earthworms destroying forests

Discussion in 'Conversations Forum' started by chuckrkc, Sep 10, 2006.

  1. chuckrkc

    chuckrkc Active Member

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    Here is something I found on the Brooklyn Botanical Garden Web site.

    Niall Dunne writes (http://www.bbg.org/gar2/topics/essays/2004su_worms.html) that exotic earthworm species, dumped by sport fishermen at the end of an fishing trip, are destroying North American forests. The worms speed up the decomposition of the leaf mulch on the forest floor, making the soil too nitrogen rich and clearing the ground for other plants to take root and compete with the native forest plants.

    More at Minnesota Worm Watch (yes, I am amused by the title): www.nrri.umn.edu/worms/default.htm

    I never thought of earthworms as anything but good. Vermicomposting takes a hit, and I thought it was as close to delightful organic gold as I could get.

    It also stirs up the more broad native-exotic debate in my skull.
     
  2. Ron B

    Ron B Paragon of Plants 10 Years

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    Playing musical chairs with organisms can really backfire. One earthworm is not the same as another. Ecosystems develop over very long periods of time and can be extremely prone to disruption. Seemingly minor alterations can spoil the whole dress.
     
  3. chuckrkc

    chuckrkc Active Member

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    I see the point. In the case of fishermen, they need to make sure unused bait is dumped in the lake or river, I understand from the Web sites.

    But how far do you carry the metaphor? No non-native introductions? No plants from Asia transplanted here? We're talking about an industry here and a bunch of us lunatic gardeners going crazy over each introduction. What about prairie grasses transplanted to Woodland regions?
     
  4. chuckrkc

    chuckrkc Active Member

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    From Dunne's article: "In The Earth Moved (Algonquin Books, 2004), a wonderful new book on earthworms by Amy Stewart, forest ecologist Cindy Hale advises worm composters to freeze their castings in air-tight bags for a least a week before adding them to garden soil, no matter what worms species they use. 'It won't hurt the soil microbes, but it will kill all the worms.' "

    My freezer collects a lot of things that require explanation to housemates.
     
  5. Ron B

    Ron B Paragon of Plants 10 Years

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    I'm not a Natives Nazi. You have to be careful with plants that may seem to have invasive potential. This can be hard, maybe impossible to predict. That is part of the problem, since ecosystems are complex exposing one to a new organism may have unimagined consequences. Most garden plants do not spread into the woods or onto the prairie, but the minority that have become pests are the cause of much trouble and expense.

    It's like most issues, it seems, polar positions are not the most reasonable. A compromise between Anything Goes and Use No Foreign Organisms will probably be best.
     
  6. chuckrkc

    chuckrkc Active Member

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    I am a compromiser, too, though I fear that is just a rationalization because I want a hydrangea serrata in my garden and hope none of my gardening buddies has one.
     
  7. angilbas

    angilbas Active Member

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    The New York Times published Anne Raver's "The Dark Side Of a Good Friend To the Soil," on March 15, 2007. It expresses concern about the effects of earthworm invasion on forest soils and ecosystems. At least some of Raver's concerns, however, seem to be exaggerated.

    Woodland herbs such as Asarum canadense, Caulophyllum thalictroides, Trillium grandiflorum, and Uvularia grandiflora can do well in earthworm-rich soils. During a walk with Professor A.R.C. Jones at the Morgan Arboretum in August 1990, I saw these species in rich deciduous woods on calcareous clay soil which had been well cleaned by worms. In many parts of the Arboretum, this clay is overlain by sand -- and at the time of my visit all of these sandy areas had a thick duff layer with no evidence of earthworm activity. It seems that earthworms have a hard time invading coarse, acidic soil.


    Raver is concerned that soils may become alkaline due to earthworm activity. Although some earthworm species do secrete calcium carbonate in their gut, their effect on soil pH is minor at most. This was noted by K.K. Langmaid in Some Effects of Earthworm Invasion in Virgin Podzols (Canadian Journal of Soil Science, Vol. 44, pp. 34-37, 1964). Worms destroyed the classic dark litter-pale Ae-dark B horizon sequence in the studied profiles, turning the whole topsoil dark in every case, but pH changes were minimal.

    Some of Raver's concerns may well be legitimate, as even with steady pH some plants may not be able to survive the change from pre-worm mor or moder to post-invasion mull humus type. Species such as Cypripedium acaule, Epigaea repens and Trillium undulatum, which seem to require thick mycorrhiza-rich litter, may be most vulnerable, along with other woodland species which are unadaptable to garden conditions.


