Trees? Effectors of geological change? You
bet! Trees cumulatively contribute mightily to the
erosion of land mass.
Consolidated rock is a solid, coherent whole; anything that
plays a part in deconsolidating rocks is a contributor to
erosion. Trees are thieves -- they steal sunlight,
water, and minerals from the plants and soil under their
leaves. We will look at how erosion is aided by trees in
a lawn, and then you'll have to answer logging questions concerning
how trees effect deconsolidation in a more "natural" setting.
In this photo, you see what I call (my words only -- I'm sure
there is a technical term for it) a paucity ring, because outside
of it, organic detritis, minerals and water are abundant, but on
the inside, the roots of the tree are sucking them out of the soil,
and the grass and other plants face a paucity of the things they
need in order to thrive. If a hot, dry spell occurs,
much of the grass inside the ring will perish. Grass and any
other plants act to reduce erosion when it rains or the wind blows;
remove the plants and the rate of erosion increases
dramatically. As you go further towards the trunk of the
tree, to the left in this photo, more and more sunlight is blocked
by the tree's leaves.
If you were blindfolded and barefoot, and walking from the right
side of the photo to the left, your feet would tell you immediately
when you had crossed the paucity ring. The grass is stiffer,
sparse, and there are innumerable pebbles.
Here in the second photo, we're looking from further west of the
tree, towards its trunk, which is about 18" across at chest
level. Immediately above "C" is the paucity ring at the
top of the prior photo. If you had followed the ring from top
to bottom and clockwise in the first photo, the two spots labeled
"B" would also be on the ring. Finally, the line labeled
A-A' consists of 4 yardsticks laid end to end. What you can
see is that there is little grass along and around this 12' length,
What you can't see from the photo is that the white areas
(without any grass) are as much as 2 inches in elevation lower than
those areas that still have grass.
This third photo is scary. It is taken in a location
similar to the previous one -- just two trees over. It is
obvious that any "topsoil" has been eroded away, and all that's
left is a gravelly ground cover. This so-called lawn is
in serious trouble. On a much wider scale, this process is
called "desertification", and for good reason, as the countryside
is on the way to becoming a desert. Here, there is no
danger of becoming a desert, but the area under this tree, and
many, many millions like it in lawns around the country, are losing
their topsoil to erosion, with trees being the
culprit. The only way to avoid this is to apply
generous, constant amounts of water and nutrients (take a look at
Augusta National Golf Course), but Mother Nature usually won't do
that for us.
To add insult to injury, photo four shows a rock, about 5" x
3.25" x 1.25" which has magically been uncovered and eroded out of
the soil in the past three years. It is harder than the
surrounding rocks were, but now is exposed to weathering -- the
boulders you'll be looking at shortly have been revealed by
precisely the same process, just on a larger scale.
So, we've looked at the effect that trees in a lawn have on the
underlying topsoil, but is that true in all lawns, or just the lawn
in which the photos were taken? Also, what about their
effect on a more natural environment? Obviously, under natural
conditions, no one comes along and mows the lawn
regularly. We will now look at two areas at the entrance
to Morrow Mountain State Park. The first will verify or
refute what we inferred from the area in which the photos were
taken, and the second will be "au naturale".
Other Educational Information:
Logging
Questions:
Send me an e-mail – not part of your log
– responding to the following:
1. Make the first line of the e-mail “GC2CR55, The
Deconsolidators: Trees”
2. How many people were in your party?
3. From the parking area, walk across the road to the
opening in the split rail fence, walk thru it, and then take a
right. Walk about 25 yards, and you'll see a 2-3' rock
"emerging" from the ground. Describe the soil in the vicinity
of this rock, with regard to:
a. Vegetation
b. Slope
c. Estimate of depth of
topsoil
4. Walk back across the road to the paved parking
lot, and walk to the first rocky outcrop (do not go to the one
closest to the road -- go about 20' to the SSE (~210º)). The
outcrop looks kind of like a ship's bottom upside
down. Describe the soil in the vicinity of this rocky
outcrop, with regard to:
a. Vegetation
b. Slope
c. Estimate of depth of
topsoil
5. Mental heavy lifting:
a. Here at the outcrop,
try to describe the relationship between the trees, soil and
exposed rock, as it relates to deconsolidation and erosion.
b. Besides the
tree-aided erosion, what other erosion-aiding agents are present
here at the outcrop?
6. Optional: Please post a photo of your party
at the iconic info building at the entrance to the
Park.
Note: For other
EarthCaches in The Deconsolidators, the Gold Hill fault zone and
mining district, and the Uwharrie Mountains series, go
here.
Platinum EarthCache Master