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The reliability of lichenometric dating is dependent on a good understanding of lichen growth rates. The growth rate of lichens can be determined from direct measurement of growing lichens or indirect methods by measuring lichens growing on surfaces of known age, although there are limitations to both approaches. Radiocarbon (14C) analysis has previously been used in only a handful of studies to determine lichen growth rates of two species from a small area of North America. These studies have produced mixed results; a small amount of carbon turnover appears to occur in one of the species (Caloplaca spp.) previously investigated introducing uncertainty in the growth rate, while much higher carbon cycling occurred...
Contents Summary1I.Introduction2II.Variation in plant C : N : P ratios: how much and what are the sources?3III.The growth rate hypothesis in terrestrial plants and the scaling of whole-plant N : P stoichiometry and production5IV.Scaling from tissues to whole plants7V.Applications: large-scale patterns and processes associated with plant stoichiometry9VI.Global change and plants: a stoichiometric scaling perspective11VII.Synthesis and summary12Acknowledgements13References13 Summary Biological stoichiometry theory considers the balance of multiple chemical elements in living systems, whereas metabolic scaling theory considers how size affects metabolic properties from cells to ecosystems. We review recent developments...
Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18?24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length-(LT) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post-maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation....