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Dear All, Dec 31, 2014
I agree to some extent with all comments made about Frog Pond. Yes =
with Nick that 'invasions' frequently reflect an inbalance of some kind. =
Yes with Dusan that dog do and ducks could readily account for =
occasional coliform peaks. And yes with Fred that a truly "invasive" =
species should readily be able to invade "undisturbed" habitats (and =
therefore we have few to no invasive plants). And also yes, the presence =
of Cabomba
caroliniana in the pond demonstrates that somehow a propagule got there =
and perhaps nothing else.
[ From the biogeographic viewpoint, ponds and river drainage systems =
are islands in a sea of land. The presence of an aquatic species =
demonstrates that it can survive there but absence may demonstrate only =
that, by bad luck, it has yet to be 'introduced' by some vector. =
Consequently one native aquatic species may fill a pond with growth, if =
by chance other competition has not arrived, and thereby seem to be =
invasive which in a sense it is. Some aquatics are widespread; of 19 =
Potamogeton species known in California by 1963 (Munz & Keck), 15 are =
also present in Nova Scotia. ]
To see what Frog Pond was like I Google-earthed it. It looks like a =
sump, fed by runoff from housing on two sides and with little or no =
outflow drainage. Someone in Halifax must have a conductivity meter and =
the means to calibrate it with standard KCl. I don't know how old those =
developments are but if >10 years I would expect abnormally high =
conductivity/salinity. But Cabomba caroliniana apparently does not =
tolerate high salinity (in one US study it was not found in salinity > =
0.5 ppt (the limit between fresh & brackish). If there is no outflow =
then the'problem' may be solved by runoff and evaporation.=20
As for control, I think it helps to step back and consider the =
broader picture. Against the backdrop of climate change and habitat =
degradation, to name just two of many serious problems, the potential =
spread of Cabomba caroliniana has an automatic score of zero on my =
concern index. And if it does grow vigorously here then it might indeed =
be useful for capture of excessive nutrients; e.g. phosphorus. =
[Pointless programs to eradicate invasives, usually mine canaries, just =
deflect attention and resources from the underlying causes.]
There was concern this summer about dense stands of vascular =
aquatics in some lake near Halifax (Lake William ?) and talk of a =
$100,000 mowing machine. So some practical experience in vascular plant =
harvesting may be long overdue. Vascular aquatics have arenchyma so will =
float when cut off, so it should not be difficult to devise affordable =
means to harvest aquatics in a diversity of settings.
=20
Yt, Dave Webster, Kentville
=20
=20
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<HTML><HEAD>
<META content=3D"text/html; charset=3Diso-8859-1" =
http-equiv=3DContent-Type>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23588">
<STYLE></STYLE>
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<BODY>
<DIV>Dear All, =20
Dec 31, 2014</DIV>
<DIV> I agree to some extent with all comments made=20
about Frog Pond. Yes with Nick that 'invasions' frequently reflect =
an=20
inbalance of some kind. Yes with Dusan that dog do and ducks could =
readily=20
account for occasional coliform peaks. And yes with Fred that a truly =
"invasive"=20
species should readily be able to invade "undisturbed" habitats (and =
therefore=20
we have few to no invasive plants). And also yes, the presence of=20
<EM>Cabomba<BR> caroliniana</EM> in the pond demonstrates that =
somehow a=20
propagule got there and perhaps nothing else.</DIV>
<DIV> </DIV>
<DIV>[ From the biogeographic viewpoint, ponds and =
river=20
drainage systems are islands in a sea of land. The presence of an =
aquatic=20
species demonstrates that it can survive there but absence may =
demonstrate only=20
that, by bad luck, it has yet to be 'introduced' by some vector.=20
Consequently one native aquatic species may fill a pond with growth, if =
by=20
chance other competition has not arrived, and thereby seem to be =
invasive which=20
in a sense it is. Some aquatics are widespread; of 19 Potamogeton =
species known=20
in California by 1963 (Munz & Keck), 15 are also present in =
Nova=20
Scotia. ]</DIV>
<DIV> </DIV>
<DIV> To see what Frog Pond was like I Google-earthed =
it. It=20
looks like a sump, fed by runoff from housing on two sides =
and with=20
little or no outflow drainage. Someone in Halifax must have a =
conductivity meter=20
and the means to calibrate it with standard KCl. I don't know how old =
those=20
developments are but if >10 years I would expect abnormally high=20
conductivity/salinity. But=20
<EM>Cabomba caroliniana </EM>apparently does not tolerate=20
high salinity (in one US study it was not found in =
salinity >=20
0.5 ppt (the limit between fresh & brackish). If there is no outflow =
then=20
the'problem' may be solved by runoff and evaporation. </DIV>
<DIV> </DIV>
<DIV> As for control, I think it helps to step back =
and=20
consider the broader picture. Against the backdrop of climate change and =
habitat=20
degradation, to name just two of many serious problems, the potential =
spread of=20
<EM>Cabomba caroliniana </EM>has an automatic score of zero on =
my=20
concern index. And if it does grow vigorously here then it might indeed =
be=20
useful for capture of excessive nutrients; e.g. phosphorus. [Pointless =
programs=20
to eradicate invasives, usually mine canaries, just =
deflect=20
attention and resources from the underlying causes.]</DIV>
<DIV> </DIV>
<DIV> There was concern this summer about dense stands =
of=20
vascular aquatics in some lake near Halifax (Lake William ?) and talk of =
a=20
$100,000 mowing machine. So some practical experience in vascular plant=20
harvesting may be long overdue. Vascular aquatics have arenchyma so will =
float=20
when cut off, so it should not be difficult to devise affordable means =
to=20
harvest aquatics in a diversity of settings.</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> Yt, Dave Webster, Kentville</DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV>
<DIV> </DIV></BODY></HTML>
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