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Characterizing variation and association of plant traits is critical for understanding plant adaptation strategies and community assembly mechanisms. However, little is known about the leaf trait variations of desert plants and their association with different life forms. We used principal component analysis, Pearson's correlation, phylogenetic independent contrasts, linear mixed model, and variance decomposition to explore the variation and association of 10 leaf traits in 22 desert plants in the arid area of northwest China. We found that: (1) the contribution of interspecific variation to the overall variation was greater than the intraspecific variation of all the studied leaf traits; (2) intraspecific and interspecific variation in leaf traits differed among life forms. Some leaf traits, such as tissue density of shrubs and specific leaf area of herbs, exhibited greater intraspecific than interspecific variation, while other traits exhibited the inverse; (3) desert shrubs corroborate the leaf economic spectrum hypothesis and had a fast acquisitive resource strategy, but herbs may not conform to this hypothesis; (4) there were trade‐offs between leaf traits, which were mediated by phylogeny. Overall, our results suggest that interspecific variation of leaf traits significantly contributes to the total leaf traits variation in desert plants. However, intraspecific variation should not be overlooked. There are contrasts in the resource acquisition strategies between plants life forms. Our results support understanding of the mechanisms underlying community assembly in arid regions and suggest that future works may focus on the variation and association of plant traits at both intra‐ and interspecific scales. Our results suggest that interspecific variation of leaf traits greatly contributes to the total leaf traits variation in desert plants but intraspecific variation should not be overlooked. There are differences in the resource strategies of plants of different life forms.

The interdependence of multiple traits allows plants to perform multiple functions. Acquiring an accurate representation of the interdependence of plant traits could advance our understanding of the adaptative strategies of plants. However, few studies focus on complex relationships among multiple traits. Here, we proposed use of leaf trait networks (LTNs) to capture the complex relationships among traits, allowing us to visualize all relationships and quantify how they differ through network parameters. We established LTNs using six leaf economic traits. It showed that significant differences in LTNs of different life forms and growth forms. The trait relationships of broad-leaved trees were tighter than conifers; thus, broad-leaved trees could be more efficient than conifers. The trait relationships of shrubs were tighter than trees because shrubs require multiple traits to co-operate efficiently to perform multiple functions for thriving in limited resources. Furthermore, leaf nitrogen concentration and life span had the highest centrality in LTNs; consequently, the environmental selection of these two traits might impact the whole phenotype. In conclusion, LTNs are useful tools for identifying key traits and quantifying the interdependence of multiple traits.

Key message Evergreen and deciduous species in a subtropical urban forest of Eastern China exhibit pronounced differences in leaf traits, with evergreens species showing lower photosynthetic rate on a leaf mass basis and leaf nutrient contents, but higher leaf mass per area ratio, leaf thickness, leaf carbon content, and leaf carbon-to-nitrogen ratio, whereas deciduous species show the opposite pattern, reflecting distinct resource-use characteristics. In addition, leaf economic and hydraulic traits are coordinated, with higher vein density associated with higher scores along the leaf economics spectrum PCA axis, reflecting resource-acquisitive characteristics and highlighting vein density as a key trait linking water transport capacity to carbon economy. Context Understanding how leaf economics and hydraulic traits vary and interact among different plant growth forms and leaf habits is essential for elucidating plant adaptability. However, the coupling of these two trait dimensions remains unclear within urban forest ecosystems where environmental conditions differ significantly from natural forests. Aims This study aimed to investigate variation and coordination between leaf economics and hydraulic traits among woody species in a subtropical urban forest of Eastern China, focusing on differences between leaf habits and growth forms. Methods We measured 10 leaf economic traits and 4 hydraulic traits across 53 woody species from a subtropical urban forest. Results Evergreen species exhibited lower photosynthetic rate on a leaf mass basis, leaf nutrient contents, and higher leaf mass per area ratio, leaf thickness, leaf carbon content, and leaf carbon-to-nitrogen ratio, consistent with resource-conserving characteristics. Deciduous species showed higher values of these parameters, indicative of rapid resource acquisition. Shrubs displayed significantly higher phosphorous content in leaves than trees. Vein density was positively correlated with the leaf economic spectrum. Conclusion These findings reveal a coordination between leaf hydraulic and economic traits. This coupling highlights the balance between water transport and resource acquisition characteristics.

