Why a Tropical Rain Forest cannot be replaced very quickly?
A rainforest cannot be replaced as once it is destroyed; it is gone forever (almost thousands of years). We have read above that only the top few inches of rainforest soil have any nutrients. Below that it is deficient in nutrients. There is a high temperature and this high temperature leads to decomposition of the organic material as well as the inorganic parent material of the soil. There are frequent rains and these rains leach the decomposing material off the soil, out of the root zone quickly. So, the result is that the Tropical rain Forests have adapted themselves and quickly take up the nutrients and most nutrients in the tropical rain forests is stored in the vegetation.
When the forest is harvested for timber or other plant products, or the forest is burned, nutrients will be lost from the ecosystem, but the outputs cannot exceed inputs for very long because the stock of nutrient capital in the system will be depleted. When forests are burned, or the cut timber is removed as in logging, the nutrients that were in the tree biomass are either washed out in the case of burning or simply removed from the system.
Because there was only a small stock of nutrients in the soil and most of the nutrients were in the biomass, there is little nutrient stock remaining to support regrowth.
Thus, we can’t simply “regrow” tropical forests once they are burned — once they are lost they are gone forever (or at least for 1000s of years, and even then the species that regrow will be different from the original forest species).