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

Answer: (d) A is false but R is true

Productivity is high (R true), but the nutrients sit in the plants. Cleared, the soil is poor within a few years (A false).

The idea

Keep two words apart. Productivity is how fast plants grow, and in a rainforest it is very high. Soil fertility is how many nutrients the soil holds, and in a rainforest it is very low. The forest grows fast in spite of its soil, because it recycles every nutrient.

Forest is cut and burnt → Ash gives a burst of nutrients → Crops do well for two or three years → Rain washes the nutrients away → Yields collapse; the farmer moves on

Why the others are wrong

(a) Accepts A — reading high productivity as fertile soil.

(b) Accepts A as true.

(c) Rejects R — but rainforest productivity really is the highest on land.

The trap

High productivity sounds like it must mean fertile soil. The fertility is in the biomass, not the ground.

Also know

This is why shifting cultivation moves from plot to plot, and why cattle ranches cut from the Amazon forest often turn to poor pasture within years.