Lower Leaf Mass Per Area Research Articles

Adjustments and coordination of hydraulic, leaf and stem traits along a water availability gradient.

Trait variability in space and time allows plants to adjust to changing environmental conditions. However, we know little about how this variability is distributed and coordinated at different organizational levels. For six dominant tree species in northeastern Spain (three Fagaceae and three Pinaceae) we quantified the inter- and intraspecific variability of a set of traits along a water availability gradient. We measured leaf mass per area (LMA), leaf nitrogen (N) concentration, carbon isotope composition in leaves (δ13 C), stem wood density, the Huber value (Hv, the ratio of cross-sectional sapwood area to leaf area), sapwood-specific and leaf-specific stem hydraulic conductivity, vulnerability to xylem embolism (P50 ) and the turgor loss point (Ptlp ). Differences between families explained the largest amount of variability for most traits, although intraspecific variability was also relevant. Species occupying wetter sites showed higher N, P50 and Ptlp , and lower LMA, δ13 C and Hv. However, when trait relationships with water availability were assessed within species they held only for Hv and Ptlp . Overall, our results indicate that intraspecific adjustments along the water availability gradient relied primarily on changes in resource allocation between sapwood and leaf area and in leaf water relations.

Convergence of ecophysiological traits drives floristic composition of early lineage vascular plants in a tropical forest floor.

Tropical understorey plant communities are highly diverse and characterized by variable resource availability, especially light. Plants in these competitive environments must carefully partition resources to ensure ecological and evolutionary success. One mechanism of effective resource partitioning is the optimization of functional traits to enhance competition in highly heterogeneous habitats. Here, we surveyed the ecophysiology of two early lineage vascular plant groups from a tropical forest understorey: Selaginella (a diverse lineage of lycophytes) and ferns. In a lowland rain forest in Costa Rica, we measured a suite of functional traits from seven species of Selaginella and six fern species. We evaluated species microclimate and habitat; several photosynthetic parameters; carbon, nitrogen and phosphorus content; chlorophyll concentration; leaf mass per area (LMA); and stomatal size and density. We then compare these two plant lineages and search for relationships between key functional parameters that already exist on a global scale for angiosperms. Convergence of trait function filtered Selaginella species into different habitats, with species in heavily shaded environments having higher chlorophyll concentrations and lower light compensation points compared with open habitats. Alternatively, lower foliar nitrogen and higher stomatal densities were detected in species occupying these open habitats. Selaginella species had denser and smaller stomata, lower LMA and lower foliar nutrient content than ferns, revealing how these plant groups optimize ecophysiological function differently in tropical forest floors. Our findings add key pieces of missing evidence to global explorations of trait patterns that define vascular plant form and function, which largely focus on seed plants. Broadly predictable functional trait relationships were detected across both Selaginella and ferns, similar to those of seed plants. However, evolutionary canalization of microphyll leaf development appears to have driven contrasting, yet successful, ecophysiological strategies for two coexisting lineages of extant homosporous vascular plants.

Landscape variation in plant leaf flammability is driven by leaf traits responding to environmental gradients

AbstractLandscape differences in environmental conditions select for divergences among plant species in strategically important leaf traits such as leaf mass per area (LMA) and leaf area (LA). Interspecific variation in some of these same leaf traits has been associated to varying degrees with differences among species in leaf flammability, including the attributes ignitibility, sustainability, and combustibility. Yet, how environmentally selected variation in leaf traits drives variation in leaf flammability at landscape scales remains largely unknown. Here, we compared leaf traits and flammability attributes between species of sheltered forest vegetation (low light, moist habitat) and plant species of exposed woodland vegetation (high light, dry habitat) in a fire‐prone landscape of south‐eastern Australia. We found that leaves of sheltered forest species were significantly more flammable via both higher ignitibility and combustibility compared with exposed woodland species. These significant differences in leaf ignitibility and combustibility were underpinned by sheltered forest species having leaves with significantly larger LA and lower LMA compared with exposed woodland species. Further, multiple regression analyses revealed that both LA and LMA were significantly and uniquely related to faster time to ignition (TTI; ignitibility) and higher mean mass loss rate (combustibility). Most notably, although significantly higher fuel moisture content (FMC) of leaves of sheltered forest species significantly lengthened TTI, the lower LMA of these species played a more critical role in reducing TTI, with low LMA explaining more unique variation (partial r2 = 0.78) in high leaf ignitibility than low FMC (partial r2 = 0.49). Our findings provide the first evidence that landscape‐scale variation in leaf flammability is tightly coordinated with the primary strategic response of the leaf traits LMA and LA to an environmental gradient. Furthermore, projections for increasing wildfire frequency and intensity in the region will likely allow wildfires to overcome the once protective nature provided by topography to sheltered forest vegetation, which means that higher leaf flammability in sheltered forest species has the potential to exacerbate the effects of changing weather conditions to place sheltered forest habitat, their plants, and their animals, at even higher risk of catastrophic wildfire.

