The global spectrum of plant form and function

Application of ATR-Fourier transform infrared spectroscopy in fast and simultaneous determination of leaf chemical and functional properties of forest herb species

ATR-Fourier transform infrared spectroscopy was used to determine the carbon and nitrogen content in the leaves of herbaceous forest plant species and functional traits associated with the leaf economic spectrum (one of the two-dimensional global spectrum of plant form and function), and monitoring plant physiological status under elevated temperature conditions. The content of carbon and nitrogen determined by traditional methods validated the accuracy of ATR-FTIR method. It was also shown that in the case of forest herbs, the ATR-FTIR method is an efficient tool for determining functional traits (such as specific leaf area (SLA) and leaf dry matter content (LDMC)) related to the leaf economics spectrum, and to diagnose the photophysiological state of plants after changes of temperature (changes of day/night temperature from 21/13 °C to 25/17 °C). Measuring the areas of three absorption bands of the ATR-FTIR spectra related to amides I and II (between 1700 cm-1 and 1500 cm-1), carbohydrates (cellulose and hemicellulose; between 1200 cm-1 - 850 cm-1) and amide III (between 1290 cm-1 and 1190 cm-1) allowed for determination of all analysed chemical and functional properties of leaves. Based on selected absorption bands accurately estimated C and N content, with coefficients of correlation (r) of 0.88 for C and 0.84 for N. SLA and LDMC were also predicted, with r values of 0.88 and -0.91, respectively. Moreover, ATR-FTIR proved to be a rapid, non-destructive tool for monitoring the plant physiological status, as demonstrated by the significant correlation (r = 0.99) between the chlorophyll fluorescence performance index (PI) and ATR-FTIR data. ATR-FTIR has been demonstrated as an efficient tool for simultaneous quantification of leaf carbon and nitrogen content, economic functional traits, and physiological status of forest herb plants.

Worldwide comparison of carbon stocks and fluxes between native and non-native forests

Climate change is one of the main challenges that human societies are currently facing. Given that forests represent major natural carbon sinks in terrestrial ecosystems, administrations worldwide are launching broad-scale programs to promote forests, including stands of non-native trees. Yet, non-native trees may have profound impacts on the functions and services of forest ecosystems, including the carbon cycle, as they may differ widely from native trees in structural and functional characteristics. Also, the allocation of carbon between above- and belowground compartments may vary between native and non-native forests and affect the vulnerability of the carbon stocks to disturbances. We conducted a global meta-analysis to compare carbon stocks and fluxes among co-occurring forests dominated by native and non-native trees, while accounting for the effects of climate, tree life stage, and stand type. We compiled 1678 case studies from 250 papers, with quantitative data for carbon cycle-related variables from co-occurring forests dominated by native and non-native trees. We included 170 non-native species from 42 families, spanning 55 countries from all continents except Antarctica. Non-native forests showed higher overall carbon stock due to higher aboveground tree biomass. However, the belowground carbon stock, particularly soil organic carbon, was greater in forests dominated by native trees. Among fluxes, carbon uptake rate was higher in non-native forests, while carbon loss rate and carbon lability did not differ between native and non-native forests. Differences in carbon stocks and fluxes between native and non-native trees were greater at early life stages (i.e. seedling and juvenile). Overall, non-native forests had greater carbon stocks and fluxes than native forests when both were natural/naturalised or planted; however, native natural forests had greater values for the carbon cycle-related variables than plantations of non-native trees. Our findings indicate that promoting non-native forests may increase carbon stocks in the aboveground compartment at the expense of belowground carbon stocks. This may have far-reaching implications on the durability and vulnerability of carbon to disturbances. Forestry policies aimed at improving long-term carbon sequestration and storage should conserve and promote native forests.

Multi-response phylogenetic mixed models: concepts and application

The scale and resolution of trait databases and molecular phylogenies is increasing rapidly. These resources permit many open questions in comparative biology to be addressed with the right statistical tools. Multi-response (MR) phylogenetic mixed models (PMMs) offer great potential for multivariate analyses of trait evolution. While flexible and powerful, these methods are not often employed by researchers in ecology and evolution, reflecting a specialised and technical literature that creates barriers to usage for many biologists. Here we present a practical and accessible guide to MR-PMMs. We begin with a review of single-response (SR) PMMs to introduce key concepts and outline the limitations of this approach for characterising patterns of trait coevolution. We emphasise MR-PMMs as a preferable approach for analyses involving multiple species traits, due to the explicit decomposition of trait covariances. We discuss multilevel models, multivariate models of evolution, and extensions to non-Gaussian response traits. We highlight techniques for causal inference using graphical models, as well as advanced topics including prior specification and latent factor models. Using simulated data and visual examples, we discuss interpretation, prediction, and model validation. We implement many of the techniques discussed in example analyses of plant functional traits to demonstrate the general utility of MR-PMMs in handling complex real-world data sets. Finally, we discuss the emerging synthesis of comparative techniques made possible by MR-PMMs, highlight strengths and weaknesses, and offer practical recommendations to analysts. To complement this material, we provide online tutorials including side-by-side model implementations in two popular R packages, MCMCglmm and brms.

Effect of climate on traits of dominant and rare tree species in the world's forests

Species' traits and environmental conditions determine the abundance of tree species across the globe. The extent to which traits of dominant and rare tree species differ remains untested across a broad environmental range, limiting our understanding of how species traits and the environment shape forest functional composition. We use a global dataset of tree composition of >22,000 forest plots and 11 traits of 1663 tree species to ask how locally dominant and rare species differ in their trait values, and how these differences are driven by climatic gradients in temperature and water availability in forest biomes across the globe. We find three consistent trait differences between locally dominant and rare species across all biomes; dominant species are taller, have softer wood and higher loading on the multivariate stem strategy axis (related to narrow tracheids and thick bark). The difference between traits of dominant and rare species is more strongly driven by temperature compared to water availability, as temperature might affect a larger number of traits. Therefore, climate change driven global temperature rise may have a strong effect on trait differences between dominant and rare tree species and may lead to changes in species abundances and therefore strong community reassembly.

Functional trait response to aridity based on leaf trait network analysis in the Hexi Corridor, China

BACKGROUND

Aridity acts as a strong environmental filter for plants and is predicted to intensify in the future, resulting in changes to leaf functional traits. However, few studies explore how interactions of multiple traits result in leaf trait tradeoff strategies along an aridity gradient, and whether trait separation occurs with increasing aridity intensity. This study examines the impact of long-term aridity on 14 plant leaf traits in two arid areas (arid and hyper-arid) in the Hexi Corridor, China. A leaf trait network (LTN) was constructed to study how leaf trait tradeoff strategies differ between the two areas. Structural equation modeling (SEM) was used to identify the direct and indirect effects of aridity and functional diversity (as measured by community weighted means and functional dispersion) on leaf nutrient concentration.

RESULTS

LTN shows trait separation, poor synergy among traits, and low resource utilization. Correlation analyses showed that the mass ratio hypothesis is dominant, and aridity is positively correlated with leaf relative water content (RWC) and leaf phosphorus content, and negatively correlated with leaf nitrogen content (LNC). SEM results indicated that LNC is directly affected by aridity, RWC, leaf carbon content, and plant height. Aridity and functional dispersion directly affects leaf phosphorus content.

CONCLUSIONS

Results indicate that increasing drought weakens plant coordination among specific traits, and the main change in plant trait tradeoff strategies is reflected in the separation of nutrient traits. Exploring the change of the tradeoff among traits along the aridity gradient can better understand the adaptation process of plants to aridity and the process of community function change.

