不同林龄和连栽代次杨树人工林土壤氮矿质化特性

采用好气培养间歇淋洗的方法,研究了江苏苏北地区不同林龄(1代4年生林地、1代10年生林地)和连栽代次(1代4年生林地、2代4年生林地)的杨树人工林土壤及农田无林地土壤在20和30℃培养条件下氮素矿质化特性.结果表明,各样地土壤经4周培养的矿化量为36.70～95.63 mg·kg~(-1),平均矿化速率约为1.31～3.42 mg·kg~(-1)·d~(-1).林龄和连栽代次对杨树人工土壤的矿质化作用有明显的影响,其中主要是对硝化作用的影响,而对氨化作用影响不明显.与1代4年生林地相比,1代10年生林地土壤矿化累积量和硝化累积量分别降低了11%～17%和13%～20%;而2代4年生林地土壤则分别降低了39%～43%和45%～49%,显示连栽代次对土壤矿质化作用的影响更加明显.各样地土壤矿化速率和硝化速率在培养的第1周最高,然后随培养周期迅速降低;而氨化速率则是在第2周达到峰值,然后逐渐降低.随林龄和连栽代次的增加,土壤矿化速率和硝化减小,尤其是培养第1周,而氨化速率差异不显著.各样地30℃培养条件下的土壤矿化量和矿化速率均明显高于20℃,表明培养温度对土壤矿质化作用具有明显的影响.

Characteristics of soil nitrogen mineralization in different aged stands and the successive rotation stands of poplar plantation

By the aerobic incubation-intermittent leaching method (20and 30 ℃) ,the characteristics of soil nitrogen mineralization in different aged poplar plantation stands (the first rotation of four-year-old and ten-year-old) ,the different successive rotation poplar plantation stands (the first rotation of four-year-old and the second rotation of four-year-old) and the agricultural land were studied in Chen-wei Forest Farm,Sihong County,Jiangsu.The results showed that the cumulative mineralized N of soils from the four studied sites ranged from 36.70 t0 95.63 mg · kg~(-1) during 4 weeks incubation and the average mineralization rate of soils approximately ranged from 1.31 t0 3.42 mg · kg~(-1) · d~(-1).The stand ages and successive rotations had great effects on soil N mineralization (mainly on nitrification).Compared with the first rotation stands of 4-year-old poplar plantation,the cumulative mineralized N and nitrified N decreased by 11% ～17qo and by 13% ～20% ,respectively in the first rotation stands of 10-year-old poplar plantation,while in the second rotation stands of 4-year-old poplar plantation it decreased by 3g% ～43% and by 45% ～49% respectively.Soil mineralization rate and nitrification rate were the greatest in the first week and then sharply decreased in the following incubation weeks for all sites while the peak value of ammonification rate occurred in the second incubation week.Soil min-eralization rate and nitrification rate decreased with the increase of stand ages and successive rotations,but the stand ages and successive rotations had no obvious effect on ammonification rate.For all stud-ied sites,the cumulative mineralized N and mineralization rate were significantly greater at the incuba-tion temperature of 30℃ than at the temperature of 20℃ ,indicating that incubation temperature had a great influence on soil mineralization.