• Introduction
• Evaluating the potential for natural recovery
  • Burn severity & plant survival
  • Noxious weed cover & survival
• Revegetating with competitive plants
  • When revegetation is necessary
  • Formulating a Seed Mix
  • Things to consider
• Establishing competitive plants
• Managing competitive plants
• Integrated Weed Management
• Preventing noxious weeds
• Eradicating small weed patches
• Managing large weed infestations
  • Mechanical control
  • Chemical control
    • Timing & placement
  • Cultural control
  • Biological control
• Monitoring & Evaluation
• Developing a burned-area IWM plan
• Summary
• Sources and Credits
• Additional Resources
• Interactive Exercises

Rangeland Weed Management - Evaluating the potential for natural recovery

Noxious weed cover and survival

After assessing the severity of the burn, estimate noxious weed cover before the fire (See Appendix A). Unless you recorded the degree of weed cover before the fire, it may not be easy to estimate the extent of pre-burn noxious weed cover. But if areas immediately adjacent to the burned area have moderate noxious weed cover, it is possible that the burned area had the same degree of cover by the same weeds. If so, and depending upon the severity of the burn and weed characteristics, you can expect some degree of noxious weed survival.

Many noxious weeds can reproduce vegetatively from rhizomes, which bear vegetative root buds capable of producing new, independent plants (See Appendix B, Rhizome-spreading Noxious Weeds of Montana). These weeds have extensive root systems that can grow quite deep. The roots of leafy spurge (Euphorbia esula) can extend to depths of 26 feet, with vegetative root buds at depths of 10 feet or more. The roots of Canada thistle (Cirsium arvense) can pen- etrate the soil as deep as 22 feet. Because even the most severe fires typically damage roots only to four inches below the soil, these noxious weeds have an excellent chance of surviving and aggressively reestablishing, even after very severe fires.

Need for Revegetation

Fortunately, weed reestablishment can be mitigated with an effective burned-area weed management plan. An initial component of such a plan may be revegetation.When indicated, revegetation can suppress noxious weeds by introduc- ing competing plants. To determine whether revegetation is needed, begin by measuring the overall burn severity of the site (see Table 1) and estimating the extent of pre-burn noxious weed cover.

Once these are known you can begin to assess the need for revegetation (see Table 2). Typically revegetation should be constrained by the abundance of available plants and propagators -again, the plants themselves, and seeds, root crowns and rhizomes - that direct natural recovery.