Post fire seeding
Encyclopedia
Wildfires consume live and dead fuels, destabilize physical and ecological landscapes, and impact human social
and economic systems. Post-fire seeding was initially used to stabilize soils. More recently it is being used to recover post wildfire plant species, manage invasive non-native plant populations and establish valued vegetation compositions.
after wildfires burned through fire prone foothills
and alluvial fans developed with homes. Although recent studies confirm that the probability of flooding and debris/mud flows significantly increase following a wildfire and that rainfall intensity, burn severity and ground cover reduction accounts for most hillside erosion, post fire seeding is not the most effective treatment.
A review of 37 publications and 25 monitoring reports on soil stabilization seeding discovered that less than half showed any reduced sediment movement with seeding. Seeding was not found to be effective in increasing cover or reducing sediment yields on burned areas in the Colorado Front Range
compared to controls, even for storms with return periods of less than one year. A comparison of commonly used soil stabilization treatments found that wood and straw mulch reduced water erosion rates by 60 to 80%, contour-felled log erosion barriers 50 to 70%, hydromulch 19% and grass seeding had little effect the first year during low intensity rainfall events and all were relatively ineffective in high intensity rainfall events. Vegetation cover from supplemental seeding was not significantly different from natural vegetation recovery.
. After the Railroad Fire in Utah
, neither seeded (drilled or aerial) or unseeded areas showed significant signs of wind erosion or deposition as evidenced by little difference (<2mm) in the height of washers on erosion measurement stakes.. Soil wind erosion was observed to have been moderated to some degree after the Command 24 Fire in Washington by natural site recovery alone..
Some recent comparison studies provide early evidence on seeding’s contribution to overall post wildfire recovery. A study at Mesa Verde National Park
compared seeded burned areas with unseeded burned areas and unburned areas and found that seeded burned areas had significantly less non-native plants than unseeded burned areas but significantly more than unburned areas except there was no significant difference in cheatgrass (Bromus tectorum) between seeded or unseeded burned areas.. In northwestern Nevada
from 1984–1997 cheatgrass density was altered by changing the seeding rates of a variety of native and non-native perennial grass and forb seed mixes. Cheatgrass densities were reduced to 2.6 plants per sq. m with seeding rates of 22.5 – 25 PLS per sq ft. Cheatgrass densities of 4.07 and 3.58 plants per sq. m were obtained with seeding rates of 10 and 35 PLS per sq. ft., respectively. On three burned areas in Colorado
and New Mexico
where native grass seeding was hand, drilled or aerially applied, there was a positive relationship between native species richness and non-native species cover and negative relationship between dominant native plant cover and non-native species cover. In a Utah study, all native perennial seeded plots had lower cover of annual species than unseeded plots; however, by the third year following seeding there was little change in seeded native species density, but the density of annuals more than doubled with cheatgrass and three annual forbs making up the majority of plant density . A California grassland study found that regardless of the treatment, exotic annual and native perennials were able to coexist; neither extirpated the other: exotic annuals persisted in plots to which native perennials had been added and vice versa.
It is possible that native plant seeding subsidies are not actually needed. Great Basin
native big squirreltail (Elymus multisetus) appears to has evolved competitive advantage traits in the presence of cheatgrass.
have been observed from post fire seeding. Seed mixes, even “certified weed free” seed mixes, have been contaminated with invasive species and initiated new infestations. Successful growth of seeded grasses (i.e., enough to affect water erosion) have displaced native or naturalized species, including shrub and tree seedlings. Seed bed preparation and the seeding process has facilitated the growth and expansion of naturalized non-native species. The machinery used in landscape seeding operations (e.g., drill seeders and chains) impact surviving native plants and disturb microbial soil crusts.
seeded burned areas exacerbates the problem of non-native annual grass invasions, even when conducted after a two year hiatus. Historic post logging
seed treatments had a significant influence on the effectiveness of post Rodeo-Chediski fire
seeding.
Social
The term social refers to a characteristic of living organisms...
and economic systems. Post-fire seeding was initially used to stabilize soils. More recently it is being used to recover post wildfire plant species, manage invasive non-native plant populations and establish valued vegetation compositions.
Water erosion
Post fire seeding evolved from a desire to stabilize hillslope soils in hilly terrain after a wildfire and prevent downstream flooding and debris/mud flows. The assumption being supplemental seeding immediately after a wildfire would provide vegetation cover lost in the wildfire. Some of the earliest seedings were in Southern CaliforniaSouthern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
after wildfires burned through fire prone foothills
Foothills
Foothills are geographically defined as gradual increases in elevation at the base of a mountain range. They are a transition zone between plains and low relief hills to the adjacent topographically high mountains.-Examples:...
and alluvial fans developed with homes. Although recent studies confirm that the probability of flooding and debris/mud flows significantly increase following a wildfire and that rainfall intensity, burn severity and ground cover reduction accounts for most hillside erosion, post fire seeding is not the most effective treatment.
A review of 37 publications and 25 monitoring reports on soil stabilization seeding discovered that less than half showed any reduced sediment movement with seeding. Seeding was not found to be effective in increasing cover or reducing sediment yields on burned areas in the Colorado Front Range
Colorado Front Range
The Colorado Front Range is a colloquial geographic term for the most populous region of the state of Colorado in the United States. The area is located just east of the foothills of the Front Range, aligned in a north-south configuration on the western edge of the Great Plains, where they meet the...
compared to controls, even for storms with return periods of less than one year. A comparison of commonly used soil stabilization treatments found that wood and straw mulch reduced water erosion rates by 60 to 80%, contour-felled log erosion barriers 50 to 70%, hydromulch 19% and grass seeding had little effect the first year during low intensity rainfall events and all were relatively ineffective in high intensity rainfall events. Vegetation cover from supplemental seeding was not significantly different from natural vegetation recovery.
