title: Insensitivity of Tree-Ring Growth to Temperature and Precipitation Sharpens the Puzzle of Enhanced Pre-Eruption NDVI on Mt. Etna (Italy).
abstract: On Mt. Etna (Italy), an enhanced Normalized Difference in Vegetation Index (NDVI) signature was detected in the summers of 2001 and 2002 along a distinct line where, in November 2002, a flank eruption subsequently occurred. These observations suggest that pre-eruptive volcanic activity may have enhanced photosynthesis along the future eruptive fissure. If a direct relation between NDVI and future volcanic eruptions could be established, it would provide a straightforward and low-cost method for early detection of upcoming eruptions. However, it is unclear if, or to what extent, the observed enhancement of NDVI can be attributed to volcanic activity prior to the subsequent eruption. We consequently aimed at determining whether an increase in ambient temperature or additional water availability owing to the rise of magma and degassing of water vapour prior to the eruption could have increased photosynthesis of Mt. Etna's trees. Using dendro-climatic analyses we quantified the sensitivity of tree ring widths to temperature and precipitation at high elevation stands on Mt. Etna. Our findings suggest that tree growth at high elevation on Mt. Etna is weakly influenced by climate, and that neither an increase in water availability nor an increase in temperature induced by pre-eruptive activity is a plausible mechanism for enhanced photosynthesis before the 2002/2003 flank eruption. Our findings thus imply that other, yet unknown, factors must be sought as causes of the pre-eruption enhancement of NDVI on Mt. Etna.
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.|Department of Geography, University of Zurich, Zürich, Switzerland.
authors.forename: Ruedi
authors.initials: R
authors.lastname: Seiler
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.|Department of Environmental Systems Science, ETH Zurich, Zürich, Switzerland.
authors.forename: James W
authors.initials: JW
authors.lastname: Kirchner
authors.affiliation: Navarino Environmental Observatory, Messinia, Greece.|Institutionen för Naturgeografi, Stockholm University, Sweden.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Krusic
authors.affiliation: Dipartimento di Bioscienze e territorio, Università del Molise, Contrada Fonte Lappone, Pesche, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Tognetti
authors.affiliation: Department of Earth Sciences, ETH Zurich, Zürich, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Houlié
authors.affiliation: Osservatorio Etneo, INGV, Sezione di Catania, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Andronico
authors.affiliation: Università di Palermo, Palermo, Italy.
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Cullotta
authors.affiliation: Department of Geography, University of Zurich, Zürich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Egli
authors.affiliation: Lamont-Doherty Earth Observatory, Palisades, New York, United States of America.
authors.forename: Rosanne
authors.initials: R
authors.lastname: D'Arrigo
authors.affiliation: Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.|Department of Geography, University of Zurich, Zürich, Switzerland.|Lamont-Doherty Earth Observatory, Palisades, New York, United States of America.
authors.forename: Paolo
authors.initials: P
authors.lastname: Cherubini
mesh_terms: D002980:Climate; D007558:Italy; D010788:Photosynthesis / Q000502:physiology; D011891:Rain; D013696:Temperature; D014197:Trees / Q000254:growth & development*; D018707:Volcanic Eruptions