Article

Biomechanical and leaf-climate relationships: A comparison of ferns and seed plants

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Abstract

Relationships of leaf size and shape (physiognomy) with climate have been well characterized for woody non-monocotyledonous angiosperms (dicots), allowing the development of models for estimating paleoclimate from fossil leaves. More recently, petiole width of seed plants has been shown to scale closely with leaf mass. By measuring petiole width and leaf area in fossils, leaf mass per area (MA) can be estimated and an approximate leaf life span inferred. However, little is known about these relationships in ferns, a clade with a deep fossil record and with the potential to greatly expand the applicability of these proxies. We measured the petiole width, MA, and leaf physiognomic characters of 179 fern species from 188 locations across six continents. We applied biomechanical models and assessed the relationship between leaf physiognomy and climate using correlational approaches. The scaling relationship between area-normalized petiole width and MA differs between fern fronds and pinnae. The scaling relationship is best modeled as an end-loaded cantilevered beam, which is different from the best-fit biomechanical model for seed plants. Fern leaf physiognomy is not influenced by climatic conditions. The cantilever beam model can be applied to fossil ferns. The lack of sensitivity of leaf physiognomy to climate in ferns argues against their use to reconstruct paleoclimate. Differences in climate sensitivity and biomechanical relationships between ferns and seed plants may be driven by differences in their hydraulic conductivity and/or their differing evolutionary histories of vein architecture and leaf morphology.

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... Plants on the "fast-return" end of the spectrum, characterized by rapid resource acquisition, typically have a short leaf life-span (less than 12 months), high photosynthetic and respiration rates, low leaf mass per area (M A ), high nutrient concentrations (principally nitrogen and phosphorus), and fast growth rates, while the inverse is true for plants with slow resource acquisition on the "slow-return" end of the spectrum (Reich et al. 1997;Westoby et al. 2002;Diaz et al. 2004;Wright et al. 2004Wright et al. , 2005Reich 2014). The interrelationships between these traits are largely independent of phylogeny in seed plants (Ackerly and Reich 1999), have been observed in all vascular plant groups (Wright et al. 2004;Karst and Lechowicz 2007;Peppe et al. 2014), and probably reflect evolutionary trade-offs in leaf design to maximize resource acquisition vs. performance for the environment in which a plant is living (Shipley et al. 2006). ...
... While in modern leaves these LES variables are easily measured, they cannot be directly measured in fossil leaves. Instead a series of different proxies based on features that are measureable in fossil leaves, such as leaf area, petiole width, and vein density, have been developed to estimate leaf mass per area M a , leaf life-span (LLS), carbon assimilation rate, and respiration rate (e.g., Brodribb et al. 2007;Boyce et al. 2009;Brodribb and Feild 2010;Royer et al. 2007Royer et al. , 2010Royer et al. , 2012Blonder et al. 2011;Feild et al. 2011b;Sack et al. , 2014Blonder and Enquist 2014;Peppe et al. 2014). These reconstructed LES variables can then be used to reconstruct aspects of the paleoecology of the fossil plant (e.g., leaf life-span, hydraulic conductance), as well as other features of the ecosystem and environment in which the plant lived. ...
... These reconstructed LES variables can then be used to reconstruct aspects of the paleoecology of the fossil plant (e.g., leaf life-span, hydraulic conductance), as well as other features of the ecosystem and environment in which the plant lived. Since the majority of these methods are developed based on relationships within the LES, they are applicable across a variety of plant groups and can be used throughout the geologic record (e.g., Royer et al. 2007Royer et al. , 2010Royer et al. , 2012Boyce et al. 2009;Brodribb and Feild 2010;Blonder et al. 2011Blonder et al. , 2014bFeild et al. 2011b;Crifo et al. 2014;Peppe et al. 2014), though some aspects of the LES, such as carbon assimilation and respiration rates are probably heavily dependent on past levels of atmospheric CO 2 and O 2 (e.g., De Boer et al. 2012;McElwain et al. 2016). ...
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Plants are strongly influenced by their surrounding environment, which makes them reliable indicators of climate and ecology. The relationship between climate, ecology, plant traits and the geographic distribution of plants based on their climatic tolerances have been used to develop plant-based proxies for reconstructing paleoclimate and paleoecology. These proxies are some of the most accurate and precise methods for reconstructing the climate and ecology of ancient terrestrial ecosystems and have been applied from the Cretaceous to the Quaternary. Despite their utility, the relationships between plant traits and climate that underlie these methods are confounded by other factors such as leaf life-span and phylogenetic history. Work focused on better understanding these confounding factors, incorporating the influence of phylogeny and leaf economic spectrum traits into proxies, expanding modern leaf trait-climate and ecology calibration datasets to additional biogeographic areas and climate regimes, and developing automated computer algorithms for measuring leaf traits are important growing research areas that will help considerably improve plant-based paleoclimate and paleoecological proxies.
... Plants on the "fast-return" end of the spectrum, characterized by rapid resource acquisition, typically have a short leaf life-span (less than 12 months), high photosynthetic and respiration rates, low leaf mass per area (M A ), high nutrient concentrations (principally nitrogen and phosphorus), and fast growth rates, while the inverse is true for plants with slow resource acquisition on the "slow-return" end of the spectrum (Reich et al. 1997;Westoby et al. 2002;Diaz et al. 2004;Wright et al. 2004Wright et al. , 2005Reich 2014). The interrelationships between these traits are largely independent of phylogeny in seed plants (Ackerly and Reich 1999), have been observed in all vascular plant groups (Wright et al. 2004;Karst and Lechowicz 2007;Peppe et al. 2014), and probably reflect evolutionary trade-offs in leaf design to maximize resource acquisition vs. performance for the environment in which a plant is living (Shipley et al. 2006). ...
... While in modern leaves these LES variables are easily measured, they cannot be directly measured in fossil leaves. Instead a series of different proxies based on features that are measureable in fossil leaves, such as leaf area, petiole width, and vein density, have been developed to estimate leaf mass per area M a , leaf life-span (LLS), carbon assimilation rate, and respiration rate (e.g., Brodribb et al. 2007;Boyce et al. 2009;Brodribb and Feild 2010;Royer et al. 2007Royer et al. , 2010Royer et al. , 2012Blonder et al. 2011;Feild et al. 2011b;Sack et al. , 2014Blonder and Enquist 2014;Peppe et al. 2014). These reconstructed LES variables can then be used to reconstruct aspects of the paleoecology of the fossil plant (e.g., leaf life-span, hydraulic conductance), as well as other features of the ecosystem and environment in which the plant lived. ...
... These reconstructed LES variables can then be used to reconstruct aspects of the paleoecology of the fossil plant (e.g., leaf life-span, hydraulic conductance), as well as other features of the ecosystem and environment in which the plant lived. Since the majority of these methods are developed based on relationships within the LES, they are applicable across a variety of plant groups and can be used throughout the geologic record (e.g., Royer et al. 2007Royer et al. , 2010Royer et al. , 2012Boyce et al. 2009;Brodribb and Feild 2010;Blonder et al. 2011Blonder et al. , 2014bFeild et al. 2011b;Crifo et al. 2014;Peppe et al. 2014), though some aspects of the LES, such as carbon assimilation and respiration rates are probably heavily dependent on past levels of atmospheric CO 2 and O 2 (e.g., De Boer et al. 2012;McElwain et al. 2016). ...
