Global patterns of intraspecific leaf trait responses to elevation

Elevational gradients are often used to quantify how traits of plant species respond to abiotic and biotic environmental variations. Yet, such analyses are frequently restricted spatially and applied along single slopes or mountain ranges. Since we know little on the response of intraspecific leaf traits to elevation across the globe, we here perform a global meta‐analysis of leaf traits in 109 plant species located in 4 continents and reported in 71 studies published between 1983 and 2018. We quantified the intraspecific change in seven morpho‐ecophysiological leaf traits along global elevational gradients: specific leaf area (SLA), leaf mass per area (LMA), leaf area (LA), nitrogen concentration per unit of area (Narea), nitrogen concentration per unit mass (Nmass), phosphorous concentration per unit mass (Pmass) and carbon isotope composition (δ¹³C). We found LMA, Narea, Nmass and δ¹³C to significantly increase and SLA to decrease with increasing elevation. Conversely, LA and Pmass showed no significant pattern with elevation worldwide. We found significantly larger increase in Narea, Nmass, Pmass and δ¹³C with elevation in warmer regions. Larger responses to increasing elevation were apparent for SLA of herbaceous compared to woody species, but not for the other traits. Finally, we also detected evidences of covariation across morphological and physiological traits within the same elevational gradient. In sum, we demonstrate that there are common cross‐species patterns of intraspecific leaf trait variation across elevational gradients worldwide. Irrespective of whether such variation is genetically determined via local adaptation or attributed to phenotypic plasticity, the leaf trait patterns quantified here suggest that plant species are adapted to live on a range of temperature conditions. Since the distribution of mountain biota is predominantly shifting upslope in response to changes in environmental conditions, our results are important to further our understanding of how plants species of mountain ecosystems adapt to global environmental change.     

Plastic changes of leaf mass per area and leaf nitrogen content in response to canopy openings in saplings of eight deciduous broad-leaved tree species

Leaf nitrogen content per area (N_area) is a good indicator of assimilative capacity of leaves of deciduous broad-leaved trees. This study examined the degrees of increase in N_area in response to canopy openings as leaf mass per area (LMA) and leaf nitrogen content per mass (N_mass) in saplings of eight deciduous broad-leaved tree species in Hokkaido, northern Japan. Five of the species were well-branched species with a large number of small leaves (lateral-growth type), and the other three species were less-branched species with a small number of large leaves (vertical-growth type). The degrees of increase in N_area were compared between the two crown types. In closed-canopy conditions, leaves of the vertical-growth species tended to have a lower LMA and higher N_mass than those of the lateral-growth species, which resulted in similar N_area for both. LMA increased in canopy openings in the eight species, and the degrees of increase were not largely different between the lateral- and vertical-growth species. On the contrary, N_mass was unchanged in canopy openings in the eight species. As a result, N_area of each species increased in canopy openings in proportion to the increase in LMA, and the degrees of increase in N_area were similar in the lateral- and vertical-growth species. Therefore, this study showed that the degrees of increase in N_area were not correlated with the crown architecture (i.e., the lateral- and vertical-growth types).     

Modulation of leaf economic traits and trait relationships by climate

Aim Our aim was to quantify climatic influences on key leaf traits and relationships at the global scale. This knowledge provides insight into how plants have adapted to different environmental pressures, and will lead to better calibration of future vegetation–climate models. Location The data set represents vegetation from 175 sites around the world. Methods For more than 2500 vascular plant species, we compiled data on leaf mass per area (LMA), leaf life span (LL), nitrogen concentration (N_mass) and photosynthetic capacity (A_mass). Site climate was described with several standard indices. Correlation and regression analyses were used for quantifying relationships between single leaf traits and climate. Standardized major axis (SMA) analyses were used for assessing the effect of climate on bivariate relationships between leaf traits. Principal components analysis (PCA) was used to summarize multidimensional trait variation. Results At hotter, drier and higher irradiance sites, (1) mean LMA and leaf N per area were higher; (2) average LL was shorter at a given LMA, or the increase in LL was less for a given increase in LMA (LL–LMA relationships became less positive); and (3) A_mass was lower at a given N_mass, or the increase in A_mass was less for a given increase in N_mass. Considering all traits simultaneously, 18% of variation along the principal multivariate trait axis was explained by climate. Main conclusions Trait‐shifts with climate were of sufficient magnitude to have major implications for plant dry mass and nutrient economics, and represent substantial selective pressures associated with adaptation to different climatic regimes.     

