Invasive plant dispersal along the new corridors of shale gas extraction

March 19, 2014 @ 01:20 pm to 02:10 pm

Katy Barlow, Penn State

104 Forest Resources Building

The vast network of well pads, compressor stations, access roads and pipelines developed for natural gas extraction in the Marcellus shale is fragmenting the natural landscape across Pennsylvania. We hypothesize that these new edges carved into forests and fields to make way for the extraction infrastructure will facilitate the spread of invasive plants, exacerbating the problem in currently invaded areas and creating new corridors for invasion in less disturbed settings. During the summer of 2012 we conducted a study to document the presence and extent of invasive exotic plants spread around well pads in the Pennsylvania State Forest system. Landscape fragmentation information for each pad locale was derived from aerial imagery in ArcGIS to identify characteristics of the forest sites that may help explain the current state of invasion. We selected sixty-seven well pads distributed across four Pennsylvania State Forests (Tioga, Tiadaghton, Sproul, and Hyner Run) and the Allegheny National Forest. For each pad, we recorded the abundance of a predefined list of 23 invasive exotic plants along the roads approaching the pad entrance (starting 0.5 km before the pad entrance), and around the pad perimeter (a band approximately 10 m from the gravel edge of the pad into the surrounding landscape). Overall, 60% of pads surveyed were invaded by at least one invasive exotic plant. Of those pads invaded, 45% harbored three or more species and 20% had individual species at abundance levels between 100 and 1000 plants around the pad perimeter. Invasive plant abundance along roads approaching the pad was a positive indicator of invasive plant abundance around the pad. The extent of prior disturbance (more edge) in the pad locale was also a factor explaining the current state of invasion around the pads. Differing seed dispersal mechanisms, such as spread by wind versus bird, and secondary dispersal such as movement by vehicle tires, likely play a role in the varying presence and abundance levels seen in species movement from nearby roads to the pad. The data collected will serve as a baseline to monitor the long-term effects of disturbance related to natural gas extraction on invasive plant abundance. The landscape fragmentation analysis as it relates to invasive spread is being explored as an invasion prediction model for this type of large-scale human disturbance. A greater understanding of how these new corridors through the landscape act as avenues for invasive plant encroachment is essential for creating best management practices to prevent future spread.