Holocene environmental change inferred from a high-resolution pollen record, Lake Zhuyeze, arid China

A high-resolution pollen record, c. 50 yr/sample, from terminal lake sediments in the Shiyang River drainage basin on the present margin of the summer monsoon was used to reconstruct vegetation and climate history during the Holocene. Forest trees from mountainous areas of the drainage, including Sabina, Picea and Pinus, dominated pollen assemblages in the early Holocene (11.6-7.1 cal. ka). In the mid-Holocene (7.1-3.8 cal. ka) desert and steppe shrubs and herbs around the lake, including Nitraria, Poaceae, Compositae and Artemisia, were dominant. The late Holocene (3.8-0 cal. ka) was again dominated by alternation of Pinus-Sabina tree pollen and desert-steppe pollen. The early Holocene forest expansion in the mountains and subsequent increase in the river transport of tree pollen corresponds with maximum precipitation during the East Asian summer monsoon maximum. The timing of these changes in our record from arid China is different from that of East China, where the Holocene monsoon maximum appeared in the middle Holocene. This difference indicates that the extent and development of summer monsoon circulation in the Holocene was complex. Changes in the pollen record appear to show pervasive and persistent centennial- to millennial-scale oscillations throughout both wet and dry periods of the Holocene. Our results imply the continental interior was sensitive to changing moisture conditions and responsive to Holocene climatic events.