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Shrubland Restoration
Shrublands are few and far between in the Northeastern United States. Even so, many species rely on these habitats for raising young and carrying out their life cycle. In the fall of 2016, I was lucky enough to be assigned to the task of expanding and restoring a shrubland on a preserve that I managed in Westchester County, New York. The area was an old blueberry field that had been encroached upon by various tree species including black cherries, red maples, and various birch trees. This page was created to describe the work that was done, and the mistakes that were made, in order to help others who want to create their own shrubland.
The first mistake that was made was during the initial decision on which trees to remove. Every tree in the area was marked to be cut down, and all of the trees were removed between November and March. By removing all of the trees, we were unable to secure the deer fencing needed to protect the young shrubs. This added more than two weeks of work to the project, and a lot of work hours with volunteers as we had to install posts to support the deer fencing (photo below). If we had girdled the trees, we could have used the remaining trunks for fence support.
A different option would have been to leave trees that could re-sprout after being topped (cut down to 6 to 10 foot tall). These trees could be trimmed back every few years to maintain the shrubland structure
and continue to support the deer fencing. Furthermore, the topped trees would add immediate shrubland structure to the habitat for nesting birds, while the rest of the area filled in with native shrubs like the blue berries.
The second mistake we made in fact occurred in the first steps, but it was not apparent until the following year. To prepare the site for volunteers, I worked with my boss to remove the invasive biomass which would impede our efforts cutting down trees. The majority of this work was done in late fall, following the best management practices outlined for each species. We spent a week mowing and weed whacking Japanese barberry (Berberis thunbergii) knowing that these shrubs would require future annual management to eventually remove the population. The annual maintenance for Japanese barberry was factored into future management plans. What I was unaware of was the amount of other invasive species in the seed bank.
By midsummer, invasive plants including Japanese stiltgrass (Microstegium vimineum), porcelain berry (Ampelopsis brevipedunculata), and mile-a-minute weed (Persicaria perfoliata) were the dominant species in the areas we removed Japanese barberry. All of these species require many more hours of work to control than Japanese barberry. These species added an extra 120 hours to the first year of maintenance to remove these invasives in an attempt to eventually rid the habitat of them, while letting the native plants colonize the restored shrubland. Successfully, during the first year, none of the Japanese stiltgrass, porcelain berry, or mile-a-minute vine were able to produce seed which means next year there should be a strong reduction in their populations. This phenomenon is common in restoration projects, where invasive species are able to colonize the disturbed areas from an existing seedbank. Sometimes, the species that will be a problem can be foreseen by doing a proper vegetation survey during the growing season before the project commences, allowing management plans to factor in hours needed to prevent establishment.
Managing these invasives also meant taking care in leaving the native plants which did establish. In the photo to the right, a small patch of golden rod can be seen, surrounded by a monoculture of invasive Japanese stiltgrass. A chemical free approach to control Japanese stiltgrass is to mow or pull it our right before it produces seed, as it is an annual. The monoculture was mowed down which is shown on the right side of the photo, while the area around the desired native plants had to be hand pulled.
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