Exotic trees set to spruce up city

Exotic tree species will form the latest line of defense against pollution, according to the city's forestry authorities.

The new varieties, from North America and Europe, will both reduce pollution and beautify the city, said the Forestry Experiment Center of North China from the Chinese Academy of Forestry Monday.

The center has domesticated several tree species, including the blue spruce from North America, and these trees can reduce pollution, absorb dust and still have gold-colored leaves from May through December, according to the Beijing Youth Daily.

The center expects the trees will become a common sight in Beijing's parks and along roads from next year, the report said.

Li Xuan, spokesman from Beijing Municipal Bureau of Landscape and Forestry, told the Global Times that the promotion of a certain tree species should be approved by the bureau first, but the bureau has not received any application for these exotic trees.

Forestry experts believe the city should not rush the introduction of new species as it might pose risks in the future.

"Beijing has some successful cases, such as the US pagoda tree, which can adapt to the climate here," said Zhang Chuanhong, professor with the Research Institute of Forestry at Chinese Academy of Forestry.

It is difficult to introduce exotic trees to Beijing, as the weather here is not moderate, she said.

Sun Zhenyuan, also a professor from the Chinese Academy of Forestry, said that the survival rates of exotic tree species are quite low in Beijing, and warned that many years of experimentation are required before introduction.

"There's a long-term risk in introducing exotic tree species, and researchers must monitor them for up to 10 years before recommending them to the city," Sun noted.

Lots of tree species were introduced purely because of commercial reasons and without the necessary monitoring, which resulted in the death of trees and is a waste of public funds, Sun remarked.

Staghorn sumac, a small tree species introduced in the 1970s from North America, has greatly violated Beijing's ecosystem, as its reproductive period is very short. It has greatly harmed the growth of other plants in farmland, Jiang Gaoming, a professor at the Chinese Academy of Sciences, told the Beijing Youth Daily.

Researchers have still not found a natural enemy for the staghorn sumac, and all the trees must be uprooted by hand, said the report.　

Even if spruces grow well at first, they still may wither under extreme weather conditions, said Sun.

"Research into exotic spruces has just started quiet recently, and [the trees] should not be promoted citywide," Sun noted.