Leaf Economics Research Articles

Inter- and intraspecific variation in leaf economic traits in wheat and maize

Leaf Economics Spectrum (LES) trait variation underpins multiple agroecological processes and many prominent crop yield models. While there are numerous independent studies assessing trait variation in crops, to date there have been no comprehensive assessments of intraspecific trait variation (ITV) in LES traits for wheat and maize: the world's most widespread crops. Using trait databases and peer-reviewed literature, we compiled over 700 records of specific leaf area (SLA), maximum photosynthetic rates (Amax) and leaf nitrogen (N) concentrations, for wheat and maize. We evaluated intraspecific LES trait variation, and intraspecific trait-environment relationships. While wheat and maize occupy the upper 90th percentile of LES trait values observed across a global species pool, ITV ranged widely across the LES in wheat and maize. Fertilization treatments had strong impacts on leaf N, while plant developmental stage (here standardized as the number of days since planting) had strong impacts on Amax; days since planting, N fertilization and irrigation all influenced SLA. When controlling for these factors, intraspecific responses to temperature and precipitation explained 39.4 and 43.7 % of the variation in Amax and SLA, respectively, but only 5.4 % of the variation in leaf N. Despite a long history of domestication in these species, ITV in wheat and maize among and within cultivars remains large. Intraspecific trait variation is a critical consideration to refine regional to global models of agroecosystem structure, function and food security. Considerable opportunities and benefits exist for consolidating a crop trait database for a wider range of domesticated plant species.

Losses of leaf area owing to abiotic stress along the leaf economics spectrum: implications for carbon gain at the branch level

Key message The differences in premature loss of leaf area between coexisting tree species have significant impacts on the duration of the functional photosynthetic machinery, therefore, this aspect should be included in the predictive models of carbon sequestration capacity.

Contrasting patterns of leaf trait variation among and within species during tropical dry forest succession in Costa Rica

A coordinated response to environmental drivers amongst individual functional traits is central to the plant strategy concept. However, whether the trait co-ordination observed at the global scale occurs at other ecological scales (especially within species) remains an open question. Here, for sapling communities of two tropical dry forest types in Costa Rica, we show large differences amongst traits in the relative contribution of species turnover and intraspecific variation to their directional changes in response to environmental changes along a successional gradient. We studied the response of functional traits associated with the leaf economics spectrum and drought tolerance using intensive sampling to analyse inter- and intra-specific responses to environmental changes and ontogeny. Although the overall functional composition of the sapling communities changed during succession more through species turnover than through intraspecific trait variation, their relative contributions differed greatly amongst traits. For instance, community mean specific leaf area changed mostly due to intraspecific variation. Traits of the leaf economics spectrum showed decoupled responses to environmental drivers and ontogeny. These findings emphasise how divergent ecological mechanisms combine to cause great differences in changes of individual functional traits over environmental gradients and ecological scales.

Decoupled dimensions of leaf economic and anti-herbivore defense strategies in a tropical canopy tree community.

Trade-offs among plant functional traits indicate diversity in plant strategies of growth and survival. The leaf economics spectrum (LES) reflects a trade-off between short-term carbon gain and long-term leaf persistence. A related trade-off, between foliar growth and anti-herbivore defense, occurs among plants growing in contrasting resource regimes, but it is unclear whether this trade-off is maintained within plant communities, where resource gradients are minimized. The LES and the growth-defense trade-off involve related traits, but the extent to which these trade-off dimensions are correlated is poorly understood. We assessed the relationship between leaf economic and anti-herbivore defense traits among sunlit foliage of 345 canopy trees in 83 species on Barro Colorado Island, Panama. We quantified ten traits related to resource allocation and defense, and identified patterns of trait co-variation using multivariate ordination. We tested whether traits and ordination axes were correlated with patterns of phylogenetic relatedness, juvenile demographic trade-offs, or topo-edaphic variation. Two independent axes described~60% of the variation among canopy trees. Axis 1 revealed a trade-off between leaf nutritional and structural investment, consistent with the LES. Physical defense traits were largely oriented along this axis. Axis 2 revealed a trade-off between investments in phenolic defenses versus other foliar defenses, which we term the leaf defense spectrum. Phylogenetic relationships and topo-edaphic variation largely did not explain trait co-variation. Our results suggest that some trade-offs among the growth and defense traits of outer-canopy trees may be captured by the LES, while others may occur along additional resource allocation dimensions.

