中文摘要：

为促进目前岩溶碳汇稳定性和速率等科学问题的深入研究,在分析桂林会仙岩溶湿地主要水生植物碳同位素的基础上,利用基于碳酸酐酶活性与植物碳同位素值显著正相关的二端元模型,估算了不同植物利用光合作用固定HCO3-的比例.结果表明,湿地核心区沉水植物光合作用固定HCO3碳量在4.86～64.73tC/（a·km2）之间,挺水植物为15.68～453.0] tC/（a·km2）,平均值为76.74 tC/（a·km2）.按平均值计算会仙湿地水生植物光合作用固定HCO3碳量为4 466.27 tC/a,即在会仙湿地岩溶地下河补给的HCO3中约47％被水生植物光合作用固定.水生植物光合作用固碳效果明显,是碳汇研究中不容忽视的一个十分重要的问题.

英文摘要：

Currently,the stability and the velocity of karst carbon sink are two major scientific questions urgently need to be answered.Characteristics of δ13C in major aquatic vegetations in the Huixian karst wetland are discussed in this paper,and the percentages of photosynthetic carbon fixation are estimated by means of double-meta model in which remarkable positive relationship is presented between carbonate anhydrase activity and the value of plant carbon isotope.The Huixian karst wetland,located in Huixian town,Lingui county and 30 km away from Guilin city,is the largest natural wetland in low-altitude area of subtropical zone of China.The wetland is mainly sourced by karst groundwater.To understand the characteristics of δ3C value in different aquatic plants,aquatic plant sampling is conducted on 10-12,August,2011,and 17 aquatic plants are collected in the core zone of this karst groundwater-fed wetland and their δ13C are analyzed.The δ13C values varied from-30.08 ‰ to-18.91‰ with an average of-26.65 ‰,in which the maximum is in watermifoil and the minimum is in scripus triqueter.The mean δ13C values of various plants in descending order are-23.91‰ （submerged plant）,-27.49 ‰ （hydrophyte）,-28.66 ‰ （emergent plant）,-28.78 ‰ （floating plant） respectively.The results show that the values of HCO3-carbon sequestration range from 4.86 to 64.73 tC/（a · km2） for submerged plants and from 15.68 to 453.01 tC/（a · km2） for emerged plants respectively in the core zone of the wetland with a mean value of 76.74 tC/（a · km2）.Furthermore,the fixed HCO3-carbon consumed by photosynthesis is estimated to be 4 466.27 tC/a using this mean value,i.e.,approximately 47 ％ of HCO3-fed by karst underground streams are consumed by aquatic vegetation photosynthesis in the wetland.Remarkable effect of carbon fixation by aquatic plant shows that the photosynthesis of aquatic plants can not be neglected in karst carbon sink study,especially for net carbon sink estimation in karst region.