Changes In Specific Leaf Area Research Articles

Native herbivore browsing alters plant physical and chemical traits in a eucalypt forest understory

AbstractMacropods exhibit selective herbivory on plant traits within and between species and hence can alter plant trait variation. In this study, we asked what are the effects of macropod herbivory on intraspecific variation in plant traits of forest understory species? We tested the effects of herbivory by macropods on eight plant traits, in nine understory species using a herbivore exclusion experiment. Generalized linear mixed models were used to test for differences between herbivory treatments in trait means as well as variation within species and at the community level. Macropod herbivory resulted in differences in either the mean trait value or trait variance within a species for seven of the eight tested plant traits. Macropod exclusion resulted in larger dimensions of size for most species, as well as changes in specific leaf area, moisture content, and carbon content of leaves. Further, community‐weighted means of specific leaf area, moisture content, and leaf nitrogen were lower in the presence of macropods. Plant trait variance was altered for three of the seven community‐weighted traits. This study demonstrates a mechanism through which macropods can drive changes in the traits of understory plant species. Plant traits have been linked to various larger scale ecological processes including ecosystem flammability, nutrient cycling, response to global change, and habitat suitability for other organisms. Therefore, herbivore‐induced changes in plant trait variation and community composition could have important flow‐on effects for other environmental processes and hence should be considered in management decisions regarding fire‐prone ecosystems.

Distinct trait syndromes and plasticity maintain similar performance between seedlings populations of the riparian tree species Populus nigra L.

Riparian forests remain largely understudied in the context of climate change in comparison to other forest ecosystems although they serve multiple socio-ecological functions. We evaluated local adaptation and adaptive potential in Populus nigra L., an emblematic tree species of European riparian forests. We set up a reciprocal transplant experiment and measured 17 structural and functional traits among 10 progenies of two genetically differentiated populations. The populations originated from two separate watersheds differing in climate conditions and a total of 1200 seedlings were grown in 1-m3 mesocosms at both sites for one growing season. Traits measured were related to growth, leaf physiology and xylem water transport. The populations showed similar biomass suggesting no local adaptation for overall performance but displayed distinct trait syndromes and plastic abilities. The southern population primarily adjusted through changes in allocation and leaf water-use efficiency while the northern population primarily adjusted through changes in specific leaf area. Genetic variation within populations was most of the times equal or larger than between populations. This combined with the generally moderate to high heritability values and the observed plasticity suggested significant adaptive potential. Altogether, our findings reveal that although evolution may not lead to obvious differentiation between populations in global performance, integrated multi-trait approaches are highly valuable to shed light on how evolution may shape distinct underlying functional strategies among populations resulting in a similar outcome.

Plasticity of wood and leaf traits related to hydraulic efficiency and safety is linked to evaporative demand and not soil moisture in rubber (Hevea brasiliensis).

The predicted increase of drought intensity in Southeast Asia has raised concern about the sustainability of rubber (Hevea brasiliensis) cultivation. In order to quantify the degree of phenotypic plasticity in this important tree crop species, we analysed a set of wood and leaf traits related to hydraulic safety and efficiency in PB260 clones from eight small-holder plantations in Jambi province, Indonesia, representing a gradient in local microclimatic and edaphic conditions. Across plots, branch embolism resistance (P50) ranged from -2.14 to -2.58MPa. P50 and P88 values declined, and the hydraulic safety margin increased, with an increase in mean annual vapour pressure deficit (VPD). Among leaf traits, only changes in specific leaf area were related to differences in evaporative demand. These variations of hydraulic trait values were not related to soil moisture levels. We did not find a trade-off between hydraulic safety and efficiency, but vessel density emerged as a major trait associated with both safety and efficiency. Vessel density, and not vessel diameter, was closely related to P50 and P88, as well as to specific hydraulic conductivity, the lumen-to-sapwood area ratio and the vessel grouping index. In conclusion, our results demonstrate some degree of phenotypic plasticity in wood traits related to hydraulic safety in this tropical tree species, but only in response to local changes in evaporative demand and not soil moisture. Given that VPD may increasingly limit plant growth in a warmer world, our results provide evidence of hydraulic traits changes in response to a rising evaporative demand.