Hydraulic and Leaf Economics of Woody Plants of the Tropical Environment

Leaf photosynthesis and hydraulic traits are closely related to the maintenance of the plants, especially in tropical environments. There is scarce information about the xylem structure and hydraulic efficiency in tropical species, mainly considering the leaf. Environmental changes influence the species performance, conditioning differences of anatomical traits and functional efficiency of xylem cells related to the water flow inside the plant. The hydraulic conductivity and the theoretical leaf-specific conductivity allow estimating the xylem cells flow and inform about the efficiency of the water transport inside the plant. The relation among leaf biometry and anatomic/hydraulic characteristics of the xylem cells of leaves with different stages of growth, of five woody species from the tropical environment, was evaluated . Differences among leaves of different ages and species indicate to be responsible for the anatomical traits variations. The xylem hydraulic traits indicate a greater or smaller efficiency in leaves water transport and are related to the species. The hydraulic and structural differences indicate an adaptation to higher efficiency in water transport in leaves related to the prevailing environmental conditions during the leaf development.

Leaf carbon and oxygen isotopes are coordinated with the leaf economics spectrum in Mediterranean rangeland species

Abstract The leaf economics spectrum (LES) describes covariation in traits relevant to carbon and nutrient economics across plant species, but much less is known about the relationship between the LES and leaf water economy. We propose an approach combining the measurement of two leaf traits related to water‐use economy, leaf carbon (δ13C) and oxygen (δ18O) isotopic composition, and the measurement of leaf morphological and nutrient traits to investigate the link between leaf carbon and nutrient economics and water use. We tested the relationships between leaf traits linked to carbon and nutrient use within the LES and water‐use traits using leaf δ18O as a proxy of stomatal conductance (gs) and δ13C as a proxy of intrinsic water‐use efficiency (WUEi) across 15 Mediterranean rangeland species grown in an irrigated common garden and in a natural rangeland in Southern France. The target species spanned a wide range of variation in leaf morphological and nutrient trait values and a wide range of leaf δ18O and δ13C values. Principal component analysis revealed multiple associations among leaf morphology, nutrients and isotopic composition, with the first axis alone explaining 56.0% of the total variation across species. Leaf δ18O and δ13C covaried with leaf morphology and leaf nutrient concentrations along a single resource‐use axis. Species with high leaf δ18O and δ13C (low gs and high WUEi) exhibited a resource‐conservative strategy (high leaf dry matter content, low leaf N, P and K), whereas species with low leaf δ18O and δ13C (high gs and low WUEi) showed a more resource‐acquisitive strategy (high specific leaf area and leaf N, P and K). These leaf trait syndromes and resource‐use strategies were strongly conserved across sites with contrasting environmental conditions, indicating that foliar δ18O and δ13C can be included as an integral part of the LES for this set of rangeland species. Overall, the data suggest a tight coupling and coordination between water, carbon and nutrient‐use strategies across herbaceous plant species. A dual δ18O and δ13C isotope approach combined with LES trait measurements is a promising tool to more comprehensively assess the diversity of resource‐use strategies among coexisting plant species. A plain language summary is available for this article.

