Mountain forest islands and holocene environmental changes in central asia:: A case study from the southern Gobi Altay, Mongolia

A multi-proxy case study conducted on Central Asia's most isolated mountain forest sheds light on the apparent decline of forest in the Subboreal time period and the incisive environmental changes from dark taiga to steppe in the Gobi Altay of Southern Mongolia over the last 5000 yr. New vegetation records from the 'Gobi Gurvan Saykhan' (43 degrees 30' N/103 degrees 10' E) reveal long distance disjunctions of birch-willow forests as well as a number of herbaceous forest plants. Thus the question arises as to whether long-distance dispersal or fragmentation, following climatic changes and human interference, are more plausible explanations for such a pattern. Analysis of current plant distribution patterns lead to conclusions which are corroborated by zoological surveys of the Gobi Altay: During the Holocene, dark taiga forests apparently existed approximately 600 km to the southeast of their present range, and pollen analysis and charcoal remains provide evidence of a forest decline during the Subboreal time period. The presence of humans during these environmental changes is highly probable as pollen indicating human presence was found. Thus, it is assumed that humans at least contributed to the subboreal forest decline and the spreading of sagebrush and pastures. Moreover we cannot rule out with certainty that disjunctions of forest flora between the Gobi Allay and the forests of north-eastern Tibet are indicative of migration through the present North China desert, as forests may have partly replaced deserts during the moister periods of the Holocene. This multidisciplinary approach implies a mid-Holocene and subboreal scenario, which is new for Central Asia and more in accordance with the environmental history of the Holocene in the western desert belt of the Old World. (c) 2007 Elsevier B.V. All rights reserved.