岩溶区不同植被下土壤水溶解无机碳含量及其稳定碳同位素组成特征  

Characteristics of concentrations and carbon isotope compositions of dissolved inorganic carbon in soil water under varying vegetations in karst watershed

作　　者：梁轩[1] 汪智军[1] 袁道先[1,2] 杨平恒[1] 贺秋芳[1] 

机构地区：[1]西南大学地理科学学院/三峡库区生态环境教育部重点实验室,重庆400715 [2]中国地质科学院岩溶地质研究所/国土资源部岩溶动力学重点实验室,桂林541004

出　　处：《生态学报》2013年第10期3031-3038,共8页Acta Ecologica Sinica

基　　金：国家自然科学基金项目(41072192;41103068);重庆市科委项目(CSTC;2010BC7004);重庆市国土房管局科技项目;西南大学博士基金(SWU111009);岩溶动力学重点实验室开放基金资助项目(KDL01-2010)

摘　　要：自2010年7月至2011年7月对重庆青木关岩溶区典型植被下的土壤水进行了月动态取样,分析了土壤水溶解无机碳含量(DIC浓度)及其稳定碳同位素组成(δ13CDIC值)的时空变化特征,以揭示岩溶土壤系统碳酸盐岩溶蚀作用及其碳汇效应。研究结果表明:草地和针叶林地土壤水的DIC浓度和δ13CDIC值相对较低,分别为59.12 mg/L和-17.22‰,31.47 mg/L和-16.37‰;而旱地、灌丛地、退耕还林地土壤水具有较高的DIC浓度和δ13CDIC值,分别达153.88 mg/L和-12.2‰,221.82 mg/L和-11.9‰,97.30 mg/L和-11.23‰,其中灌丛和退耕还林地的δ13CDIC值与DIC浓度呈正比,且雨季较旱季偏高约4‰—5‰。根据δ13CDIC值,结合各植被类型下土壤水DIC浓度与其相应的土壤碳酸盐含量呈正相关,判断旱地、灌丛地、退耕还林地等岩溶土壤水中的DIC主要来自土壤中碳酸盐岩矿物的碳酸溶蚀,即岩溶土壤中存在着碳酸盐岩碳酸溶蚀作用,从而在一定程度上减少了土壤系统向大气排放的CO2量。Carbon plays a vital role in karst ecosystem. A proportion of carbon dioxide produced by microbial activities and respiration of roots can be dissolved and carried by the infiltration water and then dissolve carbonate materials in the karst soil system. This process can produce a lot of dissolved inorganic carbon （DIC） into the soil water and groundwater. The stable carbon composition of DIC （δ^13 C_DIC） can be used as a tracer for studying biogeochemical processes in soil water because the potential biogenic, atmospheric and geologic sources of C have distinct δ^13C signatures. In order to reveal the characteristics of temporal and spatial variations of DIC fluxes, which can help us to get an insight into the carbonate dissolution and its related carbon cycling, and evaluate the carbon isotopic evolution of soil water in karst areas, soil water derived from diffe rent vegetations in Qingmuguan karst areas, Chongqing, SW China, were collected monthly from July,2010 to July, 2011, and the DIC concentrations and δ^13C_DIC values of soil water were analyzed. The results show that： （ 1 ） DIC concentrations and δ^13C_DIC of soil water showed distinct temporal and spatial variations in the study area. DIC concentrations and δ^13C_DIC values of soil water varied from 21.56 mg/L to 265.35 mg/L, and from -7.73‰ to -20.68‰, respectively. （2） Soil water derived from grass and coniferous forest land had lower DIC concentrations and δ^13 C_DIC values, with a mean value of 59.12 mg/L and -17.22‰, 31.47 mg/L and -16.37‰ respectively. The δ^13C_IC indicated that these DIC were mainly derived from the dissolution of soil CO2. （3） Soil water derived from the dry land, shrub land and afforestation land had higher DIC concentrations and δ^13C_DIC values, with the averages of 153.88 mg/L and -12.2‰, 221.82 mg/L and -11.9‰, 97.30 mg/L and -11.23‰, respectively. Meanwhile, these δ^13 C_DIC values of soil water were generally 4‰--5‰ higher in the rainy season than those in the dry season.

关 键 词：青木关岩溶区 土壤水 溶解无机碳(DIC) 稳定碳同位素组成 

分 类 号：S153.6[农业科学—土壤学]