Is the nitrification a redundant process in arid regions?: activity, abundance and diversity of nitrifiers microorganisms

NOE L; ABRIL A

REVISTA CHILENA DE HISTORIA NATURAL

SOC BIOLGIA CHILE

Lugar: Santiago de Chile; Año: 2013 vol. 86 p. 325 - 335

0716-078X

We tested if the microbial functional redundancy concept (theory relating changes in ecosystem functioning by species loss) apply for changes in the ammonium-oxidizing community (nitrifi er bacteria) due to: a) grazing disturbance, b) seasonal variations (dry season vs. wet season), c) habitat type (soil vs. organic residues), and d) ecological conditions (two eco-regions), in an arid region of central-western of Argentina. We determined: a) abundance of culturable nitrifi er bacteria, b) nitrifi cation activity and effi ciency, and c) nitrifi er community genetic structure by PCR-DGGE (richness and similarity index). Grazing did not change the nitrifi er abundance, activity and richness, while seasonally and eco- region effects were scarce. Contrarily, the habitat type affected nitrifi er activity, which was higher in organic residues than in soil. All similarity indexes were low (average 0.50, range 0.76-0.18) which suggest high species diversity in these arid eco-regions. Our results indicate that the nitrifi cation process in arid region of Argentina is redundant but it applies only for each habitat. To our knowledge, this is the fi rst functional redundancy study on microbial ecological process in disturbed arid zones, in which we report an important species replacement but without modifi cations in microorganism abundance and activity.