Being John Harper: Using evolutionary ideas to improve understanding of global patterns in plant traits

Abstract This review summarizes current understanding of five key plant traits: seed mass, plant height, wood density, leaf mass per unit area and leaf size, emphasizing ways in which our understanding of large‐scale patterns in plant traits have improved over the last two decades. Notable advances include: (1) large‐seeded species have greater seed dispersal distances than do small‐seeded species, (2) leaf mass per unit area is not strongly or consistently related to plant traits outside the leaf economics spectrum, or to broad gradients in environmental conditions, and (3) fleshy fruit could not have first evolved for seed dispersal, as the first fleshy fruit appeared millions of years before the first potential seed dispersers. While quantifying large‐scale patterns in plant traits has yielded many important discoveries, it is clear that the next major leap in understanding will not come from simply including ever more variables in our analyses. I suggest that we build upon Harper's “Darwinian approach to plant ecology” and apply evolutionary ideas to large‐scale trait ecology. For example, quantifying trait impacts on lifetime fitness rather than on particular stages of plant regeneration can allow us to understand the coordination between seemingly disparate traits. I use this approach to bring seed mass and plant height together as integrated parts of a species’ life‐history spectrum. I then point out problems associated with the implicit assumption that selection acts on species’ mean trait values and show how considering the way selection acts can improve our understanding of the effects of climate on plant traits. A goal for the future is to quantify the full suite of biotic and abiotic factors that shape plant strategy in complex, real‐world situations. Synthesis. Enormous data availability and ever more powerful computational and statistical tools have given ecologists unprecedented power to quantify large‐scale patterns in plant ecology. However, there is a limit to how far big data alone can take us. The time is ripe for a new generation of hypotheses and ecological theory built on strong evolutionary foundations. Let the creativity begin!

Relationships between leaf mass per area and nutrient concentrations in 98 Mediterranean woody species are determined by phylogeny, habitat and leaf habit

This study reinforces the existence of the leaf economics spectrum in Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as main drivers of variability in structural and nutrient traits of leaves. Leaf structural and nutrient traits are key attributes of plant ecological strategies, as these traits are related to resource-use strategies and plant growth. However, leaf structure and nutrient composition can vary among different habitats, leaf habits or phylogenetic groups. In this study, we measured 13 leaf traits (one structural—leaf mass per area, LMA—and 12 nutrient traits) in 98 Mediterranean woody species growing over a wide range of environmental conditions, with the final aim of discerning the main causes of leaf trait variability. The variance decomposition results show that phylogeny, leaf habit and habitat type affected in several ways the structural and nutrient traits studied. Leaf nutrient concentrations are strongly positively correlated amongst themselves, and negatively correlated with LMA, in accordance with the “leaf economics spectrum”. We found that leaf habit and phylogeny were important causes of variation in LMA and in a broad number of leaf nutrients (i.e., C, N, Mg, S, K), while other micronutrients seemed to be more dependent on the environment (i.e., Cu and Mn). In summary, our study reinforces the existence of the leaf economics spectrum in a broad pool of Mediterranean woody species, and demonstrates the strong influence of phylogeny, leaf habit and environmental context as the main drivers of variability in some leaf structural and nutrient traits.

The relationships between leaf economics and hydraulic traits of woody plants depend on water availability

Leaf economics and hydraulic traits are simultaneously involved in the process of trading water for CO2, but the relationships between these two suites of traits remain ambiguous. Recently, Li et al. (2015) reported that leaf economics and hydraulic traits were decoupled in five tropical-subtropical forests in China.We tested the hypothesis that the relationships between economics and hydraulic traits may depend on water availability. We analysed five leaf economics traits, four hydraulic traits and anatomical structures of 47 woody species on the Loess Plateau with poor water availability and compared those data with Li et al. (2015) obtained in tropical-subtropical regions with adequate water.The results showed that plants on the Loess Plateau tend to have higher leaf tissue density (TD), leaf nitrogen concentrations and venation density (VD) and lower stomatal guard cell length (SL) and maximum stomatal conductance to water vapour (gwmax). VD showed positive correlations with leaf nitrogen concentrations, palisade tissue thickness (PT) and ratio of palisade tissue thickness to spongy tissue thickness (PT/ST). Principal component analysis (PCA) showed a result opposite from those of tropical-subtropical regions: leaf economics and hydraulic traits were coupled on the Loess Plateau.A stable correlation between these two suites of traits may be more cost-effective on the Loess Plateau, where water availability is poor. The correlation of leaf economics and hydraulic traits may be a type of adaptation mechanism in arid conditions.

