Zeng Limin is a forester at Saihanba National Forest Park in northern Hebei Province, which is the largest man-made forest in the world. However, foresters still want to expand Saihanba's green coverage, and Zeng is now in charge of this challenging project – planting trees on the sunny slopes of small mountains that are mostly rock.  

Saihanba is in an alpine region at an altitude ranging from 1,000 to 2,000 meters. The park contains wetlands, lakes, woods, and mountains. With some mountains having very little soil, it is particularly difficult for many trees to grow on the slopes. A notable exception, however, is the Mongolian scotch pine.

Spring and autumn are the busiest times of year for Zeng. Spring is the only season where foresters are able to plant Mongolian scotch pines seedlings on the mountainside. Because of the steep slopes, Zeng and his co-workers are only able to bring the seedlings up to the mountains by themselves or by mule. And in autumn, the work is tougher, because they need to break huge rocks and dig holes in them. This is to create space for new seedlings to grow in during the following spring.

Zeng has been working in Saihanba for 21 years, and has spent most of his time in the woods with the trees. In his spare time, Zeng always goes to the mountains to see these Mongolian scotch pines that are flourishing on the sunny slopes. He says he can't stop worrying about them, especially when the seedlings are moved from nurseries to the mountains. Zeng also needs to weed often, otherwise the tall grass would block the sun, which may prevent the seedlings from growing. He also said the trees are just like his children, and nothing makes him happier than seeing them grow up healthily.