Early detection of volcanic eruptions is of major importance for protecting human life. Ground deformation and changes in seismicity, geochemistry, petrology, and gravimetry are used to assess volcanic activity before eruptions. Studies on Mt. Etna (Italy) have demonstrated that vegetation can be affected by pre-eruptive activity before the onset of eruptions. During two consecutive years before Mt. Etna's 2002/2003 flank eruption, enhanced vegetation index (NDVI) values were detected along a distinct line which later developed into an eruptive fissure. However, the mechanisms by which volcanic activity can lead to changes in pre-eruption tree growth processes are still not well understood. We analysed δ¹³C, δ¹⁸O and ¹⁴C in the rings of the survived trees growing near to the line where the pre-eruptive increase in NDVI was observed in order to evaluate whether the uptake of water vapour or fossil volcanic CO₂ could have contributed to the enhanced NDVI. We found a dramatic decrease in δ¹⁸O in tree rings formed before 2002/2003 in trees close to the eruption fissure, suggesting uptake of volcanic water by trees during pre-eruptive magma degassing. Moist conditions caused by outgassing of ascending magma may also have led to an observed reduction in tree-ring δ¹³C following the eruption. Furthermore, only ambiguous evidence for tree uptake of degassed CO₂ was found. Our results suggest that additional soil water condensed from degassed water vapour may have promoted photosynthesis, explaining local increases in NDVI before the 2002/2003 Mt. Etna flank eruption. Tree-ring oxygen stable isotopes might be used as indicators of past volcanic eruptions.

中文翻译：

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树木年轮稳定同位素和放射性碳揭示了火山过程对埃特纳火山（意大利西西里岛）树木喷发前后的影响

及早发现火山喷发对于保护人类生命至关重要。地面变形和地震活动、地球化学、岩石学和重力测量的变化用于评估火山爆发前的火山活动。对埃特纳火山（意大利）的研究表明，在火山爆发之前，植被会受到火山爆发前活动的影响。在埃特纳火山 2002/2003 年侧翼喷发前的连续两年中，沿着一条明显的线检测到了增强的植被指数 (NDVI) 值，该线后来发展为喷发裂缝。然而，火山活动导致喷发前树木生长过程发生变化的机制仍不清楚。我们分析了 δ ¹³ C、δ ¹⁸ O 和¹⁴生长在观察到 NDVI 爆发前增加的线附近的存活树木的年轮中的 C 以评估水蒸气或化石火山 CO ₂的吸收是否可能导致 NDVI 增加。我们发现2002/2003 年之前在靠近喷发裂缝的树木中形成的年轮中 δ ¹⁸ O急剧减少，这表明在喷发前岩浆脱气期间树木吸收了火山水。上升的岩浆脱气引起的潮湿条件也可能导致喷发后观察到的树木年轮 δ ¹³ C减少。此外，树木吸收脱气 CO _{2 的}证据不明确被找到。我们的结果表明，脱气水蒸气凝结的额外土壤水可能促进了光合作用，这解释了 2002/2003 年埃特纳火山侧翼喷发前 NDVI 局部增加的原因。树轮氧稳定同位素可用作过去火山喷发的指标。