Deciduous and Evergreen Leaf Habit Structures Intraspecific Trait Expression along an Elevational Gradient.

ABSTRACT Shifts in leaf functional traits and their interrelationships are expected to mirror plant ecological strategies throughout successional gradients. However, little is known about how these traits and their correlations vary across ecological scales during succession, particularly in Mediterranean ecosystems. This study examines the variability of leaf functional traits and CSR (Competitor, Stress-tolerant, Ruderal) strategies across and within Phillyrea angustifolia, Pistacia lentiscus, and Quercus coccifera growing in a matorral and a nearby sacred grove, representing contrasting successional stages and environmental conditions. For each species, 10 individuals per site were assessed for two ecophysiological traits (relative chlorophyll content and leaf thickness) and three structural allocation traits (leaf tissue density, specific leaf area, and leaf dry matter content), along with CSR strategies. Trait responses to changes in soil nutrients, light, and water availability during succession were both species- and trait-specific. When considering all species together, trait correlations aligned with those described by the global leaf economic spectrum. Thus, Q. coccifera and P. angustifolia shifted from conservative or stress-tolerant strategies in the matorral, viewed as a regressive successional stage, toward more acquisitive or competitive strategies in the sacred grove, regarded as a climax stage. Structural allocation traits showed high intraspecific variation and inconsistent within-species correlations, making them reliable indicators of local-scale adaptive strategies. In contrast, ecophysiological traits exhibited more stable relationships across scales and were largely driven by interspecific variation, limiting their usefulness for predicting intraspecific responses along local successional gradients.

Understanding how leaf water relations integrate with carbon economy is central to plant physiological ecology and to predictions of vegetation responses to environmental change, yet the degree of their coordination remains debated. We investigated relationships between leaf pressure-volume (PV) traits (leaf-specific capacitance at full turgor per dry mass (C*ft,mass), osmotic potential at the turgor loss point (πtlp), and other PV traits) and leaf economics spectrum (LES) traits (leaf nitrogen content, specific leaf area, and photosynthetic capacity) across temperate, subtropical, and tropical forests. These two suites of traits exhibited statistically partial coordination: C*ft,mass was tightly coupled with LES traits, whereas πtlp was independent of the LES framework, and this partial coupling was primarily driven by leaf saturated water content. Notably, coordination was strongest at the subtropical site, where conservative strategies strengthened the integration between PV and LES traits, thereby improving resource-use efficiency. This partial coupling provides insights into the multidimensional nature of plant functional strategies and the mechanisms underpinning species coexistence across forest types.

Anatomical and physiological trade-offs underlying the leaf economics spectrum in tropical Andean montane forests.

Mediterranean-type ecosystems occur in five regions worldwide and are characterized by intense summer drought that constrains plant carbon gain and water-use strategies. Along the leaf economics spectrum, herbs typically exhibit higher photosynthetic capacity but lower water-use efficiency than woody species due to greater stomatal (gₛ) and mesophyll conductance (gₘ). However, this expectation may not hold under the particularly arid summer conditions of the central Chilean matorral, where prolonged drought acts as a strong environmental filter on plant water-use strategies. Here, we evaluated photosynthetic capacity, diffusional and biochemical limitations, and intrinsic water-use efficiency (iWUE) in co-occurring herbs, shrubs, and trees. Using combined gas exchange, chlorophyll fluorescence, and carbon isotope composition (δ13C), we quantified gₛ and gₘ, partitioned photosynthetic limitations, and compared traditional iWUE with a mesophyll-integrated metric (iWUEmes). Herbs exhibited the highest area- and mass-based photosynthetic rates, whereas shrubs and trees showed progressively lower values, driven primarily by diffusional rather than biochemical limitations. Classical iWUE (Aₙ/gₛ) did not differ among functional groups, whereas iWUEmes showed a significant overall effect, with trees differing from herbs and shrubs, indicating divergence in carbon-water trade-offs. Evergreen trees, characterized by high leaf mass per area and low gₘ, experienced the strongest diffusional limitation. Overall, our findings demonstrate that mesophyll conductance plays a central role in regulating photosynthetic performance and water-use strategies, refining expectations derived from global trait-based frameworks and improving predictions of plant responses to increasing aridity in Mediterranean-type ecosystems.

