Leaf Economics Research Articles

Intraspecific leaf trait variation mediates edge effects on litter decomposition rate in fragmented forests.

There is strong trait dependence in species-level responses to environmental change and their cascading effects on ecosystem functioning. However, there is little understanding of whether intraspecific trait variation (ITV) can also be an important mechanism mediating environmental effects on ecosystem functioning. This is surprising, given that global change processes such as habitat fragmentation and the creation of forest edges drive strong trait shifts within species. On 20 islands in the Thousand Island Lake, China, we quantified intraspecific leaf trait shifts of a widely distributed shrub species, Vaccinium carlesii, in response to habitat fragmentation. Using a reciprocal transplant decomposition experiment between forest edge and interior on 11 islands with varying areas, we disentangled the relative effects of intraspecific leaf trait variation versus altered environmental conditions on leaf decomposition rates in forest fragments. We found strong intraspecific variation in leaf traits in response to edge effects, with a shift toward recalcitrant leaves with low specific leaf area and high leaf dry matter content from forest interior to the edge. Using structural equation modeling, we showed that such intraspecific leaf trait response to habitat fragmentation had translated into significant plant afterlife effects on leaf decomposition, leading to decreased leaf decomposition rates from the forest interior to the edge. Importantly, the effects of intraspecific leaf trait variation were additive to and stronger than the effects from local environmental changes due to edge effects and habitat loss. Our experiment provides the first quantitative study showing that intraspecific leaf trait response to edge effects is an important driver of the decrease in leaf decomposition rate in fragmented forests. By extending the trait-based response-effect framework toward the individual level, intraspecific variation in leaf economics traits can provide the missing functional link between environmental change and ecological processes. These findings suggest an important area for future research on incorporating ITV to understand and predict changes in ecosystem functioning in the context of global change.

Leaf habit and plant architecture integrate whole-plant economics and contextualize trait-climate associations within ecologically diverse genus Rhododendron.

Plant resource strategies negotiate a trade-off between fast growth and stress resistance, characterized by specific leaf area (SLA). How SLA relates to leaf structure and function or plant climate associations remains open for debate, and leaf habit and plant architecture may alter the costs versus benefits of individual traits. We used phylogenetic canonical correspondence analysis and phylogenetic least squares to understand the relationship of anatomy and gas exchange to published data on root, wood, architectural and leaf economics traits and climate. Leaf anatomy was structured by leaf habit and carbon to nitrogen ratio was a better predictor of gas exchange than SLA. We found significant correspondence of leaf anatomy with branch architecture and wood traits, gas exchange corresponded with climate, while leaf economics corresponded with climate, architecture, wood and root traits. Species from the most seasonal climates had the highest trait-climate correspondence, and different aspects of economics and anatomy reflected leaf carbon uptake versus water use. Our study using phylogenetic comparative methods including plant architecture and leaf habit provides insight into the mechanism of whole-plant functional coordination and contextualizes individual traits in relation to climate, demonstrating the evolutionary and ecological relevance of trait-trait correlations within a genus with high biodiversity.

Quantifying foliar trait variation and covariation in sun and shade leaves using leaf spectroscopy in eastern North America

Characterizing foliar trait variation in sun and shade leaves can provide insights into inter- and intra-species resource use strategies and plant response to environmental change. However, datasets with records of multiple foliar traits from the same individual and including shade leaves are sparse, which limits our ability to investigate trait-trait, trait-environment relationships and trait coordination in both sun and shade leaves. We presented a comprehensive dataset of 15 foliar traits from sun and shade leaves sampled with leaf spectroscopy, including 424 individuals of 110 plant species from 19 sites across eastern North America. We investigated trait variation, covariation, scaling relationships with leaf mass, and the effects of environment, canopy position, and taxonomy on trait expression. Generally, sun leaves had higher leaf mass per area, nonstructural carbohydrates and total phenolics, lower mass-based chlorophyll a + b, carotenoids, phosphorus, and potassium, but exhibited species-specific characteristics. Covariation between sun and shade leaf traits, and trait-environment relationships were overall consistent across species. The main dimensions of foliar trait variation in seed plants were revealed including leaf economics traits, photosynthetic pigments, defense, and structural traits. Taxonomy and canopy position collectively explained most of the foliar trait variation. This study highlights the importance of including intra-individual and intra-specific trait variation to improve our understanding of ecosystem functions. Our findings have implications for efficient field sampling, and trait mapping with remote sensing.

