[APWG] Do ecosystems resist invasion?

Ryan McEwan the.tsuga at gmail.com
Fri Mar 2 08:45:45 CST 2012 

Hi John,

I think this notion is derived from the fact that many invasive species do
well following disturbance.  Many invasive plants, for example, have
population biology traits that help them arrive on distubed sites (e.g.,
long distance dispersal) and proliferate in the presence of the abundant
resources that are available in such locations.  There is also the notion
of the "empty niche" in invasion ecology which suggests that species do
well when they invade habitats where there is "niche space" available due
to the absence of a native species.  Of course, that native species might
have been made absent by some process that leaves the system less than
"intact."

What this generally means is that if you were to compare a large landscape,
you would very likely find that disturbed sites have many more invasive
species that areas that have been carefully preserved.

Sadly, this is NOT an indication that the "intact" preserves are
"invasion-proof."  In fact, what I think we are finding is simply that the
rate of spread into more intact systems is slower than for disturbed
sites.  Slower rate, but the invasives are still penetrating, inexorably in
many cases.

The other issue here is the whole idea of an "intact" ecosystem doesnt
really hold up under scrutiny.  The fact is that all ecosystems experience
"disturbances."  Old-growth forests, for instance, have tree-fall gaps that
are a crucial part of the ecology of those systems.  These gaps can be
invaded.  Does a tree-fall gap make the system less "intact"  especially if
that is a crucial, indeed, descriptive piece of the systems ecology?  I
think not.  Same could be argued for a riparian systems and flooding.
Surely flooding is part of the system's basic biology- can we say it is
less "intact" then when a flood occurs?   There are a spectrum of potential
disturbance processes that influence any ecosystem.  So the idea of
"intact" is relative.

 My two cents:  sites that are massively disturbed are very likely to be
invaded by species with a "weedy" population biology, and in many cases the
best members of that flora/fauna are invasives.  Sites that are less
disturbed, are likely more "resistant" but invasives certainly can, and do,
penetrate those systems.

Ryan

 --
Ryan W. McEwan, PhD
Assistant Professor
Department of Biology
The University of Dayton
300 College Park, Dayton, OH  45469-2320

Email:  ryan.mcewan at udayton.edu
Lab:    http://academic.udayton.edu/ryanmcewan



On Fri, Mar 2, 2012 at 12:02 AM, John <jmbarr at academicplanet.com> wrote:

