The tropical rainforest is a complex ecosystem with a high level of biodiversity. When a tropical rainforest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. This is primarily due to the fact that the soil of the rainforest is deficient in nutrients. The high rainfall in these areas washes away the nutrients from the soil, making it less fertile. The other options, such as poor viability of propagules, slow-growing species, and invasion by exotic species, may also contribute to the slow regeneration, but the primary reason is the nutrient-deficient soil.