Leaf thermotolerance in tropical trees from a seasonally dry climate varies along the slow-fast resource acquisition spectrum

Knowledge of the upper limits of temperature tolerance is essential to understand how tropical trees will respond to global warming. We quantified leaf thermotolerance in 41 tree species growing in a seasonally dry tropical region of the Indian subcontinent to examine: (1) differences between evergreen and deciduous species; (2) relationships with leaf mass per area (LMA) and leaf size; and, (3) seasonal variation in thermotolerance. Thermotolerance ranged from 45.5 °C to 50.5 °C among species, was higher for evergreen than deciduous species, and was negatively related to a continuous estimate of deciduousness. Species with higher LMA had higher thermotolerance, but we did not detect any relationship between leaf size and thermotolerance. Seasonal changes in thermotolerance varied among species implying that species’ capacity to acclimate may differ. Thermal safety margins, the difference between thermotolerance and maximum habitat temperatures indicate that most species may be highly vulnerable to future warming. Overall our results show that deciduous, and fast growing species with low LMA are likely to be more negatively affected by global warming. This differential vulnerability may lead to directional changes in composition in dry tropical forests, and such changes could alter vegetation-atmosphere feedbacks and further exacerbate global warming.

Effects of structural complexity on within-canopy light environments and leaf traits in a northern mixed deciduous forest.

Canopy structure influences forest productivity through its effects on the distribution of radiation and the light-induced changes in leaf physiological traits. Due to the difficulty of accessing and measuring forest canopies, few field-based studies have quantitatively linked these divergent scales of canopy functioning. The objective of our study was to investigate how canopy structure affects light profiles within a forest canopy and whether leaves of mature trees adjust morphologically and biochemically to the light environments characteristic of canopies with different structural complexity. We used a combination of light detection and ranging (LiDAR) data and hemispherical photographs to quantify canopy structure and light environments, respectively, and a telescoping pole to sample leaves. Leaf mass per area (LMA), nitrogen on an area basis (Narea) and chlorophyll on a mass basis (Chlmass) were measured in red maple (Acer rubrum), american beech (Fagus grandifolia), white pine (Pinus strobus), and northern red oak (Quercus rubra) at different heights in plots with similar leaf area index but contrasting canopy complexity (rugosity). We found that more complex canopies had greater porosity and reduced light variability in the midcanopy while total light interception was unchanged relative to less complex canopies. Leaf phenotypes of F. grandifolia, Q. rubra and P. strobus were more sun-acclimated in the midstory of structurally complex canopies while leaf phenotypes of A. rubrum were more shade-acclimated (lower LMA) in the upper canopy of more complex stands, despite no differences in total light interception. Broadleaf species showed further differences in acclimation with increased Narea and reduced Chlmass in leaves with higher LMA, while P. strobus showed no change in Narea and Chlmass with higher LMA. Our results provide new insight on how light distribution and leaf acclimation in mature trees might be altered when natural and anthropogenic disturbances cause structural changes in the canopy.

Differences in ozone sensitivity among woody species are related to leaf morphology and antioxidant levels.

Ozone (O3) sensitivity varies greatly among plant species. Leaf traits such as stomatal conductance, antioxidant capacity and leaf morphology and anatomy may play important roles in controlling this variation, but the relative contributions of each trait remain elusive. In this study, we examined the differences in O3 sensitivity among 29 deciduous and evergreen woody species used for urban greening in China in an open-top chamber experiment. Elevated O3 caused visible injury and reductions in net photosynthesis, and these effects differed significantly among species. The deciduous species Sorbaria sorbifolia, Hibiscus syriacus and Fraxinus chinensis were the most sensitive, while evergreen species ranked among the most tolerant. O3 sensitivity was linked to both low leaf mass per area (LMA) and low leaf area-based antioxidant levels, but not to variation in leaf mass-based antioxidant levels or stomatal conductance. The well-known and easily measured leaf trait LMA thus represents a potentially useful metric for O3 risk assessment and for selecting appropriate species for urban greening in O3-polluted areas.

