Previous Year Question
Consider the following statements:
Statement I: The soil in tropical rainforests is rich in nutrients.
Statement II: The high temperature and moisture of tropical rainforests cause dead organic matter in the soil to decompose quickly.
Which one of the following is correct in respect of the above statements?
Both Statement I and Statement II are correct and Statement II is the correct explanation for Statement I
Both Statement I and Statement II are correct and Statement II is not the correct explanation for Statement I
Statement I is correct but Statement II is incorrect
Statement I is incorrect but Statement II is correct
Correct Answer: D
Detailed Solution
Statement I is incorrect. Tropical rainforests possess extremely dense vegetation, but their soils are generally not rich in nutrients. High temperatures and excessive rainfall cause intense weathering of the soil and leaching of nutrients.
Rainwater carries soluble nutrients such as calcium, potassium and magnesium downward from the upper soil layers. This process is known as leaching.
Most nutrients in a rainforest ecosystem are present in living vegetation rather than remaining stored in the soil. Nutrients released through decomposition are quickly absorbed by plant roots.
Statement II is correct. High temperatures and sufficient moisture throughout the year increase the activity of bacteria, fungi and other decomposers. Consequently, fallen leaves and other dead organic matter decompose very rapidly.
Rapid decomposition prevents the development of a thick litter layer on the forest floor. However, this does not make the soil nutrient-rich because rapid biological uptake and leaching of nutrients continue.