Tree species identity has little impact on the structure of soil bacterial communities in a 10-year-old tropical tree plantation

We investigated whether tree species identity has a significant impact on the structure of soil bacterial communities in a tropical tree plantation (Sardinilla, Panama). The experimental site contains tree species native to Panama, planted in both monoculture and mixed-species plots. Using a DNA fingerprinting approach (automated ribosomal intergenic spacer analysis [ARISA]), we identified significant differences in the community structure of abundant bacterial taxa in the bulk soil among all monoculture plots. We similarly found differences among plots containing five, three, one or no tree species. While distance-based gradients in bacterial community structure were detected across the plantation, further investigation revealed that the observed heterogeneity was, in fact, poorly related to the tree species in a given plot. We provide evidence that site related features (e.g., variability in soil pH) play a more important role in regulating the structure of bacterial communities within the bulk soil than tree species identity or richness.