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FW: prairie and bugs

The following is a digest of the Iowa fire and prairie insects discussion.
It's rather long, but at least I've deleted all names to save space and
concentrate on issues... 

Subject: [iowa-native-plants] BURNING & EFFECT = ON INSECTS a novice asks

Not knowing anything about fire and insects, I would = step back and ask a
few questions and make a few comments.  Rather = than ask about burning
today, I would ask the question about how long have = the prairies been
burned prior to the European invasion of man?  = If the prairie, as we
discuss it, has been here for 12,000 years then has = the prairie been
burned either by natural forces and the Native = American?  Suspecting
that the prairie has burned on a chaotic basis over = the last twelve
millennia, would the question then be what changes = have we made to the
natural order of things by not letting the prairie = burn in its normal
course of time?

Do insects that cycle or appear at odd intervals of = time, say the
cicadas, or in prime number cycles, evade = destruction by fire or other
natural events by this mechanism?

I remember reading a family history (1800s) about = burning the field when
the grasshoppers arrived. This provided feed for the = chicken over the
winter.  Would grasshoppers be a good insect to = monitor in burned vs.
unburned prairie, or perhaps they travel too great a = distance or appear
at the wrong time of year to have fire affect = them?

How do the insect eggs evade destruction by = fire?

================================
============================================================
Good questions.

There may be no good answers to them, since our knowldege of insects in
general is very poor, and of their population dynamics, even worse.
Generalizations about this single most diverse group of eukaryotic
organisms are very hard to make.

It's safe to assume that Native American burning practices had the same
effects as burning practices today, inasmuch as they were of the same
frequency, seasonality and intensity, with the possible difference that
burned areas may have been more readily re-colonized from fire refugia
within the burn area and unburned areas outside. But we also know that
unlike today, many "Indian fires" were set during summer droughty spells
or in fall, during which many insects, even plant-feeders, seek refuge from
the heat in cracks or burrows in the soil, of their own or others'
making. Litter, pithy stems, bases of grass clumps and other near-ground or
subterranean parts of plants, and soil yield increasing order of
insulation from fire, and many prairie insects spend all or part of their
lives in
these sites. Fall burns tend to leave more standing pithy stems than
spring burns, because of their higher moisture content then. It would be
interesting to sample such scorched stems systematically to determine
what might survive fire inside them.

Insects with irregular population surges occur in the prairie, but (1)
the two you mentioned, periodical cicadas and migratory grasshoppers, do not
occur in the tallgrass prairie or fly in after maturing out west,
respectively and (2) the resident species that do have notable
population fluctuation, seem to do so independent of fire. Periodical
cicadas occur
within the prairie ecoregion, but  are restricted, even today, to sites
that were historically wooded. Migratory grasshopers no longer have the
conditions to cause the big population surges, or in the case of certain
species, have gone extinct. The prairie cicada is not periodical; it
just emerges annually as an adult during the season when the prairie is
least
likely to burn, after spending most of  its life deep in the protection
of the soil. On the other hand, I can remember years when Gorgone crescent
butterflies or Least skippers (in dry and wet sites here at the reserve,
respectively) were extraordinarily abundant, but there seemed to be no
connection to fire. This deserves more study, but entomological research
apart from that on medically or agriculturally important species, is
very poorly staffed and funded.

================================
4/21/2002 12:14 PM

E. Evans has a couple of articles related to grasshoppers/fire/tallgrass
from research at Konza Prairie.  A few points he makes:

He noticed the largest changes, not surprisingly, in areas which had
been unburned for the longest times before being burned.  Annually burned
sites showed less change in grasshopper populations, suggesting that the
species which occur there may be better adapted to fire.  There was also
little
change in the control site, suggesting the changes were probably due to
fire.

"...relative abundance of forb vs grass feeders increased across burned
watersheds with time since last burning...mirrioring the relative
abundance of forbs vs grasses..."

"...sites burned every forth year had the highest diversities because
grass and forb feeders occurred in relatively equal proportions...forb
feeders
were generally relatively uncommon on more frequently burned sites..."

From: 'Fire as a natural disturbance to grasshopper assemblages of
tallgrass prairie': OIKOS 1984.  43:9-16

He goes into more excruciating detail in a paper in the Canadian Journal
of Zoology entitled, 'Grasshopper (Insecta: Orthoptera: Acrididae)
assemblages of tallgrass prairie: influences of fire frequency, topography,
and
vegetation'.  1988.  66:1495-1501.

