Invasive plants

The various Rhamnus (cathartica, frangula) are weedy here as they are with you. And we share a few other nuisances (Ailanthus for instance) but that bad weedy woodies of the midwest (Ginnala maples, Norway Maple, Barberries, Japanese Lonicera) just don't seed around here. I grant you the barberry in the Rock  Alpine Garden was planted thusly, but I have never seen another anywhere hereabouts...and there just aren't woodlands on the Plains!

Our really bad woodies are Siberian Elms and Red Mulberry: and I have never heard anyone suggest mounting a campaign against these (and the nurserymen are wise enough not to sell them or the Rhamnus any longer)...

Our worst iweeds (cheatgrass and all the classic rabble of chenopods and suchlike) were hitchhikers on crops.

We horticulturists can sleep soundly in the Rockies! It's the agronomists who should be having nightmares (and developers, miners and recreational vehicle yahoos who tear up the desert)...

"and there just aren't woodlands on the Plains!"

In areas where the ranchermans fire cannot spread woody species will invade.  If this was not the case then you would not have Siberian Elm or Red Mulberry.

"Our really bad woodies are Siberian Elms and Red Mulberry: and I have never heard anyone suggest mounting a campaign against these (and the nurserymen are wise enough not to sell them or the Rhamnus any longer)..."

We control Siberian Elm and White Mulberry in natural areas.  Red Mulberry is a rare native species.  It apparently lives in my area, but I have never seen one.  I sure wish I could get rid of some Siberian Elms neighboring nature preserves.  It is amazing that people could want to keep trees that are always half dead at maturity.

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Why is it that so many invasive species have thorns? 

Because cattle can't eat them.

Bob

Bob,

    That was a rhetorical question.  Anyway, we do not have cattle around here.  Cattle have been excluded from our local natural areas long before most invasive species were introduced.  Even though there are no cattle, we still have lots of thorny invasive species. 
    I actually wish the forest preserves would rotationally stock cattle into some of our prairie restorations.  Cattle reduce the dominating grasses resulting in more wildflowers.
    The one thing we do have is an over abundance of deer.  At least they seem to like to eat buckthorn.  While controlling buckthorn in our forest preserves deer have been known to approach work crews to browse the branches they are piling.  There lack of fear from hunger gives you an idea of just how over populated they have become without any predation.
    Oddly enough, goats have actually been employed in some instances to help control invasive species.  Goats apparently do the job because they will eat just about anything.
    Anyway, the real driver of plant diversity appears to be microbes.  Unfortunately, we know very little about these life forms.  The lack of pathogenic microorganisms in a new environment is probably the reason introduced species often dominate everthing else.  The thorns are now only an evolutionary relict that helped these invasive species survive in their original habitat.

James

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Cattle reduce the dominating grasses resulting in more wildflowers

Cattle reduce the dominating grasses, allowing invasive grasses to take over. Note also that the USDA does not consider smooth brome (Bromus inermis) to be an invasive species. Cattle can eat that.
This is an excellent website discussing invasive plants that does not consider the primary agent of invasion to be off limits in the discussion http://www.sagebrushsea.org/

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The one thing we do have is an over abundance of deer.

Probably because of extensive predator control in the past.

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the real driver of plant diversity appears to be microbes

  If by "microbes" you mean "human beings", yes, I would agree, especially if "and their diet" were added.
There's a Zen saying, "What was your face like before you were born?", which in this case I would modify to "What was your neighborhood like before your house was built?" Why is it important to preserve "the last few remaining natural areas" now, instead of doing it then? My neighborhood is surrounded by a sea of smooth brome and cheat (Bromus tectorum) that almost certainly would not have been there had the neighborhood not been built.
Berberis thunbergii is almost certainly resistant to soil-borne pathogens which is why it's a common garden plant, but then, conversely, most of the plants in the communities in which it's invading are probably resistant too. (A good way to find this out is to see if they're easily growable in an ordinary garden.) The barberry is what ecologists would call a "generalist". But whether or not it's driving out the native (or what's perceived as native by people who just moved to the area) flora is a matter of aesthetics, unless it can be shown that the "specialists" (plants with specific microbial associations, for instance) are being killed off.
The barberry, by the way, is now believed to be an alternate host of the wheat rust Puccinia graminis and I understand has been banned in Canada. That could be its fate in the U.S., too.