Wind erosion
In arid communities post fire seeding is attempted to reduce wind erosion and deposition. There is little objective evidence that supplemental seeding is any better than natural vegetation recovery from the post fire seedbankSeedbank
A seedbank stores seeds as a source for planting in case seed reserves elsewhere are destroyed. It is a type of gene bank. The seeds stored may be food crops, or those of rare species to protect biodiversity. The reasons for storing seeds may be varied...
. After the Railroad Fire in Utah
Utah
Utah is a state in the Western United States. It was the 45th state to join the Union, on January 4, 1896. Approximately 80% of Utah's 2,763,885 people live along the Wasatch Front, centering on Salt Lake City. This leaves vast expanses of the state nearly uninhabited, making the population the...
, neither seeded (drilled or aerial) or unseeded areas showed significant signs of wind erosion or deposition as evidenced by little difference (<2mm) in the height of washers on erosion measurement stakes.. Soil wind erosion was observed to have been moderated to some degree after the Command 24 Fire in Washington by natural site recovery alone..
Ecological stabilization
Seeding especially with native seed mixes is increasingly being proposed to recover post wildfire plant species, manage invasive non-native plant populations and establish valued vegetation compositions. Compared to seeding for soil stabilization, ecosystem recovery and restoration is far more complex and take several decades to fully evaluate.Some recent comparison studies provide early evidence on seeding’s contribution to overall post wildfire recovery. A study at Mesa Verde National Park
Mesa Verde National Park
Mesa Verde National Park is a U.S. National Park and UNESCO World Heritage Site located in Montezuma County, Colorado, United States. It was created in 1906 to protect some of the best-preserved cliff dwellings in the world...
compared seeded burned areas with unseeded burned areas and unburned areas and found that seeded burned areas had significantly less non-native plants than unseeded burned areas but significantly more than unburned areas except there was no significant difference in cheatgrass (Bromus tectorum) between seeded or unseeded burned areas.. In northwestern Nevada
Nevada
Nevada is a state in the western, mountain west, and southwestern regions of the United States. With an area of and a population of about 2.7 million, it is the 7th-largest and 35th-most populous state. Over two-thirds of Nevada's people live in the Las Vegas metropolitan area, which contains its...
from 1984–1997 cheatgrass density was altered by changing the seeding rates of a variety of native and non-native perennial grass and forb seed mixes. Cheatgrass densities were reduced to 2.6 plants per sq. m with seeding rates of 22.5 – 25 PLS per sq ft. Cheatgrass densities of 4.07 and 3.58 plants per sq. m were obtained with seeding rates of 10 and 35 PLS per sq. ft., respectively. On three burned areas in Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
where native grass seeding was hand, drilled or aerially applied, there was a positive relationship between native species richness and non-native species cover and negative relationship between dominant native plant cover and non-native species cover. In a Utah study, all native perennial seeded plots had lower cover of annual species than unseeded plots; however, by the third year following seeding there was little change in seeded native species density, but the density of annuals more than doubled with cheatgrass and three annual forbs making up the majority of plant density . A California grassland study found that regardless of the treatment, exotic annual and native perennials were able to coexist; neither extirpated the other: exotic annuals persisted in plots to which native perennials had been added and vice versa.
It is possible that native plant seeding subsidies are not actually needed. Great Basin
Great Basin
The Great Basin is the largest area of contiguous endorheic watersheds in North America and is noted for its arid conditions and Basin and Range topography that varies from the North American low point at Badwater Basin to the highest point of the contiguous United States, less than away at the...
native big squirreltail (Elymus multisetus) appears to has evolved competitive advantage traits in the presence of cheatgrass.
Unintended consequences
Some unintended consequencesUnintended Consequences
Unintended Consequences is a novel by John Ross, first published in 1996 by Accurate Press. The story chronicles the history of the gun culture, gun rights and gun control in the United States from the early 1900s through the late 1990s...
have been observed from post fire seeding. Seed mixes, even “certified weed free” seed mixes, have been contaminated with invasive species and initiated new infestations. Successful growth of seeded grasses (i.e., enough to affect water erosion) have displaced native or naturalized species, including shrub and tree seedlings. Seed bed preparation and the seeding process has facilitated the growth and expansion of naturalized non-native species. The machinery used in landscape seeding operations (e.g., drill seeders and chains) impact surviving native plants and disturb microbial soil crusts.
Other factors
Other land management activities can affect the effectiveness of post fire seeding. GrazingGrazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
seeded burned areas exacerbates the problem of non-native annual grass invasions, even when conducted after a two year hiatus. Historic post logging
Logging
Logging is the cutting, skidding, on-site processing, and loading of trees or logs onto trucks.In forestry, the term logging is sometimes used in a narrow sense concerning the logistics of moving wood from the stump to somewhere outside the forest, usually a sawmill or a lumber yard...
seed treatments had a significant influence on the effectiveness of post Rodeo-Chediski fire
Rodeo-Chediski fire
The Rodeo–Chediski Fire was a wildfire that burned in east-central Arizona beginning on June 18, 2002, and was not controlled until July 7. It was the worst forest fire in Arizona's recorded history until June 14th, 2011 when the Wallow Fire surpassed Rodeo-Chediski as the largest fire in Arizona...
seeding.