Multi-centennial reconstruction of drought events in South-Western Iran using tree rings of Mediterranean cypress (Cupressus sempervirens L.)

摘要

Semi-arid regions are among the most vulnerable areas prone to the negative impacts of climate change. Long-term high-resolution proxy climate data will enable us to put the recent climate trends into a long-term context of natural climate variability. We developed the hitherto first regional ring-width chronology (1450-2015C.E.) from Cupressus sempervirens L. in the Zagros Mountains, western Iran and reconstructed precipitation variability for the semi-arid region during the period 1560-2015C.E. Climate-growth relationships revealed that precipitation and minimum temperatures are positively correlated with radial growth, whereas maximum temperatures reveal negative impacts. Spatial correlations with gridded precipitation data, Palmer drought severity index (PDSI), and standardized precipitation-evapotranspiration index (SPEI 01) further indicate that the climate signals contained in tree-ring width variations capture the precipitation variability in the Near East and other eastern Mediterranean regions. The southern Zagros Mts. experienced multiple megadroughts during the reconstructed period. The longest dry period occurred from 1956 to 1971 and the highest frequency of dry events occurred in the 20th century. In addition, documented famines in Iran occurred within prolonged droughts. The southern Zagros Mts. has experienced high frequency of extreme/severe dry events and long dry phases during the Little Ice Age (1560-1850C.E.). The reconstructed dry and wet events occurred irregularly, and one-year and two-year drought/wet events showed the highest frequency during the reconstructed period, highlighting the importance of sustainable water management strategies for the semi-arid southern Zagros region.