Karl J Niklas

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Verified

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• Ph.D
• Professor Emeritus at Cornell University

The evolution of biparental sexual reproduction in animals and plants is a prominent focus in modern biology. One hundred and fifty years ago, the German biologist Julius Sachs (1832–1897) published the fourth and final edition of his influential Textbook of Botany. In the text, he referred to the work of Wilhelm Hofmeister (1824–1877) and proposed...

The earliest seed plants occurred in the Late Devonian (Famennian). However, why and how they rapidly diversified remain long-standing mysteries. We investigated the early evolution of seed plants based on a new ovule and evaluated wind pollination performance of the earliest cupulate ovules by using computational fluid dynamics simulations. Zaijun...

Zoologists have adduced morphological convergence among embryonic stages of closely related taxa, which has been called the phylotypic stage of embryogenesis. Transcriptomic analyzes reveal an hourglass pattern of gene expression during plant and animal embryogenesis, characterized by the accumulation of evolutionarily older and conserved transcrip...

Key message The Montgomery equation, which assumes a proportional relationship between the tepal area and the product of the tepal length and width, is validated using data drawn from four Magnolia species. Abstract An important metric of floral non-reproductive size is individual petal or tepal area (A). The Montgomery equation (ME) estimates A b...

The concept of a geometric series (GS) plays an important role in mathematics. However, it has been neglected in describing biological size series. Herein, we show that a GS describes the nonreproductive (perianth) parts of the flowers of four Magnoliaceae species and two Rosaceae species and the leaves of 60 Alangium chinense and 60 Shibataea chin...

Premise Although previous studies have reported a positive correlation between leaf dry mass per unit area (LMA) and mean leaf thickness (LT), the LMA versus LT scaling relationship has not been determined due to limited sample sizes, despite its importance in estimating leaf bulk tissue density (mass per unit volume). Methods This issue was addre...

Regreening efforts in deserts have been implemented globally to combat land degradation and desert expansion, but how they affect above‐ and belowground community succession and assembly processes remains unknown. Here, we examined variations in plant and soil microbial community attributes along a 53‐year restoration chronosequence following the e...

The primary vascular system of plants (the stele) has attracted interest from paleobotanists, developmental biologists, systematists, and physiologists for nearly two centuries. Ferns, with their diverse stelar morphology, deep evolutionary history, and prominent fossil record, have been a major focus in studies of the stele. To explain the diversi...

Inorganic carbon is an important component of soil carbon stocks, exerting a profound influence on climate change and ecosystem functioning. Drylands account for approximately 80% of the global soil inorganic carbon (SIC) pool within the top 200 cm. Despite its paramount importance, the components of SIC and their contributions to CO 2 fluxes have...

Background and aims The Montgomery-Koyama-Smith (MKS) equation predicts that total leaf area per shoot is proportional to the product of the sum of individual leaf widths and maximum individual leaf length, which has been validated for some herbaceous and woody plants. The equation is also predicted to be valid in describing the relationship betwee...

Studies on plant diversity are usually based on the total number of species in a community. However, few studies have examined species richness (SR) of different plant life forms in a community along large-scale environmental gradients. Particularly, the relative importance (RIV) of different plant life forms in a community and how they vary with e...

The “leafing intensity premium” hypothesis proposes that leaf size results from natural selection acting on different leafing intensities, i.e., the number of leaves per unit shoot volume or mass. The scaling relationships among various above-ground functional traits in the context of this hypothesis are important for understanding plant growth and...

Introduction The allocation of nitrogen (N) and phosphorus (P) among plant organs is an important strategy affecting growth and development as well as ecological processes in terrestrial ecosystems. However, due to lack of systematic investigation data, the allocation strategies of N and P in the three primary plant organs (e.g., leaves, stems and...

There is a lack of research on whether tree size affects lamina and petiole biomass allocation patterns, whereas the trade‐off between leaf biomass allocated to the lamina and the petiole is of significance when considering the hydraulic and mechanical function of the leaf as a whole. Here, Camptotheca acuminata Decne was selected for study because...

Total leaf area per plant is an important measure of the photosynthetic capacity of an individual plant that together with plant density drives the canopy leaf area index, that is, the total leaf area per unit ground area. Because the total number of leaves per plant (or per shoot) varies among conspecifics and among mixed species communities, this...