Trait divergence and opposite above- and below-ground strategies facilitate moso bamboo invasion into subtropical evergreen broadleaf forest.

Understanding the invasion of moso bamboo (Phyllostachys edulis) into adjacent evergreen broadleaf forest based on functional traits is crucial due to its significant influence on ecosystem processes. However, existing research has primarily focused on above- or below-ground traits in isolation, lacking a comprehensive integration of both. In this study, we conducted a trait-based analysis including 23 leaf traits and 11 root traits in three forest types - bamboo forest, mixed bamboo and broadleaf forest, and evergreen broadleaf forest - to investigate trait differences, phenotypic integration, and above- and below-ground resource strategies in bamboo and broadleaf species. Our findings demonstrated significant differences in leaf and root key traits between bamboo and broadleaf species, strongly supporting the "phenotypic divergence hypothesis". Bamboo exhibited stronger trait correlations compared to broadleaf species, indicating higher phenotypic integration. Above- and below-ground strategies were characterized by trade-offs rather than coordination, resulting in a multi-dimensional trait syndrome. Specifically, a unidimensional leaf economics spectrum revealed that bamboo with higher leaf N concentrations (LNC), P concentrations (LPC), and specific leaf area (SLA) adopted a "fast acquisitive" above-ground strategy, while broadleaf species with thicker leaves employed a "slow conservative" above-ground strategy. A two-dimensional root trait syndrome indicated a "conservation" gradient with bamboo adopting a "slow conservative" below-ground strategy associated with higher root tissue density (RTD), and broadleaf species exhibiting a "fast acquisitive" below-ground strategy linked to higher root N concentrations (RNC) and P concentrations (RPC), and a "collaboration" gradient probably ranging from broadleaf species with a "do-it-yourself" strategy characterized by high specific root length (SRL), to bamboo adopting an "outsourcing" strategy with thicker roots. In conclusion, key trait divergence from coexisting broadleaf species, higher phenotypic integration, and multi-dimensional opposite above- and below-ground resource strategies confer competitive advantages to moso bamboo, shedding light on the mechanistic understanding of its invasion into subtropical evergreen broadleaf forest and providing theoretical guidance for maintaining the stability of subtropical forest ecosystem.

Leaf traits are good predictors of woody species distribution after bamboo expansion in a mountain forest

The expansion of bamboo into neighboring plant communities is a common phenomenon in nature reserves. However, the role of climate factors and plant functional traits in the distribution of woody species after bamboo expansion remains unclear. Six functional traits of leaves of 180 individuals of 52 species, soil properties and air temperature were measured along an elevational gradient with different bamboo densities on Mt. Fanjingshan, Tongren City, Guizhou. Then, the direct and indirect effects of climate, soil properties, leaf traits and bamboo density on woody species distribution were detected. Our results showed that leaf traits were represented by two independent dimensions. The first dimension (PC1) is represented by the trade-off between the pairs leaf P, leaf N and leaf dry matter content, leaf C, representing nutrient use efficiency (NUE). The second dimension (PC2) was positively associated with leaf area, specific leaf area and leaf N, representing the leaf economics spectrum (LES). Climate, soil, leaf traits and bamboo density significantly explained 18% and 21% of the variance in species importance values for all species and evergreen species, respectively, but not for deciduous species. Air temperature had a positive indirect impact on the species importance value of all species via a negative direct impact on PC2, and air temperature affected the evergreen species importance value in two indirect ways: the first was to affect the species importance value positively and indirectly via PC2; the second was to affect the species importance value positively and indirectly through PC2 and PC1. However, bamboo expansion alone had no significant direct or indirect effects on species distribution. These results suggest that leaf traits are good predictors of woody species distribution after bamboo expansion in a mountain forest, and the effects of bamboo expansion are dependent on tree growth type, air temperature and leaf traits.

