树木定植可以影响土壤理化性质。为明确延安新区不同树种人工生态林对土壤理化性质的影响状况，为合理造林提供依据，以延安新区荒地土壤为对照，研究了人工生态林（松树、柏树）对土壤理化性质，包括含水量、pH值、有机质、铵态氮和硝态氮含量的影响。结果表明：人工林增加了土壤含水量，且随着土壤深度的增加，土壤含水量变化总体呈现出增加的趋势。土壤的pH值总体上是呈弱碱性，松树定植土壤pH值呈现降低趋势，柏树和荒地土壤pH值在不同土层中变化较大。土壤有机质的含量随深度增加呈递减的趋势，不同土层中呈现荒地＞柏树＞松树。荒地土壤铵态氮在不同土层中变化不大，柏树土壤中0～15 cm随深度的增加而增加，15～20 cm略有下降；松树土壤在0～10 cm土层基本相同，10～15 cm有所下降，15～20 cm略微上升。硝态氮在不同类型利用方式下变化不一，造成这种差异可能与树种有关。%Woods may affect the physical and chemical characteristics of soil .In order to clarify the influence of ar-tificial 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 wa-ter content ,pH value ,organic matter ,ammonium nitrogen and nitrate nitrogen .The results showed that the artificial e-cological forest increased the soil water content and the deeper ,the higher .pH value of the soil was generally weakly ba-sic .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 be-tween 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 be-came 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 .
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