Smith Habitat Management
Habitat Restoration and Invasive Plant Control
The Smith Conservation Land has outstanding conservation values: It hosts multiple habitat types, provides habitat for a rare turtle, contains three high-quality vernal pools, is part of a regionally significant habitat corridor, and is considered a high priority area for protection by the state’s BioMap2 ranking system designed to guide land managers in strategic biodiversity conservation in Massachusetts. The property has become a popular destination for area residents and visitors.
Unfortunately, the property also hosts a great diversity of aggressive invasive plants. Most notably, Oriental bittersweet has spread across 22 acres of this 54-acre conservation land. The invasive plants here severely compromise the habitat values of the site.
Oriental bittersweet in particular strangles trees and overwhelms and displaces all other vegetation in its path. If left unmanaged, the bittersweet will continue to damage the land, overcoming and killing trees and other vegetation, creating a void of healthy habitat as well as producing abundant seed sources that birds can continue to spread across the land.
The loss of diverse native vegetation poses a real and present risk to the land and to the animals dependent on diverse plant life for their survival. Invasive plants are well-documented to be the second greatest threat to biological diversity, second only to habitat destruction. SVT’s goal at the property is to restore high quality, diverse habitat in the areas that have been damaged by Asian bittersweet.
The restored areas will be home to a diverse collection of native plants, which, in turn, will support a myriad of wildlife, birds and native pollination systems. Native pollinators are increasingly at risk due to the direct loss of habitat, conversion of habitat to other uses, and invasion of non-native plants. Many native pollinating insects are specialists that simply cannot utilize invasive plants. In turn, the majority of local bird species need an abundance of caterpillars to feed their young during nesting season and studies have shown that invasive plants do not support the abundance of insect food needed by birds.
At Smith Conservation Land, there is an additional issue of a red pine stand that is dying out and has become both a safety hazard as well as a breeding ground for aggressive growth of Oriental bittersweet (see photo at right). Smith hosts another monoculture of European tamarack that is equally invaded by bittersweet. This tamarack is not native and – as with all monocultures – it is at greater risk of disease and insect pests especially in a changing climate.
Oriental bittersweet is well-documented to be difficult to control due to its extensive, networking root system and aggressive resprouting capabilities. While small infestations can be effectively controlled with repeated hand-pulling and mechanical removal over multiple years, it is impossible to control Oriental bittersweet with mechanical methods over large areas. Compounding the problem, mechanical removal will increase root growth and sprouting unless the entire plant and root system is removed or the cutting is frequently repeated during the growing season. Complete root removal entails a severe level of soil disturbance, which in itself can foment invasive plant germination and growth and will impact the soil microbial ecosystem.
At Smith Conservation Land, SVT has concluded that the limited and targeted use of state-approved herbicides is the most effective solution to controlling Oriental bittersweet while also limiting the risk to human or environmental health.
SVT had originally proposed to initiate the invasive plant control project at Smith Conservation Land in Fall 2019, but paused the project after neighbors expressed concerns about the proposed use of herbicides as part of the project. SVT wanted to ensure that our approach was, in fact, the most prudent and effective approach to invasive plant control that would not endanger the health of people, wildlife or the environment.
Over the course of the past year, SVT conducted extensive research on the potential human health and environmental risks of herbicides and on the feasibility of non-chemical controls. SVT convened a working group composed of representatives of statewide conservation organizations and agencies (including The Nature Conservancy, Mass Audubon, The Trustees, Native Plant Trust, MassWildife, the Massachusetts Natural Heritage & Endangered Species Program, and the Massachusetts Department of Conservation & Recreation’s Water Supply Division) to explore and share resources and best practices. SVT also hired an ecologist with extensive experience in the subject to conduct an updated review of literature and documented best practices.
1. The testing and review of the herbicides by regulatory authorities, which includes additional review in Massachusetts by the Department of Agricultural Resources (MDAR), are designed to be conservative such that the maximum allowed usage of an herbicide will not pose a risk to human health and the environment. The Massachusetts Department of Public Health is also involved in the review process. SVT and our partners have conducted due diligence in taking a closer look at the science as well as the practices and the results. SVT firmly believes that limited use of herbicides will yield a net benefit to the habitats and not endanger human health.
2. In invasive plant management, the amounts of herbicide that are used are well below the maximum-allowed application rates and the methods of application are focused on the target plants, further assuring that the risk posed to human health or the environment is extremely low.
3. SVT hires state-licensed applicators with experience in natural areas management and only applies herbicides approved for use in sensitive areas. Cut and dab application is the primary application method. Treatments that utilize back pack sprayers allow the operators to very specifically target only the invasive plants and avoid non-target impacts.
