Revegetating After Wildfires
Loss of vegetation leaves land vulnerable to increased runoff, erosion, and sedimentation; encourages weeds; degrades habitat; and impairs forest regeneration. Revegetation is a good step to take toward controlling noxious weed invasion after a wildfire. For more information about weed suppression, you could also contact your county weed coordinators. Reestablishment of permanent vegetation provides long-term erosion control, protection, and site stability. This practice is the least expensive per acre. It directly addresses the resource concerns, and it is best suited to addressing concerns over larger areas.
What Areas Need Revegetating?
In general, severely and moderately burned sites should be reseeded to decrease the likelihood of erosion and sediment movement down slopes, to discourage weed invasion, and to fulfill management objectives. Since lightly burned areas recover quite quickly from wildfire, reseeding is usually not necessary.
When Should I Plant?
Grasses and forbs should be planted after the wildfire or ground disturbance when the soil surface is loose. Seeding in late fall or winter (even if there are a few inches of snow) improves success. The prime time to seed is immediately prior to the ground freezing. Trees or shrubs should be planted in the fall or early spring when plants are dormant.
What Should I Plant?
Perennial grasses and forbs are slower to establish, but provide long-term cover for reseeded sites. Sites to revegetate with perennial grasses and forbs include severely burned sites and moderately burned sites that had populations of noxious weeds before the wildfire or that are less than 50 feet from a drainage channel. For example, slender wheatgrass is a native grass that establishes quickly and is moderately long-lived. Over time, as the slender wheatgrass begins to die out, other native species begin to fill in the site.
Annual ryegrass and small grains are useful when quick establishment is key; however, they only provide one year of protection. Revegetate with annual species where perennial grasses will recover naturally, including moderately burned sites with slopes greater than 15 percent. For example, winter wheat is a good option if native seed varieties are unavailable.
How Much Should I Plant?
Most seedings are broadcast with either aircraft or ground equipment. Landowners can seed small areas using a hand-crank seed broadcaster. You should use certified seed of a known variety to get the best results. If a specified variety is not available, be sure the seed originated within a 500-mile radius of your property. Be sure seed does not contain any noxious weeds. Contact the local NRCS, Extension Service, or conservation district office for recommended varieties or substitute species.
The seed mixes in the following charts are appropriate for areas west of the Continental Divide and foothills/mountains east of the Divide. Ideally, you should choose one to three of these species for a mix. The tables give the “pure-stand” seeding rates for each species expressed as pounds of pure live seed (PLS) per acre. To calculate a mix, divide the species rate by the number of species in the mix. Then, take the lbs/ac and multiply by the total acres to be seeded. Double these seeding rates on severely burned areas or steep slopes.
For example, if you are using a mix of three grasses to be seeded on 10 acres, divide the lbs/ac for each species by three and then multiply by 10. For slender wheatgrass the equation would be (12/3)10 = 40 pounds of slender wheatgrass in the mix.
Is There Anything Else I Can Do to Help the Planting?
Mulching will stabilize the soil surface to prevent movement of soil particles and loss of seed. Use straw or grass hay mulch or netting on small areas of steep slopes. Apply mulch at 70 lbs/1,000 sq. ft. (about 43 bales per acre). Use weed free material. Do not fertilize the first year. Hydromulching should be done in two operations. First, use a mulch-seed mixture to distribute the seed. Then, use the remaining mulch over the top to increase contact of seeds with the soil.
Keep your work well-maintained by repairing any spots of failure with new seed, plants, and mulch. Fertilize after the first year in spring until vegetation is well established.
What Seeding Rates Should I Use?
Zone 1 is made up of dry, warm sites consisting of open grasslands and woodland benches at low elevations on all aspects and on south and west-facing slopes at higher elevations. Woodland sites are dominated by dry Douglas-fir, limber pine, and ponderosa pine habitat types with a significant bunch grass component in the understory.
Zone 2 is made up of moist, warm sites consisting of moderate environments receiving more effective precipitation than the dry, warm sites. Zone 2 sites are found on north and east-facing slopes at lower elevations, on all aspects at mid-elevations, and on south and west-facing aspects at higher elevations. Sites are dominated by Douglas-fir and ponderosa pine habitat types.
Zone 3 is made up of moist, cool sites. Zone 3 sites are found predominantly on north and east-facing slopes at mid-elevations and on all aspects at high elevations. Sites are dominated by Douglas-fir with blue huckleberry in the understory along with Grand fir, western cedar, and western hemlock habitat types.
Zone 4 is made up of riparian areas including stream bottoms and wet meadows. These sites are subirrigated or wetter for at least a portion of each growing season.
More than 5,200 acres of private land were aerial seeded with slender wheatgrass in the Bitterroot Valley during 2000. Aerial grass seeding was very successful in most cases.
Some areas, such as stream banks and slopes around homes, were also hydro-seeded to provide immediate cover.