Establishing planted forests (PF) by afforestation and naturally regenerating forests (NF) are important measures of enhance carbon (C) sequestration in terrestrial ecosystems. However, the difference of biomass C stocks and allocation between NF and PF and their determinants in water-limited areas remain unclear. To address this gap, we conducted...

Previous studies have validated a performance equation (PE) and its generalized version (GPE) in describing the rotated and right-shifted Lorenz curves of organ size (e.g., leaf area and fruit volume) distributions of herbaceous plants. Nevertheless, there are still two questions that have not been adequately addressed by prior work: (i) whether th...

Background and aims: Leaf area (A) is a crucial indicator of the photosynthetic capacity of plants. The Montgomery equation (ME), which hypothesizes that A is proportional to the product of leaf length (L) and width (W), is a valid tool for nondestructively measuring A for many broad-leaved plants. At present, the methods used to compute L and W f...

The Lorenz curve is used to describe the relationship between the cumulative proportion of household income and the number of households of an economy. The extent to which the Lorenz curve deviates from the line of equality (i.e., y = x) is quantified by the Gini coefficient. Prior models are based on the simulated and empirical data of income dist...

Although herbivores are well known to incur positive density‐dependent damage and mortality, thereby likely shaping plant community assembly, the response of belowground root feeders to changes in plant density has seldom been addressed. Locally rare plant species (with lower plant biomass per area) are often smaller with shallower roots than commo...

The vascular veins in photosynthetic leaves play an important role in transporting water and sugars throughout the plant body, and their venation pattern and vein density determine the hydraulic efficiency of the leaf. Likewise, stomatal density (SD) can influence photosynthetic gas exchange. However, the correlation between leaf vein density and S...

Synopsis The proportions in the size of the avian egg albumen, yolk, and shell are crucial for understanding bird survival and reproductive success because their relationships with volume and surface area can affect ecological and life history strategies. Prior studies have focused on the relationship between the albumen and the yolk, but little is...

Competition is an important factor influencing the structure and dynamics of plant communities, and understanding species coexistence. Tree architectural traits, such as height-to-diameter (H-D) and branch length-to-diameter (L-d) relationships influence species competitiveness through affecting light capture by altering the occupation of space. Un...

Predators may adapt to global warming via behavioural plasticity. However, empirical evidence showing such adaptations in terrestrial ecosystems is scarce. Here we report behavioural shifts that alter the web mesh size of two dominant predatory spider species in response to experimental warming in an alpine meadow field. Experimental large open-top...

Key message A significant scaling relationship between the perianth mass and area was detected using 306 flowers of Magnolia × soulangeana, and increases in mass failed to achieve proportional increases in area. Abstract The scaling relationship between leaf lamina mass and area has been explored extensively. However, this relationship for floral...

Background and Aims The form-function linkages and variation of fine root traits reflect adaptive strategies to cope with complex soil environments. However, their contributions to the root economics spectrum (RES) remain unclear. Methods We measured thirteen functional traits in the first four root orders of 59 subtropical woody species, includin...

Foliage leaves are essential for plant survival and growth, and how plants allocate biomass to their leaves reveals their economic and ecological strategies. Prior studies have shown that leaf-age significantly influences leaf biomass allocation patterns. However, unravelling the effects of ontogeny on partitioning biomass remains a challenge becau...

Stoichiometric rules may explain the allometric scaling among biological traits and body size, a fundamental law of nature. However, testing the scaling of elemental stoichiometry and growth to size over the course of plant ontogeny is challenging. Here, we used a fast‐growing bamboo species to examine how the concentrations and contents of carbon...

This article is a Commentary on D'Ario et al. (2024), 241: 937–949.

Key message A generalized performance equation is proposed to fit the Lorenz curve of the leaf size distribution of an individual plant and is validated using 12 individual bamboo plants. Abstract The goal of this study is to provide a rigorous tool to quantify the inequality of the leaf size distribution of an individual plant, thereby serving as...

Cortex radius (CR) and stele radius (SR) are important functional traits associated with the nutrient acquisition and transport functions of fine roots, respectively. However, for developmental and anatomical reasons, the resource acquisition-transport relationship of fine roots is expected to be different for different root orders. To address this...

