Mapping Holocene pollen data and vegetation of China

Abstract

Holocene pollen maps of China north of the Yangtze River are presented for six time slices at 2000 year intervals and for ten taxa or taxon combinations on the basis of a data set of pollen diagrams of 142 sites. In spite of the problems with the differentiated data quality, a general correspondence of modern pollen maps with actual vegetation distribution justifies the feasibility of using the pollen maps to illustrate the past temporal and spatial patterns of vegetation change and to tentatively reconstruct palaeo-biomes for the specific time slices. The pollen maps reveal large changes in Holocene vegetation. In the southeastern half of the study area, arboreal taxa generally expanded in the early Holocene times, reaching their maximum at 6 or 4 ka BP, and then shrank during the late Holocene. An exception was found for eastern and northern Northeast China where the maximum development of arboreal taxa occurred during the last 4000 or 2000 years. The evident drop in AP percentages, and therefore the decline of forests, occurred after 6 ka BP in the most southeastern regions, especially in the middle and lower reaches of the Yellow River, and may have been caused by the expansion of farming since the Yangshao Culture period. The reconstructed biomes enable the visual expression of palaeo-vegetation change. A relatively open forest with Pinus as its dominant component developed in the southeastern Loess Plateau and western North China Plain from 8 to 6 ka BP, but it came to an end at about 4 ka BP. On the other hand, cold temperate conifer forest, and temperate mixed conifer and deciduous forest in Northeast China did not yet exist between 10 and 6 ka BP. They appeared at 4 ka BP and then continued to develop through time. Warm temperate deciduous forest experienced a remarkable reduction during the last 6000 years. Alpine valley Picea/ Abies forest in the eastern Qinghai-Tibet Plateau developed in the early and mid Holocene, but started to decline at 4 ka BP, and has almost disappeared today.