Indian Summer Monsoon variations could have affected the early-Holocene woodland expansion in the Near East

Abstract

Postglacial expansion of deciduous oak woodlands of the Zagros—Anti-Taurus Mountains, a major biome of the Near East, was delayed until the middle Holocene at ~6300 cal. yr BP. The current hypotheses explain this delay as a consequence of a regional aridity during the early Holocene, slow migration rates of forest trees, and/or a long history of land use and agro-pastoralism in this region. In the present paper, support is given to a hypothesis that suggests different precipitation seasonalities during the early Holocene compared with the late Holocene. The oak species of the Zagros—Anti-Taurus Mts, particularly Quercus brantii Lindl., are strongly dependent on spring precipitation for regeneration and are sensitive to a long dry season. Detailed analysis of modern atmospheric circulation patterns in SW Asia during the late spring suggests that the Indian Summer Monsoon (ISM) intensification can modify the amount of late spring and/or early summer rainfall in western/northwestern Iran and eastern Anatolia, which could in turn have controlled the development of the Zagros—Anti-Taurus deciduous oak woodlands. During the early Holocene, the northwestward shift of the Inter-Tropical Convergence Zone (ITCZ) could have displaced the subtropical anticyclonic belt or associated high pressure ridges to the northwest. The latter could, in turn, have prevented the southeastward penetration of low pressure systems originating from the North Atlantic and Black Sea regions. Such atmospheric configuration could have reduced or eliminated the spring precipitation creating a typical Mediterranean continental climate characterized by winter-dominated precipitation. This scenario highlights the complexity of biome response to climate system interactions in transitional climatic and biogeographical regions.

Vegetation dynamics in the Northeastern Mediterranean region during the past 23 000 yr: insights from a new pollen record from the Sea of Marmara

“…Conversely, a late reforestation (only after 8 ka) occurred in the drier parts of the Near East, in sites located in southernmost Europe, and in continental zones. This might be explained by a dry early Holocene where moisture levels were below the tolerance threshold for tree growth or a by a change from summer/spring to winter precipitation in sites located in Anti-Taurus-Zagros Mountains (van Zeist and Bottema, 1991;Stevens et al, 2001;Bottema and Sarpaki, 2003;Wick et al, 2003;Wright et al, 2003;Tzedakis, 2007;Djamali et al, 2010). We can conclude that the northern borderland of Southern Europe can be considered a transitional zone where the moisture level determined an earlier (ca.…”

“…Recently, climate simulations have shown that across the early Holocene stronger winter precipitation occurred over the Northeastern Mediterranean (near Turkey), while there is little evidence for summer precipitation in the Eastern Mediterranean (Brayshaw et al, 2011). The mechanism associated with winter precipitation in Eastern Mediterranean is not yet fully understood (Giorgi and Lionello, 2008), while it has been shown that strengthening/weakening of the Indian Monsoon is related with increase/decrease in spring precipitation in AntiTaurus-Zagros region (Djamali et al, 2010). Evidence from palaeo-data suggests that negative rainfall anomalies in the Black Sea region occurred during phases of high North Atlantic Oscillations (NAO) causing intervals of lower claylayer frequencies (Lamy et al, 2006).…”

Hydrological variability in the Northern Levant: a 250 ka multi-proxy record from the Yammoûneh (Lebanon) sedimentary sequence

“…During interglacial peaks, maximum tree pollen percentages reflect warm conditions and higher precipitation from the mid-latitude westerly system. Changes in seasonality were proposed by several authors to explain Holocene climate in the region (Stevens et al, 2001(Stevens et al, , 2006Magny, 2007;Tzedakis, 2007;Peyron et al, 2010;Djamali et al, 2010). At Yammoûneh, sharp δ c increases in phase with arboreal pollen peaks, attributed to enhanced seasonal thermal and hydrological contrasts, suggest that the hypothesis of seasonal changes is valid for older interglacial stages (e.g., MIS 5.5 and MIS 5.1).…”

Age-dependent response to extreme Mediterranean climate in annual rings of brant’s oak (Quercus brantii Lindl.)

“…Quercus brantii (Lindl.) is the most abundant deciduous species through Zagros-Anti-Taurus Mountains in west of the Iranian plateau and its survival is considered to be strongly dependent on early spring precipitation, and is sensitive to long drought periods (Djamali et al, 2010). Despite its wide range of distribution, no dendrochronological evidence of this species is available.…”