Changes over three decades in the floristic composition of fertile permanent grasslands in the Swiss Alps

Abstract

This study investigates how the floristic composition and species richness of fertile grasslands in the Swiss Alps has changed over the last three decades. A total of 259 phytosociological relevés in four regions were resurveyed after periods of between 17 and 29 years. Analysis of the data revealed that floristic composition of the grasslands changed significantly during the study period, although the factor ‘time’ explained only a small proportion of the total variation (2.0–4.1%). The shifts in floristic composition were interpreted as indicators of changing management intensity due to continuing changes in agricultural structures. In three of the study regions there was an increase in species that are competitive under nutrient-rich conditions, possess high roughage quality and are tolerant of frequent mowing, indicating that the intensity of management had increased. Despite this apparent intensification, however, the initially high mean values per plot for species number (30.7–36.3) and evenness (0.72–0.77) mainly increased during the interval between the surveys. In the study region with the highest intensity of management, the abundance of weed species increased on some sites and the indicator value for roughage quality decreased, suggesting that intensification had been excessive and had destabilised these plant communities. Floristic shifts in the fourth study region, where the number of farms had declined considerably, mainly indicated extensification, especially on more marginal sites. The nature conservation value of the plant communities (i.e. number per plot of species indicating ecological quality) decreased in the three study regions where the floristic changes indicated that management had been intensified (−0.4 to −0.7 species) but increased in the fourth region (+1.1 species). It is concluded that the intensification of management in the fertile grasslands of the Alpine regions studied has been less extreme than in many European lowland areas, and that the developments have in most cases been sustainable. However, the evidence of some destabilised plant communities suggests that management intensity is now too high on these sites.