Leaf Life Span Research Articles

Effect of Nitrogen on the Dynamics of Leaf Population Demography in Whole Plants ofWedelia trilobata

Premise of research. More detailed studies are required to evaluate the distribution of N among leaves and the whole-plant carbon gain in the absence of a light gradient. This study assessed the effect of leaf age on photosynthetic capacity and leaf N content simultaneously with the calculation of leaf demographic parameters in plants of Wedelia trilobata growing horizontally at three levels of nitrogen availability.Methodology. Leaf production, leaf death rates, leaf life span, and the decline in maximum photosynthetic rate with age were measured. With these data, the structure of leaf age population in whole plants was constructed, and their effect on the distribution of N among leaves and the whole-plant carbon gain was projected.Pivotal results. In all N treatments, leaf age regulated the photosynthetic capacity along the life of the leaf and established a nonuniform distribution of leaf N content in the leaves present in the plant. Leaf age structure showed that with the increase in N availability, the leaf population tends to be younger. The major contribution of carbon took place in the early life of the leaf, but the relative importance of the older leaves was different among treatments.Conclusions. The use of traditional demographic approaches allowed the scaling up of leaf carbon gain from leaf to whole plant in a species with horizontally oriented branches and demonstrated that an optimal leaf age structure at different N availabilities may be important to maximize whole-plant carbon gain under the same light condition.

Evergreen and Deciduous Ferns of the Coast Redwood Forest

Abstract The understory of California's coast redwood forests boasts an abundance of ferns, half of which are drought deciduous. Despite their ecological importance, little is known about the functional differences between deciduous and perennial ferns. This study explored morphological and physiological leaf traits of an assortment of coast redwood forest fern species sampled from the southern, drier extent of the ecosystem, to determine if deciduous species are less drought tolerant than co-occurring evergreen species because of their shorter leaf lifespan. In mid-summer, all ferns were well hydrated with water potentials above −1 MPa. Although the deciduous ferns were more vulnerable to hydraulic dysfunction by embolism, it is likely that all species experienced similarly low degrees of embolism in situ, as inferred from mid-day water potential measurements. Despite their similar water relations when water was not limiting, we observed that deciduous ferns had thinner pinnae because they avoid the late...

The incidence of low phosphorus soils in Australia

Low phosphorus (P) soils have been described as a widespread characteristic of the Australian continent and associated with sclerophyll leaf traits. In that context we ask: what proportion of the continent is low-P and how much does this vary between regions? 9234 locations sampled for soil total P from the Australian National Site Soil Data Collation were analysed. In order to make some adjustment for uneven spatial sampling we area-weighted the data using subregions from the Interim Bioregionalisation of Australia. Topsoil total P concentrations ≤100 mg kg−1 were widespread, but not a majority of the continent (estimated 25 %). The western Monsoon Tropics (65 %), southwestern Australia (50 %), and southeast South Australia (38 %) were estimated to have larger fractions of the sampled landscape ≤100 mg kg−1 than eastern Australia (13.5 %), but not a lower range of values. Total P values across the continent included a large fraction (33 %) in the range 101–250 mg kg−1. Continent-wide soil P levels low enough to favour long leaf lifespans for nutrient conservation and a variety of sclerophyll traits were widespread. It is time to move away from the qualitative dichotomies between low- and high-P that have characterised discussion of Australian vegetation, to a more quantitative view.

Constraints of cold and shade on the phenology of spring ephemeral herb species

SummarySpring ephemeral herb species in temperate deciduous forests are active above‐ground only briefly each year. This study tested experimentally how two countervailing constraints – cold and darkness – influence the phenology of six spring herb species.Dormancy of underground structures, maintained by cold temperatures in a growth chamber, was broken at six 25‐day intervals from January or February to June in two consecutive years. Upon emergence, survival and flowering were measured on cohorts grown outdoors. Shade cloth was added at the time of normal canopy closure.Cardamine concatenata,Dicentra cucullaria,Erythronium albidumandTrillium recurvatumhad no or low 2‐year survival in the two or three earliest cohorts and no or low survival in the latest cohort, relative to their natural cohort.Allium canadenseandClaytonia virginicahad survival in all cohorts. Flowering never occurred in the first two or three cohorts for three species and never occurred or declined in later cohorts in all species.Despite widely differing emergence dates, senescence was completed within a 40‐day period soon after shade was imposed for all cohorts for all species. Consequently, leaf life span became shorter as date of emergence was delayed among cohorts.In general, the brief growth period of spring herb species is an adaptation to avoid winter cold and late‐spring canopy shade. These constraints are species‐specific and differ for survival and flowering for some species.Claytonia virginicais the most tolerant among the species to a wider range of conditions.Synthesis. Knowing that cold and shade constrain a plant's non‐dormant period is important because of the significant role plant phenology plays in responses to climate change.

