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Hi Fred & All, Nov 17, 2010
Thanks for your comments. It has taken a while, but at last I have set
aside a few minutes to reply in part.
I had not intended to include Quebec or Ontario in 'Eastern Canada'
because, in this subject matter, I believe only what I have been able to
observe directly and my time has been spent mostly in NS.
"Wild spaces" in cities, often little more than unofficial garbage
disposal sites, are no doubt frequently vulnerable to being taken over by
unusually tough plants and this will usually mean non-native plants. Human
settlement tends to de-water landscapes and this effect reaches a maximum in
many cities. Former relatively stable stream flows, and relatively stable
soil moisture regimes on ravine sides and flood plains, are replaced by a
feast or famine water regime; flash flood or sopping wet during rain events
and parched a few days later. The soil on ravine sides is often a mixture of
construction waste, appliances, surplus fill, plastic sheeting, etc.; a
challenge for even tough plants. So when "wild spaces" in cities are invaded
by aliens it may be germane to consider why this happens.
Buckthorn (Rhamnus frangula) has begun in recent decades to spread
rapidly here, after spending about 250 years doing nothing and this touches
on the question of why plants "become invasive". In this case, it may be
related to changes in land use.
Until about 1960 it was common practice here to pasture cattle in
woodland, especially cut areas, near rural settlements until the hay of
meadows had been cut. As agriculture shifted from most farmers having a few
cattle to few farmers having many cattle, that practice was abandoned and
Buckthorn was protected from the lethal effects of grazing.
In 2006 I checked a nearby site for possible control of Buckthorn aby
cattle as described in the following paste.
START OF PASTE
Dear All, Sept 24, 2006
Further to my comments of Sept 21 (below) I visited this stand today [by
walking East of Kentville, to examine the bushes near the fence that is
just north of the rail trail]. Cattle have been pastured on the north
side of this fence since at least 1960 but I don't recall ever having
seen horses in this pasture.
Briefly, Hawthorn (_Crataegus_)and Common Buckthorn (_Rhamnus
cathartica_) were browsed about equally, just back to the wire or a
tongue length beyond, and these shrubs were relatively common near the
fence, as compared to abundance at distance from the fence.
In contrast, Alder-leaved Buckthorn (_Rhamnus frangula_) was browsed well
back from the fence, if anything more than Chokecherry (_Prunus
virginiana_) and was relatively infrequent near the fence.
It would appear, unless horses have been pastured here in recent years,
that Alder-leaved Buckthorn is a favourite treat of cattle and therefore
easily kept in check by cattle.
Yours truly, Dave Webster, Kentville
EXCERPT FROM SEPT 21 POST\\\\\\\\\\\\
If it did come to NS with the Acadians then some factor must have
held it in check until recently, and livestock teeth, the bane of young
woody plants is the obvious suspect. [I just remembered a stand of
Buckthorn that probably extends to a pasture fence. Will check it one of
these days for a possible browse line.]
END OF EXCERPT\\\\\\\\\\\\\
END OF PASTE
Norway Maple is a common ornamental here and spreads readily in town
provided it is not mowed. I have never seen it in woodland and doubt that it
would persist in a closed canopy here past 50 years or so of age because,
even in a narrow hedge, it seems to become long and lanky in search of
light. I would be interested to hear how it behaves elsewhere.
My subliminal impression of alien herbaceous plants is that they support
a wealth of insect life and insect life supports other life forms---
One example that found me by accident is Mustard White, a putatively
uncommon beast that would likely have become very rare if it had been denied
the opportunity to exploit a non-native crucifer; Cardamine pratensis. Where
C. pratensis is present in eastern Kings Co., Mustard White is frequently
abundant. A cut and paste from a 2004 e-mail (also partly a cut & paste)
will avoid repetition: at least at the typing end.
After having seen this unknown white butterfly many times near the
entrance to my woodlot over several years, curiosity took over and I rigged
up an insect net from muslin and a kitchen strainer hoop: son-of-a-gun;
Mustard White.
START OF PASTE
Hi Randy & All, Oct 28, 2004
The effects of adding many weedy species of herbaceous plants, for
example, might, if considered objectively, be found on balance to be
positive.
I'd love to read an example of this. And by "positive", do you mean,
"positive to people"?
Hi Randy & All, Nov 1, 2004
As explained in my e-mail of May 16, 2004 (excerpt pasted below), I
think Mustard White (Pieris napi) would now be less common in NS if it had
failed to adapt to introduced plants. So these introduced plants have
probably had positive effects from the standpoint of insect diversity and
for the welfare of the species in question.
