[APWG] Ecosystems Invasions Re: Do ecosystems resist invasion? Invasion and cropping Re: rate of change

Mon Mar 5 09:58:36 CST 2012

It is interesting to see how the discourse on this list serve has evolved over the past years in a positive manner. It seems that years ago many of the posts had to do with eradication efforts of invasives and not much else "I.e. Florida school children wage war on invasive exotic plants"  and similar stories. Posters were produced with pictures of plants that were to be "killed on sight". I recall attending a workshop years ago in West Virginia where a manager who worked for the Nature Conservancy showed slides of a helicopter indiscriminately spraying glyphosate (Round Up) over 50 acres of wetlands with the rationalization that since there were so many invasive species present there now, the only hope was to kill off everything and let "nature" start over from scratch. I could not distinguish this activity greatly from the coal companies removing entire mountain tops and allowing nature to start from scratch. Indeed this policy is still practiced in many situations, regrettably. I am pleased to see more and more posts that think beyond this.

From: apwg-bounces at lists.plantconservation.org [mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of Wayne Tyson
Sent: Friday, March 02, 2012 7:00 PM
To: Ryan McEwan; John
Cc: apwg at lists.plantconservation.org
Subject: [APWG] Ecosystems Invasions Re: Do ecosystems resist invasion? Invasion and cropping Re: rate of change

Y'all:

The excellent contributions to this subject continue to come in--and to think some had lost faith in this listerv and skedaddled. (At least some told me off-list that they were so disappointed with the quality of the discourse that they were leaving.)

This is a good time to thank Olivia for maintaining this list. THANKS, Olivia!

Ryan makes good points; I'll respond within his text below [[thus WT]]. I hope we continue to get further inputs like this.

But here are some overall observations for what they might be worth . . .

1. "Ecosystems" that are referred to as such in the plural are really convenient subdivisions of living organisms that we believe to be distinguishable from other "ecosystems." There always is a certain amount of overlap, sometimes a little, sometimes a lot. The real phenomena don't "care" one whit how we define or divide them, we do.

2. "Invasions" are just how ecosystems work. Disturbances, and the colonization of changed places by organisms different from the ones which previously occupied the space of interest are just the way the world works. Mine tailings and landslides, even volcanoes, have something in common--they radically change the ecosystems that existed before the disturbance.

The early colonists, or "pioneer species," are organisms whose requirements are met by the changed environment and which have a means of dispersing into the new niches/environments. Those species whose needs are not met by the changed environments/habitats tend not to succeed, but if their propagules continue to "try," there may come a time when, after further changes, that they, too, may establish successful individuals or colonies, and so on. This has been called "succession," but I'm not fond of the term, because I believe that there is no convincing evidence that organisms "succeed" each other. In my view, all is adaptation to change, and change is in the details--some of which we may know, some which we don't know.

The "invasions" which concern "invasion ecologists/biologists" tend to be undesirable for some reason(s), and sometimes it's just because the organism is new to the neighborhood, as it were, an "alien." But the underlying processes are essentially the same. Invasions of "intact" ecosystems are often the result of culture in action, humans acting as propagule vectors and cultivators of conditions favorable to the "undesirables." We (myself included) tend to favor indigenous wildflowers, for example, over the stickery annual grasses that have replaced them and persist to the detriment of the previous occupants--and even systems far away, by altering things like hydrology and fire.

In "undisturbed" ecosystems, say, following a tree-fall, "pioneer" species (some indigenous, some "alien") typically move in to colonize the changed environment/habitat. Plants that do this are often those that have evolved to occupy such sites and will, in time, fade away, or undergo population decline and reduction in fecundity. This phenomenon can be interpreted as "resistance to invasion," and is commonly one of the goals of most restoration projects.

This condition is one desired by invasion biologists, but for some reason not all IB's use this phenomenon to their advantage. For some reason, some IB's believe that simply killing the undesirables is their only option. One problem with not letting succession play out is that the conditions produced by whacking and digging and spraying and such is that the changes that the succession process produces don't happen at all or are greatly reduced, prolonging a return to "normal." Sometimes it makes things worse for indigenous species and better for the alien colonists.

