Scaling‐up from leaf to canopy‐aggregate properties in sclerophyll shrub species

Abstract: Plant species vary widely in their average leaf lifespan (LL) and specific leaf area (SLA, leaf area per dry mass). The negative LL–SLA relationship commonly seen among species represents an important evolutionary trade‐off, with higher SLA indicating greater potential for fast growth (higher rate of return on a given investment), but longer LL indicating a longer duration of the revenue stream from that investment. We investigated how these leaf‐economic traits related to aggregate properties of the plant crown. Across 14 Australian sclerophyll shrub species, those with long LL accumulated more leaf mass and leaf area per unit ground area. Light attenuation through their canopies was more severe. Leaf accumulation and light attenuation were more weakly related to SLA than to LL. The greater accumulation of foliage in species with longer LL and lower SLA may counterbalance their generally lower photosynthetic rates and light‐capture areas per gram of leaf.     

不同沙丘生境主要植物比叶面积和叶干物质含量的比较

研究了生长在不同沙丘生境中 (流动沙丘 ,半固定沙丘和固定沙丘 ) 2 0个植物种 (10个 1年生植物种和 10个多年生植物种 )的比叶面积 (SL A)和叶干物质含量 (L DMC)的变化 ,并且分析了各个沙丘生境的土壤养分特征。结果表明 ,各个植物种的平均 SL A和 L DMC在植物种之间差异显著 ;多数在两种或 3种沙丘生境均有分布的植物其 SL A在不同沙丘生境之间差异显著 ,但是仅有 6个植物种的 L DMC在不同沙丘生境之间表现出差异 (p<0 .0 5 )。与许多研究结果类似 ,1年生植物的 SL A显著大于多年生植物的 SL A,而且两者之间 L DMC存在一定的差异。 1年生植物 SL A和 L DMC之间相关性不显著 ,但多年生植物SL A和 L DMC之间呈显著负相关。综合所有 2 0个植物种可以发现 ,SL A增大时 ,L DMC有下降的趋势     

Irradiance, temperature and rainfall influence leaf dark respiration in woody plants: evidence from comparisons across 20 sites

Leaf dark respiration (R) is one of the most fundamental physiological processes in plants and is a major component of terrestrial CO2 input to the atmosphere. Still, it is unclear how predictably species vary in R along broad climate gradients. Data for R and other key leaf traits were compiled for 208 woody species from 20 sites around the world. We quantified relationships between R and site climate, and climate-related variation in relationships between R and other leaf traits. Species at higher-irradiance sites had higher mean R at a given leaf N concentration, specific leaf area (SLA), photosynthetic capacity (Amass) or leaf lifespan than species at lower-irradiance sites. Species at lower-rainfall sites had higher mean R at a given SLA or Amass than species at higher-rainfall sites. On average, estimated field rates of R were higher at warmer sites, while no trend with site temperature was seen when R was adjusted to a standard measurement temperature. Our findings should prove useful for modelling plant nutrient and carbon budgets, and for modelling vegetation shifts with climate change.     

Is Mass‐based Metabolism Rate Proportional to Surface Area in Plant Leaves? A Data Re‐analysis

We re-analyzed two large published databases on leaf traits of plant species from seven different biomes, and determined the scaling relationship between leaf metabolism rate (mass-based photosynthesis capacity, Amass, and mass-based dark respiration, Rdmass) and specific leaf area (SLA) across biomes, using a standardized major axis (SMA) method. Overall pooled data produced a scaling exponent of 1.33 for the relationship between Amass and SLA, significantly larger than 1.0; and 1.04 between Rdmass and SLA. The scaling exponent of the relationship between Amass and SLA ranged between 1.23 (in tropical forest) and 1.66 (in alpine biome), and it was significantly larger in alpine (1.66) and grass/meadow (1.52) biomes than in tropical forest (1.23) and wetland (1.27). The exponent of the relationship between Rdmass and SLA, however,was much smaller in wetland (1.05) than in temperate forest (1.29) and tropical rainforest (1.65). In general, the predicated universal scaling relationship that the mass-based metabolism rate should be proportional to surface area in organisms is not applicable at the leaf-level in plants. Rather, the large slope difference of the relationship between leaf metabolism rate and SLA found among biomes indicates that the strength of the selective forces driving the scaling relationship is different among the biomes. The result basically suggests the importance of increasing SLA to plant carbon gain in stressful environments and to carbon loss in favorable habitats, and therefore has an important implication for survival strategies of plants in different biomes.     

