If a tropical rain forest is removed, it does not regenerate quickly as compared to a tropical deciduous forest. This is because

The correct answer is ​the soil of rain forest is deficient in nutrients.

• The soil of rain forest is deficient in nutrients:
  • Rainforest = Rainfall through the year. It rains almost every day = The topsoil is continuously washed away = nutrients are also washed away = leaching of nutrients = very little fertility remains in topsoil = most of the seeds don’t germinate for years = regeneration is very slow (it takes decades).
  • But the layer below the topsoil (sub-soil) is very fertile.
  • So plants grow very quickly once their roots reach the sub-soil and if they receive enough sunlight.

Additional Information

• Propagules of the trees in a rain forest have poor viability:
  • Propagule = detachable structure that can give rise to a new plant, e.g. a bud, sucker, or spore [Asexual Reproduction in plants].
  • Seed bearing plants are more significant than Propagules in the rainforest. So propagules don’t really matter.
• The rain forest species are slow-growing:
  • The plant species in rainforests compete for sunlight.
  • So they grow as rapidly as they can.
• Exotic species invade the fertile soil of rain forests:
  • This statement is wrong as the rainforest soil is heavily leached. Hence they are not fertile.
  • But exotic invasive species are a threat to rain forests (E.g. Most plantation crops like rubber, palm, etc.).