This is the first plant functional trait database for Nova Scotia, Canada. The data contained here were collected between 2016 and 2019 from locations around Halifax, Nova Scotia. The species selected for trait collection were chosen based on species inventories taken across Nova Scotian coastal barrens and from green roofs at Saint Mary’s University. The purpose of the coastal barren trait data was to understand community assembly in this understudied ecosystem. The green roof inventory was included as coastal barren species are known to succeed on green roofs in Nova Scotia. The green roof trait data was used to answer questions surrounding coexistence and trait divergence, and community assembly and spatial heterogeneity. In total, this database contains 14,341 trait values from 203 species comprising 130 genera and 53 families. The majority of species are commonly found on coastal barrens (84 species), disturbed sites (48 species), and forests (27 species). Additionally, this database contains trait data for 30 species that have been successfully established (survival for >1 year) on green roofs in Nova Scotia and ruderal species that commonly colonize both green roofs and coastal barrens. This database contains 12 plant functional traits: leaf thickness (203 species), leaf area (203 species), specific leaf area (203 species), leaf dry matter content (203 species), plant height (203 species), canopy width (203 species), seed mass (79 species), seed shape (61 species), root radius (22 species), leaf phosphorus content (3 species), leaf nitrogen content (30 species), and leaf carbon content (30 species). The species in this database can be subdivided into 10 growth forms, with the majority of species characterized as forbs (75 species), shrubs (56 species), or graminoids (33 species). This data set is freely available for scientific use; when used in published analyses, this paper should be referred to as the data source.

Little attention has been paid to the impact of vertical canopy position on the leaf spectral properties of tall trees, and few studies have explored the ability of leaf spectra to characterize the variation of leaf traits across different canopy positions. Using a tower crane, we collected leaf samples from three canopy layers (lower, middle, and upper) and measured eight leaf traits (equivalent water thickness, specific leaf area, leaf carbon content, leaf nitrogen content, leaf phosphorus content, leaf chlorophyll content, flavonoid, and nitrogen balance index) in a subtropical evergreen broadleaved forest. We evaluated the variability of leaf traits and leaf spectral properties, as well as the ability of leaf spectra to track the variation of leaf traits among three canopy layers for six species within the entire reflectance spectrum. The results showed that the eight leaf traits that were moderately or highly correlated with each other showed significant differences along the vertical canopy profile. The three canopy layers of leaf spectra showed contrasting patterns for light-demanding (Castanopsis chinensis, Castanopsis fissa, Schima superba, and Machilus chinensis) and shade-tolerant species (Cryptocarya chinensis and Cryptocarya concinna) along the vertical canopy profile. The spectra at the lower and upper canopy layers were more sensitive than the middle layer for tracking the variation of leaf chlorophyll and flavonoid content. Our results revealed that it is important to choose an appropriate canopy layer for the field sampling of tall trees, and we suggest that flavonoid is an important leaf trait that can be used for mapping and monitoring plant growth with hyperspectral remote sensing.