Chapter
Full-text available
Plants are strongly influenced by their surrounding environment, which makes them reliable indicators of climate and ecology. The relationship between climate, ecology, plant traits and the geographic distribution of plants based on their climatic tolerances have been used to develop plant-based proxies for reconstructing paleoclimate and paleoecology. These proxies are some of the most accurate and precise methods for reconstructing the climate and ecology of ancient terrestrial ecosystems and have been applied from the Cretaceous to the Quaternary. Despite their utility, the relationships between plant traits and climate that underlie these methods are confounded by other factors such as leaf life-span and phylogenetic history. Work focused on better understanding these confounding factors, incorporating the influence of phylogeny and leaf economic spectrum traits into proxies, expanding modern leaf trait-climate and ecology calibration datasets to additional biogeographic areas and climate regimes, and developing automated computer algorithms for measuring leaf traits are important growing research areas that will help considerably improve plant-based paleoclimate and paleoecological proxies.
... Hence, dissimilarity in the large-scale distributional patterns of plant richness may exist across different taxonomic levels. Furthermore, previous studies have identified different legacy effects of climate on the largescale distributional patterns of plant richness in non-seed and seed plants (Peppe et al. 2014, Boyce & Lee 2017. Non-seed plants may be more sensitive to the velocity of climate change than seed plants due to their different reproduction and dispersal characteristics (Peppe et al. 2014. ...
... Furthermore, previous studies have identified different legacy effects of climate on the largescale distributional patterns of plant richness in non-seed and seed plants (Peppe et al. 2014, Boyce & Lee 2017. Non-seed plants may be more sensitive to the velocity of climate change than seed plants due to their different reproduction and dispersal characteristics (Peppe et al. 2014. Lu et al. (2018) explored the evolutionary history of the angiosperm flora of China at the species, family, and genus levels and identified areas of high species richness and phylogenetic diversity. ...
... Fossil plant records (e.g., Dubiel 1987, Collinson 2001, Watkins & Cardelús 2012, Naugolnykh et al. 2016 indicate that paleoclimates have affected the large-scale distributional pattern of ferns, while current bioclimatic variables, mainly those related to humidity (as water is an essential medium for fern reproduction), are closely associated with the variation in fern community composition. The physiological requirements and relative habitat restrictions of fern plants make them more sensitive to climate change than seed plants, and the effects of climate on plant richness may therefore differ between fern and seed plants (Schneider et al. 2004, Peppe et al. 2014. ...
Article
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p align="left"> Background: Historical and contemporary climates may shape the distributional patterns of plant species richness across different scales. However, few studies have focused on the effects of historical and contemporary climate changes on the distributional patterns of plant richness in Chinese protected areas across different taxonomic levels. Hypotheses: Historical and contemporary climates can have an important legacy effect on the large-scale distributional patterns of plant richness across different taxonomic levels. Studied species: Vascular plants. Study site: China. Method: We used data on plant richness at the family, genus, and species levels from Chinese protected areas and applied regression modelling to explore the relationships between climate change and plant richness among vascular, fern, seed, gymnosperm, and angiosperm plants based on paleoclimate (Last Glacial Maximum; LGM, ca. 22,000 years ago) and contemporary climate data. Results: The large-scale distributional patterns of plant richness could be predicted across different taxonomic levels on the basis of paleoclimate and contemporary climate data. Specifically, historical and contemporary climate variables were found to better correlate with fern plant richness than seed plant richness. For seed plants, the explanatory power of historical and contemporary climate variables was found to be stronger for the richness of gymnosperms than for the richness of angiosperms. Conclusions: The distributional pattern of plant richness could be predicted across different taxonomic levels after including paleoclimate (LGM, ca. 22,000 years ago) and contemporary climate data from China. Our study could support the effectiveness of the management of protected areas in China.
... Leaf structural and functional traits are generally correlated with each other and with the environment (Reich et al., 1997;Wright et al., 2004Wright et al., , 2005. Relationships of leaf morphology traits with climate have been well characterized for dicotyledons, allowing to reconstruct paleoclimate from fossil leaves in the geological past (Royer, 2012;Peppe et al., 2011Peppe et al., , 2014Soh et al., 2017). For example, the strong relationship between leaf teeth and temperature observed in extant woody dicotyledon can be used to estimate the paleotemperature (Royer, 2012). ...
... The biomechanical scaling relationship between petiole width and leaf mass per area in living woody dicotyledons and gymnosperms have been applied to fossil leaves to infer their paleoecological strategy (Royer et al., 2007(Royer et al., , 2010. However, significant quantitative relationships between morphological and anatomical adaptions (e.g., leaf size, stomatal parameters) and climate conditions for ferns have not been found yet (Peppe et al., 2014). Nonetheless, investigating leaf-climate relationships in ferns should not be overlooked because ferns are once a principal component of terrestrial ecosystem from the late Paleozoic/ early Mesozoic era and could be a potential paleoclimate proxy. ...
Article
The end-Triassic mass extinction (ETME) is considered to be one of the five most severe extinction events in Earth history and caused the disappearance of ca. 80% of all species. The terrestrial ecosystems were also greatly affected by this extinction, but the severity of the land plant diversity loss is not well understood. Ferns are once a principal component of the terrestrial ecosystem from the late Paleozoic/early Mesozoic era and colonizers taxa commonly found in disturbed environments. In this study, we investigated the diversity and ecology of fern during the Triassic-Jurassic (Tr–J) transition in the Sichuan Basin of South China and focused for the first time on the impact of the end-Triassic mass extinction event on the fern communities. We assembled fern fossil records in 16 localities from the Rhaetian Xujiahe (XJH) Formation to the lowermost Jurassic Zhenzhuchong (ZZC) Formation. Our results indicate that no obvious mass extinctions of macro-microflora of ferns but a clear species turnover was recorded at ETME in the Sichuan Basin, reflected an appropriate response of plants in places far away from CAMP volcanism. The paleoecological analysis based on macroflora and microflora in the Sichuan Basin shows a warm and humid condition of tropical-subtropical climate during Rhaetian followed by an increase of specific dry-resistant taxa, indicating a dryer environment at the Earliest Jurassic. Additionally, multivariate statistical approaches (principal coordinates analysis, cluster analysis, network analysis) for fern macro-remains and spores data in the southeastern Sichuan Basin infer that the members of XJH and ZZC Formation cluster in three groups, corresponding to their environmental conditions, determined by humidity and temperature.
... Similarly, in quantifying variation in LMA (leaf mass per area), a key trait in the leaf economic spectrum (Wright et al., 2004) and a good predictor of leaf function (Fig. 4), we found that measured LMA was closely linked to a leaf 's light environment and that petiole metric, cell area, and leaf δ 13 C, the same traits that were most useful for predicting canopy cover, also had the strongest relationship with LMA. The petiole metric has previously been used to reconstruct an average LMA of ecosystems (Royer et al., 2007) and the ecology and function of plants found in fossil leaf assemblages (Royer et al., 2010;Peppe et al., 2014Peppe et al., , 2018. Our observations of LMA were within a range seen across rainforests globally (e.g., 50-120 gm -2 ; Poorter et al., 2009). ...
