3a), probably because of the heat radiating from the lava. Etna have also been found to lack tree rings close to lava flows.
In contrast, trees in MFs located close to a lava flow but far away from the crater formed regular rings during 19 and seemingly were not affected by the heat emitted by the lava flow (Fig. Before comparing the tree-ring width of 1973 with the ring width of previous years, we need to correct for the age-related growth trend in trees.
We expected MFn trees to be more disturbed than the MFs trees as they were closer to the 1974 vents.
Only then will it be possible to discuss whether the observed reduction of photosynthesis was already sustained before September 1973.
Ring-width chronologies for trees in MFn (a), MFs (b), both parts of Monte de Fiore (c) and the control site (d).
Such an impact is not visible in the tree-ring width time-series of MFs trees. 4 the detrended ring-width data for trees in MFn (a), MFs (b), both parts of Monte de Fiore (c) and the control site (d) are shown.
A zoom image for the eruptive period of this figure is available in the Supplementary Materials (Supplementary Fig. After detrending the low-frequency variability of the raw time series is eliminated but high-frequency variability, such as the reduced growth of MFn trees during 1974–1975, is preserved. 3 after applying detrending to samples from MFn (a), MFs (b), all of Monte de Fiore (c) and the control site (d).
Until now, it has been unclear when this signal started, whether it was sustained and which process(es) could have caused it.
By analyzing tree-ring width time-series, we show that the reduced near-infrared precursory signal cannot be linked to a reduction in annual tree growth in the area.
Vetore station (20 events per day at the Catania station; Fig. For reference, during the 1971 crisis, the daily seismic rate did not exceed 10 events per day at the Catania station and afterwards is often associated with magma intrusions. The temporal coincidence of the October 1973 seismic crisis with both renewed activity at the Voragine and the NIR signal, raises the question of the presence of an early intrusion into the western flank in the vicinity of Monte de Fiore.
Seismic activity as detected by seismic sensors deployed on the flanks of Mt.
Recently, it has been shown that pre-eruptive volcanic activity occurring during the vegetation period can influence the photosynthesis of trees, as shown by Normalized Difference in Vegetation Index (NDVI) derived from satellite imagery months before the beginning of the 2002–2003 eruption of Mt. Before the time of modern remote sensing sensors, a reduced near-infrared (NIR) signal was detected in September 1973 in the area of Monte de Fiore (Fig. In order to test whether trees were impacted by volcanic activity and with the aim of better understanding the dynamics of the early stages of the 1974 eruptive event, we built ring-width time-series of trees located near Monte de Fiore.