Practice Description
The planting of vegetation in disturbed areas, either to establish desirable plant communities or to minimize erosion (or both). The practice of establishing desirable plant communities will typically either be associated with focused habitat restoration or with mitigating a disturbance on the landscape. Using vegetation to minimize erosion is a common practice associated with many types of land management. Revegetation is usually achieved through seeding, but direct planting can be appropriate in certain situations.
Under Practice Variations and Methods is a special section which discusses considerations for Municipalities related to closure plans for gravel and other large-scale projects.
Associated practices
- Soil Exposure: Soil preparation, and in some cases the removal of duff or other organic material, can be an important practice to set the stage for a successful Revegetation project. Especially in situations where the parent material is a poor, droughty soil appropriate to support a barrens or sandplain grassland community, but is covered by a layer of duff or litter.
- Invasive Plant Control: Competing vegetation can be a complicating factor when attempting to establish a community through seeding.
Methods
- Erosion Control: The intention of erosion control is to quickly stabilize a disturbed are in order to reduce or eliminate soil erosion. This is often accomplished through seeding or planting, with the result being the establishment of well-rooted vegetation that will keep soil in place. There are many quick-establishing plant species that can stabilize soil, but great care should always be taken to ensure that the proper species is used in the proper situation. A few considerations are as follows.
- When seeding a disturbed area, think about both the short and the long-term conditions of the site. Using a quick-germinating, non-reproductive crop to initially stabilize the site is important to not only reduce erosion, but also ensure that you’re not establishing an unwanted species to the site. A sterile annual crop like winter rye or jerry oats is often great for this purpose. For a longer-term solution, mix in a more permeant cover crop to your mix, based on what the site can support and your overall goals. For example, in poor soil sites, a seed mix of jerry oats and little bluestem (a desirable perennial species that can take a year to establish) will provide both immediate and long-term stabilization. The establishment of non-native plant species should always be avoided.
- Work with the parent soils. Often there is no need to bring in soil to support plant species for erosion-control. Instead, find seed mixes designed for the exposed soils at the site. Bringing topsoil to a site dramatically changes what natural communities and associated species a site can support, and often drastically reduces the biodiversity at a site.
- Avoid plastic erosion control mesh whenever possible. This material is lethal to small animals (birds, reptiles, etc.) when they become entangled in the mesh. Even mesh designed to quickly degrade in sunlight can persist for several years.
- Longer-term erosion issues (and their solutions), like the erosion caused by denuded stream banks, will require a more complex approach to both immediately secure the site and to ensure its proper ecological function into the future. Because of this complexity – as well as wetland protection regulations – consultation with experts should always occur. A delicate balance in these situations needs to be struck between achieving stabilization and allowing for natural processes (like meandering) to continue.
- Revegetation: The first questions that should be addressed whenever considering a revegetation project are what are the desired conditions of the target area, followed by, which plant species (or plant community) is most appropriate for the situation. The answer to these questions should always be related to what vegetation the site can support, the goals of the greater project, as well as any limitations that may be anticipated for the project. Typically, the general conditions of a revegetated area will be related to such factors as desired structure (ex. grassland, shrubland, woodland, forest), ecological goals, expected management need/capacity, and other limiting factors (ex. deer browse, invasive competition, etc.). Choosing a species or natural community will be greatly dependent upon site conditions, especially soil characteristics and hydrology. In most cases it will be much more appropriate to work within the parameters of a site’s inherent conditions than to try to alter the site’s characteristics to accommodate an otherwise incompatible species or community. The following are select considerations related to Revegetation:
- The Extant Seedbank: The extant seed bank can often naturally provide an excellent native seed source. Many sedges and specialized forbs can lay dormant in the seedbank for decades (or longer), and will then densely germinate once the surface soil has been disturbed. This is especially true in wetlands and in fire-influenced natural communities. Taking advantage of this situation not only can save a great amount of time and project resources, but relying upon the seedbank to revegetate an area can also result in an expression of a site’s historic natural community, the preservation of very local genotypes, and may also provide some unexpected specialists and rarities.
- Seeding vs. Planting: In general, it’s best to seed when revegetating large areas or establishing a base of key species. Seeding – as opposed to direct planting – allows for the introduction of significantly more individual plants onto an area, greatly reduces cost and effort, and usually results in far greater establishment. However, there are situations where direct planting is desirable, especially when establishing woody species that are difficult to establish by seed and that need a headstart over competing extant vegetation, or in stabilization projects such as dune restoration where plugs are the only practical means of quick establishment.
- What to Seed: While it’s tempting to seed an entire suite of species during a natural community restoration project, it’s usually best to begin by establishing a base planting consisting of just a few keystone species. For example, when establishing a Sandplain Grassland community, seeding the area to only little bluestem at first is often recommended. This will help to quickly establish the foundation of the community, and in time, complimentary species will often pioneer into the community on their own, often through the seedbank. If, in time, desired complementary species have not established on a site, a light overseeding or planting the plugs of those species may be considered.
