system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can rain forests have infertile soil yet such huge growth?

I've seen many documentaries that talk about rain forests having infertile soil. When they cut them down to grow soya beans, etc the problem becomes that the soil doesn't have enough nutrients.  

So how can rain forests have such infertile soil yet have the biggest plants and trees in the greatest of volume of plants and trees in the first place?   

I'm quite perplexed! Looking forward to your answers!
gpt
Because the trees pull up the nutrients as rapidly as they're deposited, there is no buildup of nutrients in the soil. The nutrient layer is very much in the surface, there's very little underneath. The trees are living on recycled nutrients of all the trees around them. The same matter goes around and around the cycle. Trees take in the nutrients, grow, make leaves, drop leaves, die, compost down in the top layer of soil, and the sequence repeats. If you have a crop which involves taking nutrients AWAY in trucks to be sold in towns, then there is a NET LOSS of nutrients. They have left the cycle.