着生位置对水曲柳小叶性状变异及性状间相关性的影响

复叶植物相比单叶植物更具生长优势,但复叶内部小叶性状及其相关关系是否受到着生位置影响尚未可知。该研究以东北典型复叶植物水曲柳(Fraxinusmandshurica)为研究对象,测定复叶内部不同着生位置小叶的叶厚(LT)、叶面积(LA)、叶干物质含量(LDMC)、比叶面积(SLA)、叶氮含量(LNC)和叶磷含量(LPC),分析上述6种小叶性状及其生长关系在复叶内部的变异,并分别通过最小显著性差异(LSD)法以及标准化主轴(SMA)法检验着生位置对小叶性状及性状间生长关系是否存在显著影响。结果表明:(1) LT、LA、LDMC和LNC随小叶着生位置级别增加(从复叶顶端至复叶基部)呈减小趋势,但SLA和LPC呈增大趋势。(2)复叶内部, LNC与SLA间以及LT与LDMC间表现为同速生长关系, LT、SLA、LPC 3个性状与LA间, SLA、LNC、LPC 3个性状与LDMC间以及LPC与LT间均表现为异速生长关系。(3)小叶着生位置对LA与LT、SLA、LPC之间的相关关系存在显著影响, LT、SLA与LA的斜率在三级小叶(复叶中部)附近达到最大值, LT、LPC与LA的斜率绝对值在六...     

Stem diameter growth rates in a fire‐prone savanna correlate with photosynthetic rate and branch‐scale biomass allocation,but not specific leaf area

Plant growth rates strongly determine ecosystem productivity and are a central element of plant ecological strategies. For laboratory and glasshouse‐grown seedlings, specific leaf area (SLA; ratio of leaf area to mass) is a key driver of interspecific variation in growth rate (GR). Consequently, SLA is often assumed to drive GR variation in field‐grown adult plants. However, there is an increasing evidence that this is not the general case. This suggests that GR – SLA relationships (and perhaps those for other traits) may vary depending on the age or size of the plants being studied. Here we investigated GR – trait relationships and their size dependence among 17 woody species from an open‐canopy, fire‐prone savanna in northern Australia. We tested the predictions that SLA and stem diameter growth rate would be positively correlated in saplings but unrelated in adults while, in both age classes, faster‐GR species would have higher light‐saturated photosynthetic rate (A_sat), higher leaf nutrient concentrations, higher branch‐scale biomass allocation to leaf versus stem tissues and lower wood density (WD). SLA showed no relationship to stem diameter GR, even in saplings, and the same was true of leaf N and P concentrations, and WD. However, branch‐scale leaf:stem allocation was strongly related to GR in both age groups, as was A_sat. Together, these two traits accounted for up to 80% of interspecific variation in adult GR, and 41% of sapling GR. A_sat is rarely measured in field‐based GR studies, and this is the first report of branch‐scale leaf:stem allocation (analogous to a benefit:cost ratio) in relation to plant growth rate. Our results suggest that we may yet find general trait‐drivers of field growth rates, but SLA will not be one.     

Turnover of plant lineages shapes herbivore phylogenetic beta diversity along ecological gradients

Understanding drivers of biodiversity patterns is of prime importance in this era of severe environmental crisis. More diverse plant communities have been postulated to represent a larger functional trait‐space, more likely to sustain a diverse assembly of herbivore species. Here, we expand this hypothesis to integrate environmental, functional and phylogenetic variation of plant communities as factors explaining the diversity of lepidopteran assemblages along elevation gradients in the Swiss Western Alps. According to expectations, we found that the association between butterflies and their host plants is highly phylogenetically structured. Multiple regression analyses showed the combined effect of climate, functional traits and phylogenetic diversity in structuring butterfly communities. Furthermore, we provide the first evidence that plant phylogenetic beta diversity is the major driver explaining butterfly phylogenetic beta diversity. Along ecological gradients, the bottom up control of herbivore diversity is thus driven by phylogenetically structured turnover of plant traits as well as environmental variables.     

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.     

Contrasting effects of fire frequency on plant traits of three dominant perennial herbs from Chaco Serrano

Fire frequencies are currently increasing in many regions across the world as a result of anthropic activities, affecting ecological processes and plant population dynamics. Fire can generate important changes in soil properties, altering nutrient dynamics and thereby plant growth. Here we analyse fire frequency effects on soil quality and plant traits of three native perennial herbaceous plants (Cologania broussonetii, Desmodium uncinatum and Rhynchosia edulis; Fabaceae) with the capacity for biological N₂ fixation that resprouts and are abundant after fire in Chaco Serrano forests. Based on 22‐year fire history, we assessed plant traits in sites with low and high fire frequencies along with unburned scenarios. We found significantly lower water content, nitrates and electrical conductivity in frequently burned soils. As a result, the three species showed consistently lower leaf area and specific leaf area in both fire frequencies, implying lower growth rates in comparison to unburned sites. However, total leaf biomass was not affected by fire, leaf phosphorus concentration was higher in R. edulis in high fire frequency and leaf N concentration was twice as large in plants growing in sites of high fire frequency in C. broussonetii and R. edulis. Such an increase in N and phosphorus concentrations is likely a result of both their conservative use of resources and their biological N₂ fixation capacity. To our knowledge, this is the first record of such contrasting fire effects observed consistently in three co‐occurring species: while plant growth decreased with fire frequency, leaf nutritional traits remain unchanged or increased in frequently burned sites. Quality‐depleted and drier soils that result from increased fire frequencies may not only affect trait variation at the intraspecific level but can also drive to a homogenization of the plant community, selecting species with particular combinations of morphological and functional traits.     