Not all sweetness and light: Non‐structural carbohydrate storage capacity in tree stems is decoupled from leaf but not from root economics

ABSTRACT Non‐structural carbohydrates (NSC) are considered as indicators of the balance between tree carbon sources and sinks and reflect functional strategies throughout different biomes. However, little is known about the contribution of NSC to tree economics, and in particular, whether leaf, stem and coarse root traits co‐ordinate together into a whole‐tree economics spectrum. Twenty‐four functional traits (including NSC content) were measured in leaves, stem and coarse root xylem of up to 90 angiosperm tree species in temperate, Mediterranean and tropical climates. By performing principal component analysis and standardized major axis regression, we explored the relationships between NSC and other functional traits, as well as the effects of climate and phylogeny on these relationships. Our results revealed a covariation between leaf and coarse root NSC content and leaf economic traits, whereas stem NSC content was largely decoupled from the leaf economics spectrum that was mostly driven by leaf nitrogen content and leaf mass per area. Coarse root xylem traits were closely correlated with leaf traits, while most stem xylem traits were independent from the leaf economics spectrum but covaried with coarse root traits. Trade‐offs among traits in tropical species opposed those from other climates. Evolutionary history affected relationships among certain traits but did not change overall patterns. We conclude that due to leaf habit, an extended growing season and heightened defences, tropical species form distinct conservative resource acquisition strategies. Across all climates, as the stem must provide an efficient transport route between roots and leaves, while maintaining the display of branch and leaf organs, stem xylem design and NSC storage capacity lead to a stem economics spectrum that is largely independent from the leaf spectrum, but is coupled with that of coarse roots due to anatomical continuity. Read the free Plain Language Summary for this article on the Journal blog.

Wood density and leaf size jointly predict woody plant growth rates across (but not within) species along a steep precipitation gradient

Abstract Functional traits have been proposed to define key dimensions of plant ecological strategies, but we lack consensus on whether traits can accurately predict plant demography. Despite theoretical expectations, it has been challenging to find consistent relationships between functional traits and growth. In this study, we quantified inter‐ and intraspecific trait variation (ITV) and individual growth rates of woody plants across a steep moisture gradient that varies 10‐fold in annual precipitation (350–3700 mm) in southern Chile and used a hierarchical Bayesian model to predict growth as a function of trait values. We show that large‐leaved species with lower stem tissue density exhibited the fastest growth rates, and these two traits exhibited the highest proportion of interspecific variation. Predictions of growth improved considerably (R2 of the best model increased from 0.28 to 0.49) when species‐level multiple traits and their interactions were considered. The inclusion of ITV, however, did not improve models of growth rate. We found that trait–growth rate relationships were not always consistent across levels of biological organization; relationships observed at the interspecific level did not necessarily hold at the intraspecific level. We found that the relationships between wood density or leaf size and growth were consistent in direction across the precipitation gradient, and the relationships between leaf economics traits and growth were weak and site‐specific. Synthesis. Although using more than one functional trait considerably improved growth predictions, wood density and leaf size successfully predicted growth rates across (not within) species, which is consistent with a whole‐plant carbon economy. We assert that these two traits are intimately linked and ultimately describe a continuum of plant architecture and carbon economy that covers multiple trait syndromes.

Decomposition of litter mixtures induces non-additive effects on soil priming across a riparian land use gradient

While litter traits have been used for decades to predict decomposition rates through the Leaf Economics Spectrum (LES) acquisitive to conservative trait lens, litter trait and litter mixture effects on soil carbon (C) priming effects (PE) is less known. To assess whether the LES can predict soil C PE during the decomposition of litter mixtures from complex ecosystems, a 99-day incubation experiment was conducted. The experiment involved soil and leaf litter from three Canadian riparian land uses (grasslands, deciduous agroforests, and coniferous agroforests), incubated as single plant species, and as plant species mixtures in their natural proportions. Natural abundance δ13C-isotopic analysis was used to assess the proportion of CO2 derived from leaf litter versus soil C mineralization at initial (0–21 days, stage I) and later (22–99 days, stage II) stages of decomposition. Single species positions on the LES mirrored litter-C mineralization dynamics, yet PE emissions remained harder to predict with LES traits. Nonetheless, higher PE emissions relative to litter-C mineralization were observed with litter from LES species expressing conservative traits compared to LES species expressing acquisitive traits. Leaf litter mixtures from both agroforests, expressing high leaf litter trait functional dissimilarity, resulted in synergistic, non-additive effects on soil PE. These findings contribute to our understanding of the effects of leaf litter functional traits and trait mixing on soil PE, highlighting that mixed-species litter decomposition can lead to non-additive effects on soil C dynamics in forested riparian ecosystems.

How are physiological responses to drought modulated by water relations and leaf economics’ traits in woody plants?

Species’ drought resistance is determined by a combination of multiple traits and their plastic response. However, a clear understanding of how these traits are coordinated and modulate plant responses to drought is still lacking.Here we used a water exclusion experiment on 20 Mediterranean woody species to evaluate a new framework to study plant drought responses, in which relatively constant functional traits modulate the physiological responses to a given drought exposure. In particular, we assessed how the response of stomatal conductance (Gs), leaf relative water content (RWC) and leaf water potential difference (ΔΨ) to leaf predawn water potential (Ψpd) were modulated by commonly used functional traits. The latter included hydraulic and water relations attributes such as turgor loss point in leaves (Ψtlp), vulnerability to xylem embolism in stems (Ψ50), hydraulic conductivity per unit sapwood (Ks), hydraulic conductivity per unit leaf area (Kl, hydraulic sufficiency) and Huber value (Hv), as well as specific leaf area (SLA) as a proxy for the leaf economics spectrum.Our results show that functional traits are highly coordinated, defining two main axes: the first related to drought tolerance and resource-use strategies and the second characterising the hydraulic sufficiency of leaves. These two axes, as well as many of the underlying functional traits, showed a significant interaction with Ψpd in explaining physiological responses to drought, thus modulating Gs, RWC, and ΔΨ responses. Drought-tolerant species showed a less stringent regulation of water use and leaf water potential but were more effective at regulating leaf RWC. Also, the leaf water potential at turgor loss (Ψtlp) emerged as an important trait orchestrating plant responses to drought.This study highlights that a clear separation between slow-varying traits (Ψtlp, Ψ50, Ks, Kl, Hv, SLA), physiological responses (Gs, RWC, ΔΨ) and tissue-level exposure to drought (Ψpd) improves our understanding of plant drought resistance strategies.

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

Functional trait-based approaches are extensively applied to the study of mechanisms governing community assembly along environmental gradients. These approaches have been classically based on studying differences in mean values among species, but there is increasing recognition that alternative metrics of trait distributions should be considered to decipher the mechanisms determining community assembly and species coexistence. Under this framework, the main aim of this study is to unravel the effects of environmental conditions as drivers of plant community assembly in sub-Mediterranean ecotones. We set 60 plots in six plant communities of a sub-Mediterranean forest in Central Spain, and measured key above- and belowground functional traits in 411 individuals belonging to 19 species, along with abiotic variables. We calculated community-weighted mean (CWM), skewness (CWS) and kurtosis (CWK) of three plant dimensions, and used maximum likelihood techniques to analyze how variation in these functional community traits was driven by abiotic factors. Additionally, we estimated the relative contribution of intraspecific trait variability and species turnover to variation in CWM. The first three axes of variation of the principal component analyses were related to three main plant ecological dimensions: Leaf Economics Spectrum, Root Economics Spectrum and plant hydraulic architecture, respectively. Type of community was the most important factor determining differences in the functional structure among communities, as compared to the role of abiotic variables. We found strong differences among communities in their CWMs in line with their biogeographic origin (Eurosiberian vs Mediterranean), while differences in CWS and CWK indicate different trends in the functional structure among communities and the coexistence of different functional strategies, respectively. Moreover, changes in functional composition were primarily due to intraspecific variability. We observed a high number of strategies in the forest with the different communities spreading along the acquisitive-conservative axis of resource-use, partly matching their Eurosiberian-Mediterranean nature, respectively. Intraspecific trait variability, rather than species turnover, stood as the most relevant factor when analyzing functional changes and assembly patterns among communities. Altogether, our data support the notion that ecotones are ecosystems where relatively minor environmental shifts may result in changes in plant and functional composition.

Vein hierarchy mediates the 2D relationship between leaf size and drought tolerance across subtropical forest tree species.