南亚热带不同演替阶段森林优势树种叶片构建成本与机械抗性的协同关系

为探究不同演替阶段森林优势种叶片资源获取策略的差异以及叶片构建成本与机械抗性的关系,对我国南亚热带不同演替阶段森林14优势种的叶片构建成本、机械抗性、角质层厚度和比叶重等结构性状进行测定。结果表明,与演替早期相比,演替晚期优势种具有更高的单位面积叶片构建成本、叶片撕裂力以及穿透力,但其叶片最大光合速率较低;同时,单位面积叶片构建成本与机械抗性呈显著正相关关系,而叶片角质层厚度、比叶重等结构性状也与叶片构建成本、机械抗性均呈显著正相关。因此,从叶片能量投资策略上反映了南亚热带森林演替进程中叶片构建成本与机械抗性的协同关系。     

Leaf nitrogen distribution in relation to leaf age and photon flux density in dominant and subordinate plants in dense stands of a dicotyledonous herb

We studied the effects of photon flux density (PFD) and leaf position, a measure of developmental age, on the distribution of nitrogen content per unit leaf area (N _area) in plants of different heights, in dense stands grown at two nitrogen availabilities and in solitary plants of the erect dicotyledonous herb Xanthium canadense. Taller more dominant plants received higher PFD levels and experienced a larger difference in relative PFD between their youngest and oldest leaves than shorter subordinate plants in the stands. Differences in PFD between leaves of solitary plants were assumed to be minimal and differences in leaf traits, found for these plants, could thus be mainly attributed to an effect of leaf position. In the solitary plants, N _area decreased with leaf position while in the plants from the stands it decreased with decreasing relative PFD, indicating both factors to be important in determining the distribution of N _area. Due to the effect of leaf position on N _area, leaves of subordinate plants had a higher N _area than older leaves of dominant plants which were at the same height or slightly higher in the canopy. Consequently, the N _area distribution patterns of individual plants plotted as a function of relative PFD were steeper, and probably closer to the optimal distribution which maximizes photosynthesis, than the average distribution in the stand. Leaves of subordinate plants had a lower mass per unit area (LMA) than those of dominant plants. In the dominant plants, LMA decreased with decreasing relative PFD (and with leaf position) while in the subordinate plants it increased. This surprising result for the subordinate plants can be explained by the fact that, during the course of a growing season, these plants became increasingly shaded and newer leaves were thus formed at progressively lower light availability. This indicates that LMA was strongly determined by the relative PFD at leaf formation and to a lesser extent by the current PFD. Leaf N content per unit mass (N _mass) was strongly determined by leaf position independent of relative PFD. This indicates that N _mass is strongly ontogenetically related to the leaf-aging process while changes in N _area, in response to PFD, were regulated through changes in LMA. Received: 11 May 1997 / Accepted: 9 September 1997     

Spatial patterns of photosynthetic characteristics and leaf physical traits of plants in the Loess Plateau of China

