Holocene Environment Changes Inferred From The Plant Macrofossil Records From The Peatlands In The Altai Mountains, Xinjiang

As the nearest warm period from the modern world, lloloccnc climate process could provide information to our understanding of past and future climate change, which made the Holocene climate to be a focus in the field of global change. The dry lands of northern and western China are an important part of the northern hemisphere’s arid belt, and its ecological environment is very sensitive to climate change. Hence, it is vital to study Holocene climate change histories in this region.Here, we present a well dated and high-resolution loss-on-ignition peat properly and plant macrofossil record from ATM10-C4(650cm) in the Altai Mountains in order to study Holocene vegetation and environment changes in this region. Loss-on-ignition (LOI) is measured for I cm intervals and plant macrofossil is analyzed for8cm intervals. Then. bog surface wetness (BSW) is reconstructed on the basic of plant macrofossil data. All19dating samples are measured by AMS14C. terrestrial plant macrofossil arc picked out for dating. The core covers the whole Holocene period.Organic matters and dry bulk density are obtained from LOI measurements. High organic matter and low dry bulk density usually indicate a warm climate, and low organic matter and high dry bulk density demonstrate a relatively dry condition. Organic matter together with dry bulk density values of this core indicates a dry early Holocene. a humid mid Holocene and a gradually drying late Holocene.Plant macrofossil results of ATM10-C4show four different stages:from11.1-8.1cal ka BP, the macrofossil are mainly composed of Cyperaceae (39.71%); from8.1-4.6cal ka BP, the mean value of Cyperaceae plant macrofossil reaches48.55%and mossl gets its highest value for about7%; from4.6-2.9cal ka BP, Cyperaceae decreases to31.92%and Sphanuml reaches to50.27%which is the highest in the whole periods; and after2.9cal ka BP, Cyperaceae increases to50%but Sphagnuml decreases less than6%.Detrended correspondence analysis (DCA) is used to distinguish different plant species. DCA result displays that moss and Sphagnum are located at the opposite ends of the first axis, which illustrate that DCA axisl is sorted by humidity. At the same time, bog surface wetness is reconstructed using DCA axisl scores.Plant macrofossil records from ATM10-C4indicate Holocenc environmental changes in Altai Mountains. The results show that Altai Mountains experienced a dry early Holocenc (11.1-8.1cal ka BP). a wetter early to mid-Holoccne (8.1-4.6cal ka BP). and a relatively dry mid-llolocene to late Holocene (after4.6cal ka BP). From4.6to2.9cal ka BP, the climate was driest in the whole Holocene periods, but the climate conditions became slightly moister after2.9cal ka BP.Ilolocene climate and environment changes inferred from plant macrofossil show the same history as indicated by pollen. Both suggest a dry early Holocene. a wet mid Holocene and a relatively dry late Holocene. However, there exist centennial scale fluctuations. Multiple proxies from Ulungur Lake, Manas Lake, Ebinur Lake and Hoton-Nur Lake in nearby Altai regions arc contrasted and found that these lakes displayed similar climate patters as the same as our plant macrofossil results from the Altai Mountains. Overall, plant macro fossils could be used as a reliable proxy in palcoclimate reconstruction. Holocenc environment change in Altai regions may be influenced together by sea-surface temperature change in North Atlantic Ocean, mid-latitude Westerlies, insolation the Northern Hemisphere and the reaction of Altai Mountains to climate change and so onof.