[Terrapreta] The Science of Terra Preta Formation
David Hirst .com
david at davidhirst.com
Tue Apr 8 11:54:30 CDT 2008
Jim,
It may be that there are a few nutrient recycling opportunities that are
natural, although how far they apply in the Amazon I do not know. For
example;
1. The bodies of Salmon bring nutrients from the sea far up river, and,
after spawning, usually get caught by bears. They tend to take a few bites,
and leave the bulk of carcass in the forest, where the nutrients recycle.
The forests seem to suffer from the loss of salmon. Do any Amazon fish swim
upriver from the sea so brining up nutrients (perhaps via several food
chains)?
2. Aeolian dust. Quote significant volumes of dust get blown about, and
land far from where they originated. In the Amazon, I guess most traces get
lost in the forest but I though Laos was build on blown dust. Some of the
dust is alive, and even scorched islands seem quite quickly to have seeds
land and germinate. Some spiders use threads to fly off and travel long
distances.
3. Volcanoes. They are also a contributor to dust.
4. Sulphur is also cycled from the sea as particulates (and cloud
condensation nuclei). Algae, when they get too hot tend to release DMS,
which helps form clouds (and so cools them).
5. Tectonic movements. Upriver, there are the Andes, which are still
being pushed up, and so can carry on eroding and feeding nutrients
downstream.
Many of these are quite slow acting, but most nutrients get recycled close
to home. I understand that most rain is from evaporation within the forests.
I imagine that forest fires do occasionally occur during dry spells, and
would tend to leave some charcoal.
Most sources seem to think that TP is anthropogenic, and I am not arguing.
But natural sources cannot be entirely ruled out on nutrient cycling
grounds.
Cheers
David
David Hirst
direct: +44 (0) 1723 570113
mobile: +44 (0) 7831 405443
email: david at davidhirst.com
-----Original Message-----
From: terrapreta-bounces at bioenergylists.org
[mailto:terrapreta-bounces at bioenergylists.org] On Behalf Of Jim Joyner
Sent: 08 April 2008 16:02
To: Terrapreta
Subject: Re: [Terrapreta] The Science of Terra Preta Formation
If I might add a few things:
I find it very difficult to believe that dark earth in Amazonia had a
natural start. Much of the muck soils in the US Midwest were due to
catastrophic events through the ice ages. These nutrients became a
treasure trove of nutrients that farmers are still mining. There is
nothing comparable in the tropics that I know of. (Well, there the
occasional guano deposits found, but even these are not soils)
There is practically no way that carbon can naturally accumulate in the
tropics for any length of time. The one exception to that seems to be
charcoal but that is not what we would call natural.
Also, in terms of nutrient (I'm speculating, but bear with me). For
thousands, many hundreds of thousands of years, nutrient has flowed
into the Amazon from the mountains above. Some of these nutrients are
soaked up into above ground jungle/rain forests. Some, of course, are
bound up in aquatic life. Most are washed out to sea. But there is no
source of nutrient in the tropics to "mine" like there are in the
temperate zones. There is no soil deposit to mine simply because, if it
had existed, it would have quickly disappeared.
This means, I think, to have supported what seems to have been huge
populations, there had to be a serious form of economizing and cycling
of nutrient. Basically, people had to take from the rivers and some from
the forests (so far that is gather-hunting which will not support large
populations), but in time as they keep their waste (somehow), they
recycled and accumulated nutrient. This recycling is not unusual (Asians
ahve done for millenia), but it is difficult in the tropics simply
because the medium that is necessary (for the most part) to hold these
nutrients, in a usable way, is carbon. And most carbon under normal
natural conditions in the tropics will will simply evaporate (actually,
the process is burning or oxidation).
Somehow, it seems the people discovered a medium to collect, hold and
recycle nutrients and carbon. Our guess, of course, some form of char.
Jim
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