Holocene vegetation and climate changes in Hoton‐Nur basin, northwest Mongolia

Abstract

Radiocarbon‐dated pollen and diatom records from Hoton‐Nur lake (48°40'N, 88°18'E), northwest Mongolia are used to reconstruct Holocene vegetation and climate changes. Steppe, which covered the area some time before 9000 BP (all ages are given in 14 C BP), was replaced by boreal conifer forest‐steppe by 9000–8500 BP. At the same time, planktonic diatoms increased in abundance from 5 to 45%. After 4000 BP there was a sharp reduction in forest and re‐establishment of steppe. Changes in the pollen composition were accompanied by a decrease in the abundance of planktonic diatoms from 35–50% (between 9000 and 5500 BP) to less than 10% soon after 4000 BP. These and other published data from Mongolia suggest wetter conditions during the early and middle Holocene than those of today. This pattern probably reflects an expansion of the Pacific monsoon recorded in geological data from China and simulated in climate‐model experiments, and suggests that the summer monsoon influenced a larger area than might appear if the Chinese records only are taken into consideration.