Plants employ multiple strategies to adapt to their growth environment. Characterizing key dimensions in plant trait space is important for understanding functional diversity within ecosystems. Leaf and root functional traits have been studied in the context of resource economics, but whether they covary, and through which mechanisms, is still debated. We investigated this in subtropical forests by sampling root and leaf traits on individuals of co-existing species in two communities with different resource availability. We found largely non-correlated variation between leaf and fine root traits both across and within communities, and a clear decoupling between leaf economic spectrum and root economic space, independent of evolutionary history. Our results suggest that leaf-root trait relationships are shaped by an interplay between microenvironmental heterogeneity that drives decoupling and shared selection pressures promoting covariation. The interplay explains the weak observed coordination and highlights the importance of environmental context in predicting above- and below-ground plant functions.

The relationship between herbaceous above ground biomass and species richness typically exhibits a unimodal pattern, shifting from positive under low-precipitation conditions to negative under high-precipitation conditions. While shrub encroachment generally reduces both herbaceous aboveground biomass and diversity, how shrubs mediate the herbaceous biomass-richness relationship under altered precipitation regimes remains unclear. By synthesizing data from globally distributed precipitation manipulation experiments, we reveal contrasting herbaceous biomass-diversity responses in grasslands and shrublands. In grasslands, reduced precipitation shifts the peak of the unimodal herbaceous biomass-richness curve toward lower biomass, whereas increased precipitation shifts it toward greater biomass. In contrast, the peak of the unimodal relationship in shrub-dominated systems shows no significant shifts across precipitation extremes. These global patterns are supported by a 5-year field experiment in a desert steppe in Northern China, which further shows that precipitation change strongly affects species richness through soil water availability in grasslands, while exerting weaker effects through modifications of the fast-slow leaf economics spectrum in shrublands. These findings demonstrate that shrub encroachment can constrain precipitation-induced changes in herbaceous biomass-diversity relationships, providing important insights into how woody plant expansion interacts with climate change to influence ecosystem structure and function.

The ratio of leaf surface area to dry mass, specific leaf area (SLA), relates function to carbon investment, but how the environment impacts SLA and whether SLA represents whole-plant resource acquisition remains debated. We tested two hypotheses using 12 Rhododendron species from four taxonomic sections with different leaf habits: (1) for leaves, we hypothesized that species, leaf position and light interception impact SLA, but higher SLA would be accompanied by higher net photosynthesis (A), stomatal conductance (gs), and maximum leaf hydraulic conductance (Kleaf), maintaining A/gs and Kleaf/gs across the canopy, and (2) for species, we hypothesized those from stressful climates would have lower SLA, higher Kleaf, higher stomatal density, and smaller stomata. At the leaf-scale, Kleaf was higher for species with lower SLA, contrary to predictions. We observed strong coordination of SLA and carbon to nitrogen ratio, but the relationship of Kleaf/gs to SLA was characterized by species replacement along the leaf economic spectrum, suggesting weak leaf-level trait coordination as a mechanism for low drought tolerance. Across species, lower SLA was associated with lower summer precipitation, lower precipitation seasonality, and larger guard cells. We show that leaf habit and habitat associations shape the functional significance of SLA, determining resource acquisition at leaf and species scales.

Mycorrhizal phosphorus (P)-scavenging strategies are inefficient in severely P-impoverished environments; yet many mycorrhizal species occur here. How these species acquire P and how their acquisition coordinates with root and leaf traits remain unknown. We measured rhizosheath acid-phosphatases, leaf P-resorption efficiency and root and leaf economic traits and defence metabolites, such as phenolics and flavonoids, of Hibbertia hypericoides (Dilleniaceae) and H. racemosa in monoculture with arbuscular mycorrhizal fungal inoculation and in a mixture with P-mobilising Banksia attenuata (Proteaceae) with or without arbuscular mycorrhizal fungal inoculation. Phosphorus acquisition of both Hibbertia species was facilitated by B. attenuata, but through different interactions: H. hypericoides, non-mycorrhizal despite having been inoculated, used its roots, whereas H. racemosa, forming arbuscular mycorrhizal associations following inoculation, relied on mycorrhizal interactions with B. attenuata. This was linked to positions along the 'collaboration' dimension of root economic space and coordinated with root defence metabolites. Hibbertia species diverged along the leaf economic spectrum, with higher scores (more conservative strategy) negatively correlated with leaf P-resorption efficiency. We conclude that arbuscular mycorrhizal fungi play a key role in the P-acquisition strategy of H. racemosa. Root and leaf traits and rhizosheath acid-phosphatase activity efficiency interacted and contributed to the growth of both Hibbertia species.

