Changes in the species composition and conservation value of limestone grasslands in Northern Switzerland after 22 years of contrasting managements

• Published in: Perspectives in plant ecology, evolution and systematics evolution and systematics, 2005-01, Vol.7 (1), p.51-67
• Main Authors: Köhler, Barbara, Gigon, Andreas, Edwards, Peter J., Krüsi, Bertil, Langenauer, Regula, Lüscher, André, Ryser, Peter
• Format: Article
• Language: English
• Subjects: Biodiversity; Brachypodium pinnatum; Bromus erectus; Calcareous grassland; Long-term experiment; Mesobrometum; Nature conservation; Salvia pratensis; Vegetation changes
• ISSN: 1433-8319; 1618-0437
• DOI: 10.1016/j.ppees.2004.11.003

An experiment was established to assess the long-term effects of six different management types on the species composition of dry limestone grasslands with the aim of finding an alternative to the traditional management (mowing annually in July) which is no longer economically viable. In addition to the traditional management (JU1), the following management types were applied experimentally for 22 years: mowing every 2 years in July (JU2), every 5 years (JU5), or not at all (ABN, abandonment), mowing annually in October (OCT), and controlled burning annually (CBR) at the end of winter. There were two study sites, Gräte and Grätental, near Schaffhausen in N Switzerland, each with three replicate 5 m×10 m plots for every management. During the course of the experiment, the vegetation was recorded on 10 occasions, yielding 306 vegetation relevés containing a total of 124 species. These data were analysed using correspondence analyses (CA). In addition, changes in the abundance of 16 plant species with high cover, high frequency or particular importance for nature conservation were examined in detail. The CA showed that the vegetation of the two study sites differed considerably, but that in both sites the various management types led to changes in floristic composition which were probably continuing even after 22 years. At the end of the experiment, on the Gräte site, species number in comparison to JU1 had declined in the following progressive order: OCT, JU2, JU5, CBR, ABN, where it was down to 70%. At the Grätental site, species number showed no clear pattern, because of the immigration of ‘new’ species from the surrounding hedges and agricultural fields. Interestingly, Bromus erectus, the dominant species with a cover of 40–70% at the beginning, decreased to 5–30% under different managements, mainly because the regeneration of its tufts is affected by abandonment and particularly burning. The rhizomatous Brachypodium pinnatum showed the opposite pattern and increased from 5% to 60% in CBR. Trifolium medium as well as Salvia pratensis, Primula veris and other long-lived forbs of high conservation value tended to be favoured by OCT, CBR and/or ABN because they can store nutrients if they are not annually cut in July. On the other hand, several low growing species like Anthyllis vulneraria and Hieracium pilosella need the better light conditions associated with the annual mowing in July for optimal growth. In every management type, some species of high conse