Leaf economics in a three‐dimensional environment: Testing leaf trait responses in vascular epiphytes to land use, climate and tree zone

Abstract The study of functional traits offers predictive power for community ecology. Particularly in cases where individual species are difficult to study, known properties of trait spectra, such as the leaf economics spectrum (LES), and trait–environment relationships can provide crucial generalizable information that can contribute to forecasts of distributional shifts in response to the abiotic effects of climate and land use changes. Vascular epiphytes have been proposed as indicators of environmental change, but we know little about the ecology of most species. Key functional trait assumptions are based on terrestrial plants; testing these in epiphytes verifies their universality and will inform applying functional traits in predicting epiphyte responses to climate and land use change. In this study, we use functional traits from 37 vascular epiphyte species from forests and shade coffee farms at two sites in northern Nicaragua. We compare correlations among traits and intraspecific trait variances with those of terrestrial plants and among epiphyte taxonomic groups. We also test trait responses to environmental differences between sites and land use types, and within zones of the tree. We find that epiphyte leaf traits fall towards the slower end of the LES, but with about one‐third lower leaf nitrogen per change in specific leaf area (SLA) relative to terrestrial herbaceous plants. Bromeliads show less relationship between these traits than other epiphyte groups and also deviate in other trait interrelationships, suggesting unique leaf construction. Trait–environment relationships varied most strongly along vertical gradients within trees, but some traits, including SLA and carbon isotope ratio, also responded to land use and site differences. We present evidence that trait relationships established for terrestrial plants appear to translate to epiphytes, but identify some possible caveats. Strong trait response to vertical gradients within trees suggests that within‐canopy shifts could provide resilience to climate and land use changes for some epiphyte species.

Shade and salinity responses of two dominant coastal wetland grasses: implications for light competition at the transition zone.

Coastal wetlands are threatened by the increased salinity that may result from sea level rise. Salinity stress alters species zonation patterns through changes in competitive outcome between species differing in salinity tolerance. This study therefore aimed to understand how salinity and light affect two dominant and competing coastal wetland grasses that differ in salt tolerance, height and photosynthetic metabolism. The C4 species Spartina anglica and the C3 species Phragmites australis were grown at five salinity levels (0, 7, 14, 21 and 28 ppt) and two light fluxes (100 % and 50 % of natural daylight) in an outdoor experimental setup for 102 d with full access to nutrients. Salinity reduced the biomass, height and shoot density of P. australis from 81.7 g dry weight (DW), 0.73 m and 37 shoots per pot at a salinity of 0 ppt to 16.8 gDW, 0.3 m and 14 shoots per pot at a salinity of 28 ppt. Biomass, height and shoot density of S. anglica did not respond or were only slightly reduced at the highest salinity of 28 ppt. High salinity also resulted in a higher tissue concentration of N and P in P. australis. Both species had low ability to acclimate to the lower light flux. Shade acclimation in S. anglica occurred via modest changes in specific leaf area, pigment content and biomass allocation. High salinity reduced traits important for light competition and increased the nutrient concentration in P. australis leaf and root biomass, while this was overall unaffected in S. anglica. This is likely to reduce the competitive ability of P. australis over S. anglica for light because at high salinities the former cannot effectively shade the lower-growing S. anglica. Neither species effectively acclimates to shade, which could explain why S. anglica does not occur in the understorey of P. australis at low salinities.

MicroRNA156-mediated changes in leaf composition lead to altered photosynthetic traits during vegetative phase change.

Plant morphology and physiology change with growth and development. Some of these changes are due to change in plant size and some are the result of genetically programmed developmental transitions. In this study we investigate the role of the developmental transition, vegetative phase change (VPC), on morphological and photosynthetic changes. We used overexpression of microRNA156, the master regulator of VPC, to modulate the timing of VPC in Populus tremula×alba, Zea mays, and Arabidopsis thaliana to determine its role in trait variation independent of changes in size and overall age. Here, we find that juvenile and adult leaves in all three species photosynthesize at different rates and that these differences are due to phase-dependent changes in specific leaf area (SLA) and leaf N but not photosynthetic biochemistry. Further, we found juvenile leaves with high SLA were associated with better photosynthetic performance at low light levels. This study establishes a role for VPC in leaf composition and photosynthetic performance across diverse species and environments. Variation in leaf traits due to VPC are likely to provide distinct benefits under specific environments; as a result, selection on the timing of this transition could be a mechanism for environmental adaptation.

