Prescribed fire is an important management tool for maintaining healthy stands of native prairie or dense nesting cover. For thousands of years, the North American prairies were subject to natural fires caused by lightning or intentional fires set by Native Americans for hunting, pest management, warfare, and range management. Fire reduces above ground biomass and releases nutrients essential for sustaining the productivity of native prairie and enhances species richness and diversity. It also sets back invading trees and shrubs.
Managers at Bowdoin NWR occasionally perform carefully planned and controlled fires to manage wildlife populations and habitat. Controlled burns are often called prescribed burns because managers write a careful prescription based on the biological outcome or management goal for a particular unit, and also take into account the weather conditions, equipment, and people necessary to safely conduct a burn. Records show that before settlement the prairies around the Bowdoin area probably burned every 10-15 years. Ideally, wildlife managers try to mimic historic burn cycles in order to restore or maintain native prairie areas. Lack of periodic burning of native prairie is one of the main reasons for the overall decline of plant and animal diversity.
Grazing and haying are two management tools used to rejuvenate upland, and in some areas, wetland habitats. Grazing can be done on both native grasslands and tame grasslands. Some dead and decaying plants from previous year's growth are necessary for shelter, escape cover and nesting habitat for many birds and animals. Too much of this dead plant material inhibits new plant growth, reduces plant productivity, is less attractive to nesting birds, and makes travel difficult for newly hatched birds and young animals. Typically, managers use cattle on areas for short, intense intervals to mimic the effects bison had on prairie plants and to renew plant growth. Grazing also benefits the participating landowners by providing additional forage for their cattle operation.
Haying is another technique used to rejuvenate tame grassland areas. Tame grasslands are areas once cultivated and now restored to a mixture of domestic grasses and legumes, or what is called dense nesting cover (DNC). DNC is normally easier and less expensive to establish than native grasses. It is also a good alternative for restoring uplands until it can eventually be seeded back to native grass species. DNC makes excellent nesting cover for many bird species, but needs to be rejuvenated every 3-4 years. Haying clears the field of standing dead vegetation, which becomes too thick for nesting birds. Periodic removal of the dead vegetation allows the underlying grasses to rejuvenate into a healthy upright stand of nesting and escape cover. Like grazing, haying also benefits the participating landowners with additional forage for their livestock.
There are numerous habitat management tools that can be used to manage natural, restored, and created wetlands effectively. Natural wetlands regularly go through wet (flooding) and dry (drawdown) cycles. When natural flooding and drawdowns are not possible, the manipulation of water levels in wetlands can be used to mimic natural wetland cycles and to manage wetland vegetation on created and enhanced wetlands. Periodic drawdowns are important to the health and productivity of a wetland by releasing nutrients bound up in the soil and the vegetation, which upon reflooding, once again become available for aquatic plant and animal growth. These dry cycles are essential for many wetland plant seeds to germinate, providing more food for waterfowl. Wetland plants also provide habitat for aquatic invertebrates, a very important protein food source for waterfowl and shorebirds.
While driving around Bowdoin NWR you may notice a number of wetlands that are filled in by cattails. Cattails are a very recognizable aquatic wetland plant that provide excellent cover and nesting habitat for certain wildlife. However, in some cases cattail stands will fill in a wetland until it is the only plant growing, choking out all other aquatic plant species. Cattails can create a dense mat of dead and standing vegetation with no open water, making it unusable for a variety of wildlife. Occasionally, these cattail stands need to be manipulated or removed to open up the wetland for wildlife use and allow other vegetation to grow. This can be done in a number of ways. Perhaps the easiest way is through water level manipulation. One can actually flood out or drown cattails; to do so the water level should be held at 3-4 feet for an extended period of time. The stand can also be burned to remove standing vegetation then, using farming equipment, disced to dig up the root system. With enough root disturbance, discing can set back cattail regrowth. Grazing by cattle is another option; cattle will eat and stomp the vegetation, creating open water areas in the wetland. Another option to control cattails is through the use of chemicals. Spraying the stand with an aquatic glyphosate-based herbicide under particular conditions will kill the cattails, and the dead plant material eventually falls and decomposes, opening up the wetlands for wildlife use and growth of aquatic vegetation.
Invasive Species Control
Most invasive plants are non-native species that become established and spread, free from their natural competitors. Some invasive plants are also designated as “noxious” which means they have been determined to be major problems in agricultural and rangeland ecosystems. The Bowdoin WMD has several species of plants that are categorized as noxious by the state of Montana and include: leafy spurge (Euphorbia esula), spotted knapweed (Centaurea maculosa), Canada thistle (Cirsium arvense), yellow toadflax (Linaria vulgaris), field bindweed (Convolvulus arvensis) and perennial pepperweed (Lepidium latifolium). Other invasive plants occurring within the Bowdoin Complex but which are not currently on the state noxious weed list are: Russian olive, cattails, crested wheatgrass and phragmites.
As a federal agency, the U.S. Fish and Wildlife Service is mandated to control pests designated as noxious and/or pests that interfere with management objectives. Russian olive, cattails and crested wheatgrass are not considered noxious but they invade wetland and native prairie areas, degrading habitat and creating management and maintenance problems.
Bowdoin NWR uses integrated pest management (IPM) to control invasive species. IPM is a process that uses knowledge of pest biology and combines biological, cultural, mechanical and chemical tools in a way that minimizes economic, health and environmental risks. For example, leafy spurge on the Refuge is controlled with a combination of mowing and herbicide application while cattails can be controlled by discing or a combination of fire and herbicide application.