Plant functional group identity differentially affects leaf and root decomposition


Jennie McLaren, tel. +1 604 822 2141, fax +1 604 822 6089, e-mail:


Losses of species and changes in the composition of plant communities are likely to influence numerous ecosystem functions. Changes in the plant-soil interactions that control decomposition, in particular, could alter carbon and nutrient cycling in soils and further alter other ecosystem functions. The effects of plant communities on decomposition may depend both on the type of tissue being decomposed and also on the different stages of the decomposition process. We used an experimental design where single plant functional groups were removed from a northern grassland to examine the role of plant identity in determining both short-term and long-term above- and belowground decomposition rates. Plant removals were conducted across fertilization and fungicide treatments to examine environmental context-dependency of functional group identity effects on decomposition. There were significant effects of plant functional group identity on aboveground decomposition, with the loss of grasses and forbs slowing decomposition, whereas the effects on belowground decomposition were rare and transient. Effects of plant identity on decomposition were consistent in both short- and long-term decomposition studies indicating that the influences of identity on the decomposition environment remained consistent throughout the different stages of the decomposition process. Both fertilizer and fungicide treatments affected overall decomposition rate, but there were few interactions between these treatments and plant removals. Although current species loss is likely to be happening in concert with environmental changes, the role a species plays in determining ecosystem functions such as decomposition may not be context-dependent in these northern environments, and this may provide greater predictive power in determining the effects of species loss with changing environments. Further, as plant identity shows significant effects on litter decomposition rates, the effects of current and predicted future biodiversity losses may depend specifically on which species are lost.