Changes in climate and vegetation of central Guizhou in southwest China since the last glacial reflected by stalagmite records from Yelang Cave

Two stalagmites (6-cm and 18-cm long) from Yelang Cave (26°2'28″N, 105°44'11″E) in central Guizhou of China have been dated by ICP-MS ²³⁰Th/U, ²¹⁰Pb and AMS ¹⁴C dating methods. Low U but high Th contents in the young stalagmites were difficult to apply ²³⁰Th/U dating. Instead, AMS ¹⁴C dating solved the chronological problem of these stalagmites. Both stalagmites had fast growth rates during Holocene Optimum and the last 600years, but absent growth between 4 and 8ka. The δ¹⁸O record of Stalagmite 20120824-13 agrees well with the Dongge δ¹⁸O records on centennial or longer scales, showing dry climates during the Last Glacial Maximum (LGM) and Younger Dryas and wet climates during Holocene Optimum following the solar insolation trend. The summer monsoon strength decreased from 4.12ka to 1.5ka, but increased during the Medieval Warm Period to produce wet climates and abundant vegetation in the study area. The δ¹⁸O record during the last 600years exhibits strongly decadal variations. Twelve light δ¹⁸O excursions on decadal scales during the last 600years can be identified, agreeing with the local Dry-Wet index record. The Pacific Decadal Oscillation (PDO) strongly affects decadal variability of the moisture budget in the study area, with cold PDO (La Niña condition) in favor of stronger EASM and wet climates. The δ¹³C record indicates that natural vegetation in the study area was strongly destroyed by human activity after the reign of Emperor Yong Zheng (AD 1722-1735) of Qing Dynasty. Since then, the karst-desertification in central Guizhou has been strongly developed due to rapidly increased population and land-use.