> With all due respect, and not to be a bother, but ...... I'd like to
> question the notion that intact ecosystems resist invasion, but I do not
> know who proposed it nor what evidence they have for it.  None the less I
> hear it bandied about again and again.
>
> Questions:
> 1) How does any species ever colonize an island?  Aren't the island's
> ecosystems as "intact" as any other?
> 2) Fire ants like many invasives arrived in North American (and around the
> globe) without their natural adversaries.  How can a native fire ant
> "resist" invasion when they have long developed adversaries and the
> invasive species has none?  This same pattern is repeated again and again
> with species after species, else why would "biocontrols" be effective or
> even considered?
> 3) I fear a circular argument, invasion occurred, hence the ecosystem was
> not intact.  Is there any ecosystem that is intact?  Really, with very few
> exceptions, if you name an ecosystem, I bet I can find: A) a prior human
> impact on that ecosystem and B) a species that will successfully invade.
>
> Enlighten me, please......is there scientific evidence for this notion?
>
> john in Austin
>
>
>
>
>
> On Mar 1, 2012, at 2:49 PM, Ty Harrison wrote:
>
>  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 <landrest at cox.net>
> *To:* Michael Schenk <schenkmj at earthlink.net> ; Marc Imlay<ialm at erols.com>
> *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 <schenkmj at earthlink.net>
> *To:* Marc Imlay <ialm at erols.com>
> *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
>
> ****************************************
> *Just to clarify, ecosystems are dynamic and constantly changing, but not
> at the present rate of change. When endangered species were protected with
> national and international laws and programs several decades ago, we agreed
> that species naturally become extinct over time. It is just the rate of
> extintion that had increased a thousand fold and needed to be reversed so
> new species had an ecosystem to evolve in.*
> **
> *
>  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
>
> *
> **
>  ------------------------------
> *From:* apwg-bounces at lists.plantconservation.org [
> mailto:apwg-bounces at lists.plantconservation.org<apwg-bounces at lists.plantconservation.org>
> ] *On Behalf Of *Hempy-Mayer,Kara L (CONTR) - KEC-4
> *Sent:* Monday, February 27, 2012 2:14 PM
> *To:* 'apwg at lists.plantconservation.org'
> *Cc:* 'rwg at lists.plantconservation.org'
> *Subject:* Re: [APWG] [RWG] Ecosystem Restoration Collapse
>
>  Agreed.  I’ve heard many people argue against the ideas of “ecosystem
> preservation” and “restoration,” but it’s usually a matter of semantics.
> What restoration and preservation are trying to accomplish is to maintain
> diversity on a global scale: there are ecosystems here that worked well
> before we starting impacting them so profoundly: we attempt to “restore”
> them by taking out what we put in (exotic weeds), or trying to repair what
> we damaged (soil structure, hydrology, etc.).  Then, hopefully, the
> previous ecosystem processes can reestablish.****
> ** **
> As to the argument about increased carbon dioxide levels: I’ve always
> wondered about this.  The argument that increased CO2 in the atmosphere has
> a profound effect on plant growth assumes that nothing else is limiting
> plant growth. From my limited background in plant physiology, there are
> usually many things limiting plant growth: macronutrients, micronutrients,
> water, and light.  In balance, can CO2 have that big of an effect, even if
> it is limiting? Are there field studies that have found evidence for this?
> ****
> ** **
> Thank you for the opportunity to comment -Kara****
> ** **
>  *From:* apwg-bounces at lists.plantconservation.org [
> mailto:apwg-bounces at lists.plantconservation.org<apwg-bounces at lists.plantconservation.org>
> ] *On Behalf Of *William Stringer
> *Sent:* Monday, February 27, 2012 8:41 AM
> *To:* Robert Layton Beyfuss; Katie Fite; Wayne Tyson
> *Cc:* apwg at lists.plantconservation.org; rwg at lists.plantconservation.org
> *Subject:* Re: [APWG] [RWG] Ecosystem Restoration Collapse****
> ** **
>  As to ecosystem restoration , we are not proposing to make a man-made
> Hope Diamond here.  We are proposing to work from our admittedly limited
> knowledge base of what should be there, and what should not.  We take out,
> to the degree that we can, the should-nots, particularly the known exotic
> invasive should-nots.  We then try to place into the site local-source
> propagules of known natives in a patchwork of mixtures of relatively
> compatible species.  At that point we have probably done most of what we
> can contribute.  We can manage the site to the degree that we can simulate
> natural disturbance phenomena.  But mostly at this point we stay out of the
> way and let natural phenomena drive the restoration.  The only exception
> would be if outbreaks of exotic invasive species begin to threaten.  Then,
> we monitor and learn****
>   ****
>  What we cannot do is let micro-analysis of the term restoration
> immobilize us into total inaction.****
>   ****
>  Bill Stringer****
>  ------------------------------
>
> *From:* apwg-bounces at lists.plantconservation.org [
> apwg-bounces at lists.plantconservation.org] On Behalf Of Robert Layton
> Beyfuss [rlb14 at cornell.edu]
> *Sent:* Monday, February 27, 2012 10:26 AM
> *To:* Katie Fite; Wayne Tyson
> *Cc:* apwg at lists.plantconservation.org; rwg at lists.plantconservation.org
> *Subject:* Re: [APWG] [RWG] Ecosystem Restoration Collapse****
>  I do not understand how ecosystems can be restored since I consider them
> as dynamic and constantly changing. It is not possible to completely
> re-create the environmental conditions that led to a given ecosystem at any
> given time in the past. If ecosystems represent the interactions of living
> and environmental factors, to restore an ecosystem requires replicating the
> previous environmental factors that affect the living organisms. The level
> of carbon dioxide in our atmosphere has doubled in the past 80 years. Plant
> growth, reproduction and survival is profoundly affected by carbon dioxide
> levels. I consider attempts to restore ecosystems  as  no more than human’s
> creating new ecosystems using species of plants that previously occurred
> because humans liked the previous once more than the current one.    ****
>  ****
>  *From:* apwg-bounces at lists.plantconservation.org [
> mailto:apwg-bounces at lists.plantconservation.org<apwg-bounces at lists.plantconservation.org>
> ] *On Behalf Of *Katie Fite
> *Sent:* Monday, February 27, 2012 9:12 AM
> *To:* Wayne Tyson
> *Cc:* apwg at lists.plantconservation.org; rwg at lists.plantconservation.org
> *Subject:* Re: [APWG] [RWG] Ecosystem Restoration Collapse****
>  ****
>
> Wayne,
>
> I am interested in the discussion.
>
> And discussions of what ecological restoration is, and also discussions of
> how the term "restoration" is currently being used by agencies or at times
> industry  -  to describe imposing major disturbances on mature or old
> growth woody vegetation communities  - with such disturbances often then
> leading to weed invasions.
>
> Katie Fite****
> ****
> ****************************
>
>  ------------------------------
>
>
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