The spatial patterns of photosynthetic characteristics and leaf physical traits of 171 plants belonging to nine life-forms or functional groups (trees, shrubs, herbs, evergreen trees, deciduous trees, C₃ and C₄ herbaceous plants, leguminous and non-leguminous species) and their relationships with environmental factors in seven sites, Yangling, Yongshou, Tongchuan, Fuxian, Ansai, Mizhi and Shenmu, ranging from south to north in the Loess Plateau of China were studied. The results showed that the leaf light-saturated photosynthetic rate (P_max), photosynthetic nitrogen use efficiency (PNUE), chlorophyll content (Chl), and leaf mass per area (LMA) of all the plants in the Loess Plateau varied significantly among three life-form groups, i.e., trees, shrubs and herbs, and two groups, i.e., evergreen trees and deciduous trees, but leaf nitrogen content differed little among different life-form groups. For the 171 plants in the Loess Plateau, leaf P_max was positively correlated with PNUE. The leaf nitrogen content per unit area (N_area) was positively correlated but Chl was negatively correlated with the LMA. When controlling the LMA, the N_area was positively correlated with the Chl (partial r = 0.20, P < 0.05). With regard to relationships between photosynthetic characteristics and leaf physical traits, the P_max was positively correlated with N _area, while the PNUE was positively correlated with the Chl and negatively correlated with the N_area and LMA. For all the species in the Loess Plateau, the PNUE was negatively correlated with the latitude and annual solar radiation (ASR), but positively correlated with the mean annual rainfall (MAR) and mean annual temperature (MAT). With regard to the leaf physical traits, the leaf Chl was negatively correlated with the latitude and ASR, but positively correlated with the MAR and MAT. However, the N_area and LMA were positively correlated with the latitude and ASR, but negatively correlated with the MAR and MAT. In general, leaf N_area and LMA increased, while PNUE and Chl decreased with increases in the latitude and ASR and decreases in MAR and MAT. Electronic supplementary material The online version of this article () contains supplementary material, which is available to authorized users.     

不同种源五角枫幼苗叶片N、P化学计量学特征对氮添加的响应

不同土壤氮环境下植物对氮沉降的响应趋势不同,因此研究不同种源地的五角枫(Acer mono)对氮沉降的响应机理具有重要的意义。为了深入了解不同种源五角枫对氮沉降的适应和响应机制,主要通过3个种源的五角枫幼苗氮添加控制实验,分析不同种源的五角枫幼苗比叶面积(SLA)和叶片干物质含量(LMDC)以及叶片N、P含量和N∶P对氮添加的响应规律。结果表明:(1)不同氮添加处理下,内蒙古种源五角枫幼苗(NW)和山西种源五角枫幼苗(SW)的LDMC均显著低于对照,NW和SW在N4条件下表现为显著的促进作用。随着氮添加浓度的增加,NW与北京种源的五角枫幼苗(BW)的SLA在N4条件下显著增加;SW的SLA在N2的水平下显著增加。(2)氮添加下,只有SW的P_(mass)在N1水平下显著增加,N_(mass)在N1和N3水平下表现为显著增加。说明在低氮水平下,能够促进SW对P的吸收,从而增加植物体内对P的积累。同时在低氮和中高氮条件下,能够促进SW对N的吸收,说明SW能较好的适应低氮和高氮环境,使其生存能力更强。(3)分析变异来源及各指标的相关性得出,氮添加条件下,五角枫的SLA、LDMC、P_(area)及N∶P与氮添加处理呈显著的相关关系,而SLA、LDMC、N_(mass)、P_(mass)、Narea、P_(area)和N∶P对氮添加处理和种源的交互作用均未表现出相关关系,说明引起五角枫各性状主要受氮添加处理影响。(4)综合各指标的变化,氮添加条件下,NW的LDMC显著降低,SLA显著增大,同时叶N含量、叶P含量以及N∶P比较高;SW的LDMC显著降低,SLA增大,同时叶N含量、叶P含量表现为显著增大,结合叶经济谱理论分析得出,SW和NW属于"快速投资-收益"型,而BW倾向于"缓慢投资-收益"型。因此,不同种源的五角枫对于氮沉降的响应存在差异,并且持续的氮添加已经改变了五角枫的适应性。     