... On the other hand, the scaling between petiole area and leaf mass is different between understory and canopy leaves (Fig. 1B). This divergence in mass-based allometric scaling constants between understory and canopy leaves accounts for our observed variance in the petiole metric to LMA relationship across groups (Fig. 1C) and may also account for variance previously seen in both herbaceous dicots (Royer et al., 2010) and ferns (Peppe et al., 2014). See Appendix S8 for formulation and further discussion. ...
Article
Premise: Within closed-canopy forests, vertical gradients of light and atmospheric CO2 drive variations in leaf carbon isotope ratios, leaf mass per area (LMA), and the micromorphology of leaf epidermal cells. Variations in traits observed in preserved or fossilized leaves could enable inferences of past forest canopy closure and leaf function and thereby habitat of individual taxa. However, as yet no calibration study has examined how isotopic, micro- and macromorphological traits, in combination, reflect position within a modern closed-canopy forest or how these could be applied to the fossil record. Methods: Leaves were sampled from throughout the vertical profile of the tropical forest canopy using the 48.5 m crane at the Daintree Rainforest Observatory, Queensland, Australia. Carbon isotope ratios, LMA, petiole metric (i.e., petiole-width2 /leaf area, a proposed proxy for LMA that can be measured from fossil leaves), and leaf micromorphology (i.e., undulation index and cell area) were compared within species across a range of canopy positions, as quantified by leaf area index (LAI). Results: Individually, cell area, δ13 C, and petiole metric all correlated with both LAI and LMA, but the use of a combined model provided significantly greater predictive power. Conclusions: Using the observed relationships with leaf carbon isotope ratio and morphology to estimate the range of LAI in fossil floras can provide a measure of canopy closure in ancient forests. Similarly, estimates of LAI and LMA for individual taxa can provide comparative measures of light environment and growth strategy of fossil taxa from within a flora.
... Leaf structural and functional traits are generally correlated with each other and with the environment (Reich et al., 1997;Wright et al., 2004Wright et al., , 2005. Relationships of leaf morphology traits with climate have been well characterized for dicotyledons, allowing to reconstruct paleoclimate from fossil leaves in the geological past (Royer, 2012;Peppe et al., 2011Peppe et al., , 2014Soh et al., 2017). For example, the strong relationship between leaf teeth and temperature observed in extant woody dicotyledon can be used to estimate the paleotemperature (Royer, 2012). ...
... The biomechanical scaling relationship between petiole width and leaf mass per area in living woody dicotyledons and gymnosperms have been applied to fossil leaves to infer their paleoecological strategy (Royer et al., 2007(Royer et al., , 2010. However, significant quantitative relationships between morphological and anatomical adaptions (e.g., leaf size, stomatal parameters) and climate conditions for ferns have not been found yet (Peppe et al., 2014). Nonetheless, investigating leaf-climate relationships in ferns should not be overlooked because ferns are once a principal component of terrestrial ecosystem from the late Paleozoic/ early Mesozoic era and could be a potential paleoclimate proxy. ...
Article
The genus Osmunda contains approximately 10 extant species widely distributed in tropical and temperate regions, with the greatest concentration of species in East and Southeast Asia. Osmunda is characterized by dimorphic or commonly hemidimorphic fronds with dimorphic pinnae. Its geological history has been traced back to the Triassic. Most records of the genus are based on the rhizomes and rarely on pinnae bearing sporangia and spores. Here, we describe fossil pinnae, sporangia and spores of Osmunda lignitum (Giebel) Stur recovered from the middle Eocene of the Changchang Formation in the Changchang Basin, Hainan Island and the Youganwo Formation in the Maoming Basin, Guangdong, South China. The fossils closely resemble the extant O . banksiifolia (C. Presl) Kuhn of the subgenus Plenasium on the basis of their morphological and anatomical structures. The present occurrence of O. lignitum indicates subg. Plenasium flourished and extended from the high latitude regions such as Northeast China to the low latitude areas of South China during the Eocene. Large numbers of specimens described here also indicate that Osmunda was the dominant understory fern element beneath mixed evergreen broad‐leaf angiosperm and gymnosperm forests living in a warm and humid environment. This article is protected by copyright. All rights reserved.
... 、 南美(Kowalski, 2002)、欧洲南部(Traiser et al., 2005)、非洲热带地 区(Jacobs, 1999)、东亚(Wolfe, 1979;Su et al., 2010; Chen et al., 2014)、澳大利亚(Greenwood et al., 2004 Greenwood, 2005)乃至全球(Peppe et al., 2011;Royer et al., 2012)建立多个温度重建的转换方程。然而, 不同区域构建的转换方程在模型拟合度和回归斜率 上存在显著的差异(Greenwood et al., 2004 Adams et al., 2008;Peppe et al., 2011), 限制了转换模型的 普适性与外推。此外, 目前基于大尺度连续分布数 据的定量叶缘分析还很欠缺, 叶缘 组成对温度的响应及其潜在的生态影响因子尚需进 一步研究。 以往的叶缘分析主要关注叶缘组成与温度间的 关系(Gregory-Wodzicki, 2000;Royer et al., 2005Royer et al., , 2009aRoyer & Wilf, 2006;Peppe et al., 2011; Chen et al., 2014)。基于叶齿的生态学功能, 叶缘状态与 水分运输和利用率密切相关。在水分充足的湿润地 区, 叶缘可能更多地响应温度的变化(Adams et al.,Wiemann et al., 1998;Wilf et al., 1998;Peppe et al., 2011; Moles et al., et al., 2012;Peppe et al., 2014)。此外, 乔灌草也具有不同的叶缘-温度关系, 即乔木的叶缘状态对温度响应最敏感, 灌木居中, 草本最弱(Royer et al., 2012)。目前大尺度的叶缘分 析多以双子叶木本植物或被子植物为研究对象, 如 对欧洲阔叶树的叶缘研究(Traiser et al., 2005)、对全 球双子叶被子植物的研究(Royer et al., 2012)等; 部 分研究以双子叶乔木为研究对象, 如对北美(Adams et al., 2008)和对中国湿润地区(Chen et al., Dolph & Dilcher, 1980; Ackerly, 2004; Schmerler et al., 2012)及其与温度间的关系(Jordan, 1997; Little et al., 2010; Jordan, 2011)。Little等(Wilf, 1997; Adams et al., 2008; Peppe et al., 2011)。对北美乔木的叶缘分析发 Jacobs, 1999; Royer et al., 2005; Peppe et al., 2011)。 叶齿数目和大小均与 年平均气温呈负相关关系, 在寒冷的环境下, 叶片 通常具有更多、 更大的齿(Royer et al., 2005; Peppe et al., 2011)。 此外, 对Acer rubrum的研究发现, 叶齿数 目和叶裂程度对气候变化的响应非常敏感(Royer et al., 2009b)。在未来研究中, He et al., 2020)。小叶作为复叶的一部分, 并不是独立的单元, 复叶的小叶在某些生理功能上 类似于单叶的叶裂或叶齿(Xu et al., 2009)。 Niinemets et al., 2006; Wu et al., 2019), 这增加了侧 向生长的投入, 但相对于永久性枝条等木质结构, 复叶的叶轴比较"廉价", 可减少植株侧枝的生物量 分配, 从而更有效地促进垂直生长(Malhado et al., Niinemets, 1998), 在叶片光合、导水率等生理活动 上的差异(Yang et al., 2019a; 赵万里等, Niinemets, 1998;Warman et al., 2011;Wu et al., 2019)。与单叶相比, 复叶有相对较高的水分传导率 和光合速率, 因此具有较高的资源获取能力和相对 生长速率(Wu et al., 2019;Yang et al., 2019a)。此外, 有研究指出, 复叶在耐阴性和规避植食上与单叶相 比没有显著不同(Niinemets, 1998 Warman et al., Xu et al., 2009)。 在小尺度上, 复叶的小叶容易脱落, al., 1998Royer et al., 2005;Traiser et al., 2005; Peppe et al., 库 (TRY Plant Trait Database, https:// www.try-db.org/TryWeb/Prop0.php)和BIEN植物信息 与 生 态 网 络 (Botanical Information and Ecology Network, http://bien.nceas.ucsb.edu/bien/biendata/)两 ...
