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Full-Text Articles in Life Sciences
The Scaling Of Reproductive Variability In Trees, Andrew Kerkhoff
The Scaling Of Reproductive Variability In Trees, Andrew Kerkhoff
Andrew J Kerkhoff
Seed output in perennial plant populations is temporally variable and often synchronous over large regions. The similarly complex spatiotemporal dynamics of animal populations have been characterized by the power-law scaling of the variance in population numbers with mean abundance. Here we show that a large compilation of published reproductive time series exhibits largely invariant mean–variance scaling properties across both angiosperm and conifer tree species. A simple model of seed production in tree stands shows that observed values of the scaling exponent reflect very general aspects of plant ecology and life history as well as the temporal dynamics of seed production. …
Allometric Growth, Life-History Invariants And Population Energetics, Andrew Kerkhoff
Allometric Growth, Life-History Invariants And Population Energetics, Andrew Kerkhoff
Andrew J Kerkhoff
Population and community level processes must be at least partially determined by variation in the body sizes of constituent individuals, implying quantitative scaling relations can be extended to account for variation in those processes. Here we integrate allometric growth and life-history invariant theories, and use this approach to develop theory describing the energetics of stationary populations. Our predictions approximate, with no free parameters, the scaling of production/biomass and assimilation/biomass ratios in mammalian populations and work partially for fish populations. This approach appears to be a promising direction and suggests the need for further development of the growth and life-history models, …
The Implications Of Scaling Approaches For Understanding Resilience And Reorganization In Ecosystems, Andrew Kerkhoff
The Implications Of Scaling Approaches For Understanding Resilience And Reorganization In Ecosystems, Andrew Kerkhoff
Andrew J Kerkhoff
Managing ecosystems for resilience—the capacity to maintain function in response to perturbation—is among the most pressing ecological and socioeconomic imperatives of our time. The variability of biological and ecological systems at multiple scales in time and space makes this task even more challenging, yet diverse ecological systems often display striking regularities. These regularities often take the form of scaling laws, which describe how the structure and function of the system change systematically with scale. In this article, we review recent work on the scaling of human settlement sizes and fertility as well as the size distributions of forests. We demonstrate …
Ontogenetic Scaling Of Metabolism, Growth, And Assimilation: Testing Metabolic Scaling Theory With Manduca Sexta Larvae., Andrew Kerkhoff, Harry Itagaki
Ontogenetic Scaling Of Metabolism, Growth, And Assimilation: Testing Metabolic Scaling Theory With Manduca Sexta Larvae., Andrew Kerkhoff, Harry Itagaki
Andrew J Kerkhoff
Metabolism, growth, and the assimilation of energy and materials are essential processes that are intricately related and depend heavily on animal size. However, models that relate the ontogenetic scaling of energy assimilation and metabolism to growth rely on assumptions that have yet to be rigorously tested. Based on detailed daily measurements of metabolism, growth, and assimilation in tobacco hornworms, Manduca sexta, we provide a first experimental test of the core assumptions of a metabolic scaling model of ontogenetic growth. Metabolic scaling parameters changed over development, in violation of the model assumptions. At the same time, the scaling of growth rate …
Multiplicative By Nature: Why Logarithmic Transformation Is Necessary In Allometry, Andrew Kerkhoff
Multiplicative By Nature: Why Logarithmic Transformation Is Necessary In Allometry, Andrew Kerkhoff
Andrew J Kerkhoff
No abstract provided.
Expectation, Explanation And Masting, Andrew Kerkhoff
Expectation, Explanation And Masting, Andrew Kerkhoff
Andrew J Kerkhoff
Masting is the synchronous, episodic production of large seed crops by perennial plant populations. Generally, hypotheses concerning the evolutionary origin and maintenance of masting entail economies of scale, where the benefit of large, synchronous reproductive events accrues by overcoming some environmental constraint, such as pollen limitation or seed predation. Because all perennial plants face some degree of inter-annual environmental variability, assessing the importance of selection via economies of scale requires a clear expectation for the reproductive dynamics of plants adapted to variable environments. Using a dynamic life-history model, I demonstrate that the observed range of reproductive variability and several other …
Testing The Metabolic Theory Of Ecology., Andrew Kerkhoff
Testing The Metabolic Theory Of Ecology., Andrew Kerkhoff
Andrew J Kerkhoff
The metabolic theory of ecology (MTE) predicts the effects of body size and temperature on metabolism through considerations of vascular distribution networks and biochemical kinetics. MTE has also been extended to characterise processes from cellular to global levels. MTE has generated both enthusiasm and controversy across a broad range of research areas. However, most efforts that claim to validate or invalidate MTE have focused on testing predictions. We argue that critical evaluation of MTE also requires strong tests of both its theoretical foundations and simplifying assumptions. To this end, we synthesise available information and find that MTE's original derivations require …