云南文山石漠化区车桑子叶脉密度与叶氮含量关系对生境的响应

植物叶脉特征和叶氮含量的变化影响着叶片经济谱的形成,为验证叶片结构中叶脉网络构建提供了理论依据。该文以单位质量叶氮含量(N_(mass))和单位面积叶氮含量(N_(area))分别表示叶氮含量,采取主成分分析、线性回归分析的方法,研究了云南文山石漠化区旷地(Ⅰ)、林缘(Ⅱ)和林下(Ⅲ)3种自然生境下车桑子的叶脉密度(Vein density,VD)与N_(mass)和N_(area)的异速关系。结果表明:从乔灌群落的旷地到林下,车桑子的比叶面积、叶绿素总含量、光能利用率和N_(mass)逐渐增大,光饱和点、光补偿点、水分利用效率、VD、N_(area)逐渐减小,净光合速率、蒸腾速率、气孔导度呈先增大后减小的趋势。VD与叶氮含量呈不同程度的相关性,在生境I和III,VD与N_(mass)和N_(area)分别具有显著的负相关(P0.05)和正相关(P0.05);在生境Ⅱ,VD与N_(mass)和N_(area)分别呈不显著负相关(P0.05)和正相关(P0.05)。车桑子在旷地强光生境,高VD的叶片含有低N_(mass)高N_(area),而林下荫蔽生境偏向于相反的配置模式,反映了石漠化区植物较强的叶脉可塑性及其与氮利用性状的权衡机制。     

唐古特白刺叶功能性状沿气候梯度的变异特征

叶功能性状与植物的生长对策及资源利用效率密切相关,研究叶功能性状沿气候梯度的变异特征能为理解植物对气候变化的响应机制提供一种简便可行的测定指标。以我国西北荒漠地区广泛分布的唐古特白刺（Nitraria tangutorum）为研究对象,对其比叶面积（SLA）、单位质量和单位面积叶氮含量（N_mass、N_area）、单位质量和单位面积叶建成成本（CC_mass、CC_area）进行测定,分析这些叶功能性状及性状相关关系沿气候梯度的变异特征。结果表明,唐古特白刺叶功能性状（CC_area除外）在气候梯度下存在显著差异,其中,温度是决定唐古特白刺SLA变化的主要因子,SLA随着温度的增加而增加;降水和温度对唐古特白刺N_mass、N_area和CC_mass均有显著影响,N_mass和N_area随着降水和温度的增加而降低,而CC_mass呈增加趋势。沿气候梯度,唐古特白刺SLA-N_mass、CC_mass-N_mass和CC_area-N_area的线性正相关关系发生平移,导致在相同SLA、CC_mass和CC_area下,降水和温度较低的地区具有更高的N_mass和N_area。这一结果表明唐古特白刺能通过调节叶功能性状之间的关系来适应气候的变化,并形成性状间的最佳功能组合。     

Reconciling the apparent difference between mass- and area-based expressions of the photosynthesis-nitrogen relationship

The relationship between photosynthetic carbon assimilation (A _max) and leaf nitrogen content (N _leaf) can be expressed on either a leaf area basis (A _area vs N _area) or a leaf mass basis (A _mass vs N _mass). Dimensional analysis shows that the units for the slope of this relationship are the same for both expressions (μmol [CO₂] g⁻¹ [N] s⁻¹). Thus the slope measures the change in CO₂ assimilation per gram of nitrogen, independent of leaf mass or leaf area. Although they have the same units, large differences between the area and mass-based slopes have been observed over a broad range of taxonomically diverse species. Some authors have claimed that regardless of these differences, the fundamental nature of the A _max-N _leaf relationship is independent of the units of expression. In contrast, other authors have claimed that the area-based A _max-N _leaf relationship is fundamentally different from the mass-based relationship because of interactions between A _max, N _leaf, and leaf mass per area (LMA, g [leaf] m⁻² [leaf]). In this study we consider the mathematical relationships involved in the transformation from mass- to area-based expressions (and vice versa), and the implications this transformation has for the slope of the A _max-N _leaf relationship. We then show that the slope of the relationship is independent of the units of expression when the effect of LMA is controlled statistically using a multiple regression. The validity of this hypothesis is demonstrated using 13 taxonomically and functionally diverse C₃ species. This analysis shows that the slope of the A _max-N _leaf relationship is similar for the mass- and area-based expressions and that significant errors in the estimate of the slope can arise when the effect of LMA is not controlled. Received: 7 May 1998 / Accepted: 19 October 1998     

Adaptive characteristics of grassland community structure and leaf traits along an altitudinal gradient on a subtropical mountain in Chongqing,China

