- 1Instituto Geológico y Minero de España (IGME-CSIC), Unidad Asociada IGME (CSIC)-Universidad de Zaragoza, Spain (unaim@igme.es)
- 2Geosphere Austria, Hohe Warte 38, 1190 Wien, Austria
- 3Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005, 50192 Zaragoza
- 4Grupo Paleomag-UBU. Escuela Politécnica Superior, Dpto. de Física. Burgos
- 5Angewandte Geowissenschaften und Geophysik, Montanuniversität Leoben, Austria
- 6Laboratorio de Paleomagnetismo CCiTUB – GEO3BCN CSIC
- 7Servicio de Planificación y Gestión Forestal. Dpto. Medio Ambiente. Gobierno de Aragón
Trees in undisturbed natural environments are known to contain ferromagnetic particles. The application of conventional paleomagnetic techniques to both living and fossil tree trunks has revealed the presence of low coercivity minerals and measurable remanences, with intermediate (300°C) unblocking temperatures and some archaeomagnetic records that are often magnetically viscous (Krs et al., 1994). However, many questions remain about the origin of the magnetization, the locking mechanisms and its stability.
There are several long-lived tree species in the Biosphere, with ages up to 35005000 years, distributed mainly in temperate (Fitzroya cupressoides) and dry mountain (Pinus longaeva) forests. Most living conifers (sequoias, pines, firs, cypresses, cedars, junipers, larches, spruces, yews) and hardwood tree species (beech species, oaks, chestnuts, etc.) have maximum ages ranging 200-1000 years. In addition, the dendrochronological record and field evidence have demonstrated the ability of certain trees to withstand multiple fires and/or direct and repeated lightning strikes. However, to the best of our knowledge, there are no studies on magnetic remanence in trees affected by fire or lightning compared to undisturbed wild trees, soils or rocks, which are better documented. Given the ages and distribution of certain tree species, the geomagnetic recording source has the potential to enhance our understanding of the secular variation of the Earth's magnetic field over the past 500-1000 years and beyond.
In this contribution, we will present the first results derived from the following working hypothesis: "Wood structures associated with lightning strikes or wild fires (including those generated internally to facilitate healing and survival) may have reliably recorded the Earth's magnetic field during the immediate aftermath of the fire (TRM and/or CRM) or in the subsequent period following the lightning strike (CRM, acquired during the healing phase)”. In order to validate or falsify this working hypothesis, several trees affected by lightning or fire were sampled in the Southern Pyrenees (External Sierras, Sto. Domingo range) between 2014 and 2019. The wood samples were analyzed in the paleomagnetic laboratories of the universities of Leoben, Burgos and Barcelona. The analyses performed included AF demagnetization of the NRM, IRM acquisition curves (and AF demagnetization). Magnetization measurements were obtained with 2G superconducting magnetometers in all cases. Additionally, preliminary observations were conducted using a JEOL 6010 Plus scanning electron microscope (located at the IGME headquarters in Tres Cantos, Madrid), operating in low vacuum mode with a backscattered electron detector and EDS microanalysis.
Krs M, Krsová M, Pruner P, Čápová J, Parés JM (1994) Magnetism of subfossil and fresh wood: initial reports. In: Růžičková E, Zeman A (eds) Holocene flood plain of the Labe River. Geol Inst Acad Sci, Praha, pp 51-65
How to cite: Pueyo, E. L., Egi, R., Camarero, J. J., Sánchez-Moreno, E. M., Calvín, P., Scholger, R., Mata, M. P., Beamud, E., and Compaired, F.: Geomagnetic record in trees affected by fires or lightning?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6866, https://doi.org/10.5194/egusphere-egu25-6866, 2025.