PB-026:

Bacterial community shift along the primary soil horizons on the recent volcanic deposits in the Island of Miyake (Miyake-jima), Japan

Pesdogenesis is strongly correlated with the vegetation development and microbial succession, however, the role of microorganisms in this process is still little known. The early ecosystem, developing on the volcanic deposits derived from the eruption of Miyake-jima (55.5 km2 in area; the highest point, 775 m) in 2000, provides a suitable material for exploring the pedogenesis interaction. Despite site IG9 (altitude, 380 m) at the lower mountainside of Miyake-jima was characterized by a vigorous vegetation development, no clear soil horizon was found in the belowground volcanic deposit layer by 2011. However, in 2014, three distinct horizons (from top to bottom: O, litter; A/B, soil layers; and C, volcanic layer) were observed at site IG9. Here, we report the chemical properties and microbial communities in the three horizons in 2014. The horizon formation was parallel with increases in TC (7.4, 86, and 199 g kg-1 for C, A/B, and O layers, respectively), TN (0.5, 5.3, and 11.9 g kg-1 for C, A/B, and O layers, respectively) and TDC (7.7, 45, and 109 _108 g-1 for C, A/B, and O layers, respectively). The respiratory activity of sampled deposit was also higher in the O layer (12.4 μg CO2-C g-1 h-1) than the A/B layer (5.5 μg CO2-C g-1 h-1) and the C layer (1.4 μg CO2-C g-1 h-1). In addition, the bacterial and archaeal 16S rRNA gene densities of the O (5.4_1013 copies g-1 and 4.8_1011 copies g-1 for bacteria and archaea) and A/B layers (2.9_1013 copies g-1 and 7.8_1011 copies g-1) were significantly higher than those of C layer (4.1_1012 copies g-1 and 7.1_1010 copies g-1). Non-metric multidimensional scaling analysis of the T-RFLP profiles revealed a clear succession of bacterial community at site IG9 from 2009 to 2014, and also a clear difference in the bacterial community among the three layers of soil horizon at the site. Clone library comparison is now in progress to identify the bacterial groups specific to each of the three horizons.

keywords:volcanic deposits,soil horizon,bacterial community,T-RFLP profiling