Until 2005, around 12 900 ha was mined, and 10 188 ha of that had been afforested. As a result of oil shale opencast mining, the relief is rugged, the soil heterogeneous and extremely stony, nitrogen and organic content of oil-shale mining spoil low .
(2005) found that annual runoff was reduced on average by 44% and 31% when grasslands and shrub lands were afforested, respectively, with eucalyptus reducing runoff by 75% compared with a 40% decrease by pines in afforested grasslands.
In a larger meta-analysis, soil C was about 10% lower following afforestation of pastures with coniferous species; the changes in soil C were not significant when pastures were afforested with broadleaf species (Guo and Gifford 2002).
The afforested soils were grouped into three drainage classes: poorly drained soils with an E (albic) or G horizon (stagnic properties) as the second horizon; moderately drained soils with an apedal horizon as the second horizon, overlying an E (albic) or G horizon (stagnic properties); and freely drained soils with an apedal horizon as the second and third horizon (Table 1).
Some 62 million hectares of plantations, accounting for 31.8 percent of the forest area of China, have been afforested or reforested according to the 2004-2008 National Forest Inventory Report (SFA 2010).