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Partitioning the components of Relative Growth Rate: how important is plant size variation?


Rees, M; Osborne, C P; Woodward, F I; Hulme, S P; Turnbull, L A; Taylor, S H (2010). Partitioning the components of Relative Growth Rate: how important is plant size variation? American Naturalist, 176(6):E152-E161.

Abstract

Plant growth plays a key role in the functioning of the
terrestrial biosphere, and there have been substantial efforts to understand why growth varies among species. To this end, a large number of experimental analyses have been undertaken; however, the emergent patterns between growth rate and its components are often contradictory. We believe that these conflicting results are a consequence of the way growth is measured. Growth is typically characterized by relative growth rate (RGR); however, RGR often declines as organisms get larger, making it difficult to compare species of different sizes. To overcome this problem, we advocate using nonlinear mixed-effects models so that RGR can be calculated at a standard size, and we present easily implemented methods for doing this. We then present new methods for analyzing the traditional components of RGR that explicitly allow for the fact that log (RGR) is the sum of its components. These methods provide an exact decomposition of the variance in log (RGR). Finally, we use simple analytical and simulation approaches to explore the effect of size variation on growth and its components and show that the relative importance of the components of RGR is influenced by the extent to which analyses standardize for plant size.

Abstract

Plant growth plays a key role in the functioning of the
terrestrial biosphere, and there have been substantial efforts to understand why growth varies among species. To this end, a large number of experimental analyses have been undertaken; however, the emergent patterns between growth rate and its components are often contradictory. We believe that these conflicting results are a consequence of the way growth is measured. Growth is typically characterized by relative growth rate (RGR); however, RGR often declines as organisms get larger, making it difficult to compare species of different sizes. To overcome this problem, we advocate using nonlinear mixed-effects models so that RGR can be calculated at a standard size, and we present easily implemented methods for doing this. We then present new methods for analyzing the traditional components of RGR that explicitly allow for the fact that log (RGR) is the sum of its components. These methods provide an exact decomposition of the variance in log (RGR). Finally, we use simple analytical and simulation approaches to explore the effect of size variation on growth and its components and show that the relative importance of the components of RGR is influenced by the extent to which analyses standardize for plant size.

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33 citations in Web of Science®
33 citations in Scopus®
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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:15 October 2010
Deposited On:24 Nov 2010 15:16
Last Modified:07 Dec 2017 04:22
Publisher:University of Chicago Press
ISSN:0003-0147
Publisher DOI:https://doi.org/10.1086/657037

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