First Year Soil Impacts of Well Pad Development and Reclamation On Wyoming's Sagebrush Steppe.

In recent years, natural gas extraction activities have disturbed thousands of acres of arid and semiarid regions in Wyoming’s sagebrush steppe ecosystem. Thin, nutrient poor topsoils, combined with subsoils potentially high in salts, limit the resilience of these arid and semiarid soil systems. Stripping and stockpiling topsoil stimulates decomposition and loss of soil organic matter (SOM) by breaking apart soil structure and eliminating inputs of plant residues, which can result in reduced SOM content. When the soil structure is disturbed organic matter can rapidly decompose, releasing mineral nutrients that are mobile and can be lost to weeds, leaching, erosion, or volatilization.  Preliminary data suggests that the soil organic matter that is needed for plant growth becomes mineralized or released when the soil is disturbed.    The data shows a small increase in mineral N concentrations after stripping and stockpiling compared to undisturbed soils, and then a large increase available N following respreading for reclamation.  This suggests that easily decomposable organic matter is conserved in deep stockpiles but then decomposed upon re-exposure to air and moisture with respreading.  The spike in mineral N originates from organic compounds that, in undisturbed conditions, hold and slowly release N and other nutrients. It represents a significant potential loss of this important “time-release” nutrient pool. The spike in mineral nutrients probably stimulates prolific weed production often observed on reclaimed sites. Weeds that stay and decompose on site may conserve and recycle the nutrients, but the data suggest a need for a better way to accomplish this.  Biochemical processes governing ecosystem C and N storage and transformations that exist in these ecosystems and how they respond to increasing anthropogenic disturbances are not clearly understood.  Information on SOM pools, processes of C and N mineralization and contributions to soil fertility recovery over time is lacking.  Understanding how ecological structure and functioning is disrupted is crucial to successfully reconstruct attributes that support ecosystem services. Soil samples were collected from three natural gas fields located in Western Wyoming.  During the first year of this study soil samples were collected from stockpiles, respread topsoil and adjacent undisturbed areas.  The purpose of this study is to gain an understanding of how natural gas development and reclamation activities impact soil properties, plant growth re-establishment, and the ability of disturbed sagebrush ecosystems to recovery over time.