Scientific research

As research scientist, my main field of study have been dendrochronology and forest ecology. My PhD thesis was focused on research methods of dendrochronology with application in the study of tree growth in relation to climate in Mediterranean forests.

Dendrochronology is the science of measuring and dating the growth rings of woody plants. In those lands where seasonality of climate is marked, the radial growth of trees stops during the harsher seasons (normally, the cold season in temperate climate), thus annual rings are formed.

Research methods of dendrochronology are applied in different disciplines, including several fields of geosciences. Important developments of dendrochronological methods have been achieved in archaeology: archeologists recognize dendrochronology as an accurate tool for absolute dating, i.e. to estimate the age of wooden artifacts.

Tree rings store information about the natural environment and can be used to study the processes and dynamics occurring in the surroundings where trees live. Tree rings are referred to as “proxy data", that means they are suitable as biological substitute records for environmental conditions and ecological events. That is because radial stem increment is influenced by a number of external factors, among which there are some that drive the growth and whose variability is most likely to be reflected in a tree-ring sequence. The relationships between tree ring growth and external factors can be modelled with statistical techniques. Using predictive models with very long tree ring chronologies from very old trees, ancient wooden artefacts or fossil wood, the past climate and other ecological processes (as mass movements, fires or outbreaks of forest pathogens) can be reconstructed.

Different subfields of dendrochronology are defined according to the ecological process the scientist deals with, for instance dendroecology, dendroclimatology, dendrohydrology, dendrogeomorphology, dendroglaciology.

Scientific research achievements

I accomplished the first dendrochronological studies in the province of Huelva, SW Spain. These included tree ring data of the species Quercus ilex (Mediterranean evergreen oak), which are very rare due to the highly difficult analysis of the wood anatomy of this species. I was able to measure and date tree ring chronologies of Quercus ilex trees older than 100 years, which are among the very rare examples existing in the whole Mediterranean region. They were published in the peer-reviewed scientific journal Dendrochronologia in 2016.
I measured and dated the longest known (at least until 2017) tree ring chronology of the Mediterranean stone pine Pinus pinea which were also published in the peer-reviewed scientific journal Dendrochronologia in 2016, and listed in the Rocky Mountain Tree-Ring Research OLDLIST database.
My researches have opened a new field of scientific research at the University of Huelva and represent the highest achievement in this discipline in this institution at least until 2017.
One of my scientific posters was awarded a prize for distinguished PhD student’s poster during an international congress in 2014, and my PhD dissertation was awarded with Latin honors.

An example of dendrogeomorphology. On the left, the picture shows a section of the stem of a tree some years after a landslide. Mass movements affect tree ring growth and can be dated on tree ring patterns. This permits to use tree rings as proxy data to reconstruct past geological processes. I took the picture at the Dendroecology Lab of the WSL (Swiss Federal Institute for Forest Snow and Landscape Research).

Dendroclimatology: variability of climate is reflected in tree ring growth patterns. This permits to identify the climatic factors and climate changes that most influence tree growth, as weel as to use tree rings as proxy data to reconstruct past climate (how climate was before meteorological station records).

The picture on the left shows me extracting samples from a living tree. The samples are prepared for analysis as shown in the picture in the centre. On the right, tools for tree ring analysis at the laboratory of the University of Huelva: samples are observed through a stereomicroscope, and tree-ring data are recorded using a measurement station connected to a software for visualization, manipulation and statistics of tree ring data.

In Spain, my colleagues and I have carried out dendroecological studies in the tree species Quercus ilex and Pinus pinea, including unprecedented studies in Andalusia (Southern Spain) under highly variable Mediterranean climate. We studied the effects of climate change on tree growth dynamics in these ecosystems.

My PhD dissertation, “A dendroecological approach to growth dynamics of Mediterranean forests in South-western Spain : climate change impacts, vulnerability and adaptive capacity”, is available in the institutional repository of the University of Huelva, at this link.

Growth rings of Mediterranean evergreen oak, Quercus ilex, (above) and Mediterranean stone pine, Pinus pinea (below).

I took these pictures through a stereo microscope; the samples are from forests of the province of Huelva, Spain.

Publications in peer-reviewed scientific journals:

Natalini F., Alejano R., Pardos M., Calama R., Vázquez-Piqué J., 2024. Declining trends in long-term Pinus pinea L. growth forecasts in Southwestern Spain. Dendrochronologia 88 (2024) 126252, DOI: https://doi.org/10.1016/j.dendro.2024.126252
Gea-Izquierdo G., Natalini F., Cardillo E., 2020. Holm oak death is accelerated but not sudden and expresses drought legacies. Science of The Total Environment 754, February 2021, 141793; link.
Andivia E., Natalini F., Fernández M., Alejano R., Vázquez-Piqué J., 2018. Contrasting holm oak provenances show different field performance but similar resilience to drought events eight years after planting in a Mediterranean environment. iForest - Biogeosciences and Forestry 11: 259-266; link.
Natalini F., Alejano R., Vázquez-Piqué J., Pardos M., Calama R., Büntgen U., 2016. Spatiotemporal variability of stone pine (Pinus pinea L.) growth response to climate across the Iberian Peninsula. Dendrochronologia, 40: 72-84; link.
Natalini F., Alejano R., Vázquez-Piqué J., Cañellas Is, Gea-Izquierdo G., 2016. The role of climate change in the widespread mortality of Holm oak in open woodlands of Southwestern Spain. Dendrochronologia, 38: 51-60; link.
Natalini F., Correia A. C., Vázquez-Piqué J., Alejano R., 2015. Tree rings reflect growth adjustments and enhanced synchrony among sites in Iberian stone pine (Pinus pinea L.) under climate change. Annals of Forest Science 72 (8): 1023–1033; link.

