[APWG] Ecosystem dynamics and 100 percent suppression by strawapplication Allelopathic straw keeping weeds out & moisturein duringdrought

Fri Nov 16 06:06:18 CST 2012

One option is to use the straw application on the worst, and relatively
small, patches of invasives, and use less harmful traditional treatments
around the severely treated spots so that natives can move back in over a
five or ten year period. 

Marc Imlay, PhD,
Conservation biologist, Park Ranger Office
Non-native Invasive Plant Control coordinator.
 <mailto:ialm at erols.com> ialm at erols.com
Natural and Historical Resources Division
The Maryland-National Capital Park and Planning Commission
 <http://www.pgparks.com/> www.pgparks.com

-----Original Message-----
From: APWG [mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of
Wayne Tyson
Sent: Wednesday, November 14, 2012 4:37 PM
To: apwg at lists.plantconservation.org
Subject: [APWG] Ecosystem dynamics and 100 percent suppression by
strawapplication Allelopathic straw keeping weeds out & moisturein
duringdrought

I have never seen 100 percent suppression of vegetative growth by anything,
much less straw. I once concluded (erroneously) upon seeing a highly
disturbed site "full" of the "worst" possible assemblage of alien weedy
species I had ever seen, that it was "100 percent" devoid of any indigenous
species after conducting a very cursory but pointed point/quadrat survey of
the area, I soon discovered how wrong I was. Down between the weedy species
I started finding small stands of "re-invading" indigenous species,
successfully slugging it out with the weeds. Where these stands occurred,
the invasives were clearly suppressed or entirely absent.

If Dremann cannot or will not cite the specific mechanisms of action
relevant to the particular project he cites, I must continue to suspend
belief until he supplies more evidence. I find his direction to a website
insufficient to support his claims; moreover it is patronizing. I am well
aware of the suppressive action of "shade," "robbing water," and "robbing
nutrients," but am aware of no chemical action which has been demonstrated
to be any percent effective in suppressing any weed growth, much less 100
percent. I stand ready to be corrected and educated, based upon evidence and
directly relevant scientific/scholarly/disciplined research. "Many" does not
reveal what mechanisms of action are responsible for the claimed 100 percent
suppression of the species Dremann mentions.

I do agree with Dremann that "straw," including that of standing or
prostrate alien species, can be protective of surface evaporation as well as
contribute to water infiltration and other beneficial effects. However, the
presence of any straw can have adverse effects upon emerging vegetation as
well. For example Robinson (????) studied this effect upon Stipa (Nasella)
pulchra (dissertation at the University of Oklahoma, if my memory serves me
correctly), and found that Stipa seedling survival was very low under such
conditions. This, combined with our own observations, led us to develop the
technique of planting very small seedlings in small colonies into the
weed-infested areas. The colonies expanded, albeit slowly, in our
experimental plots. We were never able to finish the large-scale project. We
developed a unique planting method that was very cheap (as were the small
seedlings), and, in terms of actual long-lasting results much more effective
than mass-sowing, using far less seed, thus minimizing the depredation of
wild stand seed stocks by over-collecting. As this work was never properly
completed, we never published on it; however, we did mark the plots with
buried iron markers that could probably be located with a metal detector
today, some 32 years later, should anyone be interested in a follow-up.

WT

----- Original Message -----
From: "Craig Dremann - Redwood City Seed Company" <Craig at astreet.com>
To: <apwg at lists.plantconservation.org>
Cc: <craig at street.com>
Sent: Tuesday, November 13, 2012 1:10 PM
Subject: [APWG] Allelopathic straw keeping weeds out & moisture in
duringdrought

> Dear Wayne and All,
>
> Thanks for your email.  I will comment below your email:
>
> Wayne--The grass-straw mulch is an interesting idea, and I certainly
> don't doubt that such a practice might have some utility in
> suppressing weeds, but I am concerned about suppression of indigenous
> species as well.
>
> Craig--Native grass and wild oats straw are being used on a site that
> has been 100%  devoid of any natives for the last 12 years of
> monitoring, and you can see a painting of the site at
http://www.ecoseeds.com/art3.html.
> Since the straw is 100% effective against annual weed grasses like
> cereal rye, Medusahead or cheatgrass, plus annual thistles like
> Italian and Yellow Star, I do not recommend straw to be used in areas
> where native seeds might still be in the soil seedbank.
>
> I wonder just which "allelopathogens" are responsible for the observed
> effects? What is their mechanism of action?
>
> There are many  Journal of Chemical Ecology articles an
> allelochemicals, that you can access through http://scholar.google.com
> and Dr. Liu and his team have been important authors since the early
> 1990s studying the allelochemicals involved.  His work was the first
> to sort out the allelochemical effects from the other plant
> suppression effects, like roots robbing water, or stealing nutrients,
> or shading of one plant by another, etc.
>
> Since most of the USA is in severe drought mode again, that you can
> see at http://droughtmonitor.unl.edu/ the straw mulch is keeping the
> soil surface moisture in place for much longer, perhaps twice as much
> moisture today--while we have a dry 40% relative humidity, barometer
> reading 30.20 inches (no rain for a while),  and no dewfall at
> night--than in areas that do not have any mulch.
>
> Sincerely,  Craig Dremann (650) 325-7333
>
>
>
>
>
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