Plant architectural responses in simultaneous maize/soybean strip intercropping do not lead to a yield advantage

AbstractMaize/soybean strip intercropping is a commonly used system throughout China with high crop yields at reduced nutrient input compared to sole maize. Maize is the taller crop, and due to its dominance in light capture over soybean in the intercrop, maize is expected to outperform maize in sole cropping. Conversely, soybean is the subordinate crop and intercropped soybean plants are expected to perform worse than sole soybean. Crop plants show plastic responses in plant architecture to their growing conditions to forage for light and avoid shading. There is little knowledge on plant architectural responses to growing conditions in simultaneous (non‐relay) intercropping and their relationship to species yields. A two‐year field experiment with two simultaneous maize/soybean intercropping systems with narrow and wide strips was conducted to characterise architectural traits of maize and soybean plants grown as intercrop and sole crops. Intercropped maize plants, especially those in border rows, had substantially greater leaf area, biomass and yield than maize plants in sole crops. Intercropped soybean plants, especially those in border rows, had lower leaf area, biomass and yield than sole soybean plants. Overall intercrop performance was similar to that of sole crops, with the land equivalent ratio (LER) being only slightly greater than one (1.03–1.08). Soybean displayed typical shade avoidance responses in the intercrop, such as greater internode elongation and changes in specific leaf area, but these responses could not overcome the consequences of the competition with the taller maize plants. Therefore, in contrast to relay intercrop systems, in the studied simultaneous maize/soybean system, plastic responses did not contribute to practically relevant increases in resource capture and yield at whole system (i.e., intercrop) level.

Global response patterns of plant photosynthesis to nitrogen addition: A meta-analysis.

A mechanistic understanding of plant photosynthetic response is needed to reliably predict changes in terrestrial carbon (C) gain under conditions of chronically elevated atmospheric nitrogen (N) deposition. Here, using 2,683 observations from 240 journal articles, we conducted a global meta-analysis to reveal effects of N addition on 14 photosynthesis-related traits and affecting moderators. We found that across 320 terrestrial plant species, leaf N was enhanced comparably on mass basis (Nmass , +18.4%) and area basis (Narea , +14.3%), with no changes in specific leaf area or leaf mass per area. Total leaf area (TLA) was increased significantly, as indicated by the increases in total leaf biomass (+46.5%), leaf area per plant (+29.7%), and leaf area index (LAI, +24.4%). To a lesser extent than for TLA, N addition significantly enhanced leaf photosynthetic rate per area (Aarea , +12.6%), stomatal conductance (gs , +7.5%), and transpiration rate (E, +10.5%). The responses of Aarea were positively related with that of gs , with no changes in instantaneous water-use efficiency and only slight increases in long-term water-use efficiency (+2.5%) inferred from 13 C composition. The responses of traits depended on biological, experimental, and environmental moderators. As experimental duration and N load increased, the responses of LAI and Aarea diminished while that of E increased significantly. The observed patterns of increases in both TLA and E indicate that N deposition will increase the amount of water used by plants. Taken together, N deposition will enhance gross photosynthetic C gain of the terrestrial plants while increasing their water loss to the atmosphere, but the effects on C gain might diminish over time and that on plant water use would be amplified if N deposition persists.

The effect of elevational gradient on alpine gingers (Roscoea alpina and R. purpurea) in the Himalayas.

There is currently enormous interest in how morphological and physiological responses of herbaceous plants may be affected by changing elevational gradient. Mountain regions provide an excellent opportunity to understand how closely related species may adapt to the conditions that rapidly change with elevation. We investigated the morphological and physiological responses of two Himalayan alpine gingers (Roscoea alpina and R. purpurea) along two different vertical transects of 400 m, R. purpurea between 2,174–2,574 m a.s.l and R. alpina between 2,675–3,079 m a.s.l. We measured the variables of plant height, leaf length, leaf area, specific leaf area, and stomata density at five plots, along the vertical transect at an elevational gap of ca. 100 m. Results revealed that with increased elevation plant height, and leaf area decreased while stomata density increased, whereas changes in specific leaf area, were not correlated with the elevation. Our results reveal that these alpine gingers undergo local adaptation by modifying their plant height, leaf area and stomata density in response to the varying selection pressure associated with the elevational gradient. Thus, the findings of this research provide valuable information on how a narrow range of elevational gradient affects the herbaceous plants at the alpine habitat of the Himalayas.