Hunting alters seedling functional trait composition in a Neotropical forest.

Defaunation alters trophic interactions between plants and vertebrates, whichmay disrupt trophic cascades, thereby favoring a subset of plant species and reducing diversity. If particular functional traits characterize the favored plant species,.then defaunation may alter community-wide patterns of functional trait composition. Changes in plant functional traits occurring with defaunation may help identify the species interactions affected by defaunation and the potential for other cascading effects of defaunation. We tested the hypotheses that defaunation would (1) disrupt seed dispersal, thereby favoring species whose dispersal agents are not affected (e.g., small birds, bats, and abiotic agents), (2) reduce seed predation, thereby favoring larger-seeded species, and (3) reduce herbivory, thereby favoring species with lower leaf mass per area (LMA), leaf toughness, and wood density. We examined how these six traits responded to vertebrate defaunation caused by hunters or by experimental exclosures among more than-30 000 woody seedlings in a lowland tropical moist forest. Exclosures reduced terrestrial frugivores, granivores, and herbivores, while hunters also reduced volant and arboreal frugivores and granivores. The comparison of exclosures and hunting allowed us to parse the impacts of arboreal and volant species (reduced by hunters only) and terrestrial species (reduced by both hunters and exclosures). The loss of terrestrial vertebrates alone had limited effects on plant trait composition. The additional loss of volant and arboreal vertebrates caused significant shifts in plant species composition towards communities with more species dispersed abiotically, including lianas and low wood-density tree species, and fewer species dispersed by large vertebrates. In contrast to previous studies, community seed mass did not decline significantly in hunted sites. Our exclosure results suggest this is because reducing seed predators disproportionately benefits large-seeded species,.partially compensating for the reduction of seed dispersers at hunted sites. Our result9sdemonstrate that decreased seed dispersal and seed predation are important determinants of seedling community compositional change as a consequence of defaunation. Defaunation may also negatively impact carbon storage in tropical forests, by favoring lianas and low wood density tree species.

High foliar nutrient concentrations and resorption efficiency in Embothrium coccineum (Proteaceae) in southern Chile.

Southern South American (SA) Proteaceae species growing in volcanic soils have been proposed as potential ecosystem engineers by tapping phosphorus (P) from soil through their cluster roots and shedding nutrient-rich litter to the soil, making it available for other species. We tested whether Embothrium coccineum (Proteaceae) has effectively lower P nutrient resorption efficiency and higher litter P concentrations than co-occurring, non-Proteaceae species. In southern Chile, we assessed the P and nitrogen (N) resorption efficiency of senescent leaves and fresh litter of E. coccineum and co-occurring tree species in a soil fertility and moisture gradient (600-3000 mm of annual precipitation) in Patagonia, Chile. We determined P and N concentrations, leaf mass per area (LMA), and ratios of N/P and C/N in mature and senescent leaf cohorts and fresh litter. Embothrium coccineum showed significantly higher P and N resorption efficiency than co-occurring species; in fact, E. coccineum fresh litter had the lowest P-content. While E. coccineum showed significantly lower fresh litter P concentrations than the rest of the species, it showed significantly higher N concentrations. Embothrium coccineum also had lower LMA and similar N/P and C/N ratios when compared with co-occurring tree species. We found that E. coccineum efficiently mobilized P and, to a lesser extent, N before leaf shedding. We did not find support for the ecosystem engineering hypothesis via shedding P-rich litter. We suggest that southern South American Proteaceae may be taking up other nutrients besides P, probably N, from the young, volcanic soils of this region.

