Introduction

Abstract

Amphibious lichens are widely distributed but little recognized components of freshwater vegetation. In most assessments of freshwater organisms however, lichens are still neglected which is partly due to the fact that corresponding literature is widely scattered and a profound treatment of these lichens in Central Europe is still missing. This book is intended to provide a comprehensive tool for the determination of freshwater lichens in Central Europe for both, the non-specialized limnologist and the interested lichenologist. It further summarizes basic information on ecology and distribution. The book roughly covers an area ranging from the Alps to the south shores of the North and Baltic Sea and from the Western Carpathians in the east to the Vosgues-Mountains in the west. Amphibious lichens are found in springs, streams and rivers wherever hard and stable substrata as well as sufficient light are granted. In certain streams of cooler upland areas, lichens can represent the most diverse group of organisms covering virtually any rock surface (e.g. Frey 1922). On the other hand, they are very rarely found in lakes. Rock surfaces incrusted by silt, surface erosion by sediment particles or water with a pH below 5 can exclude any growth of lichens. Resulting from that, freshwater lichens are valuable long-term indicators of the specific structure of a given watercourse, as well as they indicate key factors of water chemistry (Nascimbene et al. 2007). Water pollution was — and certainly still is — the main reason for the dramatic decline of lichen growth especially along larger watercourses during the past decades.