Question

Which one of the following options represents the correct order of decreasing average net primary productivity (g / m2 / year) in natural ecosystems?

• A. Swamp and marshes>Tropical forests>Temperate forests>Temperate grasslands>Tundra
• B. Swamps and marshes>Tropical forests>Temperate forests>Tundra>Temperate grasslands
• C. Tropical forests>Swamps and marshes>Temperate forests>Tundra>Temperate grasslands
• D. Tropical forests>Swamps and marshes>Temperate forests>Temperate grasslands>Tundra

Hint:

Think “\textbf{warm + wet = high NPP}.” Wetlands often exceed tropical forests because constant water and nutrients drive very rapid plant growth.

Answer 1

The Correct Option is A

Step 1: Core idea of NPP.

NPP measures the rate at which plants convert solar energy into biomass after respiration. High water and nutrient availability \(\Rightarrow\) high NPP; cold or dry conditions \(\Rightarrow\) low NPP.

Step 2: Typical relative productivities.

• Swamps & marshes: among the highest (\(\sim 2000{-}2500 \; g\,m^{-2}\,yr^{-1}\))
• Tropical forests: very high (\(\sim 1800{-}2200\))
• Temperate forests: moderate (\(\sim 1000{-}1300\))
• Temperate grasslands: lower (\(\sim 400{-}800\))
• Tundra: lowest (\(\sim 100{-}200\))

Step 3: Arrange in decreasing order.

\[ \text{Swamps \& marshes } > \text{ Tropical forests } > \text{ Temperate forests } > \text{ Temperate grasslands } > \text{ Tundra} \]

This ordering matches Option (A). Other options misplace grasslands or tundra, or invert swamps and tropical forests.

Final Answer: \[ \boxed{\text{(A) Swamps \& marshes > Tropical forests > Temperate forests > Temperate grasslands > Tundra}} \]