임분 조건이 다른 환경에서 하층식생으로 생육하는 까치박달(Carpinus cordata) 유목의 양분 이용 특성

This study aimed to understand the nutrient absorption, usage and allocation of Carpinus cordata in different soil and light environments. Seasonal changes of foliar nitrogen, phosphorous, chlorophyll contents, leaf mass per area (LMA) and nutrient retranslocation rates were investigated for C. cordata saplings growing in a natural deciduous broadleaved forest and an Manchurian fir (Abies holophylla) plantation in Gwangneung, Kyunggido. The deciduous forest had lower leaf area, higher light penetration, and better soil fertility than the Manchurian fir forest. However, available soil phosphorous content in the deciduous forest was only one third of that in the Manchurian fir forest, which caused lower foliar phosphorous content and higher P retranslocation rate of C. cordata in the deciduous forest than that in the Mancurian fir forest. Soil nitrogen contents in the deciduous forest were higher than that in the Manchurian fir forest, however, no differences in foliar nitrogen content and retranslocation rate in C. cordata between the two stands were found. C. cordata in the Manchurian fir forest with high LAI throughout a year, had lower LMA, foliar nitrogen content and chlorophyll a/b, while had higher total chlorophyll content and chlorophyll/N than that in the deciduous forest. These results implied C. cordata under different environments are using different strategies for nutrient use and allocations.

广西猫儿山不同海拔常绿树种和落叶树种光合速率与氮的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 广西猫儿山不同海拔常绿树种和落叶树种光合速率与氮的关系 DOI: 10.5846/stxb201205200750 作者: 作者单位: 广西壮族自治区中国科学院广西植物研究所,广西猫儿山国家级自然保护区管理局 桂林,中国林业科学研究院林业新技术研究所 北京 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31100285); 中央级公益性科研院所基本科研业务费专项资金(CAFINT2009C08); 国家科技支撑计划课题(2012BAC16B01) Photosynthesis-nitrogen relationship in evergreen and deciduous tree species at different altitudes on Mao’er Mountain, Guangxi Author: Affiliation: Guangxi Institute of Botany, Guangxi Zhuang Autonomous Region and Chinese Acedemy of Sciences,,Institute of New Forest Technology, Chinese Academy of Forestry Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分析广西猫儿山不同海拔常绿和落叶树种的光合作用-氮关系,探讨光合氮利用效率(PNUE)是否受到叶片习性和海拔的影响。落叶树种的PNUE都显著高于常绿树种,这与前者有较低的比叶重(LMA)和较高的单位叶重光合速率(Amass)、氮含量和气孔导度(gs)有密切关系。高海拔树种的PNUE显著低于中低海拔树种的PNUE,这与前者较高的LMA和较低的Amass和gs相关。PNUE和相关的叶片特征的主成分分析表明常绿-落叶树种和低海拔-中海拔-高海拔树种的分布是一个自然过渡的过程。此外,PNUE与土壤碳:氮比没有显著相关性,但与年均温正相关,这表明温度气候是调节PNUE沿海拔变化的主要环境因素。因此,这种叶片习性和温度气候调节的PNUE变化可能是调节猫儿山常绿树种沿海拔形成双峰分布的一种机制。 Abstract:The present study analyzed the photosynthesis-nitrogen relationship in evergreen and deciduous tree species at different altitudes on Mao'er Mountain, Guangxi, and explored whether photosynthetic nitrogen use efficiency (PNUE) was affected by leaf habit and altitude. Deciduous tree species had significanlty higher PNUE than evegreen tree species because of lower leaf mass per area (LMA) and higher photosynthetic rate per mass (Amass), nitrogen content and stomatal conductance (gs) in the former. Tree species at high altitude had significantly lower PNUE than those at middle and low altitudes due to higher LMA and lower Amass and gs in the former. Principal component analysis for PNUE and its related leaf traits suggested that the tree species distribution of evergreen-deciduous and low-middle-high altitude were in the process of natural transition. In addition, PNUE was not related to soil carbon: nitrogen ratio, but significantly positive related to mean annual temperature, suggesting that temperature climate was the main environmental factor that regulated the altitudianl changes in PNUE. Therefore, this differential PNUE that was affected by leaf habit and temperature climate was a mechanism for the bimodal distribution of evergreen tree species along the altitudes on Mao'er Montain. 参考文献 相似文献 引证文献

Fertilisation residues alter leaf scleromorphy in an evergreen savannah shrub (Maprounea brasiliensis, Euphorbiaceae)

