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4. Although I do everything I can to keep my dog healthy, it's still possible that her feces might contain parasites or diseases that could be transmitted to other people's dogs or even, in some cases, to humans and other animals. Even aside from the potential effects on wildlife and the environment, as a responsible pet owner I should not take unnecessary
Hi Fred & All, Apr 22, 2011
Perhaps in some areas, where PET (potential evapotranspiration) is
nearly as large as PPT (precipitation), logging may account for a
significant fraction of nutrient depletion. But in the humid east, where
half or more of precipitation is available for leaching, I suspect that
leaching of nutrients from the rooting zone may lead to serious depletion of
mobile nutrients such as N, Ca, Mg, S and in coarse soils even P. Deep
percolation losses occur every year and over a 100 year or so logging cycle
may even exceed loss due to wood extraction.
This applies especially to coarse soils, giving rise to the folk yarns
about farms so poor that rabbits have to pack a lunch before crossing or
rabbits heartbroken and crying at the sight of such poor land. But shallow
soils or mostly organic soil profiles that have been burned, both entirely
unsuitable for farming, may be even more depleted.
I can hear the wheels grinding to the effect that if leaching
impoverishes forest soils then surely the soluble components of doggie-do
would also be quickly leached from the soil. There is a major difference
because leaching loss takes place from the lower limit of root activity
whereas nutrients applied to the surface have to pass through the root zone
which is also the zone of relatively intense biological activity (The
decrease in biological activity in moist soil from the top of mineral soil
downward is roughly logarithmic).
Having been retired for 16 years my memory of such details is
increasingly like a freedom of information document (mostly blacked out) and
to refresh the screen I ordered a book today (Principles of Terrestrial
Ecosystem Ecology, 2002, Chapin, Matson & Mooney) so I may revisit this
question later.
Some 20-30 years ago sugar maple stands in Ontario and Quebec had a tree
decline problem-- gradual loss of branches and sap output culminating in
loss of trees. A multi-year survey was undertaken and a draft report of
results was sent out for review. I suggested in my review (based on my
interpretation of Waldsterben) that leaching of nutrients by acid rain from
leaves that were damaged and made permeable by ozone, could be a major cause
and suggested establishment of fertilizer trials to test this. The editor
(Rennie I think) was quite enthusiastic about this idea, intended to pursue
this with the research team for possible future research and said he would
send me a copy of the final report (all based on memory so some details may
be smuged). Some months later I received a letter to the effect that the
editor had died suddenly of a heart attack, preparation of the final report
would be delayed but I would receive the promised complementary copy in due
time. That was the last I heard of this study but I remain curious to know
whether or not the impact of leachng from foliage, on forest tree decline,
has been investigated.
Absorption and transport of nutrients has a considerable metabolic cost,
especially for elements like P and K that are poorly mobile in soil such
that absorption requires root growth (or mycorrhizal growth) into fresh
soil. And if leaching from leaves is excessive, relative to normal, such
that this cost is 2-3 times normal then some other component such as
carbohydrate reserves, growth etc may be expected to suffer.
Getting back to dogs one should keep in mind that very intensive usage
would be required to have much of an impact on e.g. tree vigor and possible
more diverse effects are of more interest to me, e.g. insects (beetles,
flies, butterflies/moths), Splachnum...
The typical manure application on arable land would be roughly as 1"
lumps spaced about 1" apart (or if you wish, 10 tons/acre or 2 g/cm^2). A
20-year manure study in the Netherlands indicated that, with an initial
state of moderate fertility, annual application for about 100 years would be
required to reach a new elevated steady state. This would be equivalent to
really intensive dog usage.
Yt, Dave Webster, Kentville
----- Original Message -----
From: "Frederick W. Schueler" <bckcdb@istar.ca>
To: <naturens@chebucto.ns.ca>
Sent: Tuesday, April 19, 2011 12:14 PM
Subject: Re: [NatureNS] Dogs on walks
> On 4/19/2011 10:28 AM, Flora Johnson wrote:
>> Much as I'd love to think that my dog is doing the wilderness a favor by
>> defecating there, sadly this does not appear to be the case.
>
> * as above, encouraging nutrient supplementation is only appropriate in
> habitats that have been degraded by anthropogenic removal of nutrients
> (by logging, fishing, etc.).
>
> fred schueler
> ------------------------------------------------------------
>
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