[APWG] Invasion and cropping Re: rate of change
Wayne Tyson
landrest at cox.net
Thu Mar 1 23:50:57 CST 2012
All:
I don't doubt this. No handy generalization is going to be 100 percent true, and again, context is everything. And, of course, not all aliens are equal. But whatever the requirements happen to be for any given species, genotype or ecotype, to the degree that the environment tends to match them, they will come--provided the vectors are up to the job of moving the propagules into position.
But all things being equal (they never are, but sometimes a variable has to be set aside to understand how phenomena operate in their absence), the question remains whether or not a given species is, or tends to be more rather than less dependent upon disturbance for colonization, especially an initial colonization, and whether or not it continues to find habitats adequate for further colonization. Then one should look at things like spread and the conditions that foster it, and the rate of spread and its causes.
Some organisms are going to be "better" at insinuating themselves into new places, but the conditions of habitat are going to have to be suitable. Organisms that evolved under certain habitat conditions are likely to be "better" able to persist in those conditions than those which didn't. For this reason, indigenous species should be able to persist under the long haul--PROVIDED that those conditions stay the same. Disturbances cause change--different conditions which may (for a short or a long time) mean that species adapted to undisturbed conditions may not be able to persist but others, adapted to the different conditions, will. Such conditions may last a long time (e.g., the effects of acid rain--a continuing disturbance), but change when a particular kind of continuing disturbance is reduced or eliminated from the dynamic ecosystem picture. Then (puff, puff,), it is exceedingly difficult to know whether or not a habitat is undisturbed. Again, an organism doesn't "know" whether or not a site is disturbed; it can either "make it" under "those" conditions or it can't.
WT
----- Original Message -----
From: Marc Imlay
To: 'Wayne Tyson' ; 'Ty Harrison' ; 'Michael Schenk'
Cc: apwg at lists.plantconservation.org
Sent: Thursday, March 01, 2012 7:42 PM
Subject: RE: [APWG] Invasion and cropping Re: rate of change
We are finding that typically about half of the invasives are about 20% as bad in natural, undisturbed habitats. Given time we find that they do take over natural areas but at a slower rate. A good example is Japanese Stiltgrass which takes advantage of natural erosion disturbance when a tree comes down naturally but is much worse with artifical erosion disturbances.
Marc Imlay, PhD,
Conservation biologist, Park Ranger Office
(301) 442-5657 cell
ialm at erols.com
Natural and Historical Resources Division
The Maryland-National Capital Park and Planning Commission
www.pgparks.com
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From: Wayne Tyson [mailto:landrest at cox.net]
Sent: Thursday, March 01, 2012 5:53 PM
To: Ty Harrison; Michael Schenk; Marc Imlay
Cc: apwg at lists.plantconservation.org
Subject: Re: [APWG] Invasion and cropping Re: rate of change
APWG:
Relevance, relevance, RELEVANCE! Why do we so often forget this? Context is EVERYTHING. At least without it you are drawing against the Lone Ranger (or arm-wrestling with Superwoman). GIGO!
Most "invasive" species are disturbance-dependent rather than invasive of dynamically stable (dynamic equilibrium state) ecosystems or insinuated into open niches (let the ecosystem without at least some open niches please stand up and be counted). In the Intermountain west and many other areas where grazing and trampling of livestock unlike the indigenous species with which the vegetation evolved, proceeds unabated, cheatgrass and other scabby plants, indigenous and foreign, are bound to attempt to bind up the wounds where Mother Earth has been so scarred, and the scabs are bound to remain in some form for years to come. Pick off the scabs in such cases all you want, Monsantoize it all you will, but as long as the processes that caused the wounds in the first place continue, the scabby cheatgrass and its pals will continue to reform. "Experts" make careers and fortunes pulling rabbits out of the hat, convincing the rubes that the magic will last, but sooner or later the piper will have to be paid. And the rubes invite the experts back for another dose of salts, having refused to take his/her incantations with a grain of it.
WT
----- Original Message -----
From: Ty Harrison
To: Wayne Tyson ; Michael Schenk ; Marc Imlay
Cc: apwg at lists.plantconservation.org
Sent: Thursday, March 01, 2012 12:49 PM
Subject: Re: [APWG] Invasion and cropping Re: rate of change
APWG: I like Tyson's metaphor (sexist?): Whizzing up wind is what many of use are doing rather than using locally relevant ecological models as he recommends. Or as others ecologists have said: weeds and other invaders occupy "emtpy niches in the old corral". But this only goes so far. Many weeds can insinuate themselves into these "empty niches" in disturbance prone (drought?) ecosystems which we have out west (eg. Cheatgrass, Cranesbill, Star Thistle, Dalmatian Toadflax etc. etc. etc.). Ty Harrison
----- Original Message -----
From: Wayne Tyson
To: Michael Schenk ; Marc Imlay
Cc: apwg at lists.plantconservation.org
Sent: Wednesday, February 29, 2012 4:41 PM
Subject: [APWG] Invasion and cropping Re: rate of change
Y'all:
When you change something in an ecosystem, other things change, including "invasions" (aka colonization). Ecosystems tend toward sequestering most or effectively all of the nutrients in the biomass--or try to. Much of colonization consists of a drive in that direction. This is why some ecologists have said that an ecosystem in equilibrium resists invasion. This is a sustained/sustainable situation, but that is far different from the invented and spun context in which "sustainable" is bandied about today.
To cut to the chase, modern agronomic practice is 180 degrees out of phase with this principle, hence with ecosystems. Study sites where the best ginseng grows, and study them completely. Then compare those conditions with the ones in which you are attempting to grow it as a crop. If there is any significant difference, it is likely that you are whizzing upwind.
This is already indulging in more conjecture than justified by the scant information about the ecological context of your project, so take it with a grain of salt and see if any of the principles mentioned help. I hope so.
WT
----- Original Message -----
From: Michael Schenk
To: Marc Imlay
Cc: apwg at lists.plantconservation.org
Sent: Tuesday, February 28, 2012 4:21 PM
Subject: [APWG] rate of change
Bingo! It's the rate of change that counts. When a new species arrives every thousand years, a time scale roughly consistent with "natural" climate change disturbances, the ecosystem has a chance to respond and integrate the new species.
If you keep on rocking the boat and never give it a chance to steady out, somebody's gonna get wet. Sometimes I feel like we're arguing over angel dancing space. The fact is, the boat is swamping, and we need to slow down the rate of change.
I'm a small landholder, trying to plant sustainable harvests of ginseng, etc., in the face of encroachment from garlic mustard, stiltgrass, tearthumb. I don't have the time or resources for massive intervention. I need affordable, time-efficient methods of non-toxic removal. I've already spent hundreds of hours and many dollars on weedwhackers and native seed. For me, the combination of mechanical removal and planting native grasses is at least holding the stiltgrass steady. I'd like to learn about other successful practices that fit with a modest budget and a working schedule.
Cheers,
Mike
-----Original Message-----
From: Marc Imlay
Sent: Feb 28, 2012 7:35 AM
To: "'Hempy-Mayer,Kara L (CONTR) - KEC-4'" , apwg at lists.plantconservation.org
Cc: rwg at lists.plantconservation.org
Subject: Re: [APWG] [RWG] Ecosystem Restoration Collapse
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