The impact of trampling by tourists on a high altitudinal grassland in the Tyrolean Alps,Austria

The long term effect of tourist trampling on a high altitudinal grassland (Caricion curvulae) in the Tyrolean Alps was investigated.Even under slight trampling the frequency of sensitive species decreases. The most sensitive species were found to be fruticose lichens, followed by mosses, some forbs and broadleaved grasses. Tolerant to trampling are the dominant species Carex curvula, and Ligusticum mutellina, which do not disappear completely even at a tourist frequency of 150 tourists per metre per day. Trampling increases soil bulk density moderately but has no marked effect on the soil water content.Comparison with high alpine sedge heath vegetation in North America shows a surprising uniformity of this vegetation type in response to trampling and also indicates that the common generalisation that alpine ecosystems are fragile and sensitive to disturbance does not hold true in this context. Furthermore these results represent evidence against the theory that ecosystems with low diversity are much more sensitive to arteficial impact than ecosystems with high diversity. However, if even the most resistant plants which are the dominant sedges are destroyed completely the rate of recovery is very low and may last for a long time. In the case of Carex curvula this is supported by the fact that it has very low seed production and grows mainly vegetatively. The rate of spread of the rhizome system of this species is 8 mm in 10 years. Similar figures may apply for the sedge species dominating in the alpine vegetation of North America. Thus fragility of this vegetation in regard to trampling does not mean low tolerance but low regeneration.Nomenclature of species follows Ehrendorfer (1973) for vascular plants and Poelt (1974) for lichens.The PCA calculations were done at the Computer laboratory of the University of Wales during a post doctoral stay at the School of Plant Biology in Bangor, U.K. I would like to record my thanks to Prof. Dr. P. Greig-Smith for fruitful discussions and reading the draft.