Community structure and leaf traits are important elements of terrestrial ecosystems. Changes of community structure and leaf traits are of particular use in the study of the influence of climate change on terrestrial ecosystems. Patterns of community structure (including species richness, above- and below-ground biomass) and leaf traits (including leaf mass per area (LMA), nitrogen content both on mass and area bases (N _mass and N _area), and foliar δ¹³C) from 19 grassland plots along an altitudinal transect at Hongchiba in Chongqing, China, were analyzed. Species richness along the altitudinal transect had a hump-shaped pattern. Above-ground biomass had a quadratic decrease along the altitudinal gradient whereas below-ground biomass had the opposite pattern. Change of above-ground biomass of various taxonomic groups with altitude was also studied. Poaceae showed strong negative relationships and Asteraceae showed a hump-shaped relationship with increase of altitude. Five common species of the grassland, Trifolium pratense, Geranium wilfordii, Aster tataricus, Leontopodium leontopodioides, and Spiraea prunifolia, were particularly studied for variation of leaf traits along the altitudinal gradient. Averaged for all species, LMA, N _area and foliar δ¹³C had positive correlations with altitude. N _mass did not change significantly as altitude increased. LMA and N _area showed significant positive relationships with foliar δ¹³C. The adaptive features of leaf traits among different species were not consistent. The study highlights specific adaptation patterns in relation to altitude for different plant species, provides further insights into adaptive trends of community structure and leaf traits in a specific ecological region filling a gap in the definition of global patterns, and adds to the understanding of how adaptive patterns of plants may respond to global climate change.     

Contrasting patterns of trait‐based community assembly in lianas and trees from temperate Australia

Trait variation in plant communities is thought to be constrained by two opposing community assembly processes operating at discrete spatial scales: habitat filtering and limiting similarity between coexisting species. Filtering processes cause convergence in ecological strategy as species are excluded from unsuitable sites, whilst limiting similarity leads to the divergence of trait values between co‐occurring species in order to alleviate competition for finite resources. Levels of alpha (within‐site) and beta (among‐site) trait variation can be indicative of the strength of these community assembly processes. We used trait‐gradient analysis to explicitly compare evidence of community assembly patterns in lianas (woody vines) and trees. These two growth forms exhibit striking differences in carbon capture and regeneration strategies, yet trait‐based mechanisms that maintain their coexistence remain understudied. Using data for four functional traits – leaf mass per area, leaf nitrogen content (N_mass), leaf area and seed mass – we partitioned interspecific trait variation in lianas and trees into alpha and beta components. Our three key findings were: 1) lianas and trees exhibit divergent patterns of trait‐based habitat filtering, due to differences in the relationship between leaf size and the other three traits examined (LMA, N_mass and seed mass), 2) on average, liana species possess smaller seeds, lower LMA and higher N_mass than do trees, but there was no clear difference in leaf area between the two growth forms, and 3) soil fertility was correlated with trait variation (leaf area, seed mass) at the site‐level in trees, but not in lianas. These results provide evidence that dominant growth forms can be filtered into the same habitat on the basis of different combinations of traits. Our findings have important implications for community assembly and co‐existence theory and for more pragmatic matters such as using trait‐based principles to inform community restoration.     

Herbivory alters plant carbon assimilation,patterns of biomass allocation and nitrogen use efficiency

Herbivory can trigger physiological processes resulting in leaf and whole plant functional changes. The effects of chronic infestation by an insect on leaf traits related to carbon and nitrogen economy in three Prunus avium cultivars were assessed. Leaves from non-infested trees (control) and damaged leaves from infested trees were selected. The insect larvae produce skeletonization of the leaves leaving relatively intact the vein network of the eaten leaves and the abaxial epidermal tissue. At the leaf level, nitrogen content per mass (N_mass) and per area (N_area), net photosynthesis per mass (A_mass) and per area (A_area), photosynthetic nitrogen-use efficiency (PNUE), leaf mass per area (LMA) and total leaf phenols content were measured in the three cultivars. All cultivars responded to herbivory in a similar fashion. The N_mass, A_mass, and PNUE decreased, while LMA and total content of phenols increased in partially damaged leaves. Increases in herbivore pressure resulted in lower leaf size and total leaf area per plant across cultivars. Despite this, stem cumulative growth tended to increase in infected plants suggesting a change in the patterns of biomass allocation and in resources sequestration elicited by herbivory. A larger N investment in defenses instead of photosynthetic structures may explain the lower PNUE and A_mass observed in damaged leaves. Some physiological changes due to herbivory partially compensate for the cost of leaf removal buffering the carbon economy at the whole plant level.     