4. The methodology that SVT is proposing to use is a Best Management Practice (BMP) for conservation land managers. The BMP includes a combination of mechanical and herbicide treatments and is used by all of the statewide conservation organizations and agencies engaged in land management as well as many regional and local land trusts and municipalities.
5. The Massachusetts Natural Heritage & Endangered Species Program (MNHESP) has formally approved SVT’s management plan for the Smith Conservation Land. MNHESP reviewed the plan because the site supports vernal pools and a rare turtle species.
6. The Littleton Water Department recently issued a statement that SVT’s proposed approach is not a threat to the community water supply.
THE MANAGEMENT PROPOSAL
In honor of a request from the Littleton Select Board, made on December 7, 2020, SVT will postpone any herbicide applications until 2021.
In response to neighbors’ concerns and restrictions imposed by the Conservation Commission, SVT has reduced the area across which herbicides will be used.
SVT will maintain the following mechanical-only (no chemical) control areas:
- 125-foot buffers around residential water wells. SVT increased this buffer by 25 ft in response to a request from the neighbors.
- 100-foot buffers from wetland boundaries.
- 200-foot buffers from vernal pool margins (100 ft more than conservation commission jurisdiction).
- 50-foot buffers from residential activity areas for those neighbors who wish to have this additional setback.
In buffer areas, SVT will only use mechanical controls in an attempt to prevent the bittersweet from going to seed and to attempt to keep the vines from spreading onto the treated habitats. In the meantime, SVT is committed to continuing to research non-chemical control methods such as the root-extraction technique that has been used by an Acton resident and that has shown promising results on small areas.
Outside of mechanical-only control areas, SVT will use herbicides to treat bittersweet vine in the red pine stand (Unit 1), the mixed Norway Spruce/old field area (Unit 3), and a few areas with large bittersweet vines in portions of Units 4 and 5. These areas occupy approximately 11.3 acres and can be viewed on the accompanying map. SVT had originally proposed herbicide treatment in Unit 2 – the European Larch stand - but that is now much less feasible with the wetland buffer restrictions; SVT will likely delay management in that area.
In the treatment areas that are beyond the buffer areas, SVT will conduct a cut stump treatment with a triclopyr-based herbicide in late fall. Licensed applicators will use chain saws and hand saws to cut the larger bittersweet stems and then apply the herbicide to the cut stem with a handheld applicator. In the following summer, a spot spray treatment will be conducted to control low-growing dense bittersweet (whose stems were too small to cut and dab) and any resprouts from bittersweet roots. The water-based mix contains triclopyr and metsulfuron methyl. The treatments will utilize back pack sprayers that allow the operators to very specifically target the invasive plants and avoid non-target impacts.
These follow-up treatments are much smaller in area and in volume of herbicide used compared to the initial cut and dab. Additional follow-up summer treatments will be conducted ONLY as needed to control any resprouting bittersweet. Backpack spraying would be limited to three applications at maximum. Hand-pulling seedlings will be conducted in between treatments. As noted above, all treatments will be conducted by licensed applicators experienced in treating natural areas.
It is important to emphasize that the method of spraying is very limited and controlled to patches of leaves. It is not aerial spraying nor boom spraying. The very limited use of herbicides will be more effective and will help us achieve a level of control whereby we can later switch to mechanical only.
SVT have observed the use of the backpack sprayers and has been impressed with the very low level of non-target impacts. The pressure in the backpack sprayers is adjustable. The sprayer wands apply the treatment in a narrow angle and flat fan pattern, so the applicator can be very directed at small targets, especially with lower pressure. Our applicator states that “Since we generally get rather good control in the first cut stump treatment, the amount of herbicide applied in follow-ups is very small in comparison.”
As we eliminate the invasive species and encourage the growth of native plants, including application of native plant seed mixes in some areas, then the native plants will gain an advantage and be able to compete with the bittersweet as long as we continue with regular manual control. That manual control goes on for many years because of the seed bank of bittersweet.
SVT is dedicated to preventing invasion of the healthy forest habitat to the west by using hand pulling of bittersweet and other invasive plants along the woodland edge. In the mechanical-only areas, SVT will use hand removal technique as much as is possible, utilizing staff and volunteers. Goats may be used to keep some areas open.
SVT will mow in open areas. The mowing will increase bittersweet root growth, but will keep it from going to seed and climbing trees. We will hire a contractor to mow down bittersweet and trees consumed by bittersweet in the southeast corner of the property and then we will keep those additional areas mowed.
We will continue to adapt our approach as we see what works (and what doesn’t) as we strive to restore the ecological treasure that is the Smith Conservation Land. Throughout, we will continue to keep interested parties informed.