Reconstruction of Spring-Summer Maximum Temperatures Based on a Regional Chronology (1750-2010) in the Western Ridge of Central Zagros, Iran

Long-term climate records are valuable for environmental planning، and tree rings allow records to extend to the time before the establishment of weather stations. For a better understanding of the past climate fluctuation and to mitigate the effect of climate fluctuation، dendroclimatic reconstructions have been applied in many parts of the world. Inter annual variations of climate have an intensive effect on water resources، agriculture، human settlements and regional ecosystems. The central Zagros region of Iran experiences different climatic situations over the seasons of a year. In recent years، dramatic changes in regional climate have damaged both local forests and agriculture. Weather stations cover a short time span of instrumental data in Iran. To overcome this challenge، tree rings can be used to put recent climate trends in a long-term context of climate variability. The central Zagros Mountains are one of the most important sites of oak forest in west of Iran. However، tree-ring based climate reconstructions are still scarce for this country. In this study، we present a reconstruction of temperature variations in the central Zagros Mountains using Quercus infectoria and Quercus persica tree rings over the last 250 years (1750-2010). The study sites are located in the central Zagros Mountain range in the west of Iran. Due to the climatic regime، there is a clear distinction between a dry (summer) and a wet (winter-spring) season in this region. Our sampling sites are covered by old-growth oak forests and have the shortest distance to meteorological stations. In this study 54 cores from two species of Quercus persica in Dalab site (Ilam province) and Q. infectoria Olive in Shineh site (Lorestan province) were extracted using an increment borer. After the sample preparation، annual ring widths were measured with a LINTAB5 measuring system. The TSAP-Win software was used for cross dating and correlations between the growth corves. The growth corves were standardized with ARSTAN program to remove none climatic effects. The Expressed Population Signal (EPS; Wigley et al، 1995) was calculated for the regional chronology (RC). Monthly and seasonal maximum temperature from Ilam (1987-2010) and Khoramabad (1951-2010) weather stations were used to calibrate the regional chronology (1750-2010) during the common period (1951-2010). Based on a linear regression model، seasonal maximum temperature of spring-summer was reconstructed over the 1840-2010 period. The results of the study show that the two site chronologies are strongly correlated with each other (p)