Generally, he suggests (in both papers) that, at least for grasshoppers,
fire DOES influence grasshopper populations, but does so primarily
through it's indirect effects affects on vegetation.

=========================================
Sat, 20 Apr 2002 12:17:30 -0500

Anne Swengel (International Crane Foundation, Baraboo, WI), Dennis Schlict
and colleagues have argued that burning is just plain bad for prairie
insects, especially prairie-dependent butterflies. Anne's latest review of
the subject qualifies this somewhat by noting there seems to be little or no
deleterious effect from burning on these organisms in Missouri prairies, but
the hypothesis still holds for Wisconsin. In my experience, Anne's papers
are hard to read because the conclusions don't always seem to be supported
by the data presented, alternatives to the favored hypothesis are not
discussed, and the statistical analysis is, to put it nicely,
inappropriately applied. (Two colleagues much better in statistics than I
have stated this to me independently -- in stronger terminology.)

On the other hand, Ron Panzer (Northeastern Illinois U.) and colleagues
argue that the "only thing worse than fire for prairie-dedendent insects is
no fire". A recent paper of theirs on Chicago area remnants compared a large
number of insect species in unmanaged prairie remnants (not burned in recent
decades) with those in remnants managed with fire. They found that the
burned prairies not only had a higher number of prairie-specialist insects
persisting in them, but that looking at the after-effects of several burns
in the managed ones showed only one apparent loss of a conservative species
and no loss of generalist species. Since insect populations are notoriously
variable from years to year, the apparent loss may be an artifact of
sampling.

Working separately, Chris Dietrich of the Illinois Natural History Survey
("the Smithsonian of the Midwest") has shown that fire sets back many
herbivorous insect populations during the early part of the first post-burn
season, but that numbers return to pre-burn levels in a season or two.

Collectively, these studies argue for some conservatism in burn frequency,
perhaps substituting with mowing or haying or grazing to help reduce fire
frequency. My own preferred intermittent substitute for burning is
dormant-season mowing to manage brush invasion but leave all the winter
insect hibernacula more or less intact. Fall burning also tends to leave
more unburned patches and standing stems for insects to survive the winter
in. One thing that Swengel, & al. have argued that seems to make sense, is
that on remnants supporting rare insect species, it may be best not to
change historical management patterns or approaches radically, since the
traditional management pattern may have been what favored the rare "bug"
over time.

===================================================
Sun, 21 Apr 2002 13:20:27 -0500
The last national prairie conference in Mason City incuded several
excellent presentations on the insect/fire dynamic. U. of Wisconsin
seems to have spent lots of time examining fire - enhanced/fire -
supressed insect species. All presentations were illuminating.

My synthesis is of course, we know so little , but it is essential to
ask the questions. I was disappointed after receiving the proceedings to
learn that many of the sessions did not include written summaries. I was
counting on them.

==========================================
Sun, 21 Apr 2002 15:17:52 -0500

These grasshopper results are similar in many respects to those for
Australian ants.

Those results, in a nutshell:

1) Species composition changes most radically after a burn following a long
unburned spell.

2) Diversity increases then levels off two or three season following a burn
(subtropical, so it takes less time than in Kansas.)

3) Both functional group representation (the ant analogs of grass vs. forb
eaters, only more groupings) and species composition are related to the
vegetation structure, and amount and type of litter.

4) Frequently burned sites have different functional group and species
composition as they approach the subsequent burn than infrequently burned
sites, though species richness is nearly identical.

In other words, a mosaic of frequently, less frequently and rarely burned
sites is necessary to maintain the total diversity. I put it this way
because in Australia (and probably in the American Midwest, also) there is
no such thing as a site that never burns.

