MICROBE-PLANT COMPETITION, ALLELOPATHY AND ARCTIC PLANTS

Michelsen et al. (1995) present results of an experiment in which aque ous leaf extracts of three arctic woody plant species were found to in hibit growth and nutrient acquisition of three graminoid species, and suggested that microbial nutrient immobilisation, rather than allelopa thy, was responsible for the observed trends. In doing this they also question previous work proposing that the Arctic dwarf shrub Empetrum hermaphroditum is allelopathic. We suggest that their conclusions are not unequivocally supported by their data. Firstly we indicate that th e approaches used for estimating microbial nutrient immobilisation are questionable. Secondly we indicate that most of the trends that they discussed are based on data in which the treatments and controls are n ot significantly different for the majority of cases. Finally we respo nd specifically to their criticisms of previous work on E. hermaphrodi tum. While the question of how arctic plants interact is an interestin g one, we conclude that this question cannot be answered by their data .