Functional composition of epiphyte communities in the Colombian Andes.

We identify changes in the functional composition of vascular epiphytes along a tropical elevational gradient with the aim of quantifying the role of climate in determining the assembly of epiphyte communities. We measured seven leaf functional traits (leaf area, specific leaf area, leaf dry-matter content, leaf thickness, force to punch, stomatal density, and potential conductance index) in the 163 most abundant epiphyte species recorded across 10 sites located along an elevational gradient between 60 and 2,900m above sea level in the Colombian Andes. We grouped the epiphyte species into seven hierarchical functional groups according to their most characteristic leaf traits. Along the elevational gradient, the two main independent leaf trait dimensions that distinguished community assemblages were defined primarily by leaf area-photosynthetic (LAPS) and mass-carbon (LMCS) gradients. Mean annual temperature was the main determinant of species position along LAPS. In contrast, local changes in specific leaf area due to variation in the epiphytes' relative height of attachment was the main determinant of their position along the LMCS. Our findings indicate that epiphytic plant leaves have evolved to optimize and enhance photosynthesis through a leaf area-based strategy and carbon acquisition through investments in construction costs of leaf area per unit of biomass that aim to regulate light capture and tissue development. Given that most studies of plant functional traits neglect vascular epiphytes, our quantification of the multiple dimensions of epiphyte leaf traits greatly augments our understanding of vascular plant function and adaptation to changing environments.

Changes in specific leaf area of dominant plants in temperate grasslands along a 2500-km transect in northern China

Specific leaf area (SLA) is a key trait with great ecological importance as it correlates with whole plant growth. We aimed to investigate how SLA varies with environmental factors at a geographical scale in temperate grasslands. We measured SLA and mass-based leaf nitrogen content (Nmass) of four dominant plant genera along a 2500 km climatic gradient in northern China grassland, and correlated SLA with mean annual precipitation (MAP), mean annual temperature (MAT), soil nitrogen concentration (soil N), soil C:N and Nmass. Climate accounts much more for SLA variation than soil variables for Stipa, Cleistogens and Carex. SLA of Stipa is negatively associated with MAP and soil N, while positively with MAT, but Cleistogenes and Carex show the opposite. For Leymus, soil N promotes SLA and accounts for largest fraction of SLA variation. Overall, SLA was positively correlated with Nmass in semi-arid regions, but not significant in arid regions. The genus-dependent responses of SLA may have consequences on ecosystem functioning, thus may help to predict the community composition and ecosystem functions under future climate scenario. The finding of SLA-Nmass trade-off and its susceptibility to precipitation will advance our understanding on plant resource use strategies.

Genotypic variability in Populus tremula L. affects how anthropogenic nitrogen enrichment influences litter decomposition

Background and aimsBoreal forests can receive substantial nitrogen (N) enrichment via atmospheric N deposition and industrial forest fertilization. While it is known that N enrichment can impact ecosystem properties, such as litter decomposition, it remains poorly understood how genetic variability within plant species modifies these impacts.MethodsWe grew replicates of ten Populus tremula L. genotypes (GTs) under 3 N conditions; ambient, and levels representing atmospheric N deposition and industrial forest fertilization. We measured leaf and litter physical and chemical traits, and conducted a litter decomposition assay.ResultsLeaf traits varied due to N treatment, GT, and constitutive tannin levels. Leaf traits were in some cases correlated with litter traits, and decomposition was influenced by single and interactive effects of N and GT. Nitrogen addition unexpectedly decelerated decomposition, potentially due to changes in specific leaf area (SLA). Variation in decomposition rates among the GTs was best explained by their differences in SLA, and lignin:N ratio. Nitrogen addition also caused a shift in which traits most strongly influenced decomposition.ConclusionsOur findings highlight that the considerable diversity present in tree species can have a strong influence on ecosystem processes, such as decomposition, and how these processes respond to environmental change.

A descriptive model o Scots pine (Pinus silvestris) L. seedling's growth during the first growing season

Scots pine seedlings were grown in pots from seed under outside conditions. Plant material was harvested ten times in fortnight periods, throughout the growing season. At each harvest, each plant was divided into particular organs and their dimensions as well as fresh and dry weight were determined. Seasonal course of growth of particular organs as well as changes in specific leaf area and distribution of dry matter between shoot and root were investigated. Net assimilation rate (NAR) and relative growth rate (RGR) were calculated from the fitted logistic growth curves.

