The ancient trees of Populus euphratica and Populus pruinosa refer to individuals whose tree age is estimated to be more than 100 years. Method for estimating the age of ancient trees: The age of trees with diameter at breast height below 70 cm is mainly based on actual measurement, and the age of trees with diameter at breast height above 70 cm is calculated based on the average annual growth. Combined with the actual measurement, the average annual growth for the diameter at breast height of 70~100 cm is estimated to be 0.3 cm, the average annual growth of the diameter above 100 cm is 0.25 cm, and the average annual growth of the diameter above 200 cm is 0.22 cm. The specific calculation method is, estimate tree age = diameter at breast height ÷ 2 ÷ average annual growth.

At present, a total of 129 ancient trees of Populus euphratica and Populus pruinosa have been collected, including 118 ancient trees of Populus euphratica (including 23 ancient tree groups and 95 ancient tree individual trees), and 11 ancient trees of Populus pruinosa (8 ancient tree groups and 3 ancient tree individual trees).

The ancient Populus euphratica are distributed in Aksu region, Bayingoleng Mongolian Autonomous Prefecture, Hoton region, Hami City, Kashgar region, Tacheng region, Boertala Mongolian Autonomous Prefecture, Karamay City, Changji Hui Autonomous Prefecture, Turpan City, a total of 10 prefectures (states, cities) in 28 counties (cities, districts). The ancient Populus euphratica germplasm resources are distributed in the range of longitude 76°38′3.10″ ~ 88°9′45.60″, latitude 36°49′79.70″ ~ 42°15′30.50″, and altitude 869m~1459m in southern Xinjiang, it is distributed in the range of longitude 82°59′27.54″~95°13′50.10″, latitude 42°12′58.20″~46°54′46.60″, and altitude 211m~1010m in northern Xinjiang.

The ancient Populus pruinosa are distributed in 3 prefectures (states, cities) 9 counties (cities and districts) of Aksu region, Kashgar region and Hotan regions of southern Xinjiang. The ancient Populus pruinosa germplasm resources are only distributed in southern Xinjiang, distributed in the range of longitude 76°28′44.60″~83°29′, latitude 36°49′79.70″~41°39′ 21.70″, and altitude 936m~1455m.

Among the ancient tree resources of Populus euphratica (including Populus pruinosa) in Xinjiang, ancient trees estimated to be over 500 years old, 300 to 399 years, 200 to 299 years, and 100 to 199 years old accounted for 2.32%, 17.82%, 44.96% and 34.88% of the total ancient tree resources, respectively.

The age of Populus euphratica (including Populus pruinosa) for ancient tree resources in the Aksu region, Bayingoleng Mongolian Autonomous Prefecture, Hotan region, Kashgar region, Hami and Tacheng regions showed diversity, while the resources of ancient trees in other regions (states, cities) only appeared in a single age group. According to the classification standard of ancient trees (define an estimate of tree age over 500 years are defined as class-I ancient trees, the range 300 - 499 years are defined as class-II ancient trees, and the range 100 - 299 years are defined as class-III ancient trees), Hotan and Aksu regions have class-I ancient trees, but the proportion is relatively low; Kashgar, Bayingoleng Mongolian Autonomous Prefecture, Hami City and Tacheng Region have class- II and class-III ancient trees, and there are mainly class-III ancient trees; Boertala Mongolian Autonomous Prefecture, Changji Hui Autonomous Prefecture, Turpan City and Karamay City all have class-III ancient trees.