Previous studies have observed a 2D relationship (i.e. decoupled correlation) between leaf size (LS) and leaf economics as well as a tight correlation between leaf economics and drought tolerance. However, the underlying mechanism maintaining the relationship between LS and drought tolerance remains largely unknown. Here, we measured LS, water potential at 50% loss of hydraulic conductance, hydraulic safety margin and different orders of vein traits across 28 tree species in a subtropical forest in Southern China. We found that LS and drought tolerance were in two independent dimensions (R2=0.00, P>0.05). Primary and secondary vein traits (i.e. vein diameter and density) explained the variation of LS, with R2 ranging from 0.37 to 0.70 (all Ps<0.01), while minor vein traits accounted for the variation of leaf drought tolerance, with R2 ranging from 0.30 to 0.43 (all Ps<0.01). Our results provide insight into the 2D relationship between LS and drought tolerance and highlight the importance of vein hierarchy in plant leaf functioning.

Herbaceous species and dry forest species have more acquisitive leaf traits than woody species and wet forest species

Abstract Life forms are key to understand the changes in species composition and vegetation types in space and with succession over time. We asked how life forms from dry and wet regions differ in their leaf traits and trait hyperspace (i.e. trait variation) in early tropical forest succession on abandoned agricultural fields. We compared 324 early successional species from six life forms (herbs, grasses, vines, lianas, shrubs and trees) that occur in the first 5 years of succession on abandoned fields in Ghanaian wet and drought deciduous tropical forests. We measured 12 leaf traits that are important for carbon, water and nutrient use. A principal component analysis showed that 46% of trait variation is captured by a two‐dimensional spectrum of plant form and function: a leaf economics spectrum underpinning fast‐slow growth strategies, and a leaf size spectrum related to plant size and heat balance, which underlie species sorting along environmental gradients in space and time (during succession). Herbaceous and woody life forms had different leaf economics strategies: herbaceous species had more acquisitive trait values (e.g. higher leaf nutrient concentrations) that increase resource capture and use efficiency whereas woody species had more conservative trait values (e.g. higher leaf mass per area) that increase resource conservation. Regardless of life forms, dry forest species and deciduous species had more acquisitive trait values than wet forest species and evergreen species as they maximize their growth during the shorter growing season. The trait hyperspace was larger for woody life forms especially in wet forests. Synthesis. Herbaceous species had ‘faster’ leaf economics trait values and, hence, rapid carbon gain, explaining their success earlier in succession. In contrast, woody species had ‘slower’ resource conservation trait values that increase persistence, thus explaining their success later in succession. Deciduous species especially in a dry region had higher leaf nitrogen and phosphorus concentration to attain faster carbon gain to cope with a seasonally harsh environment. The trait hyperspace was generally smaller in the dry forest, as there are more deciduous species, and as a result, there is less variation in leaf lifespan and associated traits. Read the free Plain Language Summary for this article on the Journal blog.

Functional‐trait contrasts between terrestrial and epiphytic ferns in Taiwanese subtropical cloud forests

AbstractAimsExtensive research on the leaf economics spectrum (LES) has improved insights into functional traits and their environmental interactions. Several studies explored trait correlations in angiosperms and ferns, expanding their ecological significance. However, knowledge gaps persist, especially concerning East‐Asian ferns and the differences between terrestrial and epiphytic ferns in LES.LocationEast Asia, Northern Taiwan.MethodsData were collected along an elevation gradient (870–2130 m a.s.l.) in northern Taiwan, where we measured nine leaf traits for 47 terrestrial and 34 epiphytic ferns across 59 vegetation plots within subtropical forests. We explored trait–trait and trait–environment relationships at the species and community levels for both terrestrial and epiphytic ferns while accounting for phylogenetic constraints.ResultsEpiphytes had lower specific leaf area (SLA) and leaf nitrogen, greater trait variance and trait space than terrestrial species, suggesting they are ecologically distinct. These differences observed at species and community levels appear to emerge because epiphytes undergo stronger water and nutritional stress along the elevation gradient. In addition, three groups were detected within epiphytes reflecting their strategies for water and nutrient stress adaptation. Trait correlations largely resembled angiosperm LES patterns but were less apparent in epiphytes. SLA and leaf dry matter content (LDMC) were consistently correlated to water stress traits, which might contribute to the restricted LES trait range of both life forms in our study. Traits exhibited a strong phylogenetic signal, with marked differences between SLA and LDMC correlations in phylogenetics‐corrected vs raw data. Trait–environment relationships were similar for several water stress‐related traits across both species groups, but stronger relationships were more evident in terrestrial ferns.ConclusionsTrait patterns are not entirely equivalent for epiphytic and terrestrial species or communities and should not be extrapolated across life forms. Distantly related species with various evolutionary backgrounds could dismantle LES patterns at the species level. Strong phylogenetic constraints may influence the trait–environment response of epiphytic species.

