[PCA] FW: RE: [Ecology] FW: Great Basin ecosystems and cheatgrass fires

Thu Sep 13 16:33:43 CDT 2007

> [Original Message]
> From: Eric Peterson <peterson at heritage.nv.gov>
> To: <larry.morse.dc at earthlink.net>; NS Botany List
<botany at lists.natureserve.org>; NS Ecology List
<ecology at lists.natureserve.org>
> Cc: <Robert.Dana at dnr.state.mn.us>; <craig at astreet.com>
> Date: 9/13/2007 5:17:47 PM
> Subject: RE: [Ecology] FW: [PCA] Great Basin ecosystems and cheatgrass
fires
>
> Greetings!
> I'd concur in part with Craig, but add some complexities to the oft told
> simple pattern: cows eat native grass, cheatgrass fills in.  Primarily,
I'd
> agree that grazing has a lot to do with what has happened to the Great
> Basin.  I'll try to address this as succinctly as possible.
>
> Unfortunately, we lack good information (heck, we even lack poor
> information!) on what the Great Basin really was like prior to the heavy
> grazing that took off in the second half of the 1800s.  
>
> I'd suggest two things: (1) biological soil crusts would have been much
more
> prevalent and (2) the 'little ice age' may have promoted greater native
> grass biomass.
>
> Grazing at the end of the 1800s and on well into the 1900s was both
> widespread and much heavier that it is even today.  This would have wiped
> out much of the soil crusts.  It is quite notable that almost all
remaining
> sites with high cover are in dry valley bottoms where lack of water and
lack
> of much of any herbaceous plants would have been unattractive to grazers.
> (The exception being the I80 corridor which was a cattle drive route as
well
> as a corridor for other transportation, hence little soil crusts even in
the
> driest areas.)
>
> Loss of soil crusts, particularly while still within the 'little ice age'
> may have actually lead to an initial flush of native grasses as the soil
> surface niche opened up.  This might help explain why so many old ranchers
> insist that when their great grand-daddy first brought in cows or sheep,
the
> grasses increased.
>
> However, the native grasses that [may have] filled in the shrub
interspaces
> after the soil crusts were trampled out would have been vulnerable to the
> over grazing, as well as the boom-and-bust interannual climate variation
of
> the Great Basin.  Cheatgrass is particularly well adapted to both soil
> surface disturbance and interannual climate variation.  All grasses get
> knocked back a bit in droughts, but cheatgrass, an early-season annual,
> recovers and reproduces faster than the natives.
>
> Although the 'little ice age' may have increased grass cover a little
> despite the historic presence of soil crusts, I am doubtful that it had a
> major impact.  Consider: Most data points to rather long fire intervals
and
> small scale of fires when they did happen in pre-grazing sagebrush systems
> (basin and Wyoming sagebrush that is).  Yet many of the major fires in
> Nevada and southern Idaho in the last two years have been in areas where
> there IS VERY LITTLE CHEATGRASS, but the native grasses have left lots of
> fine fuels.  The native grasses seem to be achieving unnaturally high
> biomass in wet years.  There is some evidence of large pre-grazing
wildfires
> in this area, but we would still need to say something like both of the
last
> two summers have reached 100-year events.  My hypothesis: given the lack
of
> soil crusts and the gradual reduction in grazing, native grasses are
> becoming exceptionally abundant in some areas.  (Small caveat: overgrazing
> also leads to unnaturally high cover of sagebrush, which can also increase
> fire carrying capacity).
>
> To finish off the original question that Craig was responding to... once
> cheatgrass starts to fill in shrub interspaces, a continuous understory of
> fine fuels develops, which carries fire much more easily and extensively
> than native Great Basin shrub systems.  Cheatgrass seed is somewhat
tolerant
> of fire and the annual nature of cheatgrass allows it to reinvade burned
> areas very quickly.  Once reinvaded, the early season growth of this grass
> uses much of the available water before natives have much chance even to
> germinate.  Thus it maintains a monoculture.
