Abstract

The construction of well sites for oil and gas extraction can cause negative environmental consequences through removal of the plant community and soil layers, leveling the landscape, and soil compaction. Reclamation techniques have been used to lessen these effects with the intention of returning the area to its pre-disturbance state. However, research assessing ecosystem recovery on well sites has shown that these techniques are not achieving this goal with sites experiencing arrested or slowed succession. The aim of this study is to prioritize well pads that require further reclamation to achieve a better ecological outcome and to identify the biophysical attributes that demand intervention. Species cover and soil data were collected at reclaimed well sites of varying ages in Central Mixedwood and Lower Foothills natural regions in central Alberta using a nested plot design in 4 quadrants. Data were then aggregated to site means and transformed for normality. Multivariate analyses (e.g., PCA, gradient analysis, CanCor) were used to reduce complexity of the data, visualize, and quantify relationships among soil and cover data. Sites were clustered using k-means to designate priority groups for ranking which sites should be targeted first. From this study, we conclude that organic layer depth, soil bulk density, and non-native plant cover are strongly associated with well pads that are not regenerating post-reclamation and require further intervention. Years since reclamation was associated with higher tree cover and lower graminoid cover. Given these attributes, we recommend light tillage and addition of soil amendments (principally manure and sulfur) for high priority sites. While well site reclamation criteria was updated in 2010 with improved requirements for use of native species, it is clear that older sites may still need further reclamation to set them on a natural successional trajectory.