Farmer perception and utilization of leaf functional traits in managing agroecosystems

Abstract Using knowledge of leaf functional traits, such as those forming the leaf economics spectrum (LES), to understand plant responses to environmental change is well‐established and now being more widely applied to agroecosystems. Yet, little is known about how farm managers invoke leaf functional traits to inform management decisions. The objectives of this research were to (1) evaluate whether farmers use knowledge of intraspecific trait variation (ITV) in LES traits (or trait proxies) of target crops as response indicators of management conditions; (2) determine whether LES trait values are ranked consistently among multiple farmers along a “Farmer Leaf Economics Spectrum” (FES); (3) evaluate how a FES corresponds to the LES; and (4) identify the farmer and farm attributes that best predict the agreement between the FES and the LES. We collaborated with coffee (Coffea arabica) farmers in the Turrialba Valley, Costa Rica. We used a visual elicitation tool of fresh leaves along an intraspecific spectrum of leaf size, leaf thickness and leaf colour (as a proxy for leaf nutrients); respondents were asked to rank leaves in response to shade and nutrient scenarios as well as yield potential. On‐farm biophysical data, management practices and socio‐economic attributes were also collected. The majority of farmers demonstrated a developed system of utilizing coffee leaf and whole‐plant ITV as indicators of management practices. Farmers managing smaller farms tended to more commonly acknowledge ITV in LES chemical–morphological traits, as compared to those managing large farms. The agreement between a respondent‐identified ranking of leaf thickness ITV as a function of light environment and an empirically defined thickness‐to‐light ranking was partially explained by farmers’ physical engagement with plants. Synthesis and applications. In scientific literature, analyses of crop intraspecific trait variation have provided important insights into the mechanistic bases of multiple key agroecological processes. We demonstrate that farmers use crop leaf trait variation as an indicator to both evaluate management prescriptions and to initiate management actions including shade‐tree species selection and abundance, crop‐ and shade‐tree pruning regimes and fertilization treatments. These findings signify that functional traits represent a key nexus between scientific and local knowledge.

Can Leaf Spectroscopy Predict Leaf and Forest Traits Along a Peruvian Tropical Forest Elevation Gradient?

AbstractHigh‐resolution spectroscopy can be used to measure leaf chemical and structural traits. Such leaf traits are often highly correlated to other traits, such as photosynthesis, through the leaf economics spectrum. We measured VNIR (visible‐near infrared) leaf reflectance (400–1,075 nm) of sunlit and shaded leaves in ~150 dominant species across ten, 1 ha plots along a 3,300 m elevation gradient in Peru (on 4,284 individual leaves). We used partial least squares (PLS) regression to compare leaf reflectance to chemical traits, such as nitrogen and phosphorus, structural traits, including leaf mass per area (LMA), branch wood density and leaf venation, and “higher‐level” traits such as leaf photosynthetic capacity, leaf water repellency, and woody growth rates. Empirical models using leaf reflectance predicted leaf N and LMA (r2 > 30% and %RMSE < 30%), weakly predicted leaf venation, photosynthesis, and branch density (r2between 10 and 35% and %RMSE between 10% and 65%), and did not predict leaf water repellency or woody growth rates (r2<5%). Prediction of higher‐level traits such as photosynthesis and branch density is likely due to these traits correlations with LMA, a trait readily predicted with leaf spectroscopy.

Shoot growth of woody trees and shrubs is predicted by maximum plant height and associated traits