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Leaf is one of the important organs of plants to exchange water and air with surrounding environment. Leaves have various morphology and their traits directly affect the physiological and biochemical processes of plants, which reflects their adaptive strategies to obtain resource. Here, we focused on several leaf morphological traits, including leaf size, leaf shape, leaf margin (with or without teeth) and leaf type (i.e. single vs. compound leaf), and reviewed related research progress. We summarized the ecological function of leaf morphological traits, described geographical distribution of leaf morphology, and explored the behind environmental drivers, potential ecological interactions, and their effects on ecosystem functions. Current studies mainly focused on single or specific taxon in local regions to explore the distribution and determinants of leaf size and leaf margin state. Leaf development in morphology is under control of gene expression. Leaf morphology traits trade off with other functional traits, and their spatial variation is driven by both temperature and water availability. Leaf morphological traits, especially leaf size, influence water and nutrient cycling, reflect the response of communities to climate change, and can be scaling up to predict ecosystem primary productivity. Further study should pay attention to combine new approaches to obtain unbiased data in high coverage, to explore the long-term adaptive evolution of leaf morphology, and to generalize scaling in leaf morphology and its effect on ecosystem functioning. Leaf provides an important perspective to understand how plants respond and adapt to environmental changes. Studying on leaf morphological traits bridges individual fitness, community dynamics and ecosystem function, hence it improves our understanding of the research progress in related fields including plant community ecology and functional biogeography.
... Mechanisms underlying spatiotemporal variation in leaf size and shape have intrigued botanists for decades (Givnish 1978;Traiser et al. 2005;Peppe et al. 2014). Variation in leaf size and shape can lead to changes in carbon, water and energy exchange of plants with their environment, thereby influencing plant photosynthetic rates (Brito-Rocha et al. 2016;Fonseca et al. 2000;Malhado et al. 2009). ...
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Aims Morphological variation of leaves is a key indicator of plant response to climatic change. Leaf size and shape are associated with carbon, water and energy exchange of plants with their environment. However, whether and how leaf size and shape responded to climate change over the past decades remains poorly studied. Moreover, many studies have only explored inter- but not intraspecific variation in leaf size and shape across space and time. Methods We collected over 6000 herbarium specimens spanning 98 years (1910–2008) in China for seven representative dicot species and measured their leaf length and width. We explored geographical patterns and temporal trends in leaf size (i.e., leaf length, leaf width and length x width product) and shape (i.e., length/width ratio), and investigated the effects of changes in precipitation and temperature over time and space on the variation in leaf size and shape. Important findings After accounting for the effects of sampling time, leaf size decreased with latitude for all species combined, but the relationship varied among species. Leaf size and shape were positively correlated with temperature and precipitation across space. After accounting for the effects of sampling locations, leaf size of all species combined increased with time. Leaf size changes over time were mostly positively correlated with precipitation, whereas leaf shape changes were mostly correlated with temperature. Overall, our results indicate significant spatial and temporal intraspecific variation in leaf size and shape in response to climate. Our study also demonstrates that herbarium specimens collected over a considerable period of time provide a good resource to study the impacts of climate change on plant morphological traits.
... This coordination allows support of large lamina with reduced total frond length (smaller size) in epiphytic ferns with less danger of embolism, a finding supported by earlier work on fern hydraulics (Watkins et al. 2010). Relationships between petiole width and LMA have also been shown to differ between epiphytic and terrestrial ferns (Peppe et al. 2014), further suggesting that trait coordination may shift roles between support and hydraulic function across fern life forms. These shifts in frond structure and anatomy represent adaptations to prevent water stress and are realized by a greater water use efficiency (less negative lamina δ 13 C) detected in epiphytic ferns. ...
Preprint
Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi-epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi-epiphytic, and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (-63%), shorter stipe lengths (-56%), thicker laminae (+41%), and reduced stomatal density (-46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation, and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi-epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi-epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely canalized physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat.
... This coordination allows support of large lamina with reduced total frond length (smaller size) in epiphytic ferns with less danger of embolism, a finding supported by earlier work on fern hydraulics (Watkins et al., 2010). Relationships between petiole width and LMA have also been shown to differ between epiphytic and terrestrial ferns (Peppe et al., 2014), further suggesting that trait coordination may shift roles between support and hydraulic function across fern life forms. These shifts in frond structure and anatomy represent adaptations to prevent water stress and are realized by a greater water use efficiency (less negative lamina δ 13 C) detected in epiphytic ferns. ...
Article
Opportunistic diversification has allowed ferns to radiate into epiphytic niches in angiosperm dominated landscapes. However, our understanding of how ecophysiological function allowed establishment in the canopy and the potential transitionary role of the hemi‐epiphytic life form remain unclear. Here, we surveyed 39 fern species in Costa Rican tropical forests to explore epiphytic trait divergence in a phylogenetic context. We examined leaf responses to water deficits in terrestrial, hemi‐epiphytic, and epiphytic ferns and related these findings to functional traits that regulate leaf water status. Epiphytic ferns had reduced xylem area (‐63%), shorter stipe lengths (‐56%), thicker laminae (+41%), and reduced stomatal density (‐46%) compared to terrestrial ferns. Epiphytic ferns exhibited similar turgor loss points, higher osmotic potential at saturation, and lower tissue capacitance after turgor loss than terrestrial ferns. Overall, hemi‐epiphytic ferns exhibited traits that share characteristics of both terrestrial and epiphytic species. Our findings clearly demonstrate the prevalence of water conservatism in both epiphytic and hemi‐epiphytic ferns, via selection for anatomical and structural traits that avoid leaf water stress. Even with likely evolutionarily constrained physiological function, adaptations for drought avoidance have allowed epiphytic ferns to successfully endure the stresses of the canopy habitat. This article is protected by copyright. All rights reserved.
... For example, previous studies have indicated different leaf margin-temperature relationships for woody, herbaceous and ferny species. The leaf margin states of woody plants usually respond effectively to the macroenvironment because of the longer lifespan of such plants (Traiser et al., 2005), whereas those of herbaceous and ferny species are often less affected by climate due to their distinct hydraulic conductivity and leaf venation networks (Royer et al., 2012;Peppe et al., 2014). Similarly, Bailey & Sinnott (1916) found different percentages of entire-leaved species among trees, shrubs and herbs, and these percentages varied in tropical and temperate regions. ...