Variable effects of nutrient enrichment on soil respiration in mangrove forests

Mangrove forests are globally important sites of carbon burial that are increasingly exposed to nutrient pollution. Here we assessed the response of soil respiration, an important component of forest carbon budgets, to nutrient enrichment over a wide range of mangrove forests. We assessed the response of soil respiration to nutrient enrichment using fertilization experiments within 22 mangrove forests over ten sites. We used boosted regression tree (BRT) models to determine the importance of environmental and plant factors for soil respiration and its responsiveness to fertilizer treatments. Leaf area index explained the largest proportion of variation in soil respiration rates (LAI, 45.9 %) followed by those of site, which had a relative influence of 39.9 % in the BRT model. Nutrient enrichment enhanced soil respiration only in nine out of 22 forests. Soil respiration in scrub forests showed a positive response to nutrient addition more frequently than taller fringing forests. The response of soil respiration to nutrient enrichment varied with changes in specific leaf area (SLA) and stem extension, with relative influences of 14.4 %, 13.6 % in the BRT model respectively. Soil respiration in mangroves varied with LAI, but other site specific factors also influenced soil respiration and its response to nutrient enrichment. Strong enhancements in aboveground growth but moderate increases in soil respiration with nutrient enrichment indicated that nutrient enrichment of mangrove forests has likely increased net ecosystem production.

Humidity‐driven changes in growth rate, photosynthetic capacity, hydraulic properties and other functional traits in silver birch (Betula pendula)

AbstractA study was performed on saplings of silver birch (Betula pendula Roth) growing at the free air humidity manipulation site, which was established to investigate the effect of increased air humidity on tree performance and canopy functioning. The aim of the experiment was to simulate the impact of the increasing atmospheric humidity on forest ecosystems predicted for northern Europe. Artificially elevated relative humidity (RH), which causes transpirational flux to decrease, diminished nutrient supply to the foliage; leaf nitrogen content, phosphorus content and P:N ratio decreased. The changes in leaf nutritional status brought about a considerable decline in both photosynthetic capacity (Amax, Vcmax, Jmax) and tree growth rate. The manipulation induced diverse changes in tree hydraulic architecture and other functional traits. Different segments of the soil‐to‐leaf water transport pathway responded differently: leaf hydraulic conductance (KL) decreased, while hydraulic conductance of root systems (KR) and leaf‐specific conductivity of stem‐wood increased in response to elevated RH. Humidification caused the Huber values of stems to increase, thus reflecting changes in allocation patterns; relatively more resources were allocated to vascular tissue and less to foliage. The elevated RH induced substantial changes in specific leaf area (increased), branch‐ (decreased) and stem‐wood density (decreased). The observed responses suggest that the expected climate‐change‐induced increase in the growth rate of trees at northern latitudes (boreal areas) due to the earlier start of the growing season in spring or higher carbon assimilation rate could be smaller or null if temperature rise is accompanied by a rise in atmospheric absolute humidity.

Little strokes fell great oaks: minor but chronic herbivory substantially reduces birch growth

Modern concepts of plant tolerance to herbivory are primarily based on studies of short‐term severe damage, whereas the effects of minor chronic damage to long‐lived woody plants, corresponding to background herbivory (2–15% annual loss of foliar biomass in boreal and temperate forests), remain poorly understood. In our experiment, the annual removal of 2, 4, 8 and 16% of the leaf area from naturally growing mountain birch Betula pubescens subsp. czerepanovii saplings during a seven‐year period resulted in a pronounced reduction of plant vertical growth (–30, –34, –45 and –78%, respectively). Leaf size decreased first (already after one year of the 16% treatment), resulting in the reduction of the total leaf area. This effect was followed by a considerable decrease in the length of long shoots in all treatments. Leaf number on the plant was maintained for a longer time, being reduced by the end of the experiment in 16% treatment only; no changes in specific leaf area or chlorophyll fluorescence were observed in either of the treatments. This pattern may indicate that the plant reallocates resources from the growth of the woody parts to the maintenance of the photosynthetic area, and can be seen as a strategy of tolerance to minor herbivory, whereas compensatory responses typical of severe herbivory (increased photosynthesis rates and shoot regrowth) have not been detected. The predicted 2–5% increase in background herbivory due to climate warming can potentially produce previously unrecognised negative impacts on tree growth. We conclude that in the long term, background herbivory is likely to impose stronger effects on the growth of woody plants than short‐term devastating outbreaks of defoliators, thus contributing more to the development of plant evolutionary adaptations to herbivory than severe but episodic bouts of damage.

