Forests on Sand Dunes have been a topic that has come up a
number of threads on the ENTS discussion List. I have
opted to organize links to these threads on this page.
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Bob et al.,
I don't know if this applies to Warren Woods, but sand dunes can
have an hydrological regime favorable for trees. For example, we
found a lakeside sand dune in Mongolia supporting a Siberian
larch
forest. We were looking for a lower treeline forest [where the
forest
meets the grasslands or steppe] which in theory would have trees
more
sensitive to drought. We drove around much of Telmen Nuur [lake]
and
found this dune forest. It was the lowest elevational forest we
could
find for the area. Gordon Jacoby explained to me that dunes
intercept
precipitation and that the precipitation slowly moves down the
dune
and out the bottom and edges. He mentioned that native Americans
in
the west raise corn on dunes to take advantage of this
hydrological
regime. Perhaps a hydrologist could explain the mechanics better
than
I have.
Nonetheless, the larch on this forest were of good size.
Some of the larch were growing very well despite living at low
elevation on a dune in semi-arid Mongolia.
Neil
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| Sand
dune forest |
Edward
Frank |
| Sep
28, 2004 09:40 PDT |
Neil, Bob, and everyone,
Sand dunes, tend to have grains of relatively uniform size, but
small. (Sorted by Aeolian -wind processes) With uniform size of
particles
there is quite a bit of space between the grains. The dune is
very porous.
All of the rain that hits the surface infiltrates immediately.
There
isn't any runoff so nearly 100% of the rainfall is retained. The
water
moves down through the dune itself rapidly, but pools up when it
reaches
the soil or rock layers below. Since it is bound by the grains
making up
the dunes the water can't flow very fast and it can't cut flow
channels. In
general the dune areas tend to be on floodplains, or lake or
seashores with
relatively low topography and many topographically closed
pockets. The
water pools at this interface and is accessible to plants, or
even people
digging shallow "wells" in the lows between the dunes.
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Ed:
This is getting increasingly interesting! If you have a
100-foot dune
with trees growing on it, how far down is it reasonable
to assume tap
roots go?
Bob
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The body of
most dunes are essentially dry aside from any water bound to the
grains by surface tension. So a hundred foot dune with trees
likely has
100 foot + tap roots. I would think there would be a good spread
of the
roots as they tried to catch water as it infiltrated past.
There are a couple of caveats here as well. Are the trees really
growing
on top of the dunes or between them? Are the dunes mobile or
stationary?
Could the tree have slowly been buried over time as the dune
crept over the
area? Would a tree survive being slowly buried and to what
depth? I would
think the trees would grow best in areas between the dunes. Not exactly
in the lowest point as that potentially could be too wet, but
near the
bottom where there is some depth of material over the water
table. I am
just guessing here about the trees, but the hydrology of the
dune is right.
To some degree the water table under a big dune will have a
small hump
that coincides with the hump of the dune, a flattened or subdued
version of
the ground topography. But still in a tall dune, the water table
(likely a
perched water table - it is sitting or pooling on top of the
comparatively
low permeability material below the dune itself) would only be
near the
surface in the areas between the individual dunes.
Ed
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| Re:
Sand dune forest |
greentreedoctor |
| Sep
28, 2004 11:45 PDT |
Ed,
Bob,
Could many of these be "sinker roots" rather than tap
roots? A while back I posted pics of loblollies
and live oaks that where killed due to the changing tides on the
south GA Atlantic coast (Jekyl and St. Simon's Islands). The
live oaks spread like a huge pancake, eventually uprooting,
while the pines remained anchored, showing numerous, deep sinker
roots. Here in the Upstate, I often observe
pine throwdowns with rotted or missing taproots. Maybe
the anaerobic clay contributes to this.
Also, on Long Island, I have observed deep sand fills that, over
a period of time, allow smaller particles (silt?) to collect at
the bottom, and inhibit gas exchange and water infiltration.
Here in the Upstate, I often recommend sand and gravel amending
to facilitate decompation in clay subsoils.
