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Question

Difficulty: MediumStrengthen

Forestry researcher: In high-elevation pine forests, stands treated with mechanical thinning showed a significantly lower rate of bark beetle infestations over a three-year observation period than adjacent untreated stands. Because thinning increases the spacing between trees, thereby increasing sunlight penetration and reducing tree competition for soil moisture, the researcher concluded that reduced water stress directly enhanced the trees' physiological capacity to produce defensive resin against beetles.

Statement: The finding that elevated wind speeds in thinned forest stands physically disperse and dilute the aggregation pheromones used by bark beetles to coordinate mass attacks strengthens the forestry researcher's conclusion.

Answer: Answer

Answer

False
The statement is false because the supplementary finding acts as a weakener rather than a strengthener. In causal arguments, introducing an alternative mechanism (wind disrupting beetle communication) that fully explains the observed effect (lower infestation rates) undermines the author's specific conclusion that the effect was produced by enhanced resin defenses resulting from reduced water stress.

Step-by-Step Solution

1
Identify the premises and conclusion of the argument.
Premise: Thinned stands had lower beetle infestation rates and reduced tree competition for water. Conclusion: Reduced water stress directly enhanced the trees' physiological capacity to produce defensive resin against beetles.
To evaluate whether supplementary evidence strengthens an argument, one must isolate the author's exact causal mechanism rather than just the general outcome.
2
Analyze the logical impact of the supplementary finding on the posited causal relationship.
The supplementary finding demonstrates that higher wind speeds in thinned stands disrupt beetle pheromones, which directly reduces beetle attacks without involving tree resin or water stress.
Determining whether new information supports or undermines the specific link between the stated cause (resin from reduced water stress) and effect (fewer infestations).
3
Determine whether introducing an alternative causal pathway strengthens the argument.
Introducing a competing, independent cause for the observed correlation weakens the author's claim that resin defense was the active cause.
An alternative explanation for the observed correlation undermines the author's proposed causal mechanism, making the statement that it strengthens the conclusion false.

Key Concept

Causal Strengthening and Alternative Explanations in Logical Reasoning
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