Changes in specific leaf area and photosynthetic nitrogen-use efficiency associated with physiological acclimation of two hybrid poplar clones to intraclonal competition

Photosynthesis is the most important process driving productivity, and its acclimation to intraclonal competition is not well understood in hybrid poplars. The aim of this study was to examine the physiological response of the crown of two hybrid poplar clones, BT747215 ( Populus balsamifera L. × Populus trichocarpa Torr. & A. Gray) and MB915319 ( Populus maximowiczii A. Henry × P. balsamifera ), to intraclonal competition. We measured light-saturated photosynthesis (Amax), leaf N content on an area basis (Narea), specific leaf area (SLA), and photosynthetic N-use efficiency (PNUE) for three successive growing seasons on trees planted at three spacings (1 m × 1 m, 3 m × 3 m, and 5 m × 5 m). Crowns were sampled at 10 locations corresponding to vertical and horizontal subdivisions. Significant changes took place at the crown level in the closest spacing (1 m × 1 m) compared with the wider spacings (3 m × 3 m and 5 m × 5 m): (i) 30% decrease in Narea, (ii) 20% increase in SLA, and (iii) 40% increase in PNUE. The slope of the Amax–Narea curve was greatest in the closest spacing, indicating a greater change in Amax per unit change in Narea. The two hybrid poplar clones had a similar morphophysiological response to changes of spacing. Both clones showed physiological acclimation of their foliage in response to intraclonal competition through modulation of SLA and PNUE.

Leaf Chemical and Optical Properties of Metrosideros polymorpha Across Environmental Gradients in Hawaii

ABSTRACTLeaf chemical, biophysical, and optical properties were measured in 13 populations of Metrosideros polymorpha across gradients of soil fertility and climate in Hawaii. Climate (predominantly temperature) caused large changes in specific leaf area (SLA) and SLA‐linked traits, including nitrogen (N) and pigment contents, as did conditions of highest soil fertility on 20 ky old substrates. When averaged by site, chemical constituent ratios containing chlorophyll (Car/Chl, Chl/N) varied more across climate than substrate gradients, while the Chl a/b ratio was similarly influenced by climate and substrate. Variations in Chl a/b ratios and SLA were similar to those found previously in a common garden of M. polymorpha taken from our climate gradient, suggesting strong genetic control over these traits. Optical reflectance indices related to photosynthetic function were closely correlated to pigment changes, varying three times more in response to climate than across substrate ages. Combined, our results suggest that variation in leaf structure, composition, and function of M. polymorpha is a result of genetic and phenotypic adaptation to environmental differences, and that these variations are greater in response to climate (especially temperature) than to soil fertility.

Cutting‐edge international tree research in New Phytologist

Cutting‐edge international tree research in <i>New Phytologist</i>

Light‐dependent changes in biomass allocation and their importance for growth of rain forest tree species

Summary Sapling growth of six rain forest tree species was compared to evaluate whether species respond in a similar way to a natural light gradient. Saplings were measured non‐destructively; production and loss of leaves, stem and branches were analysed in detail. Sapling height growth was positively related to light environment and leaf area. No single descriptor of light environment explained sapling growth best. Direct or diffuse light could explain plant growth, depending on species. Seventeen percent of the saplings had negative relative biomass growth rates, although they occurred in fairly bright conditions. Negative growth rates were caused by leaf shedding and stem breakage. Sapling relative growth rate increased with irradiance, mainly because of an increase in net assimilation rate. On a shoot basis, shaded plants had a smaller leaf mass fraction (LMF) and a larger specific leaf area, resulting in similar leaf area ratios (LAR) to those of sun plants. This contrasts with the results of seedling studies under controlled conditions, where LMF and LAR increased with shade. Biomass partitioning to leaf growth decreased with irradiance and relative growth rate of the sapling. This leaf partitioning ratio was better correlated with RGR than with irradiance. Species differed in the effect of light‐dependent changes in specific leaf area (SLA) on growth. This underscores the importance of SLA in explaining differences in species performance in a forest environment. Nevertheless, the effect of SLA was not related to the shade tolerance of the species.