基于有壳变形虫的大兴安岭洛古河泥炭沼泽古水位定量重建

THE QUANTITATIVE RECONSTRUCTION OF THE PALEO-WATER TABLE OF LUOGUHE PEATLAND IN DAXING＇ANLING MOUNTAINS BASED ON TESTATE AMOEBAE ASSEMBLAGES

对采自大兴安岭北部洛古河泥炭地表层49cm泥炭剖面，基于137Cs法建立剖面年代框架，利用有壳变形虫指标，借助转换函数法定量重建过去近100年来的水位变化。具体可划分为3个阶段：1）1918~1951年泥炭地非常湿润，有壳变形虫以喜湿物种为主，如茄壳虫未定种（H. sp.）、瓶形梨壳虫（Nebela lageniforms）、齿口阿吉尼亚虫（Argynnia dentistoma）以及Archerella flavum等，缺少干燥种，水位埋深自12cm频繁大幅波动升高至23cm；2）1951~1982年仍较湿润，但已呈现变干的趋势，喜湿种类显著减少，以指示较湿润生境的凤蝶茄壳虫（Hyalosphenia papilio）、巧茄壳虫（Hyalosphenia elegans）、染色梨壳虫（Nebela tincta）为主，水位埋深大部分时间保持在22~24cm；3）1982~2013年泥炭地持续变干，指示湿润环境的物种基本消失，苔藓鳞盖虫（Assulina muscorum）、半空鳞盖虫（Assulina seminulum）占优势，指示干燥环境的长圆鳞壳虫（Euglypha rotunda type）、暧昧蛹壳虫（Corythion dubium）丰度增大，水位埋深自24cm持续降低至34cm。洛古河泥炭地持续变干是由于气温升高驱动还是降水减少驱动，或二者都有尚待研究。

Testate amoebae are a group of single-celled protists found in abundance on the surface of peatlands and form a well-preserved shell （test）in Holocene peats. They have been routinely used as proxy for hydrological changes in boreal, suboreal and temperate peatlands in Europe and North America. However, the potential of testate amoebae for peatland palaeohydrological reconstruction has not been evaluated in Northeast China. In this study, a 49cm long peat core was taken from Luoguhe peatland （53°8＇1.08＂N, 122°3＇30.72＂E; 578m a.s.l.）in Daxing＇anling Mountains in August 2013. The timescale of peat profile was constructed with 137Cs dating method. The basal age was 1918 A.D. by extrapolating from the depth-age model. The paleo-water table was quantitatively reconstructed using testate amoebae-water table transfer function developed from peatlands in Daxing＇anling Mountains. The significance test of the reconstruction was carried out with a R package and palaeoSig. The results showed that the reconstruction based on WAPLS model was significant. There was a clear trend that Luoguhe peatland was becoming drier during the last 100 years. The history of Luoguhe peatland water table changes can be divided into three phases：1）It was wet from 1918 to 1951A.D.. The testate amoebae assemblage was dominated by very wet taxa such as Hyalosphenia sp., Nebela lageniform, Argynnia dentistoma and Archerella flavum. The dry taxa were absent in this period. The depth to water table （DWT） was fluctuating frequently and substantial from 12cm to 23cm; 2）During 1951~1982A.D., the peatland was moderately wet. The trend of becoming dry was apparent. The testate amoebae assemblage was dominated by some relative wet taxa such as Hyalosphenia papilio, Hyalosphenia elegans, Nebela tincta, while the abundance of very wet taxa decreased. The DWT kept at 22~24 cm in most time of this period; 3）The DWT gradually increased from 24cm to 34cm during 1982~2013 A.D.. The testate amoebae assemblage was dominated by relative dry taxa, Assulina muscorum, Assulina seminulum, and the abundance of dry taxa Euglypha rotunda type and Corythion dubium gradually increased. It is required further study to explore whether the Luoguhe peatland was becoming dry during the last 100 years driven by increasing temperature or by decreasing precipitation, or both of them.