- Choosing Stock: As mentioned above, matching species that are appropriate to the site’s edaphic, hydrological and chemical conditions are critical. Also very important is the use of local genotypes when selecting source material. In Massachusetts, using source material from southern New England or eastern New York is acceptable for widespread species. For highly specialized species and rarities, obtaining source material from the within 20 miles of the restoration unit (and preferably closer) should be the objective.
- Closure Plans: Projects such as sand mines and large-scale solar fields provide excellent opportunities to impact conservation once these projects come off-line. A well-designed closure plan is an important tool in ensuring that the footprints of these areas provide positive and lasting contributions to biodiversity. Traditionally, closure plans have often focused on simply “greening” a site once it is closed, usually by spreading topsoil over the disturbed areas and establishing turf grasses. Though well-intended, these actions essentially result in the project areas becoming void of meaningful biodiversity. Instead, officials and regulators are encouraged to think more holistically about how a closed site is managed; especially by taking into account a site’s soil characteristics and emphasizing opportunities to protect these values.
Often, this more holistic approach is much simpler for both the project proponent and the regulator to design, execute and maintain than the traditional “greening” of a post-closure site. Specifically, all sand mines and many large-scale solar fields are sited on poor mineral soils: the exact resource that is so important to so many species of conservation interest. Areas of exposed mineral soil are a necessity to a very large suite of highly specialized and often declining invertebrates, especially pollinators. The natural communities that develop on these poor sites are also critical to many species of birds, reptiles, and specialized plants. Covering this sand with topsoil and establishing dense turf grasses will essentially eliminate the important and highly specialized elements of biodiversity that could occur in these settings, while also creating unnecessary expense and complexity to a closure plan.
Closure plans need to be site specific, but in general, some considerations for closure plans (especially for sites on poor soils) are as follow:- Parent Material: While poor, sandy soils are often seen by the general public as unproductive and in need of amendment, the reality is that these soils are incredibly important to local and regional biodiversity. Leaving the parent material at a site exposed will allow for continued use by the specialized species that depend upon these features, and also allow for natural succession to add further structural and species diversity to the site. Often, natural succession in poor sites will lead to the establishment of rare natural communities, such as sandplain grassland and other barrens expressions.
- Stabilization: While exposed parent material is often a great benefit from an ecological perspective, there are situations where erosion occurs and needs to be addressed. In many cases, this can be achieved by simply grading steeper areas to gentler grades. In cases where more direct stabilization needs to occur, localized solutions can be applied that don’t compromise the greater ecological integrity of the site, like the establishment of physical barriers (sloughs, water bars, or armoring) or targeted plantings.
- Seeding: Plantings are typically not encouraged in poor sites because (a) exposed mineral soil is important from an ecological perspective; and (b) sites will naturally revegetate themselves from the native seed bank, often with interesting and unexpectedly welcome species. And even before plant species establish at a site, the soil will begin to naturally stabilize through the establishment of biological crusts (dense communities of micro-fungi, lichens, and mosses). However, in some cases, giving the community and its stabilization a head start can be a benefit, and in these instances, a light overseeding of little bluestem (~5lbs/acre) is advised. There is usually not a need to add additional species to a seeding.
- Water Table: Especially in retired sand mines, an element of exposed hydrology can be incredibly productive from a specialized biodiversity perspective. In situations where the floor of a mine is already near the water table, including areas in a closure plan that are scraped down to intersect with the water table creates seasonally wet sand that will often self-populate with interesting plants (many with bog affinities) and uncommon invertebrate assemblages.
- Management: The natural communities that establish on poor sites are disturbance dependent, and without some form of management, will eventually succeed into a more generalist and climax type community. But because the sites are often so poor and are starting from a non-vegetated state, this succession can take many years. In the meantime, an entire gradient of important communities can establish and shift over time and space, providing critical habitats for some of the state’s most vulnerable species. With this in mind, all closure plans should identify the desired target natural community and structure to be maintained, as well as a plan of how to achieve this, and who is responsible for the maintenance. Often the project proponent can be identified in the special permit to be the party responsible for maintaining the site in its desired condition post-closure. Plans should be clear about the desired resulting community and should be adaptive in how to achieve this condition. Mowing, invasive control and even prescribed fire may be appropriate considerations to achieve the long-term condition of a site.
- Long-term Protection: Sand mines and large-scale solar arrays are often viewed by the public as permanent losses of open spaces and their associated natural resources, but these proposals can also be viewed as temporary changes to the land that can facilitate the long-term conservation of a site. The key to achieving a positive outcome in these situations is to not only develop a thoughtful, site-specific closure plan that takes advantage of the site’s composition, but also ensuring the long-term legal protection of that site through the special permit process. One way to achieve this is to make the recording of a Conservation Restriction on the site a requirement of the permit. Under this scenario, a proponent is allowed to move forward with their project in exchange for the permanent protection of the site once the life of the project has ended. This can work extremely well for sand mines (a spent sand mine can become a near instant biodiversity hotspot) and solar arrays (as long as the permit addresses such considerations as non-anchored arrays and the preservation of the parent material).
Frequency
As needed.
Additional resources
Coming soon