Does site elevation determine the start and intensity of human impact? Pollen evidence from southern Germany

We investigated lake sediments from Groser Ursee, Landkreis Ravensburg, Allgau, Baden-Wurttemberg, to explore whether human activity was delayed and less intense at higher sites compared to those in the adjacent lower area around Bodensee (Lake Constance). A 11.1 m high resolution pollen profile from the centre of the lake was analysed, which covers the late Wurm and complete Holocene sequence, providing a continuous pollen record of 1,092 samples. Human and climate induced vegetation and landscape change is discussed. The history of human impact indicated in this profile at around 700 m in the western Allgau, with a precipitation above 1,000 mm/year and with a less favourable climate is compared with human impact in adjacent lower landscapes, with a more favourable climate for agriculture such as the Bodensee region. Since the Neolithic period, differences in vegetation development between the regions were mainly caused by a varying intensity of human impact which itself was strongly influenced by climatic differences. In the lowlands with a warm and dry climate, human impact started earlier and was stronger than in less favourable areas. Finally, the regular occurrence of Trapa natans at Groser Ursee, much more frequent there than in the adjacent warmer landscape to the west, is discussed in terms of various ecological factors.