In the present study, we examined how residues of nitrogen (N), phosphorus (P) and calcium (Ca) fertilisers affect leaf anatomical traits in Maprounea brasiliensis (Euphorbiaceae), a typical and dominant cerrado (Brazilian savannah) species adapted to dystrophic soils. We predicted that fertiliser residues would alter qualitative and quantitative aspects of M. brasiliensis leaves and would decrease their scleromorphy. Leaves were sampled from plants that were growing in soils previously fertilised with N, P and Ca and in plants that were growing in soils without fertiliser residues. We measured the thickness of the cuticle, the epidermis of adaxial and abaxial surfaces, thickness of palisade parenchyma and spongy parenchyma, total thickness of the leaf, total area of the midrib and leaf mass per area (LMA). We found that plants under fertiliser residues produced fewer scleromorphic leaves with low LMA, thinner cuticle and epidermis and thicker palisade and spongy parenchyma. They also showed a decrease in the size and area occupied by the leaf midvein. However, plants under fertiliser residues produced similar leaf thickness as did the plants in the control group. Our results showed that residual effects of fertilisation changed structural patterns of a typical species of cerrado. Thus, further studies about fertilisation effects on leaf traits are needed because larger areas of the central cerrado are being occupied for agricultural production.

Leaf anatomy, ultrastructure and plasticity of Coffea arabica L. in response to light and nitrogen availability

Phenotypic plasticity in response to environmental variation occurs at all organizational levels and across temporal scales within plants. However, the magnitude and functional significance of this plasticity is little explored in perennial species. We examined the influence of different light regimes and nitrogen (N) availability on the morphological and physiological plasticity of coffee seedlings (Coffea arabica L.). Potted plants were grown under 100% and 50% of full sunlight and were fertilized with Hoagland’s solutions containing 0, 16 or 23mM N. Most leaf traits responded to light with a classic 100% vs. 50% dichotomy [e.g., compared with those grown under 100% of full sunlight, 50% leaves had a thinner palisade mesophyll and a lower leaf mass per area (LMA) for improved light capture]. The outer periclinal cell walls in both epidermises exhibited thick epicuticular wax and three distinct layers. Chloroplasts of the mesophyll cells were densely occupied by thylakoids and starch grains. These characteristics were observed most clearly in plants supplemented by nitrogen or in those grown in shade conditions. Large starch granules were observed, but no membrane injuries were observed in either treatment. The plasticity index was high for the physiological traits that are associated with photoprotection and the maintenance of a positive carbon balance under 50% of full sunlight but was low for most morpho-anatomical features.

Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008–2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect – inhibition of above-ground growth rate – was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO3 − in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO2 concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

Responses of leaf structure and photosynthetic properties to intra-canopy light gradients: a common garden test with four broadleaf deciduous angiosperm and seven evergreen conifer tree species.

Spectra of leaf traits in northern temperate forest canopies reflect major differences in leaf longevity between evergreen conifers and deciduous broadleaf angiosperms, as well as plastic modifications caused by within-crown shading. We investigated (1) whether long-lived conifer leaves exhibit similar intra-canopy plasticity as short-lived broadleaves, and (2) whether global interspecific relationships between photosynthesis, nitrogen, and leaf structure identified for sun leaves adequately describe leaves differentiated in response to light gradients. We studied structural and photosynthetic properties of intra-tree sun and shade foliage in adult trees of seven conifer and four broadleaf angiosperm species in a common garden in Poland. Shade leaves exhibited lower leaf mass-per-area (LMA) than sun leaves; however, the relative difference was smaller in conifers than in broadleaves. In broadleaves, LMA was correlated with lamina thickness and tissue density, while in conifers, it was correlated with thickness but not density. In broadleaves, but not in conifers, reduction of lamina thickness was correlated with a thinner palisade layer. The more conservative adjustment of conifer leaves could result from a combination of phylogenetic constraints, contrasting leaf anatomies and shoot geometries, but also from functional requirements of long-lived foliage. Mass-based nitrogen concentration (Nmass) was similar between sun and shade leaves, and was lower in conifers than in deciduous broadleaved species. Given this, the smaller LMA in shade corresponded with a lower area-based N concentration (Narea). In evergreen conifers, LMA and Narea were less powerful predictors of area-based photosynthetic rate (A max(area)) in comparison with deciduous broadleaved angiosperms. Multiple regression for sun and shade leaves showed that, in each group, A max(mass) was related to Nmass but not to LMA, whereas LMA became a significant codeterminant of A max(mass) in analysis combining both groups. Thus, a fundamental mass-based relationship between photosynthesis, nitrogen, and leaf structure reported previously also exists in a dataset combining within-crown and across-functional type variation.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-012-2279-y) contains supplementary material, which is available to authorized users.

