Fifty-six surface pollen samples from different vegetation zones in the Yili Basin,western Tianshan Mountains,Xinjiang were analyzed to examine the relationships between the surface pollen assemblages and the original vegetation.A pollen analysis and a vegetation investigation with a discriminant analysis show that the pollen assemblages greatly differ across disparate vegetation zones.Twelve pollen taxa can be used as significant types for vegetation reconstruction in the basin.These taxa were the most abundant in the surface pollen samples.Cupressaceae pollen percentages were greater than 1%in Cupressaceae shrubs.More than5%of Picea pollen indicates the growth of a Picea forest within 5 km.The subalpine meadow that is distributed widely in the basin is characterized by high content of Artemisia,Chenopodiaceae,Poaceae,Picea,Asteraceae,Taraxacum and Arenaria pollen types.The Artemisia-Chenopodiaceae-Poaceae-Cannabaceae pollen assemblages indicate the presence of montane steppe in the area.Artemisia and Chenopodiaceae pollen dominate the desert steppe and Populus forest.Artemisia pollen percentages were greater than 60%in the Artemisia desert,whereas Chenopodiaceae pollen percentages exceeded 65%in the Chenopodiaceae desert.The Artemisia/Chenopodiaceae(A/C)ratios reflect the vertical moisture changes in the Yili Basin.The mean A/C ratios were greater than 1.2 in the subalpine meadow and montane steppe that occupy the humid zone in the basin.These ratios were between1 and 1.2 in the Cupressaceae shrubs,desert steppe,Populus forest and floodplain meadow.The ratios were less than 0.5 in the Chenopodiaceae desert,which is an arid environment.
Global climate change and its possible ecological consequences have become the focused issue(IPCC,2007;Mann et al.,2008;Ding et al.,2009).The Holocene contains the analogous characteristic of future climatic change and the continuous agriculture activity,providing the ideal"similar pattern"for studying the climate change and human adaption and impact in the future.Based on the recent studies of stalagmite,ice core,ocean,and lake etc.,the paper introduces the new progress in the Holocene climate and agriculture research in China as follows:(1)Discuss the variability,amplitude,and unstable characteristic of climate,as well as the abrupt events and mechanisms of climate.(2)Analyze the botanical index records for studying the early agriculture.(3)Review the agricultural origin,expanding,and development.(4)Reveal the style and intensity of early agriculture and understand the agricultural impact and adaption to the environmental changes.(5)Introduce ongoing research projects in China and emphasize the significance of increasing the dating precision and the indicative effectiveness of proxies.(6)Realize how the ecosystem and environmental factors respond to the increasing temperature process,understand how the human adapt to the rapid climate change,and provide the scientific basis for assessing the effects of climate change and the human adaption in the future.