木兰科常绿与落叶物种叶片构建策略的差异

为探究木兰科(Magnoliaceae)常绿与落叶物种叶片构建的生理生态策略,选取黄山木兰(Yulaniacylindrica)、玉兰(Y.denudata)和鸡公山玉兰(Y. jigongshanensis) 3种落叶物种,以及荷花玉兰(Magnolia grandiflora)、含笑花(Michelia figo)、石碌含笑(M. shiluensis) 3种常绿物种,对其叶片构建成本和叶片寿命相关的性状进行比较。结果表明,木兰科3落叶种的单位叶片面积成本(CCarea)显著低于3常绿种,但落叶和常绿物种的叶片质量成本(CCmass)差异不显著。落叶物种的叶氮、磷含量(Nmass,Pmass)和比叶面积(SLA)均显著高于常绿物种,而叶片寿命(LLS)显著低于常绿物种。CCarea与LLS呈显著正相关,Nmass、Pmass和SLA均与LLS呈显著负相关。这说明木兰科玉兰属落叶物种单位面积叶片构建成本小于常绿物种;落叶物种叶片寿命短,但采取低成本构建策略,提高比叶面积获得更多光资源,增加营养积累,也揭示了玉兰属落叶物种适应北亚热带较短的生长季和较低水热条件的生理生态策略。     

Biogeographic constraints on the world‐wide leaf economics spectrum

Aim The world‐wide leaf economic spectrum (LES) describes tight coordination of leaf traits across global floras, reported to date as being largely independent of phylogeny and biogeography. Here, we present and test an alternative, historical perspective that predicts that biogeography places significant constraints on global trait evolution. These hypothesized constraints could lead to important deviations in leaf trait relationships between isolated floras that were influenced by different magnitudes of genetic constraint and selection. Location Global, including floristic regions of the Northern and Southern Hemispheres, eastern North America, East Asia (EAS), the Hawaiian Islands and tropical mainland floras. Methods We use a large leaf‐trait database (GLOPNET) and species native distribution data to test for variation in leaf trait relationships modulated by floristic region, controlling for climatic differences. Standardized major axis analyses were used to evaluate biogeographic effects on bivariate relationships between LES traits, including relationships of photosynthetic capacity and dark respiration rate (A_mass–R_d‐mass), leaf lifespan and mass per area ratio (LL–LMA), and photosynthetic capacity and nitrogen content (A_mass–N_mass). Results Independent of climate or biome, floras of different evolutionary histories exhibited different leaf trait allometries. Floras of the Northern Hemisphere exhibited greater rates of return on resource investment (steeper slopes for the trait relationships analysed), and the more diverse temperate EAS flora exhibited greater slopes or intercepts in leaf trait relationships, with the exception of the A_mass–N_mass relationship. In contrast to our hypothesis, plants of the floristically isolated Hawaiian Islands exhibited a similar A_mass–N_mass relationship to those of mainland tropical regions. Main conclusions Differences in leaf trait allometries among global floristic regions support a historical perspective in understanding leaf trait relationships and suggest that independent floras can exhibit different tradeoffs in resource capture strategies.     

