IMPACT OF CARPETS OF THE INVASIVE MOSS CAMPYLOPUS-INTROFLEXUS ON CALLUNA-VULGARIS REGENERATION

1. The moss Campylopus introflexus is a Southern Hemisphere species in the process of expanding its distributional range. It was first found in Europe in 1941. 2. Some of the potential impacts of the invasion of C. introflexus into moorland habitats are investigated. In particular, the effects that the moss carpets may have on germination and subsequent growth of Calluna vulgaris are assessed. 3. A glasshouse experiment contrasted both the amount of germination of Calluna seeds and the performance of the seedlings on moss carpets and on bare ground. The effect of moisture availability was analysed, comparing normal daily watering with continuous water supply at the base of the pots. A significant depressive effect (60% reduction) of the moss carpet on the amount of germination was observed, irrespective of the form of water supply. However, seedlings grew higher and produced more flowers when growing on moss carpets. 4. Two experiments tested for the possibility of an allelopathic interaction. In one experiment seeds of Calluna were treated with a solution obtained from soaking moss fragments in deionized water. In the other the seeds were placed together with moss shoots. Neither experiment indicated allelopathic effects. 5. The results of glasshouse experiments suggested that there was no definite evidence that C. introflexus can suppress Calluna re-establishment following fire. However, under field conditions, the germination rate of heather on moss carpets can be expected to be much lower and its growth rate will be reduced by grazing. These conditions will make it more difficult for the heather to compensate for the loss in recruitment. 6. It is hypothesized that the dynamics of the moss carpet itself may play an important part in the competitive success of C. introflexus.