Changes in soil internal N cycle and trace gas fluxes under elevated nutrient input

尽管预测热带地区的氮沉降将大幅增加，但其对热带森林的影响在很大程度上仍然是描述性的。在拟议的项目中，我们计划继续进行N2 O、NO、CH 4和CO2的土壤-大气通量测量（NUMEX实验）。我们的早期研究结果表明，在通量测量的第一年后，微生物过程硝化和反硝化已经发生了重大变化。此外，有迹象表明，N循环速率增加的地块，以中等速度接收N除了。我们计划进行测量，使用15 N池稀释和15 N脉冲追逐实验，以定量评估如何微生物氮循环在森林土壤中发生了变化，并将短期N通量转化为长期命运的NH 4+和NO3 -在森林土壤中暴露于慢性N添加。另一个重点将是通过测量异养CO2呼吸对土壤碳循环的N沉降的潜在反馈。在第一阶段，我们的团队与A5合作发现，坦克凤梨是甲烷的重要来源。我们计划进行一系列的测量，以确定这些CH 4排放量的大小从不同的海拔。

Although projections are that N deposition will increase strongly in the tropics, its effects on tropical forests are still largely descriptive. In the proposed project we plan to continue on-going measurements of soil-atmosphere fluxes of N2O, NO, CH4 and CO2 (NUMEX experiment). Our early results suggest that after the first year of flux measurements there are already substantial changes in the microbial processes nitrification and denitrification. Furthermore there are indications that N cycling rates have increased in plots that receive N addition at moderate rates. We plan to conduct measurements using 15N pool dilution and a 15N pulse chase experiment to assess quantitatively how microbial N cycling has changed in forest soils and to translate the short-term N fluxes to long-term fates of NH4 + and NO3 - in forest soils exposed to chronic N addition. Another focus will be potential feedbacks of N deposition on the soil carbon cycling by measuring heterotrophic CO2 respiration. During the first phase, our group discovered in cooperation with A5 that tank bromeliads are a substantial source of Methane. We plan a series of measurement to determine the size of these CH4 emissions from different elevations.