【摘要】 利用原状土连续就地取样(sequentialcoringandin-situexposure)方法研究了澜沧江流域典型退化土壤的氮库营养动态变化过程,监测了矿质氮在时间和空间上的释放与固定、淋失与植物吸收消耗。结果表明人为干扰影响土壤氮矿质化,导致氮固定、淋失,引起养分衰减退化。从阔叶林转变为果园、坡耕地、桉树林和针叶林,矿质氮60d内平均衰减分别为51.51,29.64,26.84,16.40mg·kg-1,变异程度依次为21.5%、11.0%、14.2%、8.3%,氮固定分别为15.45,8.51,13.90,0.00mg·kg-1,淋失量则坡耕地最大,达44.50mg·kg-1,其次是针叶林和桉树林地,分别为38.41和25.30mg·kg-1。植物对土壤氮的吸收消耗为果园>坡耕地作物>桉树林>针叶林>阔叶林,利用形态以硝态氮为主。更多还原

【Abstract】 Both soil disturbance and soil utilization type changes markedly affect rates of soil N mineralization. It is generally impossible to assess the usefulness of most estimates of N mineralization as predictors of field rates because of the unknown effects of assay conditions. A methodology for fluxes of mineral N, based on sequential soil coring and in situ exposure of largely undisturbed soil columns confined within metal tube, to research the soil mineral N’s release and immobilization, plant up take of N and maximum N leaching on degraded soils in Lancang River watersheds, Yunnan. We show that disturbance can either increase net N mineralization, cause leaching of N and immobilization of N, alter the proportion of nitrate nitrogen produced during incubation, or induce or obscure the effects of previous fertilization on rates of N mineralization. The types changed from broadleaved forest to orchard, slop cropland, eucalyptus and pine coniferous forest, mineral N reduced 51 51,29 64,26 84,16 40 mg·kg -1 within 60 days,and the coefficient of variation was 21 5%, 11 0%, 14 2% and 8 3%, respectively. The immobilization of N was 15 45 mg·kg -1 for orchard, 13 90 mg·kg -1 for eucalyptus and 8 51 mg·kg -1 for slop cropland. The maximum N leaching occurred at the type of slop cropland (44 50 mg·kg -1 ), and followed the types of pine coniferous forest (38 41 mg·kg -1 ) and eucalyptus forest (25 30 mg·kg -1 ). The amount of plant up take of N for different types is orchard > slop cropland > eucalyptus forest > pine coniferous forest > broadleaved forest and type of mineral N up taken by plant is mainly as NO 3 N. The results also show that this method causes fewer disturbances to natural process and has no effect on the accumulative N’s type of the process of mineralization. It is the effective method to determine the fluxes of the soil mineral N that under the field conditions.更多还原