| Woods may affect the physical and chemical characteristics of soil. In order to clarify the influence of artificial ecological forests of different trees on soil physical and chemical properties in Yan'an new district and to provide basis for optimum afforestation, using the abandoned land of Yan’an new area as a control, this research investigated the influence of artificial ecological forest (pines and cypresses) on the physical and chemical characters of soil including water content, pH value, organic matter, ammonium nitrogen and nitrate nitrogen. The results showed that the artificial ecological forest increased the soil water content and the deeper, the higher. pH value of the soil was generally weakly basic. pH value of the pine woods was decreased while this of cypress woods and in the abandoned land varied in different layers of soil. The content of organic matter was reduced with the increase in depth of the layers, which was most in the abandoned land, and fewer in the cypresses woods, and fewest in the pines woods. As for ammonium nitrogen, not many changes in different layers of the wasteland were observed, but in the soil of pines, it became increased with depth between the layers of 0～15 cm and went decreased a little bit in the layer between 15～20 cm. In the soil of cypresses, ammonium nitrogen remained the same in the layer of 0～15 cm, and was decreased in the layer of 10～15 cm but became increased somewhat in the layer of 15～20 cm. The nitrate nitrogen contents varied a lot in different cases, which might result from the types of trees. |