title: Microbe-plant competition, allelopathy and arctic plants.
abstract: Michelsen et al. (1995) present results of an experiment in which aqueous leaf extracts of three arctic woody plant species were found to inhibit growth and nutrient acquisition of three graminoid species, and suggested that microbial nutrient immobilisation, rather than allelopathy, 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 the 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 not significantly different for the majority of cases. Finally we respond specifically to their criticisms of previous work on E. hermaphroditum. While the question of how arctic plants interact is an interesting one, we conclude that this question cannot be answered by their data.
authors.affiliation: AgResearch, Ruakura Agricultural Research Centre, East Street, Private Bag 3123, Hamilton, New Zealand fax: (64) (7) 838 5012; e-mail: wardled@agresearch.cri.nz, , , , , , NZ.
authors.forename: D A
authors.initials: DA
authors.lastname: Wardle
authors.affiliation: Department of Forest Vegetation Ecology, Swedish University of Agricultural Sciences, Faculty of Forestry, S-901 83 Umea, Sweden, , , , , , SE.
authors.forename: Marie-Charlotte
authors.initials: MC
authors.lastname: Nilsson
keywords: Arctic plants; Empetrum hermaphroditum; Key words Allelopathy; Microbial nutrient uptake; Nutrient acquisition