[Dynamic changes of soil amino sugar contents under drying and wetting cycle]

A soil incubation test was conducted to study the quantitative changes of three amino sugars (glucosamine, muramic acid, and galactosamine) derived from microbes under drying and wetting cycle, and to analyze the relative contribution of soil bacteria and fungi to the turnover of soil organic matter by using the measured glucosamine/muramic acid ratio. Under continuous wetting, the degradation of bacteria-derived muramic acid was faster than that of fungi-derived glucosamine, and the degradation rate of galactosamine was the lowest. Drying and wetting cycle altered the degradation characteristics of the three amino sugars. As compared with that under continuous wetting, the degradation rate of bacteria-derived muramic acid at the prophase of drying and wetting was faster than that of fungi-derived glucosamine, and, with the increasing frequency of drying and wetting cycle, the degradation rate of fungi-derived glucosamine was faster than that of bacteria-derived muramic acid. These results indicated that drying and wetting cycle changed the course of the microbial transformation of soil amino sugar-derived nitrogen.