On Decaying Roots, Mycorrhizal Colonization and the Design of Removal Experiments

Abstract

1 Removal experiments are widely used to study competition in natural ecosystems but suffer from a number of methodological drawbacks. We describe two glasshouse bioassays using field soil which were designed to test for effects of removal experiment methodology on plant growth. 2 Soil was sieved to remove plant roots which were then added back to some samples. The presence of decaying roots in the soil did not significantly alter the performance of Holcus lanatus plants over the time scale of the experiment (three months). 3 Over the same period of time, however, sieving the soil significantly reduced the mycorrhizal infection of Holcus lanatus roots and subsequent shoot growth. In the same experiment, a nonmycorrhizal species (Cerastium fontanum) was unaffected by soil disturbance. 4 These findings suggest that the disturbance resulting from total plant removal will have adverse effects on the performance of plants remaining in the sward. Since the presence of roots seems to have little effect, above-ground clipping and leaving roots to decay in the soil is likely to be a better approach to removal experiments.