Functional traits explain growth response to successive hotter droughts across a wide set of common and future tree species in Europe

In many regions worldwide, forests increasingly suffer from droughts. The 'hotter drought' in Europe in 2018, and the consecutive drought years 2019 and 2020 caused large-scale growth declines and forest dieback. We investigated whether tree growth responses to the 2018-2020 drought can be explained by tree functional traits related to drought tolerance, growth and resource acquisition. We assessed the growth response, that is, growth during drought compared to pre-drought conditions of 71 planted tree species, using branch shoot increments. We used gap-filled trait data related to drought tolerance (P50, stomatal density, conductivity), resource acquisition (SLA, LNC, C:N, Amax) and wood density from the TRY database to explain growth responses, while accounting for differences in growth programmes (spring vs. full-season growing species). We found significantly reduced growth during the 2018 drought across all species. Legacy effects further reduced growth in 2019 and 2020. Gymnosperms showed decreasing growth with increasing P50 and acquisitiveness, such as high SLA, LNC, and Amax. Similar results were found for angiosperms, however, with a less clear pattern. Four distinct response types emerged: 'Sufferer', 'Late sufferer', 'Recoverer' and 'Resister', with gymnosperms predominately appearing as 'Sufferer' and 'Late sufferer'. 'Late sufferers' tended to be spring growing species. This study provides evidence for significant growth reductions and legacy effects in response to consecutive hotter droughts, which can be explained by functional traits across a wide range of tree species when accounting for fundamental growth programmes. We conclude that high drought tolerance bolsters growth reductions, while acquisitive species suffer more from drought.

Trait coordination and trade-offs constrain the diversity of water use strategies in Mediterranean woody plants

The diversity of water-use strategies among dryland plants has been the focus of extensive research, but important knowledge gaps remain. Comprehensive surveys of water-use traits encompassing multiple species growing at contrasting sites are needed to further advance current understanding of plant water use in drylands. Here we show that ecohydrological niche segregation driven by differences in water uptake depth among coexisting species is widespread across Mediterranean plant communities, as evidenced by soil and stem water isotopes measured in 62 native species growing at 10 sites with contrasting climatic conditions. Foliar carbon and oxygen isotopes revealed that leaf-level stomatal regulation stringency and water-use efficiency also differ markedly among coexisting species, and are both coordinated with water uptake depth. Larger and taller woody species use a greater proportion of deeper soil water, display more conservative water use traits at leaf level ("water-savers") and show greater investment in foliage relative to shoots. Conversely, smaller species rely mainly on shallow soil water, exhibit a more profligate water use strategy ("water-spenders") and prioritize investment in shoots over foliage. Drought stress favours coordination between above and belowground water-use traits, resulting in unavoidable trade-offs that constrain the diversity of whole-plant water use strategies in Mediterranean plant communities.

Roots of domestication: unveiling the dynamics of domestication through trait-based analysis of olive trees in northern Morocco

The domestication of crops, a transformative milestone in human history, has largely contributed to reshaping agricultural practices and plant characteristics. This study investigates the functional responses along the wild-cultivated continuum in olive trees in northern Morocco, focusing on leaf functional traits to elucidate domestication effects. We compared wild olive (Olea europaea subsp. europaea var. sylvestris) with traditional cultivated varieties (O. e. subsp. e. var. europaea). Our results reveal clear distinctions in leaf traits, including leaf area, specific leaf area and leaf dry matter content, indicating divergent resource-use strategies. Cultivated varieties displayed traits associated with thicker, denser leaves and higher stomatal density, suggesting adaptations to stress conditions such as water scarcity. Principal component analysis highlighted a leaf economic spectrum, which differentiated wild and cultivated forms and supported the functional trade-off between resource acquisition and conservation. Intraspecific trait variability was substantial, driven by both genetic factors and phenotypic plasticity in response to local environmental gradients. These findings underscore the significant impact of domestication on olive trees, providing insights into the adaptive mechanisms underlying crop resilience in traditional agroecosystems. Our research emphasizes the importance of conserving these traditional olive varieties, not only for their historical and cultural significance but also for the deep understanding they offer regarding the evolving relationship between humans and the plant world.This article is part of the theme issue 'Unravelling domestication: multi-disciplinary perspectives on human and non-human relationships in the past, present and future'.

Planting Genomes in the Wild: Arabidopsis from Genetics History to the Ecology and Evolutionary Genomics Era

The genetics model system Arabidopsis thaliana (L.) Heynh. lives across a vast geographic range with contrasting climates, in response to which it has evolved diverse life histories and phenotypic adaptations. In the last decade, the cataloging of worldwide populations, DNA sequencing of whole genomes, and conducting of outdoor field experiments have transformed it into a powerful evolutionary ecology system to understand the genomic basis of adaptation. Here, we summarize new insights on Arabidopsis following the coordinated efforts of the 1001 Genomes Project, the latest reconstruction of biogeographic and demographic history, and the systematic genomic mapping of trait natural variation through 15 years of genome-wide association studies. We then put this in the context of local adaptation across climates by summarizing insights from 73 Arabidopsis outdoor common garden experiments conducted to date. We conclude by highlighting how molecular and genomic knowledge of adaptation can help us to understand species' (mal)adaptation under ongoing climate change.

Genetically based trait coordination and phenotypic plasticity of growth, gas exchange, allometry, and hydraulics across the distribution range of Pinus pinaster

Studying intraspecific trait variation across environments is key for understanding how resource-use strategies evolve. It is hypothesized that plants from mesic environments have evolved toward a more acquisitive strategy with high growth potential and phenotypic plasticity, while populations from xeric continental climates exhibit a conservative strategy with slower growth and better physiological performance under drier conditions. We tested this hypothesis through the phenotypical characterization of 14-yr-old Pinus pinaster Aiton trees from 20 range-wide populations growing in two climatically contrasting common gardens. We measured 20 traits related to growth, leaf morphology, gas exchange, photochemistry, and hydraulics. Consistent with our hypothesis, we found that populations from mesic oceanic areas exhibited higher growth rates and higher allocation to leaf surface area under mesic conditions, along with greater plasticity in these traits. By contrast, xeric continental populations had better physiological status, showing higher gas exchange rates and photochemical efficiency, but lower sapwood-specific hydraulic conductivity under drier conditions. Together, our results provide evidence that climate drives the joint evolution of leaf and stem traits and their plasticity following an acquisitive-conservative axis of resource use. Overall, trait coordination is found to be highly plastic, likely to maximize plant performance under contrasting environmental conditions.

Functional Traits From Imaging Spectroscopy Inform Patterns of Forest Mortality During Sierra Nevada Drought

California's 2012-2016 megadrought led to the mortality of over 100 million trees. In the context of extreme drought and insect outbreaks, a holistic view of plant functional traits can provide further insight into underlying physiological and abiotic drivers of the patterns of mortality. We used new maps of early-drought (pre-mortality) foliar functional traits derived from the NASA AVIRIS-Classic imaging spectrometer, along with open-access climate, topography, canopy structure, and mortality data, to assess competing influences on drought mortality at the Soaproot Saddle and Lower Teakettle NEON sites in the southern Sierra Nevada Mountains. We aimed to (1) compare mortality trends across two independently derived mortality datasets, (2) assess trait-mortality relationships across diverse sites and species, and (3) link these relationships to mechanisms of tree-level drought response. We used random forests to assess the relative importance of mortality drivers and the trends of mortality across each predictor gradient. For the lower elevation, more water-limited Soaproot Saddle site, conifer mortality was linked to taller, drier canopies while broadleaf mortality was linked to foliar traits (lower cellulose, higher sugars, and higher leaf mass per area). For the higher elevation, more energy-limited Lower Teakettle site, mortality was more strongly linked to elevation and climate, with little influence from foliar traits.

Canopy functional trait variation across Earth's tropical forests

Tropical forest canopies are the biosphere's most concentrated atmospheric interface for carbon, water and energy1,2. However, in most Earth System Models, the diverse and heterogeneous tropical forest biome is represented as a largely uniform ecosystem with either a singular or a small number of fixed canopy ecophysiological properties3. This situation arises, in part, from a lack of understanding about how and why the functional properties of tropical forest canopies vary geographically4. Here, by combining field-collected data from more than 1,800 vegetation plots and tree traits with satellite remote-sensing, terrain, climate and soil data, we predict variation across 13 morphological, structural and chemical functional traits of trees, and use this to compute and map the functional diversity of tropical forests. Our findings reveal that the tropical Americas, Africa and Asia tend to occupy different portions of the total functional trait space available across tropical forests. Tropical American forests are predicted to have 40% greater functional richness than tropical African and Asian forests. Meanwhile, African forests have the highest functional divergence-32% and 7% higher than that of tropical American and Asian forests, respectively. An uncertainty analysis highlights priority regions for further data collection, which would refine and improve these maps. Our predictions represent a ground-based and remotely enabled global analysis of how and why the functional traits of tropical forest canopies vary across space.

