What makes the soil in tropical rainforests so rich?

Rainforest - Wikipedia

Abundant rainforests, useless soils – DW – 08/23/2019

What is the difference between temperate and tropical soils? - Quora

How dark is it at the rainforest floor? - Quora

Tropical Soils: Less is More in Fast Carbon Pathways, but Only

Tropical rainforests are viewed as rich in biomass productivity

Tropical Rainforest Reptiles List With Pictures & Facts For Kids

Abundant rainforests, useless soils – DW – 08/23/2019

Features and Human uses of a tropical rainforest

What type of soil do rainforests have? - Quora

How is the Rainforest's soil? - Quora

Why is the tropical rainforest soil poor and thin? - Quora