Functional traits patterns along an altitudinal gradient in a large tropical forest region

Understanding the link between functional traits and environmental gradients can provide important information to face global change. Here, we assessed how environmental variables act on functional trait-based ecological strategies of the acquisitive-conservative continuum and dispersal syndromes in forests of the Rio Doce Basin in Brazil's Atlantic Forest. Through literature and herbarium measurements, we gathered data on ten functional traits related to light interception, leaf economics spectrum, and reproductive ability from 1912 woody species across 79 localities. Relationships between community-weighted means of functional traits and an altitudinal gradient encompassing thermal and water availability variables were quantified using generalized linear models and principal component analysis. We found that in higher altitudes are predominant vegetative conservative functional strategies (smaller leaves and petioles) and reproductive acquisitive functional strategies (smaller fruits and seeds and abiotic dispersed species). The thermal variables mainly influenced vegetative functional traits, which showed a predominantly acquisitive strategy in warmer areas, where there are more favorable and stable conditions for rapid growth and resource uptake. The water variables had a pronounced impact on reproductive functional traits, particularly in terms of dispersal patterns. Water availability tends to impact the costs of fleshy fruits and seeds with higher energy content. The patterns found for the altitudinal gradient reflected a combination of thermal and water variables, which is congruent with the aggregative role of altitude, composed of multiple physical and climatic conditions. In conclusion, the abiotic factors are operating on a large landscape scale in the plant communities, exerting influence on functional traits along the altitudinal gradient in a tropical forest region.

Phylogenetic diversity and community wide-trait means offer different insights into mechanisms regulating aboveground carbon storage

Both attributes of functional traits and phylogenetic diversity influence ecosystem functions, but which of these factors is most important is still poorly understood in natural systems. Using data from West African forests and tree savannas, we analyse how (i) phylogenetic diversity complements attributes of functional traits in explaining aboveground carbon (AGC); (ii) phylogenetic diversity relates with attributes of functional traits along gradients of phylogenetic signal; and (iii) pathways between phylogenetic diversity and attributes of functional traits relate AGC to soil and climate. Phylogenetic diversity was measured as standardised effect size of Mean Pairwise Distance (sesMPD) and Mean Nearest Taxon Distance (sesMNTD). Functional dispersion (FDis) and community weighted mean (CWM) were calculated for four traits related to leaf economics spectrum and plant life-history.Functional traits-based models explained 11 % of AGC variability. With two out of the four traits being phylogenetically conserved, incorporating phylogenetic diversity in the models increased the explained variance in AGC by 15 %. The slope of phylogenetic diversity-trait relationship was more responsive to trait conservatism for FDis than CWM. AGC was positively influenced by sesMPD and CWM of plant maximum height. In turn, CWM of plant maximum height increased with higher soil nitrogen and climate moisture, whereas sesMPD was negatively related with climate moisture. Although FDis was positively associated with sesMPD, it was not as important as sesMPD and CWM of plant maximum height in influencing and relating AGC to soil nitrogen and climate moisture.Our results suggest that phylogenetic diversity is important for AGC but does not fully reflect the functional mechanisms pertaining to community-wide trait means. The study also demonstrates the role of environment in regulating AGC, which operates through differences in community fitness driven by tall plant stature, and evolutionary processes whereby closely related species are maintained in less arid environments.