Ecosystem multifunctionality in temperate forests of South Korea is primarily controlled by structural diversity and potential moisture availability with synergy effects between ecosystem functions

Assessing and improving ecosystem multifunctionality (EMF) is essential to achieving the goals of enhancing human well-being and sustainable development. This study aims to quantify EMF and to identify its influencing factors, including biotic (tree species diversity, functional dominance, and stand structural diversity) and abiotic factors (topography, climate, and soil), and stand age. We used South Korea's 7th National Forest Inventory data to analyze 630 natural forest plots consisting of coniferous, broadleaved, and mixed stands. We categorized 12 ecosystem function-related variables to quantify EMF. Multimodel averaging and piecewise structural equation modeling were implemented to identify the main variables that affect EMF and to quantify their interrelationships and strengths. Additionally, we quantified the strength of interactions between ecosystem functions. Our findings indicate that high plant richness and old forests led to high stand structural diversity, which has a direct positive effect on EMF. Additionally, reducing water stress increased the availability of plant resources, which also has a positive effect on EMF. The mechanism controlling EMF differed according to forest stand type. In particular, we did not observe dominant plant functional traits controlling EMF in mixed stands due to the mixture of functional traits of coniferous and broadleaved trees. Finally, the interactions among ecosystem functions demonstrated a stronger synergy effect, with most functions contributing to an increase in EMF, though the degree of impact varied depending on the forest stand type. Our analysis indicates that we must comprehensively consider biodiversity and stand age as well as stand structural diversity to promote EMF. Moreover, forest management strategies should account for the interaction between plant functional traits and ecosystem functions along with environmental gradients is essential.

Nonnative tree invaders lead to declines in native tree species richness

Biological invasions are profoundly altering Earth's ecosystems, but generalities about the effects of nonnative species on the diversity and productivity of native communities have been elusive. This lack of generality may reflect the limited spatial and temporal extents of most previous studies. Using >5 million tree measurements across eastern US forests from 1995 to 2023, we quantified temporal trends in tree diversity and biomass. We then analyzed community-level changes in native tree diversity and biomass in relation to nonnative tree invasion and native species colonization. Across the entire eastern United States, native tree species richness decreased over time in plots where nonnatives occurred, whereas nonnative species richness and the biomass of both natives and nonnatives increased over time. At the community scale, native richness tended to decline following nonnative invasion, whereas native biomass and richness-independent measures of trait and phylogenetic diversity tended to remain stable. These patterns can be explained by the rarity of the displaced native species and their functional and phylogenetic similarity to native species that survived nonnative invasions. In contrast, native survivors tended to be functionally distinct from nonnative invaders, suggesting an important role for niche partitioning in community dynamics. Colonization by previously absent native species was associated with an increase in native richness (beyond the addition of native colonizers), which contrasts with declines in native richness that tended to follow nonnative invasion. These results suggest a causal role for nonnative species in the native richness decline of invaded communities.

Decomposing leaf mass into metabolic and structural components explains divergent patterns of trait variation within and among plant species

Across the global flora, interspecific variation in photosynthetic and metabolic rates depends more strongly on leaf area than leaf mass. In contrast, intraspecific variation in these rates is strongly mass-dependent. These contrasting patterns suggest that the causes of variation in leaf mass per area (LMA) may be fundamentally different within vs. among species. In order to explain these contrasting patterns, we developed a statistical modeling framework to decompose LMA into two components-metabolic LMAm (which determines photosynthetic capacity and dark respiration) and structural LMAs (which determines leaf toughness and potential leaf lifespan)-using leaf trait data from tropical forests in Panama and a global leaf-trait database. Decomposing LMA into LMAm and LMAs improves predictions of leaf trait variation (photosynthesis, respiration, and lifespan) within and among species. We show that strong area-dependence of metabolic traits across species can result from multiple factors, including high LMAs variance and/or a slow increase in photosynthetic capacity with increasing LMAm. In contrast, strong mass-dependence of metabolic traits within species results from LMAm increasing from shady to sunny conditions. LMAm and LMAs were nearly independent of each other in both global and Panama datasets, suggesting the presence of at least two important dimensions of leaf functional variation.

Cones and consequences: the false dichotomy of conifers vs broad-leaves has critical implications for research and modelling

In plant science research and modelling, particularly from the northern hemisphere, the terms 'needle-leaved' and 'conifer' along with 'broad-leaved' and 'angiosperm' are often used synonymously, creating the false dichotomy that conifers are needle-leaved and angiosperms are broad-leaved. While these equivalences may be largely correct in the temperate northern hemisphere, they do not hold true in equatorial and southern hemisphere forests. Confounding needle-leaved conifers and broad-leaved angiosperms present significant issues in empirical research and modelling. Here, we highlight the likely origins and impacts of misusing conifer-related terminology, the misinterpretation that ensues and its implications. We identify the issue of a focus on Pinaceae and coin the term 'Pinaceae panacea' to describe this. We provide recommendations for future research: from standardising the use of definitions to shifting away from using Pinaceae as a model group for all conifers.

Different responses of canopy and shrub leaves to canopy nitrogen and water addition in warm temperate forest

Introduction

Understanding the effects of nitrogen deposition and increased rainfall on plants is critical for maintaining forest ecosystem services. Although previous studies primarily examined the effects of environmental changes on leaf functional traits, the underlying physiological and metabolic processes associated with these traits remain poorly understood and warrant further investigation.

Methods

To address this knowledge gap, we evaluated the influence of canopy nitrogen (25 kg ha-1 yr-1) and water (30% of the local precipitation) addition on leaf functional traits, diversity, and associated physiological and metabolic processes in the dominant species of tree and shrub layers.

Results

Only the interaction between nitrogen and water significantly reduced the functional richness (FRic) of the community. The other treatments had no notable effects on functional diversity. Importantly, the physiological processes of trees and shrubs showed different regulatory strategies. In addition, there were significant changes in 29 metabolic pathways of the tree, whereas only 18 metabolic pathways were significantly altered in shrub. Among the identified metabolic pathways, four were annotated multiple times, with amino acid metabolism being the most active.

Discussion

These regulatory processes enable the leaves to withstand external disturbances and maintain their relative stability under changing environmental conditions. The study findings underscore the limitations of previous research, which often relied on the direct application of treatments to the understory and so failed to accurately assess the effects of nitrogen and water on leaf functional traits. Future studies should adopt canopy-level nitrogen and water addition to better simulate the impacts of global environmental change.

Leaf trait divergence between Azadirachta indica (exotic) and native species of the northern Brazilian coast

The introduction of exotic plants can pose ecological threats as they may become invasive. We investigated leaf traits potentially linked to competitive advantage and invasiveness in Azadirachta indica, a widely used exotic tree in northeastern Brazil's urban forestry, compared to native species Ouratea fieldingiana and Myrcia multiflora. We tested the limiting similarity hypothesis, evaluating how leaf characteristics influence the ecological responses of these species and A. indica's potential invasiveness. A. indica exhibited larger leaf area, specific leaf area (SLA), and leaf area ratio (LAR) compared to native species, but lower specific petiole length (SPL) and specific internode length (SIL). Additionally, A. indica displayed greater phenotypic variation in these traits. The larger leaf area, SLA, and LAR suggest a strategy in A. indica favoring rapid carbon gain through increased growth. The higher phenotypic variation observed may facilitate adaptation to new habitats, potentially enhancing its competitive ability and invasiveness. These findings highlight distinct functional strategies between exotic and native species, raising concerns regarding the potential invasiveness of A. indica in northeastern Brazil's natural ecosystems.