Evergreen vs. deciduous species: Whose water use efficiency can influence the plant trait spectrum in the karst evergreen-deciduous mixed broad-leaved forests?

Leaf respiration is a key metabolic process controlling leaf carbon balance. However, empirical data on leaf respiration, particularly in the light (RL), remain scarce for ferns, and no study has systematically compared respiration-trait relationships between ferns and seed plants. We measured seven leaf traits, including leaf respiration in the dark (RD), RL, light-saturated photosynthetic rate (Asat), leaf N and P content, leaf dry mass per unit area (LMA), and leaf dry mass content (LDMC) in 19 ferns. These fern data were analyzed in comparison with seed plant data from the Glopnet data set. Light inhibition of leaf respiration averaged 37%. Ferns had significantly lower LMA, Asat, and RD than seed plants. Standardized major axis analyses (SMA) revealed the slopes of RD vs. LMA, Asat, and P differed significantly between ferns and seed plants, while RD-N relationships shared common slopes, but their intercept differed markedly. Generalized linear models identified LMA and RD as the strongest predictors of RL, jointly explaining 70.6% of its variation. The terrestrial understory ferns employ a distinct "low-cost, slow-cycling" strategy-characterized by a unique combination of low leaf construction cost (LMA) and low metabolic rates (photosynthesis and respiration), which deviates from the traditional fast-slow leaf economics spectrum. The divergent respiration-trait relationships suggest that applying trait-based models parameterized solely for seed plants to ferns may introduce uncertainty into ecosystem models. This highlights the value of incorporating fern-specific trait relationships to refine projections of the global carbon cycle.

Abstract Biodiversity loss threatens the stability of ecosystem functions such as productivity, yet how plant functional traits regulate the two key components of ecosystem stability, species stability and species asynchrony, remains unclear. Asynchrony is often attributed to trait differences among species along the slow–fast spectrum, reflecting contrasting responses to environmental fluctuations, but may also arise from competitive interactions among species with similar growth strategies, a mechanism that is difficult to detect without experimentally manipulating interspecific coexistence. In a five‐year grassland biodiversity experiment (2018–2022), we measured two functional traits central to the leaf economics spectrum, specific leaf area (SLA) and leaf dry matter content (LDMC) in 2022. Using more than 2000 leaf samples, we assessed how species' mean trait values, intraspecific trait variation and interspecific trait dissimilarity relate to species stability and asynchrony across a gradient of species richness. Species stability declined consistently with increasing mean SLA, indicating lower temporal stability in species with faster strategies, whereas mean LDMC was not related to stability. Greater intraspecific variation in SLA and LDMC reduced species stability in monocultures but not in polycultures. The relationship between interspecific trait dissimilarity and species asynchrony also depended on species richness. In monocultures, LDMC‐based trait dissimilarity was negatively associated with temporal correlations—that is, greater functional dissimilarity among species corresponded to higher asynchrony. However, in species‐rich mixtures, temporal correlations decreased as species interactions intensified, and the relationship shifted to positive, indicating that species with similar traits exhibited higher asynchrony. Synthesis. Our findings demonstrate that species' mean positions along the slow–fast spectrum strongly shape temporal stability, whereas the influences of within‐ and between‐species trait variation depend on the extent of interspecific coexistence. This highlights that trait‐based predictions of community stability must explicitly account for species richness and the balance between environment‐driven and interaction‐driven temporal dynamics.

Understanding how plants adjust to changing rainfall and intensified drought is vital, particularly in the Mediterranean region. The Leaf Economics Spectrum (LES) framework distinguishes fast-growing plants with high specific leaf area (SLA) and low leaf dry matter content (LDMC) from resource-conserving plants with opposite traits. In drier environments, plants can be expected to exhibit lower SLA and higher LDMC to minimize water loss and enhance drought resilience. However, it is unclear whether this expectation holds within species among locally adapted populations, and how it is modulated plastically by drought and competition.This study investigated SLA and LDMC in five Mediterranean annual plant species across a macroclimatic rainfall gradient (89-926 mm annual rainfall) and contrasting microclimates: more mesic north- and more arid south exposures. Seeds were collected at 15 sites along this gradient, and plants were grown under controlled greenhouse conditions with three experimental treatments: control, drought, and competition.Contrary to LES expectations, plants from drier macroclimates had mostly evolved higher SLA and lower LDMC, suggesting that drought escape strategies via rapid growth and early reproduction were favored over conservative resource use. Microclimatic variation in leaf traits was smaller than macroclimatic variation, although in two species it showed the same trend, with south-exposure plants displaying lower SLA and/or higher LDMC. Plastic responses to drought consistently reduced SLA and increased LDMC, and vice-versa under competition, thus countering the genetically-based macroclimatic pattern. Interestingly, mesic populations showed stronger plastic shifts to competition.Our results show that evolution favored acquisitive leaves in drier sites, while plasticity modulated leaf traits in the opposite direction under drought stress and competition. These findings illustrate the interplay between evolutionary and plastic responses, underscoring the importance of considering both genetic differentiation and plasticity when assessing annual plant responses to future climate change.