================================
Sun, 21 Apr 2002 15:39:58 -0500

I have many thoughts on this subject, but here is just one. I suspect that
most prairie biota had to be fairly well adapted to fairly frequent, nearly
annual fire, though this fire varied year to year in its timing, speed of
travel, and intensity.
I have been out burning some tallgrass prairies this spring, mostly
recreations, as many of you no doubt have also been doing. What is
impressive to me, when you get the roaring 30-40 foot flames with an
occasional head fire (we usually backfire about half), thinking back to
pre-European settlement times, if you were living on the prairie, there is
no way you would want to take the chance of being caught by one of these
fires. So naturally you would set fire to the prairie intentionally every
single year in order to create a large firebreak around your camp. If you
didn't, you could be toast. These set fires then had nothing to stop them
except very large rivers and lakes. This is not to say every acre burned
every year, but that fires were at least started intentionally every year
where natives lived, which was almost everywhere except semi-permanent war
zones, such as the Chippewa-Sioux war zone in northwest Wisconsin around
the Chippewa River.
Another side thought, having teenage boys myself, one wonders if this job
wasn't assigned to these natural pyromaniacs. When they got bored or
restless, father would say, "go get your friends together and set fire the
prairie, make sure we don't get burned up." That would keep them out of his
hair for a little while anyway.

===============================
Sun, 21 Apr 2002 22:05:16 -0500

Doesn't the foundation for prairie burning by humans have to start with an
understanding of population density and distribution - and then settlement
locations? If villages are miles apart and located near water sources, human
burning may be less significant that we believe. From an evolutionary
setting, we're talking pre-European settlement, i.e., dogs were the beast of
burden and rivers/streams the roads.  Wouldn't the tallgrass prairie be a
forbidding wilderness? It was clearly forbidding to European settlers!
Burning of oak savannahs may be something else because picking up nuts in
tall grass is not fun. But then how many nuts did a family need for the
winter?

=============================
Sun, 21 Apr 2002 23:13:57 EDT

A note on recent comments.
1. Grasshoppers and ants are in underground stages during spring burn times.
So their reposes have little to do with what happens to the species that are
in the vegetation. they actually should not be directly affected. Dormant
eggs, pupae, larvae and adults above ground are lost.
2. Historical models for fire on the prairie do not function on our
non-landscape disconnected sites. Each one has to be treated as though it
were the only one because the invertebrates cannot recolonize.

==============================
Monday, April 22, 2002 7:55 AM
To:  Native Plant folks

When I became director of the Indian Creek Nature Center in l978 the place
was mostly degraded savanna and about 40 acres of flat pasture that was 100%
brome grass.  There was no diversity.  We had no money and ecological
restoration was in its infancy.    I had moved here from Kansas where I had
managed a prairie with fire.

I began burning the brome in the late 1970's and we've kept at it ever
since.

We overseeded in the brome with whatever prairie seeds we could find.  The
combination of burning and overseeding has brought a tremendous change.   It
is a gorgeous area now with a wide diversity of native plants.  Most of the
brome is gone.
Butterflies are all over the place, as are many other insects.

I have been heavily criticized by butterfly people for burning, however we
started with
brome and no butterflies.  Burning itself brought in monarda and mountain
mint and many other plants that were here but needed the fire to trigger
them.     Without fire this restoration would have failed. We'd have 100%
brome grass and no butterflies.

The thesis that burning destroys butterflies is an academic exercise.
Perhaps it would if you had a tiny remnant surrounded by a vast area of
nonprairie and a few insects haning on.   That's not the case here. There
are
all sorts of pockets of grassland that don't burn, on our property and on
neighbors nearby.  There are plenty of refuges.  Also, we don't try to burn
every square inch.  We let the fire mosey around nad it creates a mosaic.

However I reject the argument that burning destroys butterflies.  On the
contrary one must burn to maintain prairie vegetation. Without prairie
vegetation you will have no prairie butterflies.

=================================
Mon, 22 Apr 2002 11:54:30 -0500
The argument should not revolve around whether or not to burn, but rather
how to burn safely for prairie obligate invertebrates which are sensitive to
fire.  Judicious use of fire is good for the prairie and savanna, and
therefore good for species that depend on healthy prairie/savanna
communities, but it has also been demonstrated through good research that
there are fire- negative, fire-neutral, and fire-positive species.  Even
within species the response to fires varies with timing of burns and fuel
conditions.  The species of concern (fire-negative) tend to be the rare
prairie specialists.  The species that show up in formally degraded habitats
tend to be more generalist species.  Having invertebrates show up after
burning is a good thing, but does not necessarily mean that the prairie
fauna has been restored.

