Asynchronous variations of East Asian summer monsoon, vegetation and soil formation at Yulin (North China) in the Holocene

Abstract

In the East Asian monsoon region, Chinese speleothem δ 18 O records exhibit a maximum monsoon strength during the early Holocene. However, other proxy data from lakes or loess, interpreted as monsoon rainfall, show a mid-Holocene monsoon optimum. This discrepancy may come from specific climate interpretation of different proxies. Here we report multiproxy records from a single loess-palaeosol sequence at Yulin in the monsoon marginal northern China, based on an independent and high-precision chronology. Our long-chain n-alkane δD values, together with related biomarker proxies including the average chain length and concentration of long-chain n-alkanes, reveal a weakening trend in monsoon strength and less woody vegetation since ~6 ka. However, other soil formation-related proxies, such as magnetic susceptibility, grain-size distribution and total organic carbon, show a decreasing trend since 4-3 ka. We find that monsoon and vegetation are controlled by insolation variation, while soil formation is more related to temperature and humidity changes. Our multiple proxy comparison reveals different controlling mechanisms leading to different interpretations in monsoon, vegetation and soil formation reconstructions. This finding suggests that previous debates on Holocene monsoon changes in East Asia probably stem from the specific proxy interpretation.

Hydroclimatic changes on multiple timescales since 7800 y BP in the winter precipitation–dominated Central Asia

“…Decreasing summer temperature during the Holocene would have decreased the effective evaporation and improved the soil moisture availability. Together with the increasing winter temperature, it could enhance vegetation and soil development during the growing season ( 56 ) in the late Holocene, and control the soil-related proxy changes, such as δ 13 C org and magnetic susceptibility. In contrast, higher summer temperatures and lower winter temperatures during the middle Holocene could suppress soil moisture and vegetation development in WCA, even if the precipitation in WCA was higher during this period than in the late Holocene.…”

Anthropogenic Influences on Soil Erosion since the Late Holocene and Contrasting Regional Sustainability in China

“…The magnitude of paleoclimatic change is small at 4-1.5 ka but large since 1.5 ka. A recent study on Holocene loess at Yulin, a transitional zone between the CLP and Mu Us Desert, reveals asynchronous variations of East Asian summer monsoon, vegetation, and soil formation, which are ascribed to the differences in respective controlling factors [63]. It is exhibited that soil-formation-related proxies, such as magnetic susceptibility and grain size, could be inconsistent with monsoon strength.…”