Abstract The rate of elongation and thickening of individual branches (shoots) varies across plant species. This variation is important for the outcome of competition and other plant–plant interactions. Here, we compared rates of shoot growth across 44 species from tropical, warm temperate and cool temperate forests of eastern Australia. Shoot growth rate was found to correlate with a suite of traits including the potential height of the species, xylem‐specific conductivity, leaf size, leaf area per xylem cross‐section (LA/XA), twig diameter (at 40 cm length), wood density and modulus of elasticity. Within this suite of traits, maximum plant height was the clearest correlate of growth rates, explaining 50%–67% of the variation in growth overall (p < .0001), and 23%–32% of the variation (p < .05) in growth when holding the influence of the other traits constant. Structural equation models suggest that traits associated with “hydraulics,” “biomechanics” and the “leaf economics spectrum” represent three clearly separated axes of variation, with the hydraulic axis exhibiting the strongest alignment with height and largest independent contribution to growth (in the case of branch thickening). However, most of the capacity of these axes to predict growth was also associated with maximum height, presumably reflecting coordinated selection on multiple traits that together influence life histories. Growth rates were not strongly correlated with leaf nitrogen or leaf mass per unit leaf area. Correlations between growth and maximum height arose both across latitude (47%, p < .0001) and from within‐site differences between species (30%, p < .0001). Covariation between growth and maximum height was driven in part by variation in irradiance across sites as well as among canopy positions within sites (23%, p < .0001). A significant fraction of this shared variation was independent of irradiance (45%, p < .0001), reflecting intrinsic differences across species and sites. A plain language summary is available for this article.

Three Key Sub-leaf Modules and the Diversity of Leaf Designs.

Earth harbors a highly diverse array of plant leaf forms. A well-known pattern linking diverse leaf forms with their photosynthetic function across species is the global leaf economics spectrum (LES). However, within homogeneous plant functional groups such as tropical woody angiosperms or temperate deciduous woody angiosperms, many species can share a similar position in the LES but differ in other vital leaf traits, and thus function differently under the given suite of environmental drivers. How diverse leaves differentiate from each other has yet to be fully explained. Here, we propose a new perspective for linking leaf structure and function by arguing that a leaf may be divided into three key sub-modules, the light capture module, the water-nutrient flow module and the gas exchange module. Each module consists of a set of leaf tissues corresponding to a certain resource acquisition function, and the combination and configuration of different modules may differ depending on overall leaf functioning in a given environment. This modularized-leaf perspective differs from the whole-leaf perspective used in leaf economics theory and may serve as a valuable tool for tracing the evolution of leaf form and function. This perspective also implies that the evolutionary direction of various leaf designs is not to optimize a single critical trait, but to optimize the combination of different traits to better adapt to the historical and current environments. Future studies examining how different modules are synchronized for overall leaf functioning should offer critical insights into the diversity of leaf designs worldwide.

Stem photosynthesis and hydraulics are coordinated in desert plant species.

Coordination between stem photosynthesis and hydraulics in green-stemmed desert plants is important for understanding the physiology of stem photosynthesis and possible drought responses. Plants with photosynthetic stems have extra carbon gain that can help cope with the detrimental effects of drought. We studied photosynthetic, hydraulic and functional traits of 11 plant species with photosynthetic stems from three California desert locations. We compared relationships among traits between wet and dry seasons to test the effect of seasonality on these relationships. Finally, we compared stem trait relationships with analogous relationships in the leaf economics spectrum. We found that photosynthetic and hydraulic traits are coordinated in photosynthetic stems. The slope or intercept of all trait relationships was mediated by seasonality. The relationship between mass-based stem photosynthetic CO2 assimilation rate (Amass ) and specific stem area (SSA; stem surface area to dry mass ratio) was statistically indistinguishable from the leaf economics spectrum. Our results indicate that photosynthetic stems behave like leaves in the coordination of multiple traits related to carbon gain, water movement and water loss. Because of the similarity of the stem Amass -SSA relationship to the leaf Amass -specific leaf area relationship, we suggest the existence of a photosynthetic stem economic spectrum.

Trade-offs between seed and leaf size (seed-phytomer-leaf theory): functional glue linking regenerative with life history strategies … and taxonomy with ecology?

