Seasonal precipitation and continentality drive bimodal growth in Mediterranean forests |
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Affiliation: | 1. Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Montañana 1005, Zaragoza E-50192, Spain;2. Department of Natural Systems and Resources, Universidad Politécnica de Madrid, Madrid, Spain;3. Department of Biological Evolution, Ecology and Environmental Sciences, Faculty of Biology, Universitat de Barcelona, Barcelona, Spain;4. Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, Sevilla 41013, Spain;5. Department of Physical Geography and Geoecology, Faculty of Science, Charles University, Albertov 6, Prague 12843, Czech Republic;6. Mathematical Methods and IT Department, Siberian Federal University, Krasnoyarsk, Russia;7. Department of Crop and Forest Sciences, University of Lleida, Av. Alcalde Rovira Roure 191, Lleida E-25198, Spain;8. Joint Research Unit CTFC, AGROTECNIO, CERCA, Ctra. Sant Llorenç de Morunys km 2, Solsona 25280, Spain;9. Departamento de Biología Ambiental, Facultad de Ciencias, Universidad de Navarra, Calle Irunlarrea 1, Pamplona 31008, Spain |
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Abstract: | Tree phenology is sensitive to climate warming and changes in seasonal precipitation. Long xylogenesis records are scarce, thus limiting our ability to analyse how radial growth responds to climate variability. Alternatively, process-based growth models can be used to simulate intra-annual growth dynamics and to better understand why growth bimodality varies along temperature and precipitation gradients. We used the Vaganov-Shashkin (VS) growth model to analyse the main climatic drivers of growth bimodality in eight trees and shrubs conifers (four pines and four junipers) across Spain. We selected eleven sites with different continentality degree and spring/autumn precipitation ratios since we expected to find pronounced bimodal growth in less continental sites with spring and autumn precipitation peaks. The VS model successfully simulated annual growth rates at all sites as a function of daily temperature and soil moisture data. Bimodal growth patterns clustered into less continental sites showing low spring/autumn precipitation ratios. This finding agrees with observed climate-growth associations showing that growth was enhanced by wet-cool winter-to-spring conditions, but also by wet autumn conditions in the most bimodal sites. We observed a stronger growth bimodality in pines compared to junipers. We discuss the spatial variability of climate drivers in bimodality growth pattern and how increasing continentality and shifts in seasonal precipitation could affect growth patterns. Bimodality could be an advantageous response to overcome summer drought in Mediterranean forests. The ability of some species to reactivate growth during autumn might determine their capacity to withstand increasing summer aridity. |
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Keywords: | Vaganov-Shashkin model Phenology Radial growth Xylogenesis |
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