Record of environmental change by α-cellulose δ ^(13)C of sphagnum peat at Shennongjia,4000―1000 aBP  

作　　者：ZHU Yun1,2,CHEN Ye1,2,ZHAO ZhiJun1,2,XIAO JiaYi1,2,ZHANG MaoHeng1,2,SHU Qiang1,2 & ZHAO HongYan1,2 1 College of Geography Science,Nanjing Normal University,Nanjing 210046,China 2 Jiangsu Key Laboratory of Environmental Change and Ecological Construction,Nanjing 210046,China 

出　　处：《Chinese Science Bulletin》2009年第20期3731-3738,共8页

基　　金：Supported by Program for Changjiang Scholars and Innovative Research Team in University (Grant No. IRT0533);National Natural Science Foundation of China (Grant Nos. 40671193 and 40631003)

摘　　要：The Dajiuhu Basin at Shennongjia,located within typical East Asian Monsoon region,preserves a sub-alpine sphagnum peat deposition in its central area.The topmost 120 cm of the peat covers the last 4000 years according to AMS 14C dating of pollen concentration.Carbon isotope of α-cellulose,extracted from sphagnum peat,provides a quantitative reconstruction of atmospheric relative humidity,based on transfer functions of C3 plants carbon isotopic fractionation equation and the bryophyte photosynthesis CO2 absorption rate equation.δ 13C,TOC and C/N variations reveal that the Dajiuhu area has experienced a long-term tendency to dry during 4000―1000 aBP,with a major transition happening around 3000 aBP.Four relative dry events are identified at 3400―3200,3000―2600,2200―2000 and 1600―1400 aBP,respectively,corresponding to those climate events documented in many global records.Three periodicities,664 a,302 a and 277 a enclosed in the atmospheric humidity of Dajiuhu are correlated to the cycles of solar activities.The weakening of East Asia summer monsoon during this period registered in the Dajiuhu peat is consistent with the synchronous weakening of Indian Monsoon.This trend may be attributed to gradual decrease of Northern Hemispheric summer solar insolation and the consequently southward migration of Intertropical Convergent Zone(ITCZ).The Dajiuhu Basin at Shennongjia, located within typical East Asian Monsoon region, preserves a sub-alpine sphagnum peat deposition in its central area. The topmost 120 cm of the peat covers the last 4000 years according to AMS ^14C dating of pollen concentration. Carbon isotope of a-cellulose, extracted from sphagnum peat, provides a quantitative reconstruction of atmospheric relative humidity, based on transfer functions of C3 plants carbon isotopic fractionation equation and the bryophyte photosynthesis CO2 absorption rate equation. δ^13C, TOC and C/N variations reveal that the Dajiuhu area has experienced a long-term tendency to dry during 4000-1000 aBP, with a major transition happening around 3000 aBP. Four relative dry events are identified at 3400-3200, 3000-2600, 2200-2000 and 1600-1400 aBP, respectively, corresponding to those climate events documented in many global records. Three periodicities, 664 a, 302 a and 277 a enclosed in the atmospheric humidity of Dajiuhu are correlated to the cycles of solar activities. The weakening of East Asia summer monsoon during this period registered in the Dajiuhu peat is consistent with the synchronous weakening of Indian Monsoon. This trend may be attributed to gradual decrease of Northern Hemispheric summer solar insolation and the consequently southward migration of Intertropical Convergent Zone （ITCZ）.

关 键 词：神农架大九湖 泥炭沉积 碳同位素 纤维素 环境变化 泥炭藓泥炭 东亚夏季风 大气相对湿度 

分 类 号：P593[天文地球—地球化学]