Das Projekt "Tree growth rings as early indicators of volcanic activity on Mt. Etna" wird/wurde gefördert durch: Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung. Es wird/wurde ausgeführt durch: Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft.Volcanoes threaten the lives of millions of people. Early indicators of volcanic explosions could help in risk management, but eruptions remain largely unpredictable. New indicators of eruptions are urgently needed. Moreover, it would be of great interest to reconstruct past volcanic activity at many volcanoes. Recently, remote sensing techniques have revealed increased photosynthetic rates in trees growing along future eruptive fractures on Mt. Etna, Italy, and on Mt. Nyiragongo, Congo; flank eruptions occurred 3-4 years later along these same fractures. The mechanisms linking photosynthetic activity to future eruptions are currently unclear; one hypothesis is that movement of magma in the deep conduits of the volcanic system leads to degassing of substances that promote plant growth. Preliminary tree ring data from Mt. Etna suggest that trees are influenced by volcanic activity before the magma erupts, and therefore might be used 1) as early indicators of eruptions, and 2) to reconstruct past volcanic eruptions. Our main research questions are therefore: - Can trees be used as indicators of past and future eruptions? - Which natural factors control tree-ring growth to which extent on a volcanic area? - How did these factors vary over the last 100 to 150 years and how did they influence tree ring growth? Preliminary results from a pilot study on Mt. Etna (Sicily, Italy) show that trees (but not all trees and not at all locations) are growing faster several years before eruptions. The pilot study created preliminary data on tree-ring growth as well as ?13C, ?18O and 14C in tree rings, and first attempts could be made to correlate these parameters to time series of volcanic eruptions and climate data from three nearby weather stations. The planned experimental design foresees 6-12 elevation transects (within the black pine, Pinus nigra, vegetation belt) in the vicinity of recent eruptions. In addition, nearby area without any (direct) volcanic activities (Monti Nebrodi) will serve as a control site. We aim at investigating the several factors that may contribute to increased growth rates: a) availability of water, b) nutrients and trace elements in the wood and in the soil, c) degassing of carbon dioxide (CO2) or ammonia (NH4), and d) climate (temperature and precipitation). (...)