Holocene Palaeoenvironment Changes In The Ordos Plateau Recorded By Pollen Of Baahar Nuur Lake

We analysis pollen of 12 samples which are collected from 5 lakes (Qigenuur, Hashu lake, Tengenuur, Hongjian nuur, Taorimu lake) in Inner Mongolia, China. Based on pollen concentrations and pollen percentages we compare lake sediment samples with surface samples, and we find out lake sediment sample is similar with surface sample for the same lake. We preliminarily discussed distribution and representation of some type pollen. As a result, this can provide reference to recover past vegetation and reconstruct past climate by pollen assemblage of lake sediments.Pinus takes on the super deputation in semi-arid area. Appearance of Pinus doesn' t mean that there are Pinus in local area. Pollen assembly can reflect state of local vegetation.Climatic records from different and climatically sensitive regions are needed to understand the large-scale Holocene climate changes. The Ordos plateau is such an area in which the desert-loess margin and agriculture-husbandry transitional zone are situated. This thesis focuses on sections in the Ordos Plateau in attempt to provide more regional Holocene climatic information based on AMS-constrained pollen chrono-sequences obtained from Baahar Nuur lake cores. The following is a brief summary of our reconstructed Holocene climatic and environmental history of the study area. The pollen records from the Baahar nuur lake core suggest 6 stages of climate changes: (1) Cold and dry conditions sustained during 12～10 ka BP. (2) It became warmer with increasing humidity occurred in 10～8.8 ka BP, but climate was unstable. (3) Warm and humid climate dominated during the period of 8.8～4.1 ka BP. (4)Optimal warm and humid climate in 4.1～3.4ka BP. (5) The climate became drier and cooler in 3.4～2.7 ka BP. (6) The climate continued to become drier and cooler from 2.7 ka BP.The variety of solor radiation is the main factor that can lead to the change of climate. The solor radiation of summer monsoon plays dominant role on the variety of precipitation of Ordos plateau. The amount of precipitation from summer monsoon and effective humidity which is concerned with precipitation and temperature can influence ecological environment much more than temperature.