Can we predict carbon stocks in tropical ecosystems from tree diversity? Comparing species and functional diversity in a plantation and a natural forest

• Linking tree diversity to carbon storage can provide further motivation to conserve tropical forests and to design carbon-enriched plantations. Here, we examine the role of tree diversity and functional traits in determining carbon storage in a mixed-species plantation and in a natural tropical forest in Panama. • We used species richness, functional trait diversity, species dominance and functional trait dominance to predict tree carbon storage across these two forests. Then we compared the species ranking based on wood density, maximum diameter, maximum height, and leaf mass per area (LMA) between sites to reveal how these values changed between different forests. • Increased species richness, a higher proportion of nitrogen fixers and species with low LMA increased carbon storage in the mixed-species plantation, while a higher proportion of large trees and species with high LMA increased tree carbon storage in the natural forest. Furthermore, we found that tree species varied greatly in their absolute and relative values between study sites. • Different results in different forests mean that we cannot easily predict carbon storage capacity in natural forests using data from experimental plantations. Managers should be cautious when applying functional traits measured in natural populations in the design of carbon-enriched plantations.

Optimisation of spatial allocation patterns in lianas compared to trees used for support

There are only limited possibilities to study the competition between trees and lianas in the top canopy of tropical rain forests. Furthermore, the important question how the leaf traits are related to twig support is rarely studied, especially regarding growing space partitioning between the self-supporting and the climbing growth form. Our study used the hot-air balloon within the “Operation Canopee” in the Masoala National Park, Madagascar, to test the differences in spatial allocation patterns of leaves and twigs in lianas and tree parts used for support. The sampling design emphasised to obtain a common assembly of twigs and leaves from both, trees and lianas. The results from the top canopy were compared to the data from the understorey regarding biomass and nutrients in leaves and distal twigs. In the understorey the reduction in structural investment was much stronger in lianas than in trees. The results showed that lianas reduced carbon investment per volume, but increased leaf nitrogen concentration and leaf area ratio (LAR), the latter driven by a reduction in leaf mass per area (LMA). In the top canopy, lianas contributed about one third of the leaf area density of 3 m2 m−3. For distal twigs, no relationship was found between twig biomass per volume and leaf area density for trees, but lianas balanced both structural parameters closely. The climbers benefit from the external support provided by the trees and optimise the area of assimilation tissue at low per volume investment for mechanical stability. Several traits such as low LMA and high leaf nitrogen concentrations together with higher LAR and optimised spatial investment advantage the climbing growth form and enable a fast acquisition of growing space. The results emphasize the necessity to consider spatial and structural features of growing space acquisition when dealing with plant competition.

Variation in longevity and traits of leaves among co-occurring understorey plants in a tropical montane forest

Abstract:The relationship between leaf longevity and other leaf traits was compared among different life-form categories (trees, herbs, climbers and epiphytes) of 101 plant species in a tropical montane forest on Mt. Halimun, West Java, Indonesia. We applied the Cox proportional hazards regression to estimate the leaf longevity of each species from 30 mo of census data. We examined whether estimated longevity was explained by either species life-form categories, taxonomic groupings (eudicots, monocots, magnoliids and chloranthales, and ferns) or such leaf traits as leaf area, leaf mass per area (LMA), mass-based leaf nitrogen, penetrometer reading, condensed-tannin-free total phenolics and condensed tannin. There was a wide-ranged interspecific variation in leaf longevity, mostly 10–50 mo, similarly across life-form categories. LMA showed a strong positive influence on leaf longevity. We found that relationships between leaf longevity and some leaf traits were different among various life forms. Trees tended to have high LMA, while climbers tended to have low LMA at the same leaf longevity. We hypothesize that such difference among life forms reflects shoot architecture characteristics. Multi-shoot trees with branching architecture need to have self-supporting leaves, whereas semi-epiphytic climbers can maintain relatively low biomass investment to leaves hanging or relying upon the mechanical support from host plants.

