Tom's Blog

Friday, November 20, 2015

Using fire in a rational prairie/savanna restoration program

This is the time of year to be thinking about spring burns.

We have been burning at Pleasant Valley Conservancy for almost 20 years now, and the program set out below is based on our experience. We've learned a lot from doing burns with TNC, MAS, Dane County Parks, and TPE. But we've especially learned a lot from our own burns. I've always taken careful notes of each burn, and made a detailed map and narrative. I started using GIS eight years ago, and this has been very helpful for creating professional-looking maps of burn plans and burn results.

When we started prairie and oak savanna restoration at PVC, we made the mistake of burning before doing any significant brush removal. (We were poorly advised.) Fortunately, those early burns were almost completely ineffective, since there was nothing to carry a fire. I say "fortunately", because if they had been successful, all those large buckthorn and honeysuckle plants that would have been killed would have resprouted large numbers of new shoots, making them lots more difficult to eliminate.

We did have successful burns of two small prairie remnants that had no brush problems.

Fortunately, our tree and brush control program got ahead of our burns.

Here are the steps I envision in a rational prairie/savanna restoration burn program:

  • Start with your very degraded remnant(s)
  • Don't burn
  • Get rid of all the undesirable woodies by cut-and-treat or basal bark. Brush removal and tree removal move ahead together
    • Brush
    • Invasive trees
      • Walnuts
      • Aspen (by girdling)
      • Cherry
      • Box elder
      • Elm
  • As soon as the site is clear, burn to make way for the seeds
    • If the fire doesn't carry well because of sparse fuel, force it to burn by doing extensive interior lighting (stripping; see photo below).
  • Overseed with appropriate understory forbs and grasses
  • Start annual burning to get the natives well established
    • Continue overseeding after each burn for another year or two
  • Continue annual burning for 5-10 years (the longer the better)
    • Use foliar spray after each spring burn to kill woody resprouts 
    • Gradually the site will improve
    • Modify your fire technique as the years go by
  • Once the site is well established (but not too soon) switch to a period of 2 burn years followed by 1 off year.
    • The off year is to give the residual brush (which will certainly still be present) a chance to get big enough so that it can be easily found and killed with herbicide.
    • Basal bark herbicide is probably the best, since it can be done 12 months of the year, although large clonal patches are probably better cut with a brush cutter. Be sure to treat every cut stem.
  • Continue the 2 on 1 off cycle indefinitely, always monitoring the brush and making sure it has been eradicated
The above protocol should be modified depending on conditions, but the basic rationale should remain the same. For a large site, it is best to restore small units (5-10 acres at most).


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