    -Tony
     
  8. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    If European earthworms were destroying American forests, logic would also say that it should be impossible to grow American forest species in cultivation in Europe where the worms are native. This is very definitely not true! Some American forest species are even problem invasive species in parts of Europe where the climate is similar to their homeland.
     
  9. Durgan

    Durgan Contributor 10 Years

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    Interesting article, I have encountered it before. I suggest it needs more work. But introducing new species can be a disaster, one only has to look to NZ and Australia for some horror stories. Probably much worse than in Canada,

    Durgan.
     
  10. angilbas

    angilbas Active Member

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    Here is an eye-opening article by University of Minnesota researchers. And as to my earlier observations...

    ... there may have been plenty of earthworms at Morgan Arboretum, but not Lumbricus rubellus. This species causes far more disruption to understory plant communities than other worms and affects the 'worm-resistant' plants I named in my earlier post.

    L. rubellus may have invaded Toronto's wooded valleys around 1990. When I visited them several times in spring over the 1978-88 period, Trillium grandiflorum could not be missed and the understory was diverse. In E.T Seton Park, I found a community dominated by Asarum canadense, Trillium erectum and Polygonatum pubescens, still thriving in 1988. But all of these species were GONE in May 1991; their replacements were Alliaria petiolata (abundant at woodland edges in 1988 and often dominant in the woods by 1991) and Carex sp. So many understory communities in Toronto had lost their diversity after Alliaria takeover. I don't know if L. rubellus contributed to this upheaval, but after reading the above article I suspect that it did.


    -Tony
     
    Last edited: Mar 29, 2007
  11. hortfreak

    hortfreak Active Member Maple Society

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    Having lived in Toronto and hearing stories from various people, the demise of our native plants in their natural habitats is most likely caused by human beings feeling they have a right to take these plants. After all, they pay taxes, so the plants are theirs. Right? Plant theft in Toronto is rampant and has been for many years, even from private gardens. Edwards Gardens (Toronto Botanical Garden) had mature rhododendrons (and other things) removed in the night (obviously by a landscapers) with the help of large equipment---many times. If someone does that, they certainly won't think twice about taking a mere Trillium from the wild. I could totally bore you with incident after incident of just such cases.
     
  12. angilbas

    angilbas Active Member

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    You have a point, hortfreak. Theft may well explain why there were no understory plants in one of the few earthworm-free areas in Toronto's parks -- an Eastern Hemlock grove on sandy benchland in Seton Park. Beneath the hemlock litter was pale gray sand, part of an eluvial horizon which would have been obliterated by worms. It could be argued that the grove might be too shady, but it didn't look that dim. If there were no thieves one could hope to establish some acid-loving plants.


    -Tony
     
  13. hortfreak

    hortfreak Active Member Maple Society

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    Don't know about acid-loving plants. I lived fairly near Seton Park and had very high pH. However, Toronto is interesting as it has many different faces, including a sand plain. I have friends that garden in almost total sand, whereas I had "concrete".
     
  14. Michael F

    Michael F Paragon of Plants Forums Moderator 10 Years

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    Probably even more important, is human beings feeling they have a right to trample where they like, and to empty their dogs where they like. Both cause significant damage to soil structure, and therefore also to the plants the soil can support.

    Oh, and also spray herbicides where they like, let's not forget that, too.
     
  15. hortfreak

    hortfreak Active Member Maple Society

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    Yes, MY rights shall always take precedence over any others. ME, ME, ME. Only what I want is important. (Sarcastic, of course.) Michael F, you are so right. I often feel sad when I think what our native peoples could teach us and what we fail to learn---respect for the earth and all living beings.
     
  16. Liz

    Liz Well-Known Member 10 Years

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    Ain't that the truth. Quarantine is total dynamite on things brought in. The problem being the cold weather things some times really like our long summer weather :)

    Ragwort comes to mind as an interesting eg of what happens.

    Here it grows 5-6 feet high lots of branches from the roots and masses of pretty yellow flowers. A good northerly (desert wind/summer wind) sends the seed heads miles. The stuff is not good for stock. If you have too much of it and in drought conditions it takes the paddocks over the animals are hungry and eat it and the rest is sick and dead animals as it is I think to alkeline. If I see it on roadsides around here I get out of the car pull it up and place it right in the middle of the road for cars to pound it.

    When I saw it in Europe /England it was this demure little roadside wild flower.

    http://www.dpi.vic.gov.au/dpi/nreni...56BCF000AD54DECC844336D72F0634A256DEA00293F8A
     
    Last edited: Apr 6, 2007

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