Negative legacy effects of rainfall and nitrogen amendment on leaf lifespan of steppe species

Negative legacy effects of rainfall and nitrogen amendment on leaf lifespan of steppe species

Morphogenetic and structural characteristics of clones of elephant grass managed under intermittent stocking

This work was carried out to evaluate the morphogenetic and structural characteristics of basal and aerial tillers of two dwarf elephant grass clones (BRS Kurumi and CNPGL 00-1-3) managed under intermittent stocking in six grazing cycles. A completely randomized experimental design with three replications (paddocks) in split-split-plot arrangements was used. The clones were allocated to the plots, tiller classes were assigned to the subplots and grazing cycles to sub subplots. Higher values for basal tillers than aerial tillers were seen for the following characteristics: leaf elongation rate (12.8 and 5.1 cm/tiller/day), leaf appearance rate (0.26 and 0.19 leaves/tiller/day), stem elongation rate (0.38 and 0.16 cm/tiller/day), senescence rate (0.98 and 0.47 cm/tiller/day), total number of leaves (9.3 and 7.1 leaves/ tiller), number of live leaves (7.7 and 5.8 leaves/tiller) and final length of leaf blades (33.5 and 20.0 cm). Phyllochron was lower for basal (4.0 days/leaf) than aerial tillers (5.5 days/leaf). The leaf life span increased with the advance of the grazing cycles, averaging 31.2 days. The tiller density increased with the advance of the grazing cycles showing an average increase of 167% of aerial tillers and 62% of basal tillers for both clones. The morphogenetic and structural characteristics of dwarf clones were influenced jointly by the clones and the availability of the environmental factors of growth during the spring and summer. The high leaf elongation rates, associated with high leaf appearance rate, reveal the potential of high production dry matter of leaves and restoration of leaf area after grazing.

Are inter- and intraspecific variations of sapling crown traits consistent with a strategy promoting light capture in tropical moist forest?

Background and Aims Morphological variation in light-foraging strategies potentially plays important roles in efficient light utilization and carbon assimilation in spatially and temporally heterogeneous environments such as tropical moist forest understorey. By considering a suite of morphological traits at various hierarchical scales, we examined the functional significance of crown shape diversity and plasticity in response to canopy openness. Methods We conducted a field comparative study in French Guiana among tree saplings of 14 co-occurring species differing in light-niche optimum and breadth. Each leaf, axis or crown functional trait was characterized by a median value and a degree of plasticity expressed under contrasting light regimes. Key Results We found divergent patterns between shade-tolerant and heliophilic species on the one hand and between shade and sun plants on the other. Across species, multiple regression analysis showed that relative crown depth was positively correlated with leaf lifespan and not correlated with crown vertical growth rate. Within species displaying a reduction in crown depth in the shade, we observed that crown depth was limited by reduced crown vertical growth rate and not by accelerated leaf or branch shedding. In addition, the study provides contrasting examples of morphological multilevel plastic responses, which allow the maintenance of efficient foliage and enable effective whole-plant light capture in shaded conditions under a moderate vertical light gradient. Conclusions This result suggests that plastic adjustment of relative crown depth does not reflect a strategy maximizing light capture efficiency. Integrating and scaling-up leaf-level dynamics to shoot- and crown-level helps to interpret in functional and adaptive terms inter- and intraspecific patterns of crown traits and to better understand the mechanism of shade tolerance.