There are good arguments for why we cannot use fire in a fragmented
landscape in the same way it occurred in the original unfragmented prairie
landscape.  It is generally accepted that extinction probabilities increase
with a decrease in the size of natural remnants.  Yet, the same people that
suggest that our small high quality preserves are not viable because of
higher extinction probabilities, will turn around and suggest that if
species could survive a natural or anthropogenic event in the original
prairie landscape they should be able to survive that same event in a small
isolated remnant.  For many invertebrate species the mechanism for survival
might have been high fecundity (reproductive rates) and vagility (dispersal
capability) rather than survival, a strategy that no longer works in our
current fragmented landscape.  As such, we as managers need to provide for
internal recolonization sources.  We also have to keep in mind that
populations in small fragments are often smaller and therefore more prone to
extinction.  Our job as managers is to try to reduce extinction
probabilities while enhancing the overall health of the communities we
manage.

Several general guidelines apply:
1) Never apply the same management activity to an entire remnant at any one
time.  This not only applies to fire, but also to activities such as haying
and grazing.
2) Fire is a good management tool (e.g. maintaining a prairie once woody
vegetation is under control), but needs to be used in combination with other
tools for restoration (e.g. mechanical removal to restore prairies with
major woody vegetation invasion problems).  Used by itself it is less
effective, and requires a frequency and intensity that would be detrimental
to fire-negative invertebrates.
3) Remnants need to be divided into several burn units (at least 3-5) taking
care not to include all of any habitat type in any one burn unit.  Dry
prairies can be burned less frequently than mesic prairies.
4) Avoid burning adjacent areas in consecutive years.

These are just a few suggestions.  Managing for diversity is complex!  There
are no simple solutions!  As a general rule appropriate applications of
diversified management will lead to more diversity than simplified
management approaches.

===============================
Mon, 22 Apr 2002 13:22:26 -0500

By breaking up remnants into five burn units, I assume that one unit would
burn every fifth year. If so, what studies can be cited that show a negative
effect on prairie specialist insects four years post burn? Secondly, new
insects and invertebrates are being discovered all the time. I think it's
been shown that restricting fire too much distorts the plant community (to
cite just one study: Leach, Mark K and Thomas J. Givnish, 1996. Ecological
determinants of species loss in remnant prairies. Science 273:1555-1558) by
disfavoring legumes, small stature, and small seeded plant species. By
distorting the plant community, you distort the invertebrate community as
well. You may not be identifying or studying the invertebrate specialists
you are losing or gaining, but it will be happening.
Disturbance regimes are a critical ecological process that affects all
aspects of a system. We like to focus on fire because we all love prairies.
But think about flood, another nearly annual disturbance. Let's say we
conservationists own a dam on a river and with that dam can control the
flood cycle. We know the flood cycle used to be annual before the dam was
put in, back in the 30's. But we find one species of water strider that is
present below the dam that only likes floods once every five years. There
are still hundreds of unstudied invertebrates in that same stretch of river.
Are you going to change the flood cycle to match the one water strider?
I do agree we should not burn all of every remnant, we should leave refugia,
but let's not distort the whole system.
Bob Wernerehl
===================================
Date: Wed, 24 Apr 2002 12:16:53 EDT

"Let's not distort the whole system?" By definition, Iowa's remaining
prairies are islands managed by unnatural means. We have no other options:
our prairie environments are now all lab experiments, whether we recognize
it
or not. Whatever we do, it will distort the system. We need to keep studying
the systems, be mindful of regional and subregional differences, and manage
conservatively.

A related problem is that Iowa prairies have long been managed by people
used
to managing prairies in Kansas, or who were trained by burn managers from
the
southern pine forests. The situation here is radically different. I agree
with Gerald Selby; let's manage conservatively, and continue studying and
debating the results. How many management agencies put in the person-hours
each year that TNC does in cutting brush, grazing, etc., trying to diversify
management approaches?

I also hope that we'll quit trying to play "gotcha." Instead of discounting
all the insect studies by mentioning selected plant studies, let's try to
work on long-term solutions that will attempt to conserve all the species in
these little laboratories. Even then, given the principles of biogeography,
we know that it is an uphill battle. Let's not push the specialist insects
off the life-raft.

========================
Wed Apr 24 11:49:52 2002

COMMENT:
 
1. Grasshoppers and ants are in underground stages during spring burn
times. So their reposes have little to do with what happens to the species
that are in the vegetation. they actually should not be directly affected.
Dormant eggs, pupae, larvae and adults above ground are lost.

2. Historical models for fire on the prairie do not function on our
non-landscape disconnected sites. Each one has to be treated as though
it were the only one because the invertebrates cannot recolonize.]]

