地上凋落物数量变化对长白山阔叶红松林土壤氮循环的影响及其机理

The increase of atmospheric CO2 concentration has been proved to increase aboveground litter in forest ecosystems. How will this change of litter impact soil N cycling and how will the possible change in soil N cycling feedback on the carbon fixation potential of forest ecosystems, are the important questions that need further research in soil biochemistry under global change. This study will focus on the soil under the broad-leaved korean pine mixed forest at Changbai Mountain. After experimental removal and addition of leaf litter inputs, we will monitor the changes in soil temperature, moisture, and pH values and the changes in multiple soil nitrogen pools as well as the net rates of major soil N cycling processes; will combine isotope dilution method and short-term incubation to estimate gross rates of several soil N cycling processes;will use PLFA and qPCR to quantify the community structure of soil microbes and the abundance of N-cycling functional genes, respectively.The impact mechanism of litter inputs on soil N cycle will be further explored in terms of soil micro-climate and soil microbes. This study will be the first attempt in Chinese temperate forests. Out results will help to better build the forest carbon-nitrogen cycling process model and to better forecast the carbon fixation potential of north-east temperate forest ecosystems in the context of increased atmospheric CO2 concentration.

大气CO2浓度的升高增加了森林生态系统地上凋落物的数量。这一变化将如何影响土壤氮循环过程，土壤氮循环可能产生的变化又将对森林生态系统的固碳潜力产生何种反馈，是全球变化背景下土壤生物化学中亟待深入研究的问题。本研究以长白山阔叶红松林土壤为研究对象，进行野外控制实验模拟地上凋落物数量的增加和减少，监测不同凋落物处理下土壤温湿度、pH值、各氮库以及主要氮循环过程的净转化速率，结合 15N同位素稀释法和短期培养实验估算土壤多个氮循环过程的总转化速率，应用磷脂脂肪酸分析技术和qPCR技术量化土壤微生物的群落结构以及与土壤氮循环相关的微生物功能基因的丰度，进而从土壤微环境和土壤微生物的角度探讨地上凋落物数量变化对森林土壤氮循环的影响机理。此类研究在我国温带森林地区从未开展过，研究结果必将为更好地建立森林碳氮循环过程模型、更准确的预测大气CO2浓度升高条件下东北温带森林生态系统的固碳潜力提供有力依据。