利用δ^(13)C方法研究添加玉米秸秆下红壤总有机碳和重组有机碳的分解速率

DECOMPOSITION RATES OF ORGANIC CARBON IN WHOLE SOIL AND HEAVY FRACTION OF RED SOIL INCORPORATED WITH MAIZE STALKS USING CARBON-13 NATURAL ABUNDANCE

土壤有机碳分解速率是研究土壤碳动态变化的基础。本文利用13C自然丰度方法和同位素质谱分析技术,通过室内培育实验研究了红壤总有机碳和重组有机碳的分解速率,培养时间为180 d,培养温度为30℃。结果表明:在5%和10%秸秆用量下,红壤总有机碳的分解速率常数为8.2×10-4d-1~22.0×10-4d-1,而重组有机碳的分解速率常数为4.0×10-4d-1~15.6×10-4d-1。施用玉米秸秆明显地促进了红壤原有的总有机碳和重组有机碳的分解,施用量越多,原有机碳分解的越快,表明土壤中原有机碳的分解速率与进入到土壤中的新鲜有机碳量有关。

The dynamics of soil organic carbon （SOC） plays an important role in the global C cycle, while decomposition rate of SOC is essential to understanding of soil C dynamics. The objective of this study was to explore how the natural ^13C abundance method can be used to determine decomposition rates of organic carbon in whole soil and heavy faction of red soils using a laboratory incubation experiment. The soil samples used in the test were collected in March 2003 from a long-term field experiment at Yingtan State Key Agro-Ecological Experimental Stations in China and incubated aerobically at 30℃ in the dark for 180 days. Organic C contents and stable C isotope ratios of the whole soil and its heavy fraction were determined with an elemental analyzer and an isotope ratio mass spectrometer. Results show that the decomposition rates of native organic carbon in the whole soil ranged from 8.2×10^-4d^-1 to 22.0×10^-4d^-1 , and in the heavy fraction from 4.0×10^-4 d^-1 to 15.6×10^-4 d^-1 for red soil incorporated with maize stalks. They were faster in soils incorporated with maize stalks than in soils without maize stalks, which suggests maize stalk incorporation may obviously stimulate the turnover of native organic carbon. Moreover, they were faster when the maize stalk application rate was 10% than when it was 5%, indicating that decomposition rate was related to amount of fresh organic carbon supplied by maize stalks incorporated into the soil. The findings will serve as a foundation for further studies to investigate turnover of SOC fractions using the natural ^13C abundance method.