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AimLeaf margin states have been found to be strongly related to temperature, and hence have been used to reconstruct palaeotemperatures. Here, we aimed to explore the uncertainties and conditions of use of this technique in China by testing the influences of plant life-form, precipitation and evolutionary history on the relationship between percentage of untoothed species and temperature. LocationChina. Methods Using distribution maps and leaf margin states (untoothed versus toothed) of 10,480 Chinese woody dicots and dated family-level phylogenies, we evaluated the phylogenetic signal of leaf margin state, and demonstrated the variation in the patterns of leaf margin percentage and the relationship with temperature across different life-forms (evergreen and deciduous; trees, shrubs and lianas), regions with different precipitation and species quartiles with different family ages. ResultsSignificant phylogenetic signals were found for the percentage of untoothed species within families. Relationships between leaf margin percentage and temperature were: (1) weak or insignificant for all woody dicots, shrubs, evergreen and deciduous dicots, but strong for trees and lianas; (2) significantly enhanced with increasing precipitation, and (3) significantly weakened for trees belonging to old families. Main conclusionsOur results showed the complete leaf margin spectrum found in China and revealed great uncertainties in its relationship with temperature induced by life-form, precipitation and evolutionary history. These findings suggest that analysis of leaf margins for palaeotemperature reconstruction should be done cautiously: (1) only dicot trees with a relatively young family age can be used and their leaf margin states are more strongly affected by winter cold than by mean annual temperature; (2) the transfer function between leaf margin percentage and temperature is only reliable in humid and semi-humid regions of China.
... Some recent studies have shown that the stomatal behaviors of extant ferns and seed plants have different metabolic control mechanisms, including responses to abscisic acid and epidermal cell turgor (Brodribb et al., 2009;Brodribb and McAdam, 2011). Leaves of ferns and seed plants show additional differences in the relationship between leaf physiognomy and environmental factors, such as temperature (Peppe et al., 2014), so that different plant groups may need different models of biophysics and physiology. ...
... These changes in the Crenulopteris species coincided with wider changes in the character of palaeotropical vegetation to what is in effect more of a Stephanian (or Late Pennsylvanian) aspect, probably in response to a combination of regional tectonic instability and climate change (Cleal et al. 2010(Cleal et al. , 2011. The adaptive significance of the observed changes is difficult to determine, however, and recent evidence from extant ferns has suggested that climate generally has little effect on their foliar physiognomy (Peppe et al. 2014). ...
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Amongst the species referred to the genus Lobatopteris Wagner, 1959126. Wagner, R. H. 1959. Some Stephanian pecopterids from NW Spain. Mededelingen van de Geologische Stichting, New Series, 12, 5–23.View all references, three are especially abundant: Lobatopteris micromiltonii (Bertrand ex Corsin) Wagner, Lobatopteris vestita sensu Wagner (1959)126. Wagner, R. H. 1959. Some Stephanian pecopterids from NW Spain. Mededelingen van de Geologische Stichting, New Series, 12, 5–23.View all references and Lobatopteris lamuriana (Heer) Wagner. However, despite their biostratigraphical significance the taxonomy of these three species has remained poorly resolved and their nomenclature, typification and generic position problematical. This paper attempts to correct these deficiencies and, based upon new characters, transfers these taxa to the new genus Crenulopteris Wittry et al. gen. nov. Biostratigraphically, reassignment of these taxa does not impact the validity of the scheme introduced by Wagner (1984)131. Wagner, R. H. 1984. Megafloral zones of the Carboniferous. Pp. 109–134 in M. Gordon (ed) Neuvieme Congrès International de Stratigraphie et de Géologie du Carbonifère, Washington and Urbana, May 17–26, 1979. Volume 2. Southern Illinois University Press, Carbondale and Edwardsville.View all references and modified by Cleal (1991)21. Cleal, C. J. 1991. Carboniferous and Permian biostratigraphy. Pp. 182–215 in C. J. Cleal (ed.) Plant fossils in geological investigation: the Palaeozoic. Ellis Horwood, Chichester.View all references, but does necessitate the re-naming of some biozones.
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Broad scaling relationships between leaf size and function do not take into account that leaves of different size may contain different fractions of support in petiole and mid-rib. The fractions of leaf biomass in petiole, mid-rib and lamina, and the differences in chemistry and structure among mid-ribs, petioles and laminas were investigated in 122 species of contrasting leaf size, life form and climatic distribution to determine the extent to which differences in support modify whole-lamina and whole-leaf structural and chemical characteristics, and the extent to which size-dependent support investments are affected by plant life form and site climate. For the entire data set, leaf fresh mass varied over five orders of magnitude. The percentage of dry mass in mid-rib increased strongly with lamina size, reaching more than 40 % in the largest laminas. The whole-leaf percentage of mid-rib and petiole increased with leaf size, and the overall support investment was more than 60 % in the largest leaves. Fractional support investments were generally larger in herbaceous than in woody species and tended to be lower in Mediterranean than in cool temperate and tropical plants. Mid-ribs and petioles had lower N and C percentages, and lower dry to fresh mass ratio, but greater density (mass per unit volume) than laminas. N percentage of lamina without mid-rib was up to 40 % higher in the largest leaves than the total-lamina (lamina and mid-rib) N percentage, and up to 60 % higher than whole-leaf N percentage, while lamina density calculated without mid-rib was up to 80 % less than that with the mid-rib. For all leaf compartments, N percentage was negatively associated with density and dry to fresh mass ratio, while C percentage was positively linked to these characteristics, reflecting the overall inverse scaling between structural and physiological characteristics. However, the correlations between N and C percentages and structural characteristics differed among mid-ribs, petioles and laminas, implying that the mass-weighted average leaf N and C percentage, density, and dry to fresh mass ratio can have different functional values depending on the importance of within-leaf support investments. These data demonstrate that variation in leaf size is associated with major changes in within-leaf support investments and in large modifications in integrated leaf chemical and structural characteristics. These size-dependent alterations can importantly affect general leaf structure vs. function scaling relationships. These data further demonstrate important life-form effects on and climatic differentiation in foliage support costs.
Article
Evidence for convergence in biomechanical and anatomical features of leaves (elastic modulus E, second moment of area I, taper of petioles, the longitudinal distribution of petiolar and laminar weight, and volumes of tissues) is presented based on a survey of 22 species (distributed among dicots, monocots, and ferns). In general, regardless of taxonomic affinity, petioles were found to be mechanically constructed in one of two ways: Type I petioles-as cantilevered, end-loaded beams with relatively uniform flexural stiffness (EI) (simple and palmate leaves); and Type II petioles-as tapered cantilevered beams whose static loadings (biomass) and EI increase basipetally (pinnate leaves). In general, collenchyma and sclerenchyma were found to be peripherally located in transections through Type I and II petioles, respectively. Statistical analyses within each species and among species with either type of petiole indicated that EI ≈ k1 Lp(2.98) and EI ≈ k2 Lp(2.05) for Type I and II petioles, respectively, where k1 and k2 are dimensional constants and Lp is petiolar length. The data are interpreted to indicate that Type I and II petioles mechanically operate to deal with static loadings in two distinct ways, such that Type II petioles function in an analogous manner to branches supporting separate leaves (leaflets). The convergence in mechanical "designs" among taxonomically distinct lineages (angiosperms and ferns) is interpreted as evidence for selection on mechanical attributes of load supporting structures (petioles).
