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Prairie enthusiasts: 
	I have done some restoration work and collected seed at a prairie
remnant at a State Recreation Area in southeast Nebraska.  Recently I had
a phone conversation with the Superintendent of the area, and he inquired
about disking as a method of increasing forbs.  Thinking back on the
conversation I don't remember if it was in reference to a treatment for
prairies or for any grassy area, but I assumed it was in reference to
prairies because that's what we were talking about.
	I have heard of disking by game agencies as a means of increasing
stem densities, usually with the intent of benefitting upland gamebirds.
Apparently the disks are positioned vertically so they only cut into the
ground without ripping or turning the sod/soil.  I can understand
rhizomatous species responding to this treatment in a positive manner, but
I would think it would be disastrous for taprooted species.
	Does anyone have any information/experience with this type of
manipulation?  I sent a letter to the superintendent accompanied by some
literature.  I thought members of this list would be interested in it so
it is included below.  The articles I sent him are:

Davison and Kindscher. 1999. Tools for diversity: fire, grazing and mowing
	on tallgrass prairies. Ecological Restoration 17:136-143.

Collins, Knapp, Briggs, Blair and Steinauer. 1998. Modulation of
	diversity by grazing and mowing in native tallgrass prairie. 
	Science 280:745-747.

Collins and Steinauer. 1998. Disturbance, diversity, and species 
	interactions in tallgrass prairie.  Pages 140-158 in Grassland 
	Dynamics:long-term ecological research in tallgrass prairie, edited by 
	Knapp, Briggs, Hartnett and Collins. Oxford University Press, New 
	York.

Hartnett, Hickman and Walter. 1996. Effects of bison grazing, fire, and
	topography on floristic diversity in tallgrass prairie. Journal of
	Range Management 49:413-420.

Howe. 1994. Managing species diversity in tallgrass prairie:assumptions
	and implications. Conservation Biology 8:691-704.

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

Howe. 1999. Dominance, diversity and grazing in tallgrass restoration.
	Ecological Restoration 17:59-66.

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

Knapp, Blair, Briggs, Collins, Hartnett, Johnson and Towne. 1999. The
	keystone role of bison in North American tallgrass prairie. Bioscience
	49:39-50.

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.

Dear Jay:
	Here's some more literature.  Your question about disking as a
method of increasing forbs prompted me to find these articles.  They all
tend to discuss the effects of various treatments (burn date, mowing,
grazing) on plant diversity.  The general theme is:

	1) tallgrass prairie is characterized as a community dominated by
warm season grasses (C4 grasses), especially big bluestem, a wide variety
of less abundant forb species, and few woody plants.
	2) tallgrass prairie diversity is a function of both the total
number of species and the abundance of the most dominant species (big
bluestem).  The total number of species is primarily determined by the
number of forb species.
4) spring burning is necessary to maintain tallgrass prairie in its
characteristic state.
	5) spring burning benefits big bluestem greatly, at the expense of
many other species, because big bluestem can out-compete many other
species.
	6) treatments that are detrimental to big bluestem may benefit
other species because the treatments reduce the competitive effect of big
bluestem.

	One thing to keep in mind though, is that none of the articles
really discuss what the effects of any of the treatments are on
"conservative species" of forbs (or conservative grasses and sedges for
that matter).  Conservative species are generally thought of as those
species that you typically find only in medium to high quality prairie
remnants.  Part of the motivation for restoring and preserving prairie
remnants is to protect species that may require those areas to exist.
Conversely, non-conservative species are found in numerous areas such as
road ditches, agricultural fields, CRP fields, and just about anywhere
else you might look.  Because non-conservative species tend to be common
in numerous areas, and they often thrive in human-altered landscapes, they
typically aren't considered appropriate targets of conservation
activities.
	Consider a hypothetical scenario where a person determined that a
prairie remnant was characterized by low diversity and that person wished
to increase the diversity of that remnant.  A relevant example would be
the prairie on the east side of Twin Lakes WMA, which is primarily a
grassland with very few forbs relative to many other prairie remnants.
That person applied a treatment (summer burning, grazing or mowing), and
the response was an increase in the abundance of forbs.  Technically
diversity has been increased.  But a closer examination revealed that only
two forbs increased in abundance, western ragweed and common milkweed.
	Western ragweed and common milkweed are undeniably prairie
species.  They are found in most prairies and often in high abundance.
But they are also found in just about every other non-prairie habitat that
doesn't have a canopy of trees.  The question then is: has anything been
accomplished that has increased the quality of that prairie, or has
prairie conservation as a whole been advanced?  There are valid arguments
that can be made from many perspectives in answer to that question.  If
the treatment that was applied resulted in an increased abundance of wild
indigo, gentian, compass plant, or even prairie fringed orchid (a T & E
listed species), I would argue that the quality of that prairie has
increased, and prairie conservation has been advanced.  These are species
that are considered "conservative" and typically are not found in habitats
other than prairie remnants.
	To repeat what we discussed on the phone, I have my doubts about
disking as a method of prairie restoration or management.  I have never
seen it advocated in the restoration literature, I have only heard about
it being used by game agencies as a way of manipulating gamebird habitat.
I doubt there is any documentation of its effects on "conservative"
prairie species, because I think I would have run across that
documentation by now.  I do not doubt that there are species that would
respond positively to such a treatment, but I am inclined to think they
would be weedy, "non-conservative" species.  I am also inclined to think
that many conservative species would be harmed by the treatment.  Any
taprooted plant that has its taproot severed would probably die.
	I hope you find the enclosed literature usefull, and if you're
interested in any additional materials, let me know.

Steve







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