>
> Thanks,
> -Eric
> ---
>
> Eric B. Peterson, Ph.D.
> Vegetation Ecologist
> Nevada Natural Heritage Program
> Nevada Dept. Conservation and Natural Resources
> 901 South Stewart Street, suite 5002
> Carson City, NV 89701
>
> 775-684-2906 office
> 775-750-4628 cell
>
>
>
> -----Original Message-----
> From: ecology-bounces at lists.natureserve.org
> [mailto:ecology-bounces at lists.natureserve.org] On Behalf Of Larry Morse
> Sent: Thursday, September 13, 2007 11:01 AM
> To: NS Botany List; NS Ecology List
> Subject: [Ecology] FW: [PCA] Great Basin ecosystems and cheatgrass fires
>
> Ecology mailing list
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> _______________________________________________
>
>
> Larry Morse
> Washington, D.C.
> larry.morse.dc at earthlink.net
> (Larry.E.Morse at LEM-Natural-Diversity.com)
> (202)-543-2488
> < http://www.lem-natural-diversity.com/ >
>
>
> > [Original Message]
> > From: Craig Dremann <craig at astreet.com>
> > To: Robert Dana <Robert.Dana at dnr.state.mn.us>
> > Cc: <native-plants at lists.plantconservation.org>
> > Date: 9/11/2007 2:18:27 PM
> > Subject: [PCA] Great Basin ecosystems and cheatgrass fires
> >
> > Robert wrote:
> >
> > Will someone please clarify how wildfire in sagebrush steppe kills all 
> > the native perennial vegetation? ...
> >
> > Robert Dana
> > MN DNR
> > ---------------------------
> > Dear Robert and All,
> >
> > What has happened to the poor, unfortunate Great Basin ecosystem, is 
> > that prior to the 1840s, it was a shrubland with a perennial native 
> > grass understory in the shrub interspaces.
> >
> > Between 1840 and modern times, the cattle and sheep grazed out a large 
> > percentage of the perennial grass understory, and from my 1997 
> > Megatransect at http://www.ecoseeds.com/megatransect.html you can see 
> > the percentage that remains in each area that I surveyed:
> >
> > Yellowstone NP 89%
> > Colorado------ 44%
> > So. Dakota---- 43%
> > Wyoming------- 40%
> > Nevada-------- 40%
> > Utah---------- 34%
> > Utah---------- 32%
> > Southern Idaho  6%
> > California---- <1%
> >
> > In the Great Basin, the cheatgrass has been moving in, to fill the 
> > empty spaces between the shrubs where the native grasses used to grow.
> >
> > The native perennial grasses originally provided significantly less 
> > fire-fuel than the cheatgrass, and the hotter cheatgrass-fueled fires 
> > are killing the shrubs.
> >
> > Once the native shrubs are killed, that beings a snow-balling effect, 
> > where the cheatgrass has more area to move into, etc.
> >
> > The unfortunate part of the story, is that there are no longer viable 
> > native grass and forb seeds in the soil-seedbank in many areas where 
> > these fires are occurring.
> >
> > What BLM and the other land managers of the Great Basin must do very 
> > soon, is calculate how many years the seeds of the various native 
> > grasses species in the area are viable, let's say 10 years.
> >
> > Then once every five years, rest the land during a good-rainfall 
> > season, completely removing all grazing, to allow the native grass 
> > plants to produce seeds, to replenish the soil-seedbank.
> >
> > Then the ecosystem will be reseeded for free, with the proper local 
> > genetic material, and you won't have to buy those million pounds or so 
> > of exotic seeds that the government purchases for the Great Basin 
> > public lands every year.
> >
> > Sincerely,  Craig Dremann, Redwood City, CA (650) 325-7333
> >
> >
> > _______________________________________________
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> >
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