Production of leaf wax n-alkanes across a tropical forest elevation transect

Waxy compounds form the boundary layer of the living leaf and contribute biomarkers to soils, and lake and marine sediments. Cataloging the variation in leaf wax traits between species and across environmental gradients may contribute to the understanding of plant functional processes in modern ecosystems, as well as to calibration efforts supporting reconstruction of past ecosystems and environments from the sedimentary archives of leaf wax biomarkers. Towards these goals, we have surveyed the distributions of leaf wax n-alkanes in trees from the lowland tropical rainforest (TR) and montane cloud forest (TMCF) of Perú. Molecular abundances were quantified via gas chromatography flame ionization detection (GC-FID) for 632 individuals, 152 species, 99 genera and 51 families across 9 forest plots spanning 0.2–3.6km elevation. We found the expected abundance distributions; for example, they were dominated by long chain, odd numbered n-alkanes, especially C29 and C31. New observations included a tendency to increasing total alkane concentration at higher elevation. We propose that the well known leaf economic strategy to increase leaf mass per unit area with elevation, provides a theoretical basis for understanding the increase in leaf wax n-alkane abundance with elevation: we infer an increased investment in foliar defense associated with increased leaf lifespan and in response to environmental pressures including cloud immersion and declining temperature. Furthermore, we combined measurements of n-alkane concentration with estimates of forest productivity to provide new ways to quantify ecosystem-scale forest alkane productivity. We introduce a new concept of n-alkane net primary productivity (NPPalk; the product of alkane concentration and leaf NPP) and find that alkane productivity estimates range from 300 to 5000g C/ha/yr, associated with ecological and environmental changes across the elevation profile.

Improved representation of plant functional types and physiology in the Joint UK Land Environment Simulator (JULES v4.2) using plant trait information

Abstract. Dynamic global vegetation models are used to predict the response of vegetation to climate change. They are essential for planning ecosystem management, understanding carbon cycle–climate feedbacks, and evaluating the potential impacts of climate change on global ecosystems. JULES (the Joint UK Land Environment Simulator) represents terrestrial processes in the UK Hadley Centre family of models and in the first generation UK Earth System Model. Previously, JULES represented five plant functional types (PFTs): broadleaf trees, needle-leaf trees, C3 and C4 grasses, and shrubs. This study addresses three developments in JULES. First, trees and shrubs were split into deciduous and evergreen PFTs to better represent the range of leaf life spans and metabolic capacities that exists in nature. Second, we distinguished between temperate and tropical broadleaf evergreen trees. These first two changes result in a new set of nine PFTs: tropical and temperate broadleaf evergreen trees, broadleaf deciduous trees, needle-leaf evergreen and deciduous trees, C3 and C4 grasses, and evergreen and deciduous shrubs. Third, using data from the TRY database, we updated the relationship between leaf nitrogen and the maximum rate of carboxylation of Rubisco (Vcmax), and updated the leaf turnover and growth rates to include a trade-off between leaf life span and leaf mass per unit area.Overall, the simulation of gross and net primary productivity (GPP and NPP, respectively) is improved with the nine PFTs when compared to FLUXNET sites, a global GPP data set based on FLUXNET, and MODIS NPP. Compared to the standard five PFTs, the new nine PFTs simulate a higher GPP and NPP, with the exception of C3 grasses in cold environments and C4 grasses that were previously over-productive. On a biome scale, GPP is improved for all eight biomes evaluated and NPP is improved for most biomes – the exceptions being the tropical forests, savannahs, and extratropical mixed forests where simulated NPP is too high. With the new PFTs, the global present-day GPP and NPP are 128 and 62 Pg C year−1, respectively. We conclude that the inclusion of trait-based data and the evergreen/deciduous distinction has substantially improved productivity fluxes in JULES, in particular the representation of GPP. These developments increase the realism of JULES, enabling higher confidence in simulations of vegetation dynamics and carbon storage.

Overwintering evergreen oaks reverse typical relationships between leaf traits in a species spectrum.

The leaf economics spectrum has given us a fundamental understanding of the species variations in leaf variables. Across plant species, tight correlations among leaf mass per area (LMA), mass-based nitrogen (Nm) and photosynthetic rate (Am) and leaf lifespan have been well known as trade-offs in leaf carbon economy. However, the regional or biome-level correlations may not be necessary to correspond with the global-scale analysis. Here, we show that almost all leaf variables in overwintering evergreen oaks in Japan were relatively well included within the evergreen-broadleaved trees in worldwide temperate forests, but Nm was more consistent with that in deciduous broadleaved trees. Contrary to the universal correlations, the correlation between Am and Nm among the evergreen oaks was negative and the correlation between Am and LMA disappeared. The unique performance was due to specific nitrogen allocation within leaves, i.e. the evergreen oaks with later leaf maturation had lower Nm but higher nitrogen allocation to photosynthetic enzymes within leaves, to enhance carbon gain against the delayed leaf maturation and the shortened photosynthetic period due to cold winters. Our data demonstrate that correlations between leaf variables in a local scale are occasionally different from averaged global-scale datasets, because of the constraints in each biome.

