Which of the following was a result of the Hubbard Brook watershed deforestation experiment?
a. Most minerals were not recycled within the intact forest ecosystem
b. Calcium levels remained high in the soil of deforested areas
c. Deforestation decreased water runoff
d. The nitrate concentration in waters draining the deforested area became dangerously high

Verified step by step guidance

1. Understand the context of the Hubbard Brook watershed deforestation experiment, which was designed to study the effects of deforestation on ecosystem nutrient cycles and water runoff.
2. Recall that deforestation can lead to increased water runoff because trees and vegetation that normally absorb water are removed, leading to more water flowing into streams and rivers.
3. Consider the role of trees and vegetation in nutrient cycling. In an intact forest, trees absorb nutrients from the soil, and these nutrients are recycled back into the ecosystem through processes like leaf litter decomposition.
4. Recognize that without trees, nutrients such as nitrates are not absorbed and recycled effectively, leading to higher concentrations of these nutrients in water draining from the deforested area.
5. Conclude that the correct result of the Hubbard Brook experiment is that the nitrate concentration in waters draining the deforested area became dangerously high, which corresponds to option (D).

Key Concepts

Nutrient Cycling in Ecosystems

Nutrient cycling refers to the movement and exchange of organic and inorganic matter back into the production of living matter. In intact forest ecosystems, nutrients like nitrogen and calcium are recycled efficiently, maintaining soil fertility and ecosystem stability. Disruption, such as deforestation, can interrupt these cycles, leading to nutrient loss and environmental imbalance.

Impact of Deforestation on Soil and Water

Deforestation significantly affects soil and water dynamics by removing vegetation that stabilizes soil and regulates water flow. Without trees, soil erosion increases, and water runoff can carry away essential nutrients, leading to elevated concentrations of substances like nitrates in nearby water bodies, which can be harmful to aquatic life and water quality.

Nitrate Pollution

Nitrate pollution occurs when excess nitrates, often from agricultural runoff or deforestation, enter water systems, leading to eutrophication. This process can cause algal blooms, deplete oxygen levels, and harm aquatic ecosystems. In the Hubbard Brook experiment, deforestation led to increased nitrate levels in water, highlighting the importance of vegetation in nutrient retention.