The effects of wildfires on plants will vary, depending upon fire intensity and specific plant characteristics. Many plant species will survive and reinitiate growth soon after a fire. However, the ability of desirable plants to reestablish, reseed and flourish in subsequent years can be impaired if noxious weeds are inadequately managed.
Preventing weeds from spreading through seed dispersal is the most effective and least costly method of weed management. Survey burned areas to eradicate new weeds, concentrating on areas where weed infestations often begin such as along fire lines or other disturbed areas, roadways, trails, railways and waterways.
Burned areas often contain high nutrient levels, exposed, un-vegetated soil surfaces and reduced shade. These conditions favor weed invasions and exponential weed growth, which can reduce or completely prevent reestablishment of preferred vegetation and displace remaining native and desirable plants. If allowed to reach large infestation levels, the resulting weed population will be very difficult and expensive to manage. Newly established populations (or those smaller than approximately 100 square feet) are most responsive to control or elimination with herbicides, pulling, mowing or cultivation. Due to weed seed dormancy and longevity in the soil, weeds will have to be removed continuously and steadily replaced with desired vegetation until viable unwanted seeds are eliminated and reinvasion potential is sufficiently reduced.
Burned areas that have inadequate competitive vegetation cover (below 30 percent) to reestablish naturally can benefit from reseeding. A seed mix should include quick-establishing grasses and forbs (or broadleaf plants). Broadcast and spot, or targeted herbicide treatments should be applied pre- and post-seeding, according to herbicide label directions.
Most successful revegetation efforts in our area have been fall-dormant broadcast seeding directly into the ash (or disturbed soil) layer. Burned area revegetation can also benefit from seed placement with a no-till drill.
Management efforts that support and enhance healthy plant communities help shift the competitive balance from weed infestations to desired plants by revegetating, if necessary, after the infestation has been weakened through mechanical, chemical, cultural and/or biological control methods.
For more information on noxious weed management and revegetation, contact your county weed board, extension service, and land management agencies.
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