Can soil invertebrates indicate well pad reclamation success on cultivated lands?

Randi Lupardus, USGS Canyonlands Research Station, Moab, UT, Arnold Janz, Alberta Environment and Parks, Government of Alberta, Edmonton, AB, Canada, Jeffrey Battigelli, Northern Alberta Institute of Technology, AB, Canada and Lisa Lumley, Royal Alberta Museum, Edmonton, Canada

Background/Question/Methods
Integrating soil physico-chemical properties and soil invertebrate bioindicators could prove a practical and robust method for assessing reclamation and soil biological quality of cultivated lands disturbed by oil and natural gas activities. Until the current study, there have been no data or analyses showing these relationships in cultivated lands. We examined a fine line between two types of disturbance (i.e., cropland, oil & gas reclaimed cropland) and the invertebrates that could tolerate these disturbed conditions. We aimed to determine if 1) crop type, age class, reclamation criteria, soil type, disturbance history (reclaimed wellsite) or a combination of these factors, influenced/affected invertebrate abundance; 2) invertebrate community abundance correlated with soil physico-chemical properties or with the presence of major mesofauna taxa, and 3) if reclamation efforts, plus the additional yearly cultivation activities, ameliorate the biological effects of oil and gas disturbance.
Results/Conclusions
Although we identified a clear trend in the densities and abundances of major mesofauna taxa, they did not differ significantly between groups. Reclaimed sites appeared more susceptible to crop pests (Psocoptera and Hemiptera), especially on younger sites, which could have been driven by higher bulk density (low aeration). There were clear differences in soil physico-chemical properties (e.g., bulk density, pH, TOC), which were not reflected in the Acari:Collembola (A:C) ratios, invertebrate density, or community results. There were some correlations between physico-chemical properties and specific invertebrate groups. Oribatida were positively correlated with EC; Astigmata, Oribatida, and Symphyla were negatively correlated with bulk density; Prostigmata, Collembola, and Mesostigmata were negatively correlated with pH, and Mesostigmata were positively correlated with TOC. The site age results indicate that cultivation activities may reset invertebrate community succession each year, creating densities and abundances similar to that of adjacent cultivated fields and masking long-term industrial effects. For these reasons, neither broad invertebrate taxa nor A:C ratios should be used as indicators of reclamation quality or biological recovery on industrially reclaimed, cultivated sites. We foresee expansions of this research with functional trait analysis, as well as exploring differences at a finer taxonomic level within invertebrates.