Influence of vegetation in the spatial variation of microbial abundance in Monte desert, San Juan, Argentina

Due to the lack of water, vegetation in desertic ecosystems is distributed in patches. Microorganisms associated to patches are important in plant growth because favor nutrients uptake, nitrogen fixation and organic matter decomposition; also release fundamental enzymes in nutrients cycle. The objectives of this work were to evaluate the abundance of microbial groups (bacteria, yeasts and filamentous fungi) and to detect and quantify bacteria with enzymatic activities in soils and leaves of Bulnesia retama, Larrea divaricata, and interspaces with bare soil areas; to establish relations between plant distribution and the functional groups of microorganisms involved in litter plant decomposition. No significant differences were detected in the abundance of bacteria and yeasts among all different microsites, although filamentous fungi abundance was higher in soil of patches associated to L. divaricata respect to bare soil areas. The percentage of isolated bacteria colonies that showed enzymatic activities (xylanolitic and amylolitic) was higher in patches of L. divaricata and B. retama than in interspaces. Isolated bacteria from leaves of L. divaricata showed xylanolitic, amylolitic and cellulolitic activities. It was found that abundance of bacteria in patches was higher than in leaves of canopies of the studied plants; it was also found higher percentage of bacteria colonies that showed at least one of the enzymatic activities involved in organic matter decomposition. The results suggest that there could be a relationship between abundance of some bacteria functional groups and the vegetation distribution.