Climatic variability and plant functional traits in tropical montane cloud forest refugia along the Trans Mexican Volcanic Belt

Functional traits represent the adaptive responses of plant species to climatic changes. They are an integrative marker of the general environmental conditions at a location. Testing their patterns may help to understand how the functional traits would track these environmental changes of tropical montane cloud forests (TMCFs). These forests are characterized by the constant presence of clouds, and these are among the most threatened ecosystems by climate change worldwide. One of the main TMCF regions in Mexico is the Trans-Mexican Volcanic Belt (TMVB). This region has provided refugia during past climate-change events. We identify three current regions of distribution of TMCF in TMVB, Pacific, Center and Gulf. We used 60 years of climatic information, functional traits and plants databases. We proposed the following aims: to determine whether changes in climatic variation have occurred in the TMVB and how these changes can be related to functional trait variations for dominant tree species across the three TMCF regions, and to know the potential changes as a refuge of the TMCF of the TMVB. We found different rainfall and maximum temperature patterns among and within regions. We identified that the Pacific region forests were characterized by the lowest specific leaf area (SLA), wider leaf thickness and high leaf density, which indicates resources-conservative leaf economics and tolerance to low humidity. Center and Gulf forests were distinguished by the highest SLA, less leaf thickness, and higher leaf density values, which suggests that the leaves of dominant tree species tend to be resources-acquisitive rather than conservative-resources. Finally functional traits were associated with prevailing climatic conditions and suggested that SLA, leaf thickness and leaf density are the main functional traits that could be used to relate them to regional climate. Also, Central and Gulf regions could serve as a refuge for those species of trees demanding humidity.

Abiotic factors similarly shape the distribution of fruit, seed and leaf traits in tropical fleshy-fruited tree communities

The distribution of plant traits is related to abiotic and biotic factors, but it is unknown whether different types of plant traits respond similarly to these factors. We simultaneously studied seed, fruit and leaf traits and their associations with abiotic and biotic factors for tree communities in the tropical mountains of southern Ecuador. We measured seed, fruit, and leaf traits on 18–33 fleshy-fruited plant species and recorded the abundance for these species on nine 1-ha forest plots located at 1000, 2000, and 3000 m a.s.l. On the same plots, we recorded abiotic (soil C/N ratio, mean temperature, and annual rainfall) and biotic factors (avian fruit removal and foliar herbivory) potentially relevant for the measured traits. We conducted principal component and RLQ analyses to test for trait-environment covariation, controlling for phylogenetic relatedness and spatial autocorrelation. We identified a trade-off between (i) seed number and seed size and between (ii) the production of few costly (nitrogen-rich) vs. many cheap (carbon-rich) fruits. Likewise, leaf trait variation was primarily associated with (i) the leaf economics spectrum and (ii) leaf size. Controlling for phylogenetic and spatial covariation, seed, fruit and leaf traits were associated with abiotic and, to a lesser extent, with biotic factors. Fruit and leaf traits linked to production costs were mainly related to soil C/N ratios, whereas traits associated with the size of seeds, fruits, and leaves were related to rainfall. Our study suggests that associations between seed, fruit and leaf traits and the abiotic environment follow similar principles in tropical tree communities.

Plant defences as functional traits: A comparison across savannas differing in herbivore specialization

Abstract Top‐down and bottom‐up forces in tropical savannas have shaped the evolution of traits that enable plants to thrive in environments where soils are poor, dry seasons are long, fire is frequent, woody plants and grasses compete and herbivores range from cryptic caterpillars to elephants that topple entire trees. African savannas and the South American cerrado have similar climates and fire regimes, but differ in the presence of large mammal herbivores, which are mostly extinct in the cerrado. These biomes offer an instructive comparison to understand how plant defence traits evolved in response to differential herbivore pressure. Within Africa, mammalian herbivore pressure also differs across savannas, being lower in the miombo relative to more open, mixed savannas. The dominance of specialist insect herbivores in the cerrado, relative to the more generalist mammalian herbivores in Africa, suggests that defence traits will differ between savannas in accordance with herbivore identity and pressure. Wood is densest in mixed African savannas, as expected because large mammals often damage trees. Specific leaf area, related to palatability, is higher in mixed African savannas and the cerrado relative to the miombo, while leaf N is surprisingly higher in miombo species. Ant mutualists are important defences in mixed African savannas and the cerrado. Defensive chemistry has received less attention in the trait literature. Foliar phenolics, the most commonly studied chemical defences in savannas, vary in their efficacy. New analyses isolating specific compounds are informative as is the evaluation of phytochemical diversity as a defence. There are indications that phytochemical defences are more diverse in the cerrado, which may be related to greater specialization of cerrado herbivores. Synthesis. The dominance of specialist insect herbivores in the cerrado, relative to generalist mammalian herbivores in Africa, selected for different plant defence traits, contributing to the separation of species along the leaf economics spectrum and demonstrating the importance of plant defences as plant functional traits. African savanna species seem to follow a more acquisitive strategy, followed by miombo species. Cerrado species appear to follow a more conservative strategy with greater investments in tough leaves and chemical defences.

