A unifying concept for the dependence of whole-crop N:P ratio on biomass : theory and experiment

Background and Aims: Numerous estimates have been made of the concentrations of N and P required for good growth of crop species but they have not been defined by any unifying model. The aim of the present study was to develop such a model for the dependence of the N : P ratio on crop mass, to test its validity and to use it to identify elements of similarity between different crop species and wild plants. Methods: A model was derived between plant N : P ratio (Rw) and its dry biomass per unit area (W) during growth with near optimum nutrition by considering that plants consist of growth-related tissue and storage-related tissue with N : P ratios Rg and Rs, respectively. Testing and calibration against experimental data on different crop species led to a simple equation between Rw and W which was tested against independent experimental data. Key Results: The validity of the model and equation was supported by 365 measurements of Rw in 38 field experiments on crops. Rg and Rs remained approximately constant throughout growth, with average values of 11·8 and 5·8 by mass. The model also approximately predicted the relationships between leaf N and P concentrations in 124 advisory estimates on immature tissues and in 385 wild species from published global surveys. Conclusions: The N : P ratio of the biomass of very different crops, during growth with near optimum levels of nutrients, is defined entirely in terms of crop biomass, an average N : P ratio of the storage/structure-related tissue of the crop and an average N : P ratio of the growth-related tissue. The latter is similar to that found in leaves of many wild plant species, and even micro-organisms and terrestrial and freshwater autotrophs

Dynamique de la phénologie, de l’allométrie et du rendement des bleuetiers nains sauvages du Québec selon l’espèce et divers traitements agricoles

Le rendement des plants de bleuets sauvages est étroitement lié à plusieurs caractéristiques intrinsèques et extrinsèques. Pour ainsi améliorer la productivité, une meilleure compréhension de l’influence de l’architecture des plants, de la phénologie spécifique aux espèces et des traitements de fertilisation et de fauchage sur la production de fruit serait importante pour faire de meilleur choix de pratiques agricole en zone nordique. Pour ce faire, la première partie de cette étude porte sur la comparaison des traits phénologiques, architecturaux et allométriques entre les deux espèces présentes au Saguenay-Lac-Saint-Jean, soit Vaccinium angustifolium Aiton et Vaccinium myrtilloides Michaux. Dans la seconde partie de l’étude, ce sont les effets combinés sur les traits allométriques et le rendement de deux pratiques agricoles, soit le fauchage et l’application d’engrais, qui sont comparés dans une bleuetière en zone nordique. L’expérience s’est déroulée du printemps 2017 à l’automne 2018 sur une bleuetière commerciale située au nord du Saguenay-Lac-Saint-Jean. La combinaison de fauchage – mécanique ou mécanique et thermique – et d’engrais – minéral, organique ou sans – a été appliquée sur les champs. La phénologie des bourgeons, la croissance en hauteur et en longueur, la masse des fruits par plant et par parcelle ainsi que le nombre d’éléments sur la plante (bourgeon, feuille, fleur, fruit, etc.) ont été notés selon le type de production en cours dans les champs, soit l’année après fauchage (pruning year) ou l’année de récolte (harvesting year). La surface foliaire spécifique, la biomasse hors-sol des plants, l’aire et la biomasse des feuilles ont été estimées à partir de la prise de donnée sur 192 plants récoltés. La comparaison entre les espèces a permis de montrer des différences entre elles : d’abord leur phénologie diffère et le bourgeonnement des feuilles et des fleurs de V. myrtilloides est retardé, dû à un nombre plus important de composantes structurelles (bourgeon, fleur, feuille) comparativement à V. angustifolium. La biomasse des fruits est similaire entre les deux espèces : V. myrtilloides possède des fruits plus petits, mais en plus grande quantité, ce qui peut être expliqué par la limitation de la pollinisation et par une biomasse hors-sol importante. Par son retard dans la phénologie des fleurs, V. myrtilloides pourrait être l’espèce la mieux adaptée à la zone nordique pour résister au gel printanier, mais la pollinisation devrait être augmentée. Pour ce qui est des pratiques agricoles, l’application d’engrais, qu’il soit minéral ou organique, améliore la majorité des traits de la plante, dont la production de fruit après deux années. L’engrais organique n’a cependant réussi à atteindre les résultats de l’engrais minéral qu’après deux années, comme il a dû être dégradé avant d’être rendu disponible pour les plantes. Le fauchage thermique, appliqué en plus du fauchage mécanique, a accru certains traits végétatifs, comme la biomasse des feuilles et de la plante. D’ailleurs, deux modèles prévisionnels ont été produits et qui montre que le nombre de fleurs avec l’application d’engrais ainsi que la longueur des branches et la biomasse de la plante sont les facteurs qui expliquent le mieux le rendement en fruit. L’étude confirme que l’utilisation d’engrais dans les champs de bleuet en zone nordique est essentielle, mais une étude à plus long terme sur le fauchage thermique est nécessaire pour vérifier si ce type de fauchage amène réellement plus de bénéfices que de coûts

Disturbance and resource availability act differently on the same suite of plant traits: revisiting assembly hypotheses.