----- Original Message -----
From: Ryan McEwan<mailto:the.tsuga at gmail.com>
To: John<mailto:jmbarr at academicplanet.com>
Cc: apwg at lists.plantconservation.org<mailto:apwg at lists.plantconservation.org>
Sent: Friday, March 02, 2012 6:45 AM
Subject: Re: [APWG] Do ecosystems resist invasion?

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 disturbed sites (e.g., long distance dispersal) and proliferate in the presence of the abundant resources [[Since "intact" ecosystems tend to sequester almost all of the available nutrients, the resulting paucity of available nutrients may be one factor in producing resistance to invasion; on the other hand, the death of plants, including weeds, tends to release sequestered nutrients, thus helping the invasive aliens to succeed, reproduce, and disperse. WT]]  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." [[My own definition of "niche" is a bit different from that, perhaps classical definition. I don't see niches so much as places as I do conditions favorable to organisms. If others differ, I would like to hear more about the reasons for other definitions. I do, however, believe that it's appropriate to speak of niches as places where conditions favorable to organisms exist, and that certainly can be valid for places like tree-fall areas being opened up niches for colonizing species, alien or indigenous. Such places are self-evident when one finds weeds where windfalls throw up a pile of subsoil. Clearly, such conditions are suitable for the weeds released N, broken mycorrhizal mat, more light, etc. WT]]

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. [[Here we need some detail. What, for example, is slowing the spread in the "intact" ecosystems of the preserve. WT]]  Slower rate, but the invasives are still penetrating, inexorably in many cases. [[Yes, I have seen such phenomena, but the mechanisms involved, hence the right kind of management, don't seem to exist. I suggest that under such conditions we might guess wrong, whereas with better information, we could avoid doing wrong. Again, details. WT]]

The other issue here is the whole idea of an "intact" ecosystem doesn't really hold up under scrutiny. [[As discussed earlier, it's not yes or no, it's the DEGREE of "intactness." WT]]  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? [[It may indeed be descriptive, but it remains an observation, not an explanation of the mechanisms. WT]]  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. [[Agreed. In fact, many weeds evolved under the disturbance regime of floods. But look at relatively undisturbed riparian areas--how is it that they are still as "intact" or functional as they may have been prior to the invasion of Europeans in the 15th century? WT]]

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. [[I understand the logic and the "evidence." But I think we need to know more about the mechanisms. Further, I think ecologists are kidding themselves about the adequacy of observations that are limited to the external phenomena and may be a bit hasty about drawing final conclusions about cause and effect. That is, they need to get more "scientific" as well as observational. Spoken as a compulsive observer who has himself so sinned. WT]]

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<mailto: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<mailto: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<mailto:landrest at cox.net>
To: Michael Schenk<mailto:schenkmj at earthlink.net> ; Marc Imlay<mailto:ialm at erols.com>
Cc: apwg at lists.plantconservation.org<mailto: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<mailto:schenkmj at earthlink.net>
To: Marc Imlay<mailto:ialm at erols.com>
Cc: apwg at lists.plantconservation.org<mailto: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<mailto:apwg at lists.plantconservation.org>
Cc: rwg at lists.plantconservation.org<mailto: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<tel:%28301%29%20442-5657> cell
 ialm at erols.com<mailto:ialm at erols.com>
Natural and Historical Resources Division
The Maryland-National Capital Park and Planning Commission
www.pgparks.com<http://www.pgparks.com/>

________________________________
From: apwg-bounces at lists.plantconservation.org<mailto:apwg-bounces at lists.plantconservation.org> [mailto: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<mailto:'apwg at lists.plantconservation.org>'
Cc: 'rwg at lists.plantconservation.org<mailto:'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> [mailto: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<mailto:apwg at lists.plantconservation.org>; rwg at lists.plantconservation.org<mailto: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<mailto:apwg-bounces at lists.plantconservation.org> [apwg-bounces at lists.plantconservation.org<mailto:apwg-bounces at lists.plantconservation.org>] On Behalf Of Robert Layton Beyfuss [rlb14 at cornell.edu<mailto:rlb14 at cornell.edu>]
Sent: Monday, February 27, 2012 10:26 AM
To: Katie Fite; Wayne Tyson
Cc: apwg at lists.plantconservation.org<mailto:apwg at lists.plantconservation.org>; rwg at lists.plantconservation.org<mailto: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> [mailto: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<mailto:apwg at lists.plantconservation.org>; rwg at lists.plantconservation.org<mailto: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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