Search

Microbial biomass in the soils of burned and unburned Japanese red pine forests in the Setouchi District, Western Japan was determined by a slightly modified chloroform fumigation-incubation method. Averages±standard deviations of microbial biomass carbon (C) of 36 unit samples in the 0-5cm soil layers at burned sites located in Ato and Nenoura were 307±206 and 789±274mg kg-1 dry soil, respectively, and that at an unburned site at Ato was 408±213 mg kg-1 dry soil. Soil microbial biomass C at the burned sites were approximately the same or slightly higher than at the unburned site. In contrast with soil microbial biomass, the above-ground plant biomass at the burned sites was about one-fifth or one-sixth of that at the unburned site. Microbial biomass C in the FH layer at the unburned site at Ato was 13.38±6.13g kg-1 dry soil. No significant fluctuations of microbial biomass were observed through 1 year in the 0-5cm soil layers at either the burned and unburned sites, nor in the FH layer at the unburned site. The ratios of microbial biomass C to total C in the soils at the burned sites were 3.2-3.3%, significantly higher than those at the unburned site (2.1%). Significant correlations were observed between microbial biomass C and some soil characteristics, such as contents of total C, total nitrogen (N) and water, in both burned and unburned soils.

Soil microbial biomass was estimated in the burned and unburned Japanese red pine forests by the chloroform fumigation-incubation method. Along with this study numbers of some microbial groups (fungal spores, actinomycetes, total bacteria, gram-negative bacteria and bacterial spores) were investigated in the same soils by dilution plate count technique.Microbial biomass-C in the 0-2cm soil layer at the burned site at Nenoura fluctuated from month to month during the period from February, 1986 to July, 1987 (34-51 months after fire) in the range from 74 2 to 134.9mg/100g dry soil, relatively low during the period from December to April and maximal in October, 1986 and June, 1987. Microbial biomass in the 0-2cm soils at the burned sites at Tennoh (4 months after fire) and Norosan (80 months after fire) and the unburned site at Ato were almost the same level as that at the burned site at Nenoura. In contrast to the relatively small fluctuations of biomass, the numbers of microorganisms, especially those of total and gram-negative bacteria, fluctuated extensively from month to month. The greater numbers of total and gram-negative bacteria appeared in October-December in the 0-2cm soil layer at the burned site and in the FH and 0-2cm soil layer at the unburned site. The numbers of all microbial groups essentially decreased in August to early-September.