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?
(a) Both Statement I and Statement II are correct and Statement II is the correct explanation for Statement I
(b) Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I
(c) Statement I is correct but Statement II is incorrect
(d) Statement I is incorrect but Statement II is correct
14. Ans: d
Explanation:
It is a misconception that tropical soils are rich in nutrients. Initially, soil in its untouched state contains a thick mantle of Humus, making the soil fairly fertile due to the heavy leaf fall and decomposition of leaves by bacteria. But once the humus is used and natural vegetative cover is removed, the torrential downpours in these tropical rainforests soon wash out most of the soil nutrients. Thus, the soil deteriorates rapidly with subsequent soil erosion and soil impoverishment.
Hence, statement 1 is incorrect.
Factors effecting decomposition
Organic matter decomposition is influenced by climatic conditions such as high temperature, sun exposure, soil moisture, aeration and soil type. Warm, humid climates have faster decomposition rates, while cool, dry climates have slower rates.
Temperature:
Decomposition rates increase with higher temperatures because microbial activity is generally more rapid in warmer conditions. Decomposing organisms are less active at colder temperatures, resulting in a low rate of decomposition. This is why food is kept in a fridge. As temperatures, increase, soil microorganisms become more active, leading to faster litter turnover and less organic matter accumulation.
Moisture:
Adequate moisture is necessary for microbial activity. Extremely dry or waterlogged conditions microorganisms’ activity can reduce and decomposition can be hindered. Moisture is crucial in decomposition, as it aids microbial activity and the breakdown of organic matter. Microorganisms, like bacteria and fungi, require water for metabolic processes and to transport nutrients within decomposing materials. Dry conditions can hinder microbial activity, as microorganisms require specific water levels. Maintaining a balanced moisture level is essential for optimizing decomposition processes, ensuring efficient nutrient cycling and soil fertility.
Soil temperature and moisture content are crucial factors affecting decomposition rates. Warmer temperatures and high moisture levels result in higher rates of decomposition, faster litter turnover, and less organic matter accumulation
The high temperature and moisture of tropical rainforests cause dead organic matter in the soil to decompose more quickly than in other climates, thus releasing and losing its nutrients rapidly.
Hence, statement 2 is correct.
Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2023