START OF PASTE
Of the various known food plants listed in Opler & Malikul (1992;
Peterson Eastern Butterflies), Morris (1980; Butterflies and moths of
Newfoundland and Labrador), Ferguson (1954) and Scott (1986; as listed
by C. Majka e-mail of 18-May-2003) all are either cultivated,
introduced, adventive, rare or with a restricted distribution.
For example--
1) Toothwort (Cardamine <--Dentaria diphylla); Never found south of
Digby/Canso line, with a restricted habitat (rich moist soil) and now
probably less common due to grazing and tillage.
2) Watercress (Rorippa nasturtium-aquaticum)<--(Nasturtium officinale);
Escape from cultivation. Probably the food plant for the ca. 1864
Halifax area population. Also, in 1864, lepidopterists were likely more
abundant in the Halifax area than elsewhere. And those cold water
runnels of the Halifax area with watercress have long since been
converted to sewer routes.
3) Rock Cress (Arabis spp.); Rare and north of the Digby/Canso line.
4) Cardamine pratensis var. palustris; Scattered in central Cape Breton.
4a) Cardamine pratensis; Introduced. Not reported as a food plant but,
based on the var. palustris being used, expected and the North Alton
colony confirms this.
5) Rorippa palustris <-- islandica; Partly adventive and not commonly
encountered.
6) Hedge-mustard (Sisymbrium spp.); Two introduced species.
END OF PASTE
END OF PASTE
Yt, Dave Webster, Kentville
----- Original Message -----
From: "Frederick W. Schueler" <bckcdb@istar.ca>
To: <naturens@chebucto.ns.ca>
Sent: Sunday, October 31, 2010 10:49 PM
Subject: Re: [NatureNS]Invasive aliens: was re unauthorized vs. OK plants
lists
> David & Alison Webster wrote:
>
>> Executive summary:
>> I can not think of one non-native plant that has caused a serious
>> problem in Eastern Canada. Some, for a few years, may locally overwhelm
>> native plants. But sometimes native plants overwhelm other native plants.
>
> * there's a lot of good points here, but I think the questions relevant
> to the executive summary are "how far west does eastern Canada extend,"
> and "what constitutes a problem."
>
> If Toronto is allowed to be part of "eastern Canada," then between
> European Phragmites, Norway Maple, Goutweed, Dog-strangling vine,
> Flowering Rush, Pink Jewelweed, Buckthorns, Narrowleaf Cattail, Garlic
> Mustard, and a host of other alien plants, there's not much doubt that
> even forests and other "natural" habitats have had their native species
> considerably diluted, and one can't say how much truer this would be if
> Purple Loosestrife and Saint Johnswort hadn't been knocked out by
> biological controls. I described the alienness of the Toronto area in
> http://groups.google.com/group/naturelist/msg/661b4fcb53862d34?hl=en.
>
> When I commented to Bev Wigney this summer about the relatively native
> vegetation in Nova Scotia, she promptly reminded me of a lot of alien
> species that were all over the place, but that weren't on my Ontario
> alarm list (her homesite is equally divided among two alien species of
> Cherries and Black Locust, with wide patches of Goutweed, Dame's Rocket
> in the woods, and Celandine scarce only because she'd been pulling it
> all summer)
> http://karstaddailypaintings.blogspot.com/2010/09/old-black-locust.html#more
>
> There's three kinds of problem that alien plants can cause, first is the
> direct squeezing out of native species of plants by competition. The
> second is the redirection of the photosynthate they produce into their
> own growth and away from Insect herbivores, and direct attributes of the
> native species that might otherwise feed or benefit native animals.
>
> The third is more abstract: the dilution of the biogeographic integrity
> of the biota. If one accepts maintaining as much as possible of the
> biogeographic differences among places as a proper goal of People who
> live on the Earth, then the dilution of native species is an absolute
> harm that's done by all alien species, including ourselves, against
> which any human action that may introduce new species must be balanced.
> But of course biogeographic integrity is not a widely endorsed as a
> motivation, and its maintenance is derided as an overt motivation even
> by some invasive species biologists.
>
> The thing about invasive species is that they're such magnificent Plants
> that struggling against them in an open-minded way teaches the clear
> lesson of the importance of loving your enemies.
>
> fred schueler.
> ============================================================
>
>> The longer version:
>> Labels tend to cloud rather than clarify matters, as I will discuss
>> later. First though one should get the history correct.
>>
>> Based on Gray' s Manual (7 th ed; 1908), Purple loosestrife (as
>> Lythrum salicaria and as L. salicaria var. tomentosum) must have landed
>> in North America way before 1900. By the time this 7 th ed. was compiled
>> and printed, typical PL was present in N.E., Del. & D.C. and var
>> tomentosum was present from e. Que to Vt and in s. Ont. Much of these
>> range descriptions were likely based on pre-1900 collections.
