Relationship between Cellulolysis and Humification Processes in the West-Central Arid Region of Argentina

We assessed the effects of seasonal variations (dry and wet), substrate type (litter and soil), and land use (grazing) on the relationship between cellulolysis and humification processes in the west-central arid region of Argentina to establish a powerful and realistic pattern to close this information gap in terrestrial C modeling in dry lands. Three composite samples of soil and litter were collected from ungrazed and grazed sites, and the following parameters were analyzed: (i) in all samples: water content, cellulolytic microorganism abundance, activity, and efficiency (activity/abundance); (ii) in litter: organic C, insoluble fiber, and phenol contents; and (iii) in soil: organic C, fulvic and humic acids, nonhumic substances, and polymerization and humification indexes. The cellulolysis and humification processes were significantly affected by seasonal variations, substrate type, and grazing. Many significant interactions were detected among the analyzed factors, with cellulolytic activity the most sensitive parameter. All of the cellulolysis parameters were correlated with the total soil organic C and humified fractions, although there was no significant correlation with nonhumic substances. Our results suggest that cellulolytic activity and efficiency are two key parameters that should be taken into account in modeling decomposition and transformation of organic matter in soil. This approach should contribute to filling the existing gap of knowledge found in the existing literature about microbial activity, substrate, and products related to terrestrial C modeling.