Response of N turnover, DOC production and soil solution fluxes

森林和沼泽土壤经常遭受长期干旱或夏季地下水位下降的影响。土壤中的许多生物和化学过程受到水和氧可用性的影响，但对干旱期增加对这些生态系统年物质通量的影响知之甚少。在这里，我们量化和评估了降水和地下水位的变化对森林和沼泽土壤溶液中物质通量的影响。特别是，我们将重点关注无机氮和溶解有机碳（DOC）通量之外的机制和过程。15N稀释技术和气压过程分离法将用于测定不同操作阶段表层土壤的总氮矿化和总硝化作用。此外，计划在两个地点进行原位净氮矿化，以估计植物吸收无机氮的潜在可用性。在进行实地研究的同时，还将进行一项关于土壤含水量对恒温条件下氮转化影响的实验室研究。利用基于这些组分放射性碳特征的DyDOC模型模拟DOC通量和土壤有机碳周转。

Forest and fen soils are frequently subjected to extended drought periods or to lowering of water table during summer. Many biological and chemical processes in soils are affected by water and oxygen availability, but little is known about the consequences of increasing drought periods on annual matter fluxes for these ecosystems. Here, we quantify and evaluate the effects of changes in precipitation and water table on matter fluxes in soil solution of a forest and a fen at the Fichtelgebirge. Particularly, we will focus on the mechanisms and processes beyond the inorganic N and dissolved organic carbon (DOC) fluxes. The 15N dilution technique and the barometric process separation method will be used to determine the gross N mineralisation and gross nitrification in top soil horizons at different stages of the manipulations. Additionally, in-situ net N mineralisation is scheduled at both sites to estimate the potential availability of inorganic N for plant uptake. The field studies will be accompanied by a laboratory study about the effect of soil water content on N transformation at constant temperature. DOC fluxes and the turnover of soil organic carbon will be simulated using the DyDOC model based on the radiocarbon signature of these fractions.