Although many fruit geometries resemble a solid of revolution, this assumption has rarely been rigorously examined. To test this assumption, 574 fruits of Canarium album (Lour.) DC. which appear to have an ellipsoidal shape, were examined to determine the validity of a general avian-based egg-shape equation, referred to as the explicit Preston equa...

Key message Stomatal area is proportional to the product of stomatal length and width with a proportionality coefficient exceeding π/4 (indicating a deviation from an elliptical shape) for four Magnoliaceae species. Abstract Stomatal size is an important factor affecting the photosynthetic and transpiration rates of vascular plants. To examine sto...

Simple Summary Plant species diversity has been substantially studied in relation to livestock grazing intensity. However, the effect of grazing on arthropod species diversity has seldom been addressed. Here, we report the results of a two-year plant and arthropod survey from 2020 to 2021 for four levels of grazing intensity, including nongrazing (...

Egg geometry can be described using Preston's equation, which has seldom been used to calculate egg volume (V) and surface area (S) to explore S versus V scaling relationships. Herein, we provide an explicit re‐expression of Preston's equation (designated as EPE) to calculate V and S, assuming that an egg is a solid of revolution. The side (longitu...

Stomatal density (SD) is important to photosynthetic rates. However, it is time-consuming to measure SD. Here, we provide a method for estimating SD based on the scaling relationship between SD and mean nearest neighbour distance (MNND) of sampled stomatal centres. 397 leaves from eight Magnoliaceae species were used for this study. For each leaf,...

Global warming challenges predators by changing their abiotic and biotic environment. Although predators may adapt by virtue of behavioral plasticity, few studies have explored this behavior under field conditions. We conducted a field warming experiment in an alpine meadow using six large open-top chambers that increased mean annual temperature by...

Understanding the altitudinal patterns of plant stoichiometry in seeds is critical for characterizing important germination and dormancy strategies, soil seed bank composition, seed predation probability, efficiency of seed dispersal and seedling performance, and to predict how biodiversity might be influenced by climate change. However, our unders...

A review of the fossil record coupled with insights gained from molecular and developmental biology reveal a series of body plan transformations that gave rise to the first land plants. Across diverse algal clades, including the green algae and their descendants, the plant body plan underwent a unicellul ar $\to$ colonial $\to$ simple multicellular...

Evergreen and deciduous species co-exist in the subtropical forests in southeastern China. It has been suggested that phosphorus is the main limiting nutrient in subtropical forests, and that evergreen and deciduous species adopt different carbon capture strategies to deal with this limitation. However, these hypotheses have not been examined empir...

“Diminishing returns” in leaf economics occurs when increases in lamina mass (M), which can either be represented by lamina dry mass (DM) or fresh mass (FM), fail to produce proportional increases in leaf surface area (A), such that the scaling exponent (α) for the M vs. A scaling relationship exceeds unity (i.e., α > 1.0). Prior studies have shown...

Leaf functional traits are important indicators of plant growth and ecosystem dynamics. Despite a wealth of knowledge about leaf trait relationships, a mechanistic understanding of how biotic and abiotic factors quantitatively influence leaf trait variation and scaling is still incomplete. We propose that leaf water content (LWC) inherently affects...

Leaf shape and size can vary between hybrids and their parents. However, this has seldom been quantitatively tested. Photinia × fraseri is an important landscaping plant in East Asia as a hybrid between evergreen shrubs P. glabra and P. serratifolia. Its leaf shape looks like that of P. serratifolia. To investigate leaf shape, we used a general equ...

The quantification of the allocation of nitrogen (N) and phosphorus (P) among plant organs is essential to improve our understanding of plant growth, life‐history strategies and ecosystem nutrient and energy cycles. However, allocation strategies of N and P between terrestrial plant leaves and fine roots are unclear. Here, we compiled a global data...

The plant economics spectrum describes the trade‐off between plant resource acquisition and storage, and sheds light on plant responses to environmental changes. However, the data used to construct the plant economics spectrum comes mainly from seed plants, thereby neglecting vascular non‐seed plant lineages such as the ferns. To address this omiss...

Many natural objects exhibit radial or axial symmetry in a single plane. However, a universal tool for simulating and fitting the shapes of such objects is lacking. Herein, we present an R package called ‘biogeom’ that simulates and fits many shapes found in nature. The package incorporates novel universal parametric equations that generate the pro...

