摘要
根据长江口崇明东滩典型高程部位柱状样与鼎湖山不同海拔土壤剖面土壤有机碳(SOC)含量与SOC同位素资料(δ13C、Δ14C),研究了土壤有机质更新的元素与同位素特征。结果表明,土壤剖面δ13C最大值(δ13Cmax)深度以上土层的SOC含量与δ13C值呈负相关,该深度以下呈正相关。土壤SOC含量与δ13C呈负相关,说明有机质分解程度低,有机质中快循环组分的比例较高,为土壤表层新鲜有机质,有机质14C表观年龄不足200年;二者呈正相关指示有机质分解程度较高,为中、下部土层较稳定的有机质组分,成土年龄在300年以上。土壤SOC含量随时间下降的速率与成土时间呈负相关,δ13Cmax深度以下土层的下降速率明显低于该深度以上土层,且年代越老,SOC含量下降速率越慢,表明其有机质主要为慢循环组分。不同土壤剖面δ13C的时间趋势基本一致,在δ13Cmax深度以上土层,δ13C随时间延长而增大,该深度以下δ13C随时间延长而降低。土壤有机碳δ13C与SOC含量随时间的变化具有明显对应关系,表明二者的变化机制存在内在关联。
Based on the data of soil organic carbon （SOC） content and its isotopic compositions （δ^13C and Δ^14C ） in three drilling cores at typical elevations at the Chongmingdongtan salt marsh of Yangtze River Estuary and in six profiles at different altitudes in the Dinghushan Biosphere Reserve, the characteristics of SOC content and its isotopic compositions during the turnover of soil organic matter （SOM） were investigated. The results indicated that SOC contents and δ^13C values were negatively correlated in the soil sections above the depth with maximum δ^13C （δ^13 Cmax）, and positively correlated below this depth. The negative correlation indicated that SOM reduction degree was low, and the rapid turnover compartments were in greater proportions of SOM which were fresh organic matters in the upper soil sections with SOM apparent ^14C ages less than 200 years. The positive correlation was in adverse, and the SOM apparent ^14C ages were usually over 300 years. The degradation rate of SOC was negatively correlated with pedogenesis ages, and remarkably lower below the soil depth with δ^13Cmax than above the depth. The greater the pedogenesis age, the less the decreasing rate of SOC content with time, suggesting that the SOM was mainly of slow turnover compartments. The temporal changes of δ^13C values in different soil profiles Showed similar tendency, i. e. , the δ^13C values above the soil depth with δ^13Cmax increased with time, while those below this depth were in adverse, which correlated well with the temporal changes of SOC contents, due to the distribution of different SOM compartments with soil depth.
出处
《生态学杂志》
CAS
CSCD
北大核心
2007年第9期1327-1334,共8页
Chinese Journal of Ecology
基金
国家自然科学基金重大项目(39728102)
国家自然科学基金项目(40202032)
中国博士后科学基金
广东省自然科学基金博士启动项目(984105)
中国科学院广州地球化学研究所所长基金资助项目
关键词
土壤有机质
碳循环
同位素示踪
^14C计年
soil organic matter
carbon cycling
isotope tracing
radiocarbon dating.
