Soybean root nodules. Yellow on black background.
Soybean root nodules, containing billions of Rhizobium bacteria. Rhizobia are proteobacteria. Photo source: Wikipedia.

Anthropogenic pressures on tropical forests are rapidly intensifying, but our understanding of their implications for biological diversity is still very limited, especially with regard to soil biota, and in particular soil bacterial communities.

The authors evaluated bacterial community composition and diversity in the eastern Amazon, in the state of Pará, Brazil, looking at undisturbed primary forest, primary forests varyingly disturbed by fire, regenerating secondary forest, pasture, and mechanized agricultural areas. They found that land use intensification increased the observed bacterial diversity, and this effect was strongly associated with changes in soil pH. Moreover, land use intensification and subsequent changes in soil fertility, especially pH, altered the composition of bacterial communities, with communities in pastures and areas of mechanized agriculture most different from those in undisturbed primary forest.

These results indicate conversion of tropical forest to other uses impacts soil bacteria not through loss of diversity, as previously thought, but mainly by changing the composition of bacterial communities, with unknown yet potentially important implications for ecological functions and services these communities perform.

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