Our Science and Stewardship Department is excited to move forward with a new phase of habitat management work within the Serengeti area on the north side of the Milestone Road. For many years, residents and visitors have enjoyed the wide-open vistas across this portion of the Middle Moors, thanks to grassland restoration and management work initiated here in 1998. The resemblance of this area to the plains of Africa has inspired its local nickname, the Serengeti, and led to the establishment of a small “herd” of African mammals (thanks to local artists and, most recently, the Nantucket High School woodworking and art departments). Before we talk about next steps for the management of this important conservation area, we’d like to review some of the adaptive management lessons we have learned and how we got to this stage in our grassland restoration work at this site.
Prior to management, the Serengeti (an approximately 472-acre area in the southern portion the Foundation’s Middle Moors property) was vegetated with tall, dense scrub oak shrubland intermixed with small patches of heathland and grassland. In 1996, this area became part of a habitat management project undertaken by the Nantucket Conservation Foundation, the Nantucket Golf Club, the Massachusetts Natural Heritage & Endangered Species Program and the Massachusetts Audubon Society. A Conservation Permit issued under the Massachusetts Endangered Species Act allowed for the construction of the golf club on land known to provide habitat for several state-listed species in exchange for funding provided for off-site grassland restoration work on protected conservation land.
The goal of the management work undertaken in the Serengeti under this permit was to restore rare sandplain grassland and heathland habitats to benefit several rare species, including northern harriers (a rare bird of prey) and other grassland-associated plants. The initial management consisted of repeated growing and dormant season brushcutting, beginning in 1998 and continuing at least every 1-3 years since then. Although this repeated, prolonged mowing management has resulted in a dramatic reduction in the height of scrub oak and other woody shrubs, there has been very slow colonization by herbaceous species such as grasses and wildflowers. Successful restoration of the natural mosaic of grassland and heathland habitats requires both a reduction of woody cover and an increase in herbaceous species richness.
To better understand the factors limiting restoration at this site, NCF’s Department of Science and Stewardship initiated two research projects, both spearheaded by our staff botanist, Kelly Omand. The first compared the viability of the soil “seed bank” (seed present in the soil and capable of germinating) at several sites across Nantucket, including the Serengeti area. Results confirmed that the seed bank at sites overgrown with tall, dense shrubland for extended time periods contained very few seeds of key sandplain grassland wildflowers and grasses, as compared to sites that currently support grassland and heathland habitats.
The second project, also undertaken in the Serengeti, assessed the effectiveness of mechanical disk harrowing followed by native seed addition as a grassland restoration technique. Results of this research conducted within a 2.6-acre experimental unit demonstrated that this management technique effectively disturbed the duff and mineral soil layers and broke up the roots of woody species, conditions which benefitted the germination and establishment of native gasses and other herbaceous species seeded into plots. Harrowing resulted in an open mosaic of grassland, heathland and multi-age scrub oak, promoting overall community species diversity. The results of this one-time treatment conducted in 2011 are still clearly visible both on the ground and in the most recent Google Earth satellite images taken in 2018 (see aerial photo above).
Results from both of these projects, as well as feedback provided by our colleagues at the Massachusetts Natural Heritage & Endangered Species Program, have been incorporated into our revised management plans for the Serengeti area. We are excited to now have an approved plan in place that will allow us to move forward with a new phase of management work for this area. This plan involves 1) reducing the overall mowing frequency across the site to benefit rare moths, shrubland bird species, native bees and pollinators and other wildlife and 2) restoring small patches of grassland and heathland habitat mosaic within mowing units using harrow management. These changes in management will be accompanied by research and monitoring to provide future learning opportunities.
The Serengeti area has been subdivided into fifteen designated units, with overall mowing management staggered across a 3-year rotation period, including a mix of summer growing season (after August 1st, to avoid impacting nesting birds) and dormant season management. Some of the units currently managed as protective firebreaks will continue to be mowed annually, others will be managed on a 2-3-year staggered rotation schedule and sites that have never been mowed will remain unmanaged. These changes are proposed to maintain these open habitats while creating a mosaic of different stages of vegetative growth across the site to increase overall biodiversity and benefit rare wildlife.
Additionally, experimental disk harrow subunits (< 2.5 acre each) will be incorporated within units managed with mowing. These harrow subunits will be irregularly shaped and strategically located adjacent to established patches of native grasses that can serve as a seed source. Disk harrowing will be a one-time treatment. In total, approximately 10% (or ~ 47 acres) or less of the entire Serengeti area will be harrowed across a 3-5-year period. When available, seed of locally collected, common native sandplain grassland/heathland associated graminoids and forbs will be added via patch seeding to assist with grassland habitat restoration.
This past summer, we sampled vegetation monitoring transects and completed photo-monitoring within 4 management units in the Serengeti to get us started with this project. Two of these units were mowed at the beginning of August and the other two will be mowed during the early winter. Later this winter, 2 subunits within each of these mow units will be treated with disk harrowing and patch seeding with native seed. Over the next several years, we will be resampling vegetation monitoring transects and re-taking site photos to monitor the restoration progress, as well as installing additional harrow management subunits as future rotational mowing takes place.
Prior to initial management in 1998, the Serengeti site contained a large monoculture of mature scrub oak shrubland. Although this habitat type is ecologically significant, it is one of the most common habitat types on Nantucket Island. In contrast, sandplain grasslands and heathlands are much rarer and support a wide variety of plant and animal species. A great deal of time and funding has already been expended on habitat restoration efforts on this particular NCF-owned property. The management changes proposed in this plan are aimed at taking advantage of the long history of previous restoration work, utilizing results from successful Foundation-published research and incorporating newer management techniques. Two of the units that will be harrowed this coming winter are visible from the Foundation’s newly-established Milestone 4 to Altar Rock walking trail, so you can monitor the progress of this project while going for a walk and enjoying our conservation lands!
The Nantucket Conservation Foundation is a private, non-profit land trust that depends on contributions from our members to support our science projects, conservation property acquisitions and land management efforts. If you are not already a member, please join us now! www.nantucketconservation.org