The Last Glacial Maximum (LGM) was the coldest period during the previous 20,000 years.There have been different points of views on steppe distribution during the LGM period in southern China,partly due to the differe...The Last Glacial Maximum (LGM) was the coldest period during the previous 20,000 years.There have been different points of views on steppe distribution during the LGM period in southern China,partly due to the different interpretations of Artemisia occurrences.To make a reliable interpretation of the pollen fossil Artemisia,the modern distribution of Artemisia species and the relationship of pollen with climate and vegetation over a large spatial scale in China was thoroughly analyzed.Information about Artemisia species and pollen distributions used in this paper were collected from published works completed by other researchers as well as ourselves.The southern limit of steppe vegetation during the LGM period was interpreted from the published contour map of Artemisia pollen percentages during the LGM.Artemisia species in China are mostly distributed either in the horizontally distributed steppe regions or in the vertically distributed desert-steppe in the desert region,which indicates a cold and dry climate.The steppe is a distribution center of Artemisia pollen.Fractions of Artemisia in surface pollen assemblages are lower in both the desert and the temperate forest.Neither high Artemisia species cover nor high percentages of Artemisia pollen were found in the coast areas of China.Twenty-five percent of Artemisia pollen in sediments might indicate a local occurrence of steppe vegetation.Percentages of Artemisia pollen in the subtropical and tropical forest are less than 10%.A close relationship between Artemisia pollen and temperate steppe in China is demonstrated.The southern edge of the steppe vegetation during the LGM might be along the middle reach of the Yangtze River.Our results support the hypothesis that the isolated high fraction of Artemisia pollen along the northern edge of the South China Sea was transported from a large source area.展开更多
Pollen analysis of 23 surface samples in the east of Qaidam Basin reveals the characteristics of pollen assemblages and their relationships with vegetation and climate. In pollen assemblages, Chenopodiaceae and Artemi...Pollen analysis of 23 surface samples in the east of Qaidam Basin reveals the characteristics of pollen assemblages and their relationships with vegetation and climate. In pollen assemblages, Chenopodiaceae and Artemisia are preponderant types in all the samples, and Ephedra, Gramineae and Compositae are common types. The results of DCA （Detrended Correspondance Analysis） and Correlation Analysis show different pollen assemblages indicate different vegetations, coincided with respective vegetation types. A/C （Artemisia/Chenopodiaceae） in the desert can indicate the aridity. Depending on the aridity, the vegetation communities are divided into four groups： severe drought group, moderate drought group, slight drought group and tropophilous group. A/C value is less 0.2 in the severe drought group, 0.2-0.5 in the moderate drought group, 1.63 in the slight drought group and 5.72 slight-wetness group.展开更多
基金supported by National Natural Science Foundation of China Granted Projects(NSFC No.41071124)
文摘The Last Glacial Maximum (LGM) was the coldest period during the previous 20,000 years.There have been different points of views on steppe distribution during the LGM period in southern China,partly due to the different interpretations of Artemisia occurrences.To make a reliable interpretation of the pollen fossil Artemisia,the modern distribution of Artemisia species and the relationship of pollen with climate and vegetation over a large spatial scale in China was thoroughly analyzed.Information about Artemisia species and pollen distributions used in this paper were collected from published works completed by other researchers as well as ourselves.The southern limit of steppe vegetation during the LGM period was interpreted from the published contour map of Artemisia pollen percentages during the LGM.Artemisia species in China are mostly distributed either in the horizontally distributed steppe regions or in the vertically distributed desert-steppe in the desert region,which indicates a cold and dry climate.The steppe is a distribution center of Artemisia pollen.Fractions of Artemisia in surface pollen assemblages are lower in both the desert and the temperate forest.Neither high Artemisia species cover nor high percentages of Artemisia pollen were found in the coast areas of China.Twenty-five percent of Artemisia pollen in sediments might indicate a local occurrence of steppe vegetation.Percentages of Artemisia pollen in the subtropical and tropical forest are less than 10%.A close relationship between Artemisia pollen and temperate steppe in China is demonstrated.The southern edge of the steppe vegetation during the LGM might be along the middle reach of the Yangtze River.Our results support the hypothesis that the isolated high fraction of Artemisia pollen along the northern edge of the South China Sea was transported from a large source area.
基金Scientific research fund of Hebei Normal University, No.L2004B14 National Key Basic Research Program, No.2005CB422005+3 种基金 National Natural Science Foundation of China, No.90202012 No.40171095 Natural Science Foundation of Hebei Province, No.402615 Knowledge Innovation Project of CAS, No.KZCX3-SW-339
文摘Pollen analysis of 23 surface samples in the east of Qaidam Basin reveals the characteristics of pollen assemblages and their relationships with vegetation and climate. In pollen assemblages, Chenopodiaceae and Artemisia are preponderant types in all the samples, and Ephedra, Gramineae and Compositae are common types. The results of DCA （Detrended Correspondance Analysis） and Correlation Analysis show different pollen assemblages indicate different vegetations, coincided with respective vegetation types. A/C （Artemisia/Chenopodiaceae） in the desert can indicate the aridity. Depending on the aridity, the vegetation communities are divided into four groups： severe drought group, moderate drought group, slight drought group and tropophilous group. A/C value is less 0.2 in the severe drought group, 0.2-0.5 in the moderate drought group, 1.63 in the slight drought group and 5.72 slight-wetness group.