Randy |
| RE:
Sand dune forest |
Neil
Pederson |
| Sep
28, 2004 15:41 PDT |
Ed,
The Siberian larch are on top of the dune at Telmen Nuur. The
dune
seems somewhat mobile, but not so much to slow down the growth
of the
trees sampled too much. As I recall it seems too dry for tree
growth
on either side of the dune. It is too wet near the lake at the
base
of the dune for tree survival. There were younger trees at the
bottom
of the dune, but they were on microsites/dunes - they were above
the
water table and seemed to have fast growth rates.
Neil
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| RE:
Sand dune forest |
Lee
E. Frelich |
| Sep
30, 2004 07:20 PDT |
Neil, Ed, Bob:
The forests in Michigan and Wisconsin on sand dunes are all
rooted in a 1-2
foot thick horizon that has developed as organic matter
accumulates from
plant roots. Tree roots probably also break down some of the
sand into
silt, so that a layer of finer, organic and nutrient rich soil
is formed
and held into place by the forest floor and roots. We
know from gradually
emerging sand bars on Lake Michigan that soils development
capable of
supporting a climax forest of beech, maple and hemlock takes
over a
thousand years. The beech maple forest at Sleeping Bear Dunes
has tall
straight trees that go right over the top of the dunes, while
the first row
of dunes along the lake, which is younger, still has many square
miles of
open sand with occasional stunted groves of trees and patches of
dune grass
and goldenrods.
Warren Woods, Michigan, is not on dunes, it is on flat, deep,
black silt
that looks to me like loess. This forest is several miles from
Lake
Michigan, and is just beyond the sand dune region.
Lee
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Bob:
Have you visited this Hemlock site, when at Zoar Valley?
Any more information that you can add about this site &
trees?
Buffalo News - A fight to save ancient forest
http://www.buffalonews.com/editorial/20050131/1064693.asp
G. Sandy Rose, RCA
Registered Consulting Arborist
Shade Masters, Inc.
Arlington, Texas
[A fight to save ancient forest: County tries to block
owner's plan to build on rare site.
By Tom Buckham and Sandra Tan, News Staff Reporters, Derek
Gee/Buffalo News, 1/31/2005. " Hemlocks are not
supposed to grow on sand dunes. But at least two centuries ago,
a stand of the tall evergreens took root on a high dune
overlooking Lake Erie in the Town of Evans, where it remains one
of only two such old-growth forests on the planet."]
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| RE:
ancient Hemlocks near Lake Erie shore |
Ernie
Ostuno |
| Feb
10, 2005 04:11 PST |
Bob and other ENTS,
The article states that "The only other dune hemlocks in
the world are
in Sleeping Bear Dunes National Lakeshore, on Lake Michigan's
eastern
coastline." Actually, there are several fine examples of
old hemlocks
growing on sand dunes all along Lake Michigan's eastern coast,
both
north and south of Sleeping Bear Dunes. In fact you can see
photos of
them on the ENTS website:
Hoffmaster State Park has some prime examples:
http://www.nativetreesociety.org/fieldtrips/michigan/hoffmaster_state_park.htm
So does Leelanau State Park:
http://www.nativetreesociety.org/galleries/leelanau/lee04.jpg
Muskegon State Park and Saugatuck Dunes State Park also have
some intact
old growth beech/hemlock forest growing on sand dunes.
Elsewhere,
development has fragmented most of the other dune hemlock stands
to
widely scattered remnants.
I am happy to hear that in some places, conservation of rare
ecosystems
may no longer be taking a back seat to increasing the local tax
revenues!
Ernie
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| RE:
ancient Hemlocks near Lake Erie shore |
Robert
Leverett |
| Feb
10, 2005 05:16 PST |
Ernie:
We're with you on being appreciative of the
sensitivities of
communities to protect important rare habitats. I'm also
thrilled to
know that examples of hemlock-dune environments are not limited
to two.
Hemlocks in sand dunes boggles my mind. But come to think of it,
so did
the white pines growing in Nelson Swamp near Syracuse, NY.
Perched on
mounds, talk about looking out of place. Nonetheless, there they
were.
