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Calcareous sediments spanning the last 13 ka fromn I,ake Zeribar, western Iran, were sampled for stable-isotope analysis as a means of augmenting earlier climatic interpretations based on polleni and macrofossils. The Lateglacial period was cold and dry, suLpporting semi-desert vegetation and highly concentrated lake water. Low evaporation rates due to the cold resulted in long residenice times and high lake stands. Durinig the earlv Holocene, the upland vegetation changed to a pistachio-oak savanna as low temperatures and ariditv J ameliorated. Lake level dropped in response to increased evapotranspiration. The low oxygen-isotope values of lacustiine calcite during this period are interpi-eted as a relative increase in the contributioni of winiter moisture rather than overall changes in effective moistuLre. A gradual increase in oak pollen at 7 ka BP signalled the inicrease in effective moisture to levels simiiilar to those of today. At the same tinme the 5`1O values increased.A reflecting a greater percentage of "0-enriched spring rains. Modern values and seasonal distribution of precipi-HOLOCENE tation were established by 6 ka BP. A short-lived return to winter-only precipitation occuiTed at 4.5 ka BP SPECIAL ISSUE and resulted in a temporary increase in anrdity. The covariance among 6'3C, carbonate deposition and 6S'O values suggests that lake productivity is linked to these seasonal climiiatic changes.

A palynological study based on two 100-m long cores from Lake Urmia in northwestern Iran provides a vegetation record spanning 200 ka, the longest pollen record for the continental interior of the Near East.During both penultimate and last glaciations, a steppe of Artemisia and Poaceae dominated the upland vegetation with a high proportion of Chenopodiaceae in both upland and lowland saline ecosystems. While Juniperus and deciduous Quercus trees were extremely rare and restricted to some refugia, Hippophaë rhamnoides constituted an important phanerophyte, particularly during the upper last glacial sediments. A pronounced expansion in Ephedra shrub-steppe occurred at the end of the penultimate late-glacial period but was followed by extreme aridity that favoured an Artemisia steppe. Very high lake levels, registered by both pollen and sedimentary markers, occurred during the middle of the last glaciation and upper part of the penultimate glaciation. The late-glacial to early Holocene transition is represented by a succession of Hippophaë, Ephedra, Betula, Pistacia and finally Juniperus and Quercus. The last interglacial period (Eemian), slightly warmer and moister than the Holocene, was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern European pollen sequences.1 This work is dedicated to Sytze Bottema for his outstanding contribution to late Quaternary palynology of the Near East.2

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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.