Phenotypic plasticity is an important adaptive strategy that enables plants to respond to environmental changes, particularly temperature fluctuations associated with global warming. In this study, the phenotypic plasticity of Iris pumila leaf traits in response to an elevated temperature (by 1 °C) was investigated under controlled experimental conditions. In particular, we investigated important functional and mechanistic leaf traits: specific leaf area (SLA), leaf dry matter content (LDMC), specific leaf water content (SLWC), stomatal density (SD), leaf thickness (LT), and chlorophyll content. The results revealed that an elevated temperature induced trait-specific plastic responses, with mechanistic traits exhibiting greater plasticity than functional traits, reflecting their role in short-term acclimation. SLA and SD increased at higher temperatures, promoting photosynthesis and gas exchange, while reductions in SLWC, LDMC, LT, and chlorophyll content suggest a trade-off in favor of growth and metabolic activity over structural investment. Notably, chlorophyll content exhibited the highest plasticity, emphasizing its crucial role in modulating photosynthetic efficiency under thermal stress. Correlation analyses revealed strong phenotypic integration between leaf traits, with distinct trait relationships emerging under different temperature conditions. These findings suggest that I. pumila employs both rapid physiological adjustments and longer-term structural strategies to cope with thermal stress, with mechanistic traits facilitating rapid adjustments and functional traits maintaining ecological stability.

Leaf respiration in the dark (R dark ) and light (R day ) is poorly characterized in diverse tropical ecosystems, and little to no information exists on the degree of light suppression in common tree species within the Amazon basin, and their dependences upon plant functional traits and position within the canopy. We quantified R dark and apparent R day using the Kok method and measured key leaf traits in 26 tree individuals of different species distributed in three different canopy positions: canopy, lower canopy, and understory. To explore the relationships between the leaf traits we used the standardized major axis (SMA). We found that canopy trees had significantly higher rates of R dark and R day than trees in the understory. The difference between R dark and R day (the light suppression of respiration) was greatest in the understory (68 ± 9%, 95% CI) and lower canopy (49 ± 9%, 95% CI) when compared to the canopy (37 ± 10%, 95% CI). We also found that R day was significantly and strongly correlated with R dark ( p < 0.001) for all the canopy positions. Also, leaf mass per area (LMA) and leaf Phosphorus concentration (P) had a significant relationship with R dark ( p < 0.001; p = 0.003), respectively. In addition, a significant relationship was found for LMA in the canopy and lower canopy positions ( p = 0.009; p = 0.048) while P was only significant in the canopy ( p = 0.044). Finally, no significant relationship was found between R dark and nitrogen, sugars, and starch. Our results highlight the importance of including representation of the light suppression of leaf respiration in terrestrial biosphere models and also of accounting for vertical gradients within forest canopies and connections with functional traits.

Leaf functional traits allow plant survival and maintain their ecosystem function. Salinity affects leaf functional traits, but coordination among leaf functional traits is poorly known and may depend on salt severity. To increase our understanding of the coordination of leaf functional traits under salt stress, we determined hydraulic, gas exchange, and physiological and biochemical parameters in Populus euphratica Oliv. ( P. euphratica ) grown under salinity treatments, as well as gas exchange parameters under different CO 2 concentrations. We found that P. euphratica can reinforce its hydraulic capacity by increasing the water transfer efficiency of both its leaves and stems when a salinity threat occurs for a specific duration of stress. Its stems were more adaptable than leaves. The economic and hydraulic traits of P. euphratica leaves were consistent during the middle stages of salt stress, but inconsistent during the onset and late stages of salt stress. There was almost no biochemical limitation under severe salinity conditions, and CO 2 enrichment of P. euphratica had a greater effect on leaf economic traits. The mechanism of toxic ion exclusion based on water availability and intracellular mechanisms in leaves contributed to salt tolerance when P. euphratica was exposed to salinity stress. There was also a coordination mechanism for the plants during increasing salt stress. The leaf intracellular traits of P. euphratica can coordinate with the leaf economic and hydraulic traits and form a defense mechanism to reduce salt damage and guarantee growth under saline conditions. In conclusion, P. euphratica , the main constructional species of riparian forests, adapts to saline environments by adjustment and coordination of leaf functional traits, ensuring survival. These results provide a scientific basis for riparian forest restoration.

