Assertion (A): Unlike temperate forests, the tropical rain forests, if cleared, can yield productive farm-land that can support intensive agriculture for several years even without chemical fertilizers. Reason (R): The primary productivity of the tropical rain forest is very high when compared to that of the temperature forests.

The correct answer is D because Assertion A is false while Reason R is true. Assertion A is false because tropical rain forest soils are actually very poor in nutrients. Most of the nutrients in these ecosystems are stored in the living vegetation rather than the soil. Due to high temperatures and heavy rainfall, organic matter decomposes rapidly and nutrients are quickly leached away. Once the forest is cleared, the soil loses its nutrient source and becomes unproductive for agriculture within a very short period without heavy fertilization. Reason R is true because tropical rain forests have the highest primary productivity of any terrestrial ecosystem. The constant high temperature, abundant moisture, and year round growing season allow for rapid biomass production, far exceeding that of temperate forests. However, this high productivity does not translate into fertile soil, as the nutrients are recycled almost immediately back into the trees.