Fluctuation of Picea timber-line and paleo-environment on the northern slope of Tian-shan Mountains during the late Holocene

摘要

As a good indicator of Holocene climate, the fluctuation of alpine timberline is a synthetical result of impacts of many environmental factors during geological and historical periods and modern times. As the dominant tree species of mountainous conifer forests on the northern slope of Tianshan Mountains in Xinjiang, the distribution of Picea schrenkiana and its population size are sensitive to climatic change. The typical natural profile of Huashuwozi and the nearby Xiaoxigou archaeological profile,located in Quanzijie Township, Jimusaer County in Xinjiang, were chosen to analyze and compare the relative high-resolution pollen records, and to measure ~(14)C dating and SEM (scanning electron microscope) microstructure for charcoal fragments contained in Xiaoxigou profile's cultural layers. The results show that in these two profiles, the high percentages of Picea (more than 20% and 35%, respectively) appeared in the stratum of the same period (2000—1300 a BP), which corresponds to the charcoal fragment's age of Picea schrenkiana contained in Xiaoxigou cultural layers. These results convincingly revealed that during the period of 2000 — 1300 a BP, the timberline for Picea schrenkiana on the northern slope of Tianshan Mountains in Xinjiang declined by about 330m compared with the present.