Holocene vegetation change at Grosssee, eastern Swiss Alps: effects of climate and human impact

Abstract Pollen, spores, and microscopic charcoal from the sediments of Grosssee (1,619 m a.s.l.), a small lake in the lower subalpine vegetation zone of the Glarus Alps, Switzerland, were analysed to reconstruct vegetation patterns and land use over the past ca. 12,300 calibrated 14 C years bp (cal bp ). Pollen data revealed an open landscape covered with grasses and herbs such as Artemisia during the Late Glacial Period. The catchment was likely initially afforested with Betula and Pinus cembra or Pinus sylvestris during the Early Holocene. Thermophilous taxa such as Ulmus , Tilia , and Alnus glutinosa -type expanded from ca. 11,000–9,200 cal bp , and mesophyllic Picea abies and Fagus sylvatica followed, and expanded beginning from ca. 8,000–7,600 cal bp . Interestingly, Alnus viridis (synonym: A. alnobetula ) expanded about 2,000 years earlier than at comparable sites in the northern Swiss Alps. Its expansion was profound and persistent, and percentages > 15% were already achieved by ca. 7,000 cal bp . Local erosion events that followed are well explained by vegetation changes and inferred human land use activities at Grosssee. In particular, this led to a more open landscape, and land uses (e.g. grazing) intensified from the Mid- to Late Holocene. Indicators of environmental disturbance including persistently high levels of A. viridis , monolete fern spores, and microscopic charcoal were pronounced after ca. 4,000 cal bp . At that time, high influxes of spores from coprophilous fungi and the consistent presence of cultural indicators (Cerealia-type, Plantago lanceolata ) indicate increased grazing and high levels of human impact. Land use and grazing activities seemed to have been particularly pronounced and to have promoted diversity in the vegetation over the past 1,000 years.