Article
Evidence for convergence in biomechanical and anatomical features of leaves (elastic modulus E, second moment of area I, taper of petioles, the longitudinal distribution of petiolar and laminar weight, and volumes of tissues) is presented based on a survey of 22 species (distributed among dicots, monocots, and ferns). In general, regardless of taxonomic affinity, petioles were found to be mechanically constructed in one of two ways: Type I petioles-as cantilevered, end-loaded beams with relatively uniform flexural stiffness (EI) (simple and palmate leaves); and Type II petioles-as tapered cantilevered beams whose static loadings (biomass) and EI increase basipetally (pinnate leaves). In general, collenchyma and sclerenchyma were found to be peripherally located in transections through Type I and II petioles, respectively. Statistical analyses within each species and among species with either type of petiole indicated that EI ≈ k1Lp2.98 and EI ≈ k2Lp2.05 for Type I and II petioles, respectively, where k1 and k2 are dimensional constants and Lp is petiolar length. The data are interpreted to indicate that Type I and II petioles mechanically operate to deal with static loadings in two distinct ways, such that Type II petioles function in an analogous manner to branches supporting separate leaves (leaflets). The convergence in mechanical "designs" among taxonomically distinct lineages (angiosperms and ferns) is interpreted as evidence for selection on mechanical attributes of load supporting structures (petioles).
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Leaf physiognomy (size and shape) in fossils is commonly used to reconstruct terrestrial paleoclimate. Physiognomic leaf-climate methods are underpinned mostly by the covariation between toothed margins and mean annual temperature (MAT) and between leaf size and mean annual precipita-tion. Digital leaf physiognomy, a multivariate method based largely on variables that are functionally linked to climate and that can be measured by computer algorithm, minimizes many of the deficiencies present in other approaches. Nevertheless, the relationships between MAT and many physiognomic vari-ables, especially tooth-related variables, are confounded by leaf thickness, leaf habit (deciduous vs. ever-green), and phylogenetic history. Until these factors are properly accounted for, a minimum error in MAT of ±4 °C for digital leaf physiognomy and ±5 °C for other methods should be assumed.
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Precambrian life fungi, bacteria and lichens algae bryophytes terrestrialization of the land the structure and organization of vascular plants early land plants with conducting tissue lycopods sphenophytes ferns progymnosperms origin and evolution of the seed habit palaeozoic seed ferns mesozoic seed ferns palaeozoic and mesozoic foliage cycadophytes ginkgophytes gymnsoperms with obscure affinities cordaites conifers flowering plants plant/animal interactions.
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Leaves with toothed and lobed margins are frequent in deciduous forests but are rare in moist tropical forests. We hypothesize that leaf teeth may be important to deciduous species as sites of precocious, early season photosynthesis. To test this hypothesis we dosed leaves with 14CO2 and used autoradiography to examine the spatial distribution of photosynthesis within immature leaves of 18 woody species of North Carolina Piedmont forests. We found a significant concentration of early season photosynthesis on the margins of eight species with prominent teeth or lobes, but not in seven toothed or lobed leaf species and in none of the four entire-leaf species.
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Question: A set of easily-measured ('soft') plant traits has been identified as potentially useful predictors of ecosystem functioning in previous studies. Here we aimed to discover whether the screening techniques remain operational in widely contrasted circumstances, to test for the existence of axes of variation in the particular sets of traits, and to test for their links with 'harder' traits of proven importance to ecosystem functioning. Location: central-western Argentina, central England, north-ern upland Iran, and north-eastern Spain. Recurrent patterns of ecological specialization: Through ordination of a matrix of 640 vascular plant taxa by 12 stand-ardized traits, we detected similar patterns of specialization in the four floras. The first PCA axis was identified as an axis of resource capture, usage and release. PCA axis 2 appeared to be a size-related axis. Individual PCA for each country showed that the same traits remained valuable as predictors of resource capture and utilization in all of them, despite their major differences in climate, biogeography and land-use. The results were not significantly driven by particular taxa: the main traits determining PCA axis 1 were very similar in eudicotyledons and monocotyledons and Asteraceae, Fabaceae and Poaceae. Links between recurrent suites of 'soft' traits and 'hard' traits: The validity of PCA axis 1 as a key predictor of resource capture and utilization was tested by comparisons between this axis and values of more rigorously established predictors ('hard' traits) for the floras of Argentina and England. PCA axis 1 was correlated with variation in relative growth rate, leaf nitrogen content, and litter decomposition rate. It also coincided with palatability to model generalist herbivores. Therefore, location on PCA axis 1 can be linked to major ecosystem processes in those habitats where the plants are dominant. Conclusion: We confirm the existence at the global scale of a major axis of evolutionary specialization, previously recog-nised in several local floras. This axis reflects a fundamental trade-off between rapid acquisition of resources and conserva-tion of resources within well-protected tissues. These major trends of specialization were maintained across different envi-ronmental situations (including differences in the proximate causes of low productivity, i.e. drought or mineral nutrient deficiency). The trends were also consistent across floras and major phylogenetic groups, and were linked with traits di-rectly relevant to ecosystem processes.
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The leaves of extant terrestrial plants show highly diverse and elaborate patterns of leaf venation. One fundamental feature of many leaf venation patterns, especially in the case of angiosperm leaves, is the presence of anastomoses. Anastomosing Veins distinguish a network topologically from a simple dendritic (tree-like) pattern which represents the primitive venation architecture. The high degree of interspecific variation of entire venation patterns as well as phenotypic plasticity of some venation properties, such as venation density, indicate the high selective pressure acting on this branching system. Few investigations deal with functional properties of the leaf venation system. The interrelationships between topological or geometric properties of the various leaf venation patterns and functional aspects are far from being well understood. In this review we summarize current knowledge of interrelationships between the form and function of leaf venation and the evolution of leaf venation patterns. Since the functional aspects of architectural features of different leaf venation patterns are considered, the review also refers to the topic of individual and intraspecific variation. One basic function of leaf venation is represented by its contribution to the mechanical behaviour of a leaf. Venation geometry and density influences mechanical stability and may affect, for example, susceptibility to herbivory. Transport of water and carbohydrates is the other basic function of this system and the transport properties are also influenced by the venation architecture. These various functional aspects can be interpreted in an ecophysiological context. (C) 2001 Annals of Botany Company.
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Large-fronded tree ferns are critical components of many tropical forests. We investigated frond and whole-plant allometries for Hawaiian keystone species Cibotium glaucum, for prediction and to compare with global scaling relationships. We found that C. glaucum fronds maintain geometric proportionality across a wide range of plant and frond sizes. These relationships result in strong allometries that permit rapid field estimation of frond size from simple linear dimensions. C. glaucum frond allometries complied with intra- and interspecific global trends for leaf area versus mass established for much smaller-leafed species, indicating ‘diminishing returns’ in photosynthetic area per investment in mass for larger fronds. The intraspecific trend was related to declining water content in larger fronds, but not to a significantly larger investment in stipe or rachis relative to lamina. However, C. glaucum complied with the global interspecific trends for greater allocation to support structures in larger leaves. Allometries for frond number and size versus plant height showed that as plants increase in height, frond production and/or retention progressively declines, and the increases of leaf size tend to level off. These frond and whole plant-level relationships indicate the potential for estimating frond area and mass at landscape scale to enrich studies of forest dynamics.
