• 责任者：Zhang Xiao (Key Laboratory of Western China’s Environment Systems ; Ministry of Education ; Lanzhou University ; Lanzhou 730000 ; China) ; Jia Xin
• 刊名：Quaternary Sciences
• 出版年：2013
• 卷期：33(1)
• 关键词：全新世 ; Holocene ; 末次冰期 ; last glacial age ; 碳同位素 ; carbon isotopes ; 黄土高原 ; Loess Plateau
• 页码：p.187-196
• 图表：illus., 1 table, 47 refs.
• 分类号：1400
• issnNo：ISSN1001-7410
• isbnNo：CN11-2708/P

class=MsoNormal style="MARGIN: 0cm 0cm 0pt">ce="Times New Roman">Stable organic carbon isotopic compositioncii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（δce="Times New Roman">13Corg. cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">of more than 10 Chinese Loess profiles have been studied to indicate the relative abundance of C3/C4 plants in the Chinese Loess Plateau cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">CLPcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">since the Last Glacialcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">LGcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> , while only few studies have been conducted in the western part of the CLP cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman"> Longxi Loess Plateaucii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> , and the variations of the relative abundance of C3/C4 plants since the LG in the western CLP has not been well studied.cerun: yes">  Zhang Jiachuan loess profile cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">34cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">°ce="Times New Roman">59cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">＇ce="Times New Roman">N, 106cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">°ce="Times New Roman">15cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">＇ce="Times New Roman">Ecii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> is located in the northwestward of the Zhang Jiachuan county town,the northeastern part of Tianshui City in the south eastern Gansu Province,about 368km away from the provincial capital Lanzhou City. The top part of the profile cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman"> ca. 1 mcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> is disturbed by modern agricultural activities. The stratigraphy of this profile below the top part along the depth is the loess layer of the Late Holocene cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">ca. 0.54mcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> , the Holocene paleosol layercii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman"> ca. 0.54m to 2.70mcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> , and Malan loess layer accumulated during the LG cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">below ca. 2.7mcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">. Totally, 165 loess samples were collected with the density of 2cm per sample from this profile, except the top disturbed part. Four samples for radio-carboncii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">14Ccii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman"> dating were collected from depth of 54cm, 130cm, 190cm and 240cm, and the dating results indicated that the sampled profile do cover the LG and the Holocene periods. Magnetic susceptibility and cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">δce="Times New Roman">13 Crg. of the 165 loess samples have been measured indoor. For cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">δce="Times New Roman">13Corg. , the results of the standard materialscii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman"> n = 15 cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">demonstrated that the standard deviation of the instrumental measurement is cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">≤±ce="Times New Roman">0. 1cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">‰ce="Times New Roman"> cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman">VPDBcii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">.cerun: yes">  The obtained cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">δce="Times New Roman">13Corg. values from Zhang Jiachuan profile are ranged from -21.5cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">‰ce="Times New Roman"> to -23.4cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">‰ce="Times New Roman"> with an average value of -22.6cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">‰ce="Times New Roman">. The cii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">δce="Times New Roman">13Corg. values of the paleosol developed during Holocene is more positive than those of the loess accumulated during the LG, indicating that C4 plants relative abundance was increased from the LG to the Holocene in the study site which is similar to the results from the eastern CLP.cerun: yes">  Furthermore,the comparison between our results and several other soil organic carbon isotopic recordscii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">（ce="Times New Roman"> Huan Xian,Hong Jusi,Ba Xie,Jing Yuan and Yuan Baocii-font-family: ’Times New Roman’; mso-hansi-font-family: ’Times New Roman’">）ce="Times New Roman">reveals that the variations of the relative abundance of CJC4 plants in the Longxi Loess Plateau since the LG is more complex than that in the eastern CLP. Our δ13Corg. results is consistent with that from Yuan Bao profile located in southwestern part of the Longxi Loess Plateau, while opposite to that from Jing Yuan profile with more negative values occurred in the Holocene paleosol located in the northern part of the Longxi Loess Plateau,which indicate that there still has some internal differences in C3/C4 variations between different parts in the Longxi Loess Plateau. It seems the relative abundance of the C4 plants increased from the LG to the Holocene in the southeastern and southwestern part of the Longxi Loess Plateau. However,in the northern part of the Longxi Loess Plateau,it seems that this area was predominated by C3 plants not only during the LG, but also during the Holocene.cerun: yes">  Many studies on carbon isotopic composition of modern C3 plants and its relationship conditions clearly demonstrated that there is a consistent negative correlation between carbon iso with environmental topes of modern C3 plants and the amount of precipitation. If so, the organic carbon isotopes derived from vegetation composed of C3 plants or predominated by C3 plants should be a potential indicator of paleo-precipitation. Therefore, soil organic carbon isotopes from the Longxi Loess Plateau, especially from the northern part of the Longxi Loess Plateau, has great potential in paleoclimatic studies that means the study reinforced. on soil organic carbon isotopes in this region should be.