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dominated by white pine and oak, with other trees as well.=C2=A0<
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Hi Randy & All,
I had imagined these dunes to be bare sand. With tree cover on the =
peaks and presumably none on the slacks there is another effect that =
will increase effective ppt in the slacks; sublimation on the tree =
canopy in calm weather and selective snow accumulation in treeless areas =
(roads, glades, etc) in windy weather due to less turbulence and less =
speed over glades..
Yt, DW
----- Original Message -----=20
From: Randy Lauff=20
To: NatureNS=20
Sent: Wednesday, May 21, 2014 9:57 AM
Subject: Re: [NatureNS] slacks - when do they refill?
Thanks folks,
I haven't been there in winter, despite my being in NS now for over 20 =
years.
Here's the landscape picture though. Picture an accordion, partly open =
lying on its back. The bellows represent the dune system at Pomquet, =
there are peaks and troughs (slacks), and precious little other =
elevations going on. At the slack in question, the surrounding peaks of =
the dunes are dominated by white pine and oak, with other trees as well. =
Fred asked, if the dunes are sandy, how are they holding water in the =
first place? Basically, I think there is leaf litter which may be =
accumulating in the slack to slow the water seepage. Further to Anne's =
email, the slack in question is well back from the salt water, I suspect =
there is no salt to speak of in that water. Mosquitoes are there in the =
billions, peepers are deafening, both suggesting fresh water (though I =
realize a few mosquitoes can tolerate brackish water).
Randy
_________________________________
RF Lauff
Way in the boonies of
Antigonish County, NS.
On 20 May 2014 18:24, David & Alison Webster <dwebster@glinx.com> =
wrote:
Hi Randy & All, May 20, 2014
I don't have a clear picture of the topography, either dune or =
inland, but one possible source of water in the slacks is drifting of =
snow into pools.
In woods south of Kentville, where I used to walk in winter, =
pools in woodland cradlehollows of swampy sites never froze. With 2'-3' =
of snow on the ground, the air cone was typically about ~1' across at =
snow level and 4" across at water level. Even at -20o C, with heavy =
snowfall, 60 mph winds and drifting snow there would be no hint of ice. =
From the viewpoint of ppt per unit area these cones act as black holes; =
snow blows into them but, soon being water, can not escape. These air =
cones were absent when snow was not deep enough to act as a good =
insulator. With sufficient snow cover drifted ~level over the swamp, the =
soil at the base of cradlehollows would warm sufficiently by ground heat =
from below to melt overlying snow and eventually generate one of these =
air cones.
If these pools were sufficiently above the water table then they =
would tend to be transient but, in most soils (given sufficient iron and =
decomposable organic matter), infiltration rate at constant head will =
gradually slow due to formation of a local iron pan over decades or =
centuries. This effect interested me because ortstein is sometimes very =
scattered; patches 3-4' wide and 10-15' apart and these pools that =
collect below air cones could account for this. Also prolonged wetting =
will slake any soil aggregates and decrease infiltration rate.=20
Getting back to dunes, in the idealized case of parallel linear =
dunes and linear slacks and in deep snow conditions I would expect =
linear narrow pools at the base of linear narrow trenches in the snow; =
V-shaped deposits of ortstein if dunes are stable and not advancing.=20
Have you been there in winter and if so does any of this =
register ?
Yt, Dave Webster, Kentville=20
----- Original Message -----=20
From: Randy Lauff=20
To: NatureNS=20
Sent: Tuesday, May 20, 2014 4:20 PM
Subject: Re: [NatureNS] slacks - when do they refill?
Thanks Fred, but in a dune system, wouldn't that mean that the =
slacks would be less than half full with water? These are sand =
dunes...very porous, so I'm suspecting water leaching in from the hills =
of the dunes into the slacks just couldn't fill them. This is unlike the =
condition in vernal pools where there can be ample elevation around from =
which water could leach in to the pool area. I'm thinking there has to =
be a significant rain or snow fall to fill them.=20
Randy
_________________________________
RF Lauff
Way in the boonies of
Antigonish County, NS.
On 20 May 2014 15:30, Fred Schueler <bckcdb@istar.ca> wrote:
On 5/20/2014 2:18 PM, Randy Lauff wrote:
Between several of the dunes at Pomquet Beach, Ant. Co., the =
slacks (the
troughs between dune crests) fill with water, but by summer =
are dry. I
guess I've just never been there at the right time to see when =
they fill
again...it can't be just from winter melt water, since the =
slacks are
almost full (and snow melts to about 10% its volume as water). =
Do the
autumn rains fill them again, or the spring rains? Or is it a
case-by-case scenario, which I'd just have to monitor?
* I had the same thought about vernal pools at the CARCNET =
meeting at Quebec City in 1999, during a presentation on Marbled =
Salamanders, which come down into the vernal pools to lay their eggs on =
the dry pondbed in the fall, and stay with them all winter. It turns out =
that the vernal pools fill from the water table, as one would think =
sandy dunes would. And yes, I've been monitoring water level in our =
local Wood Frog ponds, fall and late winter, ever since then.
fred.
------------------------------------------------------------
Frederick W. Schueler & Aleta Karstad
Daily Paintings - http://karstaddailypaintings.blogspot.com/
Vulnerable Watersheds - http://vulnerablewaters.blogspot.ca/
study our books - http://pinicola.ca/books/index.htm
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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