<正>为研究杨树长期栽植对土壤微生物造成的影响，对江苏省宿迁市泗洪县陈圩4块杨树林地土壤进行调查。使用常规土壤化学分析手段分析了样品的主要理化性质，分别测定了样品的微生物生物量，并对微生物三大菌群以及与氮元素转化密切相关的几种微生物类群进行了计数。实验结果表明：长期栽植杨树会使林地土壤的pH逐渐升高，栽植杨树14a后林地土壤pH约比对照土壤上升1.5；林地土壤的养分元素氮、磷含量随着林龄增长而降低，而有机质的含量随着林龄增长而增加，但是明显低于对照。土壤微生物中真菌的数量随着栽植时间而逐渐下降，而细菌总数、放线菌总数，以及微生物生物量表现出与土壤有机质含量相一致的变化规律。对参与氮素循环的土壤微生物类群进行计数，发现反硝化细菌的数量随着林龄的增大而明显增加而硝化细菌铵氧化细菌与硝酸细菌的数量则有所下降。

The enzymatic hydrolysis of corn stover under ultrasound was studied. The results showed that the rate of hydrolysis could be enhanced by ultrasound. The effects of ultrasound power, irradiation time, temperature, enzymedosage, and pH were discussed in detail. Under the condition of 20kHz, 30W power and 10min irradiation time, the optimal enzyme dosage was 20IU/g dry substrate. The optimal temperature was 50℃ and the optimal pH was 4.8. The hydrolysis yield reached 27.30% after 48h and was 48.3% higher than that without ultrasound.