Kevin and Ecolog:
Just what is it about "bare mineral soil" that is needed to ensure the
perpetuation of any life form? And just what research and replication of it
has demonstrated that?
WT
----- Original Message -----
From: "Kevin Robertson" <krobert...@ttrs.org>
To: <ECOLOG-L@LISTSERV.UMD.EDU>
Sent: Monday, October 08, 2012 7:19 PM
Subject: [ECOLOG-L] FIRE Wildland and Urban Interface Myth or Truth 1 Fire
dependent plants?
Another angle, which might in part have been the intent of the interviewee
in question, is that many plants are dependent on environmental conditions,
including plant community structure, which are dependent on fire, at least
in a natural ecological context. We know that in southeastern U.S.
pine-grasslands that are large percentage of the of several hundred species
of herbs disappear upon excluding fire for several years, some sooner than
later, as well as many species of animals that depend on them. This is
because woody plants that would otherwise be topkilled rapidly grow and
outcompete herbs through root competition and shading, in addition the
removal of fire as a reproductive cue for reproduction and a means to
provide bare mineral soil for seed germination.
That aside, I am pretty unapologetic about saying that certain plants are
"fire dependent" when talking about this ecosystem. That is not to say that
you could not get the plant to survive and reproduce in a greenhouse if you
knew what specific environment and cues were required, but in an ecological
context it appears to be true that populations of certain species depend on
fire for their survival, at least there is no other process that we know
which would take the place of fire's function in that population's survival.
A well studied case is that of wiregrass (Aristida stricta), which for a
long time was thought (even if illogically) to no longer sexually reproduce,
since no one had ever seen it flower and produce seed. However, at the time
controlled burns were annually applied in the winter throughout much of the
region, preempting lightning initiated fire later in the growing season. It
was discovered later that burning (and perhaps lightning-initiated or
accidental fire) in the growing season, especially May-June, did cause the
grass to produce seed, and this corresponded to the period when
lightning-initiated fires were and still are most common. Grazing does not
seem to have the same effect of fire on this species with regard to
reproduction. Is there any set of circumstances in which it would flower
without fire? Probably. Would that set of circumstances have occurred
historically without human intervention (it was around before Native
Americans)? Probably not, or extremely rarely. Would wiregrass be one a
common grasses throughout the eastern half of the southeastern U.S. Coastal
Plain without fire? Absolutely not. Thus, for all intents and purposes, in
an ecological rather than theoretical or physiological context, I would say
it is a fire-dependent species.
Kevin Robertson
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