Network-informed analysis of a multivariate trait-space reveals optimal trait selection

Trait-based analyses have shown great potential to advance our understanding of terrestrial ecosystem processes and functions. However, challenges remain in adequately synthesising a multidimensional and covarying trait space. Reducing the number of studied traits while identifying the most informative ones is increasingly recognized as a priority in functional ecology. Here, we develop a trait reduction procedure based on network analysis of a global dataset comprising 27 traits in three steps. We first construct all possible reduced networks and identify optimal reduced networks that capture the structure of the full 27-trait network. Then we apply the constraints on trait consistency to identified optimal reduced networks and establish consistent network series across ecoregions. We find the best performing networks that capture the three main dimensions of the full network (hydrological safety, leaf economic strategy, and plant reproduction and competition) and the global variance of network metrics. Finally, we find a parsimonious representation of trait covariation strategies is achieved by a 10-trait network which preserves 60% of all the original information while costing only 20.1% of the full suite of traits. Our results show the network reduction approach can improve our understanding on the main plant strategies and facilitate the future trait-based research.

Transcriptomic Temperature Stress Responses Show Differentiation Between Biomes for Diverse Plants

Plants are foundational to terrestrial ecosystems, and because they are sessile, they are particularly reliant on physiological plasticity to respond to weather extremes. However, variation in conserved transcriptomic responses to temperature extremes is not well described across plants from contrasting environments. Beyond molecular responses, photosystem II thermal tolerance traits are widely used to assay plant thermal tolerance. To explore options for improving the prediction of thermal tolerance capacity, we investigated variation in the transcriptomic stress responses of 20 native Australian plant species from varied environments, using de novo transcriptome assemblies and 188 RNA-sequencing libraries. We documented gene expression responses for biological processes, to both hot and cold temperature treatments, that were consistent with conserved transcriptomic stress responses seen in model species. The pathways with the most significant responses were generally related to signaling and stress responses. The magnitude of some responses showed differentiation between the species from contrasting arid, alpine, and temperate biomes. This variation among biomes indicated that postheat exposure, alpine and temperate species had greater shifts in expression than arid species and alpine species had weaker responses to the cold treatment. Changes in the median expression of biological processes were also compared to plasticity in photosystem II heat and cold tolerance traits. Gene expression responses showed some expected relationships with photosystem II thermal tolerance plasticity, but these two response types appeared to be mostly independent. Our findings demonstrate the potential for using variation in conserved transcriptomic traits to characterize the sensitivity of plants from diverse taxa to temperature extremes.

Plant Acquisitive Strategies Promote Resistance and Temporal Stability of Semiarid Grasslands

Among ecologists, it is widely believed that conservative growth strategies of plants are crucial for sustaining ecosystem stability, while the potential stabilising role of acquisitive strategies has received little attention. We investigated the relationships between plant traits and three stability dimensions-temporal stability, resistance and resilience-using two complementary datasets from drought-affected semi-arid grasslands: a temporal plant community survey from a single site and a 1000-km transect survey with satellite-derived productivity estimates. We found strikingly consistent patterns from the two datasets, with grasslands dominated by acquisitive strategies exhibiting greater resistance and temporal stability of productivity. Acquisitive strategies enhance stability by facilitating drought escape and avoidance, rather than drought tolerance typically associated with conservative strategies. These results highlight the important but underappreciated role of acquisitive strategies in enhancing ecosystem resistance to disturbances and maintaining temporal stability in semi-arid grasslands.

Combined addition of γ-PGA and DCD facilitates phytoremediation of heavy metals and carbon sequestration: A field experiment

A field study examined the impact of γ-polyglutamic acid (γ-PGA), both alone and in combination with dicyandiamide (DCD), on the phytoremediation of soil contaminated with Cd, Pb, and Zn. This study focused on the heavy metal (HM) accumulation, and soil CO2 and N2O emissions in Cosmos sulphureus and Pennisetum americanum × P. purpureum, and soil microbial communities. The findings indicated that the application of γ-PGA, either alone or in combination with DCD, increased plant yield and HM bioavailability in the soil, leading to improved HM uptake by plants. For P. americanum × P. purpureum, compared to CK treatment, the combined addition of γ-PGA and DCD increased the Cd, Pb, and Zn extraction by 131.4%, 80.6%, and 99.7%, respectively. Compared to γ-PGA alone, the combined addition of γ-PGA and DCD reduced the soil N2O emission and global warming potential by 26.4% and 39.1%, respectively. P. americanum × P. purpureum treated with γ-PGA and DCD achieved C sequestration of 829 kg ha-1. Moreover, the application of γ-PGA, alone or in combination with DCD, increased the abundance of soil microbes. Bacteria (Proteobacteria, Actinobacteriota, and Firmicutes) as well as fungi (Basidiomycota and Mortierellomycota) contributed to HM accumulation and resistance to stress by altering soil enzyme activities, C and N fractions. Additionally, Acidobacteriota and Patescibacteria are beneficial to reducing soil GHG emissions and GWP in P. americanum × P. purpureum soil treated with γ-PGA and DCD. In conclusion, P. americanum × P. purpureum with the combined addition of γ-PGA and DCD increased HM extraction and total C sequestration in the plant-soil system. This approach offers a scientific basis and promising approach for integrating phytoremediation with C sequestration.

Widespread slow growth of acquisitive tree species

Trees are an important carbon sink as they accumulate biomass through photosynthesis1. Identifying tree species that grow fast is therefore commonly considered to be essential for effective climate change mitigation through forest planting. Although species characteristics are key information for plantation design and forest management, field studies often fail to detect clear relationships between species functional traits and tree growth2. Here, by consolidating four independent datasets and classifying the acquisitive and conservative species based on their functional trait values, we show that acquisitive tree species, which are supposedly fast-growing species, generally grow slowly in field conditions. This discrepancy between the current paradigm and field observations is explained by the interactions with environmental conditions that influence growth. Acquisitive species require moist mild climates and fertile soils, conditions that are generally not met in the field. By contrast, conservative species, which are supposedly slow-growing species, show generally higher realized growth due to their ability to tolerate unfavourable environmental conditions. In general, conservative tree species grow more steadily than acquisitive tree species in non-tropical forests. We recommend planting acquisitive tree species in areas where they can realize their fast-growing potential. In other regions, where environmental stress is higher, conservative tree species have a larger potential to fix carbon in their biomass.

Plant size influences specific leaf area in palms: a case for the diminishing returns hypothesis

Body size is essential in determining an organism's functional performance and metabolic requirements, influencing biological processes from organisms to ecosystems. Metabolic scaling theory integrates the size-metabolism relationship, yet most research overlooks intraspecific trait variation due to ontogeny. Specific leaf area (SLA) is a critical functional trait that reflects investment on photosynthetic tissues relative to leaf construction costs. SLA influences photosynthetic capacity and growth rates and varies across life stages. While plants exhibit interspecific differences in acquisitive (high SLA, fast growth) and conservative (low SLA, slow growth) strategies, the diminishing returns hypothesis suggests that these strategies are shaped by the proportion of supporting structures that develop over the plant´s lifespan (intraspecific variation), predicting a negative SLA relationship with increasing size. In tropical environments, palms are ecologically important yet still understudied in functional traits. Here, we examine the relationship between SLA and size in six neotropical understory and canopy palm species (236 individuals). Results showed higher SLA in understory species and a negative SLA-size relationship across most species. SLA inversely correlated with leaf thickness and leaf water content. ANCOVA models explained substantial SLA variation related to palm size, with species-specific differences in regression slopes. These findings underscore the importance of considering inter- and intraspecific SLA variation and ontogenetic changes. Understanding the trade-off between acquisitive and conservative strategies within the context of the diminishing returns hypothesis offers insights into plant growth strategies and their ecological implications, which is essential for predicting plant adaptation to environmental gradients.