Large terrestrial herbivores play crucial roles in shaping ecosystem structure and function through their foraging activities. Still, the dietary ecology of elusive tropical species remains poorly understood. We investigated the diet composition of lowland tapirs (Tapirus terrestris), the largest terrestrial herbivore in the Neotropics, using DNA metabarcoding of fecal samples from 31 latrines in Carlos Botelho State Park, Brazil. We characterized local plant communities through vegetation plots and analyzed five leaf economic spectrum (LES) traits from both consumed and surrounding vegetation to assess selective feeding patterns. Lowland tapirs consumed 61 plant species from 69 genera and 46 families, predominantly those from the Melastomataceae, Asteraceae, and Myrtaceae families. Beta-diversity analysis revealed high compositional turnover among latrines, with a high dissimilarity index, indicating that the samples being compared are distinct in species composition. The plant composition in tapir diets differed significantly from that of the surrounding vegetation, suggesting that this species forages on distinct plant species across its extensive home range rather than consuming locally abundant species. Finally, the functional trait analysis revealed no significant differences between the dietary species and the surrounding vegetation in LES traits. Tapirs consumed plants that spanned both "fast" (high specific leaf area and high nitrogen content) and "slow" (high leaf dry matter content and thick leaves) strategies, indicating a broad dietary tolerance rather than trait-based selectivity. This suggests that tapirs can adapt to diverse plant textures and nutritional profiles, browsing on leaves ranging from tough to softer and more digestible. Our findings demonstrate that lowland tapirs exhibit generalist feeding strategies, which promote high plant species turnover, potentially contributing to the maintenance of tropical forest diversity, as observed in the Atlantic forest. Given the critical threats facing this endangered megafauna, understanding their generalist diet is essential for developing effective conservation strategies.

Understanding crop responses to simultaneous environmental stressors is critical for safeguarding agricultural productivity. Yet, how microplastics (MPs) contamination interacts with water deficit to affect crop physiology, and which functional traits mediate such responses, remains poorly understood. We quantified crop growth parameters and 22 functional traits in two wheat varieties differing in drought sensitivity-drought-sensitive ('SL') and drought-tolerant ('SN')-under four treatments: control, single MPs, single mild water deficit, and combined stress. We characterized associations among leaf economic traits, water-relations traits, and eco-physiological performance. Combined stress reduced shoot dry weight by 28.32% in 'SN' and 41.25% in 'SL'. Under combined stress, 'SN' exhibited more acquisitive trait strategies than 'SL', thereby alleviating growth suppression. The leaf economics spectrum (PC1) showed positive correlations with root activity and water-use efficiency, whereas transpiration rate, stomatal conductance, and leaf water potential were negatively associated with root activity. Our results reveal that wheat resistance to combined MPs and water deficit is enhanced through acquisitive strategies that promote drought avoidance mechanisms, contrasting with the drought tolerance conventionally linked to conservative strategies. The tight coupling between leaf economics and water-relations traits underpins adaptive strategies, emphasizing the importance of trait-based optimization for improving crop performance under emerging multi-stressor environments.

The generality of the worldwide leaf economics spectrum (LES) has made it a pillar of trait-based ecological research. Yet, few studies have examined the processes shaping the evolution of the LES within species, in part, because most species occupy only a small portion of the LES. To address this gap, we took advantage of the distinct leaf economics strategies present in different ecotypes of the phenotypically diverse perennial grass Panicum virgatum (switchgrass) to generate a genetic mapping population, which we planted in common gardens at three sites spanning 12 degrees of latitude in the central United States. With this genetic mapping population, we evaluated two potentially interacting causes of LES evolution: 1) genetic architecture, where multiple traits are influenced by either the same gene (pleiotropy) or by genes in close physical proximity (genetic linkage), and 2) correlational selection, where selection acts on traits in combination rather than in isolation. We found that shared genetic architecture influenced covariation between photosynthetic rate (AMASS) and leaf nitrogen (NMASS) and between AMASS and leaf mass per area (LMA). We also found that correlational selection favored the trait combinations predicted by the LES (e.g., high LMA with low NMASS or low LMA with high NMASS) and disfavored other, mismatched trait combinations at two of the three sites. Together, these results demonstrate how the evolution of an integrated LES within species can arise from multiple evolutionary causes.