While the 'worldwide leaf economics spectrum' (Wright IJ, Reich PB, Westoby M, et al. 2004. The worldwide leaf economics spectrum. Nature : 821-827) defines mineral nutrient relationships in plants, no unifying functional consensus links size attributes. Here, the focus is upon leaf size, a much-studied plant trait that scales positively with habitat quality and components of plant size. The objective is to show that this wide range of relationships is explicable in terms of a seed-phytomer-leaf (SPL) theoretical model defining leaf size in terms of trade-offs involving the size, growth rate and number of the building blocks (phytomers) of which the young shoot is constructed. Functional data for 2400+ species and English and Spanish vegetation surveys were used to explore interrelationships between leaf area, leaf width, canopy height, seed mass and leaf dry matter content (LDMC). Leaf area was a consistent function of canopy height, LDMC and seed mass. Additionally, size traits are partially uncoupled. First, broad laminas help confer competitive exclusion while morphologically large leaves can, through dissection, be functionally small. Secondly, leaf size scales positively with plant size but many of the largest-leaved species are of medium height with basally supported leaves. Thirdly, photosynthetic stems may represent a functionally viable alternative to 'small seeds + large leaves' in disturbed, fertile habitats and 'large seeds + small leaves' in infertile ones. Although key elements defining the juvenile growth phase remain unmeasured, our results broadly support SPL theory in that phytometer and leaf size are a product of the size of the initial shoot meristem (≅seed mass) and the duration and quality of juvenile growth. These allometrically constrained traits combine to confer ecological specialization on individual species. Equally, they appear conservatively expressed within major taxa. Thus, 'evolutionary canalization' sensu Stebbins (Stebbins GL. 1974. Flowering plants: evolution above the species level . Cambridge, MA: Belknap Press) is perhaps associated with both seed and leaf development, and major taxa appear routinely specialized with respect to ecologically important size-related traits.

Palaeo leaf economics reveal a shift in ecosystem function associated with the end-Triassic mass extinction event.

Climate change is likely to have altered the ecological functioning of past ecosystems, and is likely to alter functioning in the future; however, the magnitude and direction of such changes are difficult to predict. Here we use a deep-time case study to evaluate the impact of a well-constrained CO2-induced global warming event on the ecological functioning of dominant plant communities. We use leaf mass per area (LMA), a widely used trait in modern plant ecology, to infer the palaeoecological strategy of fossil plant taxa. We show that palaeo-LMA can be inferred from fossil leaf cuticles based on a tight relationship between LMA and cuticle thickness observed among extant gymnosperms. Application of this new palaeo-LMA proxy to fossil gymnosperms from East Greenland reveals significant shifts in the dominant ecological strategies of vegetation found across the Triassic-Jurassic transition. Late Triassic forests, dominated by low-LMA taxa with inferred high transpiration rates and short leaf lifespans, were replaced in the Early Jurassic by forests dominated by high-LMA taxa that were likely to have slower metabolic rates. We suggest that extreme CO2-induced global warming selected for taxa with high LMA associated with a stress-tolerant strategy and that adaptive plasticity in leaf functional traits such as LMA contributed to post-warming ecological success.

Intraspecific Trait Variation and Coordination: Root and Leaf Economics Spectra in Coffee across Environmental Gradients.

Hypotheses on the existence of a universal “Root Economics Spectrum” (RES) have received arguably the least attention of all trait spectra, despite the key role root trait variation plays in resource acquisition potential. There is growing interest in quantifying intraspecific trait variation (ITV) in plants, but there are few studies evaluating (i) the existence of an intraspecific RES within a plant species, or (ii) how a RES may be coordinated with other trait spectra within species, such as a leaf economics spectrum (LES). Using Coffea arabica (Rubiaceae) as a model species, we measured seven morphological and chemical traits of intact lateral roots, which were paired with information on four key LES traits. Field collections were completed across four nested levels of biological organization. The intraspecific trait coefficient of variation (cv) ranged from 25 to 87% with root diameter and specific root tip density showing the lowest and highest cv, respectively. Between 27 and 68% of root ITV was explained by site identity alone for five of the seven traits measured. A single principal component explained 56.2% of root trait covariation, with plants falling along a RES from resource acquiring to conserving traits. Multiple factor analysis revealed significant orthogonal relationships between root and leaf spectra. RES traits were strongly orthogonal with respect to LES traits, suggesting these traits vary independently from one another in response to environmental cues. This study provides among the first evidence that plants from the same species differentiate from one another along an intraspecific RES. We find that in one of the world’s most widely cultivated crops, an intraspecific RES is orthogonal to an intraspecific LES, indicating that above and belowground responses of plants to managed (or natural) environmental gradients are likely to occur independently from one another.

