Do Phytophenological Series Contribute to Vegetation Monitoring?

Abstract

Phenological observations have been made in Switzerland since 1951. In addition to these observation programmes, there are two very long phenological series in Switzerland. The foliation of horse chestnut trees in Geneva has been observed since 1808, the full flowering of cherry trees in Liestal since 1894. Apart from the presentation of these series, trends for the regions Ticino and Engadine are calculated with national data from 1951 to 1998. The earlier foliation of the horse chestnut trees in Geneva can mainly be put down to the city effect (Warmth Island). This phenomenon was not observed with the cherry tree flowering in Liestal. A tendency towards earlier appearance dates in spring and later appearance dates in autumn could be made out with the data from the national observation network. It must be noted that the different phenophases and plant species react differently to various environmental influences. A general development of the vegetation — computed from data from various observation posts and phenophases for the different phenological seasons — is not suited for the investigation of phenological trends. This essay has shown that it is worthwhile to analyse more data from other regions in Switzerland.