Dear colleagues, the association of tree consultants SAG Baumstatik e.V. would like to invite you to this upcoming event: In the course of the SAG Summer School 2022 in Trieste, a public conference with speakers of SAG Baumstatik and international guests will take place on Thursday, 21st of July 2022. There, lectures on some topics of the SAG Sum...

Earth’s drylands store large amounts of organic carbon and thus play an important role in regulating atmospheric CO2 concentrations and mitigating climate change. However, little is known about the magnitude and the drivers of organic carbon stocks because of limited data, in particular in desert ecosystems. To fill this gap, we surveyed 763 plots...

The material properties of the cells and tissues of an organism dictate, to a very large degree, the ability of the organism to cope with mechanical stress induced by externally applied forces. It is, therefore, critical to understand how these properties differ across diverse species and how they have evolved. Herein, a large data base (N = 84 spe...

The Montgomery equation predicts leaf area as the product of leaf length and width multiplied by a correction factor. It has been demonstrated to apply to a variety of leaf shapes. However, it is unknown whether tree size (measured as the diameter at breast height) affects leaf shape and size, or whether such variations in leaf shape can invalidate...

Premise of study: Competition is an important driver of tree mortality, and thus affects forest structure and dynamics. Tree architectural traits, such as height-to-diameter (H-D) and branch length-to-diameter (L-d) relationships are thought to influence species competitiveness by affecting light capture. Unfortunately, little is known about how t...

Background Nitrogen (N) and phosphorus (P) are important elements for plant metabolism and growth. Therefore, the quantification of the scaling relationship of N to P in plant organs can help us understand many fundamental ecological processes. The general scaling relationships between N and P in leaves and in fine roots have been reported. As comp...

Recently, a universal equation by Narushin, Romanov, and Griffin (hereafter, the NRGE) was proposed to describe the shape of avian eggs. While NRGE can simulate the shape of spherical, ellipsoidal, ovoidal, and pyriform eggs, its predictions were not tested against actual data. Here, we tested the validity of the NRGE by fitting actual data of egg...

Sexual dimorphism in body size has been observed for many insect species. However, whether dimorphism influences the flight performance for closely related insects or between the genders of conspecifics has seldom been examined. Wing loading (i.e., body mass/total wing area, WL = M/A) is an important indicator of flight efficiency and maneuverabili...

Leaf lamina mass and area are closely correlated with the photosynthetic capacity and competitive ability of plants, whereas leaf age has been demonstrated to affect physiological processes such as photosynthesis. However, it remains unknown whether the lamina mass vs. area scaling relationship is influenced by leaf age, which is important for unde...

Water use efficiency (WUE) links carbon and water cycling and has been recognized as important in understanding the carbon-water budget of terrestrial ecosystems. However, there are few studies comparing WUE at leaf and ecosystem levels in response to environmental variables on a global scale. Here, we compare global-scale patterns and the drivers...

Soil microbes play key roles in driving and regulating nutrient cycling in terrestrial ecosystems. However, a lack of global-scale information regarding the distribution of soil microbial biomass carbon (SMB C), nitrogen (SMB N), and phosphorus (SMB P) in terrestrial ecosystems has limited our ability to incorporate the broad-scale soil microbial n...

Julius Sachs (1832–1897), who has been quite rightly called “the father of plant physiology,” was a German physiologist of international standing, whose research interests contributed to virtually every branch of the plant sciences, and whose work presaged plant molecular biology and systems biology. Here, we focus on one of his last publications,...

Premise: Across species, main leaf vein density scales inversely with leaf area (A). Yet, minor vein density manifests no clear relationship with respect to A, despite having the potential to provide important insights into the trade-off among the investments in leaf mechanical support, hydraulics, and light interception. Methods: To examine thi...

Premise: The phenomenon called "diminishing returns" refers to the scaling relationship between lamina mass (M) vs. lamina area (A) in many species, i.e., M ∝ Aα>1 , where αis the scaling exponent exceeding unity. Prior studies have focused on the scaling relationships between lamina dry mass (DM) and A, or between fresh mass (FM) and A. However,...

The whole‐plant economics spectrum (PES) refers to the trade‐offs among the many plant functional traits that are commonly used as indicators of major adaptive strategies, thereby providing insights into plant distributions, ecosystem processes and evolution. However, there are few studies of what may be called the whole‐PES that integrates bark, w...

