[tbw2]

Terra preta (Portuguese pronunciation: [ˈtɛʁɐ ˈpɾetɐ], locally [ˈtɛhɐ ˈpɾetɐ], literally "black earth" or "black land" in Portuguese) is a type of very dark, fertile anthropogenic soil found in the Amazon Basin. Around 10% of the Amazon has that soil, created I believe from burning the trees but integrating the charcoal into the ground so that it absorbs much more water and retains more nutrients. You don't get pockets of uber-fertile man-made soil throughout an area without settlement. I wouldn't be surprised if most of what we see as rain forest was farmed like the Maya and Aztec homelands, but returned more quickly after the Spanish brought the pandemics.

[SunkenCiv]

http://www.freerepublic.com/tag/terrapreta/index