Comparison of soil bacterial communities between coastal and inland forests in a subtropical area

Abstract

The diversity and composition of soil bacterial communities in four subtropical coastal forest ecosystems were examined using 16S rRNA gene clone libraries. The communities were collected from forests in two islets, Green Island (GI) and Orchid Island (OI), and two coastal forests in Chenggong (CG) and Shitoushan (ST) in southeastern Taiwan. At the elevation ranges from 60 to 340m, the mean annual precipitation is >2200mm, the mean annual temperature is about 22°C, and the soil pH is about 5–6. These forests were compared to an inland natural low montane forest ecosystem with less humidity and more acidic soils. The phyla Acidobacteria and Proteobacteria predominated among these forest soil communities. Within the Proteobacteria, the α-Proteobacteria was the most abundant group. The proportion of Verrucomicrobia at one OI study site was significantly higher than that in other communities. Based on the richness and the rarefaction curve analysis, the GI community was the most diverse. Analysis of molecular variance revealed that the communities at two islet soils and coastal soils were similar, although these islets are isolated ecosystems. Most of the abundant operational taxonomic units (OTUs) did not differ significantly among the coastal forest soils. Compared to coastal forest soil communities, the inland natural forest soil community was less diverse and Proteobacteria accounted for more than half of the community. In contrast to the coastal communities, γ-Proteobacteria was the most abundant proteobacterial class in the inland community, and the most abundant OTU only existed in inland soils. These results suggest that climate conditions and soil characteristics affect the bacterial community composition in coastal and inland forest soils. Disturbance by human activity is another factor that may influence the diversity of the coastal forest soil community.