Langzeit-Feuerökologie der Schweiz | Long-term fire ecology of Switzerland

Understanding past natural and anthropogenically induced forest fires and their long-term impact on the environment is a prerequisite for modern fire management. Thanks to modern paleoecological approaches it was possible to reconstruct the long-term role of fire for ecosystems, landscape properties and functions in various parts of Switzerland. In order to test and calibrate the paleoecological approach on a local scale, we compared the forest-fire statistics of the last 70 years around the small Lago di Origlio (southern Switzerland) with the yearly charcoal influx in the lake sediments. We demonstrated that the yearly deposition of microscopic charcoal particles (0.01−0.2 mm) correlates well with the regional forest-fire frequency 20 to 50 km around the lake, whereas macroscopic charcoal particles (> 0.2 mm) matched local fire events within a 2 km distance. Furthermore, the pilot study of lake Origlio provided insights into the different origins of forest fires and their long-term impact on vegetation. Studies in other areas in Switzerland suggest that that the long-term effects of forest fire are not limited to the southern slope of the Alps, but also concern the forests of the Swiss Plateau and the Alps. There, the diffusion of fire-sensitive tree species such as Ulmus spp., Tilia spp., Fraxinus spp., Acer spp. at the colline to mountain level, as well as Abies alba and Pinus cembra at the subalpine level was significantly reduced compared to the natural environmental conditions prior to the beginning of widespread slash and burn practices. The abundance reduction of tree species during the past millennia occurred in the southern and the northern Alps, on the Swiss Plateau, but not in the fire-prone dry valleys of the central Alps, where forest fires were more frequent naturally and exerted relevant ecosystem functions. Our results show that without considering sedimentary paleoenviromental information it is hardly possible to gain correct assessments of current and future fire, environmental and forest dynamics. The implementation of paleoecological results into practical management activities is thus indispensable, especially in the view of the expected climatic changes.