On the pee! A mechanistic exploration of nitrogen and carbon cycling dynamics in the urine patch.

该项目将实验室和田间试验与数据探索和建模相结合，以提高对控制尿斑内N和C动态的因素的理解。绘制N和C循环过程的动态图牛尿将应用于土壤（旱地和低地）土壤中NO_3、NH_4、DOC、pH和氧化还原浓度的同步变化将通过时间来确定贴片的（中心、中间、外部和"扩散"）区域。pH和O2敏感光电管将用于可视化和量化土壤环境的变化。将在土壤样品上测定N和C酶的微生物基因表达。将尿液成分与N和C循环联系起来尿液将从放牧的低地和高地牧场收集，并在施用于土壤和评估对N和C循环速率和损失的影响之前确定其成分。15 N标记的尿液将用于DENIS土壤培养（North怀克），以确定尿液成分对N2O：N2的影响。将14C标记的嘌呤衍生物，例如马尿酸，以递增的速率施用到土壤中，以确定它们的归宿和对N循环的影响。在山坡不同部分沉积的尿斑中的N和C循环将尿施用到不同的区域（水文学）的一个山坡，以测试的假设，在土壤的化学，物理和生物特性的差异，和气候因素（例如风速-Redeker等人，数据探索和建模学生将探索本项目的新数据是否可以用于改进现有的N和C循环模型，例如DNDC，或者统计建模方法是否可以更好地反映尿斑不同区域内N和C循环的变化。Redeker等人（2015）Biogeosciences 12，7423 - 7434.

The project combines laboratory and field experimentation with data exploration and modelling to improve the understanding of factors controlling N and C dynamics within urine patches.Mapping the dynamics of N and C cycling processes Cattle urine will be applied to soil (upland and lowland) in the laboratory, and simultaneous changes in soil NO3, NH4, DOC, pH and redox concentrations in different (central, middle, outer and 'diffusive') zones of the patch will be determined through time. pH and O2 sensitive optodes will be used to vizualise and quantify changes in the soil environment. Microbial gene expression of N and C enzymes will be determined on soil samples. Linking urine composition with N and C cyclingUrine will be collected from livestock grazing lowland and upland pastures and its composition determined before applying to soil and assessing effects on rates of N and C cycling and losses. 15N labelled urine will be used in a DENIS soil incubation (North Wyke) to determine effects of urine composition on the N2O:N2. 14C labelled purine derivatives, e.g. hippuric acid, will be applied at increasing rates to soil to determine their fate and effect on N cycling.N and C cycling in urine patches deposited in different parts of a hillslope Urine will be applied to different zones (hydrological) of a hillslope to test the hypothesis that differences in the soil's chemical, physical and biological properties, and climatic factors (e.g. wind speed - Redeker et al., 2015) affect N and C cycling and losses from urine patches.Data exploration and modelling The student will explore if new data from this project can be used to improve existing mechanistic N and C cycling models, e.g. DNDC, or if a statistical modelling approach can better reflect the changes in N and C cycling within different zones of the urine patch through time. Redeker et al. (2015) Biogeosciences 12, 7423-7434.