Fracking pond restoration in the western Rio Grande Plains, Texas: Stockpiled topsoils may not be necessary, but seeding helps

Abstract

Soil disturbances that accompany energy development can damage local habitats. Prior to oil and gas extraction, it is commonly recommended that topsoil stockpiles be created to aid future restoration. Our study area, a retired fracking pond in the western Rio Grande Plains, Texas, was restored in 2017 with stockpiled topsoil that was collected in 2013. We segregated the existing stockpile into three layers that were ∼1.5 m in thickness and distributed these layers, along with a non-amended control surface (consisting of former subsoil that made up the perimeter of the fracking pond), in strips over the restoration area. Each of the four surfaces was seeded with a mixture of (1) 13 native grasses, (2) 13 native grasses plus an annual warm-season grass cover crop, or (3) non-seeded. We monitored plant density and species composition two through five years post-restoration. The non-amended control surface had higher seeded grass density during the final 2 sampling periods; stockpiled surfaces seldom differed from each other. Previous year's competing plant density had little effect on restoration success. Providing supplemental seed initially increased seeded plant density but benefits diminished over time; adding a cover crop was not advantageous. Changes in community composition over time were similar on stockpile surfaces but more variable than observed on the control surface. Results suggest that stockpiling topsoil may not be necessary, but that supplemental seeding was beneficial, to restoration success.