Drastic Disturbance of Salt-Affected Soils in a Semi-Arid Cool Desert Shrubland

Abstract

Disturbing soils in arid regions can mix subsurface materials with surface soils salvaged for reclamation. Pre-disturbance assessment of soils can minimize impacts of disturbance, and better understanding of drastic disturbance in arid soils will improve reclamation success. Reclaimed well pads have undergone stockpiled soil respreading, tillage, and seeding after drilling is complete. Soil texture and chemical properties were analyzed at 0–15 cm depth in saline and sodic soils from eight paired undisturbed and recently reclaimed sites in the Great Divide Basin of Wyoming. Soil organic matter and structural properties were analyzed in additional samples from two of the paired sites (one sodic, one saline-sodic). Paired difference analysis across the eight well pads indicated that disturbed/reclaimed soils had higher electrical conductivity (EC) than undisturbed soils (12.2 and 3.0 dS m⁻¹, respectively) and higher sodium adsorption ratios (SAR) (26.1 and 1.3, respectively). Analysis of variance of soil organic C (SOC), total N, and soil structural properties indicate that disturbed soils had nearly one-third less total N and two-thirds less SOC than undisturbed soils, and over 65 times more >9.5 mm dry aggregates by weight, representing predominance of large clods in disturbed soils on both sites. Disturbed soils contained significantly smaller proportions of smaller dry aggregate fractions (<53 µm, 53–250 µm, and 250 µm–1 mm) than undisturbed soils, and saturated hydraulic conductivity (K_sat) was about 25% of that in undisturbed soils. Disturbed soils exhibited lower organic materials, higher salt contents, altered soil structure, and low potential for eventually supporting successful native plant communities.

Keywords:

• disturbance
• reclamation
• saline-sodic
• sodic

Acknowledgments

We thank Raymond Ansotegui and Cally Driessen of KC Harvey Environmental LLC for facilitating fieldwork, Gary Austin of BP America for allowing us to conduct this research in their Wamsutter natural gas production area, and Kristi Bear, T. J. Peters, Alan Hamner, and Leann Naughton for assistance in the field and lab.