水分梯度对春季冻融期湿地土壤氮累积与释放的影响

The nitrogen accumulation and release during the freeze-thaw season are closely related to wetland system functions. The effects of soil moisture on wetland soil nitrogen accumulation and release under freeze-thaw cycles are rarely studied. The project intends to select four natural wetlands with significant soil moisture gradient and adjacent to a ditch at west margin of the smaller Xingkai Lake as research plots. Based on the understanding of the freeze-thaw regime of wetland soils under soil moisture gradient, we will carry out the field and laboratory simulation experiments. By utilizing the natural spacial gradient of soil moisture of the four research plots and adjusting the temporal dynamics of soil moisture to simulate the time gradient of soil moisture, we will study the dissolved nitrogen dynamics and its lateral seepage flux, decomposition rate of litter and nitrongen dynamic and emission flux of N2O under spacial and time gradient of soil moisture during the spring freeze-thaw season. The study will reveal the effects of spacial and time gradient of soil moisture and freeze-thaw cycles on these process and the infulence of soil moisture on the freeze-thaw effects. Through carrying out mesocosm and microcosm simulation experiment, we will study the N2O emission during different periods of freeze-thaw cycles and its response to spacial and time gradient of soil moisture.Finally, we will establish a DNDC model to accurately assess the effects of soil moisture gradient on nitrogen accumulation and releas of wetland soils during the spring freeze-thaw season. The implementation of this project will help further understanding the nitrogen cycling processes of the seasonal permafrost wetland and put forward to the management of Xingkai Lake wetland ecosystem with reference value.

冻融期湿地土壤氮的累积与释放与湿地生态系统功能关系密切，水分条件对冻融作用下湿地土壤氮累积与释放过程的影响研究较薄弱。本项目拟选取兴凯湖小湖西侧4块具有明显水分梯度并且与沟渠相邻的天然湿地作为研究样地。在掌握水分梯度下湿地土壤冻融情势的基础上，开展野外原位实验和室内模拟实验，利用样地间的天然空间水分梯度，并通过调节水分动态模拟时间水分梯度，研究春季冻融期时空水分梯度下湿地土壤溶解性氮动态及侧渗通量、枯落物分解速率和氮动态、N2O排放通量。揭示时空水分梯度和冻融循环对上述过程的影响及水分梯度对冻融效应的影响。通过室内中宇宙和微宇宙模拟实验，研究冻融循环过程不同时段湿地土壤N2O排放特征及其对时空水分梯度的响应。最后，构建DNDC模型，准确评估水分梯度对春季冻融期湿地土壤碳、氮累积与释放的影响。本项目的执行，有助于深入认识季节性冻土区湿地土壤氮循环过程，对兴凯湖湿地生态系统的管理具有参考价值。

冻融期湿地土壤氮的累积与释放与湿地生态系统功能关系密切，水分条件对冻融作用下湿地土壤氮累积与释放过程的影响研究较薄弱。本项目选取兴凯湖湖滨湿地和莫莫格湿地作为研究样地，通过开展野外原位观测，揭示了冻融期湿地土壤温度、水分变化情况，并在此基础上设计和完成了室内模拟实验，利用湿筛法分析了冻融循环对湿地土壤团聚体和湿地土壤有机碳含量的影响，探讨了冻融作用对土壤碳、氮矿化过程的影响。同时利用meta分析法研究了冻结温度、年降水量、pH、土壤 C/N 、N2O等与冻融影响结果的关系，揭示了不同环境下土壤碳氮循环对冻融过程的响应。本项目的执行有助于深入认识季节性冻土区湿地土壤氮循环过程，完善对北方湿地土壤养分循环的认识，对湿地生态系统的管理提供了参考价值。