Imprisoned in the Cretan mountains: How relict Zelkova abelicea (Ulmaceae) trees cope with Mediterranean climate

Abstract

• We established the first ever centennial chronology for a broadleaved tree on Crete.• Zelkova abelicea is most sensitive to precipitation and drought in May-June.• No growth change can be related to the increase in dry conditions of the past decades.• Z. abelicea has a high capacity to withstand changing environmental conditions.We investigate the sensitivity of the relict, endemic Cretan tree species Zelkova abelicea (Lam.) Boiss. (Ulmaceae) to several climate variables (temperature, precipitation and drought). For this purpose, we establish the first centennial tree-ring chronology for the species, and the first ever tree-ring chronology for a broadleaved species on Crete. We demonstrate the strong sensitivity of Z. abelicea towards precipitation and drought in late spring to early summer and the absence of a significant response to abundant precipitation occurring during winter or early spring. Whereas the late spring sensitivity is strong and consistent through time, the species seems to be experiencing a loss of signal towards early summer conditions since the 1970s, interpreted as an earlier cessation of cambial activity due to the increase in summer drought conditions on Crete. However, despite a reduced vegetative period, no significant decrease in radial growth of Z. abelicea was observed in the tree-ring series for the last decades, thus highlighting the capacity of Z. abelicea to withstand changing environmental conditions.

From glacial refugia to hydrological microrefugia: Factors and processes driving the persistence of the climate relict tree Zelkova sicula

“…On the other side, such variability confined relict taxa to very peculiar and spatially delimited locations. Accordingly, the two Mediterranean highly relictual trees Z. abelicea and Z. sicula remained “trapped” within their refugial niches on Crete and Sicily, respectively, at high elevation (Bosque et al., 2014; Fazan et al., 2017), or in topography‐driven mesic environments (Garfì et al., 2011; Goedecke & Bergmeier, 2018; Kozlowski et al., 2014) such as hydrological microrefugia, relatively decoupled from the regional climate.…”

Using phylogeography to define conservation priorities: The case of narrow endemic plants in the Mediterranean Basin hotspot

“…The persistence by longevity and/or vegetative reproduction for long-lived plants in stable habitats such cliffs or rocky outcrops is a major biological trait that explain the long-term viability of relict narrow endemics in the MBR (García & Zamora 2003, García 2008. Some recent studies that focused on the response of single species (e.g., Fazan et al 2017, about the narrow Cretan endemic tree Zelkova abelicea) or on entire plant communities (e.g., Henne et al 2015) underline also that we may have underestimated the ecological amplitude and tolerance to climatic changes of many socalled 'temperate' species that thrive on Mediterranean mountains but could tolerate drier and warmer climates. These patterns probably explain why most of the analyzed studies have focused on the long-lived MNEs occuring on stable ecosystems, notably cliff and other rocky habitats.…”

When scientists become detectives: investigating systematic tree poisoning in a protected cove

“…Symptoms of declining tree health and dieback can be caused by a wide range of factors other than poisoning, such as changes in climate (Choat et al, 2018), environmental conditions (Fazan et al, 2017;Madrigal-Gonz alez et al, 2017), mechanical injury (Stoffel et al, 2005;Stoffel and Bollschweiler, 2008;Stoffel and Klinkmüller, 2013), nutrient deficiency (Gessler et al, 2017), defoliating insect attacks (Das et al, 2016;Saulnier et al, 2017;Panzavolta et al, 2018), nematodes (Calvão et al, 2019;Eisenback et al, 2015), fungi (Crous and Wingfield, 2018;Schmidt, 2006), or viruses (Agrios, 2004). Usually, whenever a vascular plant is experiencing stress due to one or several of these factors, it will become less resilient and thereby more susceptible to disease (Anderegg et al, 2015;Camarero et al, 2015;Navarro-Cerrillo et al, 2019).…”