Journal of Geology & Earth Sciences Volume 1| Issue 2 Research Article Open Access Holocene Vegetation and Climate Changes in Iran Sahar Maleki1, Ghasem Azizi2, Homa Rostami*,Reza Shahbazi4 1Ph.D. Candidate in Climatology, Faculty of Geography, University of Tehran, Iran 2Professor of Faculty of Geography University of Tehran, Iran 3Ph.D. Candidate in Climatology, Faculty of Geography, University of Tehran,I ran 4Ph.D Natural resources and engineering, Director Management of Geohazards, Engineering and Environmental Geology. *Corresponding author: Homa Rostami, Ph.D. Candidate in Climatology, Faculty of Geography, University of Tehran; Email: [email protected] Citation: Homa Rostami (2019) Holocene Vegetation and Climate Changes in Iran: Nessa Journal Geology & Earth Sciences. Received: 6th September 2019; Accepted: 11th September 2019; Published: 4th October 2019 Copyright: © 2019 Homa Rostami et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract There is not much information about the characteristics of the paleoclimate in Iran. Most studies are often scattered and mainly focuses on places in the west and northwest regions of Iran also many researches have also been written in Persian. This review focuses on the Iran's vegetation and climate changes over the last 20000 years, by using results of Persian and English scientific papers and thesis about paleoclimate of Iran. Understanding the interaction between climate and environment requires a nuanced, multidisciplinary understanding of the past. According to studies conducted in the north and west of Iran during glacial periods, there were cold and dry climate conditions and during the interglacial periods there was warm and humid climate. Steppe vegetation indicates cold and dry conditions and increase in trees represents an increase in moisture during interglacial periods. The transition from glacial to interglacial and changing atmospheric systems has led to different vegetation ecosystems in different parts of Iran. In general, the cycles and known events in different parts of the world have not been well identified in Iran, and our knowledge of the paleoclimate and paleoecological conditions of Iran is not enough. In order to arrive at a precise and comprehensive cognition of the paleoecological conditions of Iran, various proxies, especially for the central, eastern and southern parts of Iran, are needed. Palynological information obtained from sedimentary cores and tree rings helps identify the state of Iran's paleocology. Keywords: Paleoclimate, tree rings, geochronology, pollen, sedimentary core. Nessa Publishers| www.nessapublishers.com Page 1 Journal of Geology & Earth Sciences Volume 1| Issue 2 Introduction Vegetation in each region is affected by climatic and geographical conditions and human, therefore, the study of vegetation changes over time provides useful information on past climate change. Palynology is the most important tool in reconstructing of vegetation and the paleo environment. It is also widely used in taxonomy, genetics and evolution, climate change, archeology, geology, allergology, and jurisprudence (Fægri, and Iversen, 1989). Many palynalogical studies have been conducted in different countries, especially North America and Europe and history of vegetation during the Quaternary period have been reconstructed. Leroy & Arpe (2007) have examined potential habitats for green summer trees in Europe and Southwest Asia during the last glacial period (LGM). In their studies, they introduced small regions of southern Europe such as Spain, Italy, Greece and parts of northern Turkey, the eastern shores of the Black Sea and southern Caspian Sea regions as green summer tree shelters. The Fertile Crescent, its hilly flanks and surrounding drylands have long been a critical region for studying human societal change, first, as being an initial stepping point out of Africa for the first anatomically modern humans (Bae, Douka, & Petraglia, 2017; Hershkovitz et al.,2018), and then as a center for some of the earliest agricultural villages (Barker, 2009; Willcox, Buxo, & Herveux, 2009) and cities (Lawrence, Philip, Hunt, Snape-Kennedy, & Wilkinson, 2016; Ur, 2017). Since these early developments, the region has been the scene of many further social, technological and economic changes and exchanges (Jones et al., 2018).This review focuses on the eastern parts of Levant on the region from present day Iran especially Zagros Mountains. The last 20,000 years witnessed one of the most dramatic global climatic changes (glacial/interglacial transition), but also includes the full scope of Holocene climatic variability. This time period also includes the