漓江水陆交错带植物叶性状对水淹胁迫的响应及经济谱分析

以漓江水陆交错带为研究区,分两个条带分别量测了适生植物的5个叶性状指标:最大净光合速率(A_(max))、比叶重(LMA)、单位质量叶片全氮含量(N_(mass))、单位质量叶片全磷含量(P_(mass))、单位质量叶片全钾含量(K_(mass))。研究重度淹没带与微度淹没带不同功能型植物叶性状间的差异,分析并讨论重度淹没带叶性状间的关系与全球尺度是否存在差异,探究重度淹没带植物对水淹生境的生理响应机制。结果如下:(1)重度淹没带植物叶片的A_(mass)、N_(mass)、P_(mass)显著高于微度淹没带。(2)乔木、灌木叶片的LMA均显著高于草本植物,而A_(mass)、PPUE均显著低于草本植物。(3)重度淹没带草本叶性状指标的N_(mass)、P_(mass)、PNUE均显著高于微度微度淹没带,而乔木、灌木的叶性状在两个条带的差异则不显著。(4)重度淹没带植物叶性状关系与全球尺度基本一致,其植物叶片具有低LMA,高A_(mass)、Nmas s、P_(mass)。分析可知,重度淹没带植物在出露期提高叶片光合效率及相关营养水平可能是其适应水淹胁迫特殊生境的关键策略之一;不同功能型植物对同一环境的适应能力存在一定的差异,草本对于水淹环境的响应更为积极,适应能力更好;重度淹没带也存在叶经济谱,其植物在经济谱中属于"快速投资-收益"型物种。     

Relationships of leaf dark respiration with light environment and tissue nitrogen content in juveniles of 11 cold-temperate tree species

It has been argued that plants adapted to low light should have lower carbon losses via dark respiration (Rd) than those not so adapted, and similarly, all species would be expected to down-regulate Rd in deep shade, because the associated advantages of high metabolic potential cannot be realized in such habitats. In order to test these hypotheses, and to explore the determinants of intraspecific variation in respiration rates, we measured Rd, leaf mass per unit area (LMA), and nitrogen content of mature foliage in juveniles of 11 cold-temperate tree species (angiosperms and conifers), growing in diverse light environments in forest understories in northern Minnesota. Among the seven angiosperm species, respiration on mass, area, and nitrogen bases showed significant negative overall relationships with shade tolerance level. Mass-based respiration rates (Rd _mass) of angiosperms as a group showed a significant positive overall relationship with an index of light availability (percentage canopy openness, %CO). Rd _mass of most conifers also showed evidence of acclimation of Rd _mass to light availability. LMA of all species also increased with increasing %CO, but this response was generally much stronger in angiosperms than in conifers. As a result, the response of area-based respiration (Rd _area) to %CO was dominated by ΔRd _mass for conifers, and by ΔLMA for most angiosperms, i.e., functional types differed in the components of acclimation of Rd _area to light availability. Among the seven angiosperm species, the relationships of leaf N on a mass basis (N _mass) with %CO were modulated by shade tolerance: negative slopes in shade-tolerant species may be related to the steep increases in LMA of these taxa along gradients of increasing light intensity, and associated dilution of N-rich, metabolically active tissue by increasing investment in leaf structural components. Although N _mass was therefore an unreliable predictor of variation in Rd _mass along light gradients, respiration per unit leaf N (Rd/N) was significantly positively correlated with %CO for most species. This probably reflects variation in the proportion of leaf N allocated to protein and/or the influence of leaf carbohydrate status on Rd. Species shade tolerance differences were not significantly correlated with the magnitude of either ΔRd _mass or ΔRd _area, indicating that variation in acclimation potential of Rd is much less important than inherent differences in this trait. Acclimation of Rd _mass to light availability appears to be a generalized feature of juvenile trees, and the important ecological trade-off is likely between high metabolic capacity in high light and low respiratory losses in low light. Received: 15 April 1999 / Accepted: 24 October 1999     

Global leaf-trait mapping based on optimality theory

Aim

Leaf traits are central to plant function, and key variables in ecosystem models. However recently published global trait maps, made by applying statistical or machine-learning techniques to large compilations of trait and environmental data, differ substantially from one another. This paper aims to demonstrate the potential of an alternative approach, based on eco-evolutionary optimality theory, to yield predictions of spatio-temporal patterns in leaf traits that can be independently evaluated.

