BEIJING, May 8 (Xinhuanet) -- Landscaping a city takes more than just putting trees into holes. These are living creatures that constantly demand attention. Erik Nilsson and Wu Wencong talk to the tree doctors who keep Beijing green and lush.
Zhang Yinshan never killed anyone when he was a military fighter pilot, but now he exterminates pests with the greatest determination.
The 50-year-old has regularly flown air strikes to poison and starve invaders en masse since he became a helicopter operator for the Beijing municipal bureau of landscape and forestry's air protection section.
His foe is the American white moth, an alien species that has been chewing its way through swaths of trees in the capital and across the country.
About 40 times a month, two pilots fly small choppers five meters above the treetops at about 80 kilometers an hour outside the Fifth Ring Road to deliver a payload of diflubenzuron.
"The chemical makes it impossible for the larvae to metamorphose and forces them to eventually starve," section chief Xue Yang explains.
"It kills the bugs (but) is harmless to the environment."
Because the helicopters are small, cramped and somewhat wobbly in flight, every "sortie" requires very specific conditions, Xue says. There must be no wind, no rain and no air traffic, and the temperature must be lower than 28 degrees C.
The practice began in 1984 but changed dramatically after 1996. During the first period, cargo planes dropped 800 kg of chemicals on an average of 53 hectares during a three-hour flight. Now, the helicopters take about 15 minutes to drop 200 kg of diflubenzuron on an average of 33 hectares a mission.
"The use of helicopters to protect trees is rare in other countries," Xue says. But it's just one of many ways that China's - and in particular, its capital's - tree management is unique.
Beijing's government has taken many measures to green the gray over the years, from planting the "Great Green Wall" - a tree belt muzzling the Gobi Desert's sandy jaws from swallowing the city - to successfully encouraging rooftop gardens on public buildings.
One dimension has been the preservation of tree species that would likely otherwise be extinct, says Fu Dezhi, former head of the Beijing Botanical Garden and editor of the book, A Collection of Hand-painted Endangered Plants in China.
"Usually, the biological features of endangered tree species are too specialized to enable them to be grown in cities," Fu says.
"But a few species that can hardly be found in the wild are preserved in cities because of historical cultivation."
This is true of the dawn redwood and gingko in Beijing.
"Some researchers say the dawn redwood has been preserved only because people used to make coffins out of its wood," Fu explains.
The tree is often referred to as a "living fossil" in China.
While the dawn redwood creates a "sluggish" feel on autumn streets, the gingko - the leaves of which can be harvested for traditional Chinese remedies - is an ideal "street tree", Fu says.
"The gingko is beloved by people all over the world because its leaves turn such a radiant gold in fall. The species is more than 100 million years old but virtually absent in the wild," he says.
But this tree, another living fossil, is common in the city's temples. And Beijing Scene's website reports the local government is planting 46 million gingkoes to replace the poplars and willows - species prevalent today because of their expedience at New China's birth.
"Willows and poplars grow large quickly, and are excellent for producing shade," Beijing Institute of Landscape Science engineer Che Shaochen says.
"They were among just a handful of species the government could choose from in the 1950s, when it started its emergency campaign to increase Beijing's forest coverage. Now, there are hundreds of varieties to choose from, and authorities have stopped planting female willows and poplars."
Willows and poplars have fallen out of favor mainly because they shed huge amounts of fluff from their catkins in spring, which carpets the city in a pervasive blanket. (See story on page 4.)
The capital's forest coverage was only 3.2 percent when New China was founded in 1949, when most trees were located near temples, according to the Ministry of Forestry. The municipal government prioritized rapid forestation, which has increased to 37 percent currently, while its overall vegetation coverage occupies 53 percent of the city.
"With more varieties to choose from, authorities aren't just looking to plant tall trees but also to create vertical tiers of trees and plants," Che says.
Fu says city planners select species which effectively green areas and provide shade. Then, they consider whether they are aesthetically pleasing. And if they shed irksome seeds or fruit, they're out of the drawing.
Most of Beijing's flora not only don't scatter undesired extras but also absorb pollution.
The "typical urban tree" in Beijing stores about 36 kg of carbon dioxide (CO2), while "ancient trees" store an average of 453 kg, a 2007 Chinese Journal of Eco-culture study found.
However, it also calculated that in 2002, trees trapped about 4,600 tons of CO2. Older trees stored less than 1 percent of the total while healthy trees sucked in about 90 percent.
More than 40,000 "ancient trees" - those at least 100 years old by official record - are registered in the capital, but about 20 percent are already "in declining health", the landscape and forestry bureau's wildlife protection department head Yang Zhihua says. About 15 percent are older than 300 years.
On the opposite end of the spectrum is fast-growing and highly renewable bamboo.
"Bamboos help protect the soil against erosion and keep their leaves throughout the winter, providing green touches to the city in the cold season," International Network for Bamboo and Rattan director general Coosje Hoogendoorn says.
"Then, a little later than other plants, they replace their (spring) leaves with fresh green ones. Bamboo stems can form a green screen and give a unique experience (of) walking through a cathedral-like grove of bending, waving bamboo stems."
Fu believes that while greenery can enhance a city's ecology, this idea shouldn't be taken too far.
"It's important that we don't try to create a forestlike environment in the city," he says.
"Cities are environments we have created to cater to human needs. And real forests are not suitable for us to live in. So, the trees in cities are like the people in them - they need to be carefully managed."
(Source: China Daily)