Ecophysical constraints on avian adaptation and diversification

The evolution of morphological diversity is ultimately governed by physical laws and ecological contexts, which together impose a range of ecophysical constraints. Substantial progress has been made in identifying how these constraints shape the form and function of producers (plants), but similar knowledge is lacking for consumers, in part because the requisite data have not been available at sufficient scale for animals. Using morphometric measurements for all birds, we demonstrate that observed variation is restricted-both for beak shape and body shape-to triangular regions of morphospace with clearly defined boundaries and vertices (corners). By combining morphometric data with information on ecological and behavioral functions, we provide evidence that the extent of avian morphospace reflects a trade-off between three fundamental physical tasks for feeding (crush, engulf, and reach) that characterize resource acquisition and processing by the beak and three physical tasks (fly, swim, and walk) that characterize avian lifestyles or locomotion. Phylogenetic analyses suggest that trajectories of morphological evolution trend toward the vertices, with lineages evolving from a core of functional generalists toward more specialized physical tasks. We further propose that expansion beyond the current boundaries of morphospace is constrained by the shorter evolutionary lifespan of functional specialists, although patterns of speciation rate and current extinction risk provide only weak support for this hypothesis. Overall, we show that the structure of avian morphospace follows relatively simple rules defined by ecophysical constraints and trade-offs, shedding light on the processes shaping modern animal diversity and responses to environmental change.

Effects of warming and nitrogen deposition on species and functional diversity of plant communities in the alpine meadow of Qinghai-Tibet Plateau

Plant species and functional diversity play an important role in the stability and sustainability of grassland ecosystems. However, the changes and mechanisms of plant species and functional diversity under warming and nitrogen deposition are still unclear. In this study, we investigated the plant and soil characteristics of alpine meadows on the Qinghai-Tibet Plateau to explore the changes in species and functional diversity of plant communities under warming and nitrogen deposition, as well as their interrelationships and key determinants. The results showed that warming, nitrogen deposition, and their interactions had significant effects on plant species diversity (plant Shannon-Wiener index) and functional diversity (functional richness index, functional differentiation index, functional dispersion, and Rao's quadratic entropy index). With the increase of warming and nitrogen deposition, the Shannon-Wiener index of plants increased first and then decreased. The plant functional richness index, functional diversity index, functional dispersion index, and Rao's quadratic entropy index showed a decreasing trend. At the same time, with the increase in temperature and nitrogen deposition, the relationship between plant species diversity index and functional diversity index in the alpine meadow of Qinghai-Tibet Plateau gradually weakened. Redundancy analysis and structural equation modeling showed that both warming and nitrogen deposition had significant negative effects on the plant species diversity index and plant functional diversity index. Plant factors (Grasses importance value, leaf nitrogen weighted mean, specific leaf area-weighted mean, leaf area-weighted mean, and leaf weight weighted mean) and soil environmental factors (soil total nitrogen and soil carbon-nitrogen ratio) directly or indirectly affect plant community diversity under warming and nitrogen deposition.

Temporal stability of forest productivity declines over stand age at multiple spatial scales

There is compelling experimental evidence and theoretical predictions that temporal stability of productivity, i.e., the summation of aboveground biomass growth of surviving and recruitment trees, increases with succession. However, the temporal change in productivity stability in natural forests, which may undergo functional diversity loss during canopy transition, remains unclear. Here, we use the forest inventory dataset across the eastern United States to explore how the temporal stability of forest productivity at multi-spatial scales changes with stand age during canopy transition. We find that productivity stability decreases with stand age at the local and metacommunity scales. Specifically, consistent declines in local diversity result in less asynchronous productivity dynamics among species over succession, consequently weakening local stability. Meanwhile, increasing mortality and the transition from conservative to acquisitive species with succession weaken species and local stability. Successional increases in species composition dissimilarity among local communities cause more asynchronous productivity dynamics among local communities. However, the decline in local stability surpasses the rise in asynchronous productivity dynamics among local communities, resulting in lower metacommunity stability in old forests. Our results suggest lower productivity stability in old-growth forests and highlight the urgency of protecting diversity at multiple spatial scales to maintain productivity stability.

Response of aboveground organs of Woody plants in the Qaidam Basin in China to aridity via functional economic spectra

BACKGROUND

Plant economic profiles involve trade-offs between many functional traits of a plant that are often used as indicators to characterize major adaptive strategies, thus providing insights into plant distribution, ecosystem processes, and function. However, research on plant economic profiles in extreme habitats is limited, and most studies on economic profiles have focused on single organs, with fewer studies on economic profiles among aboveground (leaf and stem) organs.

METHODS

Taking the desert area of Qaidam Basin as the research object, 8 leaf traits and 8 stem traits of 25 dominant woody plants accounting for more than 80% of biomass in 130 sample plots under different aridity gradients were quantitatively analyzed. The functional strategies and economic profiles of aboveground organs of desert plants adapted to arid environment were studied.

RESULTS

Traits of leaves and stems represent distinct resource strategies. Leaf traits emphasize resource acquisition, while stem traits highlight conservation. The leaf economic spectrum (LES) and stem economic spectrum (SES) strategies showed an inverse pattern, with leaf traits shifting from opportunistic to conservative strategies and stem traits shifting from conservative to stabilizing strategies as aridity intensified, revealing an integrated aboveground economic spectrum of the plant along the aridity gradient. Moreover, there was a significant negative correlation between leaf and stem function strategies and reflected significant leaf-stem trade-offs.

CONCLUSION

The functional traits of plants can reflect plant responses to environmental changes, and the aboveground economics spectrum helps researchers understand the response of plants as a whole to environmental differences, thus deepening the knowledge of the economic spectrum of plants. The patterns of economic profiles embodied by plants in response to aridity were revealed in this study. The trade-off between the LES and SES demonstrated the existence of an aboveground economic spectrum, providing a scientific basis for understanding the survival mode and adaptive variation pattern of desert plants.

Shaping beta diversity in arid landscape through native plant species contributions: synergy of climate, soil, and species traits

Understanding how species traits, climate aridity, and soil resources interact to influence beta diversity is critical for predicting changes in plant community composition. This study aims to investigate how these interactions shape species contributions to spatial turnover and beta diversity, focusing on the unique dryland ecosystems of the Saint Katherine Protectorate (SKP) in Egypt. To address this, we analyzed data from 84 vegetation plots, considering the direct and indirect effects of climatic aridity, soil resources, and species traits (e.g., plant height, leaf production, specific leaf area), as well as the relative abundance of C3 plants and phylogenetic diversity on species contribution to beta diversity (SCBDeff). Using Generalized Linear Models (GLMs) and Structural Equation Modelling (SEMs), the results revealed complex indirect effects of aridity and soil resources on SCBDeff mediated by plant traits. SCBDeff was positively influenced by climatic aridity, particularly in species with greater phylogenetic distance, taller plants, high leaf production, and a higher relative abundance of C3 plants. Conversely, specific leaf area (SLA) had a negative effect. Phylogenetic diversity emerged as a significant driver of beta diversity, with distantly related species contributing more due to functional differentiation and niche partitioning. The findings emphasize the critical role of species traits and environmental conditions in shaping beta diversity. These insights can inform conservation strategies aimed at enhancing ecosystem stability under shifting climatic conditions, particularly in dryland environments where species adaptive traits play a pivotal role.

Tropical forests in the Americas are changing too slowly to track climate change

Understanding the capacity of forests to adapt to climate change is of pivotal importance for conservation science, yet this is still widely unknown. This knowledge gap is particularly acute in high-biodiversity tropical forests. Here, we examined how tropical forests of the Americas have shifted community trait composition in recent decades as a response to changes in climate. Based on historical trait-climate relationships, we found that, overall, the studied functional traits show shifts of less than 8% of what would be expected given the observed changes in climate. However, the recruit assemblage shows shifts of 21% relative to climate change expectation. The most diverse forests on Earth are changing in functional trait composition but at a rate that is fundamentally insufficient to track climate change.

Comparison of seed traits between an invasive plant and its native competitor along a latitudinal gradient

Seeds are crucial for plant population maintenance and dispersal. Invasive species often exhibit seed traits that enhance their colonization success, such as increased dispersal potential, earlier germination, or greater resource reserves. However, few studies have compared seed traits between invasive and native plant species along environmental gradients. Here, we compared morphological traits and nutrient concentrations of the seeds of two competing species, the native common reed (Phragmites australis) and the invasive saltmarsh cordgrass (Spartina alterniflora), along a 20° latitudinal gradient of the Chinese coast, and their relationships with environmental factors. Significant differences were found between the two species for 11 of the 13 traits with respect to latitude. Specifically, the seed size of S. alterniflora decreased with increasing latitude, but P. australis showed a slight curvilinear relationship with latitude, reducing to a minimum between 30 and 35° N. The latitudinal variation in seed set showed the opposite trends in both species at high latitudes. Seed nitrogen concentration decreased with latitude in both species, while seed phosphorus concentration declined only in P. australis. We also identified that temperature-dependent climatic variables were more important than soil properties in affecting the latitudinal variations of seed traits for both species, especially for S. alterniflora. Based on the results, we predict that the greater fecundity of S. alterniflora populations poses an increasing threat to P. australis at the higher latitudes as temperature rises due to climate change.

