Question

Which statement about the supply of nitrogen and phosphorus in unmanaged ecosystems is incorrect?

1. Most nitrogen and phosphorus for plant growth in unmanaged ecosystems is supplied by decomposition.
2. The decomposition of plant litter and soil organic matter provides essential nutrients.
3. In unmanaged ecosystems, external fertilization is the primary source of nitrogen and phosphorus.

• A. None of these
• B. ii only
• C. All
• D. iii only

Answer 1

Answer:

D. iii only

• Nutrients are lost from ecosystems by leaching, tracegas emission, wind and water erosion, fire, and the removal of materials in harvest.

• Most of the nitrogen and phosphorus required for plant growth in unmanaged ecosystems is supplied by the decomposition of plant litter and soil organic matter.

• Gaseous losses of nitrogen influence the chemical and radiative properties of the atmosphere, causing air pollution and enhancing the green-house effect.

• The combustion of fossil fuels has released large quantities of nitrogen and sulfur oxides to the atmosphere and increased their inputs to eco-systems.