To study soil buffering on plant growth in a region affected by acid deposition downwind of a coal-burning power plant, which experimental setup would be most appropriate?

To study soil buffering on plant growth in a region affected by acid deposition downwind of a coal-burning power plant, which experimental setup would be most appropriate?

• A. Grow plants in identical soil with no buffering
• B. Plant trees in two areas with different sunlight exposures
• C. Measure leaf color of one tree
• D. Measure changes in plant height over a year in two groups of trees the same distance from the power plant; one group is in topsoil and one group is in topsoil with limestone added.

Answer: (D)

When studying how soil buffering affects plant growth under acid deposition, you want to isolate the buffering effect while keeping the acid exposure the same. The best setup compares two groups of trees at the same distance from the power plant to ensure they experience the same level of acidic input. Use identical topsoil for both groups, but add limestone to one soil to increase its buffering capacity and raise the pH. Over a year, tracking changes in plant height provides a clear growth response to the different soil chemistries. If buffering is effective, the trees growing in the limestone-amended soil should show greater height gain because higher pH reduces toxic aluminum and improves nutrient availability, supporting better root and shoot growth. The other options fail to isolate buffering effects or introduce confounding factors, such as varying sunlight, or rely on only a single observation like leaf color, which doesn’t robustly reflect growth under acid stress.

When studying how soil buffering affects plant growth under acid deposition, you want to isolate the buffering effect while keeping the acid exposure the same. The best setup compares two groups of trees at the same distance from the power plant to ensure they experience the same level of acidic input. Use identical topsoil for both groups, but add limestone to one soil to increase its buffering capacity and raise the pH. Over a year, tracking changes in plant height provides a clear growth response to the different soil chemistries. If buffering is effective, the trees growing in the limestone-amended soil should show greater height gain because higher pH reduces toxic aluminum and improves nutrient availability, supporting better root and shoot growth. The other options fail to isolate buffering effects or introduce confounding factors, such as varying sunlight, or rely on only a single observation like leaf color, which doesn’t robustly reflect growth under acid stress.