基于水文过程和冻融循环的高山植被土壤氮动态研究

Nitrogen (N) is the most important nutrient of ecosystem which is a major limiting factor on natural ecosystem productivity. Soil freezing and thawing cycles, a prevalent phenomenon in high altitude region, may alter nitrogen mineralization in soils by changing soil structure and microbial process. Moreover, the hydrochemistry process between soil and runoff interface is influenced by mineral N of soils. However, these processes may be accelerated by global warming. Alpine ecosystems are extremely sensitive to climate change. Surface water quality in the area may deteriorate by releasing abundant NO3- and NH4+ from frozen soil. Thus, we intend to carry out the study at Mt. Wutaishan (altitude: 3061.1m). Three typical alpine vegetation communities are selected: meadow, Larix principis-rupprechtii Mayr and Picea meyeri. The in situ incubation and simulated soil freezing and thawing experiments of undisturbed soil columns are conducted. At the same time, the hydrochemistry processes of rainfall or snowmelt – surface runoff are monitored. All above tasks are designed for finding interaction mechanisms between soil N mineralization and variation of soil structure, soil microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) by quantitive methods in soil freezing and thawing processes. Then these quantitative relationships are introduced into studying the effects of soil freezing and thawing on NO3- and NH4+ concentrations in surface runoff. The results are expected to show mechanisms of N dynamic between soil and runoff interface in seasonal freezing-thawing period. Our study can be considered as a new approach for researching ecohydrology in cryosphere. The construction of water conservation forest in study area is also can be guided by results of this research.

氮(N)是生态系统最重要的养分元素，多数自然生态系统生产力都受N限制。土壤冻融是高海拔区普遍现象，通过改变土壤结构和微生物过程影响土壤N矿化，而土壤矿质N含量又影响着土水界面的水化学过程。气候变暖则可能使这一进程得到加强，尤其是在对气候变化极其敏感的高山区，地表水也许会因为接纳了大量来自冻土的NO3-和NH4+而引发水质恶化。因此，本研究拟在五台山开展(海拔3061.1m)，选择典型高山植被：草甸、华北落叶松和白扦群落，采用原状土柱原位培养和室内模拟冻融相结合的方法，同时进行降水/融雪径流水化学过程监测，定量分析冻融条件下土壤结构和微生物量碳(MBC)、微生物量氮(MBN)的变化及其对土壤N矿化的作用机理，并将它们之间的定量关系引入到土壤冻融对地表径流NO3-和NH4+浓度的影响研究中，揭示季节性冻融期间土水界面N动态机制，为冰冻圈生态水文研究提供新途径，并为该区水源涵养林建设提供依据。

氮(N)是生态系统最重要的养分元素，多数自然生态系统生产力都受N限制。土壤冻融是高海拔区普遍现象，通过改变土壤结构和微生物过程影响土壤N矿化，而土壤矿质N含量又影响着土水界面的水化学过程。气候变暖则可能使这一进程得到加强，尤其是在对气候变化极其敏感的高山区，地表水也许会因为接纳了大量来自冻土的NO3-和NH4+而引发水质恶化。因此，本研究拟在五台山开展(海拔3061.1m)，选择典型高山植被：草甸、华北落叶松和白扦群落，采用原状土柱原位培养和室内模拟冻融相结合的方法，同时进行降水/融雪径流水化学过程监测，定量分析冻融条件下土壤结构和微生物量碳(MBC)、微生物量氮(MBN)的变化及其对土壤N矿化的作用机理，并将它们之间的定量关系引入到土壤冻融对地表径流NO3-和NH4+浓度的影响研究中，结果表明，季节性冻融显著影响了土壤结构和土壤MBC、MBN，它们又显著影响了土壤氮矿化过程，最终影响研究区地表径流的N输出。这一研究结果，为五台山寒区生态水文研究和水源涵养林建设提供了基础数据。