According to China's regulations, trees with a general age of 100 years or more are ancient trees; Ancient trees are divided into national first, second and third grades.

Pinus tabulaeformis with DBH over 70cm and tree age over 500 years is classified as a first-class ancient tree.

Pinus tabulaeformis with DBH over 40 cm and age of 300-499 years is classified as a second-class ancient tree.

Age 100-299, classified as a third-class ancient tree.

DBH of Pinus tabulaeformis is not only related to age, but also related to site conditions and climate environment. The DBH age at 40 cm of Pinus tabulaeformis is about 250 ~ 350 years old.

DBH: Also called trunk diameter, it refers to the DBH of the tree trunk from the ground surface. When the cross section is abnormal, measure the average of the maximum value and the minimum value. Different trees have different DBH, and different countries have different regulations on DBH. In China and most countries, the breast height is set at1.3m above the ground.