Economic trade-offs of hydrophytes and neighbouring terrestrial herbaceous plants based on plant functional traits

This study aims to compare variation and co-variation of leaf, stem and root economic traits between hydrophytes and sympatric terrestrial plants, and further to explore the ecological strategies of the aquatic plants. We collected data for 145 species from 38 sites in Shaanxi Province, including 60 aquatic species and 85 terrestrial species (112 genera and 48 families). Fifteen plant economic traits of these species were measured, including specific leaf area, dry matter content and C, N, P stoichiometry in leaves, stems and roots. Multivariate analysis was employed to uncover the differences in economic trade-offs between aquatic and terrestrial plants. The results indicated that: (1) Hydrophytes exhibited much higher specific leaf area and lower mean leaf dry matter content, stem dry matter content, root dry matter content, stem carbon content and root carbon content compared with that of terrestrial plants in order to adapt to the aquatic environment, that is, there were differences in mean traits about the economic trade-offs faced by hydrophytes and terrestrial plants. (2) The leaf economic spectrum of aquatic plants in this region coincided with the worldwide leaf economics spectrum, while hydrophytes are located at the extreme of thin leaves which is conducive to rapid acquisition of resources. (3) Aquatic and terrestrial species can be discriminated by few functional traits related to resource acquisition and support tissues. (4) Aquatic and terrestrial plants differed in bivariate correlations between certain economic traits (standardized major axis analysis), indicating differences in plant strategies.

Coordination of morphological and physiological traits in naturally recruited Abies alba Mill. saplings: insights from a structural equation modeling approach

Apical dominance ratio (ADR), reported as a suitable indicator for the growth and development of Abies alba , is concurrently determined by morphological and functional plant traits. Structural equation modeling (SEM) proved here to be an effective multivariate technique to represent the contribution of different variables in explaining ADR variability. During the natural recruitment of understory tree saplings, the light environment and competition among individuals may change drastically as well as their growth patterns. To cope with this, saplings have a remarkable ability to accordingly modify their physiology and morphology. Therefore, understanding the ecological significance of plant structural patterns requires an integrated view of morphological, architectural, and physiological attributes of plants. Here, we applied a SEM approach to understand the mechanisms influencing the ADR, recently reported as suitable indicator of the growth conditions favoring silver fir (Abies alba Mill.) natural regeneration in Mediterranean areas. A series of plant traits (e.g., root-collar diameter, leaf mass per area, and isotope composition) were combined into two main latent variables, namely Morphology and Physiology, to account for their relative contribution in explaining the ADR variability. Our results underline the importance of variables accounting for the photosynthetic capacity and leaf economics in determining ADR; among them, leaf mass per area (LMA) emerged as an important driving variable. SEM proved to be an effective multivariate technique to represent the coordination of different morphological and functional variables in explaining ADR variability in silver fir.

Coordination and Determinants of Leaf Community Economics Spectrum for Canopy Trees and Shrubs in a Temperate Forest in Northeastern China

Upscaling the leaf economics spectrum (LES) from the species level to community level is an important step to understand how assemblages are constructed based on functional traits and how these coordinated traits for a community respond to the environmental gradients and climate change. In a 9-ha temperate forest dynamics plot located in northeastern China, we collected four LES traits and three other leaf traits from 28 tree species and 13 shrub species. We then related the LES traits at the community level to topographical and soil factors. We observed that the coordination of LES at the community level was stronger than at the species level. Soil nutrients were the primary drivers of distribution of leaf community economics spectrum with acquisition strategy communities in the resource-rich locations. We also observed that different environmental factors affected the distributions of leaf community economics spectrums for trees and shrubs. Our results provided novel evidence for the existence of leaf community economics spectrum in the continental monsoon climate zone. Both abiotic filtering and niche differentiation determined their distributions across different growth forms at the local spatial scale.