Long-term dynamics of soil organic carbon and effect of temperature increase on the residence time of soil organic carbon

1. 为了阐明土壤有机碳的长期动态，分析了土壤有机碳的^<14>C年龄与腐殖化程度、由^<13>C CPMAS NMR谱估计的C官能团组成、氧化钌氧化（RTO）氧化降解释放的多核芳香族组分组成以及土壤腐殖酸δ^<13>C之间的关系。从稻abu （Toyota, aiichi）和Miyazaki （Miyazaki, Miyazaki）两种棕色森林土壤的A2或A3层提取腐植酸，用丙酮-0.01 M NaOH分馏法将腐植酸分成7或8个馏分。在每种土壤中，^<14>C年龄与腐殖化程度的两个变量之间存在显著的相关性。随着^<14>C年龄和腐殖化程度的增加，腐植酸C以烷基C和芳香C形式存在的比例分别降低和增加。对RTO产物的GC分析表明，随着年龄的增加，多核芳香族结构的含量和缩合度都有所增加。另一方面，两种土壤的腐殖质化程度随时间的增加速率不同，稻abu的整个腐殖质化过程为2800年，而宫崎的为190年。然而，与以往的结果比较表明，Inabu的结果是一个特例，温度条件的差异并不影响腐植酸结构变化的速度。酸水解去除糖类和多肽只改变腐植酸馏分的^<14>C年龄30年。因此，在腐殖化的初始阶段，这些成分被纳入腐植酸结构中，并得以存活。温度升高对土壤有机碳停留时间的影响为了解全球变暖对腐殖化不同阶段土壤有机碳停留时间的影响，采用15、20、25、30、34、37和40℃对稻褐林A1层土壤进行了培养。分别于40、120、260、365 d采集土壤，测定总C、腐植酸C含量及腐植酸腐殖化程度。用丙酮-0.01 M NaOH分馏沉淀法测定了腐植酸组成随腐植酸化程度的变化。温度在= 30℃时，土壤总碳的下降幅度大于低于30℃时。365 d后，7个处理间腐植酸含量差异不显著。腐殖质化程度越小，分级降水没有减少。因此，温度从15℃升高到40℃，对腐殖物质在一年内的停留时间没有影响。少

1. Relationship between structural properties and ^<14>C age of soil organic carbonTo elucidate the long-term dynamics of soil organic carbon, relationships between ^<14>C age and degree of humification, composition of C functional groups as estimated by ^<13>C CPMAS NMR spectra, composition of polynuclear aromatic components released on oxidative degradation with ruthenium oxide oxidation (RTO), and δ^<13>C of humic acids in a soil layer were analyzed. Humic acids were obtained from the A2 or A3 horizon of two brown forest soils, Inabu (Toyota, Aichi) and Miyazaki (Miyazaki, Miyazaki), and fractionated by fractional precipitation with acetone-0.01 M NaOH into seven or eight fractions. In each soil, there were significant correlations between ^<14>C age and two variables indicating degree of humification. With increasing ^<14>C age and degree of humification, the proportion of humic acid C present as alkyl C and aromatic C decreased and increased, respectively. GC analysis of RTO produ … More cts showed the increases in the content and degree of condensation of polynuclear aromatic structures with increasing ^<14>C age. On the other hand, the rate of increase in the degree of humification with time differed between the two soils: 2800 years for whole humification process in Inabu while 190 years in Miyazaki. Nevertheless comparison with the previous results suggested that the Inabu result is a specific case and the difference in temperature conditions does not affect the rate of structural changes of humic acids. Removal of saccharides and peptides by acid hydrolysis changed ^<14>C age of humic acid fractions only by 30 years. Therefore, such components were incorporated in the humic acid structure during the initial stage of humification and have been survived.2. Effect ofincrease in temperature on the residence time of soil organic carbonTo understand the influence of global warning on the residence time of soil organic carbon at different stage of humification, the A1 horizon of Inabu brown forest soil was incubated at 15, 20, 25, 30, 34, 37, and 40℃. Soil was collected after 40, 120, 260, and 365 days, and total C and humic acid C content as well as the degree of humification of humic acid were determined. Change in the composition of humic acids with respect to the degree of humification was also examined using factional precipitation with acetone-0.01 M NaOH. Total C in soil decreased with a larger extent at temperatures of〓30℃ than at less than 30℃. However, humic acid contents after 365 days did not differ significantly among the seven treatments. Fractional precipitation showed no decrease in the fractions with smaller degree of humificatioan. Thus, the increase in temperature from 15 to 40℃ did not influence the residence time ofhumic substances within a year. Less