Here is an excerpt from Tea From Taiwan's website.
Wu Ling oolong tea (wu-long tea) is our best tea in our regular collection. Wu Ling is a mountain area in Taichung county and its high altitude (more than 2000 meters) contributes to the ideal growing conditions for wu long tea.
Another reason why Wu Ling wu long tea is of such fine quality is the soil of the Wu Ling area. Wu Ling was a fruit producing region for many years until economic conditions favored imported fruit over home-grown apples and pears. Former orchards in the Wu Ling area were converted into oolong tea plantations, and Wu Ling wu long tea is renowned for its fruity quality.
Wu Ling is located on Mount Li (Li Shan or Pear Mountain) and wu long tea from Mount Li is the most prized wu long tea in Taiwan. It is ideally suited for gong fu style brewing and can be re-brewed up to eight times while still retaining plenty of flavor.
More information about the Li Shan area of Taiwan (including a section on Wu Ling wu long tea) can be found on this website about Wu Ling farm.