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Why the leaves of cold temperate deciduous and moisture-loving angiosperms are so often toothed has long puzzled biologists because the functional consequences of teeth remain poorly understood. Here we provide functional and structural evidence that marginal leaf teeth of Chloranthus japonicus, an understory herb, enable the release of guttation sap during root pressure. When guttation from teeth hydathodes was experimentally blocked, we found that the leaf intercellular airspaces became flooded. Measurements of chlorophyll a fluorescence revealed that internal flooding resulted in an inhibition of photosynthesis, most likely through the formation of a film of water within the leaf that reduced CO2 diffusion. Comparing a developmental series of leaves with and without teeth experimentally covered with wax, we found that teeth did not affect overall leaf stomatal conductance and CO2 uptake. However, maximal and effective light-saturation PSII quantum yields of teeth were found to be lower or equal to the surrounding lamina throughout leaf ontogeny. Collectively, our results suggest hydathodes and their development on teeth apices enable the avoidance of mesophyll flooding by root pressure. We discuss how these new findings bear on the potential physiological interpretations of models that apply leaf marginal traits to infer ancient climates.
Article
Premise of the study: Leaf-margin state (toothed vs. untoothed) forms the basis of several popular methods for reconstructing temperature. Some potential confounding factors have not been investigated with large data sets, limiting our understanding of the adaptive significance of leaf teeth and their reliability to reconstruct paleoclimate. Here we test the strength of correlations between leaf-margin state and deciduousness, leaf thickness, wood type (ring-porous vs. diffuse-porous), height within community, and several leaf economic variables. Methods: We assembled a trait database for 3549 species from six continents based on published and original data. The strength of associations between traits was quantified using correlational and principal axes approaches. Key results: Toothed species, independent of temperature, are more likely to be deciduous and to have thin leaves, a high leaf nitrogen concentration, a low leaf mass per area, and ring-porous wood. Canopy trees display the highest sensitivity between leaf-margin state and temperature; subcanopy plants, especially herbs, are less sensitive. Conclusions: Our data support hypotheses linking the adaptive significance of teeth to leaf thickness and deciduousness (in addition to temperature). Toothed species associate with the "fast-return" end of the leaf economic spectrum, providing another functional link to thin leaves and the deciduous habit. Accounting for these confounding factors should improve climate estimates from tooth-based methods.
Article
In palaeobotany, leaf venation density is still primarily used as a taxonomic character although numerous studies on recent plants reveal that leaf venation density may be influenced by various environmental factors. To promote the use of leaf venation density as a palaeoclimate/palaeoenvironmental proxy we give a brief review of these studies and provide some additional data. Our review shows that environmental factors that increase transpiration of plants or decrease water availability also tend to increase the leaf venation density. Based on the analysis of leaves of some recent and fossil plants we found: (1) Venation density may be measured as vein length per area or as distance between veins, but the first parameter is more reliable. (2) Depending on the plant species, leaf venation density may or may not vary with leaf size. This `leaf size effect' has to be taken into account when leaf venation density is to be used as a palaeoclimate/ palaeoenvironmental proxy. (3) No significant effect of a changing atmospheric carbon dioxide concentration on leaf venation density was observed. (4) In Permian seed plants, intraspecific variation of leaf venation density was similar to that observed in modern angiosperms. Obviously, even in these seed plants, leaf venation density can be used as a palaeoclimate/palaeoenvironmental proxy.
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The mechanical behaviour of large foliage leaves in response to static and dynamic mechanical forces is reviewed in the context of a few basic engineering principles and illustrated in terms of species drawn from a variety of vascular plant lineages. When loaded under their own weight or subjected to externally applied forces, petioles similtaneous bend and twist, and thus mechanically operate as cantilevered beams. The stresses that develop in petioles reach their maximum intensities either at their surfaces or very near their centroid axes, where they are accomodated by either living and hydrostatic tissues(parenchyma and collenchyma) or dead and stiff tissues(sclerenchyma and vascular fibres) depending on the size of the leaf and the species from which it is drawn. Allometric analyses of diverse species indicate size-dependent variations in petiole length, transverse shape, geometry and stiffness that accord well with those required to maintain a uniform tip-deflection for leaves with laminae differing in mass. When dynamically loaded, the laminae of many broad-leaved species fold and curl into streamlined objects, thereby the reducing forces that they experience and transmit to their subtending petioles and stems. From a mechanical perspective, the laminae of these species operate as stress-skin panels that distribute point loads more or less equally over their entire surface. Although comparatively little is known about the mechanical structure and behaviour of foliage leaves, new advances in engineering theory and computer analyses reveal these organs to be far more complex than previously thought. For example, finite element analyses of the base of palm leaves reveal that stresses decreased when these structures are composed of anisotropic as opposed to isotropic materials(tissues).
Article
The ferns comprise one of the most ancient tracheophytic plant lineages, and occupy habitats ranging from tundra to deserts and the equatorial tropics. Like their nearest relatives the conifers, modern ferns possess tracheid-based xylem but the structure-function relationships of fern xylem are poorly understood. Here, we sampled the fronds (megaphylls) of 16 species across the fern phylogeny, and examined the relationships among hydraulic transport, drought-induced cavitation resistance, the xylem anatomy of the stipe, and the gas-exchange response of the pinnae. For comparison, the results are presented alongside a similar suite of conifer data. Fern xylem is as resistant to cavitation as conifer xylem, but exhibits none of the hydraulic or structural trade-offs associated with resistance to cavitation. On a conduit diameter basis, fern xylem can exhibit greater hydraulic efficiency than conifer and angiosperm xylem. In ferns, wide and long tracheids compensate in part for the lack of secondary xylem and allow ferns to exhibit transport rates on a par with those of conifers. We suspect that it is the arrangement of the primary xylem, in addition to the intrinsic traits of the conduits themselves, that may help explain the broad range of cavitation resistance in ferns.
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Many key aspects of early angiosperms are poorly known, including their ecophysiology and associated habitats. Evidence for fast-growing, weedy angiosperms comes from the Early Cretaceous Potomac Group, where angiosperm fossils, some of them putative herbs, are found in riparian depositional settings. However, inferences of growth rate from sedimentology and growth habit are somewhat indirect; also, the geographic extent of a weedy habit in early angiosperms is poorly constrained. Using a power law between petiole width and leaf mass, we estimated the leaf mass per area (LMA) of species from three Albian (110-105 Ma) fossil floras from North America (Winthrop Formation, Patapsco Formation of the Potomac Group, and the Aspen Shale). All LMAs for angiosperm species are low (<125 g/m(2); mean = 76 g/m(2)) but are high for gymnosperm species (>240 g/m(2); mean = 291 g/m(2)). On the basis of extant relationships between LMA and other leaf economic traits such as photosynthetic rate and leaf lifespan, we conclude that these Early Cretaceous landscapes were populated with weedy angiosperms with short-lived leaves (<12 mo). The unrivalled capacity for fast growth observed today in many angiosperms was in place by no later than the Albian and likely played an important role in their subsequent ecological success.