Innovation

Global patterns of community-mean specific leaf area (SLA) and photosynthetic capacity (V_cmax) are predicted from climate via existing optimality models. Then leaf nitrogen per unit area (N_area) and mass (N_mass) are inferred using their (previously derived) empirical relationships to SLA and V_cmax. Trait data are thus reserved for testing model predictions across sites. Temporal trends can also be predicted, as consequences of environmental change, and compared to those inferred from leaf-level measurements and/or remote-sensing methods, which are an increasingly important source of information on spatio-temporal variation in plant traits.

Main conclusions

Model predictions evaluated against site-mean trait data from > 2,000 sites in the Plant Trait database yielded R² = 73% for SLA, 38% for N_mass and 28% for N_area. Declining species-level N_mass, and increasing community-level SLA, have both been recently reported and were both correctly predicted. Leaf-trait mapping via optimality theory holds promise for macroecological applications, including an improved understanding of community leaf-trait responses to environmental change.     

Photosynthesis, leaf morphology and chemistry of Pinus koraiensis and Quercus mongolica in broadleaved Korean pine mixed forest

Leaf traits and physiology are species-specific and various with canopy position and leaf age. Leaf photosynthesis, morphology and chemistry in the upper and lower canopy positions of Pinus koraiensis Sieb. et Zucc and Quercus mongolica Fisch. ex Turoz in broadleaved Korean pine forest were determined in September 2009. Canopy position did not significantly affect light-saturated photosynthetic rate based on unit area (P _area) and unit dry mass (P _mass), apparent quantum yield (α), light compensation point (LCP), light saturation point (LSP); total nitrogen (N_m), phosphorus (P_m), carbon (C_m), and chlorophyll content (Chl_m) per unit dry mass; leaf dry mass per unit area (LMA) and photosynthetic nitrogen-use efficiency (PNUE) for P. koraiensis current-year needles and Q. mongolica leaves. While in P. koraiensis one-year-old needles, P _area, P _mass, α and LCP in the upper canopy were lower than those in the lower canopy. The needles of P. koraiensis had higher Cm and LMA than leaves of Q. mongolica, but P _mass, Chl_m and PNUE showed opposite trend. There were no differences in P _area, LSP, N_m, and P_m between the two species. Needle age significantly influenced photosynthetic parameters, chemistry and LMA of P. koraiensis needles except LCP, LSP and C_m. In contrast to LMA, P _area, P _mass, N_m, P_m, Chl_m, and PNUE of one-year-old needles were significantly lower than those of current-year needles for P. koraiensis. The negative correlations between LMA and P _mass, N_m, P_m, Chl_m, and positive correlations between P _mass and N_m, P_m, Chl_m were found for P. koraiensis current-year needles and Q. mongolica leaves. Our results indicate that leaf nitrogen and phosphorus contents and nutrient absorption from soil are similar for mature P. koraiensis and Q. mongolica growing in the same environment, while difference in carbon content between P. koraiensis and Q. mongolica may be attributed to inherent growth characteristics.     

Leaf-trait relationships of <Emphasis Type="Italic">Quercus liaotungensis</Emphasis> along an altitudinal gradient in Dongling Mountain,Beijing

Few studies have examined leaf-trait relationships in the distribution of individual species along an environmental gradient. Here we address the issue by testing for the leaf-trait relationships of Quercus liaotungensis, a dominant deciduous woody species in northern China, along an altitudinal gradient in Dongling Mountain, Beijing. These leaf traits included specific leaf area (SLA), leaf dry matter content (LDMC), and leaf nitrogen, phosphorus, and potassium concentration on mass basis (N_mass, P_mass and K_mass, respectively). Along the altitudinal gradient, negative relationships between SLA and LDMC and N_mass were found, and N_mass, P_mass and K_mass correlated with each other positively. Relationship between N_mass and P_mass was stronger than the ones between N_mass and K_mass, and between P_mass and K_mass. The weak and negative relationship between SLA and N_mass might result from trade-offs that limit photosynthesis and water use efficiency along the altitudinal gradient, suggesting many environmental factors of local site being the collective forcing of drivers. Out of our expectations, N_mass and P_mass related very weakly to soil N and P, and no significant relationship between K_mass and soil K was found along elevation. These relationships could be used to predict the productivity of the population with changing environment in this region.