Blade life span, structural investment, and nutrient allocation in giant kelp.

The turnover of plant biomass largely determines the amount of energy flowing through an ecosystem and understanding the processes that regulate turnover has been of interest to ecologists for decades. Leaf life span theory has proven useful in explaining patterns of leaf turnover in relation to resource availability, but the predictions of this theory have not been tested for macroalgae. We measured blade life span, size, thickness, nitrogen content, pigment content, and maximum photosynthetic rate (P max) in the giant kelp (Macrocystis pyrifera) along a strong resource (light) gradient to test whether the predictions of leaf life span theory applied to this alga. We found that shorter blade life spans and larger blade areas were associated with increased light availability. In addition, nitrogen and P max decreased with blade age, and their decrease was greater in shorter lived blades. These observations are generally consistent with patterns observed for higher plants and the prevailing theory of leaf life span. By contrast, variation observed in pigments of giant kelp was inconsistent with that predicted by leaf life span theory, as blades growing in the most heavily shaded portion of the forest had the lowest chlorophyll content. This result may reflect the dual role of macroalgal blades in carbon fixation and nutrient absorption and the ability of giant kelp to modify blade physiology to optimize the acquisition of light and nutrients. Thus, the marine environment may place demands on resource acquisition and allocation that have not been previously considered with respect to leaf life span optimization.

Morphogenesis in pastures of Coastcross-1 and Tifton 85 mixed with forage peanut, submitted to cutting management

The objective of this study was to evaluate the effect of the presence of forage peanut (Arachis pintoi Krap. and Greg.) on the morphogenesis characteristics of two cultivars of Cynodon (Tifton 85 and Coastcross-1). The experimental design was factorial (three factors), in randomized blocks, having as factors the cultivars (2), the occupancy area of forage peanut (4) and the seasons (3), with three replications, established in plots. There were three assessments during the study, in spring, summer and autumn, in which the total number of tillers, the culm and leaf elongation, the senescence rate and leaf emergence, the phyllochron, the leaf lifespan, the leaf number and the height of culm and canopy were evaluated. The number of green leaves, number of elongating leaves and senescence rate were similar among cultivars, but cv. Coastcross-1 showed higher number of expanded leaves and leaf emergence rate, and lower phyllochron and leaf lifespan. We observed lower rates of senescence and higher leaf emergence in spring, and lower rates of leaf elongation in autumn. The increasing participation of forage peanut in the pastures did not affect the calculated morphogenetic variables, but decreased the number of grass tillers. A lower average daily thermal accumulation decreased the development of both grasses in this study, with a more pronounced effect in cv. Tifton 85. The Coastcross-1 cultivar has higher elongation rate and leaf emergence, coupled with lower phyllochron and leaf lifespan, indicating a need for shorter rest periods when compared to cv. Tifton 85.

Variations in leaf functional traits among plant species grouped by growth and leaf types in Zhenjiang, China

Leaf functional traits are adaptations that enable plants to live under various environmental conditions. This study aims to determine the differences in leaf functional traits among plants grouped by growth habit, leaf life span, leaf lifestyle, leaf form, and origin. Specific leaf area (SLA) of perennial or evergreen species was lower than that of annual or deciduous species because longer-lived leaves of perennial or evergreen species require more investment in structural integrity and/or defense against disturbances, especially with any resource constraint. SLA of large individuals was lower than that of small individuals. The low SLA in large individuals can improve their response to changing light and water conditions because increasing plant height is advantageous for light competition, but it can also impose a cost in terms of structural support and water transport. Petioles of plants with compound leaves were significantly longer than those of simple leaves because branching is expensive in terms of gaining height. SLA of plants increased with increasing invasiveness accordingly, and SLA of invasive plants was higher than that of their native congeners because invasive plants should invest more biomass on leaf growth rather than leaf structures per unit area to achieve a higher growth rate. Overall, variation in leaf functional traits among different groups may play an adaptive role in the successful survival of plants under diverse environments because leaf functional traits can lead to pronounced effects on leaf function, especially the acquisition and use of light. Plant species with different growth and leaf traits balance resource acquisition and leaf construction to minimize trade-offs and achieve fitness advantages in their natural habitat.

