Soil salinization and ecological remediation by planting trees in China

With world population growth, the demand for food, vegetable and so on is increasing. However, arable land area cannot expand. Moreover it would decrease owing to land use change with socio-economic development. Especially in China that is the most populated country in the world, while its cultivated land area could not match with the population, farmland is gradually declining with urbanization progress. In order to meet the demand to grain production and alleviate the pressure on current arable land, wasteland must be reclaimed. Forestation is not only one way for saline-alkali soil utilization, but also can improve soil property and maintain ecological balance. Salt-affected soils extensively distribute on the earth. Although the causes are various for salinization occurrence, generally spoken it results from the accumulation of free salts to an extent that causes degradation of vegetation and soils. On the other hand, irrational human practices have increased soil salinity by changing the natural balance of the water cycle in the landscape by allowing excess recharging of groundwater. This reduces suitability to plant growth and increases the potential for other forms of land degradation such as soil erosion and structural decline. Thus salinization is one of the most serious long-term threats to the sustainability of land and water resources in the world. Trees can tolerant a certain level of salinity thanks of the nature. Therefore in the viewpoint of biological amelioration of salt-affected soil, planting trees is necessary and significant. After trees are established in saline land, the watertable could be declined through increasing discharge and decreasing recharge. Additionally total salt content could be decreased, especially in soil surface profile and topsoil as well as soil physical & chemical state could be ameliorated.