Functional composition of the Amazonian tree flora and forests

Plants cope with the environment by displaying large phenotypic variation. Two spectra of global plant form and function have been identified: a size spectrum from small to tall species with increasing stem tissue density, leaf size, and seed mass; a leaf economics spectrum reflecting slow to fast returns on investments in leaf nutrients and carbon. When species assemble to communities it is assumed that these spectra are filtered by the environment to produce community level functional composition. It is unknown what are the main drivers for community functional composition in a large area such as Amazonia. We use 13 functional traits, including wood density, seed mass, leaf characteristics, breeding system, nectar production, fruit type, and root characteristics of 812 tree genera (5211 species), and find that they describe two main axes found at the global scale. At community level, the first axis captures not only the 'fast-slow spectrum', but also most size-related traits. Climate and disturbance explain a minor part of this variance compared to soil fertility. Forests on poor soils differ largely in terms of trait values from those on rich soils. Trait composition and soil fertility exert a strong influence on forest functioning: biomass and relative biomass production.

An integrated fast-slow plant and nematode economics spectrum predicts soil organic carbon dynamics during natural restoration

Aboveground and belowground attributes of terrestrial ecosystems interact to shape carbon (C) cycling. However, plants and soil organisms are usually studied separately, leading to a knowledge gap regarding their coordinated contributions to ecosystem C cycling. We explored whether integrated consideration of plant and nematode traits better explained soil organic C (SOC) dynamics than plant or nematode traits considered separately. Our study system was a space-for-time natural restoration chronosequence following agricultural abandonment in a subtropical region, with pioneer, early, mid and climax stages. We identified an integrated fast-slow trait spectrum encompassing plants and nematodes, demonstrating coordinated shifts from fast strategies in the pioneer stage to slow strategies in the climax stage, corresponding to enhanced SOC dynamics. Joint consideration of plant and nematode traits explained more variation in SOC than by either group alone. Structural equation modeling revealed that the integrated fast-slow trait spectrum influenced SOC through its regulation of microbial traits, including microbial C use efficiency and microbial biomass. Our findings confirm the pivotal role of plant-nematode trait coordination in modulating ecosystem C cycling and highlight the value of incorporating belowground traits into biogeochemical cycling under global change scenarios.

Ectomycorrhizal Dominance Increases Temporal Stability of Productivity at Multiple Spatial Scales Across US Forests

Mycorrhizas are fundamental to plant productivity and plant diversity maintenance, yet their influence on the temporal stability of forest productivity across scales remains uncertain. The multiscale stability theory clarifies that the temporal stability (γ stability) of metacommunity-several local communities connected through species dispersal-can be decomposed into the temporal stability of local communities (α stability) and asynchrony among them. Here, based on the forest inventory dataset from the United States and the multiscale stability theory, we explored how mycorrhizal strategy influences forest stability across scales and their underlying mechanisms. At the local scale, we found that α stability increased with ectomycorrhizal dominance due to the higher temporal stability of ectomycorrhizal trees. Additionally, higher α diversity associated with mixed mycorrhizal strategies promoted species asynchrony. At the metacommunity scale, the stabilizing effect of ectomycorrhizal dominance surpassed that of mixed mycorrhizal strategies on the asynchrony among local communities (i.e., spatial asynchrony), resulting in higher γ stability with increasing ectomycorrhizal dominance. Our research suggests the stabilizing effects of ectomycorrhizal dominance on the temporal stability of forest productivity, highlighting the importance of protecting ectomycorrhizal forests to maintain productivity under climate change, especially in the boreal-temperate ecotone where ectomycorrhizal trees are threatened by global change.

Traits estimated when grown alone may underestimate the competitive advantage and invasiveness of exotic species

Functional differences between native and exotic species, estimated when species are grown alone or in mixtures, are often used to predict the invasion risk of exotic species. However, it remains elusive whether the functional differences estimated by the two methods and their ability to predict species invasiveness (e.g. high abundance) are consistent. We compiled data from two common garden experiments, in which specific leaf area, height, and aboveground biomass of 64 common native and exotic invasive species in China were estimated when grown individually (pot) or in mixtures (field). Exotic species accumulated higher aboveground biomass than natives, but only when grown in field mixtures. Moreover, aboveground biomass and functional distinctiveness estimated in mixtures were more predictive of species persistence and relative abundance in the field mixtures in the second year than those estimated when grown alone. These findings suggest that assessing species traits while grown alone may underestimate the competitive advantage for some exotic species, highlighting the importance of trait-by-environment interactions in shaping species invasion. Therefore, we propose that integrating multi-site or multi-year field surveys and manipulative experiments is required to best identify the key trait(s) and environment(s) that interactively shape species invasion and community dynamics.

Quantifying disturbance effects on ecosystem services in a changing climate

Disturbances, such as hurricanes, fires, droughts and pest outbreaks, can cause major changes in ecosystem conditions that threaten Nature's contributions to people (ecosystem services). Climate change is intensifying disturbances, posing risks to ecosystem services. To assess those risks, we develop a flexible, functional trait-based approach to quantify ecological, ecosystem service and economic impacts from disturbance regimes. Our broadly applicable approach integrates knowledge from disturbance ecology and ecosystem service valuation, and we highlight the pitfalls of using either perspective in isolation. We demonstrate our approach by quantifying impacts to timber and recreational enjoyment from extreme windstorms in a midlatitude forest. While we predict large potential losses to these services under historical and future disturbance regimes, common ecological metrics of compositional and biomass stability are inadequate for predicting these impacts. We then provide a roadmap for applying our approach across different social-ecological systems, illustrating the approach for crop pollination, flood hazard mitigation and cultural values from coral reefs-which all face intensifying disturbances. This study highlights and provides tools to address the pressing need to consider disturbances in future ecosystem service assessments.

Convergent Strategies for Leaf Traits in Tree Species From Divergent Habitats

Plant trait expressions and their trade-offs reflect the responses and long-term ecological adaptation to environmental gradients. However, how such expressions and trade-offs help plants to acclimate to a new environment remains poorly understood, which is a fundamental preset for plants' survival under a global change scenario. By comparing the trait-trait relationships of 4403 tree species from different climatic regions and the variation in trait trade-offs of 746 tree species that have been transplanted to a tropical botanical garden for several decades, our results reveal convergent but consistent alteration in trait-trait relationships of trees transplanted from different climatic regions to a common environment. The convergent trends enhance the capability of tree species in buffering the impacts of climate change through allocating more resources to growth and tolerance. We propose that altered trait-trait relationships may be the key mechanisms that underlie the long-term ecological stability and resilience of tree species.

Tree growth is better explained by absorptive fine root traits than by transport fine root traits

Although the interest in root traits has increased in recent years, we still have limited knowledge of (i) whether functionally different fine roots-absorptive versus transport roots-have similar trait coordination and (ii) how they help to explain plant performance, such as growth. We measured traits of 25 European broadleaved tree species growing in a research arboretum to study (i) the coordination of root traits within absorptive and transport fine roots and (ii) the degree of trait-tree growth relationships. To do so, we combined a suite of morphological and anatomical traits for each of the absorptive and transport roots. Despite remarkable differences in average trait values between absorptive and transport roots, our study shows that trait coordination within absorptive and transport roots is relatively similar. Our results also show that, for the selected traits, tree growth is better explained by absorptive root traits than by transport root traits and is higher in species with thinner roots. The stronger relationship between absorptive roots and tree growth highlights that roots mostly involved with resource absorption are more important in explaining tree growth than transport roots, which are mainly responsible for resource transportation.