A comprehensive analysis of mechanical and morphological traits in temperate and tropical seagrass species

Knowledge of plant mechanical traits is important in understanding how plants resistabiotic and biotic forces and in explaining ecological strategies such as leaf lifespan. To date,these traits have not been systematically evaluated in seagrasses. We analysed mechanical(breaking force and tensile strength) and associated traits (thickness, width, length, fibre content,mass area, and lifespan) of leaves in 22 seagrass species (around one-third of all known seagrassspecies) to examine (1) the inter-specific variation of these traits in relation to growth form andbioregions, (2) the contribution of morphology to leaf breaking force, (3) how breaking force scalesto leaf dimensions, and (4) how mechanical and structural traits correlate to leaf longevity. We alsocompared our seagrass dataset with terrestrial plant databases to examine similarities betweenthem. Large variation in leaf breaking force was found among seagrass species but, on average,temperate species resisted higher forces than tropical species. Variation in leaf breaking force waslargely explained by differences in leaf width rather than thickness, likely due to the benefits inleaf reconfiguration and light interception. Species of large dimensions (long leaves) typically hadhigh leaf breaking force, plausibly to tolerate the drag forces they may experience, which are proportionalto the leaf area. Leaves of long-lived species typically had high mass per leaf area andfibre content and they supported high breaking forces. Compared to terrestrial plants, seagrassesare short-lived species with moderately strong fibre-reinforced leaves, which probably evolved towithstand the hydrodynamic forces occurring in the sea, and in response to other environmentalfactors. Overall, our analysis provides new insights into the physical performance of seagrasses inthe marine environment.

To recycle or steal? Nutrient resorption in Australian and Brazilian mistletoes from three low‐phosphorus sites

Resorption is the process by which nutrients are withdrawn from leaves prior to leaf fall. Mistletoes are generally thought not to rely on nutrient resorption; being xylem‐tapping parasites, they instead derive the nutrients required for new growth from their host plant, at little or no cost. We measured nutrient (N, P, K, Ca, Mg) resorption in 18 parasitic mistletoe–host species pairs distributed across three sites with notably low‐P soil, also quantifying relationships with leaf lifespan (LL) and specific leaf area (SLA). There was little or no evidence of N, Ca or Mg resorption. By contrast, on average ∼30% of P and ∼20% of K were resorbed prior to leaf fall. Longer LL in mistletoes was associated with lower N and P concentrations in mistletoes and in host leaves. We provide evidence that, even though mistletoes are relatively inefficient in terms of nutrient resorption compared to non‐parasite species, on low‐P soils their ecological and evolutionary strategies for conserving phosphorous involve modulation of both leaf lifespan and P concentration in senesced leaves.

Leaf lifespan is positively correlated with periods of leaf production and reproduction in 49 herb and shrub species.

Leaf life span and plant phenology are central elements in strategies for plant carbon gain and nutrient conservation. Although few studies have found that leaf life span correlate with the patterns of leaf dynamics and reproductive output, but there have not been sufficient conclusive tests for relationships between leaf life span and plant phenological traits, the forms and strengths of such relationships are poorly understood. This study was conducted with 49 herb and shrub species collected from the eastern portion of the Tibetan Plateau and grown together in a common garden setting. We investigated leaf life span, the periods of leaf production and death, the time lag between leaf production and death, and the period of plant reproduction (i.e., flowering and fruiting). Interspecific relationships of leaf life span with leaf dynamics and reproduction period were determined. Leaf production period was far longer than leaf death period and largely reflected the interspecific variation of leaf life span. Moreover, leaf life span was positively correlated with the length of reproduction (i.e., flowering and fruiting) period. These relationships were generally consistent across different subgroups of species (herbs vs. shrubs) and indicate potentially widely applicable relationships between LLS and aboveground phenology. We concluded that leaf life span is associated not simply with the dynamics of the leaf itself but with reproduction period. The results demonstrate a plant trade‐off in resource allocation between production and reproduction and a coordinated arrangement of leaves, flowers, and fruits in their time investment. Our results provide insight into the relationship between leaf life span and plant phenology.

