ARS | Publication request: Long term stability of microbial diversity and activity potential in severely disturbed arid lands of the southwest

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 31, 2011
Publication Date: N/A

Technical Abstract: Arid land cryptobiotic soil crusts govern water infiltration, soil aggregate stability and nutrient cycling between soil microbial communities and vascular plants. Surface mining involves removal of topsoil and associated crust and storage in mixed mounds for extended periods. The exposed subsoil and stored mounds create conditions drastically different from original crust. Exposed subsoil is possibly re-inoculated by wind carried microbes. The minimal precipitation in these regions rarely penetrates soil mounds that remain dry. Common remediation management involves replacement of stored soils on degraded surfaces. The success of this remediation approach depends on the capacity of these soils to maintain and express microbial activity potential. Objectives: We investigated soil microbial diversity and Nitrogen cycle activity potential for surface mining, gas well pads and recently remediated soils in the Southwest U.S. Soil samples were collected from the surface crust and up to depths of 60cm from both undisturbed and disturbed sites. Methods: Bacterial and fungal genetic diversity was estimated by targeted pyrosequencing. Residual microbial activity potential was estimated by quantifying N cycling genes. Tested genes describe the entire N cycle from nitrogen fixation (nifH), ammonia oxidation (amoA), respiratory nitrate reduction (narG), dissimilatory reduction of nitrate to ammonia (napA), reduction of nitrite to nitric oxide (nirK and nirS), to reduction of nitrous oxide (nosZ). Data was normalized per 16s rDNA count. Results: Diversity analyses indicate that most heterotrophic soil crust originating taxa persist in disturbed and buried layers and maintain their activity potential. Autotrophic cyanobacteria were the most affected by disturbance.