Seed functional ecology in Brazilian rock outcrop vegetation: an integrative synthesis

BACKGROUND AND AIMS

Rock outcrop vegetation is distributed worldwide and hosts a diverse and unique flora that evolved under harsh environmental conditions. Unfortunately, seed ecology in such ecosystems has received little attention, especially regarding seed traits, germination responses to abiotic factors and the potential role of phylogenetic relatedness in shaping such features. Here, we provide the first quantitative and phylogenetically informed synthesis of the seed functional ecology of Brazilian rock outcrop vegetation, with a particular focus on quartzitic and ironstone campo rupestre.

METHODS

Using a database of functional trait data, we calculated the phylogenetic signal for seven seed traits for 371 taxa and tested whether they varied among growth forms, geographic distribution and microhabitats. We also conducted meta-analyses that included 4252 germination records for 102 taxa to assess the effects of light, temperature and fire-related cues on the germination of campo rupestre species and explored how the aforementioned ecological groups and seed traits modulate germination responses.

KEY RESULTS

All traits and germination responses showed a moderate to strong phylogenetic signal. Campo rupestre species responded positively to light and had maximum germination between 20 and 25 °C. The effect of temperatures beyond this range was moderated by growth form, species geographic distribution and microhabitat. Seeds exposed to heat shocks above 80 °C lost viability, but smoke accelerated germination. We found a moderating effect of seed mass for responses to light and heat shocks, with larger, dormant seeds tolerating heat better but being less sensitive to light. Species from xeric habitats evolved phenological strategies to synchronize germination during periods of increased soil water availability.

CONCLUSIONS

Phylogenetic relatedness plays a major role in shaping the seed ecology of Brazilian rock outcrop vegetation. Nevertheless, seed traits and germination responses varied significantly between growth forms, species geographic distribution and microhabitats, providing support to the regeneration niche hypothesis and the role of functional traits in shaping germination in these ecosystems.

Hydraulic trait variation and relationships with the leaf economics spectrum in wine grapes

Understanding how functional traits and trait spectra vary and covary with one another is a primary goal in plant ecology, however, there remains debate surrounding whether functional trait spectra vary independently of one another. Relationships among trait spectra-referred to as "trait dimensionality"-have been tested in multiple studies, investigating the dimensionality among the most common trait spectra, such as those between the Leaf Economics Spectrum (LES) and other aspects of plant form and function. However, we know considerably less about plant hydraulic traits, and whether or not they form distinct axes of trait variation within plant species, and if a hydraulic trait dimensions covaries with, or is independent of, the LES. Using 12 varieties of grapevine (Vitis vinifera), we evaluated trait dimensionality among eight hydraulic traits derived from pressure-volume curves, to test if these traits form distinct a distinct trait axis, and if this axis covaries within an intraspecific LES in wine grapes. Our results indicate that wine grape cultivars and clones differ significantly in their hydraulic trait expression, with a single principal axis of variation explaining 58.3% of hydraulic trait variation in wine grapes. Along this axis, capacitance at full turgor (Cft) is especially important in defining hydraulic traits of wine grapes, with this trait trading off against the other hydraulic traits including turgor loss point, relative leaf water content at turgor loss point, modulus of elasticity, and the apoplastic water fraction. Multiple factor analysis further revealed orthogonal relationships between hydraulic traits and a LES in wine grapes, suggesting that these trait spectra vary independently of one another. Maintaining an understanding of hydraulic trait variation is increasingly important in economically significant crops such as V. vinifera, as drought becomes more prevalent, and our results here suggest that crop trait spectra represent independent axes of ecological variation among plants, varieties, and clones.

Elevational shifts in reproductive ecology indicate the climate response of a model chasmophyte, Rainer's bellflower (Campanula raineri)

BACKGROUND AND AIMS

Elevation gradients provide 'natural experiments' for investigating plant climate change responses, advantageous for the study of protected species and life forms for which transplantation experiments are illegal or unfeasible, such as chasmophytes with perennial rhizomes pervading rock fissures. Elevational climatic differences impact mountain plant reproductive traits (pollen and seed quality, sexual vs. vegetative investment) and pollinator community composition; we investigated the reproductive ecology of a model chasmophyte, Campanula raineri Perp. (Campanulaceae), throughout its current elevational/climatic range to understand where sub-optimal conditions jeopardise survival. We hypothesised that: 1) reproductive fitness measures are positively correlated with elevation, indicative of the relationship between fitness and climate; 2) C. raineri, like other campanulas, is pollinated mainly by Hymenoptera; 3) potential pollinators shift with elevation.

METHODS

We measured pollen and seed quality, seed production, the relative investment in sexual vs. vegetative structures and vegetative (Grime's CSR) strategies at different elevations. Potential pollinators were assessed by combining molecular and morphological identification.

KEY RESULTS

Whereas CSR strategies were not linked to elevation, pollen and seed quality were positively correlated, as was seed production per fruit (Hypothesis 1 is supported). The main pollinators of C. raineri were Apidae, Andrenidae, Halictidae (Hymenoptera) and Syrphidae (Diptera), probably complemented by a range of occasional pollinators and visitors (Hypothesis 2 partially supported). Potential pollinator communities showed a taxonomic shift towards Diptera with elevation (particularly Anthomyiidae and Muscidae) and away from Hymenoptera (Hypothesis 3 was supported).

CONCLUSIONS

Pollinator availability is maintained at all elevations by taxon replacement. However, reduced pollen quality and seed production at lower elevations suggest an impact of climate change on reproduction (especially <1200 m a.s.l., where seed germination was limited). Aside from guiding targeted conservation actions for C. raineri, our results highlight problems that may be common to mountain chasmophytes worldwide.

Nitrogen enrichment and vascular plant richness loss reduce bryophyte richness

Grasslands' high diversity is threatened by land-use changes, such as nitrogen fertilization, leading to productive but low-richness, fast-growing plant communities. Bryophytes are a key component of grassland diversity and react strongly to land use. However, it is unclear whether land-use effects are direct or mediated by changes in vascular plants. Increases in vascular plant cover are likely to decrease bryophyte abundance through light competition. Whether changes in vascular plant composition and richness also play a role remains unclear. We sampled bryophytes in a factorial grassland experiment manipulating nitrogen fertilization, fungicide, species richness, and functional composition of vascular plants crossed with moderate disturbances by weeding. Disturbance increased bryophyte richness and modulated treatment effects. In contrast to previous studies reporting indirect negative fertilization effects via increasing vascular plant productivity and reduced light levels, nitrogen fertilization directly reduced bryophyte cover and species richness, possibly because of toxic effects. Low vascular plant richness and dominance of fast-growing species reduced bryophyte richness. This might be because of decreased structural and resource niche heterogeneity in species-poor communities. Our results highlight novel mechanisms by which land-use intensification can affect bryophytes and suggest that a loss of vascular plant richness might have cascading effects on other taxonomic groups.

Meta-analysis reveals global variations in plant diversity effects on productivity

Positive effects of plant diversity on productivity have been globally demonstrated and explained by two main effects: complementarity effects and selection effects1-4. However, plant diversity experiments have shown substantial variation in these effects, with driving factors poorly understood4-6. On the basis of a meta-analysis of 452 experiments across the globe, we show that productivity increases on average by 15.2% from monocultures to species mixtures with an average species richness of 2.6; net biodiversity effects are stronger in grassland and forest experiments and weaker in container, cropland and aquatic ecosystems. Of the net biodiversity effects, complementarity effects and selection effects contribute 65.6% and 34.4%, respectively. Complementarity effects increase with phylogenetic diversity, the mixing of nitrogen-fixing and non-nitrogen-fixing species and the functional diversity of leaf nitrogen contents, which indicate the key roles of niche partitioning, biotic feedback and abiotic facilitation in complementarity effects. More positive selection effects occur with higher species biomass inequality in their monocultures. Complementarity effects increase over time, whereas selection effects decrease over time, and they remain consistent across global variations in climates. Our results provide key insights into understanding global variations in plant diversity effects on productivity and underscore the importance of integrating both complementarity and selection effects into strategies for biodiversity conservation and ecological restoration.

