Soil Disturbance Increases Soil Microbial Enzymatic Activity in Arid Ecoregions

Functional diversity of the soil microbial community is commonly used in the assessment of soil health as it relates to the activity of soil microflora involved in carbon cycling. Soil microbes in different microenvironments will have varying responses to different substrates, thus catabolic fingerprint information of each location-specific community can be obtained. The purpose of this study was to evaluate total-soil enzymatic activity profiles across three disturbance regimes in an arid desert grassland in the Southwestern United States. Microbial enzymatic activity was measured using the MicroResp™ system, which measures respiration of microbes within whole soil samples supplemented with various carbon sources (simple and polymeric sugars, amino acids, carboxylic acids, and fatty acids - tests run in the absence of light). Total bacterial diversity was assessed by 16s DNA pyrosequencing. Microbial activity was greatest and most variable in sites exposed to disturbance (grazing, natural gas extraction). Decoupling the C cycle from the C-fixing cyanobacteria may induce more diverse C uptake pathways associated with a more diverse microbial population. Similarities in taxonomic diversity and C substrate utilization patterns show that, for arid lands, any degradation-enhanced heterogeneity in soil’s biotic and abiotic parameters may drive changes in soils towards higher functional diversity to adapt to the disturbance