Abstract:

Microbial community functional diversity is a sensitive indicator of soil. Forest fires can change microbial community functional diversity. In this research, the fired soil samples were collected from Huzhong of Daxing’anling in Heilongjiang Province. The functional diversity of soil microbial community was detected by BIOLOG system. The average well color development (AWCD) in BIOLOG plates indicated the ability of carbon substrate utilization of microbial community. The indices of Shannon, Simpson and McIntosh were calculated to show the richness, dominance and evenness of the functional diversity, and the principal component analysis of substrate reactions reflected the main carbon sources utilized by microbial community. The results showed that all the samples exhibited the reduction of AWCD during the first 144 hours of incubation, but there were obvious differences in the reduction degree among the samples. All kinds of fire intensities could influence microbial community functional diversity. The low fire intensity increased the richness (Shannon), dominance (Simpson) and evenness (McIntosh) of microbial community. However, the intermediate and high fire intensity reduced these parameters, suggesting that the burned soil emitted gaseous nitrogen, a number of organic carbon and available phosphorus, which caused the reduction of the microorganism in quantity and type, and change in soil ingredients. The organic material reduced in the burned soil, in the same time, the pH values rose, which changed environment in which microorganism lives. The changed environment might not be conducive to activities of the microorganism. The principal component analysis showed that the main carbon sources for soil microbes were carbohydrates and amino acids and the carbon substrate utilization patterns in different samples were significant different. Our results indicated that functional diversity of soil microbes were altered by forest fires, and the ability of microbes to utilize carbon source and the type of carbon sources were affected by different forest fire intensities.

Key words: forest fire, forest fire intensity, microbial community functional diversity, BIOLOG