Impact of three soil types on afforestation in China's Loess Plateau: Growth and survival of six tree species and their effects on soil properties

Soil chemical and physical characteristics can significantly affect the growth and distribution of all types of vegetation, particularly in arid environments. Because of soil erosion, most of the topsoil has disappeared from China's arid Loess Plateau, exposing parent material or soils with low nutrient content in many locations. However, little research has been done on the impact of these soil conditions on afforestation efforts. Conventional afforestation in the area is only thought to be possible on loess soils because the local foresters consider the two other main soil types (red clay and bedrock-derived soils) too barren to support trees. In an attempt to determine whether these soils could also support afforestation, we planted trees on all three soil types in a hilly area of the Loess Plateau near Yan’an City. The results indicate that large-scale afforestation in loess soils could potentially increase the severity of soil water shortages, degrade the natural environment, and increase the risks of desertification and of serious economic losses because of over-consumption of soil moisture. However, survival rates on red clay and bedrock-derived soils were generally comparable to those on loess for individual species, and were superior to those on loess in mixed-species plantations, with less of an adverse impact on soil water. Both red clay and bedrock-derived soils could thus potentially sustain afforestation in low-lying areas with adequate soil moisture.