Is it Possible to have Deep Soils in a Tropical Rainforest Climate?

I've been looking into the topic of rotational grazing lately. I've heard that in temperate climates there is an increase in root mass when managing a herd this way. This contributes to the increase in soil organic matter and essentially increases the depth of topsoil.

One thing I've always heard in ecology is that tropical rainforests have very shallow soils, because the organic matter is rapidly decomposed and converted into plants, leaving an extremely thin topsoil where all the nutrients are suspended in the aboveground vegetation.

How practical is rotational grazing in a tropical rainforest climate? Normally, such climates would not have the ecological feature of open plains and grassland. I'm aware that people graze cattle all throughout rainforest climates. As a matter of fact, it is one of the leading causes of deforestation.

So, what would be the main differences between rotational grazing in temperate climates and in the humid tropics? Is grazing sustainable in tropical rainforest climates? Would you actually increase soil depth or would you just mine the topsoil over time, leading to impoverished land?

Scott, perhaps you have answered your own question.
Why graze in the rainforest if it causes deforestation?

Scott, you ask a good question but I am afraid I don't know how to answer it.  I think part of the answer is knowing just how close the surface of your soil is to bedrock.  If you have say, 4 inches/10cm of total soil sitting above bedrock, I would think that at most you could improve those 4 inches/10 cm, but not actually pile up any more.  I could be wrong on this.  After all, part of carbon farming is the process of drawing carbon from the air and putting it into the soil.  Perhaps it would add a bit of depth to your soil, but in this example, I would be shocked if you could get that 4 inches to 5 inches.

On the other hand, if you have some decent depth of soil--even if of questionable quality--then I would think you could radically improve that soil with your plans.  In any case, your plans should help save what soil is there and prevent its further degradation & further loss.  I would say aim for the best and see how it goes.

Eric

Perhaps someone knows better, the following is all speculation.

I think that in order to create soil, the best option is to always have plants growing. Cattle prefer to eat grass from grasslands, though they might eat low tree branches when available. Ranchers also prefer to manage their cattle in grasslands, it's just easier. So, in tropical rainforest, ranchers would burn a forest, then grow grass from the ashes for their cattle. Then in a few years the topsoil washes away, the grass cannot be grown again and trees have a harder time to establish again. That's, I believe, the major reason for deforestation.

In holistic grazing management, ranchers do not let the cattle eat all the grass, but they move on when 2/3 of the grass has been eaten, thus allowing the plants to recover faster and maintaining soil activity. Is it possible to practice holistic grazing in tropical forests? Well, I'm not sure you can make it if you treat tropical rainforest as a grassland. Decomposition comes with sun, water and heat, and it seems that in this climate trees are a must if you want to maintain fertility. The question then is if you can manage cattle in small forest clearings, sufficient for some grass growing, but small enough that they stay protected from the sun. Maybe there are shrubs and dwarf trees your cattle likes to eat, and you can prune it low so they can eat the leaves and sprouts.

There's also the slow and expensive option of making biochar. Biochar degrades very slowly, so you can accumulate much more organic matter in this form. It works the same as mulch, but with a longer life. The idea with biochar is to apply it in small patches every year, maybe in small forest clearings, before seeding grass.
Add all the unglazed terracotta you can find to the biochar, and you will be creating 'terra preta', the indigenous potsoil of the Amazonia.