Dendrogeomorfologia applicata allo studio delle colate laviche del 1928, 1971 e 1979 sul M. Etna

Dendrogeomorphology applied to the study of 1928, 1971 and 1979 14 lava flows on Mount Etna

Abstract

The present work investigates the effects of successive basaltic lava flows on the vegetation, and in particular on the annual growth rate. It is evaluated the time necessary for a complete recovery to normal growth rate after each repeated emergence and lava flow and the relationships between distance from the flow and vegetation response. Furthermore, we evaluated dendrochronology as a reliable tool for lava flow dating. Several tens of samples were collected from Pinus laricio and Betula aetnensis located at the margins of 1928, 1971 and 1979 lava flows on the slopes of M. Etna. Trees located between 0 and 5 m from the margin of the 1971 lava flow are damaged by direct contact with the incandescent lavas and associated fires: large parts of both trunk and branches are burnt and the sequence of growth rings shows a marked scar for the year 1971. Even in cases when damage was restricted to the bark only, there are evidences of lowered growth rates soon aflter the eruption. Trees located beyond 5 m from the lava flow lack scars and the percentage of burnt trunks and branches progressively decreases. Slower growth rates are recorded by trees set at 100 to 500 m from the lava flow, although lacking marked evidences of damage. Trees located on the North side of the lava flow are more damaged than those set along the South side. Scarred trees recovered their regular growth rate 7 years after the eruption. Undamaged trees located near the flow recovered after 3 years, whereas more distant trees recovered the normal growth rate after 1 year. Similar results have been obtained also for the 1928 and 1979 events.