One was dated by Don Leopold to 458 years and that was around 8
or 9
years ago. Adding 8 years + 3 years to the trees base and we can
safely
say that today that white pine is 469 years old.
Bob
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| RE:
ancient Hemlocks near Lake Erie shore |
Lee
E. Frelich |
| Feb
10, 2005 06:18 PST |
Bob et al.:
There are also hemlock-beech forests on sand dunes on the
Wisconsin side of
Lake Michigan at Whitefish Dunes State Park, Newport State Park,
and Point
Beach State Forest.
Lee
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| Questions
for Lee |
Robert
Leverett |
| Feb
10, 2005 07:22 PST |
Lee:
Have these hemlock dunes evolved from sand
moving into more
traditional hemlock territory or hemlocks moving in and
colonizing dunes
or both? Are the dunes very shallow where the hemlocks are
found, such
as at the periphery of the dunes? When a species colonizes or
adapts to
a none conventional habitat, do taxonomists tend to treat the
adaptation
as a subspecies?
It sounds like these lake shore forests are
sum of our most
fascinating plant communities. One final question is what
possible
advantages could a hemlock derive from moving into a dunes area
as
opposed to other species?
Bob
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| Re:
Questions for Lee |
Lee
E. Frelich |
| Feb
10, 2005 07:37 PST |
Bob:
The hemlock clearly invaded the sand dunes. The forests I am
most familiar
with in WI go right over the top of dunes >100 feet tall.
These are old
dunes, on the order of 2000-3000 years. Younger dunes do not
have enough
organic matter in the soil to support a hemlock and beech
forest. Youger
dunes are first colonized by dune grass and other herbs, and
gradually
progress to prairies, then to shrublands, oak and pine
woodlands, and
finally to hemlock, beech and maple.
The sand in these dunes also is composed of fine grains. If it
were coarse
grains like in central WI, then the forest would be jack pine
and pin oak.
In addition, there are no fires to set succession back due to
the fog from
the lake.
There are cases where subspecies, or even full species, develop
over time
on different habitats. The dune goldenrod, Lake Huron Tansy,
Dune
wheatgrass, and Dwarf Lake Iris found along the northern shores
of Lake
Michigan are examples. This is not the case for hemlock--sandy
soils are a
normal habitat for hemlock. Any species benefits from taking
over as much
of the landscape as possible. The only problem hemlock has is
sugar maple.
Those two species are equally well adapted to sandy soils and
have been at
an impasse for 3000 years. See Chapters 6 and 8 of my book for
detailed
explanation.
Lee
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| RE:
Questions for Lee |
Ernie
Ostuno |
| Feb
10, 2005 22:52 PST |
Lee,
Could you give me the title of your book? Sounds like great
reading for
anyone interested in forest dynamics on this side of Lake
Michigan, too.
I was also wondering what the demise of the beech from disease
would
mean for the hemlock/beech forests along Lake Michigan.
Ludington State
Park is currently seeing a massive beech die off from beech bark
disease
which has been accelerated by storm damage in the last few
years.
Ernie
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| RE:
Questions for Lee |
Lee
E. Frelich |
| Feb
11, 2005 07:10 PST |
Ernie:
The reference is:
Frelich, L.E. 2002. Forest dynamics and disturbance regimes.
Cambridge
University Press.
Regarding beech bark disease--it usually leaves a low percentage
of trees
in a stand intact. These trees may be resistant to the disease
and might
allow the species to make a comeback over a period of several
hundred
years. In the meantime sugar maple and, if deer are not a
problem, hemlock
will expand to fill the niche now occupied by beech.
Lee
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| RE:
ancient Hemlocks near Lake Erie shore |
Don
Bragg |
| Feb
11, 2005 06:47 PST |
Although I haven't had a chance to get out and examine them in
detail, I have seen old-growth hemlock stands on steep hills
that I suspect are old dunes along US 2 along the north side of
Lake Michigan, in da UP, eh? The next time I drive this stretch
of highway, I'll try to take a closer look and confirm this...
Don Bragg
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