"Planting a tree on the barren, rocky mountain is way more difficult than on the plain," said Sun Zhanliang, deputy head of the Yuquan Mountain forest park.

It first created a slope on the mountain, installed timber planks along the slope, dug holes for tree planting and laid out an irrigation network. Company employees then carried earth, fertilizer and saplings up the slope for planting.

Because of the shape of the mountain, large machines could not be used and most of the work was done manually.