Understanding the mechanisms of trait selection at the scale of plant communities is a crucial step toward predicting community assembly. Although it is commonly assumed that disturbance and resource availability constrain separate suites of traits, representing the regenerative and established phases, respectively, a quantification and test of this accepted hypothesis is still lacking due to limitations of traditional statistical techniques. In this paper we quantify, using structural equation modeling (SEM), the relative contributions of disturbance and resource availability to the selection of suites of traits at the community scale. Our model specifies and reflects previously obtained ecological insights, taking disturbance and nutrient availability as central drivers affecting leaf, allometric, seed, and phenology traits in 156 (semi-) natural plant communities throughout The Netherlands. The common hypothesis positing that disturbance and resource availability each affect a set of mutually independent traits was not consistent with the data. Instead, our final model shows that most traits are strongly affected by both drivers. In addition, trait-trait constraints are more important in community assembly than environmental drivers in half of the cases. Both aspects of trait selection are crucial for correctly predicting ecosystem processes and community assembly, and they provide new insights into hitherto underappreciated ecological interactions. © 2012 by the Ecological Society of America

Bioinformatic and biometric methods in plant morphology

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141215/1/aps31400071.pd

Allometric Trajectories and \u201cStress\u201d: A Quantitative Approach

The term \u201cstress\u201d is an important but vague term in plant biology. We show situations in which thinking in terms of \u201cstress\u201d is profitably replaced by quantifying distance from functionally optimal scaling relationships between plant parts. These relationships include, for example, the often-cited one between leaf area and sapwood area, which presumably reflects mutual dependence between source and sink tissues and which scales positively within individuals and across species. These relationships seem to be so basic to plant functioning that they are favored by selection across nearly all plant lineages. Within a species or population, individuals that are far from the common scaling patterns are thus expected to perform negatively. For instance, \u201ctoo little\u201d leaf area (e.g. due to herbivory or disease) per unit of active stem mass would be expected to incur to low carbon income per respiratory cost and thus lead to lower growth. We present a framework that allows quantitative study of phenomena traditionally assigned to \u201cstress,\u201d without need for recourse to this term. Our approach contrasts with traditional approaches for studying \u201cstress,\u201d e.g. revealing that small \u201cstressed\u201d plants likely are in fact well suited to local conditions. We thus offer a quantitative perspective to the study of phenomena often referred to under such terms as \u201cstress,\u201d plasticity, adaptation, and acclimation

An allometry-based approach for understanding forest structure, predicting tree-size distribution and assessing the degree of disturbance

Tree-size distribution is one of the most investigated subjects in plant population biology. The forestry literature reports that tree-size distribution trajectories vary across different stands and/or species, while the metabolic scaling theory suggests that the tree number scales universally as -2 power of diameter. Here, we propose a simple functional scaling model in which these two opposing results are reconciled. Basic principles related to crown shape, energy optimization and the finite size scaling approach were used to define a set of relationships based on a single parameter, which allows us to predict the slope of the tree-size distributions in a steady state condition. We tested the model predictions on four temperate mountain forests. Plots (4 ha each, fully mapped) were selected with different degrees of human disturbance (semi-natural stands vs. formerly managed). Results showed that the size distribution range successfully fitted by the model is related to the degree of forest disturbance: in semi-natural forests the range is wide, while in formerly managed forests, the agreement with the model is confined to a very restricted range. We argue that simple allometric relationships, at individual level, shape the structure of the whole forest community.Comment: 22 pages, 4 figure

A Structurally Based Analytic Model of Growth and Biomass Dynamics in Single Species Stands of Conifers

A theoretically based analytic model of plant growth in single species conifer communities based on the species fully occupying a site and fully using the site resources is introduced. Model derivations result in a single equation simultaneously describes changes over both, different site conditions (or resources available), and over time for each variable for each species. Leaf area or biomass, or a related plant community measurement, such as site class, can be used as an indicator of available site resources. Relationships over time (years) are determined by the interaction between a stable foliage biomass in balance with site resources, and by the increase in the total heterotrophic biomass of the stand with increasing tree size. This structurally based, analytic model describes the relationships between plant growth and each species’ functional depth for foliage, its mature crown size, and stand dynamics, including the self‐thinning. Stand table data for seven conifer species are used for verification of the model. Results closely duplicate those data for each variable and species. Assumptions used provide a basis for interpreting variations within and between the species. Better understanding of the relationships between the MacArthur consumer resource model, the Chapman–Richards growth functions, the metabolic theory of ecology, and stand development resulted