Unconventional natural gas development is rapidly proceeding in the United States, and elsewhere worldwide. The processes of extracting gas from deeply buried shale and other dense rock, and transporting it to market has impacted terrestrial and aquatic ecosystems. Pennsylvania alone will see the build-out of a projected 30,000 miles of natural gas pipelines over the next 20 years, fragmenting forests throughout the state. There is widespread concern that pipeline corridors represent likely avenues for the spread of alien and invasive plant species into areas currently dominated by native forests. To begin to understand the vegetation on existing pipeline corridors, a detailed assessment was conducted of a 1700’ long section of the Transco interstate pipeline in east-central Luzerne County, PA. Plants were identified and their percent covers estimated in forty-eight 1m2 quadrats distributed along three transects representing three ages of pipeline installation and mowing intensity during the summer of 2015.
One transect, above a pipeline constructed in the late 1950s, revealed a plant community dominated by Ericaceous subshrubs and native graminoids typical of acidic woods. Their combined Shannon-Weiner index was 2.8. The other two transects assessed the vegetation pipelines constructed in the 1970s and 1990s. One was mowed in late summer 2014, while the other was unmowed. Both were dominated by meadow species like wrinkled goldenrod, swamp dewberry, and common cinquefoil. The vegetation in the transect that was mowed displayed decreased goldenrod dominance the following year, compared to the transect in the unmowed vegetation. Their combined Shannon-Weiner indices were 2.0-2.1, indicating lower diversity. Thus vegetation in the pipeline ROW was affected by the age of the disturbance and mowing practice. Local low spots with saturated soils were dominated by wetland species such as soft rush and woolgrass. Vegetation samples transferred to a greenhouse and seed bank assessments revealed similar patterns, overall. The results showed unexpected species diversity and dominance by natives in this pipeline segment, indicating potential for smart ecological restoration in future pipeline restoration efforts.