Global decoupling of functional and phylogenetic diversity in plant communities

Plant communities are composed of species that differ both in functional traits and evolutionary histories. As species' functional traits partly result from their individual evolutionary history, we expect the functional diversity of communities to increase with increasing phylogenetic diversity. This expectation has only been tested at local scales and generally for specific growth forms or specific habitat types, for example, grasslands. Here we compare standardized effect sizes for functional and phylogenetic diversity among 1,781,836 vegetation plots using the global sPlot database. In contrast to expectations, we find functional diversity and phylogenetic diversity to be only weakly and negatively correlated, implying a decoupling between these two facets of diversity. While phylogenetic diversity is higher in forests and reflects recent climatic conditions (1981 to 2010), functional diversity tends to reflect recent and past climatic conditions (21,000 years ago). The independent nature of functional and phylogenetic diversity makes it crucial to consider both aspects of diversity when analysing ecosystem functioning and prioritizing conservation efforts.

Winner-loser plant trait replacements in human-modified tropical forests

Anthropogenic landscape modification may lead to the proliferation of a few species and the loss of many. Here we investigate mechanisms and functional consequences of this winner-loser replacement in six human-modified Amazonian and Atlantic Forest regions in Brazil using a causal inference framework. Combining floristic and functional trait data for 1,207 tree species across 271 forest plots, we find that forest loss consistently caused an increased dominance of low-density woods and small seeds dispersed by endozoochory (winner traits) and the loss of distinctive traits, such as extremely dense woods and large seeds dispersed by synzoochory (loser traits). Effects on leaf traits and maximum tree height were rare or inconsistent. The independent causal effects of landscape configuration were rare, but local degradation remained important in multivariate trait-disturbance relationships and exceeded the effects of forest loss in one Amazonian region. Our findings highlight that tropical forest loss and local degradation drive predictable functional changes to remaining tree assemblages and that certain traits are consistently associated with winners and losers across different regional contexts.

Satellite Observations Reveal a Positive Relationship Between Trait-Based Diversity and Drought Response in Temperate Forests

Climate extremes such as droughts are expected to increase in frequency and intensity with global change. Therefore, it is important to map and predict ecosystem responses to such extreme events to maintain ecosystem functions and services. Alongside abiotic factors, biotic factors such as the proportion of needle and broadleaf trees were found to affect forest drought responses, corroborating results from biodiversity-ecosystem functioning (BEF) experiments. Yet it remains unclear to what extent the behavior of non-experimental systems at large scales corresponds to the relationships discovered in BEF experiments. Using remote sensing, the trait-based functional diversity of forest ecosystems can be directly quantified. We investigated the relationship between remotely sensed functional richness and evenness and forest drought responses using data from temperate mixed forests in Switzerland, which experienced an extremely hot and dry summer in 2018. We used Sentinel-2 satellite data to assess aspects of functional diversity and quantified drought response in terms of resistance, recovery, and resilience from 2017 to 2020 in a scalable approach. We then analyzed the BEF relationship between functional diversity measures and drought response for different aggregation levels of richness and evenness of three physiological canopy traits (chlorophyll, carotenoid/chlorophyll ratio, and equivalent water thickness). Forest stands with greater trait richness were more resistant and resilient to the drought event, and the relationship of trait evenness with resistance or resilience was hump-shaped or negative, respectively. These results suggest forest functional diversity can support forests in such drought responses via a mixture of complementarity and dominance effects, the first indicated by positive richness effects and the second by negative evenness effects. Our results link ecosystem functioning and biodiversity at large scales and provide new insights into the BEF relationships in non-experimental forest ecosystems.

Plant Species Better Adapted to Climate Change Need Agricultural Extensification to Persist

Agricultural intensification and climate change have led to well-known vegetation shifts in agricultural landscapes. However, concomitant plant functional changes in agroecosystems, especially at large scales, have been seldom characterised. Here, we used a standardised yearly monitoring of > 400 agricultural field margins in France to assess the temporal response of vegetation diversity and functional traits to variations in climate and intensity of agricultural practices (herbicides, fertilisation and mowing) between 2013 and 2021. We observed clear temporal trends of increasing warming and aridity, but trends towards agricultural extensification were weak or nonsignificant. Our results showed functional changes in plant communities over time, driven mostly by climate change and suggested selective forces opposing climate change to agricultural intensification. This translated as a temporal decline of competitive and ruderal species in favour of stress-tolerant species, putting plant communities in agroecosystems in a difficult position to escape both climate and agricultural pressures at the same time.

Heating up the roof of the world: tracing the impacts of in-situ warming on carbon cycle in alpine grasslands on the Tibetan Plateau

Climate warming may induce substantial changes in the ecosystem carbon cycle, particularly for those climate-sensitive regions, such as alpine grasslands on the Tibetan Plateau. By synthesizing findings from in-situ warming experiments, this review elucidates the mechanisms underlying the impacts of experimental warming on carbon cycle dynamics within these ecosystems. Generally, alterations in vegetation structure and prolonged growing season favor strategies for enhanced ecosystem carbon sequestration under warming conditions. Whilst warming modifies soil microbial communities and their carbon-related functions, its effects on soil carbon release fall behind the increased vegetation carbon uptake. Despite the fact that no significant accumulation of soil carbon stock has been detected upon warming, notable changes in its fractions indicate potential shifts in carbon stability. Future studies should prioritize deep soil carbon dynamics, the interactions of carbon, nitrogen, and phosphorus cycles under warming scenarios, and the underlying biological mechanisms behind these responses. Furthermore, the integration of long-term warming experiments with Earth system models is essential for reducing the uncertainties of model predictions regarding future carbon-climate feedback in these climate-sensitive ecosystems.

Nutrient cycling characteristics along a chronosequence of forest primary succession in the Hailuogou Glacier retreat area, eastern Tibetan Plateau

Background

The Hailuogou Glacier has been continuously retreating since the end of the Little Ice Age, resulting in a 125-year soil chronosequence and a complete primary forest succession sequence. Nutrient cycling and utilization are the foundation to forest succession processes and dynamic changes, directly influencing the structure and stability of ecosystems. However, our understandings on the characteristics of ecosystem nutrient accumulation and recycling during succession, especially in the context of primary succession within glacier retreat areas, remain limited. To address this, we investigated nutrient characteristics across six forest primary succession sites in the Hailuogou Glacier retreat area.

Methods

Six sites representing three forest stages: the pioneer plant stage (S1), the broad-leaved forest stage (S2-S4), and the coniferous forest stage (S5-S6). Three quadrats were established at each site, and measurements of biomass as well as soil characteristics were documented within each quadrat. Subsequently, we collected samples of vegetation, soil and litter. By measuring the concentrations of N, P, K, Ca, and Mg in vegetation and soil and combining with the data of the quadrat survey, the pools and nutrient characteristics of N, P, K, Ca, and Mg in various components of the ecosystem were calculated at each site.

Results

Our findings indicated that: (1) Nutrient pools, excluding the soil C layer, increased with forest primary succession, reaching 5,995.71 kg hm-2 N, 461.83 kg hm-2 P, 3,798.09 kg hm-2 K, 7,559.81 kg hm-2 Ca and 1,948.13 kg hm-2 Mg at site S6; however, the pools of P, K, and Mg in the Oa layer, and Ca and Mg in the tree layer, attained their peak levels at sites S3 to S4. (2) The pools of N, Ca, and Mg in the organic soil were significantly greater than vegetation. Although over 60% of the P and K were stored in the organic soil at site S1, these proportions shifted, with vegetation holding 60.71% of P and 56.86% of K at site S5. (3) Broad-leaved forests exhibited higher nutrient return, cycling, and absorption, thereby accelerating nutrient circulation and depleting soil nutrients to maintain growth. In contrast, coniferous forests were more efficient at nutrient utilization and storage, retaining nutrients and maintaining high biomass and productivity in nutrient-poor environments. Overall, these findings highlighted that the nutrients in each component of the ecosystem continue to accumulate with forest primary succession. Coniferous forests' nutrient cycling mechanisms offer a competitive edge in nutrient-poor environments, enhancing ecosystem stability.