The vegetation and monsoon variations at the desert-boess transition belt at Midiwan in northern China for the last 13 ka

Abstract

Fine-resolution palaeovegetation and palaeomonsoon proxies for the last 13 ka have been established at the desert-loess transition belt in northern China. These are based on pollen, organic carbon and δ13C analysis of samples from a peat section at Midiwan. Results show that the palaeovegetation underwent nine major changes: desert-grassland, grassland, semi-desert, humid grassland, desert, sparse-wood-grassland, steppe, humid grassland and desert-grassland. An interval with semi-desert, humid grassland and desert is associated with rapid oscillation events of cold-dry conditions (11200-10600 14C yr BP) to cool-humid conditions (10600-10200 14C yr BP), followed by a change to a cold-dry climate (10200-10000 14C yr BP). The Holocene optimum (10000-7500 14C yr BP) and another humid interval (4500-3500 14C yr BP) have also been detected in the area. During the last 3000 years, dry conditions have prevailed and human impact may have affected the location of desert-loess transition zone. The record therefore shows a sensitive response to climate on sub-Milankovitch timescales, and this suggests that possible forcing factors linked to processes in the north Atlantic and their influence on the Northern Hemisphere Westerlies, and the South China Sea and its influence on Summer Monsoon precipitation, have been important controls on climates and human activity in eastern Asia.