"The blossoming of flowers is influenced by the temperature, so it's uncertain. Sometimes you miss the period and have to wait for another year," says Liu.

It takes him a long time to complete shooting one plant, since he tries to record different parts－flowers, fruits, leaves and stems, which he usually cannot see at one time.

"I may capture the flowers of a plant in spring, and in autumn I remember to go there for its fruits. I just go in different seasons, shoot whatever I can find, and remember to complete the other photos next time," says Liu.

Similar to photographing birds, he says he pays more attention to plants that are often seen in the mountains instead of special types, because "all plants matter".

"It's really interesting, and I find it more appealing as time passes by. Every time you go out and find different plants, you can search the information or consult others for their identities. That's a really good experience. Sometimes when I see pictures of plants unknown to me taken by other people in the local areas, on my WeChat, I cannot help but try to find them by myself, too," says Liu.

He says he tries not to disturb the birds or plants, just works as a "recorder" instead of interfering with their lives.

"I never lure birds with food to take pictures. I wait for their appearance. Whatever they look like in nature, I just record them," says Liu.