Evidence of a causal connection between anti-herbivore defence and the decomposition rate of leaves

An experiment was conducted to lest the hypothesis that interspecific variation in rates of leaf litter decomposition arises as a consequence of differences in the anti-herbivore defences of the living leaf. Leaf palatability was assayed in 54 vascular plant species of widespread occurrence in the British Isles, using the generalist herbivore Helix aspersa (garden snail) and the omnivore Acheta domestica (a cricket). The results were then compared with published standardised measurements of litter decomposition rate available for 43 of the species. There was convincing support for the hypothesis, in the form of a significant positive correlation between leaf palatability and lifter decomposition rate. The correlation was also evident within subsets consisting of monocots or dicots. The results suggest a critical role for anti-herbivore defences in the link between aboveground and belowground processes in ecosystems.