Abstract
Key messageBased on the first dendroclimatological analyses of the thermo-Mediterranean treePyrus bourgaeana, the positive relationship between the growth and climate (i.e., precipitation) has strengthened in recent decades.The combined effect of climate change and habitat destruction and fragmentation threatens many plant populations and even entire communities in Mediterranean ecosystems. The Iberian pear, Pyrus bourgaeana Decne, a characteristic species of Mediterranean ecosystems, is threatened by both habitat and climate changes. We ask whether and how the growth of mature P. bourgaeana in the thermo-Mediterranean zone (i.e., altitude <700 m) has been affected by long-term climate changes during the last century in a fragmented landscape. Dendrochronological methods were used to find growth–climate relationships. We made the first dendroclimatological analyses and constructed a first 103-year tree-ring chronology (1905–2007) of this species. The tree-ring series revealed large growth variability. We found a clear, strong relationship between tree growth and climate, with annual precipitation being the most important climate factor enhancing radial growth. Our results also showed that warm autumns and winters positively affect growth. There was no temporal stability in the relationship between tree growth and climate. The most general trend was in the relationship between annual precipitation and tree growth: the decrease of rainfall in the last decades of the twentieth century was associated with a constant increase of the correlation coefficient. Water accumulated in the soil in autumn and winter proved to be a key factor augmenting tree growth in the following vegetation period. The climate–growth relationship in P. bourgaeana has strengthened in recent decades apparently due to decreased precipitation levels.
Highlights
Most models of climate change predict global warming associated with a marked variation of the level and spatiotemporal distribution of precipitation and temperature (IPCC 2014; Fischer and Schar 2010; Hoerling et al 2012)
The positive relationship between tree growth and mean temperature in autumn and winter strengthened in the second half of the studied period, coinciding with an increasing mean temperature trend; we found the same trend for February (Fig. 5)
The influence of annual precipitation becomes more important for tree growth in the late twentieth and early twenty-first centuries, when annual precipitation decreased and it probably became most limiting
Summary
Most models of climate change predict global warming associated with a marked variation of the level and spatiotemporal distribution of precipitation and temperature (IPCC 2014; Fischer and Schar 2010; Hoerling et al 2012). Because trees are long-lived organisms, their ring series record long-term year-to-year changes in climate conditions (Schweingruber 1996; Nicault et al 2008; Olano et al 2008, 2012). Due to their complex physiology, trees may respond to climatic changes in complex ways (Drew et al 2013; Olano et al 2014; Zang et al 2014). Changes in the constraining factors may cause temporal instability in the relationship between climate and tree growth that modulates the response patterns of tree growth (Briffa et al 1998, 2002; D’Arrigo et al 2008; Briffa and Matthews 2002; Leburgeois et al 2012)
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