This study presents the Integrated Leaf Trait Analysis (ILTA), a workflow for the combined application of methodologies in leaf trait and insect herbivory analyses on fossil dicot leaf assemblages. The objectives were (1) to record the leaf morphological variability, (2) to describe the herbivory pattern on fossil leaves, (3) to explore relations between leaf morphological trait combination types (TCTs), quantitative leaf traits, and other plant characteristics ( ., phenology), and (4) to explore relations of leaf traits and insect herbivory. The leaves of the early Oligocene floras Seifhennersdorf (Saxony, Germany) and Suletice-Berand (Ústí nad Labem Region, Czech Republic) were analyzed. The TCT approach was used to record the leaf morphological patterns. Metrics based on damage types on leaves were used to describe the kind and extent of insect herbivory. The leaf assemblages were characterized quantitatively ( ., leaf area and leaf mass per area (LM )) based on subsamples of 400 leaves per site. Multivariate analyses were performed to explore trait variations. In Seifhennersdorf, toothed leaves of TCT F from deciduous fossil-species are most frequent. The flora of Suletice-Berand is dominated by evergreen fossil-species, which is reflected by the occurrence of toothed and untoothed leaves with closed secondary venation types (TCTs A or E). Significant differences are observed for mean leaf area and LM , with larger leaves tending to lower LM in Seifhennersdorf and smaller leaves tending to higher LM in Suletice-Berand. The frequency and richness of damage types are significantly higher in Suletice-Berand than in Seifhennersdorf. In Seifhennersdorf, the evidence of damage types is highest on deciduous fossil-species, whereas it is highest on evergreen fossil-species in Suletice-Berand. Overall, insect herbivory tends to be more frequently to occur on toothed leaves (TCTs E, F, and P) that are of low LM . The frequency, richness, and occurrence of damage types vary among fossil-species with similar phenology and TCT. In general, they are highest on leaves of abundant fossil-species. TCTs reflect the diversity and abundance of leaf architectural types of fossil floras. Differences in TCT proportions and quantitative leaf traits may be consistent with local variations in the proportion of broad-leaved deciduous and evergreen elements in the ecotonal vegetation of the early Oligocene. A correlation between leaf size, LM and fossil-species indicates that trait variations are partly dependent on the taxonomic composition. Leaf morphology or TCTs itself cannot explain the difference in insect herbivory on leaves. It is a more complex relationship where leaf morphology, LM , phenology, and taxonomic affiliation are crucial.

Background and aims – While tropical forests play an important role in carbon sequestration, they are assumed to be sensitive to rising temperatures and prolonged drought. Plant functional traits are useful for understanding and predicting the effects of such changes in plant communities. Here, we analyse the variation of leaf traits of understory woody species of the Congo Basin rainforests over a 60-year period using herbaria as tools and we verify if this variation is potentially related to recent climate change. Material and methods – Leaves of five shrub species were collected in 2019–2022 in Congolese old-growth forests (Yangambi Biosphere Reserve, DR Congo) from different positions on the shrub. These leaves were compared with herbarium specimens collected in the same area before 1960. For both periods, we assessed leaf size, specific leaf area, stomatal size, and stomatal density for all species. Key results – The variability of the functional traits of the understory woody species are independent of the position of the leaves in the crown. This allows for the use of historic herbarium collections for trait analyses on tropical understory shrubs. The traits of the recently collected leaves were notably different from the traits of herbarium leaves collected in pre-1960: recent leaves were significantly larger, had a higher Specific Leaf Area, a smaller stomata pore length, and, apart from Coffea canephora , showed a lower stomatal density. Conclusion – The difference in traits over time is probably related to the increase in temperature and to atmospheric CO 2 concentration, as the average temperature at Yangambi over the past 60 years has shown an upward trend consistent with global increasing CO 2 levels, while the average annual rainfall has remained unchanged. Our results provide a first insight into the response of forest species to climate change in the Congo Basin forests, and on how the understory species and the ecosystem will react in the long term, when the temperature further increases.