Microbial processes responsible for nitrous oxide production from acid soils in different land-use patterns in Pasirmayang, central Sumatra, Indonesia

The most probable number (MPN) method and dicyandiamide (DCD), an autotroph-specific inhibitor, were used to identify microbial processes that produced N2O in acid soils. Nitrous oxide production was investigated in six sites in four different land-use patterns at Pasirmayang in Jambi province, in Sumatra, Indonesia, using soils collected in October 1999, March 2000 and June 2000. The six sites were primary forests (P1 and P2), logged-over forests (L2), a young rubber plantation established after forest had been logged and burned in March 1998 (L1), a plantation of Gmelina arborea established after logging and burning of forest in August 1996 (O), and a rubber plantation of a small landholder established in 1993 (R). Very small numbers of autotrophic ammonia oxidizers and autotrophic nitrite oxidizers. were detected. Heterotrophic nitrifiers were detected at all sites, with the highest MPNs at L1 and L2. In incubation experiments, the emission of N2O from soils increased at all six sites after adding citrate, a substrate for heterotrophic nitrifiers. No correlation appeared between denitrification activity and N2O flux. We conclude that heterotrophic nitrifiers are the main microbial contributors to N2O emission from acid soils in Pasirmayang, Jambi.