development of agriculture. The frequency of Ouercus pollen, Pistachio, Artemisia, Chenopodiaceae, Grasses and pollen of other dominant plants has been used to determine temperature and precipitation variations (Horowitz, 1971. Van Zeist & Bottema, 1991. Roberts& Wright, 1993. Rossignol-Strick, 1995). Zaribar Lake is one of the first places to be studied in the Middle East. From this lake, several sedimentary cores were taken from 1961 to 1970. Quaternary paleoecological studies in Iran more focused on lake sediments in western and northwestern Iran. Djamali et al. (2008) about Urmia lake and Rmezani et al. (2008) about southern Caspian forests have done paleoecological studies. Lake Mirabad (at Lorestan province) is the other sites of Paleoecological Zone of Zagros, which have been investigated in various ways, such as palynology (Van Zeist & Bottema, 1977). Ostracoda (Griffiths et al.2001), and stable isotopes (Stevens et al.2006). Palynological studies about lake Neor (in Ardebil province) done by Azizi et al. (2013), Akbari (2011) and Salmani (2013). Ponel et al. (2013) have been studied on pollen and insects fossils of Neor lake. Lashkari et al. (1989) has reconstructed the Bakhtegan lake paleoclimate changes based on clay mineralogy evidences. Paleoclimate studies shows that Holocene period following the melting of the glaciers in the late glacial period and warming of climate, began about 11000 years ago, at the same time sea level rose, also conditions were favorable for the growth of trees and the expansion of forests. The results of palynology researches have shown that in the glacial periods in the western regions of Iran, steppe vegetation especially Artemisia and Chenopodiaceae has been dominated (Djamali et al. 2008). The Pistachio and Oak trees was gradually increased from late glacial to Holocene. With the onset of Holocene, Poaceae suddenly replaced by Artemisia and Chenopodiaceae (Azizi et al., 2013). In 12,000 to Nessa Publishers| www.nessapublishers.com Page 2 Journal of Geology & Earth Sciences Volume 1| Issue 2 6,000 years ago, the Southwest Asia has had warmer and longer summer than the current conditions. Such conditions led to the disappearance of many shallow lakes and seasonal rivers, also vegetation changed. Studies conducted in north and west of Iran, the climate has changed between cold and dry climate during glacial and warm and humid conditions during interglacial periods (Horowitz, 1971). The lake sediments and the paleosol layers in the Loess deposits indicate an increase in moisture during the periods between the last glacial and the pre LGM (kehl, 2009). Studies in Iran's lakes such as Zaribar, Urmia, Mirabad and comparisons with Lake Van in Turkey indicate a roughly similar vegetation variation. Most studies have shown that the end of the Younger Dryas event and the beginning of the Holocene period have been accompanied by a sudden decrease in Chenopodiaceae (a representative of the cold and dry climate) and abrupt increase in Poaceae (a representative of the warm climate) (Davoodi et al,2014). Current condition in Iran is affected by the changes that occurred during the mid-Holocene (5,500-6,000 years ago) oak forests grew and expanded (wright et al., (1978), El-Moslimany et al.,(1986), Djamali et al., 2008, Stevens et al., 2001). The pollen diagrams of the Lake Maharlou in Fars province indicate that the walnut trees was planted in 4500 years ago at Fars province ,at the northwestern regions of Iran, however, planting of the walnut tree began a little later and started 4000 years ago (Djamali et al.,2009). Due to the fact that climate events in Iran are not well known and our knowledge of the ecological conditions of Iran is very small, this study attempts to analyze the results of paleoclimate researches and ultimately to a comprehensive understanding of Iran's vegetation changes during Holocene. Knowing the impact of paleoclimate change on plant communities and the environment makes we better predict future changes and we can prevent some crises. Methods In this research, the results of the Persian and English papers, thesis and the scientific researches written about paleoclimate of Iran were used. After reviewing the researches, results about vegetation in different periods separated and arranged. The information extracted was based on the name of the region, latitude and longitude, the method used, the results of the study and the results that the research gives us. We provide a multidisciplinary, multiscalar perspective on the relevance of past climate and environmental condition of Holocene in Iran. Eventually we provided a comprehensive overview of climate change and