Virtually all forms of life, from single-cell eukaryotes to complex, highly differentiated multicellular organisms, exhibit a property referred to as symmetry. However, precise measures of symmetry are often difficult to formulate and apply in a meaningful way to biological systems, where symmetries and asymmetries can be dynamic and transient, or...

Determining large‐scale patterns of plant elemental concentrations and stoichiometry along environmental gradients is critical for understanding plant adaptive strategies and predicting ecosystem biogeochemistry processes. However, it remains unclear as to how plant carbon (C), nitrogen (N) and phosphorus (P) concentrations and their stoichiometry...

The shape of leaf laminae exhibits considerable diversity and complexity that reflects adaptations to environmental factors such as ambient light and precipitation as well as phyletic legacy. Many leaves appear to be elliptical which may represent a ‘default’ developmental condition. However, whether their geometry truly conforms to the ellipse equ...

Abiotic-biotic interactions have shaped organic evolution since life first began. Abiotic factors influence growth, survival, and reproductive success, whereas biotic responses to abiotic factors have changed the physical environment (and indeed created new environments). This reciprocity is well-illustrated by land plants who begin and end their e...

Fine-root nitrogen (N) and phosphorus (P) concentrations play an important role in driving ecological processes such as nutrient cycling in terrestrial ecosystems. Previous studies have demonstrated that the N versus P scaling relationship for fine roots (<2 mm in diameter) on average follows a 0.82-power law across plant functional groups and ecos...

Premise: Leaf mass (M) and lamina surface area (A) are important functional traits reported to obey a scaling relationship called "diminishing returns" (i.e., M ∝ Aα>1 ). Previous studies have focused primarily on eudicots and ignored whether the age of leaves affects the numerical value of the scaling exponent (i.e., α). Methods: The effect of...

Many plant species produce ovate leaves, but there is no general parametric model for describing this shape. Here, we used two empirical nonlinear equations, the beta and Lobry–Rosso–Flandrois (LRF) equations, and their modified forms (referred to as the Mbeta and MLRF equations for convenience), to generate bilaterally symmetrical curves along the...

Physical principles and laws determine the set of possible organismal phenotypes. Constraints arising from development, the environment, and evolutionary history then yield workable, integrated phenotypes. We propose a theoretical and practical framework that considers the role of changing environments. This 'ecomechanical approach' integrates func...

Dietary differences are often observed among generalist herbivores co‐occurring in the same community. However, the factors underlying the differences remain poorly understood. In the context of insect herbivores, we hypothesized that interspecific dietary differences are associated with life history traits. Specifically, we hypothesized that the s...

Climate change can indirectly affect ecosystem functions including detritus decomposition by modifying physiological traits, feeding behavior, and species interactions (including consumptive and non-consumptive top-down cascading effects) of decomposing arthropods. It is known that the effect of climate change on decomposition can be negative, neut...

The extent to which key factors at the global scale influence plant biomass allocation patterns remains unclear. Here, we provide a theory about how biotic and abiotic factors influence plant biomass allocation and evaluate its predictions using a large global database for forested communities. Our analyses confirm theoretical predictions that temp...

Nitrogen (N) and phosphorus (P) are associated with the life history of all organisms. Soil microbes play essential roles in nutrient cycling and ecosystem dynamics. As compared to plants, however, our understanding of the soil microbial N versus P scaling relationship remains limited. In this study, we used a comprehensive dataset comprising 2210...

Rare plant species often suffer less damage than common species because of positive density‐dependent herbivory, and it has been suggested that this ‘rare species advantage’ fosters plant species coexistence. However, it is unknown whether rare species have an advantage when pollination interactions are also considered. We hypothesized that a ‘posi...

The discipline called biomimetics attempts to create synthetic systems that model the behavior and functions of biological systems. At a very basic level, this approach incorporates a philosophy grounded in modeling either the behavior or properties of organic systems based on inferences of structure–function relationships. This approach has achiev...

Studies show that plant defenses influence the host‐use of herbivores and tend to be evolutionarily more labile than herbivore traits (e.g. feeding preferences). However, all previous studies have focused exclusively on non‐volatile plant defenses thereby overlooking the roles of plant volatiles. We hypothesized that volatiles are equally important...