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

Wayne Tyson landrest at cox.net
Fri Nov 16 17:33:23 CST 2012 

APWG:

Another option is to interplant indigenous species that are known to be capable of suppressing weeds, either as part of a "one-stroke" (transformational) restoration operation or as a two+ phase (transitional) one. In both cases I prefer sterile, relatively short-lived indigenous "pioneer" species so that they won't continue to suppress indigenous species or reproduce; of course, there are always exceptions, depending upon circumstances. I have even been known to use certain alien species for specific functions that I know to be what I call "fast-faders" which do not persist beyond their period of usefulness. By planting such transitional suppressors/habitat modifiers in modest populations with space between them being occupied by other indigenous species, such as slower-growing components or even other pioneer species, most weedy aliens will find it tough going and decline. After all, most aliens are not as well-suited to an undisturbed ecosystem (hence Ewel's criterion of non-invasibility), they will similarly be not so well suited to a recovering one--to a degree roughly proportional to the state of recovery. A downward overall trend of alien population populations and an upward trend of indigenous populations (though populations, per se is not so important as diversity), is the best indicator of restoration project status or success. Measures like "cover" can be misleading, and are related to the site's productive potential and/or transitory or fluctuating environmental state, not necessarily restoration project success. Cover is the easiest thing to achieve; a fully functional, reproducing, diversifying, self-sufficient, permanent biological complex may have a high cover value, but in sites with limited productive potential or carrying capacity, too high a cover value can lead to failure, particularly in arid or otherwise limited sites. 

I like Imlay's idea of the straw patches because my first rule is heterogeneity as opposed to homogeneity, even on sites that appear to be homogeneous, such as grasslands. Dremann's idea of using indigenous (Nasella/Stipa, in his case) straw is an intriguing one, but I would steer clear of the oats, which can have their own "allelopathic" effects. I would, however, only use methods, straw included, that were both most effective and economical. If restoration is too expensive, it will never become popular or widely used. 

In general, I am less concerned about "competition" and more concerned about cooperation and interaction among species and do not want 100 percent of anything (even though I would very much like for alien species to be zero percent, I would not insist upon it; reducing them to a minor component of the species assemblage and with a declining trend-line is good enough for me. I want to restore the entire web of life that existed prior to disturbance and/or as complex an association as the site conditions, sometimes intentionally modified for that purpose, as I can get. For example, I want "grassland" geophytes as well as the entire suite of grass species that made up the original undisturbed site, if possible. In grassland sites, as with other sites, it may take time to reach the levels of complexity and productivity that existed before the disturbance. In areas where biological soil has been removed, for example, part of the restoration strategy will have to include or even emphasize soil-building processes, which can take many years. As the initial restoration project changes habitat conditions, species which might not have survived in the beginning can be added as conditions become more suitable for them. 

Of course, if natives can move back in on their own, so much the better. I have always begun a restoration potential assessment by considering the zero option--what is likely to happen if nothing is done--then working into increasing levels of complexity until only a barely sufficient level of action, resources, time, and money are used. 

As to herbicides, I have never used them, but that doesn't mean that a very limited and highly directed application might not be called for. I would never spray any herbicide where any chance of its touching anything (soil or other vegetation) other than the target plant would be possible. Selectively killing with herbicide without general spraying is nearly always preferable to digging and otherwise disturbing the soil. 

WT


  ----- Original Message ----- 
  From: Marc Imlay 
  To: 'Wayne Tyson' ; apwg at lists.plantconservation.org 
  Sent: Friday, November 16, 2012 4:06 AM
  Subject: RE: [APWG] Ecosystem dynamics and 100 percent suppression by strawapplication Allelopathic straw keeping weeds out & moisturein duringdrought


  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.
  ialm at erols.com
  Natural and Historical Resources Division
  The Maryland-National Capital Park and Planning Commission
  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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