基于孢粉的新疆全新世植被重建

本文选择我国干旱的新疆地区为研究区域,运用全球植物功能型分类系统(PFTS)、生物群区化定量技术(Biomisation)和600个地层孢粉样品,重建全新世14个时段的生物群区。以20世纪80年代以来采集的地层孢粉原始记录进行收集、归并和统计分析(主要包括孢粉类群、样品百分比数据、测年记录和与地理坐标有关的信息等),同时利用Digitizer图像数字化软件恢复少数已发表的孢粉学文献的孢粉图式,获得建立孢粉数据库需要的相关数据信息,最终建立起新疆全新世孢粉数据库,共获取29个地层孢粉样点的600个样品,设计了54种新疆植物功能型和13种新疆生物群区类型。共重建出7种生物群区类型: 荒漠草原(DEST)、灌木荒漠(DSDE)、平原草甸(PLME)、草原(STEP)、针阔混合林(NBMX)、山地草甸(MOME)和常绿针叶林(EVNF)。从重建结果看,整个全新世,新疆平原地区一直处于温带干旱、半干旱气候条件控制之下,植被以荒漠、荒漠草原和草原为主,在相对湿润时期,如1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P. ,6000aB.P.和10000aB.P.等时段,植被多以荒漠草原或草原类型出现; 在更加干旱时期,如500aB.P.,2000aB.P.,3000aB.P. ,4000aB.P. ,7000aB.P. ,8000aB.P. ,9000aB.P.和11000aB.P.等时段,植被多以荒漠类型出现。新疆的山地植被随气候波动及冰期、间冰期的交替,森林界线上下移动。在冷期(1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P. ,6000aB.P.和10000aB.P.),由于山地冰川扩大,气温降低,森林线下移,而海拔太低处又缺乏森林生长的足够湿度,因此森林带变窄,原来森林带的一部分被寒冷类型的草原代替; 在暖期(500aB.P. ,2000aB.P. ,3000aB.P. ,4000aB.P. ,7000aB.P. ,8000aB.P. ,9000aB.P.和11000aB.P.),气温升高,森林线上移,森林扩展。植被对应于气候变化最敏感的是在平原区,尤其是以荒漠、荒漠草原以及草原的演替更为明显。在平原区荒漠广泛发育的干旱期,如500aB.P.,2000aB.P.,3000aB.P. ,4000aB.P. ,7000aB.P.,8000aB.P.,9000aB.P.和11000aB.P.等时段基本上气候相对温暖; 在平原区荒漠草原和草原广泛发育的相对湿润期,如1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P.,6000aB.P.和10000aB.P.等时段,则基本上处于相对较冷的气候条件下。

POLLEN-BASED RECONSTRUCTION OF VEGETATION IN XINJIANG DURING THE HOLOCENE

The global change research needs to describe the past vegetation condition of Earth system.It's very important for the reconstruction of vegetation regarding to the relation between vegetation and climate and the quantitative investigation of climate system.Arid region is a sensitive area to global change and its sediment has high-resolution record of the information of climate evolution,which is an ideal place for studying the evolution of palaeoclimate and palaeoenvironment.This paper chose Xinjiang as the study area to reconstruct 14 time intervals biomes,based on a global classification system of plant functional types(PFTs),a numerical technique for biome assignment(biomisation)and a total of 600 fossil pollen records.All fossil pollen records in Xinjiang during the Holocene were collected and statistically analyzed,including pollen types,pollen grain percentage,radiacarbon dating and geographic coordinates.Some of the pollen records were digitized from published pollen diagrams using the Digitizer software.A Holocene pollen database of Xinjiang based on 29 fossil pollen sampling sites(600 samples)was finally built.54 plant functional types and 13 biomes in Xinjiang were then set up.Seven biomes were reconstructed: desert steppe(DEST),drought-tolerant shrub and sub-shrub desert(DSDE),plain meadow(PLME),steppe(STEP),needle-leaved and broad-leaved mixed forest(NBMX),mountain meadow(MOME)and evergreen needle-leaved forest(ENVF).Based on the vegetation reconstruction,it can be concluded: The plains of Xinjiang have been under the control of temperate arid and semi-arid climate throughout the Holocene and vegetation was dominated by desert,desert steppe and steppe.Vegetation was dominated by steppe or desert steppe in the relatively wet periods such as 1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P. ,6000aB.P. and 10000aB.P.; while by desert in the relatively arid periods such as 500aB.P.,2000aB.P.,3000aB.P. ,4000aB.P. ,7000aB.P. ,8000aB.P. ,9000aB.P.,and 11000aB.P.The mountain vegetation changed with the climate fluctuation and the forest boundary moved up and down.During the cold period(1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P. ,6000aB.P. and 10000aB.P.),the forest boundary moved down and the forest belt change was narrow because of the mountain glacier expansion and temperature decrease but low-altitude place lacked of enough humidity for forest growing; during the warm period(500aB.P. ,2000aB.P. ,3000aB.P. ,4000aB.P. ,7000aB.P. ,8000aB.P. ,9000aB.P. and 11000aB.P.),the forest boundary moved up and forest belt expanded because of the temperature increase and narrow mountain glacier change.The most sensitive area of vegetation corresponding to climate changes is the plains,the succession of desert,desert steppe and steppe is very obvious in plain area.The climate was relatively warm and desert was widely developed in the arid periods such as 500aB.P.,2000aB.P.,3000aB.P. ,4000aB.P. , 7000aB.P. ,8000aB.P. , 9000aB.P. and 11000aB.P.; it was relatively cold and steppe and desert steppe was widely developed in the relatively wet periods such as 1000aB.P. ,1500aB.P. ,2500aB.P. ,5000aB.P. ,6000aB.P. and 10000aB.P.