Molecular discrimination of bacteria (organic versus mineral soil layers) of dry woodlands of Argentina

Abstract

We performed comparative molecular screening of above- and belowground soil bacteria and focused on key functional community members involved in organic matter turn-over, to assess changes due to different management and climatic conditions. Aboveground organic residues (comprising plant- and animal residues) and bulk soil were sampled in summer and winter from two land use strategies (grazed vs un-grazed) and two dry forests of different climate zones of Argentina (Arid Chaco vs Monte). Genetic fingerprinting using polymerase chain reaction - denaturing gradient gel electrophoresis (PCR-DGGE) of bacterial communities, actinomycetes, ammonium oxidizers and N2 fixers was performed and interpreted as function of multiple environmental factors. The similarity differences in bacterial community structures in all analyzed conditions ranged from 12 to 85% and were consistent with i) climatic conditions in the two sampling sites; ii) the impact of land use in arid areas; iii) the temporal heterogeneity of the drylands; and iv) chemical differences between soil and aboveground organic residues. Our results revealed distinct structures of above- and belowground soil bacteria and specific multiple factor responses to environmental changes (natural vs anthropogenic),supporting the capability of comparative molecular screening to gain insights into above- and belowground soil organic matter dynamics.