桂林岩溶土壤和植被的稳定碳同位素组成及季节性变化特征

【目的】以桂林岩溶土壤为例,通过长期监测岩溶土壤及植被有机碳的δ13C值,研究其稳定碳同位素组成及季节性变化特征,为我国南方岩溶地区碳循环途径提供科学依据。【方法】选择3个试验点,定期采集土壤及优势种植被黄荆和檵木样品,测定有机碳含量和δ13C值。【结果】土壤有机碳的δ13C值具有明显的季节性变化特征,范围在-27.50‰～-17.92‰;优势种黄荆和檵木其各部位有机质的平均δ13C值范围为-28.23‰～-25.15‰,而土壤中有机碳的δ13C值范围为-22.32‰～-19.00‰;土壤有机碳的含量表现为洼地灌木丛〉坡地灌木丛〉洼地灌草丛,且都为表层土（0～5cm）〉深层土（10～20cm）。【结论】土壤有机碳的δ13C值变幅较大,但坡地灌木丛、洼地灌木丛和洼地灌草丛三者的变化规律并不一致;总体上土壤δ13C值随土层深度的增加而逐渐减小,表明土壤有机碳的δ13C值明显高于当地植被有机碳的δ13C值。

Stable carbon isotopic composition and seasonal varying characteristics of karst soil and vegetation in Guilin

Objective Using the karst soil in Guilin as the example, δ13C value of organic carbon in karst soil and vegetation was monitored for a long time to study the stable carbon isotopic composition and seasonal varying characteristics so as to provide scientific references for carbon cycle pathway in karst regions of South China. Method Dominant plants including Vitex negundo and Loropetalum chinense and soil were sampled regularly to detect organic carbon content and δ13C value. Result The δ13C value of soil organic carbon obviously changed in different seasons with the range of -27.50‰ to-17.92‰. The average δ13C value range in each organ of Vitex negundo and Loropetalum chinense was 28.23‰ to -25.15‰. The δ13C value of soil organic carbon ranged from-22.32‰ to -19.00‰ . The sequence of soil organic carbon content was karst depression busheskarst slop busheskarst depression irrigation grass,and surface soil（0-5cm） deeper soil（10-20 cm）. Conclusion The amplitude change of soil organic carbon δ13C was larger,but the change rule of slope,depression and grassland was inconsistent. From surface to the downward,the soil δ13C value decreased with the increase of soil depth on the whole,indicating that the δ13C value of soil organic carbon was obviously higher than that of local plants.