Understanding intraspecific functional trait variability (ITV) is crucial for elucidating plant functional strategies under environmental change. This study investigates the functional responses of 129 Mediterranean olive (Olea europaea L.) cultivars conserved in the Worldwide Olive Germplasm Bank of Marrakech (WOGBM), focusing on three key leaf traits: specific leaf area (SLA), specific leaf water content (SLWC), and leaf area (LA). Substantial ITV was observed, with variability predominantly driven by cultivar differences and geographic origin. LA accounted for the highest within-cultivar variability (43.60%), followed by SLWC (31.67%) and SLA (17.92%). Geographic origin significantly influenced trait expression, with eastern Mediterranean cultivars exhibiting conservative resource-use strategies (high SLWC, low SLA, and LA), while western cultivars displayed acquisitive strategies (high SLA and LA, low SLWC). Principal component analysis further differentiated eastern and western cultivars, reflecting biogeographical and evolutionary influences. The relationship between LA and climatic variables suggests climate-driven selection, where cultivars from wetter regions develop larger leaves to optimize light capture and carbon assimilation, whereas those from drier environments exhibit smaller leaves to reduce water loss. These findings highlight a trade-off between resource acquisition and conservation, supporting the leaf economic spectrum at the intraspecific level. This study underscores the importance of ITV in olive diversification and adaptation, providing insights for breeding, conservation, and climate resilience. A trait-based approach proves valuable for exploring domestication processes and plant responses to environmental gradients.

Evidence shows that local functional trait composition and diversity along the fast-slow leaf economics spectrum can predict the temporal stability of community productivity in response to environmental changes. However, it remains unclear whether these relationships persist at larger spatial scales. Combining a field survey of plant diversity with remote sensing estimates of primary productivity across a large environmental gradient in 235 grasslands across the Qinghai-Tibet Plateau and the Inner Mongolia Plateau, we find that species richness contributes to stabilizing productivity, while functional diversity contributes to destabilizing productivity at the local scale. In contrast, we find no evidence that variation in species richness and functional diversity among local communities contributes to stabilizing productivity across larger spatial scales. While the relationships between environmental conditions and local diversity and stability differ between the two regions, the overall positive relationships between diversity and stability are consistent at both the local and larger spatial scales. Our study offers insights into how functional traits along the fast-slow leaf economics spectrum mediate the effects of environmental factors (e.g., precipitation) on ecosystem stability at contrasting spatial scales.

Highly efficient phosphorus (P)-use strategies have evolved in plants, allowing them to thrive in severely P-impoverished environments. However, it remains unclear how allocating leaf P to biochemical fractions, including specific P-containing metabolites, contributes to instantaneous photosynthetic P-use efficiency (iPPUE) and the position of species along the leaf economics spectrum (LES). We measured LES-associated traits (leaf mass per area, light-saturated photosynthetic rate, and P and nitrogen concentrations) and iPPUE in 12 coexisting Proteaceae, Fabaceae, Myrtaceae and Ericaceae from two severely P-impoverished soils. We characterised patterns of P allocation into lipids, nucleic acids, metabolites, a residual fraction and inorganic P, and identified P-containing metabolites within the metabolite-P fraction. We identified multiple P-utilisation strategies that were both species-dependent and soil context-dependent. The iPPUE and LES scores, representing leaf-level resource-use strategies, were positively associated with P concentrations in nucleic acids and the residual P fraction. Concentrations of key P-containing metabolites of the Calvin-Benson cycle, ribulose-1,5-bisphosphate and 3-phosphoglycerate, were positively correlated with and served as strong predictors of iPPUE and resource-use strategies within the LES. Species in severely P-impoverished habitats exhibited species-dependent and soil context-dependent P-allocation patterns and maintained specific P-containing metabolite concentrations. These trait combinations underpin high iPPUE and enable multiple resource-use strategies.

Evergreen–deciduous divergence governs the coupling of the leaf economics spectrum with foliar phosphorus fractions