Scientific conference presentations:

Natalini F., Alejano R., Pardos M., Calama R., Vazquez-Piqué J., 2024 Declining trends in long-term Pinus pinea L. growth forecasts in Southwestern Spain. TRACE 2024 – Tree Rings in Archaeology, Climatology and Ecology; BRAȘOV, ROMANIA, 3 - 8 JUNE 2024. https://silvic.unitbv.ro/en/646-trace2024.html
Vázquez-Piqué J., Natalini F., Alejano R., 2019. Influencia de factores climáticos en la probabilidad de existencia de anillos ausentes: el caso del pino piñonero en el suroeste peninsular. Reunión del grupo de Ecología, Ecofisiología y Suelos forestales. Bases ecológicas para la gestión adaptativa de sistemas forestales. Alcalá de Henares (Madrid), 8-9 May 2019 [oral presentation] link.
Natalini F., Morales M., Alejano R., Calama R., Gallardo C., Pardos M., Vázquez-Piqué J., 2017. Prediction of tree growth under climate change scenarios using tree rings of Pinus pinea L. in Spain. XIV MEDECOS & XIII AEET meeting, Seville, Spain, 31 January – 4 February 2017 [poster]; link.
Natalini F., Alejano R., Vázquez-Piqué J., 2016. Diverse growth-climate relationships and response to climate change in Mediterranean pine woodlands in the Iberian Peninsula. Third American Dendrochronology Conference Ameridendro, Mendoza, Argentina, 28 March - 1 April 2016 [oral presentation]; link.
Natalini F., Alejano R., Vázquez-Piqué J., 2015. Growth dynamics of Mediterranean woodlands under climate change: a dendroecological approach in southwest Iberia. 10th Congress of the Italian Society of Silviculture and Forest Ecology SISEF, Florence, Italy, 15-18 September 2015 [poster]; link.
Natalini F., Alejano R., Vázquez-Piqué J., 2015. Testing tree-ring climate proxies and detrending methods in Southwestern Iberian Pinus pinea L. ecosystems. Tree Rings in Archaeology, Climatology and Ecology TRACE, Seville, Spain, 20-23 May 2015 [poster]; link.
Natalini F., Alejano R, Vázquez-Piqué J., 2014. Climate change-controlled dendroecological signal in Pinus pinea in Southern Spain. 5th International Conference on Mediterranean Pines MedPine5, Solsona, Spain, 22-26 September 2014 [poster]; link.
Natalini F., Alejano R, Vázquez-Piqué J., 2014. Plasticity in the dendroclimatic signal of Pinus pinea in connection to climate variability within its distribution range. European Dendrochronology Conference EuroDendro, Lugo, Spain, 8-12 September 2014 [oral presentation]; link.
Natalini F., Alejano R., Vázquez-Piqué J., Cañellas I., Gea-Izquierdo G., 2013. Growth trends and sensitivity to climate of declining Mediterranean open woodlands exhibiting widespread mortality in Southern Spain. Second American Dendrochronology Conference Ameridendro, Tucson, USA, 13-17 May 2013 [poster]; link.

Scientific conference proceedings:

Natalini F., Alejano R., Vázquez-Piqué J., (2017). Métodos dendroclimatológicos en bosques de Pinus pinea L. en España: estandarización de series de anchura de anillos y validación de datos climáticos. Actas del 7º Congreso Forestal Español, Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Natalini F., Garriga E., Vázquez-Piqué J., (2017). Técnicas y herramientas para la preparación de muestras extraídas de árboles para el análisis dendrocronológico. Actas del 7º Congreso Forestal Español, Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Natalini F., Alejano R., Büntgen U., Calama R., Pardos M., Vázquez-Piqué J., (2017). Plasticidad en la respuesta del crecimiento de Pinus pinea L. a la variabilidad espaciotemporal del clima en España: una aproximación dendrocronológica. Actas del 7º Congreso Forestal Español, Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Andivia, E., Natalini, F., Alejano, R., Fernández, M., Vázquez-Piqué, J. (2017). Respuesta de dos procedencias de encina a eventos de sequía: una aproximación dendroecológica. Actas del 7º Congreso Forestal Español,Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Vázquez-Piqué J., Alejano R., Calama R., Natalini F. , Madrigal G., Conde M., Pardos M. (2017). Fenología del crecimiento secundario de pino piñonero (Pinus pineaL.) en zonas de clima contrastado de la Península Ibérica. Actas del 7º Congreso Forestal Español,Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Calama R., Montero G., Vázquez-Piqué J., Alejano R., Gordo F.J., Moro J., Gandía R., Camacho V., Natalini F., Madrigal G., Conde M., Pardos M. (2017). Indicadores de sostenibilidad en la gestión forestal actual de las masas de Pinus pinea L. Actas del 7º Congreso Forestal Español,Sociedad Española de Ciencias Forestales, ISBN 978-84-941695-2-6; link.
Natalini F., Alejano R., Vázquez-Piqué J., 2016. Dendroclimatic signal in managed Mediterranean forests. A case study in SW Spain. In: Hevia A. et al. (Eds.), TRACE Volume 14, Proceedings of the Dendrosymposium 2015, GFZ German Research Centre for Geosciences, ISSN: 2190-7110, pp. 102-110; link.
Natalini F., Alejano R., Vázquez-Piqué J., Cañellas I., Gea-Izquierdo G.,2013. Dendroecología de Pinus pinea L. en el suroeste de España y su aplicación para el estudio de la vulnerabilidad de especies forestales ante el cambio global. In: Montero González, Guijarro Guzmán (Eds.) Actas del 6º Congreso Forestal Español, chapter 068, Sociedad Española de Ciencias Forestales, ISBN: 978-84-937964-9-5; link.