Leaf water relations during summer water deficit: differential responses in turgor maintenance and variation in leaf structure among different plant communities in south-western Australia

We measured leaf water relations and leaf structural traits of 20 species from three communities growing along a topographical gradient. Our aim was to assess variation in seasonal responses in leaf water status and leaf tissue physiology between sites and among species in response to summer water deficit. Species from a ridge-top heath community showed the greatest reductions in pre-dawn leaf water potentials (Psi(leaf)) and stomatal conductance during summer; species from a valley-floor woodland and a midslope mallee community showed less reductions in these parameters. Heath species also displayed greater seasonal reduction in turgor-loss point (Psi(TLP)) than species from woodland or mallee communities. In general, species that had larger reductions in Psi(leaf) during summer showed significant shifts in either their osmotic potential at full turgor (Psi(pi 100); osmotic adjustment) or in tissue elasticity (epsilon(max)). Psi(pi 100) and epsilon(max) were negatively correlated, during both spring and summer, suggesting a trade-off between these different mechanisms to cope with water stress. Specific leaf area varied greatly among species, and was significantly correlated with seasonal changes in Psi(TLP) and pre-dawn Psi(leaf). These correlations suggest that leaf structure is a prerequisite for cellular mechanisms to be effective in adjusting to water deficit.     

Global meta-analysis shows that relationships of leaf mass per area with species shade tolerance depend on leaf habit and ontogeny

It was predicted that relationships of leaf mass per area (LMA) with juvenile shade tolerance will depend on leaf habit, and on whether species are compared at a common age as young seedlings, or at a common size as saplings. A meta-analysis of 47 comparative studies (372 species) was used to test predictions, and the effect of light environment on this relationship. The LMA of evergreens was positively correlated with shade tolerance, irrespective of ontogeny or light environment. The LMA of young seedlings (相似文献   

温带草地主要优势植物不同器官间功能性状的关联

理解植物各器官间功能性状的关联, 有助于确定控制功能性状的内在机制以及性状间的比例关系。基于内蒙古温带草地19个地点、42种优势草本植物的野外观测, 分析了叶片、茎、生殖器官、细根和粗根间功能性状(N、P含量、N:P、比叶面积、比根长以及叶片和细根的组织密度)的关联。主要结果如下: 在种群和物种水平上, 各器官的N和P含量都显著正相关, 比叶面积与叶片N、P含量和组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系; 而比根长仅在种群水平上与细根的组织密度显著负相关。N、P含量以及N:P在各器官之间一致呈显著正相关, 而比叶面积和比根长没有显著的相关关系。叶片和细根的组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系。非禾草比禾草相应器官(除茎外)的N、P含量高, 但二者茎的N、P含量没有显著的差异; 豆科植物比非豆科植物相应器官的N含量高, 而P含量没有显著的差异。     

Patterns in specific leaf area and the structure of a temperate heath community

Relationships between the distribution and specific leaf area (SLA: leaf area per unit dry mass) of six heath (Ericaceae) species were investigated along an environmental gradient between peat bogs and conifer forest in British Columbia, Canada. I asked whether patterns in SLA could help to identify the processes shaping plant distributional patterns. Specifically, I assessed whether (i) species’ distributions across the environmental gradient are correlated with SLA (ii) relationships between plant distributional patterns and SLA are similar among bogs with different shrub species (iii) intraspecific patterns in SLA parallel interspecific relationships between distributions and SLA, and (iv) intraspecific patterns are environmentally determined. Results showed that distributional patterns were often correlated with SLA; species with lower SLA were more abundant towards the centre of bogs, while species with higher SLA were more abundant in forest. Intraspecific patterns in SLA paralleled distributional patterns across the gradient; individuals located towards the centre of bogs had lower SLA than those growing in forest. A transplantation experiment showed that plants typically altered their SLA according to local environmental conditions. However, one bog showed no relationship between species’ distributions and SLA. This bog lacked the two species with lowest SLA, which typically occurred at the centre of other bogs. In their absence, species with higher SLA that typically occurred in forest increased in abundance towards the centre of the bog, where they obtained lower values of SLA. Therefore, while distributional patterns were often closely associated with SLA, plasticity in SLA was associated with increased breadth of species’ distributions across the gradient. Overall results indicate SLA may serve as a useful proxy for a range of life history traits to help elucidate the processes structuring plant communities.     

