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Re: Fire this early??

On Fri, 9 Apr 1999 DACESH@aol.com wrote:

> I read about prescribed burning taking place in early April, and I get a 
> little concerned.  Fire is a tool, but if not properly applied, it does no 
> good.  Burning this early only promotes cool season exotics;  the research 
> shows the best time to use fire for controlling these exotics is at the end 
> of April through mid May.

I would like to offer what I have been taught about this subject.
It might be helpfull to consider the direct and indirect effects of fire
on vegetation.  Direct effects occur when the flames top-kill or
damage plants.  If a plant is actively growing at the time of a burn, it
will probably be injured or top-killed.  How a plant recovers from that
should depend on it's ability or inability to resprout.  This in turn may
depend on the amount of nutrient reserves the plant has available in
storage organs.  If a burn occurs when reserves are low, the plant
probably won't recover well, and you might say it has been "controlled". 

Indirect effects occur when a fire subsequently alters light, nutrient or
soil moisture levels, and these changes in turn influence plants.  For 
example, high levels of litter accumulation lengthens the growing season
of cool season plants and shortens the growing season of warm season
plants.  Fire (regardless of time of burn) generally reduces or eliminates 
litter, and litter level influences plant productivity.  Thus fire
indirectly affects plant productivity.  

Below are a number of citations that may be of interest.

Benning and Bragg. 1993. Response of big bluestem (Andropogon geradii
Vitman) to timing of spring burning. American Midland Naturalist
130:127-132.

Bragg. 1991. Implications for long-term prairie management from seasonal
burning of Loess Hill and tallgrass prairie. in Nodvin and Waldrop (eds),
Fire and the environment: ecological and cultural perspectives:
Proceedings of an international symposium. USDA Forest Service General
Technical Report SE-69, Southeastern Forest Experiment Station.

Howe. 1994. Response of early- and late-flowering plants to fire season in
experimental prairies. Ecological Applications 4:121-133.

Hulbert. 1988. Causes of fire effects in tallgrass prairie. Ecology
69:46-58.

Knapp and Seastedt. 1986. Detritus accumulation limits productivity of
tallgrass prairie. BioScience 36:662-668.
		Results from research at Konza Prairie and
	summarization of other studies.  Detritus accumulation may be the most
	important factor influencing tallgrass prairie ecosystem functioning.
	Regardless of how you remove the litter (fall, winter or spring
	burning, grazing, or raking), the direct effect of litter removal
	may be the same (remove litter, and the soil dries and heats faster, 
	and is exposed to higher light levels).

Towne and Owensby. 1984. Long-term effects of annual burning at different
dates in ungrazed Kansas tallgrass prairie. Journal of Range Management
37:392-397.
		Research from plots that have been burned since 1928 using
five treatments: no burn, winter burn (December 1), early spring burn 
(March 20), mid-spring burn (April 10), and late spring burn (May 1).  One
of the suprising results: there was no significant effect of burn
date on Kentucky bluegrass, it was equally harmed by all 4 of the burn
dates, while it did very well in the unburned treatment.  Apparently it
was activly growing at the time of all burns and was directly affected by
the flames (top-killed or injured).

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