Where in China is the chuandou structural system most common?

The chuandou structural system is currently most common in the southwestern region of China.1

Unlike the more standardized tailiang system, chuandou utilizes tall, thin columns that extend from the roof purlins to the ground along the full length of the gable end, with horizontal tie beams penetrating these columns. It is possible that this method was once standard throughout much of China before the Han dynasty, eventually retreating to the southwest due to the depletion of tall timber in the north and the adoption of the timber-saving bracketing system.1