Analysis of leaf economics sheds light on the heterophylly and ecological strategies of Paleocene Ginkgo leaves from Henan Province, China

The palaeoecology of Ginkgo through deep time, including its ecophysiology and heterophylly, remains poorly understood due to the limitation of quantitative methods. In this paper, we report well-preserved leaves of Ginkgo henanensis sp. nov. from the Paleocene Dazhang Formation of Luanchuan, Henan Province, China. Our understanding of the ecophysiology and heterophylly of the genus has been improved by the discovery. These fossils are distinguished by heterophyllous leaves that can range in morphology from bilobed to multi-lobed forms. Thus, unlike other Cenozoic Ginkgo with entire-margined leaves, this is the first well-established Cenozoic taxon that has exclusively lobed leaves similar to Mesozoic-type ginkgos. A useful leaf ecophysiological functional trait that offers quantitative insights into morphological heterophylly and the mechanism of leaf shape selection is the dry leaf mass per area (LMA) of Ginkgo. Leaf shape changes, including the evolution of heterophylly, are linked to functional adaptation. There are two groups of LMAs for four fossil G. henanensis specimens: 120.9 g/m2 to 131.3 g/m2, and 184.5 g/m2 to 187.4 g/m2. The results of the reconstructed fossil LMAs, which serve as quantitative evidence of G. henanensis' heterophylly, also point to the existence of various leaf survival strategies within G. henanensis. Additionally, both groups of G. henanensis have LMAs that are higher than those of extant Ginkgo biloba, indicating that this species has a slower return ecological strategy than its current equivalent. This strategy may have helped to decrease the rate of nutrient cycling, which supported Ginkgo to thrive in a wider variety of ecological niches in the Paleocene than it does today. These findings close a knowledge gap in the evolution of Ginkgo.

Leaf nitrogen affects photosynthesis and water use efficiency similarly in nitrogen‐fixing and non‐fixing trees

Abstract Nitrogen (N)‐fixing trees are thought to break a basic rule of leaf economics: higher leaf N concentrations do not translate into higher rates of carbon assimilation. Understanding how leaf N affects photosynthesis and water use efficiency (WUE) in this ecologically important group is critical. We grew six N‐fixing and four non‐fixing tree species for 4–5 years at four fertilization treatments in field experiments in temperate and tropical regions to assess how functional type (N fixer vs. non‐fixer) and N limitation affected leaf N and how leaf N affected light‐saturated photosynthesis (Asat), stomatal conductance (gsw) and WUE (WUEi and δ13C). Asat, WUEi and δ13C, but not gsw, increased with higher leaf N. Surprisingly, N‐fixing and non‐fixing trees displayed similar scaling between leaf N and these physiological variables, and this finding was supported by reanalysis of a global dataset. N fixers generally had higher leaf N than non‐fixers, even when non‐fixers were not N‐limited at the leaf level. Leaf‐level N limitation did not alter the relationship of Asat, gsw, WUEi and δ13C with leaf N, although it did affect the photosynthetic N use efficiency. Higher WUE was associated with higher productivity, whereas higher Asat was not. Synthesis: The ecological success of N‐fixing trees depends on the effect of leaf N on carbon gain and water loss. Using a field fertilization experiment and reanalysis of a global dataset, we show that high leaf‐level photosynthesis and WUE in N fixers stems from their higher average leaf N, rather than a difference between N fixers and non‐fixers in the scaling of photosynthesis and WUE with leaf N. By clarifying the mechanism by which N fixers achieve and benefit from high WUE, our results further the understanding of global N fixer distributions.