淹水和好气条件下东北稻田黑土有机碳矿化和微生物群落演变规律

Investigation of soil organic carbon mineralization and microbial community structure evolution of northeast paddy black soil in waterlogged and aerobic conditions

通过360 d室内恒温(30℃)培养,研究淹水和好气条件下土壤碳的动态变化及微生物群落结构演变规律。结果表明,淹水条件下,土壤TOC(总有机碳)降幅(8.68%)略高于其在好气条件下的降幅(6.23%),但差异不显著(P>0.05),DOC(溶解性有机碳)含量显著高于其在好气条件下的含量(P<0.05)。土壤有机碳在淹水条件下的矿化速率常数(0.009 5)显著高于其在好气条件下的矿化速率常数(0.007 5)。土壤淹水条件下的AWCD_(96h)(96 h平均光密度)呈现0~15 d显著低于好气条件、30~60 d差异不显著、60~360 d显著高于好气条件的规律(P<0.05)。淹水条件下,土壤微生物由以利用氨基酸类碳源为主,演变为以利用酚酸类(30~60 d)和氨基酸类碳源(180~360 d)为主;而在好气条件下则演变为以利用多聚物类碳源(60~360 d)为主。淹水提高了土壤DOC含量,增加了土壤微生物可利用底物和微生物活性,提高了土壤微生物对酚酸类和氨基酸类碳源利用,加快了土壤有机碳矿化。

Soil carbon dynamics and microbial community structure were studied at 30 ℃ under simulated waterlogged and aerobic conditions in the laboratory. Results showed that soil total organic carbon（TOC）concentrations did not change during the 360-day incubation period in either waterlogged or aerobic conditions. The change in TOC concentrations was greater under waterlogged conditions（8.68%）than under aerobic conditions（6.23%）, but the difference was not statistically significant（P〉0.05）. During the entire incubation period, the concentration of dissolved organic carbon（DOC）in waterlogged conditions was significantly greater than that under aerobic conditions（P〈0.05）.The mineralization rate constant（0.009 5 d-1）in waterlogged conditions was also significantly greater than that（0.007 5 d-1）in aerobic conditions; both rates were well fitted by the first-order kinetic equation. Values of the average well color development at 96 h（AWCD96h）（an index of catabolism of specific carbon substrates）for microbial communities in waterlogged conditions were significantly lower than those in aerobic conditions from 0 to 15 d. There were no significant differences in AWCD from 30 to 60 d, but from 180 to 360 d, the AWCD values for anaerobic microbial communities were significantly greater（P〈0.05）than those in aerobic conditions. At the beginning of incubation, the carbon resources used by soil microorganisms were mainly amino acids. In waterlogged conditions, they gradually changed to phenolic acids（3060 d）and amino acids（180360 d）, while they changed to polymer carbon sources（60360 d）in aerobic conditions. Waterlogged conditions increased the contents of soil DOC, soil microbial activity and metabolism, and the utilization of phenolic acid and amino acid carbon sources by soil microorganisms, and thus promoted the mineralization of soil organic carbon.