Shrubland Habitat Management - Bittersweet Success by Laura Mattei

Never underestimate the determination of oriental bittersweet. That’s just one of the many lessons that Sudbury Valley Trustees (SVT) has learned over the past three years as they have tirelessly worked to restore shrubland habitat at their Cedar Hill Reservation in Northborough, Massachusetts.

The project, funded by a Living Lands Biodiversity Grant, centered around a 20-acre patch of former pasture owned by SVT and surrounded by more than 2,500 acres of protected mixed forest, wetlands, fields and woodlands. The Cedar Hill Reservation presented a perfect opportunity to restore shrubland habitat for wildlife, particularly birds, that depend on these ephemeral habitats for foraging, nesting, and cover. 

Shrubland habitats were historically part of a dynamic landscape of diverse habitats maintained by wind, fire and floods and human activities such as farming, logging and livestock grazing. Today shrubland habitats are rapidly disappearing as they are developed or mature to forest in the absence of natural disturbance. As a result, the avian species that depend upon shrublands are experiencing greater declines than their forest counterparts. For example, half of the 10 most rapidly declining bird species in Massachusetts are shrubland species including the brown thrasher, eastern towhee, northern bobwhite, American kestrel and field sparrow. SVT’s plan was to restore this 20-acre degraded pasture in hopes of providing a refuge for this declining suite of bird species.

Battling Invasives

The Cedar Hill Reservation was being overtaken by an army of invasive shrubs and vines, such as honeysuckle, multiflora rose, Japanese barberry and oriental bittersweet. Native forbs and grasses were still common throughout but native shrubs were sparse.

SVT’s first plan of attack included a large Brontosaurus mower and a partnership with Mass Audubon Extension Service and the Massachusetts Division of Fisheries and Wildlife (MassWildlife). In the winter of 2005, SVT cleared several acres of invasives only to be astounded the following summer to see that bittersweet had exploded and carpeted more than 80% of the cleared area. Although they had anticipated significant regrowth, this was far beyond expectation.

Clearly a new strategy was in order. So, based on a recommendation from MassWildlife, SVT adjusted their plan to include an herbicide treatment, which they applied a year later in the Fall of 2006. In the meantime, they cleared additional acres of brush and collectively treated the cleared acres with herbicide. Although this treatment yielded results, it was not quite as successful as they were hoping for. Again, they went back to the drawing board for one last brainstorm, believing success was right around the corner.

Bringing in the Experts

Their final attempt involved pulling out all the stops. SVT found a contractor with invasive plant control and habitat restoration experience who offered a guarantee of 90 percent success within two years. The contractor applied herbicide last summer and will repeat the application again this year. To increase the effectiveness of the upcoming herbicide treatment, SVT mowed the area this spring and is eager—and hopeful—to see what success their efforts will bring next year.

Signs of Encouragement

The Cedar Hill Reservation project is a labor of love that has seen SVT through three mowing contractors, two herbiciding contractors, and innumerable management techniques. This tenacity is already starting to pay off as their latest breeding bird survey showed strong breeding densities of eastern towhees, and perhaps even more exciting, increased numbers of breeding blue-winged warblers, a result not expected for several years.

Although the path was long and sometimes frustrating, SVT has emerged with a new perspective on the value not only of perseverance but also of flexibility and adaptive management. They plan to continue to tweak their management plan with the hopes of one day supporting the full community of shrubland species at Cedar Hill Reservation—and better yet, have a successful template to apply to future projects.

Laura Mattei is the director of stewardship at the Sudbury Valley Trustees in Massachusetts.

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