Over the last 50 years, Alberta has accumulated over 100,000 wellsites that have been certified as reclaimed or are considered exempt from reclamation. To address a lack of long-term monitoring of wellsites, we have developed protocols and indices for assessing ecological recovery of these wellsites. In 2014, we implemented the developed protocol and sampled in Alberta’s forested lands, including 15 wellsites in the Central Mixedwood Natural Subregion and 15 wellsites in the Lower Foothills Natural Subregion, ranging from 7-45 years post-certification. Our field soil sampling protocols measured electrical conductivity, total organic carbon, total nitrogen, pH, and bulk density of the soil for up to four soil depths. We also measured plant species richness, diversity, percent cover by species, stem density, basal area of stems, and downed woody material. The objectives of this study were to determine if certified reclaimed forested lands were on a positive successional trajectory for recovery, if indices had met specific thresholds, and to determine which indices were most influential to recovery.
Results/Conclusions
Using hierarchical mixed models and generalizable estimating equations, we found wellsite reclamation has a strong effect on soil properties (e.g., total nitrogen, electrical conductivity, bulk density, pH) at each soil depth. Questionable threshold exceedances were also identified and modeled. The strongest predictors for soil threshold exceedances were site type (wellsite, reference), soil depth (0, 15, 30, 60), and adjacent forest stand age, but surprisingly not site age. This indicates that some sites are not recovering with time (i.e., are not on a positive trajectory). The plant community composition ordinations illustrated separation of the wellsite and reference locations across ages post-certification. Overall, our data show that wellsite development impacts can be long lasting and may remain for 50 years or more after reclamation, flatlining the recovery trajectory. The findings of our study and development of a long-term monitoring program for reclaimed wellsites in Alberta will improve our ability to adaptively manage into the future by providing novel insights into the trajectories of ecological recovery.