RESPONSE:

Right you are:

And, this is why I suggest interspersing management that leaves intact
stems, galls, etc. Also, I have had the opportunity to see the results of
some summer burns. They are very "messy", i.e. a significant portion doesn't
even burn, a good thing for maintaining insect refugia. Like I said before,
we also ought to have more info on what survives in unburned stems left by
fall burns. Spring burns may be the most damaging kind for plant-inhabiting
prairie insects, because of the more complete destruction of their
microhabitats.

Also, to another correspondent:

No one is saying not to burn prairie reconstructions in order to get them
into shape, nor that they don't end up with lots of insects in them. But
remnants with fire-sensitive, prairie-specialist species need more cautious
treatment. The latter sorts of insects are rare in reconstructions, or never
make it into them at all without specifically being introduced. Dozen of
such species are known, probably many more exist, and almost no one works on
introducing them into the reconstructions.

((To plant people wondering why we're spending so much time on "bugs": Not
about Iowa native plants specifically, so indulge us bug enthusiasts" as we
talk this one through. Since so many of the insects in question have direct
impacts on plants through herbivory, granivory, etc., I think it's relevant.
And it's certainly bringing in voices we don't hear from often. Thanks for
your patience.))

=====================================
Date: Wed, 24 Apr 2002 19:11:38 -0500

I appreciate the insights in terms of moving with caution. The systems we
presume to "manage" , and I do
believe that we have a very strong drive to "manage",  are so complex
that humility is a good first step.

I just had my students read Carolyn Raffensperger's "Precautionary
Principle"  and apply it to their top environmental challenge/problem.
Is that where we might need to be with prairies/savannas? Not unlike the
physicians oath of doing no harm. To acknowledge that we harm some and
encourage some is an honest assessment. Basically, the precautionary
principle advocates looking before leaping.. asking what harm may come
form my actions.

While I am totally anamored with the plants, I'm loving the insect
discussions too and hope to learn much more from these good discussions
as I know I have so much more to learn.

Restoration Ecology had an excellent paper last year related to the
ethics of burning and the harm that some species experienced.
Interesting to dance with that idea from a philosopher's reference point.
Keep up the good work!

===================================
Date: Wed, 24 Apr 2002 21:05:29 EDT
Subject: Burning and bugs

Hello All

Most of the folks on this list know and are concerned about all elements of
our vanishing natural landscape.  Certainly the enormous impact of the
invertebrate world on prairie is appreciated even if it is poorly
understood.

Our knowledge of native landscapes is growing as we slowly pry information
from the pathetic few remnants we have left to work with.  Knowledge is
necessary to manage wisely and we have too little.  No ethical land manager
knowingly destroys natural diversity if they have a choice.  Every remnant
is priceless and it is devalued when we lose any species.

Some of the problems facing natural area managers (I am one.) include lack
of specific knowledge of conservative insects and which plants they are
obligate to, the optimum burning conditions to protect target species, and,
of course, the lack of staff and money.

If land managers lack adequate staff and support to manage the way they know
is best, all discussion is strictly academic.  Karst prairies or xeric sites
are easy to take care of compared to riverine systems where I do most of my
work.  If we go without a burn for more than three years on many of my
remnants, there won't be any prairie.  Dogwood, willow, buckthorn, locust
and a host of other woody pests will insure that there is no resource to
save for the conservative species we wish to protect, if they are there.

A reality check tells us we don't have a legion of volunteers waiting to cut
and treat brush, mowing large woodies is not an option in areas that are wet
seven months a year - we have to burn and burn frequently or lose the
resource.

The old saw that says, If you only have a hammer than every problem begins
to look like a nail, has some validity.  I would love some constructive
advice on how to do my job better but telling me not to use the only tool
(even if it is a crude hammer) I have that works isn't an option.

The secret to addressing this "problem" is information.  Those of you who
know the invertebrates of the prairie world best, need to share what they
know of the threat presented by the extensive use of fire as a management
tool but they also need to rise to the occasion and to help distribute
reasoned, conservative guidelines for the use of fire.  It would be helpful
if that advice was tailored to address the insects most likely to be found
on
remnants that occupy different landscape positions.  Simply saying "don't
burn" and criticizing fellow prairie restorationists isn't going to persuade
many practitioners to be more judicious, given our limited resources.

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