ecosystems.

Extent of intraspecific trait variability in ecologically central and marginal populations of a dominant alpine plant across European mountains

BACKGROUND AND AIMS

Studying trait variability and restricted gene flow between populations of species can reveal species dynamics. Peripheral populations commonly exhibit lower genetic diversity and trait variability due to isolation and ecological marginality, unlike central populations experiencing gene flow and optimal conditions. This study focused on Carex curvula, the dominant species in alpine acidic meadows of European mountain regions. The species is sparser in dry areas such as the Pyrenees and Balkans, compared to the Central-Eastern Alps and Carpathians. We hypothesized that distinct population groups could be identified based on their mean functional trait values and their correlation with the environment; we predicted that ecologically marginal populations would have stronger trait correlations, lower within-population trait variability (intraspecific trait variability, ITV) and lower genetic diversity than populations of optimal habitats.

METHODS

Sampling was conducted in 34 populations that spanned the entire distribution range of C. curvula. We used hierarchical clustering to identify emergent functional groups of populations, defined by combinations of multiple traits associated with nutrient economy and drought tolerance (e.g. specific leaf area, anatomy). We contrasted the geographical distribution of these groups in relation to environment and genetic structure. We compared pairwise trait relationships, within-population trait variation (ITV) and neutral genetic diversity between groups.

KEY RESULTS

Our study identified emergent functional groups of populations. Those in the southernmost ranges, specifically the Pyrenees and Balkan region, showed drought-tolerant trait syndromes and correlated with indicators of limited water availability. While we noted a decline in population genetic diversity, we did not observe any significant changes in ITV in ecologically marginal (peripheral) populations.

CONCLUSIONS

Our research exemplifies the relationship between ecological marginality and geographical peripherality, which in this case study is linked to genetic depauperation but not to reduced ITV. Understanding these relationships is crucial for understanding the biogeographical factors shaping trait variation.

Functional and ecological diversification of underground organs in Solanum

The evolution of geophytes in response to different environmental stressors is poorly understood largely due to the great morphological variation in underground plant organs, which includes species with rhizomatous structures or underground storage organs (USOs). Here we compare the evolution and ecological niche patterns of different geophytic organs in Solanum L., classified based on a functional definition and using a clade-based approach with an expert-verified specimen occurrence dataset. Results from PERMANOVA and Phylogenetic ANOVAs indicate that geophytic species occupy drier areas, with rhizomatous species found in the hottest areas whereas species with USOs are restricted to cooler areas in the montane tropics. In addition, rhizomatous species appear to be adapted to fire-driven disturbance, in contrast to species with USOs that appear to be adapted to prolonged climatic disturbance such as unfavorable growing conditions due to drought and cold. We also show that the evolution of rhizome-like structures leads to changes in the relationship between range size and niche breadth. Ancestral state reconstruction shows that in Solanum rhizomatous species are evolutionarily more labile compared to species with USOs. Our results suggest that underground organs enable plants to shift their niches towards distinct extreme environmental conditions and have different evolutionary constraints.

Functional response and resistance to drought in seedlings of six shrub species with contrasting leaf traits from the Mediterranean Basin and California

Extreme drought events during post-fire regeneration are becoming increasingly frequent in Mediterranean-type ecosystems. Understanding how plants with different traits and origins respond to such conditions during early life stages is therefore critical for assessing the effect of climate change. Here, seedlings of three Cistus (semi-deciduous malacophylls from the Mediterranean Basin) and three Ceanothus (evergreen sclerophylls from California) species, two post-fire seeder genera with contrasting leaf traits, were subjected to complete water deprivation for 3 months in a common garden experiment. The leaf and plant structure and plant tissue water relations were characterized before the drought, and the functional responses (water availability, gas exchange and fluorescence) were monitored during the drought. Both genera exhibited contrasting leaf structure and tissue water relations traits, with higher leaf area and specific leaf area as well as higher osmotic potential at maximum turgor and turgor loss point in Cistus than Ceanothus. During drought, Ceanothus showed a more conservative use of water than Cistus, with a water potential less sensitive to decreasing soil moisture and a strong decline in photosynthesis and stomatal conductance in response to water deficit, but also a level of fluorescence more responsive to drought than Cistus. However, we could not find a different degree of drought resistance between the genera. This was particularly clear between Cistus ladanifer L. and Ceanothus pauciflorus DC., the two most functionally contrasting species, but at the same time, the two most drought-resistant. Our findings demonstrate that species with different leaf traits and functional responses to water stress may not differ in their degree of drought resistance, at least during the seedling stage. This underlines the need to take general categorizations by genus or functional types with caution and to deepen our knowledge about the Mediterranean-type species ecophysiology, especially during early life stages, in order to anticipate their vulnerability to climate change.