Effect of soil biota on growth and allocation by Eucalyptus microcarpa

We examined growth of Eucalyptus microcarpa seedlings in soil collected from four sites in southeastern Australia, in which retired pasture land has been revegetated with mixed plantings of Eucalyptus and Acacia species. Revegetation of farm land in southeastern Australia is an area of major investment. The focus of the study was to examine the influence of soil biota on seedling growth and its possible interaction with soil enrichment from a legume (Acacia) and decomposition rates. We used a soil freezing treatment (−80°C for 3 days) to retard the soil biota, with the expectation that invertebrates in particular would be killed. Soil freezing did not cause a nutrient pulse, but did reduce the level of ammonium in soil. Nitrate levels increased with time in pots, regardless of the soil treatment. Decomposition rates measured using cellulose substrate were significantly reduced by the freeze treatment, but only for approximately 90 days. Eucalyptus microcarpa seedlings grown in freeze-treated soil were approximately 40% smaller (total biomass), had marginally lower LAR (leaf area ratio), and significantly lower LMA (leaf mass per area). Low LMA indicates that leaves are either thinner in cross-section or less dense. We hypothesise that both the poor growth of seedlings and production of less robust leaves are consequences of reduced availability of soil nutrients due to the diminished soil biota after freeze treatment. Litter under Acacia was richer in nitrogen than litter under Eucalyptus but there was no difference in nitrogen content of soil, and consequently no soil source effects on plant growth or decomposition. We suggest that variation in the soil biota has the potential to greatly enhance or hinder the success of revegetation on retired agricultural land, but enrichment of soil by decomposition of nitrogen rich litter in these sites requires longer than the 8–15 years since they were revegetated.

Plant phenology, leaf traits and leaf litterfall of contrasting life forms in the arid Patagonian Monte, Argentina

AbstractQuestion: Do coexisting plant life forms differ in overall phenology, leaf traits and patterns of leaf litterfall?Location: Patagonian Monte, Chubut Province, Argentina.Methods: We assessed phenology, traits of green and senesced leaves and the pattern of leaf litterfall in 12 species of coexisting life forms (perennial grasses, deciduous shrubs, evergreen shrubs).Results: We did not identify differences in phenology, leaf traits and patterns of leaf litterfall among life forms but these attributes contrasted among species. Independent of the life form, the maintenance of green leaves or vegetative growth during the dry season was mostly associated with leaves with high leaf mass per area (LMA) and high concentration of secondary compounds. Low LMA species produced low litterfall mass with low concentration of secondary compounds, and high N concentration. High LMA species produced the largest mass of leaf litterfall. Accordingly, species were distributed along two main dimensions of ecological variation, the dimension secondary compounds in leaves ‐ length and timing of the vegetative growth period (SC ‐ VGP) and the dimension leaf mass per area ‐ leaf litterfall mass (LMA ‐ LLM).Conclusions: Phenology, leaf traits and leaf litterfall varied among species and overlapped among life forms. The two dimensions of ecological variation among species (SC ‐ VGP, LMA ‐ LLM) represent distinct combinations of plant traits or strategies related to resource acquisition and drought tolerance which are reflected in the patterns of leaf litterfall.

Are correlations among foliar traits in ferns consistent with those in the seed plants?

Broad-based studies of gymnosperms and angiosperms reveal consistent and functionally significant correlations among foliar traits such as leaf mass per area (LMA), maximum photosynthetic rate (A(area)), foliar nitrogen (N(area)), foliar chlorophyll (Chl) and leaf longevity. To assess the generality of these relationships, we studied 20 fern species growing in the understorey of a temperate deciduous forest. We found that foliar N(area) increases with LMA, and that foliar N(area) and A(area) are positively correlated with one another, as are foliar N(area) and Chl. The ferns in general have very low LMA compared with most seed plants; A(area), N(area) and Chl are below median values for seed plants but are not extreme. Species with overwintering fronds have significantly higher LMA than species with fronds that senesce at the end of the growing season, as well as a significantly higher C : N ratio in frond tissue and relatively high foliar N on an areal basis. Correlations among foliar traits associated with gas exchange in these forest understorey ferns are in accordance with patterns reported for seed plants, suggesting a high degree of functional constraint on the interrelationships among key elements in foliar design.