不同林龄杨树农田防护林土壤微生物生物量碳、氮和微生物活性

以辽宁省建平县5、10、15和20年生4个林龄的杨树农田防护林为对象，以农田作为对照，研究了农田营造防护林对土壤微生物生物量碳、氮及微生物活性的影响.结果表明：农田营造防护林后，0～15 cm层土壤有机碳、全氮、微生物生物量碳、氮含量和土壤基础呼吸均呈现出先降低后升高的趋势，在造林20年后达到或超过未造林农田的水平；而代谢熵在造林5年后显著增加，然后随着林龄的增加而降低.上述结果表明，农田营造杨树防护林后，土壤微生物生物量和活性均发生了明显的变化.

Soil microbial biomass and activity in relation to stand age of poplar shelterbelts

Taking 5-,10-,15-,and 20 years old poplar(Populus euramericana cv."N 3016")shelterbelts in Jianping County,Liaoning Province as test objects,the effects of establishing shelterbelts on the farmland soil microbial biomass carbon and nitrogen,and microbial activity were evaluated.After the establishment of sheherbelts,the concentrations of organic carbon and total nitrogen,the microbial biomass carbon and nitrogen,and the basal respiration in 0-15 cm soil layer increased after an initial decrease,being reached or exceeded the levels of the control after 20 years afforestation.The metabolic quotient increased significantly after 5 years afforestation,but decreased with increasing stand age.All the results suggested that under the effects of shelterbelt establishment,farmland soil microbial biomass and activity had obvious change.