Simulation of leaf area development based on dry matter partitioning and specific leaf area for cut chrysanthemum

This work aims to predict time courses of leaf area index (LAI) based on dry matter partitioning into the leaves and on specific leaf area of newly formed leaf biomass (SLA(n)) for year-round cut chrysanthemum crops. In five glasshouse experiments, each consisting of several plant densities and planted throughout the year, periodic destructive measurements were conducted to develop empirical models for partitioning and for SLA(n). Dry matter partitioning into leaves, calculated as incremental leaf dry mass divided by incremental shoot dry mass between two destructive harvests, could be described accurately (R(2 )= 0.93) by a Gompertz function of relative time, R(t). R(t) is 0 at planting date, 1 at the start of short-days, and 2 at final harvest. SLA(n), calculated as the slope of a linear regression between periodic measurements of leaf dry mass (LDM) and LAI, showed a significant linear increase with the inverse of the daily incident photosynthetically active radiation (incident PAR, MJ m(-2 )d(-1)), averaged over the whole growing period, the average glasshouse temperature and plant density (R(2 )= 0.74). The models were validated by two independent experiments and with data from three commercial growers, each with four planting dates. Measured shoot dry mass increase, initial LAI and LDM, plant density, daily temperature and incident PAR were input into the model. Dynamics of LDM and LAI were predicted accurately by the model, although in the last part of the cultivation LAI was often overestimated. The slope of the linear regression of simulated against measured LDM varied between 0.95 and 1.09. For LAI this slope varied between 1.01 and 1.12. The models presented in this study are important for the development of a photosynthesis-driven crop growth model for cut chrysanthemum crops.     

Determinants of some leaf characteristics of Australian mangroves

Leaf characteristics reflecting the size, lifespan (longevity), moisture content (degree of succulence) and complexity of structure of 20 mangrove species were studied over several years at 13 locations along the tropical and subtropical Australian coast. These characteristics were found to fall generally within the ranges of those for woody species from other ecosystems. With the exception of one species, it was found that leaf longevity was related inversely to leaf moisture content, increasing from nearly 6 months in more succulent species to over 2 years in less succulent species. This suggested that more succulent leaves are less complex in their structure because they have less well‐developed ability to compartmentalize salt. There was a tendency also for leaf longevity to increase in species with larger leaves. These findings were consistent with the general view for land plants that leaf longevity is greater in species that have developed tolerance to environmental stress, salt particularly in the case of mangroves. Leaf tissue in such species is more robust or complex and requires greater metabolic resources in its construction; the plant is then advantaged by retaining the tissue for longer periods. Classification of the species considered here, based on their leaf longevity, moisture content and complexity, identified phylogenetically related species groupings that reflected these leaf longevity effects.     

Plasticity in above‐ and belowground resource acquisition traits in response to single and multiple environmental factors in three tree species

Functional trait plasticity is a major component of plant adjustment to environmental stresses. Here, we explore how multiple local environmental gradients in resources required by plants (light, water, and nutrients) and soil disturbance together influence the direction and amplitude of intraspecific changes in leaf and fine root traits that facilitate capture of these resources. We measured population‐level analogous above‐ and belowground traits related to resource acquisition, i.e. “specific leaf area”–“specific root length” (SLA–SRL), and leaf and root N, P, and dry matter content (DMC), on three dominant understory tree species with contrasting carbon and nutrient economics across 15 plots in a temperate forest influenced by burrowing seabirds. We observed similar responses of the three species to the same single environmental influences, but partially species‐specific responses to combinations of influences. The strength of intraspecific above‐ and belowground trait responses appeared unrelated to species resource acquisition strategy. Finally, most analogous leaf and root traits (SLA vs. SRL, and leaf versus root P and DMC) were controlled by contrasting environmental influences. The decoupled responses of above‐ and belowground traits to these multiple environmental factors together with partially species‐specific adjustments suggest complex responses of plant communities to environmental changes, and potentially contrasting feedbacks of plant traits with ecosystem properties. We demonstrate that despite the growing evidence for broadly consistent resource‐acquisition strategies at the whole plant level among species, plants also show partially decoupled, finely tuned strategies between above‐ and belowground parts at the intraspecific level in response to their environment. This decoupling within species suggests a need for many species‐centred ecological theories on how plants respond to their environments (e.g. competitive/stress‐tolerant/ruderal and response‐effect trait frameworks) to be adapted to account for distinct plant‐environment interactions among distinct individuals of the same species and parts of the same individual.