Article
• Paleobotanists have long used models based on leaf size and shape to reconstruct paleoclimate. However, most models incorporate a single variable or use traits that are not physiologically or functionally linked to climate, limiting their predictive power. Further, they often underestimate paleotemperature relative to other proxies. • Here we quantify leaf-climate correlations from 92 globally distributed, climatically diverse sites, and explore potential confounding factors. Multiple linear regression models for mean annual temperature (MAT) and mean annual precipitation (MAP) are developed and applied to nine well-studied fossil floras. • We find that leaves in cold climates typically have larger, more numerous teeth, and are more highly dissected. Leaf habit (deciduous vs evergreen), local water availability, and phylogenetic history all affect these relationships. Leaves in wet climates are larger and have fewer, smaller teeth. Our multivariate MAT and MAP models offer moderate improvements in precision over univariate approaches (± 4.0 vs 4.8°C for MAT) and strong improvements in accuracy. For example, our provisional MAT estimates for most North American fossil floras are considerably warmer and in better agreement with independent paleoclimate evidence. • Our study demonstrates that the inclusion of additional leaf traits that are functionally linked to climate improves paleoclimate reconstructions. This work also illustrates the need for better understanding of the impact of phylogeny and leaf habit on leaf-climate relationships.
Article
Ecology Letters (2011) 14: 91–100 The leaf economics spectrum describes biome-invariant scaling functions for leaf functional traits that relate to global primary productivity and nutrient cycling. Here, we develop a comprehensive framework for the origin of this leaf economics spectrum based on venation-mediated economic strategies. We define a standardized set of traits – density, distance and loopiness – that provides a common language for the study of venation. We develop a novel quantitative model that uses these venation traits to model leaf-level physiology, and show that selection to optimize the venation network predicts the mean global trait–trait scaling relationships across 2548 species. Furthermore, using empirical venation data for 25 plant species, we test our model by predicting four key leaf functional traits related to leaf economics: net carbon assimilation rate, life span, leaf mass per area ratio and nitrogen content. Together, these results indicate that selection on venation geometry is a fundamental basis for understanding the diversity of leaf form and function, and the carbon balance of leaves. The model and associated predictions have broad implications for integrating venation network geometry with pattern and process in ecophysiology, ecology and palaeobotany.
Article
ABSTRACT 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 (Nmass) and photosynthetic capacity (Amass). 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) Amass was lower at a given Nmass, or the increase in Amass was less for a given increase in Nmass. 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.
Article
Fifteen petioles and rachises from three dicotyledon species (Acer saccharum, A. negundo, and Aesculus hippocastanum), a palm (Chamaedorea erumpens), and a fern (Cyrtomium falcatum) were used to test the hypothesis of 'economy in design' in terms of the design principle of uniform strength, i.e. a beam in which the section modulus (Z) varies along beam-length (L) in the same proportion as the bending moment (M). Such a beam is 'economical' regarding the amount of material used in its 'construction' because each of its cross section has the minimum transverse area required to satisfy the conditions of strength. The extent to which the morphology of a petiole or rachis conformed with this design principle was initially evaluated by normalizing Z (measured at a distance, x, from the tip of a petiole or rachis) with respect to the magnitude of Z measured at the base of the petiole. The normalized values were plotted against normalized petiole-rachis length (x/L). The design principle was judged to be demonstrated when such a plot was found to be isometric, i.e. when the plot had a slope of unity. This procedure was tested further by plotting M/Z vs. x/L for representative leaves of C. erumpens and A. saccharum, and judged adequate. The allometries of all six simple/palmate leaves were found not agree with the design principle. The taperings of nine petioles and rachises from pinnate leaves were consistent with the design principle. This was interpreted to provide circumstantial evidence for 'economy in design' in the petioles of some pinnate leaves and evidence that the mechanical 'design' of the petioles of some simple/palmate leaves differs substantially from that of pinnate leaves.Copyright 1993, 1999 Academic Press
Article
* The hydraulic plumbing of vascular plant leaves varies considerably between major plant groups both in the spatial organization of veins, as well as their anatomical structure. * Five conifers, three ferns and 12 angiosperm trees were selected from tropical and temperate forests to investigate whether the profound differences in foliar morphology of these groups lead to correspondingly profound differences in leaf hydraulic efficiency. * We found that angiosperm leaves spanned a range of leaf hydraulic conductance from 3.9 to 36 mmol m2 s-1 MPa-1, whereas ferns (5.9-11.4 mmol m-2 s-1 MPa-1) and conifers (1.6-9.0 mmol m-2 s-1 MPa-1) were uniformly less conductive to liquid water. Leaf hydraulic conductance (Kleaf) correlated strongly with stomatal conductance indicating an internal leaf-level regulation of liquid and vapour conductances. Photosynthetic capacity also increased with Kleaf, however, it became saturated at values of Kleaf over 20 mmol m-2 s-1 MPa-1. * The data suggest that vessels in the leaves of the angiosperms studied provide them with the flexibility to produce highly conductive leaves with correspondingly high photosynthetic capacities relative to tracheid-bearing species.
Article
Fitting a line to a bivariate dataset can be a deceptively complex problem, and there has been much debate on this issue in the literature. In this review, we describe for the practitioner the essential features of line-fitting methods for estimating the relationship between two variables: what methods are commonly used, which method should be used when, and how to make inferences from these lines to answer common research questions. A particularly important point for line-fitting in allometry is that usually, two sources of error are present (which we call measurement and equation error), and these have quite different implications for choice of line-fitting method. As a consequence, the approach in this review and the methods presented have subtle but important differences from previous reviews in the biology literature. Linear regression, major axis and standardised major axis are alternative methods that can be appropriate when there is no measurement error. When there is measurement error, this often needs to be estimated and used to adjust the variance terms in formulae for line-fitting. We also review line-fitting methods for phylogenetic analyses. Methods of inference are described for the line-fitting techniques discussed in this paper. The types of inference considered here are testing if the slope or elevation equals a given value, constructing confidence intervals for the slope or elevation, comparing several slopes or elevations, and testing for shift along the axis amongst several groups. In some cases several methods have been proposed in the literature. These are discussed and compared. In other cases there is little or no previous guidance available in the literature. Simulations were conducted to check whether the methods of inference proposed have the intended coverage probability or Type I error. We identified the methods of inference that perform well and recommend the techniques that should be adopted in future work.
Article
Recent work has identified a worldwide "economic" spectrum of correlated leaf traits that affects global patterns of nutrient cycling and primary productivity and that is used to calibrate vegetation-climate models. The correlation patterns are displayed by species from the arctic to the tropics and are largely independent of growth form or phylogeny. This generality suggests that unidentified fundamental constraints control the return of photosynthates on investments of nutrients and dry mass in leaves. Using novel graph theoretic methods and structural equation modeling, we show that the relationships among these variables can best be explained by assuming (1) a necessary trade-off between allocation to structural tissues versus liquid phase processes and (2) an evolutionary tradeoff between leaf photosynthetic rates, construction costs, and leaf longevity.
Article
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.
The worldwide leaf eco-nomics spectrum
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Paleobotany: The biology and evolution of fossil plants Leaf venation density as a cli-mate and environmental proxy: A critical review and new data
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Climate reconstruction from leaf size and shape: New developments and challenges Reconstructing Earth's deep-time climate: The state of the art in 2012 Leaf eco-nomic traits from fossils support a weedy habit for early angiosperms
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Communities and ecosystems Modulation of leaf eco-nomic traits and trait relationships by climate
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Testing climatic influences on leaf shape across the vascular plant tree of life
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