Bob

I've been reading 1491 the last few weeks: a slow read because it is very rich in information and beautifully written: I'm nearing the end with some sadness: one of the best books I have read in a long time. It is extremely thought provoking. The thesis, basically, is that native Americans had a much higher population than hitherto assumed throughout the continent, and that the level of their sophistication and civilization was much higher as well. The sections on Peru and the Amazon are nothing less than revelatory for me: I was totally ignorant of those amazing preColumbian civilizations (aside from Inka).

A constant leitmotif throughout the book, and one that struck postively Bachian chords within me, was the extent to which the landscape throughout the Western Hemisphere was deliberately, extensively, and massively modified, managed and molded by native Americans.

The whole "invasive" issue is largely obviated if you think about the extent to which our "native landscape" (an oxymoron of histrionic proportions) was utterly devastated when several dozen megafauna were eliminated in a geologic nanosecond by the first peoples, and when they udeveloped a massive fire management strategy throughout the hemisphere to encourage the adapted megafauna (mostly Eurasian immigrants like the people) for optimal Protein intake. There is no such thing as nature (as Nabokov said, "Reality" should always be in quots--so too "nature": the book contains well documented evidence that vast swaths of Amazonia were carefully planted and crafted by native peoples for optimization of fruit and seeds.

Until we come up with a deliberate vision of how to maintain our "natural" landscapes, so-called invasives will be the norm. They are in fact nothing less than NATURE (you can also capitalize her: assuming she exists) herself, seeking to clothe her body ravaged by human abuse. Within a few generations, I believe most of these "invasives" will become naturalized and integral elements of our landscapes because that's what Nature does to monocultures: she tames them. I have faith in Nature (Capitalizing the first letter is as good as quotation marks)but not so much in Humanity! The issue is the ongoing disturbance by farming and heavy machinery due to construction activities, mining, petroleum development, pipeline burial, telecomunication burial, etdc. etc. etc. etc. [we gardeners are puny players in comparison with those macho men]: real conservationists should concentrate on demanding and instituting revegetation regulations for disturbed habitats rather than trying to instill guilt in horticutlurists...AHEM! That is my last word on this tedious and tendentious subject.

Bob,

    I am not familiar enough with the ecology of the sage brush step ecosystem to comment authoritatively on the impacts of cattle grazing.  I do believe the statement that grazing is facilitating the invasion of smooth brome and cheat grass.  The fact that these grasses create enough fuel to carry fire is an additional problem.  I have read that unlike midwestern ecosystems, the sage brush step is not adapted to fire. 
    In contrast, the tallgrass, mixed grass, and short grass prairie are well adapted to fire and grazing.  The research at Konza Prairie has demonstrated this fact conclusively.  The problem is not grazing, but plowing and herbicide application.  Eliminating everything cattle do not eat may increases productivity (at least temporarily), but it also completely destroys biodiversity.  In my area Smooth Brome and Cheat Grass are limited to disturbed areas.  Herbicide application or plowing has preceded the planting of Smooth Brome or Cheat.  The destruction of the native plant community is what has allowed these species to dominate.
    As to your comment about Japanese Barberry, I have seen it completely dominate woodlands.  It seems arguing about generalists and specialists seems moot when nothing remains but Japanese Barberry and a few trees that are now unable to reproduce.

James   

Dear Panayoti,

    I see you are still making excuses.  I do feel for you.  When I moved to my house I removed Japanese barberry and burning bush from my landscape.  It was easier because I did not plant them.  I know it is hard.  I now have holes in my shrub border that will take years to fill, if I ever decide on replacements. 
       
You wrote ...

"I believe most of these "invasives" will become naturalized and integral elements of our landscapes because that's what Nature does to monocultures: she tames them. I have faith in Nature (Capitalizing the first letter is as good as quotation marks)but not so much in Humanity!"

