Reliability and effectiveness of Ellenberg’s indices in checking flora and vegetation changes induced by climatic variations

Abstract

Two methods are proposed to assess the significance of time-spanned local variations of Ellenberg’s indicator values in floristic and phytosociological data sets respectively. Both methods are based on frequencies and averages of the indicator values within and among data sets. Main goal of proposed methods is to determine the thresholds to consider significant the observed variations. In the aim to relate the observed floristic variations to recent climatic changes, attention was focused on the Ellenberg’s indices dealing with the main climatic variables: heliophany, temperature and precipitation. Study-cases from Zannone island (Pontine archipelago, Mediterranean region), Inferno valley (Rome, Mediterranean region) and Braulio valley (Stelvio National Park, Alpine region) are reported. For Mediterranean data-sets, integration and adjustments to the Ellenberg’s indicator values have been adopted.