Is a leaf life span enough to display changes on developmental instability and nitrogen after simulated herbivory?

Herbivory is a main source of plant damage and injured plants might present decrements in nutrients, delayed growth and low reproductive outputs. Therefore, herbivory can be considered a stressful agent to plants. In this study, we investigated short-term changes in stress and nutrient levels of the invasive plant species Tithonia diversifolia (Asteraceae) after simulated herbivory. Parameters such as leaf fluctuating asymmetry (FA, a measure of plant stress, also known as developmental instability) and nitrogen levels were compared between control and treated plants reared in a greenhouse. We expected high levels of FA and significant changes in nitrogen in injured leaves. FA was assessed by measuring the right and left sides of leaves, from the leaf edge to the midrib, at the middle point of the leaves; nitrogen was evaluated through the Kjeldahl method. Though non-significant, at the end of the study, injured leaves were 22% more asymmetric than control leaves, and before-after comparisons revealed that FA increased by 33% in leaves after leaf damage. In addition, FA was positively and significantly related to leaf area loss. Nitrogen did not present changes after simulated herbivory. The control group showed non-significant changes in FA and nitrogen. FA was concluded to be a rapid estimator of plant stress following leaf damage, as during its short lifespan (45days), leaves displayed tentatively increased developmental instability. We consider that leaf damage is a predictor of plant developmental instability and that FA can be used to detect and compare stress levels in plants after herbivory damage.

Do cytokinins, volatile isoprenoids and carotenoids synergically delay leaf senescence?

Do cytokinins, volatile isoprenoids and carotenoids synergically delay leaf senescence?

Canopy leaf area of a mature evergreen Eucalyptus woodland does not respond to elevated atmospheric [CO2] but tracks water availability.

Canopy leaf area, quantified by the leaf area index (L), is a crucial driver of forest productivity, water use and energy balance. Because L responds to environmental drivers, it can represent an important feedback to climate change, but its responses to rising atmospheric [CO2] and water availability of forests have been poorly quantified. We studied canopy leaf area dynamics for 28 months in a native evergreen Eucalyptus woodland exposed to free-air CO2 enrichment (the EucFACE experiment), in a subtropical climate where water limitation is common. We hypothesized that, because of expected stimulation of productivity and water-use efficiency, L should increase with elevated [CO2]. We estimated L from diffuse canopy transmittance, and measured monthly leaf litter production. Contrary to expectation, L did not respond to elevated [CO2]. We found that L varied between 1.10 and 2.20 across the study period. The dynamics of L showed a quick increase after heavy rainfall and a steady decrease during periods of low rainfall. Leaf litter production was correlated to changes in L, both during periods of decreasing L (when no leaf growth occurred) and during periods of increasing L (active shedding of old foliage when new leaf growth occurred). Leaf lifespan, estimated from mean L and total annual litter production, was up to 2 months longer under elevated [CO2] (1.18 vs. 1.01 years; P = 0.05). Our main finding that L was not responsive to elevated CO2 is consistent with other forest FACE studies, but contrasts with the positive response of L commonly predicted by many ecosystem models.

Convergent production and tolerance among 107 woody species and divergent production between shrubs and trees.

Green leaves face two fundamental challenges (i.e., carbon fixation and stress tolerance) during their lifespan. However, the relationships between leaf production potential and leaf tolerance potential have not been explicitly tested with a broad range of plant species in the same environment. To do so, we conducted a field investigation based on 107 woody plants grown in a common garden and complementary laboratory measurements. The values, as measured by a chlorophyll meter, were significantly related to the direct measurements of chlorophyll content on a leaf area basis. Area-based chlorophyll content was positively correlated with root surface area, whole-plant biomass, leaf mass per area (LMA), and force to punch. Additionally, LMA had a positive correlation with force to punch. Shrubs had a higher leaf chlorophyll content than trees; however, shrubs and trees exhibited a similar leaf lifespan, force to punch, and LMA. These findings suggest that the production potential of leaves and their tolerance to stresses may be convergent in woody species and that the leaf production potential may differ between shrubs and trees. This study highlights the possibility that functional convergence and divergence might be linked to long-term selection pressures and genetic constraints.