The Editor’s Choice paper for Issue 104:5 is titled ‘On the link between functional traits and growth rate: meta-analysis shows effects change with plant size, as predicted’ and was written by a team from the Department of Biological Sciences of Macquarie University, Sydney, Australia. Many thanks to authors Anaïs Gibert, Daniel Falster and Mark Westoby for providing some background on their study below.

The focus of our paper is on the differences across plant species in potential growth rates. It sets up working hypotheses for how traits should be expected to influence growth based on a plant growth model, and then compares these against evidence in the literature. For some traits, correlations with growth are expected to change in a predictable way with plant size. Literature evidence currently available is consistent with these expectations. (At the same time, available literature on growth rate comparisons among species is quite unbalanced and incomplete in its coverage across different traits and plant sizes.)

The paper arose from an anomaly in the literature, whereby SLA (leaf area per dry mass) has often been interpreted as an indicator of fast-growth species, but correlation with actual observed growth rates has often been weak or non existent, especially in forest plots. Theory developed by co-author Falster predicted that SLA would be correlated with rapid growth among seedlings but that this correlation would disappear as plants grew larger. Accordingly it seemed worthwhile to gather the literature evidence more systematically. The upshot means that species traits (some of them anyhow) should be thought of as influencing growth trajectories with plant size, not simply faster versus slower growth rates.

See below for some images related to the study taken by the authors.

Data used in this meta-analysis came from different ecosystems around the world, such as heathland, tropical woodland and rainforest (from left to right)

The relationship between SLA (specific leaf area, a measure of how cheaply leaf area is constructed) and growth rate shifts from positive in seedlings to non-significant or negative in adult plants.

The relationship between wood density or stem density and growth rate is expected to be negative across all plant sizes.