The members of the Standing Committee of the Political Bureau of the Communist Party of China Central Committee, including Li Keqiang, Zhang Dejiang, Yu Zhengsheng, Liu Yunshan, Wang Qishan and Zhang Gaoli, also participated in the event.
"It's necessary we further mobilize the public with more creative methods and continuously carry on the voluntary tree-planting activity," Xi said.
The report to the 18th National Congress of the Communist Party of China in November emphasized the importance of ecological progress and advocated the building of a "beautiful China" in the country's development plan.
Last year the afforestation area nationwide was 6.01 million hectares, according to the State Forestry Administration.
Beijing has also been undertaking ambitious reforestation initiatives.
Over the past 32 years, 78 million people have planted 189 million trees throughout the capital, with a survival rate of 88 percent, said the Beijing Municipal Bureau of Landscape and Forestry.
The capital has also been increasing the varieties of trees planted to further improve their survival rate and biological diversity.
According to the bureau, the forest coverage rate rose from 12.83 percent in 1980 to 38.6 percent by the end of 2012. The green coverage rate in urban areas rose from 20.08 percent to 46.2 percent in the same period.
However, despite the achievements of the past few decades, Xi said China is still an ecologically vulnerable country and has a long way to go to improve its environment.
Forests play an indispensable role for the Earth and its residents, and all of society should continuously strengthen its ecological awareness and make the country more environmentally friendly, he said.
"It is hard to imagine how the Earth and human beings would look without forests," he said.
