Step 1: Understanding the Question:
This question tests knowledge of yield regulation methods.
Step 2: Detailed Explanation:
The Swiss method of yield regulation in irregular forests is calculated on the basis of increment.
It uses the periodic increment to determine the allowable cut.
Growing stock (A): Used in some methods.
Height and increment (C): Not used in Swiss method.
Diameter class (D): Not used.
Thus, the correct answer is increment.
Step 3: Final Answer:
Thus, the Swiss method is based on increment, which corresponds to option (B).
[0.5cm]