[Aztlan] Questions about vegetation on Mesoamerican ruins

[David Hixson]

Jules Seigel brought up some very interesting
questions that are at the heart of archaeological
remote sensing studies.  If there is a correlation
between certain vegetation and mounded architecture,
multispectral or hyperspectral remote sensing would be
the avenue to locate and analyze such signatures.

Unfortunately, the correlation is not so clear-cut. 
As I found in my early studies of NW Yucatan, and Tom
Sever (helping Bill Saturno) found a few years later
in Guatemala, there ARE some differences between
vegetation growing on the "natural" surface and that
growing on the "anthropogenic" surface of mounded
architecture.  However, the difference between the two
is often qualitative rather than discrete.  By this I
mean that mounded architecture does not always have
different species of plants growing on their slopes
and peaks, but rather more or less healthy specimens.

[Side note - it has been suggested that certain
species of trees, specifically Ramon, were planted in
ancient Maya sites, therefore are more common in
archaeological ruins]

In my studies of NW Yucatan, using satellite remote
sensing, pedestrian surveys and test excavations, I
found that the mounds themselves are "soil traps". 
Following a previous study by Tim Beach (1998), I
found that in the dry and rocky soils of NW Yucatan,
the richest A/0 horizons are located ON the mounds
themselves.  This means that lowland (off-mound) soils
are highly leached and are much more likely to have
high clay and iron contents, whereas those soils on
the slopes and peaks of pyramidal architecture are
more likely to have high organic components.

This is due to three major factors -- one is that the
mounds themselves are well-drained (much like putting
rocks at the bottom of your potted plants to make sure
they are not drowned by watering); Second, the highly
soluble limestone of NW Yucatan is itself a medium for
promoting A/O horizons, as the limestone (and stucco)
decays and provides a different chemical composition
to the soil than the surrounding terrain; and third,
the decaying debris of an ancient city will often add
nutrients to the soil, giving the soils "on-site" a
more rich composition than those "off-site".

Finally, I must address Jules' question about sea
shells.  If sea shells are found at the top of a
pyramid, the only explanation is human or animal
agency (i.e., a human or animal dropped it there,
during construction, during its use, or long
thereafter).

I have certainly found crabs 15 kms from the coast
(pushed up through the underground aquifer) and I have
seen birds flying overhead with both fish and
shellfish in their talons over archaeological sites.

But I promise that the sea was never high enough
during the Holocene to allow seashells to naturally
"wash up" on the top of a pyramid (I have conducted
digital reconstructions of the Yucatan coast during
Holocene high sea stands, and this would simply be
impossible).

-Dave


> What is the tallest structure entirely covered in
> vegetation growing on 
> it (as opposed to around it forming a canopy)?
> 
> How did the vegetation get there?
> 
> What kind of vegetation is typically found?
> 
> How deep are the roots?
> 
> The depth of the soil?
> 
> Is it true that seashells have been found in the
> soil on top of 
> Mesoamerican monuments? If so, how did they get
> there? What kind? Age?


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