>>
>> Someone who has access to earlier editions of Gray's manuals and/or
>> Harvard/Yale herbaria catalogues will be able to establish a more
>> precise date but I would guess well before 1800 and perhaps partly or
>> entirely as ornamentals.
>>
>> The 7th ed. says L. salicaria is 'local'. In the 8th ed. (1950) this
>> is expanded to 'locally abundant, often too aggressive in choking out
>> native vegetation.' .
>>
>> LABELS: Labels are fine if in, e.g. ecology, if they are used to
>> characterize some set of responses to some defined set of
>> conditions. The label "Old Field Spruce" e.g. has been used to refer to
>> the forest cover that initially replaces the mostly herbaceous ground
>> cover of abandoned farmland; the older trees being predominantly Spruce
>> (favoured by exposed mineral soil) and the later arrivals being
>> predominantly Fir (favoured by litter).
>>
>> I suppose from the viewpoint of these displaced
>> shade-intolerant herbaceous plants, these Spruce could be considered
>> "Invasive" but more objectively they are just players in a process of
>> secondary succession.
>>
>> And secondary succession never sleeps. Shortly after crustose
>> lichens establish borders they are swamped by foliose lichens that
>> prosper at the edges and decline in the middle. And comparable processes
>> of encroachment, prosperity at the fringes with stagnation in the
>> interior can be seen in the vegetation of barrens, bogs and even in
>> woodland (esp at the level of air photographs).
>>
>> But labels, such as "Invasive Alien" that are assigned on the basis
>> of prejudice or labels that have emotional overtones can obstruct clear
>> thought and consequently belong more in the realms of politics or
>> propaganda than in natural history or biology.
>>
>> In many and perhaps all cases the question is not "Why did this
>> plant become invasive ?" but "Why did it become fashionable to call this
>> plant invasive ?" Or even "Why did it become fashionable to call alien
>> plants that do unusually well here invasive ?"
>>
>> Was it to drum up support for field research ? [It is unfortunately
>> likely true that a research proposal to avert some crisis is more likely
>> to be funded than a proposal to just study the natural world. If there
>> is no crisis in sight then it will be expedient to invent some.
>> Surviving cultures are those that adopt the trappings that facilitate
>> survival.]
>>
>> Or was it to solicit contributions to save... whatever fits...; our
>> native pristine wetlands...the Acadian Forest... or at least cover the
>> cost of collecting the contributions ?
>>
>> Proceeding now from the general to the particular, if we are to
>> " ordinarily rule against importation of any non-native species. " I
>> guess this means we should, while there is still time before these
>> non-native species become vicious, wipe out the Sable Island Ponies and
>> of course outlaw most agricultural crops and livestock ( e.g. horses,
>> cattle, sheep, goats, asparagus, potatoes, oats, barley , wheat, beets,
>> carrots, tomatoes, apple, pear, ....and rabbits; especially rabbits)
>> and, to be on the safe side, we should bring back non-selective
>> herbicides and wipe out the mostly non-native vegetation of lawns,
>> ornamental shrubs and flower gardens.
>>
>> And if we are going to "ordinarily rule against importation of any
>> non-native species", and bearing in mind that native species are already
>> here and thus do not need to be imported, I guess this means that we
>> should close the border to all trade involving plants (or animals by
>> extension).
>>
>> Hopefully those non-native plants that travel by wind, water, flesh
>> or fowl will do the right thing and bail out before they cross the
>> border.
>>
>> But on the other hand, perhaps those very aggressive invasive
>> species will be inconsiderate enough to cross the border anyway. In fact
>> that might be a practical working definition of this class. Therefore,
>> on this basis, all plants should be on the white list.
>>
>> Yt, Dave Webster, Kentville
>>
>
>
> --
> ------------------------------------------------------------
> Frederick W. Schueler & Aleta Karstad
> Bishops Mills Natural History Centre - http://pinicola.ca/bmnhc.htm
> Thirty Years Later Expedition -
> http://fragileinheritance.org/projects/thirty/thirtyintro.htm
> Longterm ecological monitoring - http://fragileinheritance.org/
> Daily Paintings - http://karstaddailypaintings.blogspot.com/
> http://www.doingnaturalhistory.com/
> http://quietcuratorialtime.blogspot.com/
> RR#2 Bishops Mills, Ontario, Canada K0G 1T0
> on the Smiths Falls Limestone Plain 44* 52'N 75* 42'W
> (613)258-3107 <bckcdb at istar.ca> http://pinicola.ca/
> ------------------------------------------------------------
> ------------------------------------------------------------
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