IS THE RELIC FLORA OF THE FALLATSCHE ENDA NGERED - CHANGES IN THE FLORA AND VEGETATION OF AN EROSION SLOPE NEAR ZURICH

The Fallatsche is an impressive erosion slope in the shape of a semici rcular funnel in the vicinity of Ziirich. Its vegetation is characteri zed by a succession series which starts on slopes of bare marl or calc areous sandstone. These patches offer suitable habitats for early-succ essional species and pioneers. The final serial stage is a sparse pine forest. Intermittent erosion can interrupt the successional series at any stage. In the resulting mosaic of various habitats we registrated 309 taxa of vascular plants and 48 taxa of bryophytes. They mainly be long to species which are characteristic for pine forests (Molinio-Pin etum), nutrient-poor meadows (Mesobrometum), and nutrient-poor fens do minated by small sedges (Caricion davallianae), as well as to a group of subalpine species. Many of them are mentioned in the Red List of va scular plants of Switzerland. The comparison of the recent flora of th e Fallatsche with its former flora (before 1970) by means of informati on taken from literature revealed that only two plant species have dis appeared from this location, but that the numbers of weeds, of ruderal s, and of species indicating nutrient-rich conditions have increased. This fact parallels a decrease in open habitat patches and an increase of denser vegetation. Both phenomena are caused by the stabilizing ef fects of protective measures like river breaks and possibly by aerial nitrogen deposition. Despite its small area but due to its natural lan dscape dynamics, the Fallatsche is a regional hot-spot for the conserv ation of atonal vegetation in the northeastern Swiss Plateau.