People plant trees in the Xixi National Wetland Park in Hangzhou, East China's Zhejiang province, March 10, 2019. A total of 30 families planted trees at the wetland park on Sunday to greet the upcoming Arbor Day. [Photo/Xinhua]

A child waters a tree in the Xixi National Wetland Park in Hangzhou, East China's Zhejiang province, March 10, 2019. A total of 30 families planted trees at the wetland park on Sunday to greet the upcoming Arbor Day. [Photo/Xinhua]

A child waters a tree with help of her father in the Xixi National Wetland Park in Hangzhou, East China's Zhejiang province, March 10, 2019. A total of 30 families planted trees at the wetland park on Sunday to greet the upcoming Arbor Day. [Photo/Xinhua]

A child tries to plant a tree in the Xixi National Wetland Park in Hangzhou, East China's Zhejiang province, March 10, 2019. A total of 30 families planted trees at the wetland park on Sunday to greet the upcoming Arbor Day. [Photo/Xinhua]

A child ties a card on a tree to record its growth in the Xixi National Wetland Park in Hangzhou, East China's Zhejiang province, March 10, 2019. A total of 30 families planted trees at the wetland park on Sunday to greet the upcoming Arbor Day.  [Photo/Xinhua]