The mystery of the enhanced NDVI signal on Mt. Etna. Dendrochronological analysis of pine trees growing near the Dendrochronological analysis of pine trees growing near the 2002/2003 eruptive fissure.

This study investigates the potential for trees to perceive and react to volcanic activity prior to an eruption. Previous research found an unusual increase in the Normalized Difference Vegeta tion Index (NDVI) in the two years preceding the 2002/2003 eruption near Piano Provenzana on Mt. Etna. This finding suggests that trees were more photosynthetically active during this time. While prior studies were unable to ascertain the precise cause, one hypothesis suggests that extra soil moisture from condensed volcanic vapor may have contributed to the elevated NDVI signal. The sampling location of this thesis is located closer to the eruptive fissure, com pared to previously analyzed trees. In this thesis, tree-ring analysis revealed that some trees near the eruption site exhibited missing rings, suggesting potential disruptions to their growth patterns. Statistical analysis indicated that their growth patterns were not primarily influenced by precipitation or temperature, sug gesting the presence of other environmental factors. To further explore this phenomenon, a series of chemical analyses were conducted, including stable isotope analysis (of oxygen, hydrogen, and carbon), radiocarbon dating, and trace element measurements. The results suggest that stom atal activity may have undergone changes prior to the eruption, possibly due to the influence of deep-origin CO2 influencing the trees. Lower δ18O values suggest that the trees accessed a different water source during and after the eruption. Stem-water analysis further confirmed that trees in proximity to the eruption site absorbed water with distinct isotopic signatures compared to trees in a control area. These findings provide evidence for potential changes in groundwater chemistry. Furthermore, the presence of certain trace elements found in the tree rings during and following the eruption suggest an increased availability of nutrients. This augmented nutri ent availability is likely due to volcanic activity. Despite these findings, a single factor does not clearly explain the pre-eruptive NDVI increase, rendering it an ongoing mystery. Subsequent research efforts will be key to uncovering the full picture.