Near rivers and “contains large amounts of nitrogen, potassium, and phosphorus.…”
I bet the same could be said about the soil below heron rookeries.
In North America there used to be huge amounts of guano fertilizer under miles-long groves of passenger pigeon nesting trees.
But when that was used up the passenger pigeons were extinct so it hadn’t been replaced.
In these villages there would be lots of organic material brought in from open areas to thatch the big communal house and all the other buildings every so many years. Plus human waste, peeled bark, cordage making, food processing, etc.
Piasa; makes sense!
"In these villages there would be lots of organic material brought in from open areas to thatch the big communal house and all the other buildings every so many years." And every few years the building was replaced and the old building became firewood and flooring or just fell down and turned back into soil. If along a riverbank, they fished, and what did they do to the fins, heads, and tails (if they were not making soup that day!) Remember Tisquanto using fish fertilizer! (Biochar, fish byproduct, kitchen waste, and human waste in a riverside settlement.)
Lençóis Maranhenses, MA, Brasil. In Brazil, but not, I think, an amazonian indiginous tribal product. Makes the point, though, about generational concentrations of organic matter from indigenous Amazonian building materials.