Influence of moisture and organic matter in soil microorganisms abundance of the Médanos Grandes de Caucete, San Juan

VEGA AVILA A.D; SALOMON, M.V.; NOÉ L.; ABRIL A.; TORO M.E.; VAZQUEZ F.

Rosario

Congreso; V Congreso Argentino de Microbiología general; 2008

Sociedad Argentina de Microbiología General (SAMIGE)

oil microorganisms play a fundamental role in organic matter decomposition and nutrients recycle because several stages of the nutrient cycle are mediated exclusively by microorganisms, and some of them can participate in one or more biogeochemical cycles. In arid soils microorganisms¡¯ abundance and activity can be restricted by climatic conditions, water availability mainly. This is reflected in organic matter decomposition and nitrogen fixation. The objective of this work was to evaluate the soil microbial biomass which corresponds to functional groups and their relation with organic material and moisture amounts in M¨¦danos Grandes, Caucete, San Juan province, seasonally. Samples of soil (0-20 cm depth) at two well differentiated environments (sand dune and interdune) were taken in autumn and winter. It was determined soil moisture and organic matter content. The abundance of ammonifiers, nitrifiers, and cellulolytic functional groups of microorganisms was determined by MPN method. The abundance of free living N fixing was analyzed by plating count. Total biomass is the accumulate abundance of studied functional groups. Results: in the entire studied place, microorganisms¡¯ abundance show significant differences (p¡Ü 0.05) between seasons (winter: 18.14 log CFU g-1; autumn: 14.59 log CFU g-1). Organic matter and moisture did not show significant differences. Seasonal analyses of parameters from each environment show significant differences in accumulated biomass (autumn: 14.42 log CFU g-1winter: 18.16 log CFU g-1) and moisture (autumn: 0.52%; winter: 0.94%) of sand dune. In autumn the accumulate abundance of microorganisms was related to the moisture and organic matter in both environments studied: Sand dune (Biomass/Humidity: R2 0.42; Biomass/OM: R2 = 0.94); Interdune (Biomass/Humidity: R2 = 0.38; Biomass/OM: R2 = 0.52). On the other hand, was found correlation between parameters only in interdune (Biomass/Humidity: R2 = 0.66; Biomass/OM: R2 = 0.42) in winter. Conclusion: seasonally changes in edaphic microorganisms¡¯ abundance can be related to changes of water availability. The characteristics of sand dune can influence water retention so; this fact can be better reflected in this place. In these environments water availability depends on rainfall pulses. The use of the recourse when the pulse occurs can be responsible for the variation on edaphic microorganisms¡¯ abundance. The organic material is not a limiting factor.