Revisiting Reclaimed Well Pads in Boreal Forests: The Role of Time and Changing Criteria in the Recovery of Vegetation Composition, Forest Structure, and Plant Traits

Boreal forests provide multiple ecological and economic services, including carbon storage, provision of wildlife habitat and recreational space, and timber supply. In Canada’s western boreal forests, natural resource energy exploration and extraction results in substantial anthropogenic disturbances, including clearing forests for well pads. Well sites are decommissioned and then reclaimed: a process whereby disturbed land is to be set on a trajectory of ecological recovery. However, after meeting reclamation requirements sites are rarely monitored, resulting in uncertainty about long-term successional trajectories. Ecological succession of these post-reclaimed sites may be arrested, contributing to landscape fragmentation and its associated negative consequences. This includes loss of habitat and thus biodiversity, greater vulnerability to invasive species, and changes to ecosystem processes. To understand post-reclamation recovery, we collected data on vegetation at 25 well pads and adjacent reference boreal forests in north-west Alberta, Canada. Taxonomic (e.g., species occurrence), structural (e.g., basal area), functional (e.g., specific leaf area) and soil property (e.g., bulk density) data were used to assess the recovery trajectories of well pads of varying post-certification ages. Multivariate ordinations and analyses, generalized additive mixed models, and mixed effect models were used to quantify recovery patterns. Our analyses demonstrated that well pads of varying ages and criteria groups differed from adjacent reference forests. However, soil FH depth, leaf carbon, and diversity measures showed resilience. Overall, our data suggest that many well pads are not recovering even 44 years post-reclamation and that more time is needed to assess if recent changes to criteria are aiding recovery. Other factors may be influencing the trajectory of recovery in the understory plant community more than the time since post-reclamation. Results from this study can improve our understanding of post-disturbance successional dynamics and may help inform mitigation actions used to remove biological and environmental barriers limiting ecological recovery