Four million trees will be planted in Beijing in 2011 as part of efforts to sow the seeds of a greener capital.

"Another 1,100 hectares of land will be turned into green fields," said Wang Sumei, spokeswoman for the Municipal Bureau of Landscape and Forestry, as the nation marked the 30th anniversary of Arbor Day last Saturday.

"The capital's forest coverage will reach 37.6 percent, compared with 35.47 percent in 2005, while 10 more outskirt parks will be opened to the public before the National Day holiday (in October)," she said.

The capital's plan encourages residents to help out in 18 ways, such as planting trees in 30 specially selected suburban locations before the forestation season ends in late April.

Other choices include adopting one of the city's 151 public lawns and woods. The process requires the signing of an agreement that clearly states the time limit (usually one year with an option to renew), the cost and the work that needs to be carried out.

Only 26,000 people chose to adopt a lawn or wood in 2009, although last year that figure soared to 263,000, according to official data.

"Adoption of green areas has become the public's second-favorite choice from the methods to fulfill their responsibilities for forestation," said Wang.

"The top choice has always been planting trees in person."

Ten of the 151 locations up for adoption require both money and management, including keeping them clean and protecting them from damage, while another seven require voluntary care work. The rest involve only donations.

Residents can also adopt old trees, as well as donate cash to green projects and foundations aimed at building up the capital's forestation coverage to offset their personal carbon footprint.

Wang urged more people to buy carbon credits as they are "the most direct way to learn the real ecological value of forests".

2011, which was designated International Year of the Forest by the United Nations in 2006, marks the 30th year since the Chinese government began its nationwide tree-planting movement. In that time, roughly 181 million trees have been planted in Beijing, with a survival rate of 88 percent.