Do you really believe this?  Or is this just something you tell yourself so you can feel better?  This belief is as unfounded as the Native American belief that the "Ghost Dance" would get rid of all the white people.  I think you know how badly that one ended.

"[we gardeners are puny players in comparison with those macho men]"

Actually, invasive species rank just after habitat destruction as a threat to species loss.  I have already listed the many invasive species that were brought to my region for gardens in a previous post.

... real conservationists should concentrate on demanding and instituting revegetation regulations for disturbed habitats rather than ...

The fact is, once it is gone it cannot be brought back.  Restoration efforts have had their successes, but they never reach the quality of an intact remnant.

James

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In contrast, the tallgrass, mixed grass, and short grass prairie are well adapted to fire and grazing.  The research at Konza Prairie has demonstrated this fact conclusively.

In a reserve. Not in real life. Bison moved around the prairies, allowing grasses to regrow without human intervention; cattle are stationary.
Introduction of non-native grasses increases the fire potential. The vectors of introduction are grazing and development.

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It seems arguing about generalists and specialists seems moot when nothing remains but Japanese Barberry and a few trees that are now unable to reproduce.

That's why it was important to save the areas invaded by the generalist barberry before it was allowed to start seeding.

Bob

Bob,

    Cattle are far from stationary.  They selectively graze newly burned areas.  This patch burn grazing regime causes them to move around (just like historically occurred from bison).  The unburned areas that are ignored by cattle give the grasses time to recover.  It is an ever shifting balance that must occur for the highest level of biodiversity to be maintained.
    Previously you posted a link about Sage Grouse.  The Greater Prairie Chicken has been found to disappear without grazing management.  This species requires the shorter structure created from grazing management for its survival.  The shift away from patch burn grazing in Illinois has nearly lead to the disappearance of Prairie Chickens from my home state.
    As for nonnative grasses increasing fire potential, it is actually about the opposite in my area.  A field of Big Bluestem will go off like a bomb when ignited during prime fire conditions.  You would have trouble being closer than 30 yards from these intense flames.  We make sure we have good fire breaks and hope we do not an emergency requiring us to put it out.  In contrast, cool season grasses like Kentucky Blue grass and Fescue do not burn well at all.  They are still green during prime fire conditions.

    As for saving areas before they get invaded, we are trying.  We keep an eye out for invasive species in our natural areas and remove them before they have a chance to take over the entire habitat.  If we remove invasive species from an otherwise undisturbed habitat we have repeatedly observed an impressive recovery of the native vegetation.  We do our best.  Most is of the labor is volunteers.

James

Although some of my neighbours have cattle (the Scottish Highland type  or kyloe) grazing outside all winter I am fortunate not to have them in my garden. Selective or not . . .The slugs I do have are always selectively choosing the dearest plants I have!

Although the weather is rather mild - the mean temperature is about 8C warmer than last November and 3C warmer than the November mean - it is not many of the "old" plants that still flower. However, some have started their spring growth as these Hellebores show.

Hoy,  Although I would also not graze cattle in my garden, here is a site discussing the importance of grazing for some cherished European species.

http://www.whitecliffscountryside.org.uk/index.php?id_sec=79&id_sub=3

James

James wrote:

Hoy,  Although I would also not graze cattle in my garden, here is a site discussing the importance of grazing for some cherished European species.

http://www.whitecliffscountryside.org.uk/index.php?id_sec=79&id_sub=3

James

Thanks, James. However I am aware of the benefits of grazing and also of the importance of maintenance of cultural landscapes. Here's an example, all summer cattle graze to keep the grass and shrubs down. It is not a farm any more but a protected area.

Hoy,  In retrospect I now understand the teasing.  Also, thanks for demonstrating the idea with an excellent example.

James 

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Cattle are far from stationary.

Cattle are stationary. They are not allowed to roam freely, like bison did, anywhere in North America. That's why barbed wire was invented.
The selective grazing you mention is the result of human intervention and not a replication of a natural situation, since cattle, unlike bison, are property. They might be able to replicate the actual act of mowing down grasses, but then, so could a lawn mower.

Bob